It was demonstrated 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 was heated under O2/H2O at 460C had 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. It was concluded that heating under O2/H2O introduced defects, such as cation vacancies associated with lithiated O sites, which could electrochemically exchange Li ions and serve as additional charge-storage sites. This could also explain how metal oxides synthesized from sol–gels, such as xerogels and aerogels, inserted Li ions without a concomitant reduction in transition-metal ion sites; high surface-area metal oxides were likely to be non-stoichiometric and rich in surface point defects which could serve as additional charge-storage sites.

Improved Lithium Capacity of Defective V2O5 Materials. K.E.Swider-Lyons, C.T.Love, D.R.Rolison: Solid State Ionics, 2002, 152-153, 99-104