Enhanced Electrochemical Properties of Li3VO4 with Controlled Oxygen Vacancies as Li-Ion Battery Anode

Li3VO4, as a promising intercalation-type anode material for lithium-ion batteries, features a desired discharge potential (ca. 0.5-1.0 V vs. Li/ Li+) and a good theoretical storage capacity (590 mAhg(-1) with three Li+ inserted). However, the poor electrical conductivity of Li3VO4 hinders its practical application. In the present work, various amounts of oxygen vacancies were introduced in Li3VO4 through annealing in hydrogen to improve its conductivity. To elucidate the influence of oxygen vacancies on the electrochemical performances of Li3VO4, the surface energy of the resulting material was measured with an inverse gas chromatography method. It was found that Li3VO4 annealed in pure hydrogen at 400 degrees C for 15 min exhibited a much higher surface energy (60.7 mJm(-2)) than pristine Li3VO4 (50.6 mJm(-2)). The increased surface energy would lower the activation energy of phase transformation during the charge-discharge process, leading to improved electrochemical properties. As a result, the oxygen-deficient Li3VO4 achieved a significantly improved specific capacity of 495 mAhg(-1) at 0.1 Ag-1 (381 mAhg(-1) for pristine Li3VO4) and retains 165 mAhg(-1) when the current density increases to 8 Ag-1.