Investigation on effect of phase change material on the thermal runaway of lithium-ion battery and exploration of flame retardancy improvement

Thermal safety is important for the process of storage and utilization of lithium-ion battery. Once battery thermal runaway (TR) happens, accidents are difficult to avoid. As a cooling medium for battery thermal management, phase change material (PCM) can effectively maintain the temperature under normal operations. However, the flammability of PCM makes it doubtful to work safely under extreme conditions like TR. Herein, several sets of TR experiments have been conducted on 18650 batteries covered without and with different PCMs. Paraffin PCM (PPCM) and composite PCM (CPCM) are considered to explore their effects on TR. Results demonstrate that PPCM delays the onset of TR by 277 s and lowers the battery temperature utilizing its heat absorption while CPCM has little effect. However, flammable PPCM increases the heat release significantly which brings great fire risk. Based on the foregoing, a flame-retarded PPCM mixed with hydroxide flame-retardant proved to relieve the adverse effects of PPCM as well as maintain the performance for inhibiting TR. Results show that the addition of flame retardants reduces the peak heat release rate from 29 kW to 15.5 kW, which gives guidance in the process safety assurance and fire protection design in a real engineering application of battery thermal management.