Advanced Thermal Modeling of Batteries
CBD Battery Design LLC
Battery Design Studio
Update March 20, 2012 13:30 – 13:55
New Features Covered Today
• 3D models
• Voltage dependent diffusion
Let’s start with brief introduction to Battery Design Studio®
Battery Design LLC CBD
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Battery Design Studio®
A user-friendly interface between battery designers and users for costing, sizing, and correlation of test data to performance, safety, and life predictions.
Development started APR1999 interface
Input Model Output
Size
Cost
Power
Impedance
Life
Abuse, etc Data
Lab
User
Battery Design LLC CBD Standardized software promotes
(enables) communication
Models Input
Output Materials Supplier
Input
Output
Battery Developer
Exchange of battery information.
Modeler
Input Output Input Output
Modeler
CBD
Battery Design Studio®
Formulations Cell Design Test conditions
Standardization lowers cost, allows faster product introduction.
Battery Design LLC CBD
BDS Cell Design Process
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Physical Cell Description
• Coin, cylindrical pouch, prismatic
•Gives size, weight, equilibrium voltage, capacity, bill of materials, etc.
Fit Model Parameters
• circuit, physics
• Allows simulation of performance
Use and/or Distribute
Text Battery Model (TBM)
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TBM files bridge the
supply chain of batteries
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•Button cell
•Formulations
•Test results
Materials Developer (cathode, anode,
separator, electrolyte, etc.)
•Model selection
•Electrodes, incl. tabbing
•Separator
•Cylindrical, prismatic, pouch
Cell Designer •Performance estimation
•Model selection
•Series/Parallel cells
•Cooling
End User, Module and/or Pack Developer
TBM file, prg, out
TBM file
STAR-CCM+
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3D MODEL THEORY
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Unit Cell Concept
Material between current collectors represented as unit cell.
Collectors modeled as resistors connecting unit cells.
Negative current collector
Positive current collector
Unit Cell
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Battery Design LLC CBD Selected Simulation Models in
Battery Design Studio ®
2654
3
3
2
210
DODaDODaaY
DODaDODaDODaaU
UVVYJ np
(1) J. Newman and W. Tiedemann, J. Electrochem.
Soc. Vol. 140, No. 7, July 1993 pp. 1961-1968.
(2) H. Gu, J. Electrochem. Soc., Vol. 130 No. 7
1983 pp. 1459-1464.
(3) U. S. Kim, Ch.B. Shin, C.-S. Kim, J. Power Src.
189 (2009) 841-846
(1) T. Fuller, M. Doyle, J. Newman, J.
Electrochem. Soc. 141 (1994) 1-10
(2) Battery Design LLC, “BDS
Documentation”
M. Verbrugge and R. Conell, J.
Electrochem. Soc. 149 (2002) A45-A53
Cell Design
DISTNP
HEV/PHEV Module/Pack
RCR
EV Module/Pack
NTG
Solves transport, kinetics, equations
Quick response for frequent charge/ discharge like HEV/PHEV energy storage
Simple, easy to create model , and best for simple discharging thermal analysis
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3D CELL DESIGNS
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Stacked Plate Design
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Battery Design LLC CBD
Stacked Plate Design
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Battery Design LLC CBD
Spirally Wound Design
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Battery Design LLC CBD
18650 – LoY, Pos Plate
Voltage
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Battery Design LLC CBD
18650 – LoY, Pos Inner
Current Density
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Battery Design LLC CBD
18650 – LoY, Outer Current
Density
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Battery Design LLC CBD
18650 – LoY, Neg Plate
Voltage
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Battery Design LLC CBD
18650 – LoY, Neg Plate Iin
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Battery Design LLC CBD
18650 – LoY, Neg Plate Iout
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CONCENTRATION-DEPENDENT DIFFUSION COEFFICIENTS
Concentration-dependent diffusion coefficients
• Solid-phase diffusion coefficients are known to depend on concentration.
• Theory shows that diffusion coefficient depends on derivative of equilibrium potential (E) with respect to lithium fraction (x).
Concentration dependence of lithium diffusion coefficient in LiCoO2, Young-Il Jang, Bernd J. Neudecker, and Nancy J. Dudney, Electrochemical and Solid-State Letters, 4 (6) A74-A77 (2001)
dx
dE
RT
FxD
xd
adDD LiLiLi
ln
ln~
• Correction can be significant.
• BDS accounts for this correction.
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Accounting for concentration dependence of solid-phase diffusion coefficients in BDS (1)
Use “Monotonic cubic” mode for interpolation of voltage data.
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Accounting for concentration dependence of solid-phase diffusion coefficients in BDS (2)
Just check option for “Diffusion Conc. Correction”
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Example: NCM/Graphite Cell
NCM Equilibrium Curve Graphite Equilibrium Curve
dx
dE
E
x
x Cathode material shows significant effect of voltage on solid-phase diffusion coefficient.
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Simulation Results: Discharge Curves
Effect of variability in solid-phase diffusion coefficient becomes more significant at higher rates.
~40 mV delta ~2.5% capacity delta
~80 mV delta ~8.4% capacity delta
~20 mV delta ~0.6% capacity delta
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Simulation Results: Diffusion Coefficient Variation across cell for 3C Discharge
Constant Diffusion Coefficient Variable Diffusion Coefficient
Distance from negative collector, mm
Time, min
Solid-phase diffusion coefficient has complex profile when concentration dependence is accounted for.
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Simulation Results: Solid-Phase Concentration Variation across cell for 3C Discharge
Constant Diffusion Coefficient
Variable Diffusion Coefficient
Distance from negative collector, mm
Variable diffusion case results gives smaller concentration gradient in positive electrode.
Negative Positive
Surface concentration
Average concentration
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Summary
• Dependence of solid-phase diffusion coefficient with lithium concentration has a strong theoretical foundation, and experimental validation.
• Accounting for concentration dependence of solid-phase diffusion coefficients has a significant effect of cell behavior at high rates.
• BDS allows this effect to be simulated with ease.
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Conclusion
Battery Design Studio® is the industry standard platform for:
• Analyzing data and visualizing results.
• Exchanging battery data and models.
• Pathway to pack and system design
with STAR-CCM+.