Improved lithium capacity of defective V2O5 materials

We demonstrate that point defects may be introduced into a metal oxide to increase its Li-ion capacity by using various heat treatments to modify the defect structure of polycrystalline V2O5 and then comparing the Li capacity of the materials. The V2O5 that is heated under O2/H2O at 460 °C has a 23% higher Li capacity than the as-received material despite no change to its long-range structure. Other heating conditions lower the Li capacity of the V2O5. We infer that heating under O2/H2O introduces defects, such as cation vacancies associated with lithiated oxygen sites, which can electrochemically exchange Li ions and serve as additional charge-storage sites. This study may also explain how metal oxides synthesized from sol–gels, such as xerogels and aerogels, insert lithium ions without concomitant reduction of transition-metal-ion sites—high-surface-area metal oxides are likely to be nonstoichiometric and rich with surface point defects which can serve as additional charge-storage sites.