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.

Development of a Novel Test Method for 

On-Demand Internal Short Circuit in a Li-Ion Cell

Large Lithium Ion Battery Technology and Application Symposium

Advanced Automotive Battery Conference

Jan 25-28, 2011, Pasadena, CA Matt Keyser, Dirk Long, Yoon Seok Jung, 

and Ahmad Pesaran

NREL, Golden, CO

Eric Darcy

NASA-JSC, Houston, TX

Ben McCarthy, Luke Patrick, 

and Chad Kruger

Dow-Kokam, Lee’s Summit, MO

This work is funded by DOE’s Energy Storage R&D at 

the DOE Vehicle Technologies Office (David Howell)

NREL/PR-5400-50082
NATIONAL RENEWABLE ENERGY LABORATORY

Li-Ion Cell Internal Short, a Major Concern

• Li-ion cells provide the highest specific energy 

(>180 Wh/kg) and energy density (>360 Wh/L) 

rechargeable battery building block to date with the 

longest life.

• Electrode/electrolyte thermal instability and 

flammability of the electrolyte of Li-ion cells make 

them prone to catastrophic thermal runaway under 

some rare internal short circuit conditions.

• Despite extensive QC/QA, standardized industry 

safety testing, and over 18 years of manufacturing 

experience, major recalls have taken place and 

incidents still occur.

• Many safety incidents that take place in the field 

originate due to an internal short that was not 

detectable or predictable at the point of 

manufacture.

• These internal short incidents are estimated at 1 to 

10 ppm probability (well beyond 6 σ) in consumer 

applications using cells from experienced and 

reputable manufacturers1.

• Estimated at 1 in 235 million with commercial cells 

screened for spacecraft applications2.

• What about custom-made large cells?

• Not enough data exists to build statistically useful 

probabilities.

1. Barnett, B., TIAX, NASA Aerospace Battery Workshop, Nov 2008

2. Spurrett, R., ABSL, NASA Aerospace Battery Workshop, Nov 2008

Aftermath of an external short incident

Aftermath of a suspected internal short incident

Photos Credit: NASA – Eric Darcy 211/20/08
NATIONAL RENEWABLE ENERGY LABORATORY

Motivation

Lithium Ion Battery Field Failures - Mechanisms

• Latent defect (i.e., built into the cell during manufacturing) gradually moves into position to 

create an internal short while the battery is in use.

• Sony3 concluded that metallic defects were the cause of its recall of 1.8-million batteries in 2006

• Inadequate design and/or off-limits operation (cycling) causes Li surface plating on anode, 

eventually stressing the separator

Both mechanisms are rare enough that catching one in the act or even inducing a cell 

with a benign short into a hard short is inefficient.

Current abuse test methods may not be relevant to field failures

• Mechanical (crush, nail penetration, etc.)

• Cell can or pouch is breached; pressure, temperature dynamics are different

• Thermal (heat to vent, thermal cycling, etc.)

• Cell exposed to general overheating rather than point-specific overheating

• Not a valid verification of “shutdown” separators

• Electrical (overcharge, off-limits cycling, etc.)

• Not relevant to the latent-defect–induced field failure

To date, no reliable and practical method exists to create on-demand internal shorts in 

Li-ion cells that produce a response that is relevant to the ones produced by field 

failures.

3. Nikkei Electronics, Nov. 6, 2006

3
NATIONAL RENEWABLE ENERGY LABORATORY

Previous Efforts & Shortcomings

Penetration and Crush Tests Methods 

• Army/Navy/FBI use nail/bullet penetration tests4.

• NASA uses a crush test with a rounded rod5.

• Underwriters Laboratory (UL) uses a blunt nail crush test6. 

• Motorola/ Oakridge National Laboratory use a pinch (crush) 

test on pouch cells7.

Reliable, but not representative of field failures

4. Lyman, P., and Klimek, P., 69th Lithium Battery Technical/Safety Meeting, Myrtle Beach 2004

5. Jeevarajan, J., 2008 NASA Aerospace Battery Workshop, Huntsville, AL

6. Chapin, T., and Wu, A., 2009 NASA Aerospace Battery Workshop, Huntsville, AL

7. Maleki, H., and Howard, J.N., J. Power Sources, 2008

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NATIONAL RENEWABLE ENERGY LABORATORY

Previous Efforts & Shortcomings (cont.)

Contamination Test Methods 

• BAJ8 and Celgard9 retrofitted a Ni particle into the jellyroll of a cell 

and triggered the event using a crush test.

• Sandia National Laboratory10,11,12 has tried several methods:

• Building cells with Ni particle contamination and combined with sonication, 

thermal ramp, or overcharge to trigger the short

• Implanting low melting indium (In) alloy in the separator combined with heat 

trigger.

• TIAX13 retrofitted a metallic particle into the jellyroll of a cell and 

triggered the event by repeated charge/discharge cycling.

More relevant, but with reliability and reproducibility 

challenges

8. Battery Association of Japan, Nov 11, 2008 presentation on web

9. S. Santhanagopalan et al., J. Power Sources, 194 (2009) 550-557

10.Orendorff, C., et al., ECS Meeting, May 2009

11. Orendorff, C., and Roth, E.P., USABC TT Meeting, Feb 2009 

12. Orendorff, C., et al., ECS Meeting, Oct 2010

13. Barnett, B., et al., 2010 Power Sources Conference

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NATIONAL RENEWABLE ENERGY LABORATORY

Objectives

Establish an improved ISC cell-level test method that:

• Simulates an emergent internal short circuit (ISC) by detailing the 

cell assembly and test conditions that replicate catastrophic field 

failure behavior due to a latent cell defect

• Capable of triggering the four types of cell internal shorts

• Produces consistent and reproducible results

• Cell behaves normally until the short is activated – age cell 

before activation.

• We can establish the test conditions for the cell – SOC, 

temperature, power, etc...

• Provides relevant data to validate ISC models

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NATIONAL RENEWABLE ENERGY LABORATORY

NREL Cell Internal Short Circuit Development

Internal short circuit device design

• Small, low-profile and implantable into Li-ion cells, preferably during 

assembly

• Key component is an electrolyte-compatible phase change material (PCM)

• Triggered by heating the cell above PCM melting temperature (presently 

40 C – 60 C)

• In laboratory testing, the activated device can handle currents in excess of 

200 A to simulate hard shorts (<5 mohms).

• Phase change from non-conducting to conducting has been 100% 

successful during trigger tests.

Patent application filed for the ISC Device 

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NATIONAL RENEWABLE ENERGY LABORATORY

NREL Internal Short Design

8

Separator

Positive current collector (Al)

Cathode electrode

ISC device

Wax

Negative current collector (Cu) Anode electrode

Graphic is not to scale

and for illustration only Activated short with PCM wicked

by battery separator

Photo Credit: NREL – Dirk Long
NATIONAL RENEWABLE ENERGY LABORATORY

Hot Plate

Laboratory Test Fixture 

9

Electrical Insulation

+

Mass

Internal short circuit 

simulator

-

Power cables to a 

battery cycler

Copper buss bars

Acrylic guide tube

Thermal/Elec. Insulation

Varying mass yields pressures

between 1 and 15 psi

Photo Credit: NREL – Dirk Long
NATIONAL RENEWABLE ENERGY LABORATORY

0

50

100

150

200

250

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140

Current (Amps), Temperature (

oC)

Voltage Drop Across Platens (Volts) 

Time (Seconds)

Voltage Current Temperature

Laboratory Test Fixture – Internal Short Test

Hot Plate

Electrical Insulation

+

Mass

-

Thermal/Elec. Insulation

10

Short Impedance ~ 0.5 mΩ
NATIONAL RENEWABLE ENERGY LABORATORY

Internal Short Circuit – Coin Cell Tests

0

5

10

15

20

25

30

35

40

45

50

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25 30 35 40

Copper Platen Temperature (oC)

Coin Cell Voltage (Volts)

Time (Minutes)

Voltage Temperature

Nine of nine coin cells shorted with new ISC device design, shown here using a 42 – 44°C melting PCM.

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NATIONAL RENEWABLE ENERGY LABORATORY

Cell Internal Short Circuit Development

• NREL partnered with Dow-Kokam (DK) to have cells 

assembled and tested with the new ISC device.

• Design of the device uses a flexible PCM, resulting in a 

device that is compatible with automated cell 

stacking/winding equipment.

• To date, over 50 cells have had the device implanted into it. 

All cells show nominal capacity and voltage curves.

12

ISC Cathode Anode

Al Current 

Collector

Cu Current

Collector Comments

1 X X Completed

2 X X Completed

3 X X Results in 4 Weeks

4 X X Results in 1 Week
NATIONAL RENEWABLE ENERGY LABORATORY

Implantation of ISC Device for Active-Active Short

Cu side of ISC device interfaces anode, Al side interfaces cathode;

shown here implanted inside a Dow-Kokam 8-Ah pouch cell design.

Photo Credits: Dow Kokam – Ben McCarthy

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NATIONAL RENEWABLE ENERGY LABORATORY

Test Setup for Triggering ISC Implanted in a Cell

• Cell is charged to the 

appropriate SOC.

• Hot plate provides the 

heating source.

• Cell is placed under 

compression (~1.6 psi).

• Al plate between hot plate 

and cell has an embedded 

thermocouple (TC).

• Thermocouple placed cell 

side opposite hot plate.

• Thin foam pad and Lexan 

plate placed between cell top 

and 25-lb weight.

• Thin particulate bag 

encapsulates cell and its top 

TC (not shown for clarity).

Hot plate

Aluminum plate with embedded TC

Cell with ISC device

Thin rubber foam liner

Lexan sheet

25 lbs

TC

Graphic is not to scale

and for illustration only

TC

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NATIONAL RENEWABLE ENERGY LABORATORY

Voltage Response to ISC – Active to Active
NATIONAL RENEWABLE ENERGY LABORATORY

Impedance Model of the ISC Device

Axis symmetry geometry 

Current 

B.C. 

Ground 

B.C.

Property Al-pad Cu-pad Cu-piece

Positive 

current 

collector

Negative

current 

collector

Cathode 

electrode

Anode 

electrode Separator

Electric 

conductivity

[S/m]

3.541x107 5.8x107 5.8x107 3.541x107 5.8x107 5 58 1x10-15

Assuming no interface contact 

resistance between components

Cathode active material is most resistive component

Interface contact resistances must be determined by test

Graphic not drawn to scale
NATIONAL RENEWABLE ENERGY LABORATORY

Al layer of ISC device

Improving Interface Contact Resistance

• Cathode active material contact 

resistance with the pure Al foil 

pad of our ISC is on the order of 

~1 Ω and is driving the resistance 

of the anode-to-cathode short.

• A metallic contaminant pressed into 

the cathode material during 

manufacturing would have much 

better contact resistance, as field 

failures have demonstrated

• Looking at advanced materials 

for improving contact resistances

• Carbon/Polyvinylidenefluoride (PVDF) 

deposited on Al (pictured)

• High-conductivity micro-carbon fibers 

(pictured)

• Bonding Al disc onto the cathode 

active material during electrode 

coating.

Photo courtesy of ESLI

Cathode layer

Cathode layer

Al

Carbon/PVDF 

Photo Credit: NREL – Bobby To

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NATIONAL RENEWABLE ENERGY LABORATORY

Anode-to-Aluminum Current Collector Short

• Used NMP to remove 

cathode coating from 

center portion of doublesided cathodes.

• Replaced thin Al pad on 

ISC device with one that 

matches the thickness of 

the cathode coating.

• Dry conductance tests 

indicate ~150 mohms 

from Al current collector to 

Cu current collector using 

an activated ISC device.

• Implanted a ISC device in 

a cell at DK labs. 

Photo Credit: NREL – Yoon Seok Jung

14

Separator

Positive current collector (Al)

Cathode electrode

ISC device

Wax

Negative current collector (Cu) Anode electrode

Graphic is not to scale

and for illustration only
NATIONAL RENEWABLE ENERGY LABORATORY

Anode-to-Al Short

DK lightly glued the custom ISC device to 

the modified cathode, lines up the separator 

hole with a template to center the separator 

hole, and then allowed stacking to proceed.

Photo Credits: Dow Kokam – Ben McCarthy

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NATIONAL RENEWABLE ENERGY LABORATORY

Nominal Capacity Cycling after Implantation

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

0 20 40 60 80 100 120 140

Voltage (Volts)

Time (Minutes)

Cell 11 Cell 12 Cell 13

4 amp discharge voltage curves from initial cycle data.

Dow Kokam 8 Ah pouch cells with anode-Al ISC device.

Device has negligible impact on cell performance.

Cell 11 capacity = 7.862 Ah

Cell 12 capacity = 7.864 Ah

Cell 13 capacity = 7.789 Ah

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NATIONAL RENEWABLE ENERGY LABORATORY

0

20

40

60

80

100

120

3.85

3.9

3.95

4

4.05

4.1

4.15

0 5 10 15 20 25 30 35 40 45 50

Temperature (

oC)

Voltage (Volts)

Time, Minutes

Voltage and Temperature Response to ISC

Detected a 55°C temperature rise in 80 seconds

Cell temperature on side of ISC device.

OCV

Hot plate temperature -

turned off here.

On demand ISC – anode to Al trigger device

DK 8 Ah pouch cell

Isoc = 100%, 57oC ISC trigger temperature

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NATIONAL RENEWABLE ENERGY LABORATORY

Results of Destructive Physical Analysis

Anode-Al short without any improvements to 

interface contact resistances

Severe heat-affected zones in eight 

electrode layers in vicinity of ISC 

device and on inside of pouch laminate 

side near short.

Tabs stayed intact.

Internal Short Circuit Device

Photo Credit: Dow Kokam – Ben McCarthy

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NATIONAL RENEWABLE ENERGY LABORATORY

Unfolding the cell after 

the Anode-Al short 

Anode and cathode 

sandwiching the ISC 

were not yet 

separated to prevent 

damage.

Destructive Physical Analysis Evidence (cont.)

Photo Credits: Dow Kokam – Ben McCarthy

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NATIONAL RENEWABLE ENERGY LABORATORY

Observations 

• A small, low profile, flexible, and implantable device has been 

demonstrated to be reliable in triggering on-demand internal short circuits

• PCM activation has never failed to activate.

• Anode-Al short caused a rapid 55 C temperature rise in an 8-Ah Dow-Kokam cell 

design, but did not result in thermal runaway.

• High contact resistances prevented hard shorts and thermal runaway.

• Currently investigating several very promising redesign options to lower key interface 

resistances.

• Although thermal runway was not achieved, much was learned from ISC 

device/cell component impedance measurements

• Cathode active material-to-device interface has highest impedance.

• Suggests that metallic particle contamination after electrode calendaring may only yield 

high/med impedance shorts if only bridging anode-to-cathode active materials.

• Anode-to-Al short yielded lower impedance shorts

• As predicted previously by others14, this type of short is more likely to drive cell into 

thermal runaway.

• ~150 mohm short at ISC device caused significant damage in eight electrode layers and 

the inside of closest pouch layer.

14. S. Santhanagopalan et al., J. Power Sources (2009)

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NATIONAL RENEWABLE ENERGY LABORATORY

Summary and Planned Work

• NREL/NASA has developed a small, low profile device for simulating internal 

short circuit (ISC) in Li-Ion cells.

• An patent application has been filed for the ISC device. 

• To date, anode-cathode and anode-Al short-circuit cases have been tested 

in coin and stacked pouch cells

• The ISC device has shown great potential to produce results relevant to field 

failures caused by internal cell defects

– Evaluation ISC response of a cell no longer has to rely on less relevant crush tests.

– Results have promise to guide and focus cell production line defect and contamination 

mitigation measures.

– Comparison of the abuse tolerance of various cell designs will be possible.

• Planned Work:

• With further maturation, we plan to further test the effectiveness of the ISC 

device in triggering a thermal runaway

• Test Cathode-to-Cu and Al-Cu collector shorts in stacked cells 

• Implant and test ISC device in 18650 Li-Ion cell designs 

• Test the effectiveness of battery managements systems in preventing collateral 

damage to cells neighboring one with an internal short circuit.

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NATIONAL RENEWABLE ENERGY LABORATORY

Acknowledgments

26

• Funding provided through Energy Storage Research 

and Development Program at the Office of Vehicle 

Technologies in the U.S. Department of Energy.

• Dave Howell

• Dow-Kokam for being willing to be the first to support us 

with evaluation of NREL ISC device

• Support and contributions by NREL colleagues

• Gi-Heon Kim

• Kyu-Jin Lee

• Shriram Santhanagopalan 

• John Ireland