Regulating electrochemistry kinetics and discharge product selectivity with near-free cobalt single-atom catalyst in Li-O2 batteries

Recognization of the dynamic evolution of the catalytic active site and battery reaction intermediates under working conditions is essential for optimal design of advanced electrocatalysts for lithium-oxygen batteries, yet remaining formidable challenges because of size, carrier, and surface interface effect on traditional supported catalysts. Herein, based on the designed single-Co-atom catalyst model with uniform and isolated active centers, the structural dynamic evolution of near-free active centers and the complicated reaction pathways of lithium-oxygen electrochemistry is firstly in-depth identified at the atomic level by virtue of structural and ingredient measurements at multiscale levels. We discover that the near-free Co site (Co1-N3) tends to be dynamically released from the nitrogen-carbon substrate, and then forms a freer O*-Co1-N2 site, facilitating the surface adsorption and activation of the key *O intermediate for oxygen reduction reaction during discharge. More interestingly, near-free Co exists a better lattice match with the (100) crystal plane of Li2O2, forming an easily decomposed single-oriented sheet-like Li2O2 with higher electron transport capacity and weaker *LiO2 combination, thus improving the kinetics of oxygen evolution reaction during recharge. The integration of multiple test techniques on single-atom catalyst model in this study may pave the way for revealing important dynamic evolution steps and reaction mechanisms at three-phase boundaries in metal-air batteries.