MnO2改性Li3V2（PO4）3/C正极材料的电化学性能

Electrochemical Performance of MnO2 Modified Li3V2（PO4）3/C Cathode Materials

通过改良的溶胶–凝胶法（pH=4）制备Li3V2（PO4）3/C正极材料,然后通过聚乙烯醇（PVA）辅助的悬浮液包覆法利用不同含量的无定形MnO2对其进行包覆改性,MnO2的包覆量分别为0%、2%、3%和4%（质量分数）。扫描电子显微镜显示添加适量MnO2,样品的晶粒尺寸变小且形成片层状形貌。电化学测试表明,包覆MnO2后的电极材料性能明显好于未包覆样品,且倍率越高,改善性能越明显,当引入3%的MnO2,正极材料具有最佳的电化学性能。该样品在0.5C倍率下室温首次放电比容量为144.4 mA·h/g,在0.15.0 C倍率下进行60个循环后的放电比容量为94.7 mA·h/g（容量保留率56.7%）,电荷转移电阻仅为18.9？。

Li3V2（PO4）3/C was prepared by an improved sol-gel method（pH=4） and then modified with various amounts of MnO2（0, 2, 3 and 4%, mass fraction） by a suspension coating process assisted with polyvinyl alcohol（PVA）. The results by scanning electron microscopy（SEM） indicate that the particle size of MnO2-coated samples reduces and a plate-like structure forms at an appropriated addition amount of MnO2. The electrochemical tests reveal that the performance of MnO2-coated samples is much better than that of pristine Li3V2（PO4）3/C material. The effect of MnO2 modification becomes more dominant when the current rate increases. When the content of MnO2 increases to 3%, the sample exhibits the optimum electrochemical performance among all the samples. It delivers an initial discharge capacity of 144.4 m A·h/g at 0.5 C at room temperature. It has a discharge capacity of 94.7 m A·h/g with a capacity retention of 56.7% after 60 cycles at 0.1–5.0 C. However, its charge transfer resistance is only 18.9 ？.