Temperature dependent dielectric performance of battery wrapping film for high voltage energy storage

Abstract The direct connection of Li-ion battery energy storage systems to high voltage (HV) power grids through electronic equipment becomes promising. The overvoltage and high-frequency interference of the electronic circuit may result in thermal runaway of battery cells and insulation failure of battery wrapping film. The key dielectric properties of the wrapping film for energy storage battery are investigated under DC at high frequency and room temperature to elevated temperature. The results indicate that high-frequency electric fields and high temperatures are both adverse to the insulation performance of the wrapping film. Under concurrent high-temperature and high-electric-field conditions, the breakdown strength can decrease by more than 70% compared to that under regular conditions. The analysis of the broadband dielectric response suggests that the interfacial defects inside the wrapping film may play an important role in the degradation of dielectric performance. This research provides theoretical basis for insulation failure and improvement of battery wrapping films used in HV energy storage systems.