Decoupling Solvation Lability from Catalytic Turnover: A Dual-Atom Strategy for Stabilizing the Li-O2 Battery Interface.

The performance of lithium-oxygen (Li-O2) batteries is fundamentally dictated by the competition between surface-mediated and solution-mediated discharge product growth. While dual single-atom catalysts (dual-SACs) offer a platform for tuning these pathways, the atomistic roles of site-specific adsorption, solvent coordination, and LiO2 interfacial stability remain elusive. Here, we have investigated a Zn-Co dual-SAC, in which Zn and Co metal atoms are anchored to an N-doped carbon substrate using density functional theory and explicit solvent ab initio molecular dynamics (AIMD) simulations. The presence of two distinct metal centers exhibits site-preferential adsorption behavior, favoring O2 adsorption over lithium adsorption and initiating the oxygen-first nucleation pathway. The two metal sites exhibit distinct interfacial behavior. The dual-site configuration induces a site-dependent adsorption hierarchy: the Zn site exhibits strong affinity for oxygen-containing species and can coordinate a DMSO molecule via the Zn-O(DMSO) interaction. In contrast, the Co site provides a more balanced Li-O intermediate binding and lower round-trip overpotential, while no persistent DMSO coordination to the Co site is observed in the modeled interface. This balance makes the Co site favorable for reversible surface-mediated Li2O2 formation. Explicit solvent slow growth AIMD reveals that Li2O2 formation proceeds through solvent-assisted Li+ coordination rearrangement, involving a transient trigonal-bipyramidal-like coordination state during coupling between solvated Li+ and surface-bound LiO2 with a free-energy barrier of 0.18 eV. In contrast, the higher slow-growth free energy barrier for LiO2 desorption (0.46 eV) makes LiO2 release into the electrolyte less favorable, supporting the preference for the surface-mediated pathway. These results show that LiO2 stability at the catalyst-electrolyte interface plays a key role in governing the competition between surface and solution pathways. Overall, this work highlights intermediate binding strength and LiO2 stability as key factors governing activity, reversibility, and reaction pathways, providing insights for the rational design of cathode materials for Li-O2 batteries.