Low voltage charge/discharge behavior of manganese hexacyanoferrate

Abstract

Recently, Prussian blue analogues (PBAs) have been reported to exhibit a low voltage charge/discharge behavior with high capacity (300–545 mAh/g) in lithium-ion secondary batteries (LIBs). To clarify the mechanism of low voltage behavior, we performed ex situ synchrotron radiation X-ray diffraction (XRD) and ex situ X-ray absorption spectroscopy (XAS) of a film of Na1.34Mn[Fe(CN)6]0.84·3.4H2O without air exposure. After the 1st discharge process, the XRD patterns and X-ray absorption spectra around the Fe and Mn K edges reveal formation of Fe and Mn metals. After the charge process, the XRD pattern reveals formation of Fe2O3 . Based on these observations, we ascribed the low voltage behavior mainly to the conversion reaction of Fe2O3: 6e− + Fe2O3 + 6Li+ ⇀↽ 2Fe +3Li2O.