Structure and electrochemistry of LiMO2 (M=Ti, Mn, Fe, Co, Ni) prepared by mechanochemical synthesis

LiMO2 (M=Ti, Mn and Fe) were prepared by ball milling mixtures of lithium transition metals and transition metal oxides. The resulting oxides were found to have the rocksalt structure with the transition metal and lithium ions randomly ordered in the cation sites, except for LiMnO2 which had some short range cation order. LiCoO2 and LiNiO2 samples prepared at high temperature were also observed to transform to the disordered rocksalt structure after subsequent milling. However, during milling these samples lost lithia and oxygen to form LixM1−xO (0.25×0.5). The electrochemical performance of the milled samples as cathodes in lithium batteries was poor, presumably due to the disorder of the cation lattice. However, mechanochemical synthesis may prove to be a useful synthesis step in the preparation of novel active cathode materials.