荷电状态对锂离子电池电化学性能的影响研究

Effect of state of charge on electrochemical performance of lithium ion battery

以LiNi0.6Co0.2Mn0.2O为主要正极材料制备锂离子电池,通过循环伏安法、电化学阻抗谱和恒电流间歇滴定技术研究了过充状态、过放状态和正常使用条件下锂离子电池电化学参数变化规律。结果表明,锂离子电池在过充、过放时,固体电解质界面(SEI)膜遭到破坏,电荷转移和离子扩散难度增加,电池整体电阻增大,安全性降低;然而,以恒电流间歇滴定方式将电池过充到4.5 V时,电池正、负极材料结构的改变具有可逆性,电池可以恢复到正常状态;将电池过放至2.5 V后,正极或负极材料的结构遭到严重破坏,该破坏过程不可逆。该项研究结果对于明确荷电状态对电池整体性能的影响、开发新型电池检测技术并进行电池安全设计具有重要意义。

Lithium ion batteries were prepared with LiNi0.6Co0.2Mn0.2O as the main cathode material.The electrochemical parameters evolution characteristics of lithium ion batteries were studied by using electrochemical impedance spectroscopy,cyclic voltammetry and constant current intermittent titration techniques under the conditions of over charge,over discharge and normal state,respectively.The results indicate that both the charge transfer and ion diffusion process become difficult when the lithium ion battery is over charged or over discharged,thus the overall resistance of the battery increases and the security reduces.However,the structure change of the anode and cathode materials is reversible after over charging to 4.5 V via constant current intermittent titration mode,and the battery can restore to normal state.After over discharging to 2.5 V,the structures of the anode and cathode materials are seriously damaged and the damage process is irreversible.The research results provide important reference for determining the influence of state of charge on the overall performance of the battery,the development of new battery detection technology and the safety design of lithium ion battery.