Abstract: Targeting the current gas generated by the thermal runaway of single-cell lithium-ion battery, its flammability and explosive nature will cause the problem of thermal spread, three 18650 batteries with different cathode materials were selected as the research objects, and the risk of thermal runaway of lithium-ion batteries with different cathode materials was studied by the specific thermal runaway characteristic temperature, the composition of thermal runaway gas and the precipitation time under different charge state conditions. The results show that under the same SOC (state of charge), the thermal runaway starting temperature of lithium-ion batteries with ternary cathode material is significantly lower than that of batteries with LiCoO2 as cathode material, and the thermal runaway peak temperature is much higher than that of LiCoO2 batteries, indicating that the risk of ternary lithium-ion batteries is significantly higher than that of LiCoO2 batteries. Comparing the two different ternary lithium-ion batteries, the proportion of nickel greatly affects the safety of the battery, and as the proportion of nickel increases, the risk of thermal runaway increases. The types of gases produced by lithium-ion batteries with different cathode materials after thermal runaway were approximately the same, and the precipitation time of H2 and CO2 were both gradually advanced with the increase of SOC. And under the same experimental conditions, the H2 precipitation of ternary lithium-ion batteries is earlier than that of LiCoO2 batteries, and the peak value of CO2 gradually increases with the increase of SOC. The CO2 generated after thermal runaway in the 100% SOC group was much higher than that in other SOC experimental groups. The results of the study can provide theoretical support for the early warning of thermal runaway in lithium-ion batteries.

Key words: lithium-ion battery, cathode material, battery thermal runaway, thermal runaway gas