Abstract:The carbon-coated monoclinic Li₃V₂(PO₄)₃ (LVP) cathode materials were successfully synthesized by liquid phase method using PEG as reducing agent and carbon source. The effects of relative molecular mass of PEG on the properties of Li₃V₂(PO₄)₃/C were evaluated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical performance tests. The SEM images show that smaller size particles are obtained by adding larger and smaller PEGs. The electrochemical cycling of Li₃V₂(PO₄)₃/C prepared by both PEG200 and PEG20k has a high initial discharge capacity of 131.1 mA·h/g at 0.1C during 3.0-4.2 V, and delivers a reversible discharge capacity of 123.6 mA·h/g over 30 cycles, which is better than that of other samples. The improvement in electrochemical performance is caused by its improved lithium ion diffusion coefficient for the macroporous morphology, which is verified by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Key words: lithium-ion battery; lithium vanadium phosphate; PEG; carbon-coating; liquid phase method