Enhancing Li-S redox kinetics by fabrication of a three dimensional Co/CoP@nitrogen-doped carbon electrocatalyst

The design of sulfur hosts with high electrochemical activity and high sulfur loading plays a vital role in developing high-energy-density lithium-sulfur batteries. Herein, a novel type of sulfur cathode substrate is established via a facile two-step process, in which the Co and CoP nanoparticles are embedded in a three-dimensional (3D) porous nitrogen-doped carbon polyhedron (Co/CoP@NC). These Co and CoP nanograins not only act as polysulfides capturing centers but also the electrocatalysts effectively promoting the redox kinetics towards polysulfides conversion, as confirmed by the experimental results and DFT calculations. Meanwhile, the interconnected 3D porous N-doped carbon architecture contributed to Li+ transportation, electrolyte infiltration and relieves volume expansion of sulfur. Thus, Li-S batteries configured with the S@Co/CoP@NC cathode exhibit a remarkable enhancement in the rate capability and cycling performances. When sulfur content is controlled to be 75.8 wt%, the S@Co/CoP@NC cathode delivers an outstanding high-rate capability up to 30 C and low capacity decay rates of 0.033% and 0.03% per cycle over 1000 cycles at 1 C and 2 C, respectively.