In situ IR spectroscopy during oxidation process of cobalt Prussian blue analogues
Hideharu Niwa, Toshiaki Moriya, Takayuki Shibata, Yuya Fukuzumi, Yutaka Moritomo
Abstract
Abstract Cobalt Prussian blue analogues (Co-PBA; Na x Co[Fe(CN) 6 ] y ), consisting of cyano-bridged transition metal network, –Fe–CN–Co–NC–Fe–, are promising cathode materials for Na-ion secondary batteries. In the oxidation process, oxidization of Fe and/or Co are compensated by Na + deintercalation. Here, we investigated the oxidization process of three Co-PBAs by means of in situ infrared absorption (IR) spectroscopy. With use of an empirical rule of the frequencies of the CN − stretching mode in ferrocyanide ([Fe II (CN) 6 ] 4− ) and ferricyanide ([Fe III (CN) 6 ] 3− ), the oxidation processes of Co-PBAs were determined against the Fe concentration ( y ) and temperature ( T ). We will discuss the interrelation between the oxidation processes and Fe concentration ( y ).