The indentation analysis triggering internal short circuit of lithium-ion pouch battery based on shape function theory

A novel indentation theory with homogenized, isotropic, and continuum model based on different shape functions is investigated to predict the mechanical behavior triggering internal short circuit of lithium-ion pouch battery (LIPB) under indentation loading. By taking energy conservation principle into account, the relationship among indentation force, indentation displacement, and indentation region of LIPB is proposed. The results conclude that the effects of deformation region and indentation displacement play an important role in mechanical behavior triggering internal short circuit. The theoretical results based on sine, cosine, and quadratic shape functions agree well with experimental results. Both of increasing compressed yield stress of jellyroll core and punch radius and decreasing flow stress of soft casing and thickness of soft casing can avoid triggering internal short circuit of LIPB. According to current research, the indentation loading is reduced to flat compression when punch radius approaches infinity, and the internal short circuit of LIPB under flat compression is very difficult to be triggered. Effectiveness and application scope of different shape functions are also discussed. The theoretical model provides guidance for improving mechanical behavior, decreasing internal short circuit, and optimizing structure of LIPB in industrial manufacture.