THE MANGANESE-DIOXIDE ELECTRODE .13. AN FTIR STUDY OF H-INSERTION INTO EMD

Two battery active gamma-manganese dioxides, coded R2 and IBA 19, with similar to 100% microtwinning and similar to 40% de Wolff disorder we re inserted with H by chemical methods in a nonaqueous environment. Co mpounds with compositions varying from the starting material to the fu lly H-inserted material were prepared and investigated by FTIR spectro scopy. 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 o ccurred as evidenced by a sharp change in integrated areas of regions of the spectra associated with O-H bond formation. Simultaneously a ch ange 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 w hich supports the proposal that a demicrotwinning of the structure occ urs as H begins to locate and the structure expands anisotropically.