Portal de Periódicos da CAPES

Probing the Local Structure and the Role of Protons in Lithium Sorption Processes of a New Lithium-Rich Manganese Oxide

2006; American Chemical Society; Volume: 18; Issue: 7 Linguagem: Inglês

10.1021/cm052214r

1520-5002

M.J. Ariza, Deborah J. Jones, Jacques Rozière, Ramesh Chitrakar, Kenta Ooi,

Multiferroics and related materials

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