Generalized separator failure criteria for internal short circuit of lithium-ion battery

To enable the understanding of the internal short circuit mechanism triggered by separator failure, mechanical indentation loadings are designed to create the deformation of the separator in a precisely controllable way. Herein, two characteristic short-circuit types are observed in anode-separator-cathode stack upon mechanical abusive loading, i.e., rapid and gentle voltage drop. Through the ex-situ experiment, the rapid voltage drop is due to the direct contact between cathode and anode as a result of separator fracture, while the gentle voltage drop is related to the flattening of the separator with the absence of its function to isolate electron transfer. The developed detailed numerical models, considering the failure of anode and cathode and the anisotropy of separator, can well describe the mechanical responses of components and stack. Thanks to the numerical computation model and computation, we establish and validate the generalized short-circuit criteria for the two representative failure modes based on the volumetric strain and equivalent strain of separator. Results provide a powerful and generalized tool aiming for the design of next-generation separator technology, enabling a more fundamental and effective way for future ISC detection, monitoring, and evaluation which can be embedded within the battery management system.