The LiFe(1-x)VxPO4/C Composite Synthesized by Gel-Combustion Method, with Improved Rate Capability and Cycle Life in Aerated Aqueous Solutions

Abstract

The nitrate-(glycine + malonic acid)-assisted gel-combustion process, followed by a heat treatment at 750 °C under reductive atmosphere, was used as a fast and effective way to synthesize vanadium doped olivine incorporated in carbon matrix, of general formula LiFe(1−x)VxPO4/C. The two-phased Rietveld refinement confirmed that vanadium incorporation into olivine structure was complete. The heating under reduction atmosphere caused the formation of iron phosphide to some extent, the concentration was determined by Rietveld analysis. The capacity and rate capability of these composites were tested by both cyclic voltammetry and galvanostatic cycling. Specifically, the average discharging capacities of the composite with x = 0.055, determined in an saturated aqueous LiNO3 solution equilibrated with air, at the rates of 1, 10 and 100 C, amounted to 91, 73 and 35 mAh g−1, respectively, with no perceivable capacity fade.