Simultaneous Tailoring of Chemical Composition and Morphology Configuration in Metal Hexacyanoferrate for Ultrafast and Durable Sodium‐ion Storage

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium‐ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high‐entropy MHCF (HMHE‐HCF) assembled by nanocubes for the first time to realize the objective. The “cocktail effect” of high‐entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE‐HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE‐HCF cathode demonstrates superior rate performance up to an ultra‐high rate of 100 C (71.1% retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8% over 25,000 cycles at 100 C, outperforming most reported sodium‐ion cathodes. Further, the HMHE‐HCF//hard carbon full‐cell delivers capacities of 99.0 and 82.3 mAh g–1 at 0.1 C and 10 C, respectively, and retains 98.1% of the initial capacity after 1,600 cycles at 5C, demonstrating its potential application for sodium‐ion storage.