Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS...

34
2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical cells & ion transport - electrochemical potential - half-cell reactions Lithium Ion Batteries (LiBs) - battery materials - application of batteries - “post-LiBs” Fuel Cell Basics & Applications - fuel cell types and materials - basic electrocatalysis - H 2 reduction & O 2 reduction kinetics - transport resistances - cell-reversal & start-stop degradation

Transcript of Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS...

Page 1: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30

Electrochemistry Basics

- electrochemical cells & ion transport

- electrochemical potential

- half-cell reactions

Lithium Ion Batteries (LiBs)

- battery materials

- application of batteries

- “post-LiBs”

Fuel Cell Basics & Applications

- fuel cell types and materials

- basic electrocatalysis

- H2 reduction & O2 reduction kinetics

- transport resistances

- cell-reversal & start-stop degradation

Page 2: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 31

Lithium Ion Batteries (LiBs) - Solvents

use of (metallic) lithium electrodes requires aprotic organic electrolytes

potential) reduction standard-1( V045.3E;eLiLi 0

)Li/Li(

V0E;H5.0eH 0

)2H/H(2

V045.3E;H5.0LiHLi 0

)2H/H(2

Li unstable with H+ (and H2O)

aprotic organic solvents

from: K. Xu; Chem. Rev. 104 (2004) 4303

Page 3: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 32

Lithium Ion Batteries - Solvents

from: K. Xu; Chem. Rev. 104 (2004) 4303

requirements: - high dielectric constant (e)

- low viscosity (h)

- low melting point (Tm), high boiling point (Tb), high flash point (Tf)

propylene carbonate (PC) seems almost perfect (1958: first Li-plating from PC)

Page 4: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 33

Lithium Ion Batteries - Salts

from: K. Xu; Chem. Rev. 104 (2004) 4303

requirements: - complete dissociation high conductivity (s)

- oxidative/reductive stability

- thermal stability (high Tdecomposition)

- chemical stability towards all cell components (e.g., Al current collector)

lithium salts soluble in aprotic electrolytes aprotic organic electrolytes

Page 5: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 34

Positive Electrodes for LiBs TiS2 : first reversible Li+ intercalation compound (Whittingham, 1973)

1)-0 x withinphase (single TiSLiTiSexLix 2x2

- TiS2 sheets

- hexagonal close-packed S-lattice

- S stacking sequence ABABAB

from: M.S. Whittingham; Chem. Rev. 104 (2004) 4271

specific capacity theoretical capacity normalized by weight (referenced to lithiated/de-lithiated compound for positive/negative electrode)

22

2

LiTiSLiTiS

s

LiTiSg

mAh225

g

As811

molg119

molAs96485C

specific energy: )Li/Li.vs(LiTiS

s

LiTiSLiTiS

s

LiTiS E]g/mWh[C]g/mWh[W2222

Page 6: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 35

Li / TiS2 Battery

Li // 2.5M LiClO4 in DL // TiS2 at 10 mA/cm2 (25C) from: M.S. Whittingham; Chem. Rev. 104 (2004) 4271 (M.S. Whittingham; Prog. Solid State Chem. 12 (1978) 41; 790 cits.)

from: M.S. Whittingham; Chem. Rev. 104 (2004) 4271

V0.2E)Li/Li.vs(

22 LiTiS

s

LiTiS g/mWh450W

note: dioxolane was used, since PC

co-intercalated with Li+ into TiS2

first large automotive LiB in 1977

using LiAl-alloy negative electrode (0.2 V vs. Li/Li+; used for safety reasons)

Page 7: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 36

Li Metal Negative Electrode

highest specific capacity (3800 mAh/gLi )

but, formation of dendrites (safety!)

& shape-change (loss of active material)

from: K. Xu; Chem. Rev. 104 (2004) 4303

in addition:

continuous reduction of electrolyte

no lithium-metal electrodes in

today’s rechargeable LiBs

Page 8: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 37

LiC6 Negative Electrode (Sony 1990)

Li+ insertion in between graphene planes of graphite up to 1 Li+ per 6 C

6LiCC6exLi

C

s

Cg

mAh372

molg72

molAs96485C , with

ELixC vs. Li+/Li

no Li-plating (ELixC > ELi )

no shape-change (fixed C-”cage”)

but, …

from: R.A. Huggins; Advanced Batteries (Springer, 2009)

Page 9: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 38

Solid Electrolyte Interface (SEI)

SEI: electrolyte reduction products on LixC or Li (fluorides from LiBF4 or LiPF6)

Li+-conducting, but

electronically insulating (20 Å)

prevents continuous electrolyte reduction

Li+ consumed for initial SEI formation

(batteries must be built with excess Li+)

but, …

from: K. Xu; Chem. Rev. 104 (2004) 4303

Page 10: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 39

Graphite Electrode Defoliation

strong solvation of Li+ with PC intercalation of PC into graphite

from: K. Xu; Chem. Rev. 104 (2004) 4303

prevents formation of stable SEI w. PC

EC, however, forms stable SEI

need to add DMC, DEC, or EMC

to increase conductivity at 25C

stable negative graphite electrode

lithium must be introduced via

the positive electrode materials

(does not work, e.g., with TiS2)

Page 11: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 40

Positive Intercalation Electrode with Li

discovery of LiCoO2 (layer compound) in 1980:

0.55 Li+ + 0.55 e– + Li0.45CoO2 LiCoO2

2

2

LiCoO

s

LiCoOg

mAh150

molg98

molAs9648555.0C

reversible inter-/deintercalation of Li+

between LiCoO2 and Li0.45CoO2

graphite // alkylcarbonates + LiPF6 // LiCoO2 developed by Sony in 1990

is the currently predominant LiB system

from: R.A. Huggins; Advanced Batteries (Springer, 2009)

Page 12: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 41

LiB – Summary

from: B. Dunn, H. Kamath, J.M. Tarascon; Science 334 (2011) 928

Page 13: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 42

Electrolyte Filled Separator

from: P. Arora & . Zhang; Chem. Rev. 104 (2004) 44193

porous polymer matrix: electrolyte reservoir

& electronic insulation

5.1

eelectrolyteelectrolyt

separator

areal

tR

es

estimated ionic resistance:

Page 14: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 43

Battery Assembly

from: P. Arora & . Zhang; Chem. Rev. 104 (2004) 44193

spiral-wound cylindrical design (for high energy batteries: pouch or prismatic cells)

note: commonly the negative electrode is referred to as anode and the positive

electrode as cathode (based on the discharge reaction)

typical dimensions:

- negative current collector (Cu): 10 mm

- positive current collector (Al): 20 mm

- separator: 25 mm

- separator: 25 mm

- electrodes: - high power 20-40 mm

- high energy 60-100 mm

for high energy LiBs:

2.5 mAh/cm2 4V 10 mWh/cm2

huge area for electric vehicle batteries!

Page 15: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 44

Ragone Plots

celates specific energy to specific power (rate)

C-rate is defined as specific power/specific energy [1/h]

from: B. Dunn, H. Kamath, J.M. Tarascon; Science 334 (2011) 928

Page 16: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 45

Electrochemistry Basics

- electrochemical cells & ion transport

- electrochemical potential

- half-cell reactions

Lithium Ion Batteries (LiBs)

- battery materials

- application of batteries

- “post-LiBs”

Fuel Cell Basics & Applications

- fuel cell types and materials

- basic electrocatalysis

- H2 reduction & O2 reduction kinetics

- transport resistances

- cell-reversal & start-stop degradation

Page 17: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 46

battery system weight & cost:

120 Whname-plate/kgsystem (Tesla) highest Wh/kg battery pack, but very complex system

400 km range (53 kWhname-plate): 450 kg and 13000 € (2030 projection*) )

charging time: hour(s)

Tesla EV (2009)

Electromobility Challenges: BEVs

safety:

short-term: higher Wh/kg electrode materials and/or high-cost system architecture

long-term: novel electrode and electrolyte materials

*) “Transitions to Alternative Transportation Technologies – Plug-In Hybrid Electric Vehicles”,

National Research Council (2010); see: www.nap.edu/catalog/12826.html

safer and higher Wh/kg batteries are required for full BEVs

Page 18: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 47

Battery Materials/Concepts

Li/air

Li/sulfur

silcon

LiNiPO4

LiCoPO4modified from: J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

LiNiPO4

LiCoPO4modified from: J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

an

od

es (

neg

ati

ve)

ca

tho

de

s (

po

sit

ive

)

Page 19: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 48

Li/air

Li/sulfur

silcon

LiNiPO4

LiCoPO4modified from: J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

LiNiPO4

LiCoPO4modified from: J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

higher Wh/kg: - 5V cathodes (Co,Mn,Fe-phosphoolivines, Mn-spinels) 25% gain

- higher specific capacity materials

“post-LiB”: Li/air and Li/S batteries with Si-based anodes

Battery Specific Energy [Wh/kgelectrodes ]

Page 20: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 49

Battery Materials anodes:

cathodes:

from: Lamm, A.; Warthmann, W.; Soczka-Guth, T.; Kaufmann, R.; Spier, B.; Friebe, P.; Stuis, H.; Mohrdieck;

“Lithium-Ionen Batterie – Erster Serieneinsatz im S400 Hybrid“; ATZ (07-0812009) 2009, 111, 490.

durability, safety, and cost are additional critical considerations

Page 21: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 50

Limit of Lithium-Ion Batteries

specific of cells and battery-packs:

- electrodes: 70% of cell weight

(rest: current collectors & electrolyte)

LiNixMnyCozO2 / C: 300 Wh/kgcell

from: F.T. Wagner, B. Lakshmanan,

M.F. Mathias; J. Phys. Chem.

Lett. 1 (2010) 2204

long-term projection:

200 Wh/kgbattery-pack

(from F.T. Wagner et al.)

LiNixMnyCozO2 / C

specific capacity of electrodes [Ah/kgelectrodes]: 110

cathode voltage (positive) [V] 4.0

anode voltage (negative) [V] 0.1

battery voltage [V] 3.9

specific energy of electrodes [Wh/kgelectrodes]: 430

spec. energy of C-anodes & NMC-cathodes:

)CC(

CCC

ss

sss

where

Page 22: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 51

BEV Battery Weight & Cost

projected performance of today’s LiB technology: - 200 Wh/kgbattery-pack*)

- 95% discharge efficiency

- 80% state-of-charge range

- 250 €/kWhname-plate**)

**) “Transitions to Alternative Transportation Technologies – Plug-In Hybrid Electric Vehicles”,

National Research Council (2010); see: www.nap.edu/catalog/12826.html

*) F.T. Wagner, B. Lakshmanan, M.F. Mathias; J. Phys. Chem. Lett. 1 (2010) 2204

energy required for small 4-passenger car: - 100 Wh/km*)

150 km range 500 km range

required net energy: 15 kWhnet 50 kWhnet

required name-plate energy: 20 kWhname-plate 66 kWhname-plate

battery weight: 100 kg 330 kg

battery cost: 5000 € 16500 €

current cost & weight 2-fold higher

fast charging increases perceived range

Page 23: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 52

Rapid Charging

charging time vs. power: kWhelectricity / kWcharging = tcharging

from:

E.ON presentation

at the IAS Opening

by J. Eckstein

(Oct. 22, 2010)

rapid charging: impacts battery life & business case of electric utilities

long-range BEVs need advanced batteries

Page 24: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 53

Battery Targets for 500 km BEVs

battery requiriements for 500 km-range small 4-passenger cars:

- 70 kWhname-plate < 200 kg weight > 350 Wh/kgbattery-pack

- 35 kW constant power C-rate of 0.5 h-1 (continuous)

- 100 kW accelerating power C-rate of 1.5 h-1 (short-term)

- 25000 km life (50% avg. charge) > 1000 cycles

- <10000 € battery cost < 150 €/kWhname-plate (15 €/m2cell !)

current LiB technology will not meet the long-range Wh/kg requirements

Wh/l of concern for current car architectures:

380 kg / 500 l (ICE) 430 kg / 350 l (20kWh BEV)

alternative batteries – “post-LiBs” ?

Page 25: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 54

Electrochemistry Basics

- electrochemical cells & ion transport

- electrochemical potential

- half-cell reactions

Lithium Ion Batteries (LiBs)

- battery materials

- application of batteries

- “post-LiBs”

Fuel Cell Basics & Applications

- fuel cell types and materials

- basic electrocatalysis

- H2 reduction & O2 reduction kinetics

- transport resistances

- cell-reversal & start-stop degradation

Page 26: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 55

Li-S Batteries

challenges & development needs:

- polysulfide diffusion to anode Li+-conducting diffusion-barrier

- poor C-rate & cathode “clogging” cathode design

- stable anode configuration improved Li-metal anode design or alternative

Li2S2/Li2S

Li+

e-

Li2S4

e-

Li+

Li2S8

S8

e-

Li + e-

Li2S4

Li2S2

& Li2S

sulfur-electrode (e.g., porous carbon)Li-electrode

sep

ara

torpoly-sulfide redox-shuttle

Li2S6

e-

Li+Li+Li+

cu

rren

t-co

llecto

r

+

cu

rren

t-co

llecto

r

Li2S2/Li2S

Li+

e-

Li2S4

e-

Li+

Li2S8

S8

e-

Li + e-

Li2S4

Li2S2

& Li2S

sulfur-electrode (e.g., porous carbon)Li-electrode

sep

ara

torpoly-sulfide redox-shuttle

Li2S6

e-

Li+Li+Li+

cu

rren

t-co

llecto

rcu

rren

t-co

llecto

rcu

rren

t-co

llecto

r

+

cu

rren

t-co

llecto

r

++

cu

rren

t-co

llecto

r

2 Li + S (Li2S)solid ; E0 2.0 VLi

2 Li 2 Li+ + 2 e-

S + 2 Li+ + 2 e- (Li2S)solid

Page 27: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 56

Li-S Batteries: State-of-the-Art

further advances needed, also wrt. Li-metal safety

increased cycle-life with poly-sulfide diffusion barriers

Cathode / Electrolyte / Anode S-Utilization C-Rate Cycles Ref.

C+S / liquid electrolyte / Li 70% 0.10 h-1

20 [1]

C+S / liquid+solid-electrolyte/ Li 70% 0.20 h-1

150 [2]

C+S / polymer electrolyte / Li 70-50% 0.20 h-1

200 [3]

C+Li2S / liquid electrolyte / Si 40% 0.13 h-1

20 [4]

C+Li2S / polymer electrolyte / Sn 40% 0.20 h-1

100 [5]

[1] X. Ji, K.T. Lee, L.F. Nazar; Nature Materials 8 (2009) 500.

[2] SION Power presentation; ORNL Symposium on Scalable Energy Storage Beyond Li-Ion:

Materials Perspective (Oct. .2010)

https://www.ornl.gov/ccsd_registrations/battery/presentations/Session7-1020-Affinito.pdf.

[3] G. Ivanov (Oxis Energy Ltd.); (Jan. 2010); Oxis web site:

http://www.oxisenergy.com/downloads/Recent%20progress%20Polymer%20Li-S_2010.pdf;

[4] J. Li, R.B. Lewis, J.R. Dahn; Electrochem. & Solid-State Lett. 10 (2007) A17.

[5] H.S. Ryu, Z. Guo, H.J. Ahn, G.B. Cho, H. Liu; J. Power Sources 189 (2009) 1179.

still insufficient performance: - S-utilization 70% vs. 90% target

- C-rate 0.2 h-1 vs. 0.5 h-1 target

- cycle-life 200 cycles vs. 2000 cycle target

Page 28: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 57

Li-S Batteries: Metallic Li-Anodes

supression of Li dendrite formation / shape-change is challenging

alternative anode concepts ?

Page 29: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 58

0

100

200

300

400

500

600

700

800

900

0 500 1000 1500 2000 2500 3000 3500

specific capacity of negative electrode [Ah/kg]

sp

ec. cap

acit

y o

f ele

ctr

od

es [

Ah

/kg

]Anode Effect on Wh/kg

)(

CC

CCCelectrodes

high capacity anodes essential for Li-S & Li-air batteries

Si-anodes (Li15Si4): volumetric expansion (4x) is challenging

Si-anode

Li-anode

C-anode

Page 30: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 59

Wh/kg of LiB vs. Li/S

spec. capacity & energy projections:

2x Wh/kgbattery-pack gains projected for Li-S

J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

LiNixMnyCozO2 / C Li2S / Si Li2O / Si

specific capacity of electrodes [Ah/kgelectrodes]: 110 630 800

cathode voltage (positive) [V] 4.0 2.0 2.7

anode voltage (negative) [V] 0.1 0.5 0.5

battery voltage [V] 3.9 1.5 2.2

specific energy of electrodes [Wh/kgelectrodes] 430 950 1,700

gain vs. current batteries 2-fold 4-fold

Page 31: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 60

Li-Air Batteries: Thermodynamics

2 Li + O2 (Li2O2)solid ; E0 = 2.96 VLi1)

2 Li 2 Li+ + 2 e-

O2 + 2 Li+ + 2 e- (Li2O2)solid

4 Li + O2 (Li2O)solid ; E0 = 2.91

VLi1)

4 Li 4 Li+ + 4 e-

O2 + 4 Li+ + 4 e- (Li2O)solid

Li2O2 observed by ex-situ Raman2,3)

partial Li2O formation via O2 balance4)

1) M.W. Chase; NIST-JANAF Thermochemical Tables 4th Ed. (1998) 2) K.M. Abraham, Z. Jiang; J. Electrochem. Soc. 143 (1996) 1

4) J. Read; J. Electrochem. Soc. 149 (2002) A1190

O2

O2

Limetal

O2

O2

Limetal

5) L. Andrews, R. Smardzew; J. Chem. Phys. 58 (1973) 2258

3) A. Débart, A.J. Paterson, J. Bao, P.G. Bruce; Angew. Chem. Int. Ed. 47 (2008) 4521

evidence for Li2O2 & Li2O in organic electrolytes

bulk-LiO2 only stable at 15 K5), but [LiO2]solvated in organic electrolytes

Page 32: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 61

Li-Air Batteries: Processes

Li2O2 / Li2O

e-

e-

Li

Li-electrode

[ LiO2 ]solv.

Li+

cu

rren

t-co

llecto

r

+

O2 (air)

( H2O, CO2 )LixO2

Li2CO3

LiOH

e-

c c c

cccc

+

porous air-electrodee- +

sep

ara

tor

Li2O2 / Li2O

e-

e-

Li

Li-electrode

[ LiO2 ]solv.

Li+

cu

rren

t-co

llecto

rcu

rren

t-co

llecto

rcu

rren

t-co

llecto

r

++

O2 (air)

( H2O, CO2 )LixO2

Li2CO3

LiOH

e-

c c c

cccc

++

porous air-electrodee- ++

sep

ara

tor

challenges:

- solid Li2O2/Li2O can clog electrodes and limit O2 & Li+ mass-transport

- O2, H2O, & CO2 can react on the lithium anode

Page 33: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 62

Challenges for Li/Air Batteries

slow reaction rates at the air-cathode

low round-trip efficiency ( 70%)

low rate capability (C-rate 0.1 h-1)

insufficient cycle-life (<50 cycles)

reaction of O2 with carbonate-based electrolytes

Li-metal electrode (dendrites, shape-change, corrosion)

open-system due to air-feed

contamination/degradation from H2O-vapor & CO2

electrolyte evaporation

low volumetric energy density (air-feed channels)

improved catalysts, electrodes, electrolytes, & Li+-ion selective separators

high-risk / high-gain technology

fun

da

men

tals

en

gin

ee

rin

gfu

nd

am

en

tals

en

gin

ee

rin

g

(electro)catalysis,

electrode design

Page 34: Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS Battery & FC Lectures - Battery (Michele P. for Hubert G.).ppt p. 30 Electrochemistry Basics - electrochemical

2012-01-31 AMS Battery & FC Lectures – Fuel Cell - 1 (Hubert G.).ppt p. 63

Wh/kg of LiB, Li/S, & Li/Air Electrodes

spec. capacity & energy projections:

large Wh/kgbattery-pack gains projected for Li-S (2x) and Li-air (3x)

J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

J.-M. Tarascon & M. Armand,

Nature 414 (2001) 359

Li/air

Li/sulfur

silcon

LiNixMnyCozO2 / C Li2S / Si Li2O / Si

specific capacity of electrodes [Ah/kgelectrodes]: 110 630 800

cathode voltage (positive) [V] 4.0 2.0 2.7

anode voltage (negative) [V] 0.1 0.5 0.5

battery voltage [V] 3.9 1.5 2.2

specific energy of electrodes [Wh/kgelectrodes] 430 950 1,700

gain vs. current batteries 2-fold 4-fold