Layered Li–Mn oxides with the O2 structure: preparation of Li2/3[Mn1−xMx]O2 (M=Li, Cr, Mg, Al) by ion exchange

Layered sodium manganese bronzes, Na2/3[Mn1−xMx]O2 (M=Li, Cr, Mg, Al) with the P2 structure have been investigated. In the case of M=Li, the location of the dopant was identified on the basis of ion-exchange properties and chemical analysis. With the increase doped Cr content, the P2-structure Na2/3[Mn1−xCrx]O2 gradually underwent a transformation to orthorhombic Na4[Mn9−yCry]O18. X-ray photoelectron spectroscopy (XPS) was used to measure the oxidation state and the composition near the surface. The compositions near the surface and in the bulk were found to vary with the identity of the doped element. The O2-structure lithium manganese oxides were prepared from Na-bronzes by ion exchange, but the crystallinity decreased after the ion exchange as a result of stacking faults.