Materials are presented of the formula: Ax My Mizi O2−d, where A is sodium or a mixed alkali metal including sodium as a major constituent; x>0; M is a metal or germanium; y>0; Mi, for i=1, 2, 3 . . . n, is a transition metal or an alkali metal; zi≧0 for each i=1, 2, 3 . . . n; 0 2−d. The formula includes compounds that are oxygen deficient. Further the oxidation states may or may not be integers i.e. they may be whole numbers or fractions or a combination of whole numbers and fractions and may be averaged over different crystallographic sites in the material. Such materials are useful, for example, as electrode materials in rechargeable battery applications. Also presented is a method of preparing a compound having the formula Ax My Mizi O2−d.