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

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.