Mo⁶⁺ Doping in Li₃VO₄ Anode for Li-Ion Batteries: Significantly Improve the Reversible Capacity and Rate Performance

Abstract

Consider the almost insulator for pure Li₃VO₄ with a band gap of 3.77 eV, to significantly improve the electrical conductivity, the novel Li₃V_1-xMo_xO₄ (x = 0.00, 0.01, 0.02, 0.05, and 0.10) anode materials were prepared successfully by simple sol-gel method. Our calculations show that, by substitute Mo⁶⁺ for V⁵⁺, the extra electron occupied the V 3p empty orbital and caused the Fermi level shift up into the conduction band, where the Mo-doped Li₃VO₄ presents electrical conductor. The V/I curve measurements show that, by Mo doping in V site, the electronic conductivity of the Li₃VO₄ was increased by 5 orders of magnitude. And thence the polarization was obviously reduced. EIS measurement results indicated that by Mo-doping a higher lithium diffusion coefficient can be obtained. The significantly increased electronic conductivity combined the higher lithium diffusion coefficient leads to an obvious improvement in reversible capacity and rate performance for the Mo-doped Li₃VO₄. The resulting Li₃V_1-xMo_xO₄ (x = 0.01) material exhibited the excellent rate capability. At a high rate 5 C, a big discharge capacity of the initial discharge capacity 439 mAh/g can be obtained, which is higher than that of pure Li₃VO₄ (only 166 mAh/g), and after 100 cycles the mean capacity fade is only 0.06% per cycle.