Cation Vacancy Modulated Interfacial Electronic Interactions for Enhanced Electrocatalysis in Lithium–Oxygen Batteries

Abstract Li–O 2 batteries deliver ultrahigh theoretical specific energy while suffering from low energy efficiency and poor cyclability due to sluggish kinetics of oxygen electrode reactions. Herein, a strategy of engineering interfacial electron structure of MXene‐based composites is presented to boost oxygen electrode reactions for advancing Li–O 2 batteries with the cation vacancy‐rich CoSe@MXene (V Co ‐CoSe 2 @MXene) as the case study. The formation of interfacial Co─C bond between V Co ‐CoSe 2 and Ti 3 C 2 MXene and its enhanced covalency after introducing Co vacancy leads to promoted electron transfer from Ti 3 C 2 MXene to CoSe 2 and optimized electronic structure of interfacial Co sites, especially the second Co sites neighboring Co vacancy, which serve as the active centers for oxygen redox reactions. On this basis, V Co ‐CoSe 2 @MXene‐based Li─O 2 batteries exhibit low overpotential (0.35 V) and excellent cycling stability (250 cycles at 500 mA g −1 ). This work proposes an effective strategy to develop MXene‐based electrocatalysts for Li–O 2 batteries by tailoring interfacial electron structure.