Strong localization of oxidized Co state in cobalt-hexacyanoferrate.

Secondary batteries are important energy storage devices for a mobile equipment, an electric car, and a large-scale energy storage. Nevertheless, variation of the local electronic state of the battery materials in the charge (or oxidization) process are still unclear. Here, we investigated the local electronic state of cobalt-hexacyanoferrate (Na Co[Fe(CN)]), by means of resonant inelastic X-ray scattering (RIXS) with high energy resolution (~100 meV).

In situ observation of macroscopic phase separation in cobalt hexacyanoferrate film.

Lithium-ion secondary batteries (LIBs) store electric energy via Li deintercalation from cathode materials. The Li deintercalation frequently drives a first-order phase transition of the cathode material as a result of the Li-ordering or Li-concentration effect and causes a phase separation (PS) into the Li-rich and Li-poor phases. Here, we performed an in situ microscopic investigation of the PS dynamics in thin films of cobalt hexacyanoferrate, LiCo[Fe(CN)], against Li deintercalation.

Na(+) diffusion kinetics in nanoporous metal-hexacyanoferrates.

Metal-hexacyanoferrates (metal-HCFs) are promising candidates for cathode materials of sodium-ion secondary batteries (SIBs). Here, we systematically investigated Na(+) diffusion constants (D) and the activation energies (Ea) of metal-HCFs against the framework size (= a/2). We found that the magnitude of D (Ea) systematically increases (decreases) with increases in a, indicating that steric hindrance plays a dominant role in Na(+) diffusion.

A sodium manganese ferrocyanide thin film for Na-ion batteries.

A thin film of sodium manganese ferrocyanide, Na1.32Mn[Fe(CN)6]0.83·3.