A comparative study of overcharge thermal runaway force-electrical-thermal characteristics and safety assessment of lithium batteries with different cathode materials

This work compares the differences in thermal runaway (TR) behavior and force-electrical-thermal characteristics of three predominant types of lithium-ion batteries (LiNixCoyMn1-x-yO2 (NCM), LiFePO4 (LFP), LiCoO2 (LCO)) with the highest market share under various overcharge rates. The voltage and temperature of cells during the experiment are monitored. Early warning based on expansion force is currently a hot research topic. This study analyzes the evolution of expansion force from overcharging to TR, and lays the foundation for expansion force early warning. The results show that LFP batteries exhibit the lowest overcharging tolerance. However, LFP batteries exhibit the lowest TR hazard and only exhibit smoke release, no explosion or fire. NCM and LCO batteries exhibit more serious TR hazards. A novel safety assessment method based on seven experimental characteristics is proposed to evaluate the TR risks and hazards of three types of batteries qualitatively and quantitatively. Overall, this study compares the TR behaviors of three common lithium-ion batteries, introduces the expansion force parameter for comparative analysis, and reveals the mechanisms of multidimensional parameter evolution offering valuable insights for battery selection. The findings guide the safe use and risk management of lithium-ion batteries in electric vehicles.