Numerical modeling of thermal distribution in polymer reinforced solid state electrolyte in lithium ion batteries

Abstract

The capability of lithium-ion batteries to dissipate internal heat generation is critical to performance and safe operation. Limiting the interface temperatures between the solid-state electrolyte and the polymer separator film is necessary to prevent the physical breakdown of the separator which could lead to thermal runaway of the battery. Current polymer separators and solid electrolytes have lower thermal conductivity values which are not conducive to efficient and uniform heat dissipation. This thesis describes the use of finite-element methods for numerical modeling of a thin film battery pack. This research compares presently used polyethylene(oxide) electrolyte and polyvinylidene fluoride polymer separators with thermally enhanced polymers, such as ordered crystalline polyethylene(oxide) and aluminum nitride polyvinylidene fluoride. Secondarily, an insulating metallic mesh and PVDF separator is analyzed. The interface temperatures within the simulated battery packs are compared and examined for optimum design characteristics. The results showed that the thermally enhanced ordered crystalline electrolyte reduced the interface temperatures by up to 45% compared to the amorphous electrolyte. Using the amorphous electrolyte, the optimum separator thickness which lowered interface temperatures with the integrated mesh was found to be between 25-35µm.