Rational design of Prussian blue analogues as conversion anodes for lithium-ion batteries with high capacity and long cycle life

Abstract

Prussian blue analogues (PBAs) have garnered much attentions in energy fields due to their three-dimensional open framework and electrochemical tunability. Noticeably, PBAs are also deemed extremely attractive as anode materials for batteries by virtue of their abundant internal active sites. However, their unclear redox mechanisms at lower potential severely restricts PBAs anodes to realize stable cycling performances. In this work, low-cost KxMn[Fe(CN)6]y□1−y·nH2O with diverse H2O content and structure are harvested via controlling the crystallization rate. It is firstly discovered that the KxMn[Fe(CN)6]y anodes undergoes multi-electron conversion reactions involving the fracture and recombination of MnN bonds, while the stronger FeC bond is preserved. Then, it is confirmed that weaker MnN bond which need to be prepared at a faster crystallization rate is more conducive to the fast electrochemical kinetics of the reversible conversion paths. Accordingly, the K0.09Mn[Fe(CN)6]0.66□0.34·3.40 H2O with higher H2O content and weaker MnN bond achieve the best Li-storage performances, exhibiting a reversible capacity of 480 mAh g−1 at a high current density of 1 A g−1 and considerable cycling stability exceeding 1000 cycles. The results also suggest that interstitial H2O could be beneficial for the better cycling stability of the KxMn[Fe(CN)6]y anodes. This work can provide new insights for the rational design of novel conversion anodes with high reversible capacity and superior cycling stability.