Synthesis and characterization of LiVPO4F/C using precursor obtained through a soft chemical route with mechanical activation assist
Synthesis and characterization of LiVPO4F/C using precursor obtained through a soft chemical route with mechanical activation assist
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DOI：
10.1016/j.electacta.2012.12.095
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发表时间：
2013-02
影响因子：
6.6
通讯作者：
Jiexi Wang;Xinhai Li;Zhixing Wang;Huajun Guo;Yunhe Zhang;Xunhui Xiong;Zhenjiang He
中科院分区：
文献类型：
--
作者：
Jiexi Wang;Xinhai Li;Zhixing Wang;Huajun Guo;Yunhe Zhang;Xunhui Xiong;Zhenjiang He
采用机械活化辅助的软化学方法制备了碳包覆的三斜晶系LiVPO 4F样品。在球磨过程中，V（+5）被草酸还原为V（+3），得到非晶态Li-V-PO 4-F的绿色浆料。当温度升高到550°C时，前驱体开始结晶，在550-650°C下可以得到良好的纯相LiVPO 4F晶体。但在700°C以上烧成的样品中，由于HF气体在高温下的水分存在下挥发，观察到Li 3V 2（PO 4）3杂质。充放电测试表明，在700°C烧结的样品具有最佳的电化学性能，在0.1C倍率下首次放电容量为136 mAhg − 1，在1C倍率下首次放电容量为123 mAhg − 1。即使在5C倍率下，放电容量仍保持在107 mAhg-1，100次循环后保持95.3%。交流阻抗谱分析表明，它具有较小的阻抗比其他样品。用循环伏安法测定了样品中锂离子的表观化学常数。
Carbon coated triclinic LiVPO4F samples are synthesized by annealing the precursor obtained through a soft chemical route with mechanical activation assist. The V(+5) is reduced to V(+3) by oxalic acid dehydrate during ball milling process, and green slurry of amorphous Li–V–PO4–F is obtained. When the temperature rises to 550°C, the precursor starts crystallizing and good crystal of pure-phase LiVPO4F can be obtained at 550–650°C. But Li3V2(PO4)3impurity is observed in samples fired at temperature above 700°C because of the volatilization of HF gas in the presence of moisture at high temperature. Charge–discharge tests show that the sample sintered at 700°C exhibits the best electrochemical performance, delivering the initial discharge capacity of 136 at 0.1C rate and 123mAhg−1at 1C rate. Even at 5C rate, the discharge capacity remains 107mAhg−1and keeps 95.3% after 100 cycles. EIS analysis shows that it possesses smaller impedance than other samples. The apparent chemical coefficient of lithium ions in the prepared sample is evaluated by cyclic voltammetry.