Lithium-ion batteries (LIBs) are widely employed in electric vehicles owing to their high power density, long cycle life, and environmental friendliness. However, LIBs are hazardous in the event of a crash, leading to thermal runaway. In this study, the basic structure of a battery module is analyzed to improve the crashworthiness of LIBs. A simplified finite element model of the battery module structure, which is a battery unit composed of two pouch cells and a cooling fin, is set up and verified by conducting module-level simulations. The simulation results reveal that the cooling fin in the battery module has the potential to absorb energy. Six sandwich configurations are introduced to modify the cooling fin. With a unidirectionally stiffened double hull USDH structure serving as an example, a parametric analysis is conducted, demonstrating that the sandwich height does not influence the areal density; a small height of 3 mm can make the material work sufficiently while avoiding early buckling of the structure. Further, the crashworthiness of different sandwich configurations with the same areal density and height is compared, leading to three deformation modes. USDH and circular core structures are found to be able to effectively reduce the peak force and improve the energy absorption ability.