Enhancement of discharge capacity of Li3V2(PO4)3 by stabilizing the orthorhombic phase at room temperature

Li3V2(PO4)(3) and solid solutions of Li3-2x(V1-x,Zr-x)(2)(PO4)(3) were prepared by a solid state reaction. A high temperature orthorhombic phase of Li3V2(PO4)(3) with a beta -Fe-2(SO4)(3)-type was successfully stabilized at room temperature by substituting Zr for V with substitution ratios beyond x = 0.05. The pure material of Li3V2(PO4)(3) exhibited a cathode performance with two well defined regions of plateau at around 3.7 and 4.1 V vs. Li/Li+ upon charging and 3.6 and 4.0 V vs. Li/Li+ upon discharging, respectively, suggesting two types of phases produced upon the charge/discharge process. On the other hand, the cathode performance of the orthorhombic stabilized materials showed almost the same charge/discharge voltages as those of the pure material, but, with two plateaus slightly sloping, showed a considerably improved charge/discharge cycle performance compared to that of the purl material. Such improvement on the charge/discharge cycle performance is suggested to come from the disordered lithium ion arrangement in the orthorhombic phase. (C) 2000 Elsevier Science B.V. All rights reserved.