Theoretical analysis of lithium‐ion battery failure characteristics under different states of charge

Summary Lithium‐ion batteries (LIBs) are extensively applied in various portable electronic equipment because of their high energy density power. However, accidents related to LIBs frequently occur. This study focuses on failure results, characteristics, and phenomena. Lithium‐ion batteries under different states of charge (SOCs) (0%, 30%, 50%, 80%, 100%, and 120%) at high temperatures have been investigated with the thermal abuse test. During the experiments, several typical failure processes were captured. According to the phenomena, 2 failure modes (smoke and jet fire) and 3 stages (primary reaction, tempestuous reaction in the middle time period, and extinguishing reaction in the final stage) were observed. A substantial amount of gas was vented, and jet fire was detected in the middle period. Only gas vented when the SOC was lower than 50%, whereas vented gas and jet fire were detected simultaneously when the SOC exceeded 50%. The results indicated combustible behaviors and exothermic reactions related to the SOC. An increase in the SOC caused a decrease in the thermal runaway initial temperature and the maximum increase in temperature. A higher SOC determined intense chemical reactions in the cell at higher temperatures, which caused a significant amount of materials to spew out of the batteries as well as additional mass loss. Relationships between failure characteristics and internal reactions were analyzed. The SOC should be lower than 50% in transportation or storage. The intercalated lithium capacities were the main reason for the series of domino reactions, which caused runaway in the terminal. These studies can serve as a reference for safety applications, transportation, and loss prevention in LIBs.