Impact of micro-short circuits on the electrochemical performance and structural degradation of lithium-ion batteries

This study investigates the impact of micro-short circuits on the electrochemical performance of lithium-ion batteries. By injecting different amounts of iron powder (0 g, 0.5 g, 2 g) into the batteries, micro-short circuit faults were simulated to evaluate their effects on battery performance. The experiments involved 1 C charge-discharge cycling tests and self-developed impedance measurement equipment, which monitored changes in the battery's capacity, Coulombic efficiency (CE), and internal resistance during the charge-discharge process. The results indicate that the micro-short circuit effect induced by the iron powder significantly affects the battery's performance. Compared to the control group, after iron powder injection, both the capacity retention and Coulombic efficiency of the batteries showed varying degrees of degradation. In particular, the 2 g iron powder group exhibited rapid performance degradation, with noticeable reductions in both capacity retention and Coulombic efficiency. In contrast, the 0.5 g iron powder group showed more gradual performance deterioration. To further analyze the changes in battery materials induced by micro-short circuits, the batteries were disassembled after cycling tests, and the cathode materials were characterized using scanning electron microscopy (SEM). The SEM results revealed significant burn marks and cracks in the cathode materials of the 2 g iron powder group, indicating that the electrochemical reactions triggered by the micro-short circuit caused considerable damage to the internal structure of the battery. Through these experiments, this study provides detailed theoretical support for the failure mechanism of micro-short circuits in lithium-ion batteries and offers valuable insights for battery fault diagnosis and safety management.