Se‐Induced Synergistic Valence Regulation of NiFe LDH Enables Efficient Cl ⁻ Storage in High‐Rate Chloride Ion Batteries

Layered double hydroxides (LDHs) are promising chlorophilic hosts for chloride-ion batteries (CIBs), yet their practical application is hampered by poor intrinsic electronic conductivity and pronounced interlayer restacking. Here, we report a one-step hydrothermal selenium doping strategy to construct Se-doped NiFe LDH cathodes for CIBs. This approach preserves the hydrotalcite-like layered framework while introducing abundant oxygen vacancies and tuning the valence states of Ni and Fe, thereby establishing more continuous electron and ion transport pathways. The optimized Se0.2-NiFe-Cl LDH delivers a reversible capacity of 100 mAh g⁻¹ after 350 cycles at a current density of 300 mA g⁻¹ with nearly 100% Coulombic efficiency. It also exhibits an apparent Cl⁻ diffusion coefficient in the range of 10⁻¹³-10⁻ ¹¹ cm² s⁻¹, up to about one order of magnitude higher than that of pristine NiFe LDH. Ex situ characterizations combined with DFT calculations reveal that reversible Cl⁻ insertion/extraction is charge-compensated by synergistic dual-metals redox process within the LDH host layers, while Se doping optimizes the band-edge electronic structure and strengthens Cl⁻ adsorption at the LDH surface. This work identifies Se-doped NiFe LDH as an efficient model cathode for CIBs and offers a simple yet robust strategy for designing high-capacity, long-life Cl-storage materials.