高温循环老化对锂离子电池安全性影响研究

Research on the Impact of High-temperature Cyclic Aging on the Safety of Lithium-ion Batteries

高温循环老化会造成电池降解,改变电池热稳定性,进而影响电池的安全使用。全面阐述锂离子电池在高温循环老化过程中热安全特性演变具有重要意义。通过对锂离子电池在高温循环老化过程中降解行为、放电过程中的产热特性、绝热热失控特性及过充热失控特性进行研究,全面揭示锂离子电池在高温循环老化过程中热安全特性的演变,为电池的安全使用提供参考。结果显示,电池在高温循环老化过程中的内部降解致使容量衰减、阻抗增加。在绝热放电过程中,随着老化程度的加深,温升先降后增,主导因素由容量变为温升速率;高温循环严重削减阳极和阴极的热稳定性,使得电池的自产热起始温度和热失控触发温度严重下降,热稳定性降低。活性物质的损失致使电池最高温度和最大温升速率降低,热危害性降低;由于高温循环老化致使电池阻抗增加,在过充过程中,老化电池的特征电压均出现升高。但是,老化电池的过充热失控时间缩短、热失控触发温度降低、副反应热对热失控触发的贡献率降低,电池的抗性下降。

High-temperature cyclic aging can cause battery degradation,influence battery thermal stability,and further affect the safety use of batteries.It is of great significance to clarify the evolution of thermal safety during high-temperature cyclic aging for lithium ion batteries.By investigating the degradation behavior,heat generation characteristics upon discharge,adiabatic thermal runaway characteristics,and overcharge characteristics during high-temperature cyclic aging,the thermal safety evolution is revealed,which can provide guidance for the safe utilization of lithium ion batteries.High-temperature cyclic aging causes battery degradation,such as capacity degradation and impedance increase.In the adiabatic discharge process,the entire temperature rise first decreases and then increases with aging.The dominant factor changes from capacity to temperature rise.High-temperature cyclic aging severely reduces the thermal stability of the anode and cathode,making the self-heating initial temperature and thermal runaway triggering temperature decrease severely.The battery thermal safety is reduced.The loss of active materials reduces the maximum temperature and the maximum temperature rise rate,which means that the thermal hazards decrease.Due to the impedance increase during high-temperature cyclic aging,the characteristic voltages increase upon overcharge.However,the overcharge thermal runaway time of aged cell is shortened,the thermal runaway triggering temperature is reduced,and the contribution rate of side reaction heat to thermal runaway triggering is reduced.The battery tolerance is reduced.