LiCoPO4-based ternary composite thin-film electrode for lithium secondary battery

Lithium-excessive LiCoPO4-based thin-film electrodes were fabricated by electrostatic spray deposition (ESD) technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) were used to analyze the structures and Co oxidation state of the electrodes. The electrochemical properties of these electrodes were evaluated by galvanostatic cell cycling. With an excess of lithium in the initial nominal compositions Li1+xCoPO4 (x = 0–1), a LiCoPO4–Li3PO4–Co3O4 ternary composite was obtained after heat treatment. Li3PO4 and Co3O4 were introduced and homogeneously distributed in the LiCoPO4 matrix. We have obtained distinct two-step feature of the voltage plateaus at 4.8 and 4.9 V, high specific capacity and excellent cycling performance for this “5 V”-electrode material. The presence of Co3O4 in the electrode can enhance its electronic conductivity and increase the capacity, while Li3PO4 can act as an electrolyte separation layer and improve the cycling performance of cells with electrolyte LiPF6 (EC–DEC, 1:1 v/v).