As one of the most promising new energy sources, the lithium-ion battery (LIB) and its associated safety concerns have attracted great research interest. Herein, a comprehensive review on the thermal hazards of LIBs and the corresponding countermeasures is provided. In general, the thermal hazards of the LIB can be caused or aggravated by several factors including physical, electrical and thermal factors, manufacturing defect and even battery aging. Due to the activity and combustibility of traditional battery components, they usually possess a relatively high thermal hazard and a series of side reactions between electrodes and electrolytes may occur under abusive conditions, which would further lead to the thermal failure of LIBs. Besides, the thermal hazards generally manifest as the thermal runaway behaviors such as high-temperature, ejection, combustion, explosion and toxic gases for a single battery, and it can even evolve to thermal failure propagation within a battery pack. To decrease these hazards, some countermeasures are reviewed including the application of safety devices, fire-retardant additives, battery management systems, hazard warnings and firefighting should a hazard occur.

A lithium-ion battery (LIB) may experience overcharge or over-discharge when it is used in a battery pack because of capacity variation of different batteries in the pack and the difficulty of maintaining identical state of charge (SOC) of every single battery.

This study investigates the effectiveness of different wrapping materials, namely aerogel felt, thermal conductive gel, and two phase change materials (PCMs) in mitigating thermal runaway in lithium-ion batteries. The experimental results reveal that all the materials tested delay the onset of thermal runaway and safety valve rupture compared to unwrapped batteries. Specifically, aerogel felt and thermal conductive gel offer substantial thermal runaway inhibition, delaying the safety valve rupture time by 97 and 99 s, respectively. PCM-1 demonstrates a delay in safety valve rupture but has a limited impact on the onset of thermal runaway. Among all materials, thermal conductive gel shows the most significant impact, postponing both safety valve rupture and thermal runaway onset. In contrast, the PCMs exhibit relatively weaker effects. Furthermore, batteries wrapped in aerogel felt produce the highest CO concentration during thermal runaway, reaching 3,658 ppm. The maximum mass loss rate of the batteries varies with the wrapping material, ranging from 20.1 to 68.5 g/s, with the unwrapped batteries exhibiting the highest loss rate. Overall, the results suggest that thermal conductive gels and phase change materials improve the safety and emergency response of lithium-ion batteries under extreme conditions, with the thermal conductive gel showing the most promising results in delaying both safety valve rupture and thermal runaway.