Engineering Li-Al LDH with anions and metals modulations for durable lithium recovery

초록

The rise of lithium-ion battery use necessitates the development of efficient, eco-friendly, and cost-effective lithium (Li+) recovery systems. In this study, lithium–aluminum layered double hydroxides (LDH) were modified by introducing different interlayer anions (CO32−, Cl−, SO42−, NO3−, CH3COO−, and PO43−) and first row divalent metal cations (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) and their performance was systematically evaluated. The results revealed that the LDH material doped with Fe2+ and intercalated with PO43− (Fe-LDH-P) showed the optimal configuration for Li+ recovery. These modifications synergistically enlarge the interlayer spacing through PO43− intercalation and enhance structural stability by Fe2+ doping, thereby preventing structural collapse during repeated lithium adsorption–desorption cycles. Adsorption experiments in Li+-spiked seawater showed that Fe-LDH-P achieved a maximum adsorption capacity (qmax) of 11.23 mg/g, significantly exceeding that of LDH (6.95 mg/g). Nonlinear isotherm analysis indicated the Langmuir model best describes the adsorption behavior (R2 = 0.993), confirming monolayer adsorption and strong selectivity over competing ions. Kinetic analysis revealed pseudo-second-order (PSO) behavior (R2 = 0.94, K2 = 0.143 g/ mg min, RMSE = 0.267, χ2 = 6.76), indicating a chemisorption-controlled Li+ adsorption mechanism. Density functional theory (DFT) analysis revealed that phosphate intercalation significantly expands the LDH interlayer spacing from 7.59 to 8.86 Å, enhancing Li+ accessibility and structural stability, whereas iron doping induces a slight contraction while strengthening Li+ binding and suppressing deintercalation and gibbsite formation. This synergistic effect suppresses Li+ deintercalation and gibbsite formation, thereby enabling durable and efficient Li+ recovery. © 2026 Elsevier B.V.

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