Lithium Capture in Gibbsite-Derived Layered Double Hydroxides: Molecular Insights into Intercalation and Lattice Incorporation Mechanisms

Phase transition from gibbsite to lithium–aluminum layered double hydroxides (Li–Al LDHs) is important for the use of Li–Al LDHs in capturing Li + from brines. Here, we hypothesize that Li + incorporation into the gibbsite lattice to form Li–Al LDHs proceeds through a multistep mechanism involving Li + partitioning from bulk solution into hydrated gibbsite interlayers, followed by incorporation into vacant octahedral lattice sites. Our molecular dynamics simulation results indicate that in strongly confined bihydrated interlayers (2W), Li + experiences an unfavorable free-energy entering the pore environment from bulk solution, whereas expansion to trihydrated interlayers (3W) substantially reduces the confinement effect and facilitates lithium entry into the pore. Once inside the interlayer, incorporation into the vacant octahedral sites of gibbsite becomes thermodynamically favorable, producing a deep free-energy minimum. The free-energy profile also confirms that Li + encounters an energy barrier when transitioning from an inner-sphere adsorption complex to the lattice site, although this barrier can be readily overcome at elevated temperatures. Simulations further demonstrate that Li + uniquely completes the full pathway toward lattice incorporation, while competing ions such as Na + and Mg 2+ remain in hydrated or adsorbed states. These findings demonstrate that lithium capture in Li–Al LDHs is governed not by simple adsorption, but by coupled nanoconfinement, hydration, and lattice incorporation processes.