Novel synthesis process and structure refinements of Li(sub 4)Mn(sub 5)O(sub 12) for rechargeable lithium batteries

摘要

Well crystallized Li4Mn5O12 was prepared from LiOAc-Mn(NO3)2 under flowing oxygen. Rietveld refinement with XRD and neutron powder diffraction indicated that Li4Mn5O12 has cubic spinel structure in which the Li ions occupy both the tetrahedral sites 8a and part of the octahedral sites 16d but not the 16c sites, while all the Mn ions occupy the 16d sites of the space group Fd(bar 3)m. The lattice parameter was found to be sensitive to synthesis temperature owing to variation in Mn valence. Sample prepared at 500 C showed better electrode performance: a rechargeable capacity of 135 mAh/g for the cell Li/Li4Mn5O12 at cell voltages 2.5-3.6 V. It is found that Mn oxidation state in Li4Mn5O12 has a strong effect on electrode performance of Li/Li4Mn5O12 cell.