Lithium-Ion Battery Storage and Use Hazards

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Lithium-Ion Battery Storage and Use Hazards
R. Thomas Long, P.E.
Mike Kahn, Ph.D.
Celina Mikolajczak, P.E.
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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
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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
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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:
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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
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Gap 1:
Gap 2:
Gap 3:
Gap 4:
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Leaked Electrolyte & Vent Gas Composition
Sprinkler Protection criteria for Li-ion Cells
Effectiveness of Various Suppressants
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
Onboard “fuel gauge” indicator lights orange,
indicating mid state of charge
 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
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Ryobi P104 Power Tool Packs – Construction
Hard injection-molded
plastic shell
Protection printed circuit board (PCB) /
Battery Management Unit (BMU)
Soft foam padding
Rubber feet
Bottom View
Flexible rubber padding
Hard plastic
frame
 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
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Ryobi P104 Power Tool Packs –
(+) side (with vent port)
(-) side (no vent port)
Characterization
Positive terminal
and vent port
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•
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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
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.
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Voltage/V
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Power Tool Packs – SOC
Discharge Capacity
Pack S/
CS12233D430739 – 667 mAh (50% SOC)
CS12271N430014 – 652 mAh (49% SOC)
4.2
4.1
V of NFPA-sanyo-18650.015
V of NFPA-sanyo-18650.008
Initial voltage 3.72 V
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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
0
100
200
300
400
Capacity/mAh
500
600
 Two battery packs were measured for voltage and capacity
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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
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Ryobi Packs – Sanyo 18650 Cell Disassembly
Separator
Separator
Positive electrode (on Al foil)
Positive cell tab
Steel
can
Negative electrode (on Cu foil)
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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
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EDS Spectrum
Mn
O
Co
Ni
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18650 Cells – Characterization
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Jelly roll in cell can
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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
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18650 Cells – State of charge (SOC)
Discharge Capacity
4.3
Cell capacities:
1.05 Ah (40% SOC)
1.05 Ah (40% SOC)
Initial voltage 3.74 V
4.1
18650 Channel 8
3.9
18650 Channel 15
Voltage (V)
3.7
3.5
3.3
3.1
2.9
2.7
2.5
0
0.2
0.4
0.6
Capacity (Ah)
0.8
1
1.2
 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
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18650 Cells – Cell Disassembly
Separator
Separator
Positive electrode (on Al foil)
Negative electrode (on Cu foil)
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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
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EDS Spectrum
O
Co
Steel
can
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Li-Polymer Cells – Characterization
Coated
aluminum pouch
+ tab
– tab
Cell windings (“Jelly roll”)
•
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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
 Cell enclosure is aluminum foil coated with polymer, and is designed to be
electrically neutral and insulated
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Li-Polymer Cells – SOC
Discharge Capacity
4.3
Cell markings:
9H27 – 1.62 Ah (60% SOC)
9I19 – 1.66 Ah (61% SOC)
Initial voltage 3.84 V
4.1
Pouch 9I19
3.9
Pouch 9H27_1
Voltage (V)
3.7
3.5
3.3
3.1
2.9
2.7
2.5
0
0.5
1
Capacity (Ah)
1.5
2
 Two cells were measured for voltage and capacity
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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
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Li-Polymer Cells – Cell Disassembly
Al
Pouch
Separator
Separator
Negative electrode (on Cu foil)
Positive electrode (on Al foil)
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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
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EDS Spectrum
O
Co
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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
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