锂离子电池电解液中甲醇杂质对石墨电极性能影响机制的电化学阻抗谱研究

运用电化学阻抗谱和循环伏安法研究了在1mol/LLiPF6-EC/DEC/DMC电解液中,不同甲醇杂质含量对石墨电极性能的影响及其机制.结果表明,甲醇对石墨电极性能的影响与电解液中甲醇的含量有关;其对石墨电极性能的影响机制为甲醇在2.0V左右还原生成的甲氧基锂沉积在石墨电极表面上,形成一层初始SEI膜,影响了EC的还原分解成膜过程.

Effects of Methanol Contaminant in Electrolyte on Performance of Graphite Electrodes for Li-ion Batteries Studied via Electrochemical Impedance Spectroscopy

Electrochemical performance of graphite electrode cycled vs.Li in 1 mol/L LiPF6-EC/DEC/DMC(1:1:1, volume ratio) electrolyte solution,which contains different concentrations of methanol,was investigated by cyclic voltammetry and electrochemical impedance spectroscopy(EIS) in the process of first lithiation.It was demonstrated that methanol contaminant caused the deterioration of the electrochemical performance of graphite electrodes,which depends markedly on the concentration of methanol.Based on the experimental results and analysis,a mechanism of the deterioration of the electrochemical performance of graphite electrode caused by methanol contaminant was proposed.The methanol was reduced to lithium methoxide,that deposited on graphite electrode surface to form initial SEI(solid electrolyte interphase) near 2.0 V,which resulted in ethylene carbonate excess decomposition and poor passive ability of the SEI ultimately formed.