Mechanical-electrical decoupling failure of pouch lithium-ion batteries under mechanical abuse: Role of indenter type

Mechanical failure is a primary trigger of thermal runaway in lithium-ion batteries and is commonly assumed to be accompanied by a synchronous voltage drop caused by internal short circuits following fracture. Here, we challenge this prevailing assumption, which may lead to overestimation of battery mechanical performance. Using two mechanical test protocols, three representative loading conditions, and three complementary analytical approaches, we systematically investigate battery mechanical failure behaviors and their underlying mechanisms. The results show that when tensile deformation and global bending dominate, mechanical-electrical synchronous failure occurs, with force and voltage drops appearing nearly simultaneously. In contrast, when localized shear stresses govern the response, premature separator rupture and electrode contact can occur prior to global structural instability, leading to pronounced mechanical-electrical decoupling and the formation of minor internal short-circuit pathways. These findings provide critical insights for avoiding overestimation of battery mechanical robustness and offer guidance for safer mechanical design and more accurate multiphysics failure modeling.