1 Lithium-Ion Battery Storage and Use Hazards R. Thomas Long, P.E. Mike Kahn, Ph.D. Celina Mikolajczak, P.E. 1100034.000 C0T0 0213 RTL1 February 28, 2013 SUPDET 2013 Orlando, FL
1100034.000 C0T0 0213 RTL1 2 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)
1100034.000 C0T0 0213 RTL1 3 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
4 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) 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 5 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
1100034.000 C0T0 0213 RTL1 6 What is a Li-ion Cell?
1100034.000 C0T0 0213 RTL1 7 What is a Li-ion Battery? A Li-ion battery pack contains An enclosure One or more cells Protection electronics
8 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 Blockage in center of cell Open center of cell Pressure buildup at base 1100034.000 C0T0 0213 RTL1
9 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 1100034.000 C0T0 0213 RTL1
10 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 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 11 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
12 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 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 13 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
14 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 1100034.000 C0T0 0213 RTL1
15 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 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 16 Survey Conducted in 2012 Responders were typically engaged in: Manufacturing Research Recycling Almost all responders stored batteries, cells, or devices with batteries/cells.
1100034.000 C0T0 0213 RTL1 17 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.
1100034.000 C0T0 0213 RTL1 18 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 Cell chemistry Approx. state of charge (SOC) as received 3.3 g 2.6 g 4.0 g Lithium Nickel Manganese Cobalt Oxide (NMC) Lithium Cobalt Oxide (LCO) 50% 40% 60% Lithium Cobalt Oxide (LCO)
19 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 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 20 Protection printed circuit board (PCB) / Bottom View Ryobi P104 Power Tool Packs Construction Battery Management Unit (BMU) Hard injection-molded plastic shell Soft foam padding Flexible rubber padding Rubber feet 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
1100034.000 C0T0 0213 RTL1 21 Ryobi P104 Power Tool Packs (+) side (with vent port) (-) side (no vent port) Characterization Positive terminal and vent port 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.
Voltage/V 1100034.000 C0T0 0213 RTL1 22 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 0 Power Tool Packs SOC 100 Discharge Capacity Initial voltage 3.72 V 200 300 400 Capacity/mAh 500 600 Pack S/ CS12233D430739 667 mah (50% SOC) CS12271N430014 652 mah (49% SOC) V of NFPA-sanyo-18650.015 V of NFPA-sanyo-18650.008 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
23 Ryobi Packs Sanyo 18650 Cell Disassembly Separator Positive cell tab Separator Positive electrode (on Al foil) Negative electrode (on Cu foil) Steel can Electrodes are in a jelly roll configuration, typical of 18650 cells Mn EDS Spectrum 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(Ni x Mn y Co z )O 2 where x, y, and z can vary depending on manufacturer s formula O Co Ni 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 24 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
Voltage (V) 1100034.000 C0T0 0213 RTL1 25 18650 Cells State of charge (SOC) 4.3 4.1 3.9 3.7 Discharge Capacity Initial voltage 3.74 V 18650 Channel 8 18650 Channel 15 Cell capacities: 1.05 Ah (40% SOC) 1.05 Ah (40% SOC) 3.5 3.3 3.1 2.9 2.7 2.5 0 0.2 0.4 0.6 0.8 1 1.2 Capacity (Ah) 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
26 18650 Cells Cell Disassembly Separator Separator Positive electrode (on Al foil) Steel can Negative electrode (on Cu foil) 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. LiCoO 2 O EDS Spectrum Co 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 27 Li-Polymer Cells Characterization + tab Coated aluminum pouch tab Cell windings ( Jelly roll ) 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
Voltage (V) 1100034.000 C0T0 0213 RTL1 28 Li-Polymer Cells SOC 4.3 4.1 3.9 Discharge Capacity Initial voltage 3.84 V Pouch 9I19 Pouch 9H27_1 Cell markings: 9H27 1.62 Ah (60% SOC) 9I19 1.66 Ah (61% SOC) 3.7 3.5 3.3 3.1 2.9 2.7 2.5 0 0.5 1 1.5 2 Capacity (Ah) 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
29 Li-Polymer Cells Cell Disassembly Separator Al Pouch Separator Negative electrode (on Cu foil) Positive electrode (on Al foil) 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. LiCoO 2 O EDS Spectrum Co 1100034.000 C0T0 0213 RTL1
1100034.000 C0T0 0213 RTL1 30 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