Solid NMR Study of Lithium Ions Accommodated in Various Transition Metal Oxides

Solid NMR was used to elucidate the lithium accommodation/extraction reaction in various transition metal oxides. The first study was the lithium ion exchange reaction of titanium antimonic acid (TiSbA). The effect of hydration on the selectivity of lithium ion in the solid phase was examined using 7Li NMR. The second study was the irreversible ion exchange behavior of HNbO3. The selectivity for the lithium ion and the irreversible behavior were examined using 1H and 7Li NMR. The third study was the isotope separation between 6Li and 7Li in various inorganic ion exchangers. The high isotope separation coefficient was ascribed to the degree of dehydration during the ion exchange reaction. The degree of dehydration was examined by 1H and 7Li NMR studies. The last study was determining the mechanism of the lithium accommodation/extraction reaction of λ-MnO2 in an aqueous solution. The different paths between the accommodation and extraction and the formation of MnO4− during the accommodation were determined by chemical analysis. The Knight shift in the 7Li MAS-NMR spectra of Li0.5MnO2 suggested the localization of the electron density on the lithium nuclei. An XPS study also suggested the presence of an electron density on the lithium nuclei. A pH-independent redox couple was assumed to account for the accommodation/extraction reaction of lithium ions, such as Li(I)/Li(0).