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% CH(4)-air to simulate the mining hazard. The present work extends earlier findings to include a study of LiFePO(4) cells crushed while under charge, prismatic form factor LiCoO(2) cells, primary spiral-wound constructed LiMnO(2) 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 LiCoO(2) and primary spiral-wound Saft FRIWO M52EX LiMnO(2) cells pose a CH(4)-air ignition hazard from internal short circuit. Under specified test conditions, A123 systems ANR26650M1A LiFePO(4) 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 LiMnO(2) 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.