The manganese dioxide electrode Part XIII: An FTIR study of H-insertion into EMD

Abstract

Two battery active γ-manganese dioxides, coded R2 and IBA 19, with ~100% microtwinning and ~40% de Wolff disorder were inserted with H by chemical methods in a nonaqueous environment. Compounds with compositions varying from the starting material to the fully H-inserted material were prepared and investigated by FTIR spectroscopy. Both series of compounds exhibited little change in their FTIR patterns until an H-insertion level expressed by s in MnOnHs of s = 0.63 (R2) and s = 0.55 (IBA 19) consistent with the idea that H and e− are mobile in the structure and present as independent thermodynamic components in an ideal solid solution. Beyond this level H location occurred as evidenced by a sharp change in integrated areas of regions of the spectra associated with O—H bond formation. Simultaneously a change in the position of one of the vibrations associated with that of the [MnO6] octahedra occurred. The assignment of bands in the spectra is discussed and evidence presented using a modified cusum procedure which supports the proposal that a demicrotwinning of the structure occurs as H begins to locate and the structure expands anisotropically.