CoFe–Cl Layered Double Hydroxide: A New Cathode Material for High‐Performance Chloride Ion Batteries

Abstract Chloride ion batteries (CIBs) are regarded as promising energy storage systems due to their large theoretical volumetric energy density, high abundance, and low cost of chloride resources. Herein, the synthesis of CoFe layered double hydroxide in the chloride form (CoFe–Cl LDH), for use as a new cathode material for CIBs, is demonstrated for the first time. The CoFe–Cl LDH exhibits a maximum capacity of 239.3 mAh g −1 and a high reversible capacity of ≈160 mAh g −1 over 100 cycles. The superb Cl − ion storage of CoFe–Cl LDH is attributed to its unique topochemical transformation property during the charge/discharge process: a reversible intercalation/deintercalation of Cl − ions in cathode with slight expansion/contraction of basal spacing, accompanied by chemical state changes in Co 2+ /Co 3+ and Fe 2+ /Fe 3+ couples. First‐principles calculations reveal that CoFe–Cl LDH is an excellent Cl − ion conductor, with extremely low energy barriers (0.12−0.25 eV) for Cl − diffusion. This work opens a new avenue for LDH materials as promising cathodes for anion‐type rechargeable batteries, which are regarded as formidable competitors to traditional metal ion‐shuttling batteries.