不同正极材料锂离子电池热失控产物研究

Research on thermal runaway products of lithiumion batteries with different cathode materials

针对目前单节锂离子电池热失控过程中产生的气体,其可燃性和爆炸性将会引起热蔓延的问题,选择3种不同正极材料的18650电池作为研究对象,在不同的荷电状态条件下,通过对比热失控特征温度、热失控气体的成分、析出时间,对不同正极材料锂离子电池热失控危险性进行研究。结果表明:在相同荷电状态(SOC)的条件下,三元正极材料的锂离子电池的热失控起点温度明显低于以钴酸锂为正极材料的电池,且热失控峰值温度远高于钴酸锂电池,表明三元锂离子电池的危险性明显高于钴酸锂电池。对比两种不同的三元锂离子电池,镍元素的比例很大程度影响了电池的安全性,随着镍元素比例的提高,电池热失控的危险性随之升高。不同正极材料的锂离子电池在热失控之后产生的气体种类大致相同,H2与CO_(2)的析出时间都随着SOC的增加逐渐提前,且在相同试验条件下,三元锂离子电池的H_(2)析出比钴酸锂电池更早,CO_(2)的峰值也随着SOC的增加逐渐升高,并且100%SOC组的锂离子电池热失控之后产生的CO_(2)远高于其他SOC试验组。

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 LiCoO_(2)as cathode material,and the thermal runaway peak temperature is much higher than that of LiCoO_(2)batteries,indicating that the risk of ternary lithium-ion batteries is significantly higher than that of LiCoO_(2)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 H_(2)and CO_(2)were both gradually advanced with the increase of SOC.And under the same experimental conditions,the H_(2)precipitation of ternary lithium-ion batteries is earlier than that of LiCoO_(2)batteries,and the peak value of CO_(2)gradually increases with the increase of SOC.The CO_(2)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.