RECYCLING OF SPENT LITHIUM NICKEL-COBALT BATTERIES …
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RECYCLING OF SPENT LITHIUM NICKEL-COBALT BATTERIES THROUGH LEACHING OF NICKEL AND COBALT FROM CATHODE MATERIAL By Kristian Monteiro An honours research thesis submitted to Murdoch University In fulfilment of the requirements for the Degree of Bachelor (Hnrs) in Chemical and Metallurgical Engineering Department of Chemical and Metallurgical Engineering Murdoch University 2018 Supervisor: Dr Aleks Nikoloski
Transcript of RECYCLING OF SPENT LITHIUM NICKEL-COBALT BATTERIES …
RECYCLING OF SPENT LITHIUM NICKEL-COBALT
BATTERIES THROUGH LEACHING OF NICKEL AND
COBALT FROM CATHODE MATERIAL
By
Kristian Monteiro
An honours research thesis submitted to Murdoch University
In fulfilment of the requirements for the Degree of
Bachelor (Hnrs) in Chemical and Metallurgical Engineering
Department of Chemical and Metallurgical Engineering
Murdoch University
2018
Supervisor: Dr Aleks Nikoloski
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Author’s Declaration
I declare that the following work presented is my own, unless otherwise specified, and the
research carried out was under the supervision of Dr Aleks Nikoloski and Dr. Asem Mousa
during the years of 2017-2018. This thesis is submitted as part of the requirements for the
Bachelor (Hnrs) of Chemical and Metallurgical Engineering degree to the school of
Engineering and Information Technology, Murdoch University, Western Australia. This thesis
has not previously been submitted for a degree at any tertiary education institution.
Kristian Monteiro
7th June, 2018
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Abstract
This research paper investigates a hydrometallurgical approach that includes the leaching of
spent lithium-ion battery cathode material. The targeted elements to be recovered are cobalt
and nickel which are identified to be the cost drivers in the lithium-ion battery to date. The
observation of parameters surrounding the leaches give a brief but excellent understanding
into the recovery mechanisms and extraction stages of nickel and cobalt in a sulphuric acid
and hydrogen peroxide medium.
The recycling of lithium ion batteries is trending to become one of the major processes in the
recycling industry heading forward. As more appliances and technologies look to lithium ion
batteries for an energy storage system, it is crucial that the supply is not hindered with the
increase in demand for the battery. The eventual commercialization of a hydrometallurgical
process will most likely be based around the leaching of the spent lithium ion batteries and
the recovery of valuable metals.
Although further test work is necessary to achieve credible and reliable results, this thesis
demonstrates the effect of the change in parameters within the test work which leads to the
recovery of nickel and cobalt from waste lithium ion batteries. 113.2 % cobalt and 98.6 %
nickel were recovered with the leaching of cathode material while 109.6 % cobalt and 100.5
% nickel were extracted with the leaching of separator material. The increased recovery at a
lower cost will generally lead to a commercialised process that will in the future be used to
process all spent lithium- ion batteries.
This thesis looks at the broader scope of the energy storage system market, identifies the cost
driver and looks to decrease that cost driver for a viable and cost effective process.
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Acknowledgements
As I look back on the last four and a half years of this degree, it is staggering to see how much
has changed. It is a reminder of the good people who have made all of this possible.
I firstly would like to thank Dr Aleks Nikoloski for his ongoing support in not only this thesis
but also throughout the degree. Having a supervisor with so much knowledge and willingness
to guide allowed the process of this last step to be relatively smooth. The enthusiasm
expressed in each meeting will not be forgotten, thank you.
I would also like to thank Dr Asem Mousa for his willingness to give up time and valuable
knowledge that helped with the research. Dr Mousa’s extensive knowledge into battery
systems helped me with the initial stages right through to the test work of this thesis.
I would like to thank the tutors and lecturers I have had the privilege of studying under
throughout my time in this degree. Notably associate professor Gamini Senanyake for his
teachings throughout the years.
To my friends who I have met pre-university and friends I have made in university, thank you
for supporting and encouraging throughout these years. Bryce, Mike, Shannon, Lia and Daniel,
thank you for the laughs and hangouts over the last couple of years.
My girlfriend Raquel, thank you for the unwavering support over the last 4 years. Thank you
for your patience and guidance, without you this would not have been possible. Thank you
for your sacrifice at times to put your life on hold for me.
Last but not least to my family. Mum, Dad, Josh, Luke and George, it is not possible to thank
you enough for the support, wisdom and encouragement through some of the hardest times
in my life. I hope that in some way, shape or form I have made you proud.
I could not have asked for better people to be by my side through my university life. For this,
thank you God.
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Contents
Chapter 1 – Introduction ................................................................................................... 1
1.1 Overview ....................................................................................................................................... 1
1.2 Motivation for Study ..................................................................................................................... 2
1.3 Leaching Using Hydrogen Peroxide and Sulfuric Acid................................................................... 3
1.4 Scope and Objectives .................................................................................................................... 4
Chapter 2 – Literature Review ........................................................................................... 5
2.1 Introduction .................................................................................................................................. 5
2.2 Background ................................................................................................................................... 5
2.2.1 Lithium – Ion Batteries ....................................................................................................... 6
2.2.2 Zinc - Bromine Batteries ..................................................................................................... 7
2.2.3 Nickel Metal – Hydride ....................................................................................................... 8
2.2.4 Vanadium Redox Flow ....................................................................................................... 9
2.2.5 Lead – Acid ....................................................................................................................... 10
2.3 Battery Operation and Chemistry ............................................................................................... 11
2.3.1 Lithium – Ion .................................................................................................................... 11
2.3.2 Zinc – Bromine ................................................................................................................. 12
2.3.3 Vanadium Redox Flow ..................................................................................................... 13
2.3.4 Nickel Metal – Hydride ..................................................................................................... 14
2.3.5 Lead – Acid ....................................................................................................................... 15
2.4 Leading Developers ..................................................................................................................... 17
2.5 Battery Materials & Chemicals ................................................................................................... 19
2.5.1 Chemical Compositions and Concentrations ................................................................... 20
2.5.2 Varied Materials ............................................................................................................... 20
2.6 Processing ................................................................................................................................... 23
2.7 Major Ore Deposits and Mineralogy ....................................................................................... 24
2.7.1 Vanadium ......................................................................................................................... 24
2.7.2 Nickel ................................................................................................................................ 25
2.7.3 Lead .................................................................................................................................. 26
2.7.4 Lithium ............................................................................................................................. 26
2.7.5 Zinc ................................................................................................................................... 27
2.7.6 Cobalt ............................................................................................................................... 27
2.7.7 Reserve and Production Summary ................................................................................... 27
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2.8 Processing Options .................................................................................................................. 29
2.8.1 Nickel ................................................................................................................................ 29
2.8.2 Lead .................................................................................................................................. 29
2.8.3 Vanadium ......................................................................................................................... 30
2.8.4 Cobalt ............................................................................................................................... 30
2.8.5 Zinc ................................................................................................................................... 31
2.8.6 Lithium ............................................................................................................................. 31
2.8.7 Processing Summary ........................................................................................................ 31
2.9 Battery Effectivity & Efficiency.................................................................................................... 32
2.9.1 Operational Cell Voltage .................................................................................................. 32
2.9.2 Specific Capacities ............................................................................................................ 33
2.9.3 Recharge Time ................................................................................................................. 34
2.9.4 Operable Temperatures ................................................................................................... 34
2.9.5 Battery/Cycle Life ............................................................................................................. 35
2.9.6 Effectivity and Efficiency Summary .................................................................................. 35
2.10 Cost Comparisons ..................................................................................................................... 36
2.10.1 Lithium Ion Battery ........................................................................................................ 36
2.10.2 Vanadium Redox Flow Battery ....................................................................................... 38
2.11 Critical Cost Drivers ................................................................................................................... 39
2.11.1 Sensitivity Analysis ............................................................................................................. 40
2.12 Summary ................................................................................................................................... 41
Chapter 3 – Experimental Methods ................................................................................. 43
3.1 Introduction ................................................................................................................................ 43
3.2 Sample Source, Reagents and Equipment .................................................................................. 43
3.2.1 Lithium ion batteries ............................................................................................................ 43
3.2.2 Acids ..................................................................................................................................... 45
3.2.3 Catalyst ................................................................................................................................. 45
3.2.4 Equipment ............................................................................................................................ 46
3.3 Method ....................................................................................................................................... 47
3.3.1 Battery Discharge ................................................................................................................. 47
3.3.2 Battery Deconstruction ........................................................................................................ 48
3.3.3 Material Cleaning ................................................................................................................. 50
3.3.4 Small-Scale Leaches ............................................................................................................. 51
3.3.5 AAS & ICP-MS Analysis ......................................................................................................... 54
Chapter 4 - Cathode Characterisation ............................................................................. 56
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4.1 External Cathode Characterisation Assays ................................................................................. 56
Chapter 5 - Leach Results ................................................................................................ 58
5.1 Time Variable Results .................................................................................................................. 58
5.1.1 Change of pH on Time Leach ............................................................................................... 60
5.2 Temperature Variable Results .................................................................................................... 62
5.2.1 Change of pH on Temperature Leach .................................................................................. 63
5.3 Acid Concentration Variable Results ........................................................................................... 64
5.3.1 Change of pH on Acid Leach ................................................................................................ 65
5.4 Hydrogen Peroxide Concentration Variable Results ................................................................... 66
5.4.1 Change of pH on Peroxide Leach ......................................................................................... 68
5.5 Leach Optimization ..................................................................................................................... 69
Chapter 6 – Conclusions and Recommendations ............................................................. 72
6.1.1 Conclusions .............................................................................................................................. 72
6.1.2 Recommendations ................................................................................................................... 73
Chapter 7 - References ................................................................................................... 76
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Tables, Equations and Figures
Table 2.2. 1: Cathodic and anodic reactions of the most promising battery systems .............. 9
Table 2.3. 1: Positive electrode materials with given capacities (Linden 2002) ...................... 11
Table 2.3. 2: Conductivity in mS/cm for 1 M of LiFP6 in different solvents (Linden 2002) ..... 12
Table 2.3. 3: Molecular weight and solubility data of the electrolytes (Zabavchik n.d.) ........ 12
Table 2.3. 4: Properties of sulphuric Acid Solutions and change in Ah (Linden 2002). ........... 16
Table 2.5. 1: Materials for anodes, cathodes and electrolytes for the investigated battery
systems (Linden 2002). ............................................................................................................ 19
Table 2.5. 2: Sodium alanates used as metal-hydride cathodic materials (Sakintuna 2006). . 22
Table 2.7. 1: Elemental reserves and production for 2016 (USGS 2016). ............................... 24
Table 2.9. 1: Characteristics of each battery system compared to each other (Linden 2002).
.................................................................................................................................................. 32
Table 2.10. 1: Cost breakdown of lithium ion battery (cobalt cathode) (Novo 2016). ........... 37
Table 2.10. 2: Cost Breakdown of the vanadium redox flow battery (VRFB) (Moore 2013)... 38
Table 3.2. 1: Battery weight breakdown for a lithium ion battery .......................................... 45
Table 3.3. 1: Mass Percentage for components of batteries .................................................. 51
Table 3.3. 2: Variable Time Leach Variables ............................................................................ 51
Table 3.3. 3: Variable Temperature Leach Variables ............................................................... 51
Table 3.3. 4: Variable Acid Concentration Leach Variables ..................................................... 52
Table 3.3. 5: Variable H2O2 Concentration Leach Variables ................................................... 52
Table 3.3. 6: Optimisation Leach Variables.............................................................................. 52
Table 4.1. 1: Cathode, Anode and Separator characterisations via ICP-MS in standard ppm
concentrations ......................................................................................................................... 56
Table 5.5. 1: Optimisation parameters for both cathode and separator material.................. 69
Table 5.5. 2: Cobalt and nickel recoveries in both cathode and separator materials. ............ 70
[1] Leaching Rate Equation……………………..………………………………………………………………………… 46
[2] Chemical Reaction For Hydrogen Peroxide…………………………………….……………………….…….46
[3] pH Equation…………………………………………………………………………………………………………………..61
[4] Arrhenius Equation ……………………………………………………………………………………………………….62
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Figure 1. 1.1: Rechargeable battery powered car sourced by Wikimedia Commons ............... 1
Figure 2.2. 1: Operation of the lithium-ion cell showing charge and discharge adapted from
Roy Poulomi 2015 ...................................................................................................................... 6
Figure 2.2. 2: The operation of the zinc-bromine cell showing charge and discharge adapted
from BSEF 2017 .......................................................................................................................... 7
Figure 2.2. 3: Operation of nickel metal-hydride cells showing charge/discharge adapted
from Kawasaki 2017 ................................................................................................................... 8
Figure 2.2. 4: Operation of the lead-acid cell showing charge and discharge adapted from
Kuphaldt 2010 .......................................................................................................................... 10
Figure 2.3. 1: The vanadium redox flow battery operation adapted from Australian
Vanadium Limited 2017 ........................................................................................................... 14
Figure 2.3. 2: Alkaline electrolyte (NaOH and KOH) conductivities adapted by Rand 2011 ... 15
Figure 2.3. 3: Cell voltage and rated capacity data in the lead-acid battery adapted by
Vincent 1984 ............................................................................................................................ 16
Figure 2.7. 1: World selected element reserves as of 2016. ................................................... 25
Figure 2.7. 2: World elemental production of each investigated element in 2016. ............... 26
Figure 2.7. 3: Major lithium processing operations adapted from British Geological Surveys
2008 ......................................................................................................................................... 28
Figure 2.8. 1: Sphalerite mineral containing zinc sourced by Wikimedia Commons .............. 30
Figure 2.9. 1: Sumitomo’s redox flow battery shown as a grid scale adapted from Sumitomo
Electric 2017 ............................................................................................................................. 33
Figure 2.9. 2: Projected installed capacity for three different batteries adapted from MSE
Supplies 2015 ........................................................................................................................... 34
Figure 2.10. 1: Lithium ion battery cost breakdown into cathodic elements adapted from
Berger 2012 .............................................................................................................................. 36
Figure 2.10. 2:Capital cost fractions pie chart showing distribution of costings for lithium ion.
.................................................................................................................................................. 37
Figure 2.10. 3: Capital cost fractions pie chart showing distribution of costings for VRFB. .... 38
Figure 2.11. 1: Sensitivity web diagram for the fluctuation of each vanadium battery
component ............................................................................................................................... 40
Figure 2.11. 2: Sensitivity web diagram for the fluctuation of each lithium-ion battery
component ............................................................................................................................... 41
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Figure 3.2. 1: Lithium ion battery breakdown (Physics Central 2017) .................................... 44
Figure 3.3. 1: Discharging mechanism for battery ................................................................... 47
Figure 3.3. 2: 18650 lithium ion battery outer-shell components .......................................... 48
Figure 3.3. 3: Inner-battery components ................................................................................. 49
Figure 3.3. 4: Separated components showing cathode, separator and anode material
respectively .............................................................................................................................. 49
Figure 3.3. 5: Aluminium foil with attached cobalt and nickel material ................................. 50
Figure 3.3. 6: Event tree showing the method for leaching of spent lithium ion battery
cathode material ...................................................................................................................... 53
Figure 3.3. 7: Nickel standard curve 1 showing error and equation ....................................... 54
Figure 3.3. 8: Cobalt standard curve 1 showing error and equation ....................................... 54
Figure 3.3. 9: Nickel standard curve 2 showing error and equation ....................................... 55
Figure 3.3. 10: Cobalt standard curve 2 showing error and equation ..................................... 55
Figure 5.1. 1: Pink leach liquor with 40-minute time leach ..................................................... 58
Figure 5.1. 2: Time vs Co & Ni Extraction ................................................................................. 59
Figure 5.1. 3: pH variation of solution during precipitation (Sohn 2006) ................................ 60
Figure 5.1. 4: Time vs Delta pH ................................................................................................ 61
Figure 5.2. 1: Leach temperature vs leach liquor concentration of nickel and cobalt ............ 62
Figure 5.2. 2: Temperature vs Delta pH ................................................................................... 63
Figure 5.3. 1: H2SO4 Concentration Vs Leach Liquor concentration of nickel and cobalt ...... 64
Figure 5.3. 2: H2SO4 Concentration Vs Leach Liquor concentration of various elements (Nayl
2017). ....................................................................................................................................... 65
Figure 5.3. 3: H2SO4 concentration Vs Delta pH ..................................................................... 65
Figure 5.4. 1: Hydrogen Peroxide addition % (H2O2) Vs cobalt and nickel concentration in
leach liquor .............................................................................................................................. 66
Figure 5.4. 2: Hydrogen Peroxide Addition Vs Leaching Percentage of various elements (Nayl
2017) ........................................................................................................................................ 67
Figure 5.4. 3: H2O2 % Vs Delta pH ............................................................................................ 68
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Chapter 1 – Introduction
1.1 Overview
As the demand for advances in technology presents itself, supply is critical in sustaining this
advancement. Renewable energy is crucial to sustain modern day technology as shown by
multiple upcoming innovative products. The electric car is most likely to be the biggest ‘new’
technology which is made possible through the use of rechargeable batteries and renewable
energy. These rechargeable batteries now power a lot of modern day technology such as
mobile phones and portable computers. As population increases at a rapid rate, the demand
for this technology is also increasing at a rapid rate suggesting a shortage of rechargeable
batteries may be a factor into stopping civilization in progressing.
The objective of this research was to reduce the costing of a significant battery by the method
of cost driver identification and process optimization. By reducing the cost of processing of
energy storage components, the particular battery system has a higher chance of being
sustainable for the future and may even prove some batteries to be valid for particular uses
in technology.
Figure 1. 1.1: Rechargeable battery powered car sourced by Wikimedia Commons 2018
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Finding a more efficient technique of processing may reduce tailings hence increasing
production, increase production through a faster processing method or reducing cost of the
processing through a cheaper and more affordable process. The minimization of any of these
factors may lead to the commercialization of a battery or make it more viable and sustainable.
Once a cost driver is determined for the most applicable energy storage system, test work can
begin into the minimizing in cost of that component which would ideally lead to advances in
the battery production.
In this research project, it was found that the cathode component in the Lithium ion battery
was the cost driver. A total of 27 % of the total battery cost was accountable to the cathode
consisting of mainly nickel and cobalt. As this was the largest component by percent within
the battery systems studied and also the battery that is ideal in most rechargeable battery
applications, it was chosen to be researched. The vanadium battery also had a large cost
driver being the vanadium electrolyte, this battery however is still in relative early
development in terms of processing and is not as widely used as the lithium ion battery.
1.2 Motivation for Study
As the lithium ion battery was predicted to have the biggest impact on the energy storage
system market, decreasing the cost driver was the selected point of research. A similar
process has already been conducted in 2017 by Nayl et al. It was interesting to see a recycling
process used to decrease the major cost driver in the lithium ion battery. Using spent lithium
ion batteries seemed quite relevant as the demand for lithium ion batteries is increasing and
the spent cathode is still relatively unchanged after discharge.
As the lithium electrolyte decreases in capacity and electrical conductivity characteristics over
its long life, the important matter was the cathode. If the cathode can be recovered, the
costliest part of the battery may be recycled. Nayl et al (2017) used a leaching process with
hydrogen peroxide and sulfuric acid which seemed relevant to the metallurgy and process
side of the production or recycling of lithium ion batteries.
A similar process of recycling is the intention for the test work however using conditions that
will prove even less costly may be the difference between a useable and non-useable process.
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1.3 Leaching Using Hydrogen Peroxide and Sulfuric Acid
A cheap yet effective type of acid needs to be used to recover the cobalt and nickel into
solution. It is important that the conditions in the leach are relatively cost effective to make
the process successful and relevant. Using an inorganic acid is usually cheaper and can prove
to be very effective in recovery of metals (Yan, 2014). Although the inorganic acid may achieve
less recovery, it could be the difference between a successful or non-successful recycling
process due to its low cost.
High recoveries of cobalt and nickel were recorded by Nayl et al (2017). Using the process of
a hydrogen peroxide and sulfuric acid leach, up to 97% recovery was achieved. This high
recovery shows that the process is effective however if conditions can be tweaked to achieve
similar recoveries at a lower cost, it may make it a viable process.
Using hydrometallurgy processes to recycle battery materials is not a new idea and has
already been used in nickel metal hydride battery recycling (Holmberg, 2017). Using a similar
process for lithium ion batteries is the next step to decrease overall costings for the battery
which proves to be a large factor in modern day technology.
Decreasing the demand for primary cobalt and nickel deposits and stockpiles, the cobalt and
nickel used in lithium ion batteries can be recycled which makes it a much more sustainable
and cheap energy storage system.
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1.4 Scope and Objectives
The recovery of cobalt and nickel from a spent lithium ion battery’s cathode material in a cost
effective process in turn decreasing overall production cost of the lithium ion battery is the
sole aim of this report. Having this clear scope in mind, setting out basic objectives is a good
method to achieve success. These objectives include the following process variables;
• Altering hydrogen peroxide concentration to achieve the best recovery to cost ratio
• Finding optimal time for leach to achieve maximum recovery
• Finding optimal temperature for maximum recovery
• Finding optimal sulfuric acid concentration to achieve the highest recovery
• Combining all optimal variables to achieve the highest recovery possible in a sulfuric
acid - hydrogen peroxide leach
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Chapter 2 – Literature Review
2.1 Introduction
Identifying cost drivers associated with different batteries allows for advances in the
reduction of production costs for relevant energy storage systems. Chapter 2 studies the
exploration of the largest cost driver in the given batteries investigated to find the biggest
influence on the market. The literature review will be the guideline for the test work needed
to locate and reduce the largest cost driver. A process of elimination technique not only
identifies cost driver objectives but also ore reserves and battery relevance in terms of
efficiency in today’s context. By completing this compact study and investigating each energy
storage system individually, comparisons can be made to further the research in a positive
and useful direction.
It was critical that the energy storage systems explored needed to be broad and an open
minded study was undertaken. The batteries and their given uses proved it to be a difficult
selection process therefore all systems needed to be characterized in topics to identify the
most relevant battery to be further researched.
2.2 Background
Some batteries that will be studied include lithium-ion, zinc- bromine, nickel metal hydride,
lead-acid and also the vanadium redox flow battery. These batteries have been developed to
be the most practical, efficient and cost effective for modern day applications. Development
of these batteries have included substitution and alteration of given materials, chemicals and
conditions. The batteries investigated have been chosen due to their market demand for
energy storage considering integration of wind and solar energy (ESA, 2015).
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2.2.1 Lithium – Ion Batteries
Lithium-ion batteries are one of the latest batteries to take over the market and be used in a
wide range of applications. Sony Energytec Incorporated developed the battery in 1991 after
findings from John Goodenough at Oxford University suggested that lithium-cobalt oxides and
lithium-nickel oxides could create rechargeable batteries (Brodd, 2012). Rechargeable
batteries and electric car batteries are two of the main applications that lithium is processed
for, taking over conventional lead-acid batteries (Hecimovich, 2015).
As lithium-ion batteries continue to grow in market value and usage around the world, one
of the main questions that need to be asked is; how long will the lithium reserves last?
Stanford University suggested that if all cars were to be replaced with electric engines using
the lithium ion rechargeable battery, 82 % of the world’s lithium reserves (economically viable
to process) would be ‘consumed’ (Eason, 2010). This suggests that lithium reserves may be
sustainable now however may not be with an increased process rate, this is shown in table
2.7.1. With this figure not accounting for population increase, lithium shows to be a short
term solution. This underlying problem shows that lithium will not be able to keep up with
the world’s supply and demand and therefore alternative energy storage systems should be
investigated. Although lithium production won’t be able to sustain human needs after a
period of time, the lithium- ion battery may be the bridging between current or previous
technologies to future technologies that are more sustainable and viable in the long term.
Figure 2.2. 1: Operation of the lithium-ion cell showing charge and discharge adapted from Roy Poulomi (2015)
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2.2.2 Zinc - Bromine Batteries
Zinc-bromine batteries are energy storage systems that utilize a redox flow technique that
allows for plating of zinc onto anode plates. The zinc – bromine batteries were patented in
the late 1800’s but not thoroughly researched until the 1970’s by Exxon. The reason for this
was due to the highly volatile chemical nature of bromine that was not suitable for battery
systems as it posed as a severe risk and also due to its high discharge rate. It was not until the
70’s that a new electrolyte was considered (being zinc-bromide). The zinc-bromine battery
was effective with the use of the zinc-bromide electrolyte as the regeneration of zinc-bromide
could occur through reactions with the introduction of a charge (Rand, 2001). The zinc-
bromine flow battery is effective in that it can discharge large amounts of energy and also can
be scaled up depending on its application relatively easily, however its downfall is the toxicity
of the zinc bromide electrolyte and its high costing of materials (ESA, 2017). Figure 2.2.2
shows the operation and reactions occurring in a zinc-bromine battery.
Figure 2.2. 2: The operation of the zinc-bromine cell showing charge and discharge adapted from BSEF (2017)
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2.2.3 Nickel Metal – Hydride
Nickel metal-hydride batteries are another energy storage system that have been used
extensively in the last 50 years. As a replacement for nickel-cadmium batteries, nickel metal-
hydride batteries use a similar battery mechanism to NiCd however they don’t contain the
toxic element of cadmium. Toxicity of cadmium was not the only disadvantage of the nickel-
cadmium battery, the discharge rate was much too high for consumer use and interest which
urged developers to invent an alternative battery with longer shelf life, hence the invention
of the NIMH battery (Rosch, 2001). Stanford Ovshinsky was the inventor of the NiMH battery
in 1992 (Lambert, 2016). The battery technology incorporates hydrogen stored in the alloys
which can act as a cathode. This change with the energy storage system increased the shelf
life for the battery which aided in the eventual commercialization. Although the shelf life of
the battery increases, compared to other batteries, nickel metal-hydride cell systems still are
at a disadvantage with service life when deep discharge occurs. This is one of the main
problems of the nickel metal-hydride battery and is crucial to the battery operation as
consumers want batteries with longevity (Green Ion, 2016). This battery configuration is now
used in car batteries and also many portable devices such as phones, PC’s and televisions.
Figure 2.2. 3: Operation of nickel metal-hydride cells showing charge/discharge adapted from Kawasaki (2017)
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2.2.4 Vanadium Redox Flow
Vanadium redox flow batteries (VRB) are one of the newer batteries that show extremely high
potential to become commercialized worldwide. The battery runs off of a vanadium
electrolyte which has the ability to move charges without a change in capacity which means
a high battery life is able to be achieved (Energy Storage Association, n.d.). Maria Skyllas-
Kazacos and co-workers invented the vanadium battery at The University of New South Wales
in 1985 (UNSW, n.d.). Some of the main advantages of the battery include its long battery life
(longer than most current batteries) and its ability to power large scale grids by a high energy
efficiency (Wang, 2012). The downfall for vanadium currently is the costing of vanadium
electrolyte as the processing is quite complex. Although the vanadium battery is not used
world-wide currently, an in depth analysis can be carried out to find the cost driver of this
developing battery and in time aid in the commercialisation of this exciting and innovative
technology.
Table 2.2. 1: Cathodic and anodic reactions of the most promising battery systems
Battery System
Anode (Anolyte) Reaction + Potential
Cathode (Catholyte) Reaction + Potential
References
Lithium – Ion
(Cobalt)
Li0.55CoO2 + 0.45Li+ + 0.45e- ⇋ LiCoO2
E° = +1.00
LixC6 ⇋ 6C + xLi+ + xe-
E° = -3.00
(S.-C. S. Wang 2011)
Lithium – Ion
(Nickel)
Li0.35NiO2 + 0.5Li+ + 0.5e- ⇋ Li0.85NiO2
E° = +0.70
LixC6 ⇋ 6C + xLi+ + xe-
E° = -3.00
(S.-C. S. Wang 2011)
Vanadium
Redox-Flow
VO2++e-+2H+ ⇋ V3+ + H2O, E° = +0.34
VO2++2H++e- ⇋ VO2+ + H2O, E° = +1.00
V2+ + 2e- ⇋ V, E° = -1.13
V3+ + e- ⇋ V2+, E° = -0.26
(Skyllas-Kazacos 2012)
Zinc-Bromine Br2 + 2e- ⇋ 2Br-
E° = +1.065 *
Zn ⇋ Zn2+ + 2e-
E° = -0.76 *
(Rajarathnam 2016)
Nickel metal-
hydride
NiOOH + H2O + e- ⇋ Ni(OH)2 + OH-
E° = +0.83
MHx + OH- ⇋ MHx-1 + H2O + e-
E° = -0.52
(Power Stream 2017)
Lead - Acid PbO2 + HSO4- + 3H+ + e- → PbSO4 + 2H2O
E° = +1.685
Pb + HSO4- → PbSO4 + H+ + 2e-
E° = -0.356
(Engineers Edge 2017)
* = Potentials taken from potassium hydroxide electrolyte and nickel oxyhydroxide cathode
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2.2.5 Lead – Acid
Lead-acid batteries are unarguably one of the most used rechargeable energy storage systems
used in the last century. These batteries use the reaction of lead (II) sulphate and sulphuric
acid to store the energy in the electrodes as electrons are transferred between the cells. The
commercialization and eventual success of the battery was due to its robustness, cheap cost
and reliability of the energy storage system (Electropaedia, 2017). Gaston Planté was the
French physicist who invented the lead-acid battery in 1859 before being tweaked to be the
popular battery that it is today (Vincent, 1984). One of the main factors that make the lead-
acid battery appealing to the motor industry is the power to weight ratio. The large supply
currents within the relatively small battery makes it favourable with cars and automotive
vehicles along with its low cost (Evolving Energy, n.d.). Some disadvantages and problems for
the lead acid battery include its weight and size (although robust, can be quite bulky), it has
the ability to overheat during charging and also for a battery in the 21st century has a relatively
small service life of around 400-500 cycles (Linden, 2002). Main applications of the lead acid
battery include automotive, lighting, high current drainage applications and also backup
energy storage (Sunlight, 2012).
Figure 2.2. 4: Operation of the lead-acid cell showing charge and discharge adapted from Kuphaldt (2010)
11 | P a g e
2.3 Battery Operation and Chemistry
2.3.1 Lithium – Ion
Lithium-ion batteries operate with three main components, a positive and negative electrode
with a lithium electrolyte. The positive electrode is made of an aluminium foil that is usually
coated with either LiCoO2 or LiNiO2. Many different electrode compounds have been used
however the LiCoO2 and LiNiO2 compounds have proven to be the most effective. Table 2.3.1
shows the specific capacity of the different positive electrode materials. Only the LiCoO2 or
LiNiO2 electrode compounds will be investigated to find cost drivers as they are most widely
used in the market. Initially, the lithium-nickel positive electrode was the preferred material
due to its low toxicity however was found to be too reactive with the electrolyte. This high
reactivity caused safety hazards and also reduced the battery life after multiple cycles (Brodd,
2012). The negative electrode is usually a copper foil that is coated with powdered graphite
or carbon. Between the two electrodes is a membrane film that acts as a separator between
the two electrodes that is usually super saturated with the electrolyte salt (LiPF6). Table 2.3.2
shows the effect of solvent used and how the temperature affects conductivity. As the cell
runs, the electrodes attract or repel the charged lithium ion which results in the build-up of
charge as electrons transfer. The movement of lithium ion across the cells to one electrode
or another determines the charging or discharging of the battery and hence the reason why
it is called the lithium-ion battery. As shown in Table 2.3.3 one problem associated with the
lithium-ion battery is the solubility of the LiPF6 as it is quite low at around 1 g/L in water at
standard temperatures. The three materials used in the lithium-ion battery need to be studied
to find the cost driver within the useful battery storage system (Brodd, 2012).
Table 2.3. 1: Positive electrode materials with given capacities (Linden 2002)
Material Specific Capacity (mAh/g) Advantages and Disadvantages
LiCoO2 155 Most Common Commercially
LiNi0.7Co0.3O2 190 Intermediate Cost
LiNi0.8Co0.2O2 205 Intermediate Cost
LiNi0.9Co0.1O2 220 Highest Specific Capacity
LiNiO2 200 Most Exothermic Decomposition
LiMn2O4 120 Least Exothermic Decomposition
12 | P a g e
Table 2.3. 2: Conductivity in mS/cm for 1 M of LiFP6 in different solvents (Linden 2002)
Solvent -40 C -20 C 0 C 20 C 40 C 60 C 80 C
diethyl carbonate - 1.4 2.1 2.9 3.6 4.3 4.9
ethyl methyl carbonate 1.1 2.2 3.2 4.3 5.2 6.2 7.1
propylene carbonate 0.2 1.1 2.8 5.2 8.4 12.2 16.3
dimethyl carbonate - 1.4 4.7 6.5 7.9 9.1 10
ethylene carbonate - - - 6.9 10.6 15.5 20.6
methyl acetate 8.3 12 14.9 17.1 18.7 20 -
methyl formate 15.8 20.8 25 28.3 - - -
Table 2.3. 3: Molecular weight and solubility data of the electrolytes (Zabavchik n.d.)
Electrolyte Molecular Weight (g/mol) Solubility in Water (25° C)
V2O5 181.9 Low Solubility
LiPF6 151.9 Low Solubility
H2SO4 98.07 Soluble
ZnBr2 225.19 Soluble
NaOH 39.99 Soluble
KOH 56.11 Soluble
Soluble – More than 1 g/ 100 g of water
Low Solubility – 0.01 to 0.1 grams per 100 grams of water
2.3.2 Zinc – Bromine
The zinc – bromine battery operates by the flow of electrolyte through a cell stack. The
electrolyte that consists of the zinc – bromide which is dissolved in salt water passes through
the cell stack from one tank where zinc is plated onto the cathode and the bromine is oxidised
at the anode. This solution is then transferred into the opposite tank where it is stored until
a recharge occurs. The reaction of zinc plating occurs on the negative electrode where the
zinc ions attaches onto carbon-plastic electrodes. The charging occurs when bromine solution
is loaded by dissolved zinc ions from the plate. The amount of electrodes can be increased to
increase the cell stack size. Increasing the cell stack size by simply increasing the carbon-
plastic electrode count suggests that the battery size is determined by the amount of
13 | P a g e
electrolyte in the tanks and also the electrode sizes, making the battery a viable energy
storage solution (Rand, 2001).
2.3.3 Vanadium Redox Flow
The vanadium redox flow battery essentially also has four main sections. The catholyte,
anolyte, membrane filter and electrodes are all the essential key aspects that make up the
vanadium flow battery. The battery works by the movement of electrolyte from one cell to
another. The distinctive characteristic that vanadium contains is that it has the ability to gain
and lose charges (electrons) without a lasting effect on the electrolyte solution. Compared to
lead acid and lithium-ion, the vanadium battery therefore has an ‘infinite’ time life if the
vanadium electrolyte is being inspected (Kim, 2015). In the catholyte, VO2+ is oxidised to VO2+
where V3+ is reduced to V2+ in the anolyte for the charging of the battery. The opposite occurs
for the discharge of the battery and this is why the redox reaction is so important in this cell.
The membrane that divides the catholyte and anolyte is primarily to stop the mixing of
electrolyte as they will have different charges and vanadium ions. As the mechanism is similar
to lithium-ion batteries, it is important to note the key differences in that the vanadium redox
flow battery runs off of a much simpler mechanism and reaction that has an increased
electrolyte life. The electrolyte however does have a problem with solubility. It is found that
V2O5 has a low solubility of around 1 g/L of water which poses to be a problem to be dissolved
in water or sulphuric acid. Further refining of V2O5 to V2O4 gives better solubility allowing for
increased electrolyte performance however, cost is a factor. Finding the cost drivers of the
vanadium redox flow battery would help in the commercialization of the battery and reduce
cost factors that may pose an issue (Rand, 2001). Figure 2.3.1 shows a component breakdown
of the vanadium flow battery clearly showing the main sections with reactions.
14 | P a g e
Figure 2.3. 1: The vanadium redox flow battery operation adapted from Australian Vanadium Limited (2017)
2.3.4 Nickel Metal – Hydride
The nickel metal-hydride battery uses a similar energy transfer mechanism to the lead acid
battery. The ‘hydrogen’ component is in the form of the metal hydride at the negative
electrode. Nickel oxide is the material used at the positive electrode with an alkaline
electrolyte used to transfer the charge. The alkaline electrolyte is usually a potassium
hydroxide or sodium hydroxide. Both electrolytes are shown to be effective however
potassium hydroxide proves to have a better conduction. Figure 2.3.2 shows the conductivity
effected by concentration of electrolyte. The alkaline electrolyte reacts with the metal-
hydride electrode and discharges electrons with the production of water at the negative
electrode. The positive electrode reacts with the H2O molecules which allow for the
‘reduction’ stage. These reactions are also reversible so charging the battery can be done by
the reverse reactions. This two stage process at the positive and negative electrodes allows
the battery to have multiple advantages over other batteries such as a high storage capacity
and low battery costs (Rand, 2001).
15 | P a g e
Figure 2.3. 2: Alkaline electrolyte (NaOH and KOH) conductivities adapted by Rand (2011)
2.3.5 Lead – Acid
The lead-acid battery is similar to the lithium-ion battery in that is contains two electrodes
and a solution. The positive electrode is a lead dioxide (PbO2) material while the negative
electrode is of a lead sponge material. Both of these electrodes are submerged in diluted
sulphuric acid that plays a similar role which is to transfer electrons from the negative
electrode to the positive electrode however, the sulphuric acid also takes part in the reaction
between the electrodes and is not merely a form of transport for the ions in solution. As the
cell discharges, the sulphuric acid is converted to water which means for good indication of
battery charge. Figure 2.3.3 shows the indication of capacity and voltage constraints as
sulphuric acid is depleted (decrease in density). The charging mechanism from the lead-acid
battery occurs when the lead sulphate (PbSO4) reacts with the lead electrodes to form
sulphuric acid under reverse current. The lead sulphate is reconverted at the appropriate
electrodes and hence is why the charging is possible in the lead-acid battery (Vincent, 1984).
Table 2.3.4 shows the effect on sulphuric acid concentration in water and how the
electrochemistry is affected. Even though this battery storage system has been used
industrially for a lengthy amount of time, it is still important to understand the mechanisms
of the battery and find cost drivers that may have not been found before.
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0 2 4 6 8 10
Co
nd
uct
ance
/ S
cm
-1
Concentration / mol l-1
NaOH
KOH
16 | P a g e
Figure 2.3. 3: Cell voltage and rated capacity data in the lead-acid battery adapted by Vincent (1984)
Table 2.3. 4: Properties of sulphuric Acid Solutions and change in Ah (Linden 2002).
Specific Gravity H2SO4 Electrochemical Equivalent Ah At 15° C At 25° C Wt % Vol % mol/L
1 1 0 0 0 0
1.05 1.049 7.3 4.2 0.82 22
1.1 1.097 14.3 8.5 1.65 44
1.15 1.146 20.9 13 2.51 67
1.2 1.196 27.2 17.7 3.39 90
1.25 1.245 33.2 22.6 4.31 115
1.3 1.295 39.1 27.6 5.26 141
1.35 1.345 44.7 32.8 6.23 167
1.4 1.395 50 38 7.21 -
1.45 1.445 55 43.3 8.2 -
1.5 1.495 59.7 48.7 9.2 -
1
1.1
1.2
1.3
1.4
1.9
2
2.1
2.2
0 20 40 60 80 100
Elec
tro
lyte
Den
sity
(kg
/d
m3 )
Op
en C
ircu
it C
ell V
olt
age
(V)
Percentage of Rated Capacity
17 | P a g e
2.4 Leading Developers
It is important to recognise the companies that are focused on creating new energy storage
systems and also the companies that are innovating current batteries. These companies are
usually large users of the given battery and therefore make it a priority to innovate current
energy storage systems to gain profit and improve technological potential.
• As lithium – ion batteries are the most popular trend in battery systems, Tesla has
been a leading developer of recent as it uses the rechargeable battery in electric
vehicles. Some other leading developers of the lithium ion battery include AESC, Alevo
(who developed the first inorganic lithium battery), Amprius and Electrovaya (Shahan
2015). LG Chem is also another company that is focused on creating lithium ion hybrid
batteries. Producing lithium-ion polymer batteries capable of grid scale and electric
vehicle application, the company aims to improve battery capacity and efficiency
through change in components (LG Chem, 2017).
• Imergy is one of the leading developers for the vanadium redox flow battery as the
company aims to find more effective stationary energy storage systems. The company
has already implemented the redox flow batteries in several countries including
Australia (Bridges, 2016). Sumitomo is a Japanese company who have also
implemented a major redox flow battery in Japan. Small towns in Japan are being
powered by the battery systems and has proven to be an effective investment (Stone,
2014). Maria Skyllas - Kazacos although inventing the battery system has continued
researching on the battery and proves to be one of the leading researches into the
reduction of cost and improving efficiency.
18 | P a g e
• Primus Power have developed a zinc - bromine battery that is capable of large grid
scale deployment and use. It utilizes a stronger membrane filter as well as a single
tank. The grid-scale batteries are being deployed in multiple countries and is
appealing to consumers due to its ‘endless’ battery life similar to the vanadium redox
flow (Primus Power, 2017). Redflow is also a company that is promoting growth as
the zinc- bromine energy storage producers have supplied to over 100 projects
worldwide (Stone, 2014). The company is currently implementing the zinc-bromine
battery into telecommunications, grid scale, commercial and residential applications.
(RedFlow, 2017).
• Ecoult which is a lead-acid battery developing company from Australia have been
granted funding to aid in the developing of the lead-acid battery in India with a sole
focus on decreasing costings for the widely used energy storage system. It is
important to notice that batteries are still being investigated and developed to cut
costings or increase battery efficiency after a long period of time (Financial Review,
2017).
19 | P a g e
2.5 Battery Materials & Chemicals
As observing multiple energy storage systems can be quite complex, it is useful to form a
material matrix that can be used to examine the various materials in each battery which will
help in the costing analysis. Finding the cost driver is the objective to achieve the aim of
finding a method to reduce the costing of a particular battery. As the battery systems include
multiple components, the material matrix can be broken down into cathodes, anodes and
electrolytes. As the batteries being investigated nearly all contain these components, it can
be a crucial piece of data that helps in finding the cost driver. The cost drivers of each battery
system are usually related to the cathodes, anodes or electrolytes.
Table 2.5. 1: Materials for anodes, cathodes and electrolytes for the investigated battery systems (Linden 2002).
Battery System Material
Anode
(Anolyte)
Cathode
(Catholyte)
Electrolyte
Lithium – Ion
(Nickel Complex)
Lithium Nickel – Oxide Carbon Graphite Lithium Hexafluorophosphate
(LiPF6)
Lithium – Ion
(Cobalt Complex)
Lithium Cobalt - Oxide Carbon Graphite Lithium Hexafluorophosphate
(LiPF6)
Vanadium Redox
Flow
Carbon Graphite
Carbon Graphite
Vanadium (V) Oxide (V2O5)
Nickel Metal -
Hydride
Nickel (II) Oxide
Metal-Hydride
Potassium Hydroxide OR
Sodium Hydroxide (NaOH)
Zinc Bromine Bi-polar Carbon
Plastic Electrode
Bi-polar Carbon Plastic
Electrode
Zinc Bromide (ZnBr2)
Lead - Acid Lead Dioxide
Lead Sponge Sulfuric Acid (H2SO4)
20 | P a g e
Although there are various materials that can be substituted for each major component of
the investigated batteries, these materials and chemicals are the most commonly used. Table
2.5.1 will eventually be the basis that a cost driver will be taken from as the battery systems
are further investigated. The vanadium flow battery has multiple vanadium states in the
catholyte and anolyte as the reactions take place which affects the composition of the double
cell system.
2.5.1 Chemical Compositions and Concentrations
Various materials and chemicals also have a mixture composition to maintain a cost effective
material while still achieving the desired battery potential. Electrolytes particularly can be
diluted or mixed with a different chemical if costing is too great or effectivity is greater in the
electrolyte complex. It is therefore important to take this into account especially with the
costing analysis of each electrolyte as diluted electrolytes are very common in batteries.
Vanadium(V) oxide used as an electrolyte in the VRB is a mixture of V2O5 and sulphuric acid
mixture which is used in concentrations that maintain battery efficiency while being a
relatively cost effective electrolyte. For the VRB and zinc- bromide batteries, concentrations
of 2 – 3 mol/L of the major chemical is standard (Hashimoto, 1993). The nickel metal-hydride
electrolyte of either potassium hydroxide or sodium hydroxide is normally around 30% by
volume with water (Linden, 2002).
2.5.2 Varied Materials
Nickel metal – hydride batteries can use various cathode materials. Different cathodic
materials may hinder performance or costing so it is suited to the task of the battery.
According to Dell and Rand, the metal-hydride cathode should; have high storage capacity,
prove to be safe, have good corrosion resistance, repeat cycles without change in pressure
and temperature characteristics, and also form and decompose at any appropriate rate (Rand
2001). To make a useful analysis for the nickel metal-hydride batteries, some common
cathode materials can be analysed. Table 2.5.2 shows just a small list of cathodic materials
that can be used in the nickel metal-hydride battery.
21 | P a g e
It is important to analyse each component and the most common material that is used. The
availability of the material, costing for processing, the mineral reserves and also the effectivity
of the materials should be taken into consideration as various effective materials may be used
at a cheaper cost. Assessing all of these factors in each case will develop a method to find the
cost driver for each energy storage system.
22 | P a g e
Table 2.5. 2: Sodium alanates used as metal-hydride cathodic materials (Sakintuna, 2006).
Materials Method Temperature
(C ) Pressure (bar) Kinetics (min)
Cycling stability
Max wt % of H2
Na3AlH6 Mechano-chemical synthesis
Tdes: 200 Pdes: 1 Tdes: 150 No Data 2.5
Na2LiAlH6 BM Tabs: 211 Pabs: 45 Tabs: 100 No Data 2.5
NaAlH4-2 mol %
BM Tabs and Tdes:
125-165 Pabs & Pdes: 101-202
Tabs: 60 5 cyc.: not
stable
3 Ti(Obun)4-
2 mol % Zr(Opri)4
BM - - Tdes: 180 stable
NaAlH4-4 mol% Ti
BM Tabs: 120 Pabs: 120 Tabs: 60 8 cyc.: not
stable 3.3
Tdes: 150 Pdes: 1 Tdes: 600
NaAlH4-2 mol % Ti
BM Tdes: 25-160 Pabs: 20-120 Tabs: 300 - 720
No data 3.8 Tabs: 25-193 Pdes: 1 Tdes: 40
NaAlH4-2 mol %
(Ti(Obun)4 Mixing
Tabs: 120 Pabs and Pdes: 60-150
Tabs: 1020 25 cyc.: not stable
4 Tdes: 180-260 Tdes: 120-300
NaAlH4-2 mol %
Ti(Obun)4 Mixing
Tabs: 135 - 120 Pabs and Pdes: 150-130
Tabs:330 33 cyc.: not stable
4 Tdes: 180-160 Tdes:90
NaAlH4-2 mol % TiCl3
BM Tdes: 125-100 Pdes: 83-91 Tdes:20 5 cyc.: not
stable 4
NaAlH4-2 mol %
Zr(OPr)4 Mixing Tdes: 200 Pdes: 1 No Data
3 cyc.: stable 3 after
second cyc 4
NaAlH4-2 mol %
Ti(Obun)4 Mixing Tabs: 104 Pabs:88 Tabs: 1020
3 cyc.: stable after second
cycle 4
NaAlH4 Mechano-chemical synthesis
Tabs and Tdes: 80-180
Pabs and Pdes: 76-91
Tabs: 120-300 2 cyc.: not stable
5
Tdes:300
NaAlH4-2 mol %
Ti(Obun)4-C
Mixing Tdes: 200 Pdes: 1 No Data Not Stable 5
NaAlH4-2 mol % TiN
BM Tabs: 104-170 Pabs: 115-140 Tdes:30-1200 25 cycle:
stable after 17th cycle
5
Tdes: Desorption time
23 | P a g e
2.6 Processing
The cost analysis for the studied energy storage systems can be broken down into four major
parts including;
• Sustainability
• Applicability
• Performance
• Materials and individual components
Studying the materials and the individual components may lead to cost drivers of which can
be reduced. Some sections that can be changed within the battery to reduce the overall cost
and make a battery a more viable option include;
• Material cost reduction
• Chemical cost reduction (electrolyte)
• Changing the design of the battery
• Additions that may aid in the performance of the battery such as reagent or
conditional changes (temperature and pressure)
As the material costing tends to be the cost driver in most applications, observing processing
techniques is a critical method that could lead to the reduction of cost. Many energy storage
system elements are processed and produced in different methods so it is important to find
which elements are expensive to produce starting at the mining processes.
Ore bodies and reserves are also an important factor to analyze the sustainability of the
battery and to achieve battery viability estimates assuming the energy storage systems are
commercialized. Materials are produced all over the world through different processes due
to the mineralogy so it is crucial to understand trends to find costing figures.
24 | P a g e
2.7 Major Ore Deposits and Mineralogy
2.7.1 Vanadium
Vanadium is usually mined as a by-product and is not typically mined from individual mineral
sources. Found in over 65 minerals, vanadium resources have found to exceed well over 63
Mt. The majority of vanadium is found in phosphate rocks, titaniferous magnetite, uraniferous
sandstone, siltstone as well as carboniferous materials such as crude oil, coal, oil shale and
tar sands (USGS, 2016). Vanadium processing is largely associated with titaniferous magnetite
as it accounts for 85% of vanadium production (Investing News, 2016). As vanadium is mined
as a by-product and is found in various different minerals, it is best to recognize vanadium
product by country. China, South Africa, Russia and Brazil are the four leading producers of
the vanadium resource V2O5 that can be further processed to be used in the vanadium redox
flow battery system. At 0.042 Mt of vanadium produced in 2016, China poses to be a large
contributor to the vanadium stocks however large vanadium sources can be found in
Australia. This suggests that Australia may be a future major producer of the sustainable
battery (Australian Shares, 2016).
Table 2.7. 1: Elemental reserves and production for 2016 (USGS, 2016).
Element Reserves (Mt) Production (Mt) 2016 Sustainability (years)
Vanadium 63 0.076 829
Lithium 40 0.035 1143
Cobalt 25 0.123 203
Nickel 130 2.25 58
Lead 2000 4.82 415
Zinc 1900 11.9 160
25 | P a g e
2.7.2 Nickel
Nickel used in the nickel metal – hydride batteries as well as the anodic material for the
lithium – ion battery is in abundance in various countries. Estimated nickel reserves are
approximated at around 130 Mt with 2.25 Mt of that being processed in 2016 alone. Leading
nickel producers include the Philippines, Canada, Russia and Australia respectively, although
the largest amount of nickel reserves by country is Australia (USGS, 2016). Major minerals
that contain the nickel include pentlandite, millerite, niccolite, garnierite and also the nickel
replacement in pyrrhotite. The high amount of nickel being processed in a single year show
the world wide processing and availability of nickel (British Geological Surveys, 2008).
Figure 2.7. 1: World selected element reserves as of 2016.
0
300
600
900
1200
1500
1800
2100
Vanadium Lithium Cobalt Nickel Lead Zinc
Res
erve
s (M
t)
26 | P a g e
2.7.3 Lead
Lead which is used in the lead – acid battery has a large reserve of over 2000 Mt. Australia,
China, Russia and Peru are the leaders in lead reserves respectively as of 2016 (Statista, 2016).
Galena is the main mineral that contains the lead at high amounts. Cerussite and anglesite
also make up large amounts of the lead reserve as an oxidized lead mineral (Government of
South Australia, n.d.). Of this 2000 Mt reserve, 4.82 Mt of lead was produced in 2016 alone.
This larger amount of lead reserve also shows a large production of the lead. The supply and
demand of lead is the main contributor to the large process (USGS, 2016).
2.7.4 Lithium
Lithium resources used to create the anode and electrolyte for the lithium ion battery is on
high demand as renewable energies are being pursued. With a reserve of over 40 Mt, lithium
is being produced predominately by Chile, China, Argentina and Australia respectively at
around 0.035 Mt in 2015 (USGS, 2016). Although found in over 100 minerals, major lithium
bearing minerals that are economically viable to process include spodumene, lepidolite,
petalite, eucryptite and jadarite. Lithium can also be processed from brines which is a fluid
that contains the dissolved lithium element. Although in small concentrations, large amounts
of lithium can be processed from these fluid bodies. With major deposits in Australia, South
America and China, Figure 2.7.3 shows the various major lithium ore deposits including major
brine processes for the production of lithium (British Geological Survey 2016).
Figure 2.7. 2: World elemental production of each investigated element in 2016.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0
2
4
6
8
10
12
14
Nickel Lead Zinc Cobalt Vanadium Lithium
Pro
du
ctio
n (
Mt)
Pro
du
ctio
n (
Mt)
27 | P a g e
2.7.5 Zinc
Zinc is used for the electrolyte in the zinc-bromine battery. As of 2011, zinc reserves estimated
around 1900 Mt. Majority of the zinc reserve was found in Australia, China and Peru. Of the
three countries with major zinc reserves, China is the world’s leading producer of zinc at
nearly 5 Mt of zinc in 2011 (Asian Minerals, 2013). Zinc minerals that are economically viable
to process are sphalerite, smithsonite and willemite (MEC n.d.).
2.7.6 Cobalt
Cobalt is used in the lithium ion (cobalt complex) battery. Used as one of the main elements
of the anode, it is a large determinant as to whether the lithium ion battery is viable in terms
of sustainability. As of 2016, found cobalt reserves accumulated to approximately 25 Mt. The
amount of cobalt mined in 2016 is around 0.123 Mt world-wide. These reserve and
production figures are based primarily off terrestrial ore deposits. Cobalt has also been found
in manganese nodules on the crusts of the oceanic floor that account for some 120 Mt. These
nodules that contain the cobalt however are not included in the overall reserve as mining
processes have not been used. Some leading producers of cobalt include China, Canada and
Congo, who produced the largest amount of cobalt at 0.066 Mt in 2016. Majority of cobalt is
found in sediment hosted copper ores (USGS, 2017).
2.7.7 Reserve and Production Summary
As shown in Figure 2.7.2, although small compared to zinc and lead, vanadium has quite a
large reserve and exceeds lithium which suggests that vanadium redox flow batteries can be
sustainable for the future. Having large sources of vanadium and small production shows that
the battery may contain large future potential. Lithium although not as abundant as vanadium
also has considerable amount of deposits that can be used to sustain lithium ion batteries
into the future. Sustainability figures can approximate element life if production was to
continue at the 2016 rate with no new reserves found. As shown lithium and vanadium are
the most sustainable elements currently.
28 | P a g e
Fig
ure
2.7
. 3: M
ajo
r lit
hiu
m p
roce
ssin
g o
per
ati
on
s a
da
pte
d f
rom
Bri
tish
Geo
log
ica
l Su
rvey
s (2
00
8)
29 | P a g e
2.8 Processing Options
2.8.1 Nickel
Nickel can be processed by hydrometallurgical or pyrometallurgical processes. The difference
in processes usually depends on the mineral composition. Nickel sulphide ores usually
undergo crushing, flotation, thickening, smelting and refining where a high purity nickel
product is formed. The sulphide ores that undergo pyrometallurgical processing can also
incorporate hydrometallurgical processing, where solvent extraction is used to separate the
nickel-cobalt matte into nickel and cobalt (usually in sulphide ores). Electro refining is then
used to produce the nickel on the cathode. A high pressure acid leach can also be used to
recover the nickel using high concentrations of sulfuric acid and high pressures. This high
pressure acid leach has been used for over 60 years. (Metalpedia, 2016).
2.8.2 Lead
Lead sulphide ores are usually concentrated by flotation (as sulphides are generally easy to
float). The concentrate is then roasted and then smelted for reduction purposes. In this
indirect smelting process, impurities are skimmed from the top to produce high grade lead.
Direct smelting is also an option as no coke is required and also pollution is quite minimal.
The remaining impurities from the lead bullion can be removed by electro refining or further
pyrometallurgical processes (Ponikvar, 2016).
30 | P a g e
Figure 2.8. 1: Sphalerite mineral containing zinc sourced by Wikimedia Commons
2.8.3 Vanadium
Vanadium is produced by various methods as the element exists in many forms. Hot sulphuric
acid is used to leach carnotite over a 24-hour period. The leached solution which consists of
both uranium (as uranium is usually a co-product with vanadium) and vanadium are extracted
by solvent extraction in two different stages. Ferrovanadium is processed by the electric arc
furnace. The oxidation reduction reaction that takes place within the furnace allows for the
separation and hence production of the vanadium pentoxide (Moskalyk, 2003).
2.8.4 Cobalt
Cobalt is processed through a number of different methods. Copper-cobalt ores account for
quite a large amount of cobalt reserve. The ore is usually floated to separate the minerals into
a concentrate. The use of an electric-arc furnace reduces the cobalt in the copper-cobalt
complex ores. After the electric-arc furnace, the compound is then leached to extract the
cobalt and nickel from ore. The cobalt is then removed from the leach solution by electrolysis.
(Taylor, 2017). Both pyrometallurgical and hydrometallurgical processes can be used to
extract the cobalt.
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2.8.5 Zinc
Zinc sulfides are concentrated usually through the flotation process. Once concentrated, the
zinc sulfides undergo roasting, smelting and then electrolysis. Fluidized bed roasters are
typically used to remove the sulfur before the blast furnace is used to reduce the zinc sulfides
and in some cases separate concentrates such as lead and zinc. Electrolysis is used to produce
the zinc sulfate solution and purify for electrowinning (Richards, 2011). The sphalerite mineral
shown in Figure 2.8.1 contains the zinc element.
2.8.6 Lithium
Spodumene is the main lithium bearing mineral. The spodumene is usually first floated to
produce a concentrate. The concentrate is then dried and sent to a roaster which is standard
practice. The redox process is followed by a leaching circuit to extract the lithium. Once
leached the solution is extracted and undergoes electrowinning to produce lithium. Brines
that contain lithium (large source) undergoes an evaporation process that goes over long
periods of time (18 months) (Bohlsen, 2016). The evaporation followed by leaching produces
a lithium concentrate for purification.
2.8.7 Processing Summary
Observing sustainability factors in relation to each battery element, it is deduced that Lithium-
ion, lead acid and vanadium redox flow are the most sustainable batteries that need to be
examined. This deduction was made from considering both elemental reserves and elemental
production. Although vanadium, lithium and cobalt do not have a large reserve, production
rates are small compared to nickel, lead and zinc. Lead however has a large reserve which
suggests that even though production is high, the element can be produced in the future. Not
accounting for production and reserve fluctuations, the lithium ion battery has abundance of
lithium and cobalt while the vanadium redox flow also has high amounts of vanadium to be
processed. Although nickel and zinc have large reserves, production suggests that within 58 -
160 years, both nickel and zinc will be depleted (not considering reserve fluctuations). These
three batteries will be investigated further.
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2.9 Battery Effectivity & Efficiency
The process of elimination can aid in the selection of a battery once a cost driver has been
found. To select a battery that will be worth-while to investigate however is the main
problem. Observing battery characteristics can be a useful tool in comparing batteries to find
which batteries are most suited to the markets and customer demand. Some main
characteristics that can have major influence on battery efficiency and effectivity include cell
voltage, capacity, recharge time, amount of cycles, self-discharge rate, operable temperature
and energy density. These characteristics however must be compared to each other in context
with the usability of the battery.
Table 2.9. 1: Characteristics of each battery system compared to each other (Linden, 2002).
Characteristic Lithium-Ion
(Nickel Cathode) Lithium-Ion
(Cobalt Cathode) Vanadium Redox
Flow Lead-Acid
Operational Cell Voltage (V) 3 - 4 3 - 4 1.4 2.1
Specific Capacity (Ah/kg) - 100 21 120
Specific Energy (Wh/kg) 150 360 29 252
Recharge Time (hr) 2.5 - 6 - 10 8 - 24
Cycle Life (Cycles) 400 600 3000 500
Self-Discharge Rate (%/Month) <3.5 - 5 - 10 3
Operable Temperature (C°) -20 - 45 -20 - 60 10 - 50 -20 - 50
Energy Density (Wh/L) 400 410 10 80
2.9.1 Operational Cell Voltage
The open circuit cell voltage for the lithium ion batteries are the highest in comparison to the
redox flow and lead acid. Vanadium redox flow battery although significantly smaller in
capacity, energy and voltage does have some factors associated. The vanadium redox flow
battery is much more applicable to scaling than other batteries. Increasing the size of the
battery requires more electrolyte and carbon electrodes while lithium-ion and lead acid
require much more components to upsize. These low energy capacities and voltages are then
countered with the easy increase in size of the vanadium redox flow.
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2.9.2 Specific Capacities
For Lithium ion and lead-acid batteries, energy capacities and voltages need to be quite high
due to the use of the battery. Primarily used in portable batteries for motors and automotive
vehicles, the batteries need to be able to operate at high voltages to supply the demand of
energy. The high energy capacities of both lithium-ion and lead-acid are linked to the amount
of energy needed for it to be useful to the automotive industry and attract marketable value.
Vanadium redox flow batteries are used for grid scale application which suggests that
although characterised as a low capacity and voltage battery, larger scale systems can in the
future provide varying energy outputs with varying sizes.
Figure 2.9. 1: Sumitomo’s redox flow battery shown as a grid scale adapted from Sumitomo Electric (2017)
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2.9.3 Recharge Time
Recharge time is mainly applicable to portable batteries. The lead-acid and lithium-ion
batteries need to have relatively low recharge times to maintain viability towards portable
batteries for automotive applications. As the lithium-ion battery has quite a low recharge time
it becomes very applicable to the automotive industry as the battery usage is quite high. The
vanadium redox flow battery is used mainly on a grid scale where it can constantly be charged
with minimal battery deterioration. This suggests that self-discharge rate is also not heavily
applicable to the vanadium redox flow battery as constant charging can be done. Lithium-ion
batteries and lead-acid batteries have similar self-discharge rates which are quite minimal.
2.9.4 Operable Temperatures
As the vanadium redox flow battery is mainly composed of vanadium electrolyte, it is
important to note the operable temperatures of the cell system. The flow battery has a lower
operable temperature due to precipitation and freezing of electrolyte. This is a problem for
low temperature climates however heating systems can be implemented especially for large
grid systems. The Li-ion and Lead acid batteries can be used in multiple applications including
portable batteries due to the characteristic of having large operable temperature ranges. This
large temperature range means that the portable batteries can be used widely around the
world in a variety of climates.
Figure 2.9. 2: Projected installed capacity for three different batteries adapted from MSE Supplies (2015)
0
200
400
600
800
1000
1200
1400
1600
2013 2014 2015 2016 2017 2018 2019 2020 2021
Cap
acit
y (M
W)
Advanced Flow Battery Advanced Li-ion Battery Advanced Lead-Acid Battery
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2.9.5 Battery/Cycle Life
Battery life is a major factor in the determinant of an energy storage system viability. The
main advantage that the vanadium redox flow battery has over other energy storage systems
is the long battery life through cycles. The flow battery can go through above 3000 cycles
without having an effect on electrolyte and capacity which means the life of electrolyte is
‘infinite’. Compared to the lithium-ion and lead-acid the flow battery is far superior in terms
of battery life which makes it more applicable to large scale systems as it won’t have to be
replaced often. Small scale portable batteries can be replaced relatively easy and thus smaller
battery life is acceptable. Increasing the amount of cycles with the lithium-ion could be a
driver that would increase applicability of the lithium – ion battery.
2.9.6 Effectivity and Efficiency Summary
The two main advantages that can be taken from the energy, capacity and durability data in
Table 2.9.2 is; the vanadium redox flow battery has a large cycle amount meaning it is useful
to large scale systems and also that the lithium – ion battery has great energy efficiency
making it applicable to portable energy storage and automotive applications. By observing
the differences in lithium ion cobalt and lithium ion nickel batteries, conclusions can be made
about the use of cobalt. As shown, the cobalt cathodes do have an effect on the efficiency of
the battery system with an increased amount of cycles, an increased energy density and
increased energy capacity.
As batteries with the most potential in terms of sustainability and battery efficiency have a
higher chance of change in cost driver, these batteries will be further investigated; the lithium
ion with cobalt cathode, the lithium ion with the nickel cathode and the vanadium redox flow.
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2.10 Cost Comparisons
By observing a cost breakdown for each battery, it is possible to find cost drivers that may
affect the overall marketability of the battery. Batteries come in different variations with a
wide range of elements, suggesting that a comparison between them is quite difficult. Overall
battery breakdowns however can be compared to find which batteries are the most efficient
under a single unit. As the aim of this investigation is to find the cost drivers behind multiple
batteries to identify potential changes that decrease costs in batteries, the cost comparison
is a crucial factor.
2.10.1 Lithium Ion Battery
The lithium ion battery with the different cathodes and the vanadium redox flow battery will
be compared in capital costings.
Figure 2.10.1 shows the lithium ion battery breakdown in capital costings. This particular cell
is assumed to be using a 96 Wh PHEV cell with an NCM622 cathode (use of cobalt). Elemental
material prices are; US 7.00 $/lb nickel, US 12.00 $/lb cobalt, US 1.00 $/lb manganese and US
6.50 $/lb lithium.
Figure 2.10. 1: Lithium ion battery cost breakdown into cathodic elements adapted from Berger (2012)
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Table 2.10. 1: Cost breakdown of lithium ion battery (cobalt cathode) (Novo 2016).
Lithium - Ion (Cobalt Cathode)
Component Cost (US$/kWh) Material Costs (US$/kWh) Percentage (%)
Overhead 64.23 - -
Labour 9.52 - -
Cathode 40.48 40.48 27
Anode 21.43 21.43 14
Electrolyte 21.43 21.43 14
Separator 19.05 19.05 13
Other Materials 50.00 50.00 33
Total Cost 226.14 152.39 100
As shown, the capital costs supplied by Novo and Berger (2016 & 2012) are very similar.
Cathode costing is heavily weighted in capital cost with the focus on nickel and cobalt.
Accounting for approximately 78 % of the cost of the cathode material and 39 % of the overall
cost of battery, Berger’s model gives indication that nickel and cobalt are large cost drivers in
the lithium-ion battery. Berger’s model suggests around US 240 $/kWh while the Novo data
suggests around 226 $/kWh. With fluctuations in price as a factor, it is very similar and
therefore is a reliable estimate.
27%
14%
14%
13%
33%
Cathode Anode Electrolyte Separator Other Materials
Figure 2.10. 2:Capital cost fractions pie chart showing distribution of costings for lithium ion.
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2.10.2 Vanadium Redox Flow Battery
Table 2.10. 2: Cost Breakdown of the vanadium redox flow battery (VRFB) (Moore 2013).
Vanadium Flow Battery
Component Cost (US$/kWh) Percentage (%)
Total Cost of Stack 117.10 31
Pump Costs and Heat Exchangers 11.33 3
Cost of Electrolyte Tanks 30.22 8
Total Cost of Vanadium 139.76 37
PCS, Transformer, etc. 79.32 21
Total Cost 377.73 100
Figure 2.10. 3: Capital cost fractions pie chart showing distribution of costings for VRFB.
Table 2.10.2 and Figure 2.10.3 show the overall distribution for cost breakdown of the
vanadium redox flow battery. Suggested by the pie chart, the vanadium electrolyte accounts
for a large portion of the overall capital cost of the vanadium battery, 37 % to be exact.
31 %
3 %
8 %37 %
21 %
Total Cost of Stack Pump Costs and Heat Exchangers
Cost of Electrolyte Tanks Total Cost of Vanadium
PCS, Transformer, etc.
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Observing total capital cost for both batteries shows large differences. US 377.73 $/kWh
compared to US 226.14 $/kWh shows just where the two batteries are in terms of
development. The VRFB is grossly expensive compared to the lithium battery, however in
context the extra cost is justifiable. The cycle life for the VRFB is nearly 4 times that of the
lithium ion battery which suggests that although an expensive battery is costed, it makes up
for it in battery life and cycle amount. As of 2017, the two batteries have different applications
in the world. One battery poses to be a grid scale energy storage system, while the other is
best suited currently to portable devices for relatively short use and high energy throughputs.
2.11 Critical Cost Drivers
Following the cost analysis, the critical cost drivers can be found which provides avenues to
minimize costs. In the lithium – ion battery with cobalt used as the cathode, the cathode
showed to have the highest expense in comparison to other materials and parts. The cathode
alone accounts for 39 % of the overall expenditure suggesting that the critical cost driver is
certainly the cobalt and nickel in the cathode.
The vanadium redox flow battery’s critical cost driver is the vanadium electrolyte, which
accounts for 37 % of the total cost. To decrease the market value of the battery, it is necessary
to decrease the cost of vanadium production.
By comparing the cost drivers, vanadium electrolyte is considerably more expensive than the
cobalt cathode, which indicates a large potential for reduction of costing.
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2.11.1 Sensitivity Analysis
A sensitivity analysis has been used to examine the critical drivers for supporting evidence. By
exposing the individual component costs of both the lithium-ion and vanadium redox flow to
fluctuations in increments, the critical cost drivers can be deduced from the largest price
change. Figure 2.11.1 shows that the critical cost driver of the vanadium redox flow battery is
the vanadium electrolyte, indicated by the largest price changes at 10 and 20 % fluctuations.
Costing of stacks also accounts for large amounts of the vanadium redox flow battery cost.
Figure 2.11.2 shows the fluctuation in price for the lithium ion battery. Eliminating ‘other
materials’ as it is comprised of multiple small components; the cathode has the largest cost
influence on the lithium ion battery. An increase or decrease of 20 % for the cathodic material
in price will lower the overall cost of the lithium ion battery immensely.
Figure 2.11. 1: Sensitivity web diagram for the fluctuation of each vanadium battery component
-30
-20
-10
0
10
20
30
-25% -20% -15% -10% -5% 0% 5% 10% 15% 20% 25%
Dif
fere
nce
in c
ost
(U
S$/k
Wh
)
Input Fluctuation
Cost of Stack Pump and Heat ExchangersElectrolyte Tanks Vanadium ElectrolytePCS, Transformers, etc.
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Figure 2.11. 2: Sensitivity web diagram for the fluctuation of each lithium-ion battery component
2.12 Summary
The investigative study to obtain cost drivers in various energy storage systems has been
achieved. By analyzing economical, sustainability and efficiency factors for the zinc bromide,
lithium ion, lead acid, vanadium redox flow and nickel metal-hydride batteries, cost drivers
were found that would have the biggest impact in the renewable energy storage market.
It was found that through a sustainability analysis, the nickel-metal hydride and zinc bromine
batteries were found to be less sustainable compared to the lithium ion, lead acid and
vanadium redox flow batteries. Being produced at 11.9 and 2.25 Mt per year respectively,
zinc and nickel are less sustainable compared to the other investigated batteries. Elemental
reserves and production rates were taken into consideration to achieve a general ‘element
life’ which aided in the investigation of the most sustainable, economic and efficient battery
for cost driver findings.
-10
-8
-6
-4
-2
0
2
4
6
8
10
-25% -20% -15% -10% -5% 0% 5% 10% 15% 20% 25%
Dif
fere
nce
in c
ost
(U
S$/k
Wh
)
Input Fluctuation
Cathode Anode
Electrolyte Separator
Other Materials
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Comparing efficiency, cycle life and capacity data allowed for good conclusions to be made of
the lithium ion battery and the vanadium redox flow batteries, given the current applications.
The vanadium redox flow battery poses to be a long term grid scale energy storage system
due to the 3000 cycles for the electrolyte life, while the lithium ion battery proved to be
applicable for portable devices and high energy output systems due to its high operational
cell voltage of around 3 – 4 volts. These two factors a marginally higher than the other
investigated batteries therefore were chosen to be cost analyzed further.
The economic analysis was based around the batteries with the largest potential, being
lithium ion and VRFB. The analysis concluded that the cost drivers in the VRFB was the
vanadium electrolyte with a 37 % cost composition of the overall battery, while the lithium
ion cost drivers was the cobalt and nickel in the cobalt cathode with a cost weight of 39%.
A decrease in vanadium electrolyte process cost will have a larger effect on the market than
the reduction in cost of processing cobalt. Reasoning is due to the cost breakdown of both
batteries, which suggests the vanadium electrolyte has a higher cost weight compared to the
cobalt cathode.
Solubility data suggests that refining vanadium increases the overall solubility of electrolyte
which increases efficiency of the vanadium battery. Refining the V2O5 with a cost effective
method will decrease the costing of the vanadium energy storage system. Specialized leaching
and electro-refining techniques are avenues that may be able to obtain the vanadium from
ore at a lesser cost. As carnotite is a major vanadium bearing mineral, flotation on the
uranium – vanadium mineral may be an option to produce a concentrate for leaching. If a
concentrate can be produced that contains a higher grade of uranium and vanadium,
sequential processing will be vastly cheaper. Studying conditions around the selective
flotation of uranium and vanadium would be an interesting avenue.
Extracting nickel or cobalt from ore with a cheaper process will reduce overall costing of the
battery remarkably. As electric arc furnaces heavily influence the cost of processing the
cobalt, reducing the cobalt by cheaper methods may introduce a decrease in costings.
Flotation of cobalt can be examined to alter conditions which has potentials of decreasing
operational cost of processing. The flotation of copper-cobalt ores may reduce costings by
decreasing throughput and increasing grade for the electric arc furnace.
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Chapter 3 – Experimental Methods
3.1 Introduction
Finding a methodical approach into this investigation in regards to test work is quite
complicated and technical. In this chapter, these methods are clearly outlined and discussed
to prove relativity and accuracy within the results. From how the test work was conducted to
the materials and resources used, the lithium ion battery recycling test work needed to be
accurate in order for the results to be valid. Points of error are discussed and room for
development within the research test work. For test work replication, it was necessary to
clearly define the test work procedure to create a recycling process that may be of use in the
future.
3.2 Sample Source, Reagents and Equipment
3.2.1 Lithium ion batteries
Lithium batteries are constructed from materials that are specific to its use. It is therefore
important to choose a battery that is composed of the materials selected for leaching. The
alteration of battery components is directly linked to its performance and cost. The anode
material is generally similar in most lithium ion batteries, being carbon graphite. The
electrolyte is varied from one battery to another to increase or decrease capacity, costing,
storage life and performance. As the lithium electrolyte was not of importance in the leaching
stage, this component was disregarded.
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Figure 3.2. 1: Lithium ion battery breakdown (Physics Central 2017)
The cathode was the sole factor in the choice of lithium ion battery. As nickel and cobalt were
found to be the costliest elements in the lithium ion battery, the cathode needed to be
composed of cobalt and nickel to be leached. A safe battery was mandatory as the
disassembly posed to be a dangerous factor. The lithium ion ICR - 18650 was the battery of
choice as it was quite small and relatively easy to disassemble. The ICR has high amounts of
cobalt in the cathode which means that a cobalt leach can be achieved (Battery Bro, 2015). A
generally low voltage of 3.7 V could easily be discharged which meant that time taken to
disassemble and discharge multiple batteries would be made possible in a short period of
time.
According to research into the cleaning of lithium-ion cathodes, a large portion of the battery
weight is attributed to the cathode. This reflected to be useful as the amount of cathode
powder extracted from the lithium ion could be used in the leaches. The greater the weight
of cathode material, the less batteries needed for the test work. Although all batteries are
different in terms of composition and weights, the test work by Toma can be used as a relative
reference guide as to how many batteries were needed, in this case 20 seemed sufficient
(Toma, 2017). Table 3.2.1 represents the battery weight breakdown and shows the high
amount of cathode material.
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Table 3.2. 1: Battery weight breakdown for a lithium ion battery
Component Weight %
LiCoO2 (Cathode) 27.5
Steel/Ni 24.5
Cu/Al 14.5
Carbon 16
Electrolyte 3.5
Polymer 14
3.2.2 Acids
As the aim of this research is to find a cost effective method in the recycling of spent lithium
ion batteries, it is important to keep the process cost and reagent cost low. Many different
acids can be used in the leaching of nickel and cobalt however choosing a cost effective acid
that will achieve high recovery is necessary. Sulfuric acid (H2SO4) was used in this test work as
the inorganic acid proves to be effective with many leaching procedures and is also cost
effective.
Metals have been extracted and leached into solution with the use of sulfuric acid in a wide
range of cases. Nickel and cobalt which are the desired elements to be leached from the spent
lithium ion battery cathode material have both been leached with the use of sulfuric acid
(Ognyanova, 2009) (Sohn, 2006). In both cases cobalt and nickel recoveries were above 90 %
showing the effectivity of sulfuric acid on the leaching mechanism.
A solution of 96 % v/v sulfuric acid was used and diluted to the given concentrations of acid
needed for the test work. Nayl et al. (2017) tested multiple sulfuric acid concentrations and
found that 2 M was optimum suggesting that not a high concentration is necessary for
extraction (Nayl, 2017).
3.2.3 Catalyst
Hydrogen peroxide (H2O2) is commonly used with the dissolution of cyanide however in this
case, it is used to create cobalt 2+ ions. The cobalt (II) ions are readily leached into solution
making it a faster method than common oxidation from air. As the reaction rate is dependent
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on diffusion coefficient of cobalt ions, it makes sense that the cobalt 2+ ions increase the
reaction rate and create a faster leaching mechanism (Deng, 2007).
The equation for reaction rate of leaching is;
𝑘𝑝 = 2𝑏𝑀𝐷𝐶
𝑝𝑟2 where D = diffusion co-efficient of cobalt ions. [1]
A solution of 30 % w/v hydrogen peroxide was used in liquid state and this was key to keeping
the costs low and also testing to see if extraction would still remain high. Nayl et al. (2017)
used 4 % H2O2 obviously at a higher w/v however keeping costs low was crucial for the
commercialization of the process (Nayl, 2017).
The chemical reaction taking place with the addition of H2O2 is;
2𝐿𝑖𝐶𝑜𝑂2(𝑠) + 3𝐻2𝑆𝑂4(𝑙) + 𝐻2𝑂2(𝑙) → 2𝐶𝑜𝑆𝑂4(𝑙) + 𝐿𝑖2𝑆𝑂4(𝑙) + 4𝐻2𝑂(𝑙) + 𝑂2(𝑔) [2]
3.2.4 Equipment
Some pieces of equipment were quite minor in the process and some major. It is important
to outline the equipment as replication of results can be made easier or even optimized with
more effective equipment types and specifications.
• X-Ray Diffraction (XRD) – Used to characterize the material found in the lithium ion
batteries and produce findings into specific elements for the leach feed.
• Atomic Absorption Spectroscopy (AAS) –Used to find concentration of elements
within leach liquor to determine effectivity of test work. The AAS machine used was a
55B AA Agilent Technology system.
• Inductively Coupled Plasma Mass Spectrometry (ICP-MS) – Used for characterisation
of leach feed material and also concentrations of leach liquors. This machine was used
by Nagrom Metallurgical for feed leach concentrations.
• Fume Hood – Extraction of harmful vapors and mitigation of odors from lithium
electrolyte material during battery decomposition and also vapors from leaches.
• Heated Bath – Used to maintain leaches at desired temperature and keep solids in
suspension to optimize surface reaction with acids.
• Beakers, flasks, measuring cylinders, sample bottles, pipettes etc.
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3.3 Method
3.3.1 Battery Discharge
To safely disassemble a battery, it is mandatory to ensure it is fully discharged. Batteries that
still contain charge have the ability to short, explode or catch on fire. A well investigated
process was needed to discharge the 18650 lithium ion batteries.
A few options were considered such as the discharging through salt water, short circuiting, a
lightbulb circuit configuration, laptop discharge and also a resistor circuit. In many case
studies, the pre – treatment of lithium ion batteries was made simple as the batteries were
recycled meaning that they had no charge. The batteries purchased however were fully
charged at 3.7 V. In 2017, Chen et al used an electrolyte solution to discharge the batteries to
0.0 V (Chen 2017). The ions in solution allow for the complete discharge of the battery
however the process is quite long for batteries with full charge.
Short circuiting was an option however due to the large amount of current flowing through
the battery, the lithium ion battery started to smoke suggesting that there was not enough
resistance. A resistor circuit was the easiest method to discharge the batteries safely. Using
multiple 1 ohm resistors in series due to the 3.7 V voltage, the batteries would deplete in
charge within 20 – 30 minutes. The voltage however would remain at approximately 1.7 V as
a safety mechanism built inside the battery faults the discharge when going below a certain
voltage. Although the resistors were very hot, it was a safe and relatively fast method to
discharge the 20 batteries. The battery packaging was used to hold the battery during
discharge. This is shown in Figure 3.3.1.
Figure 3.3. 1: Discharging mechanism for battery
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At 1.7 V, the batteries carried no charge and were safe enough to dismantle. Multiple checks
were done on the battery before it was dismantled to make certain that little to no charge
was in the lithium ion 18650 battery.
3.3.2 Battery Deconstruction
The lithium ion 18650 batteries needed to be dismantled very carefully as residual energy
may cause shorting. The tools necessary to deconstruct the batteries were a fume hood for
electrolyte vapors and also a pair of pliers to pry the casing open.
The batteries showed to be quite simple to disassemble and the technique made it easy. By
prying open the top of the battery and removing the ‘cap’ or protector, the casing could slowly
be pulled away into a spiral to reveal the inner layers. Below is a breakdown of the outer
casing of the 18650 lithium ion batteries.
Figure 3.3. 2: 18650 lithium ion battery outer-shell components
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After removing the outer shell casing of the 18650 batteries, the inner roll of cathode, anode
and separator could be found. Unraveling the roll showed the copper sheet coated with
carbon graphite, the aluminum sheet coated with cathode material and the separators which
had both carbon and cathode material attached. A current distributor rod was inserted into
the middle of the roll to transfer current from one terminal to another.
Figure 3.3. 3: Inner-battery components
The three components of the inner battery were separated into beakers for further
processing and cleaning. It was important that all test work was performed under a fume
hood to decrease lithium electrolyte vapor contact. The electrolyte was very odorous and in
some cases very hot when shorted.
Figure 3.3. 4: Separated components showing cathode, separator and anode material respectively
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3.3.3 Material Cleaning
Removing the leach feed material from the cathode and anode was quite strenuous as the
material had coated the copper and aluminum. The copper sheet was soaked in DI water to
rinse off carbon graphite material, vacuum filtered and then dried under a heat lamp to
remove excess moisture. Similar processes were repeated for the separator and aluminum
sheet however the nickel-cobalt material was much more difficult to remove and needed to
be scraped off of the surface. The aluminum sheet full clean was not possible as the metal
material was too weak to be scraped. The aluminum sheet with attached LiCoO2 is shown in
Figure 3.3.5.
Figure 3.3. 5: Aluminium foil with attached cobalt and nickel material
Recording weights of material extracted from the battery was quite interesting and showed
little significance with literature findings. Anode material accounted for around 39 % of the
total mass of the battery disregarding the aluminum anode. This finding was not
representative of the whole battery composition as only small amount of cathode material
could be extracted (10%). Although this does not support literature suggested in earlier
sections, it is still possible that more material could be extracted from the aluminum sheets
via better cleaning methods. A cleaning method that could be used is the ultrasonic bath with
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the use of acetic acid. Toma et al. used this process to release the strongly bound nickel and
cobalt material from the sheets (Toma, 2017). Separator material also contains high amounts
of the nickel-cobalt material with the carbon graphite. The separator material can also be
leached for extractive purposes.
Table 3.3. 1: Mass Percentage for components of batteries
Battery Composition (20 Batteries)
Component Mass (g) Mass Percentage %
Cathode Material 31.72 10.37
Anode Material 118.52 38.76
Separator Material 67.25 21.99
Copper Sheet 88.27 28.87
Aluminium Sheet - -
3.3.4 Small-Scale Leaches
The following leaches were undertaken to check for recoveries of cobalt and nickel from spent
lithium ion battery material. The leaching mechanisms of the sulfuric acid can be shown in
the results and discussion component of this thesis. Obtaining the correct parameters was
mandatory to show relevance and also provide a base case for the optimization leach.
Table 3.3. 2: Variable Time Leach Conditions
H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)
2 M 4 % 70 50:1 VARIABLE*
VARIABLE* = 50, 60, 70, 120 and 180 minutes
Table 3.3. 3: Variable Temperature Leach Conditions
H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)
2 M 4 % VARIABLE* 50:1 70
VARIABLE* = 30, 40, 50, 60, 80 C°
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Table 3.3. 4: Variable Acid Concentration Leach Conditions
H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)
VARIABLE* 4 % 70 50:1 70
VARIABLE* = 1, 4 and 6 M
Table 3.3. 5: Variable H2O2 Concentration Leach Conditions
H2SO4 Concentration (M) H2O2 Concentration Temp (C°) L/S mass ratio Time (min)
2 M VARIABLE* 70 50:1 70
VARIABLE* = 0, 2, 4 and 6 %
Once all of the variables have been considered and tested for optimization, an optimization
leach can be conducted to achieve the best possible process for the extraction of cobalt and
nickel material from spent lithium ion batteries using a leaching method.
Table 3.3. 6: Optimisation Leach Conditions
H2SO4 Concentration H2O2 Concentration Temp (C°) L/S mass ratio Time (min)
Optimised Optimised Optimised 50:1 Optimised
Figure 3.3.6 shows the eventual breakdown of the full method with concentrations and mass
percentages for majority of streams. If results are to be replicated or furthermore improved,
it is important to follow a similar method to show relativity.
53 | P a g e
Fig
ure
3.3
. 6: E
ven
t tr
ee s
ho
win
g t
he
met
ho
d f
or
lea
chin
g o
f sp
ent
lith
ium
ion
ba
tter
y ca
tho
de
ma
teri
al
54 | P a g e
3.3.5 AAS & ICP-MS Analysis
AAS analysis was carried out on the leach liquors and wash solutions to analyze for cobalt and
nickel extraction. Below are the standard graphs which were used to show accuracy within
results. As shown by each graph, R2 figures were recorded and are kept relatively high to
assure accuracy. As the leaches were analyzed in two separate dates, two different graphs
are presented for both nickel and cobalt trends.
Figure 3.3. 7: Nickel standard curve 1 showing error and equation
Figure 3.3. 8: Cobalt standard curve 1 showing error and equation
y = 0.0101xR² = 0.9974
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60 70 80 90 100
Ab
s
Concentration (ppm)
y = 0.0014xR² = 0.9997
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 10 20 30 40 50 60 70 80 90 100
Ab
s
Concentration (ppm)
55 | P a g e
Figure 3.3. 9: Nickel standard curve 2 showing error and equation
Figure 3.3. 10: Cobalt standard curve 2 showing error and equation
y = 0.0095x + 0.0463R² = 0.9866
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60 70 80 90 100
Ab
s
Concentration (ppm)
y = 0.0012x + 0.002R² = 0.9988
0
0.02
0.04
0.06
0.08
0.1
0.12
0 10 20 30 40 50 60 70 80 90 100
Ab
s
Concentration (ppm)
56 | P a g e
Chapter 4 - Cathode Characterisation
Characterizing the cathode material is important to understand the leach mechanisms taking
place. Obtaining baseline elemental results in the feed will give indication of how efficient
and effective the leaching was. Multiple assays can bring out an average in elemental
composition which decreases error and shows accuracy in lab results.
4.1 External Cathode Characterisation Assays
The cathode characterisation was carried out through external test work. The initial feed
cathode sample was assayed externally by Nagrom Metallurgical. Nagrom is a local laboratory
operating out of Western Australia that specialize in assaying and metallurgy (Nagrom, 2018).
Triplicate samples were assayed via ICP-MS through the Nagrom laboratory to determine the
elemental composition of feed material to be leached. Obtaining accurate results for the
elemental composition of the cathode material would allow comparisons to be drawn from
the leaches and also gives clear indication of what material is being leached from the feed
material. The samples were extracted from the initial leach feed material by a riffle splitter to
achieve a relatively homogenous sample.
Table 4.1. 1: Cathode, Anode and Separator characterisations via ICP-MS in standard ppm concentrations
Al Co Cu Li Li2O Mn Ni
Units ppm ppm ppm ppm ppm ppm ppm
Cathode 4350 238500 <100 40075 86270 24500 46550
Anode 700 700 300 <100 <100 100 100
Separator 200 279225 200 48000 103340 29900 56400
57 | P a g e
Table 4.1.1 shows the composition of each assayed material. The assays were completed in
triplicate samples to assure representative results and accurate compositions. It was
interesting to assay the separator and anode materials as some notable compositions were
found, shown in table 4.4.1. The two elements to be leached from feed were cobalt and nickel.
Cobalt in both cathode and anode were as expected as the cathode material would have been
predominately LiCoO2, while the anode would have contained more graphite. The given
concentration of 700 ppm in the anode would have most likely been contamination through
the cleaning process.
The nickel concentration in the anode was expected to be quite low however the cathode
nickel concentration was notably low. With cobalt concentration being over 5 times that
amount of nickel concentration, it is evident that the cathode composition was more cobalt
based than nickel based.
The separator findings were also unexpected. Taking the battery apart, it would be expected
to find that the separator material’s cobalt and nickel concentration would be less than that
of the cathode material. This however was proved wrong as both nickel and cobalt
concentrations were higher in the separator material than in the cathode material. This is
most likely due to the inefficient cleaning methods or the discharging method. If the cleaning
methods were the reason for the higher concentrations in the separator than the cathode, it
would most likely be because of the contamination between the two samples. As the powders
within the battery cell were very fine, it was easy to mix the two cobalt and nickel
concentrated powders. Another reason could have been the discharge methods in order to
take the battery apart. As the lithium-ion batteries contained safety mechanisms to stop the
battery from discharging to 0 V, it would have been possible that the ‘cathode’ material was
still being transferred to the aluminum foil, however was stopped by the discharge safety
mechanism. This would mean that a great deal of cobalt and nickel ions would have been
forming on the separator.
In the literature review section of this thesis, it discusses that all batteries have a cycle life
and this produces an irreversible process that disallows the battery to charge, in this case,
this is why the separator contains more nickel and cobalt than the aluminum cathode.
58 | P a g e
Chapter 5 - Leach Results
5.1 Time Variable Results
Using the various leach times, it was possible to draw conclusions into the kinetics and
extraction of each leach. Observing the colors of leach liquor is the first form of noticeable
extraction. The leaches all under various times produced reddish-pink leach liquors suggesting
large amount of cobalt has been leached from the feed solids (Flett, 2004).
Figure 5.1. 1: Pink leach liquor with 50-minute time leach
The time variable leaches were carried out at 50, 60, 70, 120 and 180 minutes. These times
were set to find a general extraction curve with the focus on getting an optimum time. Figure
5.1.2 shows the cobalt and nickel extraction over the given set of times. As shown, nickel
concentration is drastically less than cobalt concentration however a trend is shown. Initial
timings (50, 60 and 70 minutes) show slight decreases in extraction however both elements
are shown to have the highest concentration with the two hour leaches. Cobalt achieves 5.29
g/L into solution while nickel achieves 1.56 g/L into solution.
59 | P a g e
Figure 5.1. 2: Time vs Co & Ni Extraction
As shown, equilibrium for cobalt and nickel in solution occurs in the first 50 minutes of the
leaches. This is shown by the plateau in both elements and only the slight decrease and
increase in concentration of liquor through to the 180-minute test. This gives indication that
the solution is either supersaturated with cobalt and nickel ions and the pulp density needs
to decrease (below 1:50) or all of the cobalt and nickel in the leach feed has been extracted
into solution. Increasing the acid volume to a ratio of 1:75 would increase the capacity for
ions in solution however keeping costs low was a factor. If the leach feed cobalt and nickel
has been fully extracted, increasing the pulp density may be a method in the increase of
concentration of cobalt and nickel in solution. A time leach below 50 minutes could also be
undertaken to find the general curve of the rate of extraction before equilibrium however
cathode material for testing was limited. For optimization purposes however, 2 hour leaches
achieve the greatest concentration of cobalt and nickel ions.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0 50 60 70 120 180
Leac
h L
iqu
or
Nic
kel C
on
cen
trat
ion
(g/
L
Leac
h L
iqu
or
Co
bal
t C
on
cen
trat
ion
(g/
L)
Time [min]
Cobalt
Nickel
// //
60 | P a g e
5.1.1 Change of pH on Time Leach
The change of pH can be linked to the extraction of the leach mechanism. As time increases
the change in pH also increases. These results can be compared to a similar study on the
leaching of cobalt in sulfuric acid solution. Although a longer length of time is trialed, latter
pH changes are similar to test work in that a decrease in pH is found (Sohn 2006). Sohn (2006)
attributed the initial increase in pH of solution to the mixing of acid, showing the initial
increase. After this increase however, pH steadily decreases. Very similar conditions were
used however pulp density does play a key factor into the high recoveries. pH similarities
however can be drawn.
Figure 5.1. 3: pH variation of solution during precipitation (Sohn, 2006)
0.15
0.17
0.19
0.21
0.23
0.25
0.27
0.29
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 13 25 46 70
pH
Pre
cip
itat
ion
Rat
e (e
ffic
ien
cy)
(%)
Time [hr]
// // // //
61 | P a g e
Figure 5.1. 4: Time vs Delta pH
The reason for the decrease in pH over time is due to hydrogen ions into solution. The pH
equation is given below;
pH = -log[H+] [3]
This equation shows the relationship between hydrogen ions and pH. An increase in hydrogen
ions in solution is due to the sulfuric acid reacting with the cobalt oxide material causing a
dissolution of hydrogen ions (Yakusheva, 2010). This suggests that as time increases with the
leaching mechanism, increased amount of hydrogen ions accumulate to decrease pH levels
within solution.
0.02
0.04
0.06
0.08
0.1
0.12
0.14
50 70 90 110 130 150 170 190
Del
ta p
H
Time [min]
62 | P a g e
5.2 Temperature Variable Results
Temperature can heavily effect leaching activity which is shown through the Arrhenius
equation below.
𝑘 = 𝐴𝑒−𝐸𝑎
𝑅𝑇 [4]
The rate constant (k) is effected by temperature (T) shown. This is good indication that the
change in temperature will have a positive or negative impact on the leach recovery. This
claim is supported by Figure 5.2.1 in which both nickel and cobalt show change in liquor
concentration with the change in temperature. Cobalt extraction with temperature shows
logarithmic growth as temperature increases shown in figure 5.2.1, this is good indication that
the rate of leach reaction (k) is increasing with the increasing temperature.
Figure 5.2. 1: Leach temperature vs leach liquor concentration of nickel and cobalt
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.00
2.00
3.00
4.00
5.00
6.00
40 50 60 70 80
Leac
h L
iqu
or
Nic
kel C
on
cen
trat
ion
(m
g/L)
Leac
h L
iqu
or
Co
bal
t C
on
cen
trat
ion
(m
g/L)
Temperature [C°]
Cobalt
Nickel
63 | P a g e
Nickel concentration in leach has only slight increases over 50°C. This is most likely due to the
nickel being the limiting factor in the reaction. If all nickel has been leached into solution at
50°C the concentration will not increase. Changing the solid/liquid ratio could be a mechanism
to increase this nickel concentration. Cobalt loss however could be a factor as the cobalt in
feed material is obviously still able to be leached above the 50-degree temperature. Having a
low concentration of nickel in the feed mass is the reason why low nickel concentrations in
solution are found. Cobalt concentration achieved approximately 5.1 g/L while nickel
concentration achieved approximately 1.5 g/L. Although the leaching mechanism is similar for
both leach reactions, limiting factors are the reason for the difference in trend. In conclusion,
an increased in temperature has a positive impact on the recovery of nickel and cobalt.
5.2.1 Change of pH on Temperature Leach
Effect of temperature on the pH of solution is not as expected. With the increase in hydrogen
ions, pH decreases. This is not evident with Figure 5.2.2 as the decrease in pH is less at 80 °C
than the 60 and 70°C temperature’s respective pH decrease. This suggests that there is an
equilibrium point between 60 – 70°C where dissociation is maximal. Above these
temperatures, hydrogen ions are being drawn from solution suggesting the formation of
precipitation maybe occurring. Although no precipitation was noticeable at 80°C, the
decrease in hydrogen ions in solution suggest a cobalt or nickel complex was most likely
forming.
Figure 5.2. 2: Temperature vs Delta pH
0
0.02
0.04
0.06
0.08
0.1
0.12
40 45 50 55 60 65 70 75 80
Del
ta p
H
Temperature (C)
64 | P a g e
5.3 Acid Concentration Variable Results
Leach liquor concentration of both nickel and cobalt is only slightly effected by the
concentration of sulfuric acid. 1, 2, 4 and 6 M solutions of H2SO4 were made up to identify
the relationship between extraction and sulfuric acid concentration. As shown in Figure 5.3.1,
leach extraction for both elements do not differ greatly over the various concentrations. The
greatest recoveries of both nickel and cobalt were achieved at sulfuric acid concentrations of
4 M. Above 4 M, extraction mechanisms look to diminish as suggested by the 6 M
concentration.
Figure 5.3. 1: H2SO4 Concentration Vs Leach Liquor concentration of nickel and cobalt
By observing Figure 5.3.1, it is quite possible to see that the extraction equilibrium is achieved
between 1 to 6 M. This gives indication that to find the correct acid molarity vs extraction
curve, sulfuric acid concentrations below 1 M would have to be trialed. This is supported by
literature where most extraction change occurs before 1.5 M shown in Figure 5.3.2 (Nayl
2017). Sulfuric acid solutions with a higher concentration than 3.5 M also shows to decline in
extraction for both nickel and cobalt. Concentrations below 1 M could have been trialed
however cathode and separator material was limited.
1.20
1.25
1.30
1.35
1.40
1.45
1.00
2.00
3.00
4.00
5.00
1 2 4 6Le
ach
Liq
uo
r N
icke
l Co
nce
ntr
atio
n (
g/L)
Leac
h L
iqu
or
Co
bal
t C
on
cen
trat
ion
(g/
L)
[H2SO4], M
Cobalt
Nickel
// //
65 | P a g e
Figure 5.3. 2: H2SO4 Concentration Vs Leach Liquor concentration of various elements (Nayl 2017).
5.3.1 Change of pH on Acid Leach
The effect of sulfuric acid concentration on the change of pH is negligible shown in figure
5.3.3. As leach extraction decreases after 4 M, a notable difference in pH increase is recorded.
This is contradictory to what was previously related between extraction and dissolution in
equation [4]. To identify the errors, it would be important to increase the amount of intervals
to display accurate results that are backed through multiple tests.
Figure 5.3. 3: H2SO4 concentration Vs Delta pH
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Leac
hin
g P
erce
nta
ge (
% E
)
[H2SO4], M
Mn
Li
Co
Ni
0.02
0.04
0.06
0.08
0.1
0.12
0.14
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Del
ta p
H
[H2SO4], M
66 | P a g e
5.4 Hydrogen Peroxide Concentration Variable Results
Hydrogen peroxide as an additive does show to effect extraction of both nickel and cobalt
logarithmically. With the trend identified in Figure 5.4.1, both nickel and cobalt increase with
a similar leach rate. Although nickel and cobalt concentration in leach feed are very different,
it is interesting to find that both have the same leach characteristics. These similar leach
characteristics can be an advantage into the identification of a leach process for spent Li-ion
battery cathodes as only a single process needs to be used. If nickel and cobalt were both
leached at different conditions or rates, designing a process would become more complex
and may introduce a higher cost for processing.
Figure 5.4. 1: Hydrogen Peroxide addition % (H2O2) Vs cobalt and nickel concentration in leach liquor
The hydrogen peroxide % that produces the best recovery of both cobalt and nickel was 6 %,
which was the highest test for H2O2. This however does not give clear indication of the optimal
hydrogen peroxide concentration needed to optimise the leach. To find this optimum
hydrogen peroxide to sulphuric acid ratio, a higher test range would need to be completed.
For the given test range, maximum cobalt in solution is approximately 5.1 g/L while nickel in
solution is approximately 1.5 g/L. Increasing the hydrogen peroxide in intervals up to 20 %, a
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0.50
1.50
2.50
3.50
4.50
5.50
0 2 4 6
Leac
h L
iqu
or
Nic
kel C
on
cen
trat
ion
(g/
L
Leac
h L
iqu
or
Co
bal
t C
on
cen
trat
ion
(g/
L)
[H2O2], %
Cobalt
Nickel
67 | P a g e
clear optimised additive content could be deduced. Above this optimised percentage, it would
be realistic to find a decrease in nickel and cobalt recovery due to the acid concentration
decrease.
Figure 5.4. 2: Hydrogen Peroxide Addition Vs Leaching Percentage of various elements (Nayl 2017)
Figure 5.4.2 shows the relationship between peroxide and leaching recovery of various
elements. It shows that at around 4 % hydrogen peroxide, the highest recovery is achieved
and in fact tends to decrease above this concentration of additive (Nayl 2017). This test work
however was conducted with ~ 100 % w/v H2O2 additive whereas 30 % w/v H2O2 solution was
used for the purpose of decreasing costs of the process.
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6
Leac
hin
g P
erce
nta
ge (
%E)
[H2O2], %
Mn
Ni
Co
Li
68 | P a g e
5.4.1 Change of pH on Peroxide Leach
As shown in Figure 5.4.3, the pH is not effected by the addition of H2O2. As multiple peroxide
tests were completed, it is clearly evident that there is no effect on pH. This is an interesting
finding as the change in cobalt and nickel extraction was clearly effected by the addition of
hydrogen peroxide, however no noticeable change in pH was noted with the change in
hydrogen peroxide.
Figure 5.4. 3: H2O2 % Vs Delta pH
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 1 2 3 4 5 6
Del
ta p
H
[H2O2], %
69 | P a g e
5.5 Leach Optimization
Leach optimizations were carried out to achieve maximum recoveries possible with the given
conditions while limiting costs of the process. The leach parameters used were taken from
the maximum recoveries within each leach test and are shown in Table 5.5.1.
Table 5.5. 1: Optimisation parameters for both cathode and separator material
Temperature (°C) Time (min) Solid/Liquid Ratio H2O2 Conc (%) H2SO4 Conc (M)
80 120 50:1 4 M 6 %
Optimization leaches were carried out on both cathode and separator materials. Although
the baseline leaches were completed on the cathode material to find optimization results, it
was important to also test these parameters on the separator material as a high concentration
of targeted metal to be extracted was discovered. If the same parameters could be used for
the extraction of nickel and cobalt on both separator and cathode materials, it would reduce
the cost as both materials could be leached together. Ideally, a concentrated leach feed of
high grade is the best material for leaching hence separating the components of a lithium-ion
battery does provide to produce a higher concentrated feed of nickel and cobalt. Cost factors
however need to be considered as it may be cheaper to leach all of the battery including
anode, casing etc.
The cathode optimization leach was quite successful however results tend to show a large
amount of error. As the cathode composition revealed an average of 238500 ppm cobalt, this
suggests approximately 23.85 % of the 1-gram sample was cobalt. The cobalt extraction in the
cathode optimization leach revealed an optimum of 5 g/L. This suggests that using 1 gram in
54 mL as a reference, 0.27 grams of cobalt was found to be leached into solution. These values
show subsequent error as the recovery of cobalt in the optimization leach is approximately
113.2 %. More cobalt is being extracted from the feed material than the amount of cobalt
that is in the feed material. This error is most likely attributed to the feed characterisation. As
only two tests were assayed on the leach feed material, it may be likely that a higher
concentration Co-Ni leach feed was leached or a lower concentration Co-Ni sample was
assayed.
70 | P a g e
The nickel concentration in solution with the cathode material achieved 0.849 g/L. Again using
1 gram and 54 mL as a reference, 0.0459 grams of nickel was found to have leached. With the
characterisation of the leach feed cathode material, 4.655 % of the material was Ni. This is
clear indication of good leach recovery as 98.6 % recovery was achieved.
Although high recoveries were achieved with the leach optimization, it is important however
to note the decrease in extraction with the optimization parameters. As the optimization was
imposed to find the best possible parameters to achieve the highest nickel and cobalt
recovery, it has not been the case in this instance. A lower cobalt and nickel concentration
was found in both optimization leaches for the cathode material. This is most likely because
even though one parameter may be optimized for leach recovery, it may come into conflict
with the leach mechanism of a different parameter. To overcome this problem, it would be
important to observe all leach conditions at different parameters as adverse or negative leach
reactions can occur. For example, if the extraction is greatest at 2 hours and in a separate test
at 80 °C, it may not necessarily mean the extraction will be the greatest at 2 hours and 80 °C
in the same test.
Table 5.5. 2: Cobalt and nickel recoveries in both cathode and separator materials.
Co Feed [%] Ni Feed [%] Co Opt [g] Ni Opt [g] Co Recovery Ni Recovery
Cathode 23.8500 4.6550 0.2700 0.0459 113.2% 98.6%
Anode 0.0007 0.0001 - - - -
Separator 27.9225 5.6400 0.3060 0.0567 109.6% 100.5%
Table 5.5.2 shows the nickel and cobalt recoveries for the cathode as well as separator. As
indicated, cobalt recovery in the optimization cathode leach is approximately 109.6 % which
is less than the cathode optimization leach. Again these results tend to show high % error and
it supports the argument that the feed mass was not indicative of the overall sample. As both
separator and cathode recoveries are above 100 %, it suggests that the main reason for error
is the non-representative sample. The nickel recovery if compared to the cathode leach is
actually higher, at 100.5 % however this suggests there is some error.
71 | P a g e
These results can be used to conclude that the given parameters achieve better cobalt
recoveries in the cathode material leach while the nickel recovery is increased with the
separator material. It is difficult to draw conclusions with recoveries when the feed sample is
not representative, therefor it is crucial to re-assay the samples and perhaps decrease particle
size for a more representative sample which can be used to find more accurate recoveries.
An interesting point of discussion was the change in pH pre and post leach for both cathode
and separator materials. While the greatest pH change was a 0.13 decrease in the standard
leaches, the optimization leaches shows to have a 0.49 and 0.59 pH drop for the cathode and
separator materials respectively. This suggests that an increase in H+ ions are in solution which
is representative of the reaction taking place. This however is not supported by extraction
results as higher recoveries of both nickel and cobalt took place at different parameters.
72 | P a g e
Chapter 6 – Conclusions and Recommendations
6.1.1 Conclusions
The demand for lithium-ion batteries into the future will continue to rise as technology
advances and the advantages of lithium – ion energy storage systems are needed. To ensure
this demand is supplied, it is crucial to find alternative and more efficient processes to not
only extract lithium-ion battery components from the source (mineral) but also recycling. This
thesis identified the cost drivers surrounding the lithium-ion battery, constructed a formal
method in decreasing the cost drivers through recycling and also presented the results to be
further investigated. As similar investigations and reports have been published into the
recycling of lithium-ion energy storage systems, it is important to further those studies to
produce and make more effective already trialed processes.
The literature review section of this thesis identified that the cost drivers surrounding lithium-
ion batteries were nickel and cobalt metals used in the cathode material. These metals proved
to be the costliest component of the battery and showed that the reduction of these
components would dramatically reduce the overall battery cost. The reduction of this cost
would mean that the battery would be even more viable in the energy storage market than it
already is.
Observing cobalt and nickel reserves, it was evident that there will come a time when a
different energy storage system will have to be commercially available as reserves deplete.
The recycling of the cobalt and nickel within the battery cathode would be a way to decrease
demand on the raw mineral processing which would lead to the reduction in overall process
cost for the lithium-ion battery. Finding an effective recycling process was made easy through
literature and already published methods. The method that provided the highest
concentrations at a relatively low cost was the hydrometallurgical process of leaching through
the use of sulfuric acid (Nayl, 2017).
Through the alteration of certain cost factors in regards to the leach process, the aim was to
increase recovery while decreasing the cost component for the hydrometallurgical process.
73 | P a g e
The parameters that were tested for reduction were time, temperature, sulfuric acid
concentration, hydrogen peroxide concentration and also the battery component material.
This test work differed to other literature in that the leach material that was used was highly
concentrated through the manual breakdown of 20, 18650 – ICR lithium-ion batteries. This
high concentration of both nickel and cobalt in material could be compared to standard
lithium-ion battery recycling techniques which usually consists of lower concentrations due
to the high impurities in the feed. A cost analysis could be completed to find if it is more or
less cost effective to breakdown the battery components and leach the concentrate. This
would depend on recovery and time factors.
It was concluded that although high recoveries were achieved within the leach optimizations
for both nickel and cobalt, the results are inconclusive with the high amount of error.
Achieving recoveries over 100 % brings about speculation in research and is usually accounted
for in accountabilities and repetition in testing. Multiple recommended technical changes can
be made to decrease the error in the results and is discussed in the following section 6.1.2.
6.1.2 Recommendations
To further the investigation into the recycling of lithium ion batteries by a hydrometallurgical
approach, it is important to recommend different aspects of which should be considered.
These aspects from a test-work point of view may make the results more valid or decrease
error within achieved results. Broadening the test work schematic may also lead to the
increase in development into the process and therefore aids in the commercialization of the
leaching of cathodes from spent lithium ion batteries.
Accountability throughout the test work is pivotal into the reliability of data and results. It is
crucial that when performing leach studies, whatever is input into the leach cell is taken out
and tested. This will assure that all mass and compositions have been accounted for which
confirms results and decreases error. As assays are relatively expensive when completed
externally, it was not possible to retrieve all accountability data. This data however would
have been helpful to support presented arguments surrounding compositions and leach
recoveries.
74 | P a g e
Internal characterisation could have been completed on the feed and residue samples. This
characterisation includes Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD).
These machines could have been used to further study the structures and compositions on a
microscopic and angular level. The SEM could have identified new methods into the
processing of the leach feed as microscopic imagery can enhance understanding by showing
certain characteristics about the material that is not seen by the naked eye. XRD could have
been used to identify pre and post leach material compositions which would have supported
arguments made about leaching recovery and efficiency. As the SEM machine was not
operational in the time the test work was being carried out, it was not possible to obtain the
information and imagery.
As shown in Table 3.3.1, the battery cathode cleaning suffers in that not a large amount of
cathode material was recovered. As the cathode material was the subject material to be
leached in the test work, it was disadvantageous to the results as only small leaches could be
carried out. If larger amounts of cathode material were recovered, increased sized leaches
could have been undertaken which would have decreased the amount of error. It was difficult
to draw conclusions between test work battery material compositions and literature battery
compositions as the cathode material was unable to be retrieved. A better cleaning method
that may be able to extract this valuable material is acetic acid usage in ultrasonic baths (Toma
2017).
An increased amount of parameters could have been tested to increase recovery. Such
parameters that could have been tested and measured includes pH change of solution with
the use of NaOH, measurement of Eh, leaching of certain apertures and sizing and also the
different liquid/solid mass ratios. All of these factors most likely would have made a large
difference to the final recovery of the leach and therefore should be investigated to achieve
a worthwhile process. The increase in surface area of a material increases the rate of
dissolution and therefore increases the recovery and rate of leach (Peelman 2016). This
suggests that the use of a mill or pulverizer would decrease the particle sizes and increase the
surface area for leaching, thus increasing extraction.
Increasing the peroxide concentration range will most likely also increase the extraction of
nickel and cobalt. As shown in Figure 5.4.1, extraction shows logarithmic increase and is most
likely to increase even past 6 %.
75 | P a g e
Increasing the amount of feed characterisation assays would have been helpful in the
composition make up of feed material. Decreasing the error is a critical to achieve credible
results. As displayed in the optimization section of this thesis, it is evident that there is error
within the leach feed compositions. If this feed material was averaged over an extended
amount of assays as well as large sample sizes, the composition data would have minimal
error. Further homogenization of the feed material would also achieve credibility towards
accuracy and data reliability.
A drop in pH was unexpectedly recorded for all tests. This was most likely due to the excess
acid converting to H+ ions. As the liquid/solid mass ratio was approximately 50:1, the reaction
allowed for the sulfuric acid to be in excess. Test work allowed for such high doses of sulfuric
acid as the liquid/solid mass ratio was approximately 10:1. This would have made a large
difference on the acid usage and allowed for H+ ions to be drawn from solution hence
increasing pH. A free acid test could have been used to identify this excess usage of acid
however time was a constraint. As the material used for the leaches was manually taken from
spent lithium ion batteries, the material usage was also a limiting constraint that hindered pH
results and correct parameters.
76 | P a g e
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