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Lithium-Ion Battery Storage and Use Hazards

R. Thomas Long, P.E.

Mike Kahn, Ph.D.

Celina Mikolajczak, P.E.

February 28, 2013

SUPDET 2013 Orlando, FL

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Acknowledgements

The authors would like to thank:

The FPRF and the project sponsors for giving Exponent the opportunity to complete this work

The project Technical Panel for their many comments and suggestions

The Property Insurance Research Group (PIRG)

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Today’s Topics

Project History

Brief Technology Review

Brief Failure Incidents and Modes

Brief Battery Life Cycle / Applications Hazard Assessment

Survey Results

General Research Approach

Battery Acquisition

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Introduction

Phase 1: Lithium Ion Hazard and Use Assessment http://www.nfpa.org/assets/files/PDF/Research/RFLithiumIonBatteriesHazard.pdf

Phase 2:

A: Survey

B1: Test Planning and battery/cell acquisition/characterization

B2: Full scale testing (FM global)

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What Does Li-Ion Mean?

Li-ion refers to a family of battery chemistries

Negative (anode) and positive (cathode) electrode materials serve as hosts for lithium ions:

Ions intercalate into the electrode materials

No free lithium metal in a Li-ion cell

Rechargeable

No “standard” Li-ion cell

Electrolyte = flammable

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What is a Li-ion Cell?

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What is a Li-ion Battery?

A Li-ion battery pack contains

An enclosure

One or more cells

Protection electronics

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Cell Thermal Runaway

1. Cell internal temperature increases

2. Cell internal pressure increases

3. Cell undergoes venting

4. Cell vent gases may ignite

5. Cell contents may be ejected

6. Cell thermal runaway may propagate to adjacent cells

Cell

windings

Open center

of cell

Blockage in

center of cell

Pressure

buildup at

base

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Thermal Runaway- How do you get there

Thermal Abuse: The most direct way to exceed the thermal stability limits of a Li-ion cell is to subject it to external heating

Mechanical Abuse: Mechanical abuse of cells can cause shorting between cell electrodes, leading to localized cell heating that propagates to the entire cell and initiates thermal runaway;

Electrical Abuse: Overcharge, External Short Circuit, Over-discharge

Internal Cell Faults: For commercial Li-ion battery packs with mature

protection electronics packages, the majority of thermal runaway

failures in the field are caused by internal cell faults

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Battery Life Cycle Hazards

Key Finding: Warehouse setting was frequent throughout

lifecycle of batteries

Warehouse setting

Failure modes:

Mechanical abuse – cells being crushed, punctured, dropped

Electrical abuse – short circuiting improperly packaged cells/ packs

Thermal abuse – external fire

Internal fault – unlikely unless cells being charged

Mitigation:

Cells/packs usually stored at reduced states of charge (50% SOC or less)

Cells and packs can be contained in packaging to prevent mechanical and external short circuit damage

Fire suppression strategies

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Knowledge Gaps

Gap 1: Leaked Electrolyte & Vent Gas Composition

Gap 2: Sprinkler Protection criteria for Li-ion Cells

Gap 3: Effectiveness of Various Suppressants

Gap 4: Post – Fire Cleanup Issues

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Gap 2: Sprinkler Protection

2.1: At present there is no fire protection suppression strategy for

Li-ion cells

2.1a: Bulk packaged Li-ion cells

2.1b: Large format Li-ion cells

2.1c: Li-ion cells contained in or packed with equipment

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Gap 2: Overview

Current infrastructure in most occupancies includes the ability to provide water based fire protection systems

Currently not known if water is the most appropriate extinguishing medium for Li-ion batteries

NFPA 13 does not provide a specific recommendation for the protection of or fire protection strategies for Li-ion cells or complete batteries

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Gap 2: Sprinkler Protection for Li-Ion

NFPA 13 ‘battery” Commodity Classifications

NFPA 13 provides a list of commodity classes for various

commodities in Table A.5.6.3.

Dry cells (non-lithium or similar exotic metals) packaged in cartons: Class I (for example alkaline cells);

Dry cells (non-lithium or similar exotic metals) blister packed in cartons: Class II (for example alkaline cells);

Automobile batteries – filled: Class I (typically lead acid batteries with water-based electrolyte);

Truck or larger batteries, empty or filled Group A Plastics (typically lead acid batteries with water-based electrolyte);

Li-ion chemistries are not included

Full Scale testing appropriate

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Gap 2: Sprinkler Protection for Li-Ion

For full scale tests needed to define

Commodities

Cell chemistry

Cell size / form factor

Cell SOC

Packaging configuration

Storage geometries and arrangments

Full scale tests of every cell type / configuration is not practical

Select a “most typical case”

Purchasing commodities for testing is expensive

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Survey

Conducted in 2012

Responders were typically engaged in:

Manufacturing

Research

Recycling

Almost all responders stored batteries, cells, or devices with batteries/cells.

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Survey Responses Summary

Battery Types at the Surveyed Facilities: Cylindrical cells

were the most common form factor. Small format was the most

common size.

Tasks Carried Out at Facilities Surveyed: Most of the

responding facilities were engaged in the storage of cells, battery

packs or devices.

Packaging of Received Batteries: Cells typically arrive in

cardboard boxes. These boxes may be on wooden pallets and/or

encapsulated.

Rack storage type: Movable racks were more common than

fixed racks, and shelves were more likely to be perforated than solid.

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Battery Aquissition

Parameter Power tool 18650 18650 Li-Polymer

Nominal voltage 3.7 V 3.7 V 3.7 V

Nominal capacity 1300 mAh 2600 mAh 2700 mAh

Mass of Cell 42.9 g 47.2 g 50.0 g

Approximate mass of

electrolyte solvent

3.3 g 2.6 g 4.0 g

Cell chemistry Lithium Nickel

Manganese Cobalt

Oxide (NMC)

Lithium Cobalt Oxide

(LCO)

Lithium Cobalt Oxide

(LCO)

Approx. state of charge

(SOC) as received

50% 40% 60%

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Ryobi P104 Power Tool Packs – Overview

18 V, 48 Wh Lithium-Ion power tool packs selected over lower voltage, lower capacity packs in

an effort to maximize the ratio of lithium-ion battery cells to packaging materials

The battery packs measure approximately (5 ½” long) x (3 ¼” wide) x (4 ¼” tall)

Blister packs plus casing presented an appreciable amount of plastics

Onboard “fuel gauge” indicator lights orange, indicating mid state of charge

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Ryobi P104 Power Tool Packs – Construction

Battery pack materials include a protection PCB, spot-welded nickel interconnects, hard plastic

structural elements, flexible rubber elements (rubber feet and internal flexible rubber padding), and

soft foam padding for vibration resistance

Hard injection-molded plastic shell

Rubber feet

Bottom View

Hard plastic frame

Soft foam padding

Protection printed circuit board (PCB) / Battery Management Unit (BMU)

Flexible rubber padding

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Ryobi P104 Power Tool Packs –

Characterization

The unit is constructed using 10 18650 cells in a 5 series, 2 parallel configuration

5 series elements @ 3.7 V nominal = 18.5 V nominal pack voltage

2 parallel elements @ 1300 mAh per cell = 2600 mAh capacity

18.5 V x 2.6 Ah = 48.1 Wh nominal pack energy (Packaging indicates “18 V” / “48 Wh” for simplicity)

The cells are arranged in alternating fashion, thus vent ports (on the positive terminal side) face both sides of the

battery pack. Cell venting would occur on both sides of the pack during overpressure events.

• High-Power Lithium-Ion Cells • Form Factor: 18650 Hard case cylindrical cells • Dimensions: 18 mm x 65.0 mm • Cell enclosure: steel can with shrink wrap • Chemistry: NMC (Lithium Nickel Manganese Cobalt Oxide) • Nominal voltage: 3.7 V • Nominal capacity: 1300 mAh • Approximate assembled weight: 42.9 g • Approximate mass of electrolyte solvent: 3.3 g

(+) side (with vent port) (-) side (no vent port)

Positive terminal and vent port

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Power Tool Packs – SOC

Two battery packs were measured for voltage and capacity

Both battery packs were 18.60 V (corresponding to 3.72 V per series element)

Battery packs are close to the nominal pack voltage of 18.5 V (or nominal cell voltage of 3.7 V)

A battery pack at the nominal voltage usually indicates it is near the halfway point of charge

A fully charged pack would be 21 V (4.2 V x 5 series elements)

State of Charge (SOC) was measured on one cell from each of two battery packs (S/N listed above) using

a standard C/5 rate (0.26 A) constant current discharge until 2.5V was reached

Both cells were determined to be close to 50% SOC

V of NFPA-sanyo-18650.015

V of NFPA-sanyo-18650.008

Capacity/mAh

6005004003002001000

Voltage/V

4.2

4.1

4

3.9

3.8

3.7

3.6

3.5

3.4

3.3

3.2

3.1

3

2.9

2.8

2.7

2.6

2.5

Discharge Capacity Pack S/ CS12233D430739 – 667 mAh (50% SOC) CS12271N430014 – 652 mAh (49% SOC)

Initial voltage 3.72 V

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Ryobi Packs – Sanyo 18650 Cell Disassembly

Electrodes are in a jelly roll configuration,

typical of 18650 cells

One cell was disassembled and the positive

electrode was subjected to energy

dispersive X-ray spectroscopy (EDS) to

assess cell chemistry

Cell chemistry is consistent with NMC

(lithium nickel manganese cobalt oxide)

chemistry, i.e. Li(NixMnyCoz)O2 where x, y,

and z can vary depending on manufacturer’s

formula

Negative electrode (on Cu foil)

Positive electrode (on Al foil)

Separator

Separator

Mn

Co

Ni

Positive cell tab

EDS Spectrum

O

Steel can

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18650 Cells – Characterization

• 18650 Lithium-Ion Cells • Form Factor: Hard case cylindrical cell

(18 mm diameter x 65.0 mm) • Cell enclosure: steel can with shrink wrap • Chemistry: LCO (Lithium cobalt oxide) • Nominal voltage: 3.7 V • Nominal capacity: 2600 mAh • Approximate assembled weight: 47.2 g • Approximate mass of electrolyte solvent: 2.6 g

Jelly roll in cell can

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2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

0 0.2 0.4 0.6 0.8 1 1.2

Vo

ltag

e (

V)

Capacity (Ah)

18650 Channel 8

18650 Channel 15

18650 Cells – State of charge (SOC)

Two cells were measured for voltage and capacity

Both cells were 3.74 V, close to the nominal cell voltage of 3.7 V

A battery pack at the nominal voltage usually indicates it is near the halfway point of charge

A fully charged cell would be 4.2 V

State of Charge (SOC) was measured on two cells using a standard C/5 rate (0.52 A) constant current

discharge until 3.0 V was reached

Discharge Capacity Cell capacities: 1.05 Ah (40% SOC) 1.05 Ah (40% SOC)

Initial voltage 3.74 V

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18650 Cells – Cell Disassembly

Electrodes are in a jelly roll

configuration, typical of 18650 cells

One 18650C was disassembled and

the positive electrode was subjected

to energy dispersive X-ray

spectroscopy (EDS) to assess cell

chemistry

Cell chemistry is consistent with LCO

(lithium cobalt oxide) chemistry, i.e.

LiCoO2

Steel can

Negative electrode (on Cu foil)

Positive electrode (on Al foil)

Separator

Separator

O

Co EDS Spectrum

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Li-Polymer Cells – Characterization

• Lithium-Polymer Cells • Form Factor: Li-polymer (soft pack) cell • Dimensions: 6 mm thick x 41 mm x 99 mm • Cell enclosure: aluminum foil with polymer coating • Electrode configuration: jelly roll (as opposed to

stacked) • Chemistry: LCO (Lithium cobalt oxide) • Nominal voltage: 3.7 V • Nominal capacity: 2700 mAh • Approximate assembled weight: 50.0 g • Approximate mass of electrolyte solvent: 4.0 g

Coated aluminum pouch

Cell windings (“Jelly roll”)

Cell enclosure is aluminum foil coated with polymer, and is designed to be

electrically neutral and insulated

+ tab

– tab

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2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

0 0.5 1 1.5 2

Vo

ltag

e (

V)

Capacity (Ah)

Pouch 9I19

Pouch 9H27_1

Li-Polymer Cells – SOC

Two cells were measured for voltage and capacity

Both cells were 3.84 V

Battery packs are close to the nominal cell voltage of 3.7 V

A battery pack at the nominal voltage usually indicates it is near the halfway point of charge

A fully charged cell would be 4.2 V

SOC was measured on two cells using a standard C/5 rate (0.54 A) constant current discharge until 3.0 V

was reached

Discharge Capacity Cell markings: 9H27 – 1.62 Ah (60% SOC) 9I19 – 1.66 Ah (61% SOC)

Initial voltage 3.84 V

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Li-Polymer Cells – Cell Disassembly

Electrodes are in a jelly roll

configuration, as opposed to stacked

electrode design

One Li polymer cell was disassembled

and the positive electrode was

subjected to energy dispersive X-ray

spectroscopy (EDS) to assess cell

chemistry

Cell chemistry is consistent with LCO

(lithium cobalt oxide) chemistry, i.e.

LiCoO2

Al Pouch

Negative electrode (on Cu foil)

Positive electrode (on Al foil)

Separator

Separator

O

Co EDS Spectrum

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Flammability Characterization

Full scale tests

Limited quantities of batteries/cells

Rack storage arrangement

Free burn/external ignition source

Hard and soft case batteries with similar energy

densities

Battery packs with appreciable plastics

Due to costs, tests required an unique approach to full

scale tests – FM Global – reduced commodity testing