Modeling the anisotropic behavior of highly orthotropic lithium-ion batteries polymer separators

Abstract

Separators in commercial lithium-ion batteries are microporous polymeric films characterized by highly anisotropic mechanical behavior. An accurate characterization of their mechanical and fracture behavior is essential for optimal design, performance, and safety of lithium-ion batteries. In this work, the mechanical and fracture behavior of battery separators subjected to uniaxial tension and punch tests are characterized and discussed. An anisotropic continuum damage coupled elastic-hyperelastic-viscoplastic model is developed in the framework of the large deformation theory to capture the mechanical and fracture behavior of battery separators. A robust implicit integration scheme is developed then the model is implemented as a user-defined material subroutine (UMAT) in commercial finite-element software in order to solve boundary-value problems. The capability of the proposed model to predict the anisotropic mechanical behavior up to fracture for two different types of battery separators highlights the versatility of the proposed modeling approach. The model results showed a good agreement with the experimental data. Moreover, the model was able to predict the failure of the separators under different loading conditions.