NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Coupling of Mechanical Behavior of Cell Components 

to Electrochemical-Thermal Models for ComputerAided Engineering of Batteries under Abuse

P.I.: Ahmad Pesaran

Team: Tomasz Wierzbicki and Elham Sahraei (MIT)

 Genong Li and Lewis Collins (ANSYS)

 M. Sprague, G.H. Kim and S. Santhangopalan (NREL)

June 17, 2014

This presentation does not contain any proprietary, confidential, or otherwise restricted information.

NREL/PR-5400-61885 Project ID: ES199
2

Overview

• Project Start: October 2013

• Project End: September 2015

• Percent Complete: 20%

• Safety concerns of Li batteries

• Thermal runaway of Li batteries 

due to heating

• Understanding the thermal 

response of batteries after 

crash-induced crush

• Total Project Budget: $1,003K

• Funding Received: $1,003K

o MIT Share: $200K

o ANSYS Share: $100K

o NREL SHARE: $703K

Timeline

Budget

Barriers Addressed

• Massachusetts Institute of 

Technology (MIT)

• ANSYS

• NREL Energy Storage Team

• NREL High Performance 

Computing Team

• Project Lead – NREL 

Partners
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Relevance – DOE VTO Program

• The EV Everywhere Grand Challenge aims to produce 

plug-in electric vehicles as affordable and convenient for 

the American family as gasoline-powered vehicles by 

2022 

o Electric vehicles must be as safe as conventional vehicles

o EV batteries must not lead to unsafe situations under abuse 

conditions

• This project was started in October 2013 based on a 

proposal in response to the January 2013 DOE VTO FOA.

• The goal is to develop computer-aided engineering tools 

to accelerate development of safer lithium-ion batteries.
4

Relevance – Project Objectives

This project addresses two abuse conditions: “crush” 

and “thermal ramp” of cells

• The main objective is to develop a model to couple the 

electrochemical-thermal (ECT) behavior of a lithium-ion cell 

to its structural behavior after rapid mechanical 

deformation

• A second objective is to develop a model to predict the 

thermal response of cells to thermal ramp 

• A supporting objective is to make the models compatible 

with CAEBAT-1 and its Open Architecture Software (OAS) 

for wider proliferation of their use. 
5

Milestones – Met (✔) or On-Track

Milestone Title Due Date

Place subcontracts with MIT December 2013

Place Subcontract with ANSYS December 2013

Develop user-interface software for running chemical kinetics model August 2014

Document user-interface software and demonstration of CAEBAT-1 compatibility November 2014

Demonstrate compatibility of chemical kinetic model with OAS February 2015

Document validation of chemical kinetic abuse model and computational model 

performance 

April 2015

Chemical kinetic abuse model input files available on CD and/or publicly accessible 

website

June 2015

Document results of mechanical deformation experiments April 2014

Document validation and computational mechanical deformation and damage model September 2014

Document simulation results of ECT response of mechanically crushed cell October 2014

Document validation and computational model performance April 2015

Document user interface for importing mechanical-ECT model to CAEBAT-1 platform June 2015

Document implementation of mechanical-ECT software with Oak Ridge National 

Laboratory’s (ORNL’s) OAS

September 2015

✔

✔
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Approach – Thermal Ramp 

Transfer NREL chemical kinetic abuse model to ANSYS 

CAEBAT-1 platform

• Model chemical kinetics reactions happening in 

lithium-ion cells at elevated temperatures, including 

o Solid electroplate interface (SEI) decomposition

o Negative-solvent reactions 

o Positive-solvent reactions

o Electrolyte decomposition

• Include actual internal geometry of the cells

• ANSYS to create user-friendly interface to access 

the above chemical reaction model in CAEBAT-1 

platform

• Make the model/tool compatible with OAS
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Approach – Cell Crush Modeling

Couple MIT’s mechanical model with NREL’s ECT model 

• Simulating simultaneous mechanical, electrochemical, 

and thermal response of a cell due to crush is very 

complex and requires modeling simplifications 

• Our approach is to assume that crush is rapid (e.g., 

the cell is damaged in less than a fraction of a second) 

• We also assume that electrochemical and thermal 

response of a cell takes longer than seconds 

• This allows us to couple the mechanical aspect with 

the thermal aspect in a sequential, one-way fashion 
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Accomplishments – NREL Thermal Ramp

NREL’s Abuse Reaction Kinetics (ARK) model has 

been documented and shared with ANSYS 

NREL’s ARK Model 

• Empirical reaction model

o Built from calorimetric test data

• Evaluates the rate of heat from 

exothermic decomposition reactions

Bottom-up approach

• Abuse reactions among cell components superimposed

• Incorporated exothermic component reactions commonly addressed; readily 

accommodates other abuse reactions

Model Equation – Box Model

S : volumetric reaction heat 

H : heat of reaction

dα/dt : reaction rate 

k(T) : temperature-dependent rate constant
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Accomplishments – NREL Thermal Ramp

Developed a user friendly tool for parameter 

identification for the ARK model 

Example: Identifying electrolyte decomposition reaction parameter from ARC data 

• In-house ARC tests carried out for a 

type of lithium-ion battery electrolyte

• Superposition theorem is used to 

isolate the peaks; fit these two peaks 

individually

0 500 1000 1500 2000 2500 3000 3500 4000

0

80

160

240

320

400

Temperature ( oC )

e pe atu e a d essu e as a u ct o o e

Temperature

Pressure

0 500 1000 1500 2000 2500 3000 3500 4000

0

80

160

240

320

400

Temperature ( oC )

e pe atu e a d essu e as a u ct o o e

Temperature

Pressure

0 500 1000 1500 2000 2500 3000 3500 4000

0

44

88

132

176

220

Pressure ( bar )

Test data

140 160 180 200 220 240 260

10-2

10-1

100

101

Temperature ( oC )

dT/dt ( oC/min )

SQ tt g o C ( ect o yte) S cu e

Experimental data

Initial guess

Final fitting resultsInitial guess

Test data

Fitted model

aE rK m n p

Initial 2.74E5 5.14E25 1 0 0

R1 2.53E5 5.14E25 3 0.3762 0.2430

R2 2.80E5 5.14E25 0 0.0991 2.1145

Note: The curve shown above is not a unique solution

ARC: Accelerating Rate Calorimeter
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Accomplishments – ANSYS

• At the time this presentation was prepared, the 

ANSYS subcontract was still being negotiated

• We expect the subcontract to be finalized and signed 

by mid May 2014 

• Although ANSYS has not started work at the time this 

presentation was prepared, we do not think this will 

adversely affect the future milestones/deliverable for 

this project 
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Accomplishments – MIT Crush

In order to couple the existing ECT model with 

the mechanical model of a cell, it is necessary 

to determine:

• Location of mechanical

failure within the jellyroll

• Crack orientation

• Size of the fractured region

This information is provided by the new 

enhanced anisotropic model of the jellyroll
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Accomplishment – MIT Crush

Calibration of a Single Cell

Compression tests in in-plane and

through thickness directions

Tensile tests on components of the 

electrode/separator assembly
13

Accomplishment – MIT Crush

Anisotropic Homogenized Material Model

Separate tests should be done in machine, transverse, through 

thickness directions
14

Accomplishments – NREL Crush

• Software installed on NREL cluster 

and first round of models set up

• To facilitate integration of the 

different models, a “‘test-case” 

crush simulation is performed at 

NREL

• This set of simulations will help:

o Establish what parameters must be 

exchanged among the models

o Compute local heat generation rates in 

an arbitrary deformed cell-geometry

• When crush models from MIT 

become available, NREL will 

integrate the ECT models to the 

deformed geometry

Crush-simulation on an electrode pair: for 

different crush bar orientations, the contact 

between individual layers is simulated

Geometry & Mesh

Splitting of individual 

layers during a crush

Displacement
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Accomplishments – NREL Crush (Contd.)

Resistivity vs. Deformation:

• Select deformation threshold for 

electrical contact to be formed

• Generate deformed geometry

• Compute effective resistance as 

function of percentage deformation

• Develop simplified relationships to 

scale up results from individual 

layers across the cell

• Include simplified expressions in 

cell-level ECT simulations

Electrical contact is predicted using the local 

z-velocity and the deformation threshold

Change in resistivity during crush

z-velocity
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Responses to Previous Year Reviewers’ Comments

This project is new and was not presented at AMR in FY2013.
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Collaborations and Coordination

• NREL Energy Storage Team (lead)

• NREL High Performance Computing Team

• MIT

• ANSYS
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Remaining Challenges and Barriers

• “Multi-layer puncture” approach for loose coupling 

of mechanical deformation to ECT behavior may not 

be automatable to capture damage zones created 

by different crush loads and orientations

• Model validation with experimental data may take 

longer than expected; simulation may not represent 

a particular experiment, resulting in repeated 

simulation, and insufficient time and budget for 

further validation

• Integration of new code with emphasis on 

mechanical/structural/chemical physics into ORNL’s 

OAS 
19

Future Work

• Transfer Existing Chemical Kinetic Abuse Model to Current 

CAEBAT-1 Platform, Maintaining Compatibility with OAS 

Framework

• Validate Software from Task 2 in Thermal Ramp Abuse Conditions 

against Published Experimental Data

• Create Validated Mechanical Deformation (Crush) Computational 

Models

• Couple MIT’s Mechanically Deformed Models with NREL’s ECT 

Models

• Implement Coupled Mechanical-Electrical-Chemical-Thermal 

Model in ANSYS CAEBAT-1 Platform and Make It Compatible with 

OAS
20

Summary

• This project was funded based on the team’s proposal to the 

2013 DOE VTO FOA

• This project is focused on coupling models of crush and thermal 

runaway of cells 

• Eventual goal is to be able to predict the onset of thermal 

runaway after crash-induced crush or thermal ramp 

• MIT is under subcontract; ANSYS subcontract is pending

• We have documented our chemical kinetics reaction model for 

incorporation into the ANSYS CAEBAT-1 platform (FLUENT-15)

• A procedure is being developed for an anisotropic model for the 

jellyroll with testing and calibration

• An approach to link mechanical deformation to short resistivity 

was created 
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Back Up Slides
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Causes of Battery Failure

Focus for this project
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Crack as seen in CT Scan Crack as seen in FE simulation

 Demonstrating MIT’s capabilities of the element-deletion technique:

The figures above compare the finite element (FE) prediction with an actual 

crack observed by CT scan of a cell under load; good results were obtained 

by choosing a proper value of fracture strain (maximum principal tensile 

strain) 

Crash Formation under Hemispherical Punch
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Partially Crushed 18650 Cell between Rigid Plates

Crush experiments and FE simulation performed at MIT
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LS-Dyna Simulation of 18650 Cell Crush
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Typical Results of NREL Chemical Kinetics 

Reaction Model

Electrode active material/solvent reactions trigger thermal 

runaway in a LiCoO2/graphite cell