Atomically dispersed ruthenium sites on ZnCo2O4 spinel as a highly active electrocatalyst for efficient lithium-oxygen battery

Aprotic lithium-oxygen batteries (LOBs) have aroused extensive attention due to their ultrahigh theoretical energy density. However, sluggish oxygen electrode reaction kinetics and large overpotential obstruct their largescale application. Herein, single-atom ruthenium decorated ZnCo2O4 (denoted as Ru-ZnCo2O4) with atomically dispersed Ru-Co atomic pair is prepared to boost oxygen redox reactions in LOBs. LOBs with the as-developed RuZnCo2O4 electrocatalyst achieve a low overpotential of 0.3 V, superior rate capability and excellent cyclability over 380 cycles. Based on physical characterizations, the introduction of atomically dispersed Ru leads to decreased electron density around Co3+. Theoretical calculations show the incorporation of Ru atoms not only adjusts the d-orbital energy level of cobalt but also breeds the rearrangement of d-electron in terms of increased eg filling. This causes the upshift of Co 3d band center towards O 2p band center in Ru-ZnCo2O4, which is conducive to enhancing the covalency of Co-O bands and boosting electron transfer between Co sites and oxygen adsorbates, eventually promoting the oxygen redox reaction kinetics.