Further study of the intrinsic safety of internally shorted lithium and lithium-ion cells within methane-air

Abstract

National Institute for Occupational Safety and Health (NIOSH) researchers continue to study the potential for lithium and lithium-ion battery thermal runaway from an internal short circuit in equipment for use in underground coal mines. Researchers conducted cell crush tests using a plastic wedge within a 20-L explosion-containment chamber filled with 6.5% CH4-air to simulate the mining hazard. The present work extends earlier findings to include a study of LiFePO4 cells crushed while under charge, prismatic form factor LiCoO2 cells, primary spiral-wound constructed LiMnO2 cells, and crush speed influence on thermal runaway susceptibility. The plastic wedge crush was a more severe test than the flat plate crush with a prismatic format cell. Test results indicate that prismatic Saft MP 174565 LiCoO2 and primary spiral-wound Saft FRIWO M52EX LiMnO2 cells pose a CH4-air ignition hazard from internal short circuit. Under specified test conditions, A123 systems ANR26650M1A LiFePO4 cylindrical cells produced no chamber ignitions while under a charge of up to 5 A. Common spiral-wound cell separators are too thin to meet intrinsic safety standards provisions for distance through solid insulation, suggesting that a hard internal short circuit within these cells should be considered for intrinsic safety evaluation purposes, even as a non-countable fault. Observed flames from a LiMnO2 spiral-wound cell after a chamber ignition within an inert atmosphere indicate a sustained exothermic reaction within the cell. The influence of crush speed on ignitions under specified test conditions was not statistically significant.

Internal short circuit and accelerated rate calorimetry tests of lithium-ion cells: Considerations for methane-air intrinsic safety and explosion proof/flameproof protection methods

“…The plastic wedge produced internal short circuits for all crush tests attempted under the NIOSH study reported here and previously (Dubaniewicz and DuCarme, 2013, 2014). All of these plastic wedge tests used only a fraction of the force specified for the UL flat plate crush test.…”

“…For example, LiSOCl 2 cells with a spiral wound construction may contain thin separator materials that are susceptible to internal short circuit failure modes for intrinsic safety evaluation purposes (Dubaniewicz and DuCarme, 2014). Exposure to flame temperatures within explosion proof or flameproof enclosures is another potential ignition mechanism for LiSOCl 2 cells of any construction.…”

“…Efforts to develop methods to induce an internal short circuit with a plastic wedge inside the 20-L chamber containing 6.5% CH 4 -air were described previously (Dubaniewicz and DuCarme, 2013, 2014). Fig.…”

“…Previous phases of the study (Dubaniewicz and DuCarme, 2013, 2014) demonstrated a potential methane (CH 4 )-air ignition hazard from internal short circuit within selected Li-ion secondary and lithium primary cells, and a potentially safer Li-ion secondary cell that uses a lithium iron phosphate (LiFePO 4 ) cathode chemistry to weaken exothermic reactions within the cell. The potential for ambient explosive atmosphere ignition by li-ion cell thermal runaway was described in terms of cell chemistry (lithium cobalt oxide (LiCoO 2 ) for example), and spiral wound construction with a thin separator (Figs.…”

Study of temperature classification, spark ignition and drop test assessment on secondary cells for intrinsically safe equipment for explosive atmospheres

“…Barnett et al asserted that Li‐ion battery's safety issues are not met with the same scientific and technical rigor when applied with Li‐ion technology. Doughty and Roth and Thomas and Josheph proposed that safety is often a property which determined after the development phase of Li‐ion technology, and that safety and thermal stability should become a prime consideration in the initial development. Roth and Orendorff reviewed research of nonflammable electrolytes for cell due to temperature and evaluation of temperature is required.…”