Study on the fire risk associated with a failure of large‐scale commercial LiFePO 4 /graphite and LiNi x Co y Mn 1‐x‐y O 2 /graphite batteries

The fire hazards of fully charged large‐scale commercial LiFe PO 4 /graphite and LiNi x Co y Mn 1‐x‐ y O 2 /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 LiNi x Co y Mn 1‐x‐ y O 2 /graphite battery give more splash spark, explosion, and gas/smoke ejection, while LiFe PO 4 /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 LiFe PO 4 /graphite and LiNi x Co y Mn 1‐x‐ y O 2 /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 LiFe PO 4 /graphite battery is higher than LiNi x Co y Mn 1‐x‐ y O 2 /graphite battery. The normalized heat release by initial mass of battery is found to be 2.304 and 3.133 kJ/g for LiFe PO 4 /graphite and LiNi x Co y Mn 1‐x‐ y O 2 /graphite batteries, respectively. Besides, LiNi x Co y Mn 1‐x‐ y O 2 /graphite battery releases more CO and exhibits larger mass loss compared with LiFe PO 4 /graphite battery. Finally, fire risk assessment for two batteries is also performed and discussed. In conclusion, LiNi x Co y Mn 1‐x‐ y O 2 /graphite battery is more hazardous than LiFe PO 4 /graphite battery in current condition.