Phase separation of a hexacyanoferrate-bridged coordination framework under electrochemical na-ion insertion

Satoshi Kajiyama; Yoshifumi Mizuno; Masashi Okubo; Ryosuke Kurono; Shin-ichi Nishimura; Atsuo Yamada

doi:10.1021/ic403088r

Phase separation of a hexacyanoferrate-bridged coordination framework under electrochemical na-ion insertion

Inorg Chem. 2014 Mar 17;53(6):3141-7. doi: 10.1021/ic403088r. Epub 2014 Mar 3.

Authors

Satoshi Kajiyama¹, Yoshifumi Mizuno, Masashi Okubo, Ryosuke Kurono, Shin-ichi Nishimura, Atsuo Yamada

Affiliation

¹ National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.

PMID: 24588620
DOI: 10.1021/ic403088r

Abstract

Phase separation and transformation induced by electrochemical ion insertion are key processes in achieving efficient energy storage. Exploration of novel insertion electrode materials/reactions is particularly important to unravel the atomic/molecular-level mechanism and improve the electrochemical properties. Here, we report the unconventional phase separation of a cyanide-bridged coordination polymer, Eu[Fe(CN)6]·4H2O, under electrochemical Na-ion insertion. Detailed structural analyses performed during the electrochemical reaction revealed that, in contrast to conventional electrochemical phase separation induced by the elastic interaction between nearest neighbors, the phase separation of NaxEu[Fe(CN)6]·4H2O is due to a long-range interaction, namely, cooperative rotation ordering of hexacyanoferrates. Kolmogorov-Johnson-Mehl-Avrami analysis showed that the activation energy for the phase boundary migration in NaxEu[Fe(CN)6]·4H2O is lower than that in other conventional electrode materials such as Li(1-x)FePO4.