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Commercialization of Silicon Anodes for Electric Vehicle Applications
J. Kaiser*, V. Chevrier, E. Figgemeier, K. Eberman,
3M
AABC Europe
Mainz, 31/1/2017
2. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Why silicon anodes?
Stack 1C || NMC:833 Wh/L
303 Wh/kg
Graphite
Collector
Graphite
Separator
NMC 622
Collector
NMC 622
Separator
Stack 2.1 Si || NMC:1138 Wh/L379 Wh/kg
Silicon
Collector
Silicon
Separator
NMC 622
Collector
NMC 622
Separator
Stack 2.2Si || NMC:
1308 Wh/L438 Wh/kg
Silicon
Collector
Silicon
Separator
NMC 622
Collector
NMC 622
Separator
3. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Stability of silicon anodes
• Nano-Si in inactive matrix
• Active/inactive domains < 15nm
• High first cycle efficiency
• Remains amorphous on cycling
• Minimizes surface area
• Dilutes volume expansion
• Scalable alloying processChevrier et al., IMLB 2016
4. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Irreversible losses and phase change
Chevrier et al., JES 161 A783 (2014)
Cycle #1 – #10, Cha C/4 (5 mV, C/40), Dch C/4 (0,9V)
Si- alloy V6
Nano Si
Cycle (a) #20 – #50, (b) #2 - #50Cha C/4 (5 mV, C/40), Dch C/4 (0,9V)
Nano Si
Si- alloy V6Si- alloy V6
Nano Si
5. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Realistic energy densities
Compare with:
300
305
310
315
320
325
330
335
340
0% 20% 40% 60%
Sta
ck
Wh
/kg
3M Si Alloy (wt%)
832
833
834
835
836
837
838
839
0% 20% 40% 60%
Sta
ck
Wh
/L
3M Si Alloy (wt%)
C || NMC 303 Wh/kg 833 Wh/L
Si (100%) || NMC 379 Wh/kg 1138 Wh/L
6. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Impact of electrolyteElectrode morphology after 100 cycles @ 0,5C / 0,5C
Chevrier et al., IMLB 2016
7. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Impact of electrolyteCycle life test @ 0.5C / 0.5C
wt%
EC DMC EMC DEC FEC PC X
Variation 1 28% 65% 5% 2%
Variation 2 28% 65% 5% 2%
Variation 3 28% 65% 5% 2%
Variation 4 25% 58% 5% 10% 2%
Variation 5 23% 55% 20% 2%
Chevrier et al., IMLB 2016
Graphite/Si-alloy anode, LCO cathode; 0,5C/0,5C, 2,75V – 4,35V CCCV (cut-off @C/20)
8. All Rights Reserved.29 January 2017© 3M 3M Confidential.
FEC related gasing at elevated temperaturesCycle test at 45°C
CMC/SBR binder45°C, 2.75V-4.35V
unclampedC/10
C/5C/2 C/20
C
9. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Prelithiation makes high percentages of Si practical
• 3M is collaborating with Nanoscale Components, Inc..
• Nanoscale uses breakthrough Lithium metal free process
• Industrial scale roll-to-roll process
• Full compensation for irreversible losses
• Increases cycle life
Nanoscale’s
Process Reason
Safer
manufacturing
No lithium metal is used, eliminating a key fire risk
Safer cells No lithium metal is in cells, eliminating tendency to form
dendrites
Better uniformity Electrochemical method offers more control than powder
dispersion
Reduced swelling Partial expansion occurs during pre-lithiation, before cell
assembly
Reduced gassing SEI is partially formed during pre-lithiation; less occurs in
formation
Less expensive Lithium salt used is much less expensive than metal
10. All Rights Reserved.29 January 2017© 3M 3M Confidential.
~500 full cycles with prelithiated anode( 55%wt. Si-alloy, 100% DOD, @ 0.5C / 0.5C )
• Higher energy density for prelithiated cell
• Massively improved cycle life
• Linear capacity fade
• Improved coulombic efficiency suppressed
parasitic side reactions
11. All Rights Reserved.29 January 2017© 3M 3M Confidential.
Summary
• Phase change and mechanical stress in pure Si particles are root causes of pure Si degradation.
• Design of material and microstructure is necessary to mitigates these effects, but comes at the
cost of smaller energy density gains compared to pure Si.
• Electrolyte composition has strong impact on cycle life.
• Prelithiation reduces undesired side reactions and massively improves cycles life.
~500 cycles with with prelithiated 55% Si-alloy anode achieved in full cell.
Please send product inquiries to [email protected] or [email protected]
Thank you.
