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.