Dual Vacancy‐Driven “Lattice Softening” NiFeAl x LDHs for High‐Rate and Durable Chloride Ion Storage

Abstract Defect engineering becomes an essential strategy for enhancing electrochemical performance, yet its application in anion‐based systems such as chloride‐ion batteries (CIBs) remains largely unexplored. Herein, a rational defect‐engineering strategy is developed to overcome these bottlenecks by constructing dual‐vacancy NiFeAl x layered double hydroxides (LDHs) featuring coexisting cationic and oxygen vacancies, achieved via a room‐temperature alkaline etching process that selectively leaches Al 3+ while retaining layered integrity. The optimized NiFeAl 0.04 ‐24h‐Cl LDH exhibits unprecedented “lattice softening” behavior, enabling elastic deformation and dynamic structural reconstruction to accommodate volumetric fluctuations during Cl‐intercalation/de‐intercalation. Benefiting from this defect‐induced structural flexibility, the electrode delivers a high reversible capacity of 101.4 mAh g −1 after 1000 cycles at 1000 mA g −1 , along with the Coulombic efficiency of 99.91%. Multiscale mechanistic analyses demonstrate that the coupled vacancies regulate local electronic distribution and coordination environments while simultaneously imparting pronounced lattice softening and structural elasticity to the NiFeAl 0.04 ‐24h‐Cl LDH, thereby facilitating enhanced Cl − ion accommodation. Furthermore, the vacancies construct interconnected 3D ion highways, which dramatically accelerate Cl − diffusion, enhance interfacial adsorption kinetics, and minimize charge‐transfer resistance. Such lattice‐adaptive regulation resolves the long‐standing trade‐off between anion‐storage capacity and structural stability in LDH‐based systems, offering a promising strategy for designing efficient anion‐hosting electrodes for advanced CIB systems.