Experimental investigation on thermal management system with flame retardant flexible phase change material for retired battery module

Phase change material (PCM) cooling technology has attracted significant attention as an efficient battery thermal management strategy owing to its promising performance, especially in retired battery modules with the amplification of inconsistency and security risk generation. However, it has some limitations in practical applications, including the leakage of phase change ingredients, low thermal conductivity, and high flammability. Herein, a novel paraffin (PA)/EVA grafted with maleic anhydride (EVA-g-MAH)/expanded graphite (EG)/melamine (MA)/triphenyl phosphate (TPP) composite phase change material (MTPCM) was successfully prepared and utilised in a retired battery module. MTPCM3 with an MA/TPP ratio of 10/15 achieved multiple functions, such as leakage-proof capability, superior high thermal conductivity, and prominent flammable retardant performance (UL94-V0). Particularly, MTPCM demonstrated excellent total heat release (THR) and total smoke production (TSP) of 193.8 MJ/m2 and 7.8 m2, respectively. Furthermore, the application of MTPCM3 in 32650-type retired lithium iron phosphate battery modules effectively controlled the maximum temperature below 50 °C and maintained a temperature difference within 5 °C at a 3C discharge rate; this significantly prevented the heat accumulation of batteries and improved the temperature consistency of the retired battery during the long cycling process. This work suggests an efficient approach toward exploiting a multifunctional PCM for thermal management and energy storage fields.