The incorporation of vanadium into olivine LiFePO4/C: improvement of lithium intercalation from both organic and aqueous electrolyte

Abstract

The simple and fast (malonic acid+glycine)-assisted gel-combustion process, followed by a heat treatment at 750oC under reductive atmosphere, is found to be a very effective way for the synthesis of (V-doped LiFePO4)/C composites. The Rietveld refinement confirms that vanadium incorporation into olivine structure was accompanied by the formation of iron phosphide conducting phase. The coulombic capacity and rate capability of (V-doped LiFePO4)/C composite, in both organic and aqueous electrolyte solutions, were significantly improved relative to an undoped sample, as revealed by both galvanostatic cycling and cyclic voltammetry. The average discharging capacities of ~5mol.%V-doped LiFePO4/C composite in an aqueous LiNO3 solution were 91, 73 and 35 mAh g-1 at 1, 10 and 100 C, respectively, with no perceivable capacity fade upon 100 charging/discharging cycles.