锂离子二次电池正极材料ε-VOPO4纳米片的制备与表征

摘要

通过水热法合成钒系磷酸盐单斜系VPO4·H2O,通过氧化作用得到ε-VOPO4纳米片.ε-VOPO4纳米片在嵌锂两个过程中与超过1 mol的锂原子发生反应.对制备的ε-VOPO4纳米片进行XRD测试,得到晶胞参数为α=7.2588(4)?;b=6.8633(2)?;c=7.2667(4)?.结果表明,制备的ε-VOPO4纳米片厚度为200 nm且结晶度完美.电化学性能表征结果表明,制备的单斜系 ε-VOPO4纳米片在高电流密度下表现出优越的电化学性能,在电流密度为0.09 mA/cm2情况下的初始放电容量为230.3 mA·h/g.初始放电后,在电流密度为0.6 mA/cm2下经过1000次循环后其容量保持率为73.6%(放电窗口为2.0~4.3 V).%Vanadium (III) phosphate monoclinic VPO4·H2O was synthesized hydrothermally. Theε-VOPO4 nanosheets, formed by the oxidative de-intercalation of protons from monoclinic VPO4·H2O, can reversibly react with more than 1 mol lithium atoms in two steps. Crystal XRD analysis revealed that the structure of theε-VOPO4 nanosheets is monoclinic with lattice parameters ofα=7.2588(4) ?, b=6.8633(2) ? andc=7.2667(4) ?. The results show that theε-VOPO4 nanosheets have a thickness of 200 nm and uniform crystallinity. Electrochemical characterization of theε-VOPO4 monoclinic nanosheets reveals that they have good electrochemical properties at high current density, and deliver high initial capacity of 230.3 mA·h/g at a current density of 0.09 mA/cm2. Following the first charge cycle, reversible electrochemical lithium extraction/insertion at current density of 0.6 mA/cm2 affords a capacity retention rate of 73.6% (2.0?4.3 V window) that is stable for at least 1000 cycles.