improvements in voltage and energy density*

Vanadium oxides (VO) are among the most promising materials that can be used as electrodes in multivalent rechargeable batteries. VO can be used as electrode materials for Al ion batteries although voltages reported to date are rather low, leading to low energy density. We explore amorphization as a strategy to increase voltage and compare Al insertion into amorphous vs crystalline VO₂ . The amorphous structure is generated using a customized force field, and Al insertion is then studied by first-principles calculations. We show Al insertion in amorphous VO₂ can occur at insertion sites with well-dispersed insertion energies, with the lowest energy site much more thermodynamically favourable than any insertion site in the crystalline VO₂. We compute the voltage-composition profile for amorphous VO₂ and show that amorphization increases the average voltage of VO₂ cathode, which will lead to higher energy density. We also suggest that the stability of amorphous VO₂ cathode is improved by reducing volume expansion during Al insertion, potential leading to longer cycle life in practical applications. Overall, the demonstrated improvements suggest a high potential of amorphous VO₂ electrodes for multivalent batteries.