Cation distribution in lithium nickel oxide crystals

Octahedral black-colored Li0.27Ni0.73O crystals were ground and studied by single-crystal X-ray diffraction. They crystallize in the rhombohedral R3 s pace group (no. 146) with unit cell dimensions (Angstrom) a = 6.020(2) and c = 14.726(5). The crystal structure consists of a close-packing oxygen arr angement with the cations occupying all of the octahedral sites, in such a way that two mixed layers containing Li and Ni in different proportions alt ernate along the c direction. The Li ordering is incompatible with the exis tence of pure Ni layers alternating with more or less doped Li ones as was assumed in the model admitted until now. The new model looks consistent wit h the magnetization measurements (300-2 K), which give evidence that Li0.27 Ni0.73O behaves as a mictomagnetic material, and can throw some light upon the Li diffusion pathway in rechargeable batteries.