Investigation on overcharge-caused thermal runaway of lithium-ion batteries in real-world electric vehicles

Overcharge is one of the most typical triggers leading to battery thermal runaway during real-world vehicular operation. An in-depth exploration of the real-scenario-oriented failure mechanism of battery overcharge is critical to safeguard the safe and durable operation of electric vehicles. With environmental changes and drivers’ random behaviors under real occasions considered, this paper demonstrates the multi-factor overcharge-to-thermal-runaway modelling theory based on electro-chemical thermal coupling analysis. A case study of a real-world electric vehicle that experienced an overcharge-caused thermal runaway accident is presented, and the pre-accident battery overcharge characteristics are dissected referring to the accident investigation reports. Furthermore, the multi-stage pre-accident characterization is performed by dividing overcharge into three feature stages, such as charge, fully-charged instant, and overcharge. Various characterization parameters directly measurable and indirectly calculated are extracted, then a variable evaluation of the state of health degradation under overcharge is implemented. Moreover, a rudimentary probability model of overcharge-caused thermal runaway is proposed combining all potential motivating factors, including environments and drivers’ behaviors. This is the first of this kind to apply the actual accident case on overcharge-caused thermal runaway research, which can guide the battery overcharge protection to safeguard drivers and passengers.