The structure of a V Li_xMnO₂ cathode and its change upon electrochemical lithiation

The crystal structure of Li_1.25MnO₂ obtained by heat-treatment of a γ-MnO₂ and LiNO₃ mixture (Li/Mn ratio 1:3, 370°C, 20 h), which is used as a 3 V cathode in rechargeable lithium batteries, is proposed as an ordered alternation of [1 × 2] and [1 × 1] channels. The simulation of this structure by the Rietveld method is in good agreement with the powder X-ray diffraction pattern of this material. It has been shown that the major difference between the structures of γ-MnO₂ and the thermal lithiated product is the ordering in the MnO₄-octahedra arrangement. This leads to the high reversibility and cyclability of this cathode material in rechargeable Li batteries.