Research on internal short circuit detection method for lithium-ion batteries based on battery expansion characteristics

Short circuits are a major contributor to thermal runaway in lithium-ion batteries, but present detection techniques cannot distinguish different forms of short circuits. Therefore, the paper provides a detection method for internal short circuits (ISCs) based on coupled mechanical stress that can determine the type of short circuit. Firstly, cathode-anode (Ca-An) short-circuit batteries with a controllable triggering time and measurable internal temperature and electrode potential are designed. Secondly, the performance evolution of fault batteries under coupled mechanical stress conditions is investigated, along with the impact of faults on the battery's safety performance. Additionally, the influence of battery expansion characteristics on the contact pressure at the short circuit location and the correlation between short circuit resistance and mechanical stress are analyzed. The results show, except for self-discharge, no significant differences between Ca-An short-circuit and normal batteries, and there are no mutable features observed, but the faults can exacerbate internal-external temperature differences during charging. The different reasons for thermal runaway during sustained pressurization between short-circuit and normal batteries are revealed. Finally, a method for detecting ISC based on the differences in short-circuit resistance at different states of charge is proposed. Overall, the paper provides a basis for fault classification in lithium-ion batteries.