Determination of the Chemical Bonding of Ionic Lithium and Proton Exchange in Spinel-Type Manganese Oxides

A study of the electronic structure and chemical bonding of the Li ions and protons inserted in manganese oxides was performed by a first-principles molecular-orbital method using model clusters (Mn28O40)32+ for λ-MnO2 and (X5Mn12O40)n- for XMn2O4{n = 31 (X = H) and n = 33 (X = Li)}. The discrete-variational (DV)-Xα method was employed and Mulliken’s population analyses were carried out. Strong covalent interactions operate between Mn and O ions in the manganese oxides. Li and hydrogen in manganese oxides are highly ionized. These results are likely to be a very important factor in determining the excellent selectivity of spinel-type manganese oxides for Li+ ions and the exchange between Li+ and protons.