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

Li-O2 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-O2 batteries with the cation vacancy-rich CoSe@MXene (VCo-CoSe2@MXene) as the case study. The formation of interfacial CoC bond between VCo-CoSe2 and Ti3C2 MXene and its enhanced covalency after introducing Co vacancy leads to promoted electron transfer from Ti3C2 MXene to CoSe2 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, VCo-CoSe2@MXene-based LiO2 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-O2 batteries by tailoring interfacial electron structure. To investigate the positive effects of intensely interfacial interactions caused by cation vacancy on the oxygen electrode reactions in Li-O2 batteries, cationic cobalt vacancy-rich CoSe2 are fabricated on Ti3C2 MXene (VCo-CoSe2@MXene). The generation of cobalt vacancies promotes the electron exchange between Ti3C2 MXene and CoSe2, reducing the reaction energy barrier of the oxygen electrode, ultimately leading to excellent electrochemical performance of Li-O2 batteries. image