Mechanism of inhomogeneous deformation and equal-stiffness design of large-format prismatic lithium-ion batteries

Inhomogeneous deformation is one of the most critical reasons for performance degradation in lithium-ion battery cells integrated into a complete battery system. However, the mechanism of inhomogeneous deformation at the cell-level remains poorly understood owing to the limited experimental and simulation studies on the subject. In this study, an in-situ measurement platform and a three-dimensional intercalation-induced expansion model are proposed for the heterogeneity analysis of a 100-Ah prismatic battery. The platform can precisely acquire the surface topography and multi-points strain distribution in three directions. Furthermore, the expansion model can accurately predict the electrochemical and mechanical responses of the battery by introducing an equivalent coefficient of intercalation-induced expansion. We obtained three typical characteristics of non-uniform deformation, which can be attributed to a warped shell with variable stiffness. Accordingly, a lattice composite sandwich spacer based on equal-stiffness theory is presented, with the maximum deformation and displacement variance reduced by 40.3% and 63.7%, respectively. Our proposed approach is beneficial for mitigating the inhomogeneous deformation and also conducive to a more uniform temperature field, as it allows refrigerant flow through the voids of spacers.