The Role of Ternary Phases in Cathode Reactions

The cell reactions between lithium and several transition metal oxides and sulfides have been found to produce ternary phases and not the formation of lithium oxide or sulfide as previously proposed. These reactions, at 25°C, take place with essential retention of the crystalline lattice, thus facilitating secondary cathodic behavior. It is found that cell reversibility is optimized when no chemical bonds are broken during discharge, that is, where ternary phases are formed by an intercalation reaction and where a broad range of nonstoichiometry exists as in the system . Where some chemical bonds are broken as for and partial or difficult reversibility is found, but when all the bonds are broken as for example in , the cell only exhibits primary characteristics.