Research on the lower explosion limit of thermal runaway gas in lithium batteries under high-temperature and slight overcharge conditions

Lithium battery thermal runaway release a large amount of flammable gas, which often triggers secondary explosions at high temperatures. Slight overcharge can lead to an increase in the risk of thermal runaway gas, and different charge and discharge temperature environments have a great impact on the thermal runaway gas of overcharged batteries. In this paper, the lower explosion limits of thermal runaway gas of lithium batteries under different charging and discharging environments are studied, and corresponding guidelines are proposed for the safe use of lithium batteries. The experimental results show that overcharging leads to a decrease in the Lower Explosion Limit (LEL) of thermal runaway gas. The charge/discharge temperature environment also has an effect on the thermal runaway gas LEL of the battery, and the lowest thermal runaway gas explosion lower limit is found for the battery charged and discharged at a temperature environment of 40 °C. The decrease of thermal runaway gas LEL is due to the decrease of CO2 content in the gas and the increase of vaporized Differential Scanning Calorimetry (DMC) content, and the increase of vaporized DMC content in the gas mixture is due to the precipitation of lithium in the negative electrode material.