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化学学报
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化学学报 ›› 2011, Vol. 69 ›› Issue (11): 1287-1292. 上一篇    下一篇

研究论文

二(三氟甲基磺酰)亚胺锂对磷酸铁锂正极高温行为的影响

车海英，杨军*，吴凯，王久林，努丽燕娜   

  1. (上海交通大学化学化工学院 上海 200240)
  • 投稿日期:2010-10-10 修回日期:2011-01-06 发布日期:2011-02-12
  • 通讯作者: 杨军 E-mail:yangj723@sjtu.edu.cn
  • 基金资助:

    973计划项目

Effect of Lithium Bis(trifluoromethylsulfonyl)imide on the High- temperature Behavior of LiFePO4 Positive Electrode

CHE Hai-Ying, YANG Jun, WU Kai, WANG Jiu-Lin, NU Li-Yan-Na   

  1. (School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240)
  • Received:2010-10-10 Revised:2011-01-06 Published:2011-02-12
  • Contact: Jun YANG E-mail:yangj723@sjtu.edu.cn

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系统研究了电解质锂盐对磷酸铁锂电极高温性能的影响, 并探讨了相关的作用机理. 差示扫描量热仪测试显示, 与LiPF6相比, 二(三氟甲基磺酰)亚胺锂(LiTFSI)和LiBF4具有对水份稳定且热稳定性好的优点, 更适合高温条件下使用. 应用等离子体发射光谱考察LiFePO4在55 ℃和不同电解液体系中铁离子溶出程度, 结果表明, 在LiTFSI和无氟锂盐电解液中LiFePO4的铁很少溶出, 而在LiPF6电解液中却溶出严重, 且FePO4的铁溶出量高于LiFePO4. 循环伏安和光学显微镜测试结果显示少量LiBF4的加入能有效抑制LiTFSI对集流体铝箔的腐蚀. 以LiTFSI和LiBF4作为混合锂盐配成的电解液能显著改善LiFePO4/Li电池的高温电化学性能, 在55 ℃和1 C倍率下循环40次后放电比容量达147.7 mAh/g.

关键词: 电解液, 二(三氟甲基磺酰)亚胺锂, 磷酸铁锂, 铁溶出, 高温性能

The effect of lithium salts in electrolytes on the high-temperature performance of LiFePO4 electrode is investigated systematically and the related mechanism is revealed. Differential scanning calorimetry measurements show that lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and LiBF4 are more favorable for the use at high temperature than LiPF6 because of their water insensitivities and excellent thermal stabilities. Inductively coupled plasma is used to examine the dissolving degree of ferrous ions from LiFePO4 in the different electrolytes at 55 ℃. It is found that little ferrous ions can be dissolved from LiFePO4 in LiTFSI and fluorine-free lithium salt electrolytes. On the contrary, it is quite serious in LiPF6 electrolyte. In addition, FePO4 is easier to release iron ions than LiFePO4 in the LiPF6 electrolyte. The experimental results of cyclic voltammetry and light microscope indicate that a small amount of LiBF4 can inhibit the corrosion of aluminum foil current collector from LiTFSI. The electrolyte containing mixed salts of LiTFSI and LiBF4 significantly improves the high-temperature performance of LiFePO4/Li cell. The discharge capacity is still 147.7 mAh/g after 40 cycles at 55 ℃ and 1 C rate.

Key words: electrolyte, lithium bis(trifluoromethylsulfonyl)imide, LiFePO4, iron dissolution, high- temperature performance