Influence of Y3+ doping on structure and electrochemical performance of layered Li1.05V3O8

LiOH-H2O, V2O5 and Y(NO3)3 were used as raw materials to synthesize the precursors containing Li. V and Y by liquid-state reaction, then the cathode materials Li1.05YxV3-xO8 (x=0, 0.0025, 0.005, 0.01, 0.02, 0.1, 0.2) for lithium-ion battery were obtained by calcining the precursors. The influence of Y3+ doping on structure, conductivity and electrochemical performance of Li1.05V3O8 were investigated by using XRD, cyclic voltammograms, AC impedance, etc. The results show that Li1.05YxV3-xO8 with different doping amounts have well-developed crystal structure of layered Li1.05V3O8 and lengthened interlayer distance of (100) crystal plane. Y3+ can insert into crystal lattice completely when the doping amount is small and the impurity phase of YVO4 is found when x≥0.1. There is no change in the process of Li+ insertion-deinsertion with Y3+ doping. The conductivity is clearly improved due to small amount of Y3+ doping and it tends to increase first and then decrease with increasing doping amount. The initial discharge capacity and plateau potential are both enhanced with proper amount of Y3+ doping. When x is 0.005, the first specific discharge capacity reaches 288.9 mA·h/g, 4.60 % larger than that of undoped sample (276.2 mA·h/g). When x≤0.1. the average discharge plateau potentials are enhanced by about 0.15 V, which makes for higher energy density.