Thermal Abuse Modeling of Li-Ion Cells 

and Propagation in Modules

4th International Symposium on Large Lithium-Ion 

Battery Technology and Application (with AABC Conference)

In conjunction with the 8th Advanced 

Automotive Battery Conference

Tampa, Florida

May 13-16, 2008

Gi-Heon Kim, Ahmad Pesaran, and Kandler Smith

(ahmad_pesaran@nrel.gov)

National Renewable Energy Laboratory

NREL/PR-540-43186

Supported by 

Vehicle Technologies Program, Energy Storage Technologies

Office of Energy Efficiency and Renewable Energy 

U.S. Department of Energy
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Outline

• Background

• Objectives

• Simulating Internal Short in a Cell

– Parametric runs

– Results

• Propagation in a Module

• Summary

Methodology for Understanding Impacts of Battery Design 

Parameters on Thermal Runaway in Lithium-Ion 

Cells/Modules
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Background

• Last year, in LLIBTA-3, we introduced our 

approach for modeling Li-ion thermal abuse1

– Chemical reactions at elevated temperatures

• SEI decomposition

• Negative-solvent reaction

• Positive-solvent reaction

• Electrolyte decomposition

– Captured real 3-D geometries and boundary conditions

– Performed oven heat test simulations

– Simulated localized heating – cell internal short

– Cell-to-cell propagation in a module

• Balance between discrete heat sources and thermal network

• Heat transfer through radiation, conduction, and convection

1G.-H. Kim, A. Pesaran “Analysis of Heat Dissipation in Li-ion Cells & Modules for Modeling of Thermal 

Runaway,” 3rd Large Lithium Ion Battery Technology and Application, May 2007, Long Beach, CA

Used literature information for 

graphite–cobalt oxide chemistry
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Thermal Runaway

External Heating

Over-Charging

High Current Charging

Crush

Nail penetration

External 

Abuse Conditions

External Short

Over-Discharging

Thermal Runaway - Background
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Thermal Runaway

If Heating rate 

exceeds 

Dissipation rate

Internal Short Circuit

Lithium Plating

Causing or Energizing 

Internal Events or 

Exothermic Reactions

Decompositions

Electrochemical 

Reactions

Electrode-Electrolyte

Reactions

External Heating

Over-Charging

High Current Charging

Crush

Nail penetration

External 

Abuse Conditions

External Short

Over-Discharging

Thermal Runaway - Background
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Thermal Runaway

Leak

Smoke

Gas Venting

If Heating rate 

exceeds 

Dissipation rate

Internal Short Circuit

Lithium Plating

Causing or Energizing 

Internal Events or 

Exothermic Reactions

Decompositions

Electrochemical 

Reactions

Electrode-Electrolyte

Reactions

External Heating

Over-Charging

High Current Charging

Crush

Nail penetration

External 

Abuse Conditions

External Short

Over-Discharging

Rapid Disassembly

Flames

Thermal Runaway

Thermal Runaway - Background

Focus of the modeling
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• Formulated Exothermic Reactions at elevated temperatures

Reproduce thermal abuse modeling of Li-ion cells provided by 

Hatchard et al. (J. Electrochem. Soc. 148, 2001);

Bob Spotnitz provided insight for reaction formulation 

• Extended to multi-dimensional models capturing actual thermal 

paths and geometries of cells and modules.

Component reactions were fitted to Arrhenius type reactions.

Kinetic parameters were determined from ARC/DSC literature data. 

A commercial finite-volume method (FVM) 

solver, FLUENT, was used. 

Background - Approach
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Background- 3D Oven Heat Test

P/S: positive/cathode-solvent 

N/S: negative/anode-solvent

*D18H65: Diameter of 18 mm, Height of 65 mm

Temperature Heat P/S N/S

201

o 367 C

Small Cell (D18H65)*

Temperature Heat

P/S N/S

198

oC 209 Although oven test is not 

a highly multidimensional 

phenomenon, it still 

demonstrates noticeable 

spatial distribution, 

especially in large cells.

Large Cell (D50H90)

Average Temp after 

cell exposed to 

155 C.
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• Use the 3D Li-ion battery thermal abuse “reaction” model developed 

for cells to explore the impact of the location of internal short, its 

heating rate, and thermal properties of the cell. 

• Continue to understand the mechanisms and interactions between 

heat transfer and chemical reactions during thermal runaway for Liion cells and modules. 

• Explore the use of the developed methodology to support the 

design of abuse-tolerant Li-ion battery systems.

Continue to explore thermal abuse behaviors of Li-ion cells and 

modules that are affected by local conditions of heat and 

materials

Objectives of this Study
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Cell Level Thermal Runaway Analysis

• Internal Short Simulation

 Impact of short location in a cell

 Impact of thermal property of cell materials

 Impact of heating rate at short event
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Model Description

• MESH

 Computational grid: 200K

 Grid size: ~1 mm by 1 mm by 1 mm 

 Max: 2.01 mm3 ; min: 0.31 mm3

1⁄2 Model with Symmetry Plane

Hot-Spot

 Localized energy is 

released in a short period 

of time in a very small 

volume of the core.

 Initially we assumed 5% 

of stored electric energy 

released

 Simulation of details of 

initial process of short is 

challenging, but we are 

trying to predict what 

happens after short

happens.

163 mm

54 mm

Heat Sources

 Exothermic reaction heat

 No resistive/Joules 

heating

Core Material

 Cylindrically orthotropic properties

Thermal Boundary Conditions

 Natural/forced convection

 Gray-body radiation
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Temperature Evolution after a Short

(oC)

Internal T External T

0 20 40 60 80 (sec)

Delay between measuring external temperature and 

internal event, external sensing may be too late.

0 10 20 30 40 50 60 70 80

100

200

300

400

500

600

700

Time(sec)

Temperautre (oC)

T

avg

Tneg term

Tpos term

Tcan surf

T

avg

Tneg term

Tpos term

Tcan surf

Short in the middle of cell

Local internal temperatures of 

core could exceed 600°C

5% of stored electric energy released 

in a short time at a small portion of 

active volume.
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Volumetric Heat Generation after a Short

(W/m3)

0 20 40 60 80 (sec)

Total heat

SEI decomposition

Positive/electrolyte

Negative/electrolyte

(Total and due to various reactions, showing how reactions propagate)

5% of stored electric energy released in a short time 

at a small portion of active volume.
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Impact of the Location of the Short

Initial location of short and

thermal paths and material distributions

Propagation pattern 

Heat release duration







Li-ion Thermal Abuse Reaction Model

Layered structure of electrodes 

Preferred directions of reaction propagation

5% of stored electric energy released in a 

short time at a grid point.
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Short Near Exterior Surface vs.

Short Near Center of Cell

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

middle

near surface

near center

Snapshots of temperature distribution at interior 

(top) and surface (bottom) 38 seconds after short

Total heat released (area 

under each curve) is about the 

same for three cases.

Heat dissipation is dependent on the location of heat release and thermal paths.

(oC)
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Short Near Surface vs. Near Center

2 20 38 54

Temperatures

sec

Near center

• Location of short has impact on how heat flows and abuse reactions propagate 

(e.g., delay in abuse reaction heat release for near-surface case). 

Near surface

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

near surface

near center

Near surface

Near center

(oC)
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Short Near Bottom of Cell vs.

Short Near Top of Cell

Snapshots of temperature distribution at interior 

(top) and surface (bottom) 25 seconds after short

Total heat released (area 

under each curve) is about the 

same for three cases.

Heat dissipation is dependent on the location of heat release and thermal paths.

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

middle

near bottom

near top

(oC)
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Short near top .vs. Short near bottom

near bottom

near top

middle 2 14 26 38 sec

Temperatures: near-top short

Temperatures: middle short

Heat dissipation is dependent 

on the location of heat release 

and thermal paths. (oC)
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Heat Capacity

Thermal Conductivity

Cp

50% less k 50% more

5% less 5% more

Electrode/current collector thicknesses and

relative amount of component materials 

Volumetric heat generation

Thermal properties of electrode sandwich





Impact of Thermal Properties
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Heat Capacity Impact on Cell Thermal Runaway

Heat Capacity

5% less Cp 5% more

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

base

5% less

5% more

Temperatures

10 20 30 40 sec

Small cp

Large cp

Reaction propagation is faster in a cell with smaller heat capacity.

5% of stored electric energy released in a 

short time at a small portion of active volume.

(oC)
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Core Thermal Conductivity Impact on 

Cell Thermal Runaway

Thermal Conductivity

50% less k 50% more

Temperatures

Small k

Large k

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

0 10 20 30 40 50 60 70 80 0

2

4

6

8

10

12

Time(sec)

Heat Generation (kW)

base

50% less

50% more

2 14 26 38 sec

Reaction propagation is slower in a cell with smaller thermal conductivity

(oC)
The 4th AABC-08 International Symposium on Large Lithium Ion Battery Technology and Application

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Temperature

20 sec

Impact of Amount of Released Heat

Heat: % of cell energy release at a very small volume 1% 5%

No thermal runaway with 

smaller heat release

Heat dissipates quickly 

without triggering thermal 

runaway.

Pattern of initial heat 

release at short events 

need to be investigated. 

We did an in-depth 

analysis.

(oC)

2 14 26 38
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Impact of Heating Rate in Short Events

Heat Release at a Short Event is affected by†

• Electrical Resistance of the Short

• Cell Power Rate (Power/Energy ratio)

• Cell Size (Capacity)

†This is based on our ongoing analysis and the details are beyond scope of 

this presentation. The next few slides look at a case with high-resistance 

short. Details of low-resistance case will be presented at other upcoming 

conferences.
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Quantifying Heat Release at Short Event

Total Heat [W] = Volumetric Heat for Current Production + Heat Release at Short (Short Heat )

Using Electrochemical Cell Model

High-resistance Short Cases (3Ω, 7Ω, 

10Ω) Observed from SNL Data

• Short current is determined by the 

short resistance rather than by the 

power rate or by the size of a cell.

• Relatively low c-rate for high 

resistance shorts

• Volumetric heat from current 

production is small

• Most released heat is local to the 

short site

0 200 400 600 800 1000 1200 1400 1600 1800

1

1.5

2

2.5

3

3.5

4

4.5

5

time [sec]

Heat [W]

18650 Cell Spec

• 1.35 Ah

• 30 mΩ

Total Heat (3Ω)

Total Heat (7Ω)

Total Heat (10Ω)

 

 

 

 

Short Heat (3Ω)

Short Heat (7Ω)

Short Heat (10Ω)
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Thermal Behavior of a Cell 

at High-Resistance Short Events

0 20 40 60 80 100

0

1

2

3

4

5

Reaction Heat [W]

Time [minute]

3Ω

7Ω

10Ω

Temperature Reaction Heat

18650 CoO2/graphite

30oC ambient, heat transfer coefficient on cell surface (h) = 7 W/m2K

0 20 40 60 80 100

0

100

200

300

400

500

600

700

Temperature [oC]

Time [minute]

3Ω

7Ω

10Ω

7Ω, with h=15W/m2K

Strong natural 

convection in air

Heat Dissipation vs Heat Release

h=7W/m2K
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Comparison of Thermal Behavior

Between two High-Resistance Short Events

0 20 40 60 80 100

0

0.2

0.4

0.6

0.8

1

Reaction Heat [W]

Time [minute]

SEI Decompostion

Negative/Electrolyte

Positive/Electrolyte

NET

0 20 40 60 80 100

0

0.2

0.4

0.6

0.8

1

Reaction Heat [W]

Time [minute]

SEI Decompostion

Negative/Electrolyte

Positive/Electrolyte

NET

7Ω Short

10Ω Short

Temperature Component Reaction Heat

Led to 

thermal 

runaway.

Did not 

lead to 

thermal 

runaway.

18650 CoO

2/graphite Cell

30

oC ambient, (h) = 7 W/m

2

K

Can a short 

have such a 

high 

resistance?

(oC)
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Delayed Separator Breakdown 

With No Cell Runaway (1 amp current)

0

20

40

60

80

100

120

140

160

180

200

0 500 1000 1500 2000

Time (s)

Temperature (C)

0

5

10

15

20

25

30

Cell Voltage (V)

Pos. Term. Temp

OCV Voltage

Gen3 Electrodes

Celgard Separator

EC:EMC\LiPF6

Observed Events 

Internal Short (may or may not lead to thermal runaway)

(E. Peter Roth and Tom Wunsch)

SNL Data: From presentations at DOE’s Advanced Technology Development Meetings 

• Short occurred at about 700 sec.

• Temperature started to increase and 

reached thermal equilibrium at about 

160oC.

• Thermal runaway was not observed.

• Heat dissipation appears fast enough.

• High resistance short (>5Ω) is likely.

Immediate Separator Failure With Potential

Cell Thermal Runaway (1 amp current limit)

0

50

100

150

200

250

300

350

400

450

1250 1270 1290 1310 1330 1350 1370 1390

Elapsed Time (sec)

Temperature (C)

0

2

4

6

8

10

12

14

16

18

20

Cell Voltage (V)

Cell Temp

Voltage

Gen2 Electrodes

Celgard Separator

EC:PC:DMC\LiPF6

Short & Thermal Runaway

observed by SNL

• Heat release was much faster than dissipation.

• Low resistance short (<<1Ω) is likely

18650 Cells
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Module-Level Analysis of Cell-to-Cell 

Thermal Runaway Propagation

How can a module be more resistive to cell-to-cell thermal 

runaway propagation?

Li-ion Thermal Abuse Reaction Model
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Background 

We proposed that Cell-to-Cell Propagation in a module is

a result of the INTERACTION between the distributed chemical 

sources and the thermal transport network through a module.

• Formulated exothermic chemical reactions of a cell at elevated 

temperatures.

• Quantified heat transfer among the cells in a module

• We used multi-node lumped approach last year; this year we have 

looked at 3D approach

Approach for the analysis of this system

Radiation heat transfer

Conduction heat transfer

Convection heat transfer

dispersed sources thermal network
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0 10 20 30 40 50 60 70 80 90 100

50

100

150

200

250

300

350

400

450

500 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Base case (air) Graphite matrix impregnated with PCM

It appears that a very conductive medium may reduce the chance for propagation.

NOTE: * PCM/graphite matrix is a highly porous graphite structure that is impregnated with phase-change 

material (PCM) (based on information from S. Al-Halaj et al.).

0 10 20 30 40 50 60 70 80 90 100

0

100

200

300

400

500

600

700 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Impact of a Highly Conductive Heat Transfer Medium

Rather than the air used in the base case (left), a highly conductive PCM/graphite 

matrix was used to fill the space between the cells in the module (right). 

Example of Multi-node Lumped Module Analysis
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3D Module Propagation Model

Objective: Developing a 3D cell and module 

geometry capturing cell-to-cell interconnects

CAD drawing of a 10-cell module

(Each cell is in its own individual sleeve) Grid for the 10-cell module

Top view

Bottom view
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2 seconds apart between each frame

Close Look at Reaction in an Individual Cell 

in the 10-cell Module
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Top view

Side view

Reaction Propagation in a Module 

with 10 Cells in Series

The order at which cells go into 

thermal runaway depends on the 

cell interconnect configurations.
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On-going Work

Module-Level Research in Progress

Adding the electrical network modeling

• Impact of thermal transport network + electrical 

network

6 Parallel, 4 Series 
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• Li-ion thermal abuse reaction chemistry was implemented in a 

finite-volume 3D cell model to address various design elements.

 Examined impact of cell design parameters

 Investigated impact of short location and thermal properties

 Some shorts may not lead to thermal runaway

 Heat dissipation is important, but depending on the amount of heat 

release from abuse

• Propagation of abuse reaction through a module was simulated.

 A complicated balance between the heat transfer network and 

dispersed chemical sources

 Balance is affected by module design parameters such as cell 

size, configuration and size of cell-to-cell connectors, and cellto-cell heat transfer medium

Summary
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Future Work

• Improve model through comparisons with experimental data

from other laboratories

• Continue examining the impact of design variables

• Address the limitation of the model

• Expand the model capability to address various chemistries and 

materials, such as iron phosphate

• Investigate internal/external short by incorporating an thermally 

coupled electrochemistry model into the three-dimensional cell 

model

• Use the models to investigate the impact of (shut-down) 

separators

• Work with developers on specific cell and module designs
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Acknowledgments

Funding is provided by Energy Storage Technologies 

R&D in the DOE Vehicle Technologies Program, 

Office of Energy Efficiency and Renewable Energy

• Tien Duong

• Dave Howell