Synergistic effect of Au quantum dot-loaded CNT enhances ORR/OER catalytic performance in Li-O2 batteries

Abstract Li-O2 batteries are regarded as next-generation energy storage systems due to their exceptionally high theoretical energy density. However, their practical application remains constrained by the sluggish kinetic reactions occurring at the cathode. Herein, Au quantum dots supported on carbon nanotubes (Aux@CNT, x = 6, 10) are engineered as a dual-function electrocatalyst for the battery. This composite structure exhibits favourable thermodynamic stability and outstanding electronic conductivity. During discharge, LiO2 predominantly converts to Li2O2 via lithiation rather than disproportionation reactions, effectively suppressing the dissolution of intermediate products and associated side reactions. Gibbs free energy calculations indicate that the final discharge products may include Li4O2 and Li4O4. Furthermore, for the Li4O4 reaction pathway, incorporating solvent effects reveals that Aux@CNT exhibits overpotentials slightly lower than vacuum conditions in typical organic solvents. Molecular dynamics simulations confirm that neither the electrode structure nor solvent molecules undergo decomposition. Product morphology simulations reveal that an amorphous Li2O2 film is more readily formed on the electrode surface. This structure significantly reduces interfacial impedance while promoting efficient decomposition of the film-like Li2O2 during charging, effectively enhancing battery capacity and cycling stability. In summary, this study reveals the regulatory mechanism of Au quantum dots on the cathode reaction pathways and overpotential in Li-O2 batteries. These findings provide a crucial theoretical basis for the future rational design of high-performance metal nanocluster/carbon-based composite cathode materials and matched electrolyte systems.