Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

The chemical composition of electrode surfaces has been determined by X-ray photoelectron spectroscopy and compared with the results of X-ray diffraction studies to expose differences between bulk and surface structure in electrodes cycled or stored at room temperature. The surface of electrodes discharged to contains only although the bulk phase also contains a component of phase. On the other hand, both and are found on the surface of an electrode delithiated to phase-pure Electrodes cycled or stored exhibit a -rich surface, contrary to the bulk structure. It is concluded that or some defect spinel-type structure with averaged Mn oxidation state below 3.5 is formed on the electrode surface.