Lithium intercalation properties in manganese-iron Prussian blue analogues

We investigated the electronic states and structural properties of Li_xMn[Fe(CN)₆]_0.83·3.5H₂O, and Li_xMn[Fe(CN)₆]_0.87·2.6H₂O, which have different amount of [Fe(CN)₆] vacancies. X-ray absorption spectra near the Fe and Mn K-edges revealed that the Li intercalation/deintercalation process is two-electron reaction, i.e. Mn^II—NC—Fe^II, Mn^II—NC—Fe^III, and Mn^III—NC—Fe^III. The crystal structure of Li_xMn[Fe(CN)₆]_0.83·3.5H₂O remains cubic and single phase throughout the Li intercalation/deintercalation process. The crystal structure of Li_xMn[Fe(CN)₆]_0.87·2.6H₂O is also cubic, while phase separation of Li⁺-rich phase and Li⁺-poor phase was observed during the Mn^II/Mn^III reduction/oxidation process.