A review on passive and active strategies of enhancing the safety of lithium-ion batteries

Lithium-ion battery (LIB) becomes the dominant candidate for electric vehicles (EVs) and energy storage systems (ESSs); nevertheless, as its popularization, the number of safety (fire) accidents regarding with LIB thermal runaway increases, undermining the public confidence. Safety turns into one of the main concerns in the widespread usage of LIBs. In this review paper, various faults in LIBs which have a potential risk leading to safety accidents are scrutinized firstly, followed by the presentation of recent progress in strategies of improving the safety of LIBs. Faults in large-scale LIB-based systems like EVs and ESSs for power grids include battery faults, sensor faults and actuator faults. The battery faults can be triggered by mechanical abuse, electrical abuse, thermal abuse as well as aging or degradation. This paper classifies the safety strategies into active safety strategies and passive safety strategies. Passive safety strategies pursue inherent safety in LIBs via material modification and alleviate the hazard level of faults through taking timely countermeasure like fire suppression or extinguishment once the LIB fire accident occurs. On the contrary, the active safety strategies aim to prevent the abuse conditions from developing into uncontrollable thermal runaway or fire accidents by effective state estimation and monitoring, fault diagnosis and early warning, thermal management, equalization technology, etc.