A Feasibility Study on the Use of Li4V3O8 as a High Capacity Cathode Material for Lithium-Ion Batteries

Li4V3O8 materials have been prepared by chemical lithiation by Li2S of spherical Li1.1V3O8 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 Li4V3O8 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 Li4V3O8 materials, resulting in both Li1.1V3O8 and Li2CO3. 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 Li4V3O8 cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li1.1V3O8 precursor material, that is, retaining an average charge capacity of 205 mAhg(-1) at 2800 mAg(-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 Li4V3O8 cathode showed promising cycling behaviour, retaining a charge capacity (Li+ extraction) above 130 mAhg(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mAg(-1) (C/3 rate).