锂离子电池电解液痕量水污染的超声表象

Studies on ultrasonic appearance of trace water contamination in lithium-ion battery electrolyte

锂离子电池电解液痕量水污染是导致电池产气和快速失效的重要原因,而过去对痕量水污染电芯缺乏无损检测分析技术。本工作基于超声无损成像技术对微量产气副反应的敏感性,对不同水含量电解液商用NCM523/AG软包电池化成、静置、循环过程中的产气行为进行了超声透射扫描成像,并结合EIS/SEM和充放电特性对其老化和失效机制进行了分析。结果表明痕量水的存在会造成电解液的损耗,加速气体生成,增加界面阻抗和极化电压,造成库仑效率降低和可逆容量衰减,加快电池失效过程。本研究对电池生产过程质量控制以及使用过程的失效机理分析具有指导意义。

Trace water contamination in the electrolyte is an important cause for gassing and rapid failure of lithium-ion batteries.However,there is lack of nondestructive techniques to detect trace water in cells.In this study,based on the sensitivity of ultrasonic nondestructive imaging technique to trace gassing side reactions,ultrasonic transmission scanning imaging was performed to analyze the gassing behavior of commercial NCM523/AG pouch cells with different water contents during formation,storing,and cycling.Using electrochemical impedance spectroscopy,scanning electronic microscopy,and charge/discharge characterization,the aging and failure mechanisms were analyzed.The results show that the presence of trace water causes consumption of electrolyte,accelerates gas generation,and increases interfacial impedance and polarization voltage.These characteristics can further cause the reduction of coulomb efficiency and capacity decay,thus accelerating battery failure.This study has guiding significance for quality control in the battery production process and failure mechanism analysis during battery usage.