低温条件下锂电池放电特性分析

Analysis of Discharge Characteristics of Lithium Batteries at Low Temperatures

了解锂电池的低温性能与低温容量损失路径对促进锂电池的低温应用及进一步开发更优秀的低温锂电池具有重要的现实意义。基于此,使用正极材料为较好低温性能钴酸锂和高比容量的三元锂复配合成,负极材料为钛酸锂的锂离子电池分别设计不同温度下不同倍率的放电实验、混合脉冲功率特性实验及0.05C小倍率充、放电实验,研究其在低温下的放电特性。实验结果表明:在低温下,锂电池的容量损失是可逆的,待放电温度回至常温时,锂电池的性能会恢复原样;温度和放电倍率对于锂电池的放电容量具有显著的影响;在低温环境下,随着温度的降低,欧姆内阻与极化内阻均增大,但极化内阻增加速率更快;锂电池的容量损失主要是由于锂电池活性材料损失、锂离子损失和内阻增加造成的,三者在不同温度区间内的作用力不尽相同,但整体而言,锂电池活性材料损失对于低温条件下锂电池的容量影响更大。

To promote the low-temperature applications of lithium batteries and further develop better low-temperature lithium batteries,the understanding of the performance and capacity loss path of lithium batteries at low temperatures is of practical significance.In this paper,the experimental object was a lithium battery in which the cathode material consisted of lithium cobaltate(with a better low-temperature performance)and ternary lithium(with a higher specific capacity)and the anode material was lithium titanate.To study the discharge characteristics of lithium batteries at low temperatures,the following experiments were designed,i.e.,discharge experiments at different discharge rates,hybrid pulse power characteristics experiments,and charge-discharge experiments at 0.05C discharge rate.Experimental results showed that at low temperatures,the capacity loss of lithium batteries was reversible,and when the discharging temperature returned to a normal temperature,the performance of lithium batteries would restore to its original state.Temperature and discharge rate had a significant effect on the discharge capacity of lithium batteries.At low temperatures,both the ohmic resistance and polarization internal resistance would increase with the decrease of temperature,but the polarization internal resistance increased even faster.The capacity loss of lithium batteries was mainly due to the loss of active materials,loss of lithium inventory and increase of internal resistance,and although the effects of these three factors were different in various temperature ranges,the loss of active materials had a greater influence as a whole.