Influence of sol–gel derived lithium cobalt phosphate in alkaline rechargeable battery

Abstract

A lithium cobalt phosphate (LiCoPO4) cathode was synthesised by citric acid assisted sol–gel method and its electrochemical behaviour in alkaline secondary battery (using novel lithium hydroxide as the electrolyte) is reported. The sol–gel method using metal acetate precursors with citric acid as a chelating agent influenced the particle size and the homogeneity while yielding a single phase LiCoPO4 at a considerably lower temperature and shortened heating time, compared to that of the conventional solid state reaction. The cyclic voltammogram of LiCoPO4 showed a reversible redox process implying that de-intercalation and intercalation of lithium can occur in aqueous electrolyte. This was supported by X-ray diffraction (XRD) and Infra-red (IR) studies. The charge–discharge performance of the Zn/LiCoPO4 battery showed good capacity retention (after 25 cycles it delivered 90 % of its initial capacity). This enhanced capacity retention was attributed to the synergistic effect of particle homogeneity, reduced Li+ diffusion path and stability of the non-reactive aqueous electrolyte between the electrode and the electrolyte interface.