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. We demonstrate for the first time, the synthesis of a CoFe LDH with Cl^– in the interlayer space (denoted as CoFe-Cl LDH) and its potential application as a cathode material for high-performance CIBs. The Cl^– ions storage mechanism was based on the unique topochemical transformation of CoFe-Cl LDH structure. First-principles calculations reveal that CoFe-Cl LDH is an excellent Cl⁻ ion conductor, with extremely low energy barriers ~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.
    In addition, theNi₂V_0.9Al_0.1-Cl trimetallic LDH with Cl⁻ in the interlayer was synthesized and have also been demonstrated to be excellent cathode materials for CIBs. The Ni₂V_0.9Al_0.1-Cl LDH is capable of delivering a high initial capacity of 312.2 mAh g⁻¹ at 200 mA g⁻¹ and an ultralong life over 1000 cycles (with a capacity higher than 113.8 mAh g⁻¹). Such a long cycling life exceeds that of any reported CIBs. The remarkable Cl⁻-storage performance of the Ni₂V_0.9Al_0.1-Cl LDH is ascribed to the synergetic contributions from V^m+(high redox activity), Ni²⁺ (favourable electronic structure) and inactive Al³⁺ (enhances the structural stability), which is revealed by a comprehensive study that utilizes synchrotron Xray absorption near-edge structure experiments, kinetic investigations and theoretical calculations.