Evolution mechanism and non-destructive assessment of thermal safety for lithium-ion batteries during the whole lifecycle

The thermal safety variations of lithium-ion batteries during operational usage pose a significant threat to the safe application of electric vehicles. This work initially investigates the battery thermal safety evolution mechanism under different degradation paths. Lithium plating is identified as the critical common degradation mechanism leading to the decline of battery thermal safety through multi-angle characterization analysis. However, lithium plating generated by different formation mechanism has different impact on the battery thermal stability. The most severe degradation of battery thermal safety is caused by lithium plating which is induced by the limited lithium intercalation rate under low-temperature cycling and high-rate cycling. Further, the mechanism of internal degradation on the battery thermal safety is elucidated through multi-scale thermal test analysis. It is indicated that lithium plating and transition metal dissolution are crucial factors leading to the decreased thermal stability of the anode and cathode respectively, which consequently results in a significant reduction of T1 and T2. Furthermore, based on the principle of internal degradation synchronously affecting electrochemical characteristics and thermal stability characteristics, the mapping relationship between the observation indicators of electrochemical characteristics and the characterization parameters of thermal safety is established, realizing the non-destructive assessment of battery thermal safety during the whole lifecycle.