Intercalation of Water in P2, T2 and O2 Structure Az[CoxNi1/3-xMn2/3]O2

Abstract

The intercalation of water into P2-Na2/3[CoxNi1/3-xMn2/3]O2 (x = 0, 1/6, 1/3) and T2 or O2 structure Li2/3[CoxNi1/3-xMn2/3]O2 (x = 0, 1/6, 1/3) has been investigated by X-ray diffraction and thermogravimetric analysis (TGA). Water can be intercalated into P2-Na2/3[CoxNi1/3-xMn2/3]O2 (x = 1/6, 1/3) but not within P2-Na2/3[Ni1/3Mn2/3]O2. This difference may be related to the existence of superlattice ordering of Ni atoms, but not Co atoms, within the transition metal layer which apparently induces a very strong interlayer interaction and inhibits the uptake of water. Two water-containing phases of P2-Na2/3(H2O)y[Co1/3Mn2/3]O2 were found and one, with y ≈ 2/3, could be prepared in pure form. By Rietveld refinement of the X-ray diffraction pattern of P2-Na2/3(H2O)2/3[Co1/3Mn2/3]O2, it can be concluded that the compound still exists in the ideal P2 structure (P63/mmc) with the oxygen atoms of the water molecule located on the 2c site. Water cannot be intercalated into the corresponding lithiated phases, Li2/3[CoxNi1/3-xMn2/3]O2 for any value of x that we tested (x = 0, 1/6, 1/3).