Carbon-coated Li3V2(PO4)(3) composite cathode material for lithium-ion batteries: Sol-gel synthesis and performance

A carbon-coated Li3V2(PO4)(3) Composite cathode material was synthesized by a sol-gel method using V2O5, LIOH center dot H2O, H2O2, NH4H2PO4 and citric acid as starting materials. Properties of the prepared composite material were investigated using XPS, XRD, SEM, Raman spectroscopy, TEM, and various electrochemical techniques. The relationship among structure, calcination temperature, electronic conductivity and the electrochemical performance of samples was also studied. The sample obtained had a monoclinic structure with a space group of P2(1)/n and a rough and porous carbon surface layer. The electronic conductivity of the carbon-coated Li3V2(PO4)3 samples synthesized at 800 degrees C was about a factor of similar to 10(4) higher than that of carbon-free Li3V2(PO4)(3) prepared by solid-state hydrogen reducing reaction. The results show that the carbon-coated Li3V2(PO4)(3) is superior in the electrochemical performance to the carbon-free sample. In the voltage range of 3.0 similar to 4.3 V, the carbon-coated Li3V2(PO4)(3) synthesized at 800 degrees C displays large reversible capacities (128 mAh center dot g(-1) at 0.1C and 109 mAh center dot g(-1) at 2C, respectively) and excellent cyclic stability. The reason for the excellent electrochemical performance of the carbon coated Li3V2(PO4)(3) is discussed.