Mn2o3

Li₃NbO₄ was prepared by solid-state reaction from stoichiometric amounts of Li₂CO₃ (> 98.5%; Kanto Kagaku) and Nb₂O₅ (99.9%; Wako Pure Chemical Industries) at 950 °C for 24 h in air. Li_1.3Nb_0.3Me_0.4O₂ (Me=Fe³⁺, Mn³⁺ and V³⁺) samples were prepared from Li₂CO₃, Nb₂O₅ and precursors containing each transition metal: Mn₂O₃, Fe₂O₃ (99.9%; Wako Pure Chemical Industries), V₂O₃ (98%; Sigma-Aldrich Japan). Mn₂O₃ was obtained by heating of MnCO₃ (Kishida Chemical) at 700 °C for 12 h. The precursors were thoroughly mixed by wet mechanical ball milling and then dried in air. Thus obtained mixtures of the samples were pressed into pellets. The pellets were heated at 900 °C for 12 h in air (Fe³⁺) or inert atmosphere (Mn³⁺ and V³⁺). The samples were stored in an Ar-filled glove box until use.
Li_1.2Ti_0.4Mn_0.4O₂ was prepared from Li₂CO₃, TiO₂ (Anatase, 98.5%; Wako Pure Chemical Industries), and Mn₂O₃. The precursors were thoroughly mixed by wet mechanical ball milling and the mixture was heated at 900 °C for 12 h in inert atmosphere. Particle morphology of the samples was observed using a scanning electron microscope (JCM-6000, JEOL) with acceleration voltage of 15 keV.