The structural arrangement of g-MnO 2 is currently explained by a random intergrowth of pyrolusite layers in a ramsdellite matrix. The structures of a large variety of g-MnO 2 samples with various structural parameters Pr were studied by x-ray powder diffraction and Raman scattering spectroscopy. We show that elucidation of the quantitative determination of the structural disorder present in g-MnO 2 is accurate by Raman scattering spectroscopy. The Raman data for manganese dioxides with the g-type structure are treated by a local environment model, which allows one to consider the relationship between the band wavenumber and the pyrolusite intergrowth that corresponds to the structural De Wolff defects.

The lithiated nickel-cobalt oxide LiNi 0.5 Co 0.5 O 2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi 0.5 Co 0.5 O 2 products calcined at 400-600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi 0.5 Co 0.5 O 2 compounds. Thermal (TG-DTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO 4 in propylene carbonate, PC). The LiNi 0.5 Co 0.5 O 2 positive electrodes fired at 600°C exhibited good cycling behavior.

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