Using the electrochemical-hydrothermal method, Al-substituted MnO2 materials with alpha- or gamma-structures or mixtures of these phases have been synthesized. The Al-substituted materials are highly disordered and are characterized by a large amount of microtwinning defects compared to non substituted ones synthesized under the same conditions. The effect of the presence of aluminum on the physico-chemical, structural and morphological properties are presented. The presence of Al-III allows obtaining "interconnected nanowires" of Mn1-yAlyO2-delta with very high surface areas. The lithium insertion properties of the Al-substituted gamma-MnO2 materials are discussed by comparison to non substituted ones. (c) 2006 Elsevier B.V. All rights reserved.