The study of carbon-coated V2O5 nanoparticles as a potential cathodic material for Li rechargeable batteries

Carbon-coated V2O5 nanoparticles (CCV2O5) are good candidates as cathodic materials for rechargeable Li batteries. These nanoparticles were prepared by burning off carbon-coated V2O3 nanoparticles in air (around 400 degrees C). The V2O3 nanoparticles were prepared by a simple, single-stage reaction under autogenic pressure. Variations in the conditions of the burning process determine the properties of the carbon coating (e.g., thickness, weight % of carbon). Several types of electrodes were investigated. These included composite electrodes comprising different batches of CCV2O5, additional carbon particles and PVdF binder, composite electrodes comprising micrometric size, commercial V2O5 as the active mass, and electrodes in which the CCV2O5 or micronic size V2O5 particles were embedded in aluminum foils without using any carbon additive or binder. The electrochemical response in terms of capacity, cyclability, and rates (up to 5C) at different potential ranges (narrow 3-4 V and wide 2-4 V domains, vs Li/Li+) was investigated in LiClO4 1 M and in LiPF6 1 M ethylene carbonate/dimethyl carbonate solutions by standard electrochemical techniques, including chronopotentiometry, cyclic voltammetry, and impedance spectroscopy. The behavior of the CCV2O5 electrodes (nanoparticles) was compared to that of electrodes comprising micronic size V2O5 particles. In general, CCV2O5 electrodes demonstrated a higher capacity, much better rate capability, and very good stability upon cycling and aging at elevated temperatures compared to electrodes comprising microparticles of V2O5. In situ and ex situ atomic force microscopy imaging was used for the morphological analysis of these electrodes. (C) 2007 The Electrochemical Society.