Two-Electron Reaction without Structural Phase Transition in Nanoporous CathodeMaterial

We investigated the charge/discharge properties, valence states, and structural properties of a nanoporous cathode material LixMn[Fe(CN)(6)](0.83) center dot 3.5H(2)O. The film-type electrode of LixMn[Fe(CN)(6)](0.83) center dot 3.5H(2)O exhibited a high charge capacity (= 128mAh g(-1)) and a good cyclability (87% of the initial value after 100 cycles) and is one of the promising candidates for Liion battery cathode. X-ray absorption spectra near the Fe and Mn K-edges revealed that the charge/discharge process is a twoelectron reaction; that is, Mn-II-NC-Fe-II, Mn-II-NC-Fe-III, and Mn-III-NC-Fe-III. We further found that the crystal structure remains cubic throughout the charge/discharge process. The lattice constant slightly increased during the [Fe-II(CN)(6)](4-)/[Fe-III(CN) (6)](3-) oxidization reaction while decreased during the MnII/MnIII oxidization reaction. The two-electron reaction without structural phase transition is responsible for the high charge capacity and the good cyclability.