Study on the fire risk associated with a failure of large-scale commercial LiFePO4/graphite and LiNixCoyMn1-x-yO2/graphite batteries

Abstract

The fire hazards of fully charged large-scale commercial LiFePO4/graphite and LiNixCoyMn1-x-yO2/graphite batteries are experimentally studied using a bench-scale calorimetry apparatus. The battery burning process can be roughly summarized into three stages with significant criteria. The fire behaviors associated with LiNixCoyMn1-x-yO2/graphite battery give more splash spark, explosion, and gas/smoke ejection, while LiFePO4/graphite battery presents more jet flame. The sound signal may be a good choice for reflecting the battery state during thermal failure. The battery catches fire when average surface temperature (ST) reaches about 150°C. The maximum average STs for LiFePO4/graphite and LiNixCoyMn1-x-yO2/graphite batteries are approximately 535.3 and 658.7°C, respectively. The maximum heat release rate (HRR) of two batteries is comparable, while the total heat release for LiFePO4/graphite battery is higher than LiNixCoyMn1-x-yO2/graphite battery. The normalized heat release by initial mass of battery is found to be 2.304 and 3.133 kJ/g for LiFePO4/graphite and LiNixCoyMn1-x-yO2/graphite batteries, respectively. Besides, LiNixCoyMn1-x-yO2/graphite battery releases more CO and exhibits larger mass loss compared with LiFePO4/graphite battery. Finally, fire risk assessment for two batteries is also performed and discussed. In conclusion, LiNixCoyMn1-x-yO2/graphite battery is more hazardous than LiFePO4/graphite battery in current condition.