(Invited) Vanadium Based Phosphate, Phosphite, Oxalate Cathode Materials for Lithium Batteries

Abstract

Commercial lithium ion batteries (LIBs) use layer-type compounds, lithium cobalt oxide (LiCoO2) or LiFePO4 as the cathode (positive electrode) and graphite (C) as the anode (negative electrode) material, and a non-aqueous Li- ion conducting electrolyte. The liquid electrolyte in the form of a solution or immobilized in a gel-polymer. LIBs with an operating voltage of 3.6 V are extensively used in the present-day portable electronic devices like, cell phones and other low power operated devices. For high-power applications like, electric/hybrid electric vehicles and back-up power supplies and, the LIBs need to satisfy several criteria, namely, cost-reduction, improvement in the energy density, safety-in-operation at high current charge/discharge rates and improvement in the low-temperature-operation. To satisfy the above criteria, researches are being carried out worldwide to find alternative cathode materials.In my presentation, I will discuss our group studies on V-based Flouro phosphates cathode materials. Specifically, I will focus bare and Fe doped-LiVPO4F, αI-LiVOPO4 and V-based metal organic framework materials, MX[(VO)2N2(C2O4)], where M= K, Li, Na , N= HPO4, HPO3. and LiSiV2O6. Materials were prepared variety of chemical methods carbothermal/Graphenothermal reduction, hot plate and hydrothermal methods. Materials were characterized by Rietveld refinement X-ray diffraction, X-ray photoelectron spectroscopy, Raman, XPS, Microscopy (SEM &TEM) and BET surface area methods. Electro analytical studies like cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy techniques. Interestingly V-based cathodes showed around 4 V redox couple (except LiSiV2O6) which is higher than that of LiFePO4 (3.5V vs. Li) and observed reversible capacity is order 80-140 mAh/g. Discuss in detail long term cycling studies and rate capabilities and reaction mechanisms. Keywords: Materials synthesis; Batteries; Cathodes; Electrochemical Properties; Energy storage