动力锂离子电池老化速率影响因素的实验研究

Experimental Study on Effect Factors of Aging Rate for Power Lithium-ion Batteries

针对动力锂离子电池的老化现象,以高比能量锂离子电池LG-21700为研究对象,以放电容量、欧姆内阻以及极化内阻作为表征参数,基于电池测试系统分别探究了充电倍率、放电倍率、充电截止电压、放电截止电压以及环境温度5种老化应力对电池老化速率的影响.研究结果表明:充放电倍率越大时,容量衰减速率越快,欧姆内阻和极化内阻的增长速率越快;充电倍率是影响老化速率的决定性因素,当充电倍率达到1.00 C时,电池的循环性能极差;充放电的截止电压区间越大,电池容量衰减速率以及欧姆内阻、极化内阻的增长速率越大;恒流恒压的充电方式有助于延缓老化;动力电池在低温环境中进行老化时,由于锂沉积的作用,其容量衰减速率以及内阻增长速率剧烈升高.综合考虑电池的容量特性、循环特性以及工作温度,在30~35℃进行充放电不仅可以延缓电池老化,还可以提高电池的工作性能,保证电池安全.综上,减小充放电倍率、充放电深度以及在合适的环境温度使用电池可以有效延长电池的使用寿命.

According to the aging problem of power lithium-ion batteries,the LG-21700 lithium-ion battery with high specific energy was taken as the research object for studying the effect factors on its aging rate.The discharge capacity,ohmic resistance and polarization resistance were tested to characterize the degree of ageing respectively.Effects of five aging stresses on the aging rate were investigated and discussed based on the battery test system,which were charge rate,discharge rate,charge cut-off voltage,discharge cut-off voltage and ambient temperature,respectively.The results show that the capacity degradation,ohmic resistance and polarization resistance increase faster as the charge or discharge rates enlarge.Meanwhile,the charge rate is the crucial factor on the aging rate.When it reaches 1.00 C,the cycle performance of the battery becomes extremely poor.Moreover,the capacity degradation and internal resistance rise as the range between charge and discharge cut-off voltage enlarges.The charging method of constant current-constant voltage is beneficial to extending the lifetime.When the battery is aging in low temperature,the capacity degradation and internal resistance increase sharply due to the effect of lithium deposition.Considering the capacity characteristics,cycle performance and working temperature,it is found that charging and discharging between 30-35℃ not only delays the aging,but also improves its working performance and ensures its safety.In summary,the lifetime of battery can be effectively extended by reducing the charge/discharge rate and depth of charge/discharge or selecting the suitable ambient temperature.