Three-colored electrochromic lithiated vanadium oxides: the role of surface superoxides in the electro-generation of the red state

Lithiated vanadium oxides with polyelectrochromic behaviour are reported here for the first time. Electrochrome was obtained by means of a simple and solvent-free solid state reaction. Clear XPS evidence indicates that the electro-generation of the red color is due to the dismutation of surface-adsorbed O₂⁻ species with subsequent formation of red colored V⁵⁺–O₂²⁻ complexes. The reaction is switched electrochemically by oxidation of the surface V⁴⁺ centers.