全氟烷基膦酸锂电解液的制备与性能研究

选取氯代二异丙基膦(C6H14PCl)为原料, 利用电化学氟化方法, 得到全氟烷基膦酸[(C3F7)2PF3], (C3F7)2PF3与氟化锂(LiF)反应得到全氟烷基膦酸锂(Li[(C3F7)2PF4]), 将其溶于碳酸乙烯酯(EC)和碳酸二甲酯(DMC)质量比为1∶1的混合溶剂中得到电解液, 考察电解液的电导率、抗水性及氧化分解电位. 以LiCoO2为正极, 锂片为负极组装两电极模拟电池体系, 测试得到电池的放电平台为3.7 V; 电池的首次放电比容量为107 mA•h•g－1; 当循环放电40次后, 容量衰减较快, 电池循环50周后, 效率仍保持102%. 交流阻抗图谱表明电解液放电时的阻抗约为140 Ω. 研究结果表明, 全氟烷基膦酸锂有望成为新型锂离子二次电池的电解质盐.

Preparation and Performance of Lithium Perfluoroalkylphosphonate

Lithium perfluoroalkylphosphonate was synthesized by LiF and perfluoroalkylphosphonate acid obtained by electrochemically fluorinating chlorodiisopropylphosphine. Some properties of a kind of electrolyte that was made from dissolving the lithium perfluoroalkylphosphonate in the mixed solvent with ethylene carbonate (EC) and dimethyl carbonate (DMC) mass ratio 1∶1 were investigated, such as conductivity, stability toward hydrolysis and oxidative decomposition potential, and so on. The electrolyte was studied by a secondary cell testing system. Using LiCoO2 as anode, Li as cathode, it was found that the discharge platform was 3.7 V, initial discharge capacity was 107 mA•h•g－1 and efficiency still remained 102% after cycled 50 times while capacity decreased largely after 40 times. The electrochemical impedance spectroscopy diagram showed that the electrolyte electrochemical impedance was nearly 140 Ω. The results indicated that the lithium perfluoroalkylphosphonate was expected to be the new electrolyte salt of lithium-ion rechargeable batteries.