The enhanced cycling stability and rate capability of sodium-modified Li3VO4 anode material for lithium-ion batteries

Na-doped lithium vanadates Li3−xNaxVO4 (x = 0, 0.03, 0.05, and 0.08) were synthesized as anode materials for lithium-ion batteries by a simple sol-gel method. The structural and morphological characterizations reveal that Na-doping in Li3VO4 leads to slightly expanded lattice and suppressed particle agglomeration with relative uniform morphology and the doped Na+ ions distributed uniformly throughout Li3VO4 grains. The Na-doped Li3VO4 electrodes present enhanced cycling stability, better rate performance and lower charge transfer resistance, especially for the Li2.95Na0.05VO4 electrode. It delivers the highest initial charge capacity of 523.4 mAh/g at 0.1C in the series electrodes. After 150 cycles at 1C, Li2.95Na0.05VO4 electrode maintains a charge capacity of 398.3 mAh/g, which is almost the same with that of the initial one. In addition, Li2.95Na0.05VO4 electrode also exhibits a much better rate capability with 364 and 284 mAh/g at 2C and 4C, respectively, superior to that of Li3VO4. The excellent electrochemical performance of the Na-doped samples is suggested to originate from the much higher lithium diffusion coefficient induced by the expanded lattice, the much smaller polarization and charge transfer resistance.