Synthesis and performance of Li3(V1-xMgx)2(PO4)3 cathode materials

In order to search for cathode materials with better performance, Li-3(V1-xMgx)(2)(PO4)(3) (0, 0.04, 0.07, 0.10 and 0.13) is prepared via a carbothermal reduction (CTR) process with LiOH center dot H2O, V2O5, Mg(CH3COO)(2)center dot 4H(2)O, NH4H2PO4, and sucrose as raw materials and investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM) and electrochemical impedance spectrum (EIS). XRD shows that Li-3(V1-xMgx)(2)(PO4)(3) (x = 0.04, 0.07, 0.10 and 0.13) has the same monoclinic structure as undoped Li3V2(PO4)(3) while the particle size of Li-3(V1-xMgx)(2)(PO4)(3) is smaller than that of Li3V2(PO4)(3) according to SEM images. EIS reveals that the charge transfer resistance of as-prepared materials is reduced and its reversibility is enhanced proved by the cyclic votammograms. The Mg2+-doped Li3V2(PO4)(3) has a better high rate discharge performance. At a discharge rate of 20C, the discharge capacity of Li-3(V0.9Mg0.1)(2)(PO4)(3) is 107 mAh g(-1) and the capacity retention is 98% after 80 cycles. Li-3(V0.9Mg0.1)(2)(PO4)(3)//graphite full cells (085580-type) have good discharge performance and the modified cathode material has very good compatibility with graphite. (C) 2010 Elsevier B.V. All rights reserved,