Ab initio study of Li, Mg and Al insertion into rutile VO: fast diffusion and enhanced voltages for multivalent batteries.

Vanadium oxides are among the most promising materials that can be used as electrodes in rechargeable metal-ion batteries. In this work, we systematically investigate thermodynamic, electronic, and kinetic properties associated with the insertion of Li, Mg and Al atoms into rutile VO. Using first-principles calculations, we systematically study the structural evolution and voltage curves of LiVO, MgVO and AlVO (0 < x < 1) compounds. The calculated lithium intercalation voltage starts at 3.50 V for single-atom insertion and decreases to 2.23 V for full lithiation, to the LiVO compound, which agrees well with the experimental results. The Mg insertion features a plateau about 1.6 V up to MgVO and then another plateau-like region at around 0.5 V up to MgVO. The predicted voltage curve for Al insertion starts at 1.98 V, followed by two plateaus at 1.48 V and 1.17 V. The diffusion barrier of Li, Mg and Al in the tunnel structure of VO is 0.06, 0.33 and 0.50 eV, respectively. The demonstrated excellent Li, Mg and Al mobility, high structural stability and high specific capacity suggest promising potential of rutile VO electrodes especially for multivalent batteries.