Safety studies of Li-ion battery materials by accelerated rate calorimetry

Exothermic reactions of selected Li-ion battery was studied with accelerated rate calorimetry (ARC®). Liquid electrolyte EC/DMC (1:1)-LiPF 6 starts exothermic reactions at 225°C, which results in thermal runaway. The stability of gel polymer electrolytes, consisting of P(VDF-HFP) and EC/PC (1:1)-LiPF 6 , is not significantly different from the liquid system. Solid polymer electrolytes made of high molecular weight PEO and LiClO 4 or LiPF 6 salts showed the highest thermal stability in the study. The onset temperatures of exothermic reactions of cathode materials in EC/DMC-LiPF 6 electrolyte are in the order of LiCoO 2 > LiMn 2 O 4 ≃ LiNi 0.8 Co 0.2 O 2 . However, no significant difference was observed when testing these cathode materials without other battery components present. Fully lithiated graphite anodes proved very low thermal stability, and observed onset temperature of exothermic reactions 75C followed by catastrophic self-heating rates in the 1000°C/minute.