Effects of V2O5 nanowires on the performances of Li2MnSiO4 as a cathode material for lithium-ion batteries

Abstract

The effects of vanadium pentoxide on the electrochemical properties of Li₂MnSiO₄ as a cathode material for lithium-ion batteries were tested by synthesizing a V₂O₅ nanowire-modified in situ carbon coated Li₂MnSiO₄ composite (LMS/C/V₂O₅) and comparing its performances with that of a Li₂MnSiO₄ composite without V₂O₅. In LMS/C/V₂O₅, the V₂O₅ nanowires, with diameters of around 10–20 nm and lengths up to tens of micrometers, entangled together and formed a 3D conductive network; the Li₂MnSiO₄ nanoparticles, with sizes around 30 nm, distributed uniformly in the network frame and tended to adhere to the V₂O₅ nanowires. In this structure, the LMS/C/V₂O₅ composite showed a superior performance as a cathode of lithium-ion batteries even with very low carbon content (3.4 wt%). Ex situ X-ray diffraction patterns, electrochemical impedance spectroscopies of the electrodes and the concentration of Mn ions in the electrolyte during the charge–discharge processes explained the effects of the V₂O₅ nanowires as an additive in the Li₂MnSiO₄ cathode material. The benefits of the nanowires include maintaining the crystal structure of Li₂MnSiO₄ during the charge–discharge cyclings, reducing the charge-transfer resistances at the solid–electrolyte interfaces, increasing the lithium ions diffusion coefficient in the cathode and alleviating the dissolution of manganese into the electrolyte of the batteries.