A process for preparing an alkali metal oxyanion electrode material having a carbon coating deposited by a thermal treatment, said process comprising a thermal step under a humidified atmosphere of: (i) said alkali metal oxyanion electrode material having a carbon coating deposited by a thermal treatment; (ii) precursors of said alkali metal oxyanion electrode material and an organic precursor of carbon; or (iii) said alkali metal oxyanion electrode material and an organic precursor of carbon, wherein said thermal step is performed at a temperature in the range of about 300° C. to about 950° C.