State of manganese atoms during the mechanochemical synthesis of LiMn2O4

It has been established using X-ray photoelectron spectroscopy in combination with other physical methods that the initial stages of mechanochemical synthesis of LiMn2O4 in mixtures of MnO2 with LiOH and Li2CO3 are considerably different. In the first case the "smearing" of LiOH, having a flaky structure, on the surface of MnO2 and the formation of an amorphous layer take place. The reaction is accompanied by a redox process, with the participation of OH groups and Mn4+ ions and with diffusion of lithium ions to the interior of the particles, and is completed by formation of Li-O-Mn bonds. No change in the valence state of manganese was detected, in Li2CO3, only brittle fracture was observed. Formation of defect spinel-like Li2O . yMnO(2) (2.5 less than or equal to y less than or equal to 4) on the surface is proposed. (C) 1999 Academic Press.