FEC 基电解液对高压正极材料 Li2CoPO4F 电化学性能的影响

本文研究了以氟代碳酸乙烯酯FEC（fluoroethylene carbonate）为共溶剂的电解液对高压正极材料 Li₂CoPO₄F 电化学性能的影响，与碳酸酯基电解液1 mol·L^-1 LiPF₆ EC/DMC=1:1（m:m）相比，1 mol·L^-1 LiPF₆ FEC/DMC=1:1（m:m）可显著提高Li₂CoPO₄F的循环稳定性. 通过线性扫描伏安法（LSV）、扫描电镜（SEM）、X射线光电子能谱（XPS）、X射线衍射（XRD）结合电化学阻抗（EIS）对 FEC 改善 Li₂CoPO₄F 材料循环稳定性的机理进行了探索，结果表明与传统碳酸酯基电解液相比，FEC 基电解液在高压下有着优异的抗氧化性，能够有效抑制电解液的氧化分解. 同时，FEC 基电解液中形成的表面膜具有更高的稳定性，能够抑制电极/电解液界面副反应的发生，提高循环过程中电极材料结构稳定性，从而有益于提高 Li₂CoPO₄F 材料的电化学性能.

Influences of FEC-based Electrolyte on Electrochemical Performance of High Voltage Cathode MaterialLi2CoPO4F

The effects of fluoroethylene carbonate (FEC) as co-solvent on the electrochemical performance of high voltage cathode materialLi₂CoPO₄F are investigated. Compared with traditional carbonate based electrolyte (1mol·L^-1 LiPF₆ EC/DMC (1:1, m:m)), the FEC/DMC based electrolyte can significantly improved the electrochemical performance ofLi₂CoPO₄F. After 100 cycles between 3Vand 5.4 V at 1 C rate, the capacity retention ofLi₂CoPO₄F electrode in 1mol·L^-1 LiPF₆ EC/DMC (1:1, m:m)was 52.6 % , while that in the EC/DMC based electrolytewas only 14.5 %.Possible functional mechanisms of FEC improving the electrochemical performance ofLi₂CoPO₄F were studied by LSV, EIS, SEM and XPS measurements. It was shown that compared with the traditional EC/DMC based electrolyte, the FEC/DMC based electrolyteexhibited higher stability at high voltage, which suppressed the side reactions at electrode/electrolyte interface when charged to high voltage, and improved the structure stability ofLi₂CoPO₄F during cycling, thus, significantlyenhanced the electrochemical performance ofLi₂CoPO₄F.