Unique intermediate adsorption enabled by anion vacancies in metal sulfide embedded MXene nanosheets overcoming kinetic barriers of oxygen electrode reactions in lithium-oxygen batteries

ABSTRACT Designing electrode materials with optimized surface electronic structure and fully exposed active sites is urgently desired to improve oxygen electrode reaction kinetics in lithium-oxygen batteries (LOBs). Herein, sulfur vacancy-rich Ni3S2 on two dimensional MXene (VS-Ni3S2@MN) is fabricate as a bifunctional catalyst for LOBs. The introduction of sulfur vacancy via Ar plasma bombards exposes massive coordination unsaturated sites on the surface of VS-Ni3S2@MN, which is available for deposition and decomposition of uniformly distributed Li2O2 during oxygen reduction reactions and oxygen evolution reactions, thus efficiently decreasing overpotentials and ameliorating round-trip efficiency. In addition, theoretical calculations confirm that sulfur vacancies as the active sites can memorably improve the intrinsic appetency of intermediates and thus fundamentally adjust the deposition mechanism of Li2O2. Specifically, LOBs with the VS-Ni3S2@MN electrode afford remarkably decreased overpotential (0.77 V) and improved long-term cyclic stability (200 cycles with current density 400 mA g−1). This work provides a unique view that the regulation of intermediate adsorption via surface vacancies is a practical strategy for enhancing the performance of the LOBs and sheds new light on designing oxygen electrode materials.