A critical review of lithium-ion battery safety testing and standards

The safety of lithium-ion batteries (LiBs) is a major challenge in the development of large-scale applications of batteries in electric vehicles and energy storage systems. With the non-stop growing improvement of LiBs in energy density and power capability, battery safety has become even more significant. Reports of accidents involving LiBs have been communicated showing evidence of fire and explosions of battery systems (e.g., electric scooter charging overnight). Indeed, when electrochemical systems such as LiBs operate outside their normal range of operation, thermal runaway (TR) occurs leading to safety hazards that include fire, smoke and in some cases explosion. In battery safety research, TR is the major scientific problem and battery safety testing is the key to helping reduce the TR threat. Thereby, this paper proposes a critical review of the safety testing of LiBs commencing with a description of the temperature effect on LiBs in terms of low-temperature, high-temperature and safety issues. After describing the fundamentals of the origin of TR in LiBs, recent investigations of battery abuse testing have been summarized and broken down into three categories corresponding to the three main abuse scenarios: electrical, thermal and mechanical abuse. Overcharging and thermal abuse testing remains the most documented battery safety tests in the literature and the most observed reasons for battery safety accidents. Finally, LiB safety tests have been analysed in a recent overview of international battery standards (e.g. IEC 62660-2, UL 2580, SAE J2464) and the main abuse test protocols for getting certified are described. The most important ones are overcharge, fire propagation or collision. However, standardisation of some safety tests (e.g., the internal short-circuit) is still lacking and needs to be improved for reducing the TR hazard in LiB applications.