Regulating Electrocatalytic Polysulfides Redox Kinetics through Manipulating Surface Electronic Structure of Molybdenum-Based Catalysts for High-Performance Lithium-Sulfur Batteries

The polysulfide shuttle effect and sluggish reaction kinetics still severely impede practical application of lithium-sulfur batteries. Rational design effective electrocatalysts bring new functionalities to suppress polysulfide migration and accelerate sulfur conversion kinetics. Herein, the Mo/Zn bimetallic imidazole framework (Mo/Zn BIF)-derived Mo2C nanoparticles are designed with dual functions of strong chemisorption and high catalytic capability. The internal unoccupied d-orbit of Mo on the surface results in electron deficiency, endowing the Mo2C with abundant active sites and strengthened LiPS adsorbability. The regulated electronic structure of Mo–C–Mo leads to high conductivity and accelerated catalytic conversion. This combination of surface modulation and nanoflower architecture design results in favorable trapping–diffusion–conversion of LiPSs on the interface. Consequently, the lithium-sulfur batteries with Mo2C-modified separator exhibit enhanced electrochemical performance with outstanding rate performance (520 mAh g–1 at 4C) and cyclic stability (decay 0.067% per cycle during 570 cycles at 1C). Even with a sulfur loading of 8.0 mg cm–2, the batteries can still maintain an areal capacity of 6 mAh cm–2 over 45 cycles under 0.1C. This work provides an insightful investigation on atomic engineering and may guide rational design of electrocatalysts to boost the commercialization of Li-S batteries.