Studies of the layered manganese bronzes, Na2/3[Mn1−xMx]O2 with M=Co, Ni, Li, and Li2/3[Mn1−xMx]O2 prepared by ion-exchange

Layered sodium manganese bronzes, Na2/3MO2 (M=Mn1−xAx, A=Co, Li, Ni) with the P2-structure were investigated. A phase diagram (composition–structure–temperature diagram) for materials synthesized in air is presented. Substitution extends the stability region of P2 phases toward lower temperatures. Na2/3MnO2 exhibits a monoclinic distortion. Weakly substituted samples exhibit an orthorhombic distortion of the ideal P2-structure whereas heavily substituted bronzes adopt the ideal P2-structure. Dry samples exhibit larger distortions than samples exposed to air. The layered sodium bronzes were used to prepare layered Li-transition metal oxides by ion-exchange. Layered Li–Mn oxides with O2-structures were prepared from these bronzes for the first time. As an example crystalline Li2/3[Ni1/3Mn2/3]O2 with the O2 structure was prepared.