Quantitative study on the thermal failure features of lithium iron phosphate batteries under varied heating powers

Highlights: • Pioneering study the effects of heating power on battery thermal failure at same heating quantity. • The thermal failure process of the battery was divided into four stages. • Quantifying the internal heat generation of battery thermal failure. • Batteries have the highest internal heat generation at 100 W. • The explosion risk of battery under high heating power cannot be underestimated. Insights into thermal failure features under varied heating powers are significant for the safe application of lithium ion batteries. In this work, a series of experiments were conducted to investigate the thermal failure features of fully charged lithium iron phosphate battery by means of copper slug battery calorimetry. Batteries were given a total quantity of external heat (16 kJ) under various heating powers (20–200 W). Battery temperatures, onset time of venting, mass loss and internal heat generation were measured and analyzed. Results show onset times of venting and thermal runaway both decrease exponentially with increasing heating power. Heat generation of batteries under different heating powers is in the range of 10.38 kJ − 15.07 kJ. The battery maximum temperature and heat generation do not increase monotonically with heating power, but reach the highest at 100 W. Furthermore, the experiments at 20 W with continuous heating were carried out to contrast with the experiments results of fixed heating quantity. It is found that battery maximum temperature, mass loss and heat generation are all higher under continuous heating. These encouraging results could enhance our understanding of thermal failure features and provide references for the safety design and thermal failure propagation prevention in battery module.