Ng See-How, Tran Nicolas, Bramnik Kirill G, Hibst Hartmut, Novák Petr
Paul Scherrer Institut, Electrochemistry Laboratory, 5232 Villigen PSI, Switzerland.
Chemistry. 2008;14(35):11141-8. doi: 10.1002/chem.200800286.
Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).
通过喷雾干燥技术获得球形Li(1.1)V(3)O(8)前驱体材料，再用Li(2)S进行化学锂化制备了Li(4)V(3)O(8)材料。通过扫描电子显微镜（SEM）和X射线衍射（XRD）对过锂化钒酸盐进行物理表征，并在半电池（相对于锂金属）和全电池（相对于石墨）系统中使用恒电流充放电和循环伏安法进行电化学表征。Li(4)V(3)O(8)材料在空气中稳定长达5小时，在空气中储存的样品几乎没有容量下降。然而，长时间暴露在空气中会严重改变Li(4)V(3)O(8)材料的组成，生成Li(1.1)V(3)O(8)和Li(2)CO(3)。发现这些过锂化钒酸盐的电化学性能对阴极中的导电添加剂（炭黑）含量非常敏感。当添加足够的炭黑时，Li(4)V(3)O(8)阴极表现出良好的循环性能和优异的倍率性能，与Li(1.1)V(3)O(8)前驱体材料相当，即在相对于锂金属的2.0 - 4.0 V电位范围内循环时，在2800 mA g(-1)（8C倍率；1C倍率表示电池在一小时内完全充电或放电）下保持平均充电容量为205 mAh g(-1)。当应用于非优化的全电池系统（相对于石墨）时，Li(4)V(3)O(8)阴极在1.6 - 4.0 V电压范围内、117 mA g(-1)（C/3倍率）的特定电流下循环时，表现出有前景的循环性能，在50次循环后保持高于130 mAh g(-1)的充电容量（Li(+)脱出）。
