understanding lithium-ion technology · 2019. 6. 11. · systems with sloping soc vs. voltage curve...
TRANSCRIPT
Understanding Lithium-Ion Technology
Jim McDowall (updated from Battcon 2008)
PE/SB Winter Meeting 2015, New Orleans
Background
2
History
Started with primary batteries with metallic lithium negatives
True lithium ion – Sony paper in 1990
Large-scale shipments in 1993
First mass-produced auto (Mercedes S400 mild hybrid) in 2008
Widespread deployments for grid-connected energy storage since ~2010
Issues
Safety
Safety
Safety
PE/SB WM2015 - Understanding Lithium Ion Technology
Reaction mechanism
3
Lithium Ion
Metal Ion
Carbon
Oxygen
Separator
POSITIVE NEGATIVE
SEI
e–
Charge
Charge
Discharge
Discharge
e–
PE/SB WM2015 - Understanding Lithium Ion Technology
Current chemistries
PE/SB WM2015 - Understanding Lithium Ion Technology 4
Positive (cathode)
LiCoO2 (LCO)
LiNiCoAlO2 (NCA)
LiNiMnCoO2 (NMC)
LiMn2O4 (LMO)
LiFePO4 (LFP)
Negative (anode)
Graphite (C)
Lithium titanate (LTO)
195 Ah/kg145 Ah/kg
125 Ah/kg
162 Ah/kg
3,00
3,20
3,40
3,60
3,80
4,00
4,20
4,40
0,00 50,00 100,00 150,00 200,00 250,00
CAPACITY (Ah/kg)
VO
LT
AG
E (V
)
LiNiO2
LiCoO2
LiMn2O4
LiFePO4
0
0.5
1
1.5
2
0 50 100 150 200 250 300 350 400
ESLS30 AD003 (6.5 m2/g)
EC/DMC/EA (15/25/60)
LiPF6 1,5M + 4.75% VC
20 mA/g at 60°C
Vo
lts
/Li
Capacity (mAh/g)
60°C
353 mAh/g
39
Graphite
Technologies
5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Vo
ltag
e v
s.
Li
meta
l
LCO / C
3.8 V NCA / C
3.6 V
LMO / C
3.7 V
LFP / C
3.2 V
LCO / LTO
2.5 V
Voltage indicates approximate mid-point value
LFP / LTO
1.9 V
PE/SB WM2015 - Understanding Lithium Ion Technology
Future developments
PE/SB WM2015 - Understanding Lithium Ion Technology 6
Avicenne Energy - 30th INTERNATIONNAL BATTERY SEMINAR & EXHIBIT, March 11, 2013
Construction
7
Lithium-ion cells
Cylindrical
Prismatic
Lithium-ion polymer
‘Pouch cells’
Lithium metal polymer
Metallic lithium negative
No liquid electrolyte
PE/SB WM2015 - Understanding Lithium Ion Technology
Safety discussion
8
Will be covered in next presentation…
PE/SB WM2015 - Understanding Lithium Ion Technology
Calendar aging
9
Fundamental difference between systems
Aging in aqueous systems driven by reaction kinetics
Aging in Li-ion driven by thermodynamic stability
Rate of aging influenced strongly by both temperature and operating voltage
Typically linear capacity fading to 60% or 70% SOH
Aging factor?
PE/SB WM2015 - Understanding Lithium Ion Technology
Calendar aging – negative electrode
10
Gradual ‘leakage’ of lithium ions through SEI
Metallic ions dissolved from positive provide conduit
Emerging lithium ions react with solvents in electrolyte
Increase in SEI thickness and impedance
Some metals are more soluble than others
LMO has relatively high solubility = more rapid capacity fading
Some LFP products have solubility issues above 40°C to 45°C
Loss of lithium ions (‘fuel’)
Temperature-dependent
PE/SB WM2015 - Understanding Lithium Ion Technology
Calendar aging – positive electrode
11
Primary aging process is oxidation reactions with electrolyte
Affects intercalation ability
Impedance increase
NCA has slowest rate of aging
Dependent on temperature AND voltage
PE/SB WM2015 - Understanding Lithium Ion Technology
Cycling aging
12
Frequency and depth of discharge
Influence of charge rate
High temperature can reduce cycling aging
PE/SB WM2015 - Understanding Lithium Ion Technology
Pros and cons of ‘slope’
13
Lithium batteries must use electronics for balancing
Systems with sloping SOC vs. voltage curve are easy to balance
BUT non-ideal charging can impact SOC in service
Charge voltage
14-cell NCA battery requires 56.0 V for 100% SOC
Charging at 54.5 V gives ~90% SOC
Temperature compensation can be a problem!
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
0 10 20 30 40 50 60 70 80 90 100
Vo
ltag
e (V
)
State of charge (%)
LCO
NCA
PE/SB WM2015 - Understanding Lithium Ion Technology
Pros and cons of ‘slope’ (cont.)
14
Technologies with no slope are good for constant-power discharges
Lack of slope poses problems in balancing
Potential problems for long-term operation at intermediate SOC
Steep rise at end of charge requires aggressive balancing or alternative approach
Charging - LiFePO4
PE/SB WM2015 - Understanding Lithium Ion Technology
Summary
15
Broad family of lithium-ion electrochemistries
Different cell formats and system architectures
Should not be promoted – or accepted – in the same way as traditional batteries
PE/SB WM2015 - Understanding Lithium Ion Technology
Further reading
16
Battcon 2010: Sophistication Versus Simplicity – System Design Considerations for Li-Ion Batteries
PE/SB WM2015 - Understanding Lithium Ion Technology