Ab initio study of Li, Mg and Al insertion into rutile VO2: Fast diffusion and enhanced voltages

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 in rutile VO2. Using first-principles calculations, we systematically study the structural evolution and voltage curves of LixVO2, MgxVO2 and AlxVO2 (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 LiVO2 compound, which agrees well with experimental results. The Mg insertion features a plateau about 1.6 V up to Mg0.5VO2 and then another plateau-like region at around 0.5 V up to Mg1VO2. 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 VO2 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 a promising potential of rutile VO2 electrodes especially for multivalent batteries.