S-decorated Mo2C as efficient catalyst for Li–O2 battery system

Abstract

Lithium–oxygen (Li–O₂) batteries are considered an important candidate for the next generation of energy storage systems due to their ultra-high theoretical energy density (11 586 mA h g⁻¹), but their slow kinetic reactions, high overpotential and cyclic instability seriously limit their practical applications. In this study, sulfur modified Mo₂C (S@Mo₂C) cathode materials were prepared by hydrothermal synthesis by sulfur (S) doping to optimize the electronic structure and catalytic activity of Mo₂C (Mo₂C). Experiments show that S@Mo₂C exhibits significantly improved electrochemical performance compared to commercial Mo₂C: its specific capacity is up to 3955 mA h g⁻¹ (commercial material only 508 mA h g⁻¹), the charge and discharge overpotential is reduced to 0.26 V (53.6%), and the capacity retention rate remains 77.8% after 250 cycles. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis showed that the introduction of sulfur induced the formation of a heterostructure of MoS₂/MoS₃ in the Mo₂C lattice, which enhanced the conductivity and oxygen reduction/precipitation (ORR/OER) activity of the material. In addition, sulfur doping promotes the formation of highly conductive amorphous Li₂O₂ and effectively inhibits the accumulation of insulating ring Li₂O₂, thus significantly improving the cycle stability and energy efficiency of the battery. This study provides a new structural regulation strategy for the design of high efficiency lithium oxygen battery catalysts.