Selective Lithium Recovery via Photothermal Evaporation and Hydration-Controlled Adsorption

Solar-driven evaporation enables scalable, energy-efficient lithium recovery from saline water, but it is challenged by slow kinetics, low selectivity, and ionic interference. Here, we present a bilayer Mo-Layered Double Hydroxide@Sponge composite that integrates photothermal evaporation with hydration-controlled adsorption for selective lithium extraction. A dynamic two-stage behavior emerges, where photothermal energy initially enhances both ion transport and interfacial water evaporation, followed by hydration-induced suppression of further adsorption. This transition reflects a shift in the dominant transport regime, where thermal stimulation initially accelerates mobility, but prolonged exposure alters the hydration structure. Elevated temperatures promote the formation of more compact hydration shells around Li⁺, which in turn hinder diffusion by increasing viscosity and enhancing ion-solvent interactions, highlighting a hydration-controlled adsorption mechanism. Meanwhile, high salt concentrations contribute to reduced interfacial cohesion, which further facilitates evaporation and reinforces concentration-driven Li⁺ transport, complementing the hydration-governed adsorption dynamics. The composite exhibits strong Li⁺ selectivity, structural robustness, and stable solar performance, providing a mechanistic basis for scalable lithium recovery.