文摘
Lithium exchange mechanisms, local structure, and its possible evolutions on lithium extraction andreinsertion are studied in Li1.6Mn1.6O4, a new lithium-rich manganese oxide showing improved lithiumsorption. The parent Li1.6Mn1.6O4 and its lithium-extracted and lithium-reinserted forms are characterizedby X-ray absorption (EXAFS and XANES) and incoherent inelastic neutron scattering (IINS)spectroscopies. Lattice hydroxyl groups are detected in the lithium-extracted sample; the chemicalreinsertion of lithium removes most of the hydroxyl groups, but some protons remain in the structuremainly as structural water. X-ray absorption spectroscopy at the manganese K-edge indicates a localspinel structure of Li1.6Mn1.6O4 with manganese in oxidation state 4+. The structural arrangement andMn oxidation state remain unchanged when lithium is extracted and reinserted. The lithium sorptionoccurs by Li+/H+ ion exchange process, as for Li1.33Mn1.67O4, the previously considered end member ofthe Li1+xMn2-xO4 spinel lithium-rich series. Since the cation-to-anion ratio of Li1.6Mn1.6O4 is not thatwhich is typical for a spinel, the new lithium-rich manganese oxide has a spinel structure with the extraLi+ probably in interstitial sites, although lithium cannot be located unequivocally from these results.