Atomically Asymmetrical Ruthenium–Oxygen–Cobalt Sites Accelerate Oxygen Redox and Suppress Side Reactions for Stable Lithium–Oxygen Batteries

Development of aprotic lithium–oxygen (Li–O 2 ) batteries suffers from slow cathode reaction kinetics, numerous side reactions, and large polarization, which are intimately related to the discharge product of Li 2 O 2 . Here, we designed and prepared a modified Co 3 O 4 nanoparticle with atomic Ru substitution at octahedral Co sites supported by carbon nanocages (RuCoO x @HCNs) as a cathode catalyst. The asymmetrical octahedral Ru–O–Co units trigger a strong electron coupling effect, leading to charge redistribution and optimization of the d-orbital energy levels, thus facilitating oxygen activation and conversion into superoxide anions during discharging. More importantly, the Ru–O–Co units manifest high affinity for the intermediate LiO 2, inducing the rapid formation of unique nanoneedle-like Li 2 O 2 on RuCoO x @HCNs, avoiding the accumulation of byproducts and accelerating its decomposition during charge. These merit the Li–O 2 battery with RuCoO x @HCNs to deliver a reduced polarization of 0.96 V and a prolonged lifespan of over 2200 h.