A study on the influence of compression pads on the safety and life of a lithium-ion cell module

The demand for eco-friendly electric powertrains has increased significantly in recent years. Cells are the most crucial component of a battery pack, directly influencing the dimensions, range, lifespan, performance, and cost of electric vehicles. Lithium-ion cells outperform other cell chemistries due to their higher energy density, allowing for more compact and lightweight designs while providing longer operational ranges. It is crucial that lithium-ion cell packaging complies with assembly requirements to maximize its lifespan and ensure operational safety. Assembly force requirements of lithium-ion cells are critical to ensure optimal cell performance throughout its lifetime & enhance the longevity of the battery pack. The compression pad between cells ensures appropriate cell assembly pressure. The service life is how long a lithium-ion cell can operate effectively, while the cyclic life refers to the number of charge-discharge cycles before cell functional degradation. The cell surface pressure varies from the cell's beginning of life till its end of life. This manuscript details the meticulous process for selecting a compression pad based on cell force requirements at the beginning and end of its life. It also considers cell swelling, thermal insulation and other factors crucial for compression pad selection. The chosen compression pad must ensure even pressure distribution across all cells in the module to prevent varying rates of cell ageing. The document also explains how different cell ageing rates within the module affect the overall battery pack cycle life. Additionally, a module-level 3D model swelling simulation was conducted to estimate cell pressure distribution with the selected compression pad. Based on the simulation results, a recommendation for maintaining even pressure distribution is provided and verified through another iteration of the swelling simulation. This proposed solution aims to maintain uniform cell ageing within the module and improve the cycle life of the cell, module, and battery pack.