Asymmetric Catalytic Site Driving LiOH Chemistry for Li–O2 Batteries Based on Cationic Vacancy-Derived Single-Atom Spinel

The high conductivity and low decomposition potential of LiOH as the discharge product in Li–O2 batteries have garnered significant attention. However, challenges remain in developing LiOH-based Li–O2 batteries and promoting efficient generation/decomposition of LiOH. Here, we propose a strategy to build a binder-free cathode for Li–O2 batteries by embedding atomically dispersed Ru onto the surface of MnCo2O4 (RuSA-MnCo2O4) through defect engineering and adsorption–deposition methods, harnessing the synergistic benefits of spinel and a single atom in terms of catalytic activity and physical structure. The embedding of Ru leads to slight lattice distortion of MnCo2O4 and electron enrichment near Co, breaking the long-range ordered and symmetrical structure of spinel and transforming the symmetrical Mn/Co low-activity centers into asymmetrical Ru–O–Co high-activity centers. Compared to that of MnCo2O4, the d-band center of RuSA-MnCo2O4 is positioned further away from the Fermi level, resulting in an increased occupancy of antibonding orbitals. This leads to more moderate adsorption energies for LiO2* and LiOH*, as well as a reduction in the reaction barrier for LiOH formation, thereby optimizing the kinetics of the redox reactions. Thanks to the catalytic active center regulated by RuSA, the electrochemical performances were greatly improved, which also provides a clever approach for the development of catalysts for LiOH-based Li–O2 batteries.