In situ detection method for Li-ion battery of separator pore closure defects based on abnormal voltage in rest condition

Lithium-ion batteries have been widely used in various fields, and safety accidents caused by defects in batteries often occur. However, there is little research on defect characteristics, models, and detection methods. In this study, a typical separator pore closure defect is simulated using an intentionally implanted polyethylene terephthalate tab on the anode. The effects of the lithium-ion blocking defect on the battery performance are investigated through experimentation and simulation. The research reveals the lithium-ion horizontal equalization mechanism that causes abnormal voltage variation in the defective battery, especially in the long-term rest condition. Furthermore, an in-situ detection method to diagnose defects based on abnormal voltage variations is proposed herein. The detection is conducted under a special cycle, and the voltage variation is described by two characteristic parameters. The method is proven to identify the defects and determine the relative size through numerical simulation and experiments of pouch batteries with different aging and defect degrees. In addition to the implanted defects, this method can diagnose inherent heterogeneity problems. • An in-situ defect detection method based on abnormal voltage rise. • Horizontal equalization effect caused by separator pore closure defect. • Analysis and evaluation of inherent heterogeneity. • Modeling and simulation of defective battery.