Gill‐Inspired Hierarchical Li/Al Layer Double Hydroxide Membrane for High‐Capacity Lithium Adsorption from Salt Lakes

Abstract Li‐ion extraction from salt lakes is crucial to flourishing Li‐ion battery industry, but is limited by low efficiency of adsorbents. Mushrooms are a family of natural sorbents for metal ions, benefiting from hierarchical gills with high surface areas. With this inspiration, a free‐standing Li/Al‐layer double hydroxides (Li/Al‐LDHs) adsorption membrane with hierarchical Li‐ion channels is developed, for fast and high‐capacity LiCl capture. Layer‐by‐layer Li/Al‐LDHs grow and stack along the vertical direction of nanofibers of porous Al foams, to build ion diffusion highways. Thereafter, sub‐1 nm Li‐ion selective channels formed orthotopically with Li‐ion deintercalation of Li/Al‐LDHs, and acted as Li‐adsorption sites. Superior to the reported Al‐based sorbents, the Li/Al‐LDH membrane (LDHM) exhibits outstanding Li‐ion adsorption performance, surpassing 35 mg g ⁻¹ of M _Li /M _LDH even in LiCl aqueous solutions with a Li ⁺ concentration of 320 ppm, by virtue of effective exposure of the active adsorption sites in hierarchical pathways. Notably, applied for Qarhan Salt Lake, the Li‐ion adsorption capacity also reaches up to 8.96 mg g ⁻¹ of M _Li /M _LDH . This work proposes a general strategy for high‐capacity Li‐ion sorbents, and highlights the advantages of hierarchical adsorption membranes over conventional granule sorbents in metal‐ion extraction applications.