Abstract: In order to effectively prevent and control safety accidents in lithium iron phosphate battery energy storage power stations, it is of utmost importance to evaluate the explosion risk of gases escaping from lithium iron phosphate batteries after thermal runaway. Based on the preliminary experimental results, this article prepares premixed gases with different volume ratios of combustible gases and air released from thermal runaway of lithium iron phosphate batteries at different states of charge (SOC), and conducts research on the detonation process of premixed gases. The experimental results show that the explosion pressure of premixed gas shows a pattern of first increasing and then decreasing with the increase of combustible gas volume fraction, and has little correlation with SOC; The maximum pressure pmax of premixed gas deflagration increases with the increase of the proportion of combustible components such as H2, CO, and CH4 in the premixed gas; By conducting a 20 L ball explosion limit test, the explosion limits of premixed gases prepared for batteries with different states of charge were obtained; Comparing two numerical calculation methods for explosion limits, it is believed that the Le Chatelier formula is suitable for calculating the lower explosion limit, while the adiabatic flame temperature method is suitable for calculating the upper explosion limit; According to the explosion index Kg, it can be seen that the destructive effect caused by thermal runaway gas explosion accidents in lithium iron phosphate batteries increases with the increase of SOC, indicating that high SOC lithium iron phosphate batteries are highly prone to fire and explosion hazards. It is recommended to take measures such as installing combustible gas concentration monitoring devices to prevent and reduce the potential risks of the battery.

Key words: combustible gas, explosive limit, pressure, lithium? ion phosphate batteries, energy storage