Mo(VI) and W(VI) substituted Lin+xMoyV3-yO8 and Lin+xWyV3-yO8 where y less than or equal to 0.25, were synthesized by solid state reactions. Lithium insertion in these phases from organic electrolytes during electrochemical reaction was investigated. Oxides of the composition Lin+xMoyV3-yO8 with a molybdenum content in the structure near the upper concentration limit (0.2 less than or equal to y < 0.25) exhibit high discharge capacities. For the strongly crystalline Li1+xV3O8-like host structure (x = 3), the discharge capacity is close to the theoretical value. Intercalation mechanism, based on the ordering process in the lithium superlattice, has been proposed for this type of solid solution.