A comparative study of thermal runaway of commercial lithium ion cells

Thermal runaway of three lithium ion cells (“A” - NCA/Graphite, “B” - LFP/Graphite, “C” - NCA/LTO) at 0%, 50%, and 100% state of charge (SOC) is studied by Accelerating Rate Calorimetry (ARC). Thermal behaviour of harvested positive and negative electrodes at three SOC (0%, 50%, and 100%) is analyzed using Differential Scanning Calorimetry (DSC). Thermal stability of recovered separators is also investigated by DSC. Harvested electrodes and separators are studied alone and in contact with a liquid electrolyte. The thermal behaviour of each component and its contribution is quantified and thoroughly discussed. A crucial negative impact of the state of charge and presence of highly flammable liquid electrolyte on the thermal instability of the investigated cells and “electrode - electrolyte” systems is clearly revealed. Among studied cells, LiFePO4/Graphite one is the safest due to intrinsic thermal stability of lithium iron phosphate LiFePO4 based cathode and despite the fact of using a microporous polyolefin separator with limited thermal stability.