Failure and performance degradation mechanisms of pouch batteries under dynamic and quasi-static loading

To reveal the failure characteristics and performance degradation mechanisms of lithium-ion batteries under different mechanical abuse conditions, comparative tests of quasi-static planar compression, dynamic plate impact, and dynamic hemispherical impact were conducted on commercial pouch lithium-ion batteries. Real-time voltage monitoring, post-impact voltage tracking, electrochemical performance tests, and disassembly analysis were combined to investigate the effects of loading mode on failure threshold, electrical performance degradation, and internal damage mechanism. The results show that the loading mode significantly affects the safety boundary and failure mode of the battery. Failure occurs after a deformation energy of approximately 115 J under quasi-static compression, whereas plate impact and hemispherical impact induce failure at input energies of approximately 50 J and 10 J, respectively, indicating that dynamic impact, especially localized hemispherical impact, markedly narrows the safety boundary of the battery. At the same load level, quasi-static compression mainly causes an increase in internal resistance, while plate impact leads to more pronounced capacity loss. Under critical failure conditions, plate impact causes only slight capacity loss and internal resistance variation, whereas hemispherical impact results in a capacity loss of 17.4% and an internal resistance up to three times that of the fresh battery. This indicates that the transient voltage disturbance does not necessarily correspond to the actual degradation degree. Disassembly analysis further reveals two distinct failure mechanisms under dynamic impact: localized separator tearing and internal short circuit induced by hemispherical impact, and aluminum-plastic film rupture with electrolyte leakage induced by plate impact. This study provides experimental evidence for battery safety risk assessment under complex collision scenarios.