Two-Electron Reaction without Structural Phase Transition in Nanoporous Cathode Material.

We investigated the charge/discharge properties, valence states, and structural properties of a nanoporous cathode material LixMn[Fe(CN)₆]_0.83 . 3.5H₂O. The film-type electrode of LixMn[Fe(CN)₆]_0.83 . 3.5H₂O 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- /[FeIII(CN)₆]^3- oxidization reaction while decreased during the Mn^II/Mn^III oxidization reaction. The two-electron reaction without structural phase transition is responsible for the high charge capacity and the good cyclability. [ABSTRACT FROM AUTHOR]