Density functional theory study of selectivity of crown ethers to Li+ in spent lithium-ion batteries leaching solutions

Abstract

It is a challenge to recover lithium from the leaching solution of spent lithium-ion batteries, and crown ethers are potential extractants due to their selectivity to alkali metal ions. The theoretical calculations for the selectivity of crown ethers with different structures to Li ions in aqueous solutions were carried out based on the density functional theory. The calculated results of geometries, binding energies, and thermodynamic parameters show that 15C5 has the strongest selectivity to Li ions in the three crown ethers of 12C4, 15C5, and 18C6. B15C5 has a smaller binding energy but more negative free energy than 15C5 when combined with Li + , leading to that the lithium ions in aqueous solutions will combine with B15C5 rather than 15C5. The exchange reactions between B15C5 and hydrated Li + , Co 2+ , and Ni 2+ were analyzed and the results show that B15C5 is more likely to capture Li + from the hydrated ions in an aqueous solution containing Li + , Co 2+ , and Ni 2+. This study indicates that it is feasible to extract Li ions selectively using B15C5 as an extractant from the leaching solution of spent lithium-ion batteries.

Investigation of ion-electrode interactions of linear polyimides and alkali metal ions for next generation alternative-ion batteries

“…To better probe the interactions responsible for the differing properties among polymer–ion combinations, crown ethers were added to the electrolyte solutions (12-crown-4 ether for Li + batteries, 18-crown-6 ether for K + batteries) to serve as strongly-coordinating and highly persistent chelating agents around the charge-compensating ions. 67–71 In essence, crown ethers serve as a solvent shell that cannot be shed by the ion.…”

Thermodynamics of Li+–Crown Ether Interactions in Aqueous Solvent

“…Because the cavity size of crown ether 12-crown-4 corresponds to the size of the Li + , 12-crown-4 has garnered interest as a potential host for Li + . This work was supported by an initial set of density functional theory calculations that lend significant credence to the idea, as do observations of improved alkali-metal ion separations when including CEs in nonaqueous environments. − However, some other studies reveal that such size-matching predictions are not always realized. , As the prevailing theory behind this work is done in a vacuum, and experiments are typically done in a solvent, there is potential for discrepancies that can be resolved by appealing to molecular simulations.…”

“…Because of the variance in sizes between different cations and different crown ether cavities, specific ions are hypothesized to have a greater affinity to certain crown ethers . Cavity sizes of 12-crown-4, 15-crown-5, and 18-crown-6 are 3.228, 4.074, and 5.299 Å, where the lengths correspond to the minimum distance between two oxygen atoms located at the para-position . We illustrate hypothetical binding of a Li + ion to these three crown ethers in Figure .…”

“…23 Cavity sizes of 12-crown-4, 15crown-5, and 18-crown-6 are 3.228, 4.074, and 5.299 Å, where the lengths correspond to the minimum distance between two oxygen atoms located at the para-position. 24 We illustrate hypothetical binding of a Li + ion to these three crown ethers in Figure 1.…”

Thermodynamics of Li+–Crown Ether Interactions in Aqueous Solvent

“…atoms located at para-position. 20 We illustrate hypothetical binding of a Li + ion to these three crown ethers in Figure 1.…”