不同方法合成LiVPO_4F/C的电化学性能研究

Electrochemical performance of LiVPO_4F/C synthesized by different methods

以葡萄糖、NH4H2PO4、V2O5和LiF为原料,分别通过液相法和固相法合成了锂离子电池正极材料LiVPO4F/C复合材料,并通过X-射线衍射(XRD)、扫描电镜(SEM)及电化学测试技术对复合材料的结构、形貌及电化学性能进行了表征。结果表明,两种方法所合成复合材料均由三斜结构的LiVPO4F与碳组成;液相法所合成的材料首次放电比容量分别为133.7(0.2 C)、124.9 mAh/g(0.5 C)和118.7 mAh/g(1 C),明显高于相同测试条件下固相法所合成材料的首次放电比容量[131.2(0.2 C)、121.4 mAh/g(0.5 C)和104.9 mAh/g(1 C)],并且液相法合成的复合材料循环性能优于固相法合成的复合材料;液相法合成的LiVPO4F/C复合材料具有良好的循环性能和倍率性能,其2 C和5 C的放电比容量分别高达114 mAh/g和98 mAh/g,循环50次后,容量损失率均小于1%。

LiVPO4F/C composite materials were synthesized by solid-state and liquid-phase methods using glucose,NH4H2PO4,V2O5 and LiF as raw materials,and the structure,morphology and electrochemical performance of the composite materials were investigated by X-ray diffraction（XRD）,scanning electron microscope（SEM）,and electrochemical tests.The results show that the composites synthesized by solid-state and liquid-phase methods comprise triclinic LiVPO4F and carbon.The composite prepared by liquid-phase method displays initial discharge specific capacity of 133.7,124.9 mAh/g and 118.7 mAh/g at 0.2 C,0.5 C and 1 C,respectively,higher than that of composite synthesized by solid-state method at the corresponding current rates [131.2 mAh/g（0.2 C）,121.4 mAh/g（0.5 C） and 104.9 mAh/g（1 C）].The composite prepared by liquid-phase method displays better electrochemical performance and capability,its initial discharge specific capacities are 114 mAh/g and 98 mAh/g at 2 C and 5 C,respectively,and the rate of capacity loss is less than 1% after 50 cycles.