Enhancing lithium-ion battery pack safety: Mitigating thermal runaway with high-energy storage inorganic hydrated salt/expanded graphite composite

Fire and explosion incidents caused by thermal runaway (TR) in lithium-ion batteries (LIBs) have severely threatened human lives and properties. In this study, we propose an inorganic hydrated salt/expanded graphite composite (TCM40/EG) that integrates phase change and thermochemical heat storage for thermal management and TR suppression in LIB packs. TCM40/EG melts at 35.2 °C and decomposes within the range of 87.1–112 °C, providing a significant thermal energy storage capacity of 1276 kJ/kg. Therefore, it is efficient for thermal management and TR suppression of batteries. During a charge/discharge cycle, the maximum temperature and temperature difference of a LIB pack were restricted to below 36 °C and 2.5 °C, respectively. Over 10 consecutive cycles, the corresponding limits were below 50 °C and 5 °C. The temperature of the triggered cell was suppressed to 305 °C, while the temperatures of the other batteries remained below 95 °C during the occurrence of TR. Thus, TR propagation was easily prevented. However, TR propagation was observed in battery packs that utilized aerogel or paraffin composites (OP44/EG CPCM). While aerogel did delay the TR propagation to some extent, it was unable to completely inhibit it. As a result, the entire battery pack experienced TR consecutively. OP44/EG CPCM was effective in reducing the temperature of the battery pack. However, its enthalpy was found to be insufficient in successfully suppressing TR propagation. As a result, TR was triggered in three adjacent batteries within an extremely short period. The results suggest that TCM40/EG offers notable advantages over aerogels and OP44/EG CPCM in preventing TR propagation. Furthermore, it is suggested that effectively dissipating the heat released from the triggered battery may be more effective than simply blocking it. Additionally, materials with high enthalpy, appropriate phase change, and decomposition temperatures are significant in suppressing TR propagation. Therefore, the proposed inorganic hydrated salt composite, which demonstrates good thermal management effects and TR suppression performance, may provide valuable insights for the design of safer lithium-ion batteries.