Validation of Sahraei Failure Criterion on cylindrical and pouch Lithium-ion battery cells
Yihan Song, Marian Bulla, Huzefa Patanwala, Elham Sahraei
Abstract
Safety is a major concern for Li-ion batteries in Electric Vehicles (EVs). Internal fracture of a battery cell may lead to a short circuit, and in extreme cases, cause thermal runaway and explosion. Consequently, heavy protective structures are used around EV battery packs to ensure zero deformation in the event of a vehicle crash. Having a universal failure model for battery short circuits can enable better prediction of imminent safety concerns and provide a tool for designing optimized protective structures. In this work, a failure and short circuit model titled the “Sahraei Failure Criterion” derived from simulations of the microstructure of the electrode-separator assembly, is developed and employed to predict cell failures for two types of cylindrical cells and one pouch cell. The failure model, in combination with a homogenized cell model, is validated in predicting all major loading scenarios, including local hemispherical and rod indentations, three-point bending and in-plane loading. This failure model defines the jellyroll's in-plane failure strain values as a function of the ratio of through-thickness compressive strain to in-plane tensile strain . A user-defined FORTRAN code has been used to implement the Sahraei failure criterion in RADIOSS. This universal failure model predicts the onset of internal fracture of the jellyroll under all available types of loadings with a single calibrated input curve. The model is also now programmed in the commercial software Altair RADIOSS (and OpenRadioss) as /FAIL/SAHRAEI criteria and is currently being implemented in Ansys LS-DYNA under the *MAT_MODIFIED_HONEYCOMB keyword to be available for users of both software.