State of manganese atoms during the mechanochemical synthesis of LiMn2O4

It has been established using X-ray photoelectron spectroscopy in combinati on with other physical methods that the initial stages of mechanochemical s ynthesis of LiMn2O4 in mixtures of MnO2 with LiOH and Li2CO3 are considerab ly different. In the first case the "smearing" of LiOH, having a flaky stru cture, on the surface of MnO2 and the formation of an amorphous layer take place. The reaction is accompanied by a redox process, with the participati on of OH groups and Mn4+ ions and with diffusion of lithium ions to the int erior 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 brit tle 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 prop osed. (C) 1999 Academic Press.