Tailoring lattice confinement and conductivity of AlF co-doped Li2TiO3 ion sieves for highly selective lithium electrosorption

Built C@HTO-Al-F for electro-assisted Li + adsorption via Al 3+ /F − co-doping. • Carbon coating increases BET from 71.7 to 126.6 m 2  g −1 . • The C@HTO-Al-F electrode achieves a Li + adsorption capacity of 51.4 mg g −1 . • Li + binding affinity to −3.77 eV by regulating charge distribution and interlayer spacing. The selective extraction of lithium from salt lake brines is severely challenged by low Li + concentrations and the interference of coexisting Na + /K + ions. To address these limitations, an electro-assisted adsorption strategy was developed utilizing an Al F co-doped Li 2 TiO 3 ion-sieve encapsulated by a conductive carbon layer (C@HTO-Al-F). Structural characterization reveals that the synergistic incorporation of Al 3+ and F − induces a tailored lattice contraction-reducing the unit cell volume by 0.7 Å 3 -while the subsequent carbon coating dramatically expands the specific surface area from 71.7 to 126.6 m 2  g −1 . This multi-scale modulation simultaneously enhances the intrinsic ion-sieving effect, establishes a continuous electronic transmission network, and maximizes the density of accessible active sites. Consequently, under an applied voltage of 2.0 V, the C@HTO-Al-F electrode delivers a superior Li + adsorption capacity of 51.4 mg g −1 with exceptional selectivity, achieving separation factors of 47.8 against Na + and 26.9 against K + . Density functional theory (DFT) calculations further elucidate the atomic-scale mechanism, showing that co-doping optimizes the surface charge distribution and interlayer spacing, thereby strengthening the Li + binding affinity (adsorption energy of −3.77 eV). Furthermore, the conductive carbon shell mitigates interfacial polarization and ensures robust structural stability over long-term cycling. The work establishes a potent co-doping protocol for modulating ion-sieve structures, offering a promising avenue for high-efficiency lithium recovery from complex, multi-ionic aqueous resources.