A Na-rich manganese hexacyanoferrate hollow nano-cube with low crystal water and few defects for efficient Zn ion storage in aqueous batteries

Abstract

Prussian blue analogs (PBAs) have competitive advantages as cathode materials for aqueous rechargeable batteries, including stable framework structures, regulated redox sites, and straightforward synthesis methods. However, in most cases, there are vacancies and coordinated/interstitial water molecules in the framework of PBAs. This not only reduces the active sites but also makes their structure susceptible to collapse during the charge-discharge process, leading to low specific capacity and poor cycling stability. In this work, a favorable cathode material of Na1.39Mn[Fe(CN)6]·1.2H2O (denoted as RNMHCF-H) equipped with abundant Na content, low crystal water and few defects was successfully prepared by a simple co-precipitable method. The RNMHCF-H exhibits a greatly improved capacity of 151.4 mA h g−1 at 100 mA g−1, good rate performance and impressive stability performance in aqueous Zn ion batteries (AZIBs). Furthermore, multifaceted characterization techniques were used to reveal the process and mechanism of Zn2+ storage in RNMHCF-H, and it was found that both manganese and iron participate in the electrochemical redox reaction during the charging/discharging process.