Preparation and electrochemical performance studies on Cr-doped Li3V2(PO4)3 as cathode materials for lithium-ion batteries

Cr-doped Li3V2-xCrx(PO4)3/C (x = 0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol-gel method. The Rietveld refinement results indicate that single-phase Li3V2-xCrx(PO4)3/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li3V2-xCrx(PO4)3/C. Li3V1.9Cr0.1(PO4)3/C compound presents an initial capacity of 171.4 mAh g-1 and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li3V1.9Cr0.1(PO4)3/C can give an initial capacity of 130.2 mAh g-1 and 10.8% capacity loss after 100 cycles where the Li3V2(PO4)3/C presents the initial capacity of 127.4 mAh g-1 and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x = 0.1) in V sites.