Hollandite cathodes for lithium ion batteries. 1. Synthesis and characterization of the MM ' Mn7O16 compounds (M= K, Ba M = Mg, Mn, Fe, Ni)

BaMMn7O16 (M = Mg, Mn, Fe, Ni) and AMn(8)O(16) (A = Ba, K-2) hollandite oxi des were synthesized in air from metal carbonates and a mixture of simple o xides using the thermal decomposition in solid phase method at 850 degreesC . The oxides BaMn8O16 and BaFeMn7O16 crystallized in the hollandite monocli nic phase, S.G. 12/m and S.G. P2(1)/n respectively, whereas K2Mn8O16 was te tragonal, S.G. 14/m. Two new phases are reported: BaMgMn7O16 and BaNiMn7O16 which crystallize in the hollandite monoclinic phase structure. The ionic distributions were proposed on the basis of several physicochemical analyse s comporting XRD, GTA, magnetic susceptibility and oxidation power measurem ents. Barium and potassium manganites showed Mn3+ and Mn4+ in octahedral si tes whereas BaMMn7O16 (M = Mg, Ni) exhibited Mn2+ and Mn4+ in sites B. On t he other hand, iron-manganese hollanclite, BaFeMn7O16, shows Fe3+ ions besi des Mn3+ and Mn4+ cations.