부산대학교 도서관

Vanadate-based compounds, in particular LiV3O8, are promising candidates for cathode materials of Li-ion batteries. Thanks to their open-layered structures and the various possible oxidation states of the V metal center, LiV3O8can effectively accommodate Li ions and store electron potential. To further improve the transport kinetics of the cathode, in this work, we used the first-principles method to explore the effects of oxygen vacancies on Li insertion, Li diffusion, and electronic conduction in the form of polaron hopping. We find that the polaron is mobile in the [010] direction with an effective hopping barrier, Ea,eff, of 0.11 eV and is sluggish in other directions with an Ea,effof 0.56 eV. Such anisotropic conduction is also observed in experiments. Interestingly, unlike other transition metal oxides, formation of a polaron negligibly affects Li insertion and diffusion, where the charge transport kinetics is solely limited by the ion movement with an Ea,effof 0.50 eV. The introduction of an oxygen vacancy, VO, creates two polarons at the two nearby V centers where at least one of them is relatively mobile (Ea,eff= 0.16 eV) contributing to electronic conductivity of the materials. At low VOconcentrations of up to 1%, the most stable VOexists far from the Li diffusion path and does not affect the ion transport kinetics. In contrast, if the VOconcentration increases to 2–3%, the second most stable VOstarts to form at the diffusion path, which greatly diminishes Li diffusion. Hence, it is suggested that controlling the low concentration of VOwithin 1% can enhance electronic conductivity by increasing the concentration of charge carriers while maintaining the ion diffusivity of the LiV3O8cathode.