溶胶-凝胶法合成锂离子电池正极材料LiV_3O_8

Preparation of LiV_3O_8 by Sol-Gel Method

用体积分数为10％的H_2O_2和V_2O_5反应得到的V_2O_5·nH_2O湿凝胶,与Li_2CO_3反应得LiV_3O_8沉淀,经400℃焙烧后得LiV_3O_8产品。与传统的高温固相反应相比,合成方法温度较低、产品粒度较细。前驱体和产品用热分析法、X射线衍射法、元素分析技术进行表征。采用恒电流充放电法、循环伏安法、交流阻抗技术对样品进行电化学性能测试;利用平面电极的半无限扩散阻抗模型,计算锂在活性材料LiV_3O_8中的化学扩散系数D_(Li)。结果表明,活性材料LiV_3O_8在0.1C的放电倍率和3.6～1.8 V的电压范围内具有较高的放电容量,循环20次后仍保持有225 mA·h/g的放电比容量;化学扩散系数D_(Li)的变化范围为1×10^(-8)～1×10^(-11)cm^2/s,数量级。

Lithium vanadium oxide LiV_3O_8 was synthesized by a sol-gel method followed by calcination. The V_2O_5·nH_2O hydro-gel was prepared by reacting V_2O_5 with 10% H_2O_2, and aged for 4 days at room temperature. The LiV_3O_8 precursor was obtained from V_2O_5·nH_2O hydro-gel and Li_2CO_3 and dried at 120℃, and the LiV_3O_8 was obtained after calcination at 400℃ for 20h. Compared with the conventional high temperature solid phase reaction methods, this method has the advantages of the lower synthesis temperature and smaller particle size of the product. The precursor and product were characterized by DTA-TG, XRD and ICP measurements. Electrochemical behavior of the LiV_3O_8 as a cathode material for rechargeable lithium-ion battery was studied by galvanostatic charge-discharge, cyclic voltammetry, and A. C. impedance techniques. The chemical diffusion coefficient(D_(Li)) of lithium was calculated by semi-infinite diffusion impedance model the range of 1×10^(-8)～1×10^(-11)cm^2/s. The results showed that the active material LiV_3O_8 has a specific discharge capacity of 225 mA·h/g at 0.1C rate and voltage limits of 1.8～3.6 V during 20 cycles.