Synthesis of LiVOPO4 for cathode materials by coordination and microwave sintering

Lithium vanadyl phosphate (LiVOPO4) sample, as one potential cathode materials, was synthesized via a route of coordination and microwave sintering. The precursors were prepared by coordination reactions among LiOH.H2O, NH4VO3, NH4H2PO4, C6H8O7.H2O and a small amount of water, and then they were sintered in a microwave furnace at 600 deg. C for 50 min. X-ray diffraction (XRD) results confirmed the formation of crystallized LiVOPO4 with orthorhombic structures belonging to the space group of Pnma. Scanning electron microscopy (SEM) measurements indicated that the average particle size was less than 500 nm. After undergone an 'activation' process, the sample exhibited a high discharge capacity for about 154 mA h g-1 by the 22nd cycle at a current of 18.5 mA g-1, which was very close to the theoretical values. Though the discharge capacity decreased obviously with the increased current, 110 as well as 80 mA h g-1 can still be sustained within 40 cycles at 38 and 75 mA g-1 respectively. This paper showed that submicron-sized LiVOPO4 materials prepared through above way should be prospective for the application to 4 V system of lithium ion batteries.