Novel Cerium Hexacyanoferrate(II) as Cathode Material for Sodium-Ion Batteries

Owing to the demand for large-scale energy storage applications and the Li resource shortage, over the past few decades, various novel materials have been investigated as Li + -ion hosts. However, very few candidates have been found as Na + /K + -ion host due to their much larger ionic radius than that of Li + -ions. Herein, a cerium hexacyanoferrate (CeHCF) has been successfully synthesized by a facile coprecipitation method for Li + /Na + /K + -ion storage. As a cathode material, CeHCF delivers a specific capacity of ∼60 mAh/g at 0.25 C and ∼80% capacity retention at 8.3 C in lithium-ion batteries (LIBs), and ∼55 mAh/g at 0.25 C with ∼55% capacity retention at 8.3 C in sodium-ion batteries (SIBs), respectively. Owing to its open 3D framework and highly stable crystal structure, CeHCF presents as a “zero-strain” insertion cathode material for a reversible insertion/extraction of Li + /Na + /K + -ion. Through multiple characterization techniques, including in situ XRD and ex situ Raman, alkali ion intercalation of CeHCF has been investigated. Our studies not only deliver a novel candidate as a universal host for alkali ion but also deduce the alkali ion storage mechanism in the framework and the structure evolution in the electrochemical process.