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 (Mn28O4O)(32+) for lambda-MnO2 and (X5Mn12O40)(n-) for XMn2O4{n = 31 (X = H) and n = 33 (X = Li)}. The discrete-variational (DV)-Xalpha 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.