Selective Molecular Ion-Gating at Electrochemical Interfaces for Accelerated Lithium Extraction

The selective recovery of lithium from complex brines in battery deionization (BDI) systems is constrained by the competitive adsorption and intercalation of chemically similar alkali ions at the solid-liquid interface. Although Faradaic lithium insertion materials exhibit high theoretical capacities, they often fail to provide the necessary selectivity to suppress the substantial competitive flux of coexisting sodium ions. Here, we report a molecular ion-gating strategy that decouples selectivity from capacity via interfacial engineering. By encapsulating the LiMn₂O₄ (LMO) core within an Aza-15-Crown-5 (A15C5)-functionalized graphene oxide (CGO) shell, we construct a core-shell LMO@CGO architecture that exhibits highly selective Li⁺ transport. Experimental results and kinetic modeling support that the [C₁₀O₅] macrocyclic rings function as selective ion gates, preferentially enriching Li⁺ at the interfacial region through coordination. This interfacial enrichment accelerates Li⁺ intercalation into the LMO lattice while suppressing competing cation transfer. When integrated into a BDI system, the LMO@CGO architecture achieves a highly competitive Li⁺/Na⁺ separation factor of 302.23 and a capacity of 19.8 mg·g^-1 in raw Lagoco salt lake brine. Our findings demonstrate that bridging molecular-level gating with electrochemical Faradaic processes provides a promising interfacial design strategy for selective electrochemical lithium recovery from complex aqueous conditions.