V2O5/石墨烯复合电极材料的制备与储锂性能

Preparation and Lithium Storage Performance of V2O5/Graphene Composite Electrode Material

采用溶胶-凝胶法制备了V2O5/石墨烯复合电极材料。利用SEM、XRD、Raman和TGA表征了其微观结构。结果表明,该复合电极材料是含有质量分数0.55%石墨烯的片状正交相V2O5。电化学测试表明,与未复合石墨烯的纯V2O5样品相比,V2O5/石墨烯复合材料具有更高的储锂活性和优异的大电流放电性能。在200 mA/g的电流密度下,V2O5/石墨烯复合材料和纯V2O5样品的放电比容量分别为283和253 mA·h/g;当电流密度增加到5 A/g时,V2O5/石墨烯复合材料依然保持有150 mA·h/g的放电比容量,而纯V2O5样品的放电比容量仅为114 mA·h/g;V2O5/石墨烯和纯V2O5电极的电荷传递电阻分别为142和293Ω。V2O5/石墨烯//Li4Ti5O12全电池测试结果表明,在1.0-2.5 V电压内,循环初期全电池正极材料的放电比容量从110 mA·h/g衰减到96 mA·h/g,随后又出现上升,循环100次后,正极材料的放电比容量稳定在102 mA·h/g,库伦效率接近100%,表明V2O5/石墨烯复合电极材料是一种非常有应用前景的锂离子电池电极活性材料。

V2O5/Graphene composite material was prepared by a facile sol-gel method and characterized by SEM, XRD, Raman spectroscopy and TGA. The results demonstrated that the as-prepared V2O5/Graphene composite material contained 0.55% （mass fraction） graphene and was formed by a two-dimensional sheet-like V205 with orthorhombic structure. The electrochemical measurements revealed that the V2O5/Graphene composite material exhibited higher lithium storage activity and better high rate capability than the pure V205 counterpart. At a current density of 200 mA/g, the V2O5/Graphene composite material delivered a discharge capacity of 283 mA·h/g, which was higher than that of the pure V205 （253 mA·h/g）. When the current density was increased 5 A/g, the discharge capacity of V205/graphene composite material was 150 mA·h/g, whereas that of the pure V205 was only 114 mA·h/g. In addition, the charge transfer resistance of the V2O5/Graphene composite and pure V205 counterpart was 142Ω and 293Ω, respectively. In a voltage range of 1.0-2.5 V, the discharge specific capacity of V2O5/Graphene//Li4Ti5O12 full-cell initially decreased from 110 mA·h/g to 96 mA·h/g and then increased, and stabilized about 102 mA·h/g after 100 cycles. Furthermore, the coulombic efficiency was closed to 100% during charge/discharge cycles. So, the V2O5/Graphene composite material could be used as a promising cathode material for lithium-ion batteries.