Comparison of Li, Na, Mg and Al-ion insertion in vanadium pentoxides and vanadium dioxides

Vanadium oxides (VO) are among the most promising electrode materials for advanced electrochemical batteries since they are able to operate in most major types of batteries (Li, Na, Mg and Al-ion). The practical development of VO electrodes, however, is complicated by the presence of multiple VO stoichiometries and phases with distinctly different lattice stabilities, electronic properties and, hence, metal ion insertion thermodynamics and kinetics. We present a systematic comparative ab initio study of four most stable VO phases (alpha-V2O5, beta-V2O5, VO2(R) and VO2(B)) and their interaction mechanism with Li, Na, Mg, and Al atoms. Our results show that among the studied phases, rutile VO2(R) exhibits the largest Al binding energy and a low Al diffusion barrier, which makes it quite promising for Al-ion batteries. At the same time, the beta-V2O5 phase exhibits the highest binding energy for Mg insertion and significant reduction of the Mg diffusion barrier compared to conventionally used alpha-V2O5. Our results highlight the benefits of rational phase engineering and may assist further experimental studies of high performance VO electrodes for Na, Mg, and Al-ion batteries.