Unveiling K-storage property of temperature-depended Fe-based metal organic terephthalate in KFSI-based electrolyte

Abstract

Constructing suitable anode materials with high specific capacity, cyclic performance as well as low-cost have been mainly restricted by the large K+radius for inorganic counterparts in potassium-ion batteries recently. Herein, the potassium storage performance and reaction mechanism of temperature-depended organic iron terephthalate (FeC8H4O4) were comparatively investigated in difluoro-sulfonimide potassium (KFSI)-based ester and ether electrolytes. The as-prepared FeC8H4O4–250 with rough surface area and larger specific surface area, showed the best electrochemical performance than that of FeC8H4O4–150 and FeC8H4O4. It was disclosed that the potassium storage mechanism of FeC8H4O4–250 is based on the reversible enolation reaction of carbonyl and the conversion of Fe2+ into Fe nanoparticles, consequently resulting in high specific capacity. In addition, the results suggest that FeC8H4O4–250 exhibits better cycling stability in KFSI/DME electrolyte than in KFSI/EC+DEC, which is mainly because the salts and solvents in KFSI/EC+DEC contribute to the formation of a stable and robust SEI that inhibits the decomposition of the electrolyte. Our work is of significant to explore high-performance electrode materials for next-generation energy storage systems.