Failure behavior of prismatic Li-ion battery cells under abuse loading condition - A combined experimental and computational study

Li-ion jelly rolls and prismatic battery cells were quasi-statically loaded by three different indenters: (1) Hemispherical nose punch, (2) Flat end punch, and (3) Round edge wedge. Force and displacement during indentation were measured. For the cells, voltage drop was also recorded to monitor short circuiting. The deformation/failure modes of specimens were examined and the critical force at initiation of short circuit was analyzed for the cells. Substantial differences occurred depending upon indenter shape; also loading orientation for the wedge. In all cases, short circuiting of the entire cell initiated by formation of the first jelly roll crack. Based on test loading and boundary conditions, finite element (FE) models were developed using explicit FEA code LS-DYNA. The model predictions demonstrated good agreement in terms of force-displacement responses and structural failure modes at both jelly roll and prismatic cell levels. With the validated numerical model, the original battery cell design was modified in order to alter the deformation and failure modes of the jelly roll. Three design modifications were considered: (1) Include a thin mica sheet between the first and second jelly roll layers; (2) Use thinner, but higher stiffness/strength steel to replace the aluminum alloy enclosure material; and (3) Change the enclosure material where indenter contact occurs from an aluminum alloy sheet to an aluminum alloy sandwich structure. All three indentation conditions were simulated and results were compared to the original design. The outcomes were sensitive to indenter shape, where round end wedge indentation benefitted the most. The findings have potential for improving prismatic battery cell safety by incorporating them into future designs.