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Transcript of Electrochemistry Basics - Technische Universität Mü · PDF file2012-05-22 AMS...
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
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
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)
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
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
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)
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
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)
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
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)
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)
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
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:
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!
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
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
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
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
)
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 ]
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
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
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
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
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” ?
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
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
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
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 ?
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
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
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
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
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
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