Advanced Thermal Modeling of Batteries 

CBD Battery Design LLC

Empirical Battery Models

STAR Asia Conference December 2013

Overview Battery Design Process Use of Physics-based model for synthetic

data generation Parameters for RCR Table Model Evaluation of RCR Table Model Fits Conclusion

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Overview of Battery Design Processwith Empirical Model

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Test cell Fit data to modelUse model to simulate battery performance

What procedure(s) to use?

What temperatures?

What model?

How to validate fit?

Can battery deliver required performance?

Is heat‐transfer adequate to ensure max. temperature not exceeded and uniform?

Selected Simulation Models in Battery Design Studio

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(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

Consumer Electronics,

EV

NTG

HEV/PHEV Module/Pack

RCR

Cell Design

DISTNP

Simple, easy to create model, best for simple discharge/charge, thermal analysis

Quick response for frequent charge/ discharge like HEV/PHEV

Useful for design. Solves transport, kinetics, equations

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(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

DISTNP model allows prediction of cell performance based on materials properties and cell design.

Battery Physics – DISTNP Model

5T. Fuller, M. Doyle, J. Newman, J. Electrochem. Soc., Vol. 141 (1994) 1‐10

DISTNP model can simulate aging

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Impedance rise and capacity loss due to SEI growth.

4C rate

2C rate

Lithium‐Ion Battery TransportSolid‐ and Liquid‐Phase Gradients

A. Nyman, T. G. Zavalis, R. Elger, M. Behm, G. Lindbergh “Analysis of the Polarization in a Li‐Ion Battery Cell by Numerical Simulation” J. Electrochem. Soc., 157(11) A136‐A1246 (2010).

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DISTNP model allows sources of voltage loss in cell to be quantitatively assigned to specific physical processes.

Electrolyte diffusion polarization

dxjxc

FcRT

j LL

c

L

Ltot

0

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Kinetic Overpotential L

avesurfloctot

dxEEajj 0

1

Contact Resistance Losses contactappl Rj

Liquid-Phase Ohmic drop L

eff

L

tot

dxjj 0

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Solid-Phase Ohmic dropL

eff

S

tot

dxjj 0

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Solid Diffusion Polarization

L

surfLSloctot

dxEajj 0

1

Approach to parameterize RCR model in BDS

Generate synthetic data with DISTNP model

Use BDS gap tool to parameterize RCR model

Simulate HPPC test using RCR model

Simulate Drive Cycle using RCR model

Compare to synthetic

data

Questions:• For HPPC test, how sensitive are fitted

parameters/simulation results to:• pulse duration? 2 s, 10 s, 30 s• pulse currents? 5 C rate versus 10 C rate• Temperature? 10, 20, 40, 50C

• How well does temperature interpolation work?8

DISTNP Model Cell Used for Generation of Synthetic Data

Model uses two different particle sizes, realistic electrolyte properties, temperature dependent solid-phase diffusion and kinetics.

Generate Synthetic Data

Goal should be to emulate good physical testing.

Testing should be done under controlled temperature and ideally cell temperature will be uniform. Thin, pouch cell is ideal for

characterizing electrochemical behavior.

Cell can be clamped with aluminum plates and placed vertically in environmental chamber to provide well-defined boundary conditions for heat transfer between cell and chamber.

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Generate Synthetic Data (cont.)

Hybrid Pulse Power Characterization (HPPC) Test provides convenient, standardized method to characterize impedance and voltage relaxation of battery of state of charge from 90 to 10%.

http://www.uscar.org/guest/teams/11/U-S-DRIVE-Electrochemical-Energy-Storage-Tech-Team

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Analysis of Voltage Losses in HPPC Test

Contact resistance, a purely ohmic loss, is major source of voltage loss. At 10C the voltage loss due to electrolyte diffusion polarization and activation overpotential are much larger than at 30C. At 30 the voltage loss is mainly due to contact resistance and electrolyte diffusion polarization.

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Breakdown of voltage losses in HPPC Discharge Pulse

Major source of voltage drop is contact resistance between electrode coating and current collector

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RCR Table ModelParameters can be entered as tables. Interpolation between values as a function of state of charge is done using Bezier splines. Linear interpolation is used to compute values at intermediate temperatures.

Model is easy to use and computationally efficient.

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Gap tool in BDS provides automatic regression of USABC Equivalent Circuit Model (RCR type)

User simply selects data file with HPPC data and Gap tool automatically generates table of RCR parameters.

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RCR Parameters can be entered into BDS RCRTable Model

One table for each temperature can be entered.

Linear interpolation is used to obtain parameter values at intermediate temperatures.

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Parameterized RCRTable Model

Entered parameters for 10, 20, 40 and 50 °C

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Drive Cycle Simulation: US06 PHEV Charge Depleting

A Ah

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Comparison of computation times

RCRTable model is ~104 times faster than DIST model

45.9 min

0.2 s

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COMPARISON OF RCR MODEL TO SYNTHETIC DATA

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Comparison of Fitted HPPC test to synthetic data

RMS error = 17 mV10°C, 5 C rate, 10 s pulse

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Drive Cycle Simulation at 10C: Voltage

RMS error = 12 mV10°C, 5 C rate, 10 s pulse

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Drive Cycle Simulation at 10C: Temperature

RMS error = 0.08 °C10°C, 5 C rate, 10 s pulse

1012141618

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Drive Cycle Simulation at 30C: VoltageParameters Interpolated from 20 and 40C

RMS error = 12.8 mV

30°C, 5 C rate, 10 s pulse

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Drive Cycle Simulation at 30C: TemperatureParameters Interpolated from 20 and 40C

RMS error = 0.108 °C30°C, 5 C rate, 10 s pulse

As time progresses differences in temperature accumulate.

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Summary of Drive Cycle Simulations

*Interpolated

Comments• Predictions are very good, 2 s give best overall voltage simulation• Fits at 10C rate were comparable

T, °C

5C Rate - RMS Error milliVolts

Pulse Time, sT, °C

5C Rate - RMS Error degrees C

Pulse Time, s2 10 30 2 10 30

10 7.7 12.0 10 0.044 0.01220 13.8 13.9 13.0 20 0.163 0.149 0.06330 13.2 12.8 17.3 30 0.136 0.108 0.25340 8.7 13.1 13.3 40 0.202 0.155 0.153

average 10.8 13.0 14.5 average 0.14 0.11 0.16

55 31.6 % SOC

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Drive Cycle Simulation at 20C: Voltage

RMS error = 33 mV20°C, 5 C rate, 10 s pulse

70 23.4% SOC

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Drive Cycle Simulation at 20C : Temperature

RMS error = 0.64 °C

10°C, 5 C rate, 10 s pulse70 23.4% SOC

~15°C temperature rise20

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Summary Physics-based model is useful for generating

synthetic data• Realistic simulations can account for different

particle sizes, electrode formulations, separators, electrolytes, kinetics, aging

RCR Table model is computationally efficient and provides excellent prediction for data sets where voltage losses are mainly ohmic.• Predicted voltage and temperature correspond

closely for parameters obtained over range of rates and temperatures

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