锂离子电池纳米ε-VOPO_4正极材料的合成与电化学性能

Synthesis and electrochemical characteristics of cathode material nanostructured ε-VOPO_4 for lithium-ion batteries

以V2O5、H3PO4为原料，在V2O5与H3PO4摩尔比为1：2.4条件下通过水热法制备VOPO4？xH2O，得到的VOPO4？xH2O再通过650℃煅烧制备纳米结构ε-VOPO4，通过X射线衍射对制备材料进行表征。采用SEM对产物形貌进行观察，考察原料配比条件对产物组成和晶相的影响；对纳米ε-VOPO4进行电化学性能测试。结果表明：在该条件下制备出的纳米ε-VOPO4物相纯；所制备纳米结构的ε-VOPO4颗粒粒径为200 nm，且颗粒度均匀；在0.2C倍率、电压范围为2.0～4.3 V充放电制度下，首次充电比容量可以达到227.9 mA·h/g,在0.5C倍率充放电制度下循环140次后，放电容量达160.49 mA·h/g。

VOPO4·xH2O was obtained through hydro-thermal method with V2O5 and H3PO4 as initial materials. Nanostructuredε-VOPO4 was synthesized from VOPO4·xH2O heated at 650℃when molar ratio of V2O5 to H3PO4 is 1：2.4. The nanostructed ε-VOPO4 has been characterization by X-ray. The product morphology was studied by SEM. The results show that the nanostructuredε-VOPO4 is pure with particle size of about 200 nm. The effects of the molar ratio of the initial reaction materials on the product components and crystal structure were studied. And the electrochemical performance of the nanostructured ε-VOPO4 was also studied. The best electrochemical performance and crystal of the obtained nanostructured ε-VOPO4 is from that molar ratio of the V2O5 and H3PO4 is 1：2.4. The particle size of the nanostructured ε-VOPO4 was about 200 nm. The nanostructured ε-VOPO4 exhibits an initial discharge capacity of 227.9 mA·h/g at 0.2C rate in the voltage window of 2.0-4.3 V. The discharge capacity is as high as 160.49 mA·h/g at the rate of 0.5C after the 140th cycle.