Effective Mechanical Properties of an Innovative Module-Free Li-Ion Battery Pack Integrated with Honeycomb Cells and Optimum Design for Enhanced Crash Energy Absorption

To create advanced lithium-ion battery packs (BP) that are both lightweight and durable in crashes, an innovative honeycomb BP design has been developed. This design involves inserting cylindrical lithium-ion battery cells into a honeycomb cell core, eliminating the need for traditional modules. To reduce the weight of BP, collision analyses using the finite element method (FEM) are conducted with various thickness-to-length ratios for the honeycomb cell structures. A new mathematical formula is developed to calculate the energy absorption rate per unit volume and compared with the FEM results. Based on the formula, the optimal thickness-to-length ratio is determined. Furthermore, a new method to capture effective mechanical properties for the integrated battery cells with honeycomb cells is developed using the optimal thickness ratios and a modified rule of mixture. To enhance the collision safety of the honeycomb BP, its dimensions have been optimized by performing transient FE analyses while colliding with a rigid pillar on its one edge. A weight reduction of approximately 23.7% has been achieved.