Doping engineering of lithium-aluminum layered double hydroxides for high-efficiency lithium extraction from salt lake brines

Lithium-aluminum layered double hydroxides (LiAl-LDH) have been be successfully applied in commercial-scale for lithium extraction from salt lake brine, however, further advancement of their applications is hampered by suboptimal Li⁺ adsorption performance and ambiguous extraction process. Herein, a doping engineering strategy was developed to fabricate novel Zn²⁺-doped LiAl-LDH (LiZnAl-LDH) with remarkable higher Li⁺ adsorption capacity (13.4 mg/g) and selectivity (separation factors of 213, 834, 171 for Li⁺/K⁺, Li⁺/Na⁺, Li⁺/Mg²⁺, respectively), as well as lossless reusability in Luobupo brine compared to the pristine LiAl-LDH. Further, combining experiments and simulation calculations, it was revealed that the specific surface area, hydrophilic, and surface attraction for Li⁺ of LiZnAl-LDH were significantly improved, reducing the adsorption energy (E_ad) and Gibbs free energy (ΔG), thus facilitating the transfer of Li⁺ from brine into interface followed by insertion into voids. Importantly, the intrinsic oxygen vacancies derived from Zn-doping depressed the diffusion energy barrier of Li⁺, which accelerated the diffusion process of Li⁺ in the internal bulk of LiZnAl-LDH. This work provides a general strategy to overcome the existing limitations of Li⁺ recovery and deepens the understanding of Li⁺ extraction on LiAl-LDH.