Effect of oxygen vacancy on Li-ion diffusion in a V2O5 cathode: a first-principles study

The energy barriers of lithium-ion mobility in a V2O5 cathode are calculated using the nudged elastic band method. The low activation energy of the hopping pathway along the < 0 1 0 > direction (paralleling with the b-axis, the shortest lattice parameter) indicates that V2O5 has a one-dimensional diffusion pattern at the initial stage of charging and discharging. At a temperature of 300 K, the estimated diffusion coefficient is 2.520 x 10(-8) cm(2) s(-1), which is consistent with the range of diffusivity of the previous reported fast ionic conductors. A systematic investigation of the effect of oxygen vacancy on Li-ion diffusion suggests that the bridging oxygen O(2) plays a very positive role in the Li-ion diffusion along the < 0 1 0 > direction and the activation energy is reduced from 0.340 to 0.215 eV, while the existence of O(1) and O(3) vacancies can hinder the lithium diffusion along this direction due to the increase in the activation energy, respectively. The oxygen vacancies make the energy barriers of the other two potential diffusion pathways reduced to some extent, which is still very large compared with the energy barrier of diffusion along the b-axis.