Assessment of the explosion risk during lithium-ion battery fires

Lithium-ion batteries are widely used for renewable energy storage and to deliver mobile power because of their high energy densities and electromotive forces. However, such batteries can catch fire and explode, potentially causing casualties and property damage. Here, we used a cone calorimeter to investigate the fire risk and assess the associated heat release rate (HRR). Standard cylindrical battery fires feature two combustion stages, the first of which is characterized by diffusion-like flames and the second by partially premixed flames with a higher peak HRR and a violent explosion. The overall combustion properties depend principally on the state of charge (SOC). A higher SOC battery is associated with a higher maximum HRR, a shorter HRR peak-to-peak time, larger CO and CO2 emissions, and a greater instantaneous mass loss. The average rate of heat emission based on the measured combustion properties is introduced and its maximum value is expected to predict reactivity and explosiveness comprehensively in the event of fire.