Cobalt–zinc carbides embedded in N-doped porous carbon nanospheres as polysulfide mediators for efficient lithium–sulfur batteries

Abstract

Developing high-efficiency interlayer catalysts is a promising tactic for improving the cycling performance of rechargeable lithium–sulfur (Li–S) batteries. Herein, using the Prussian blue analogue as the precursor, cobalt–zinc carbide nanocrystal-embedded N-doped porous carbon (Co₃ZnC@NC) is synthesized via simple post-carbonization. The obtained Co₃ZnC@NC nanospheres exhibit a robust core–shell structure showing good conductivity, high porosity and available metal active sites, favoring the interfacial charge transfer and the electron transport upon electrochemical reactions. The results demonstrate that the Co₃ZnC@NC catalyst is quite suitable for boosting the adsorption and redox conversion kinetics of soluble polysulfides. When acting as the separator interlayer, Co₃ZnC@NC contributes to improved Li–S batteries with a high discharge specific capacity of 1659.8 mA h g⁻¹ at 0.1C and superior cycling stability of over 250 cycles at 1.0C (high capacity retention of 84.1% after 100 cycles at 0.5C). Furthermore, the Co₃ZnC@NC-based battery can maintain a high discharge capacity of 734.0 mA h g⁻¹ at 5.0C, along with delivering a stable reversible capacity of 805.4 mA h g⁻¹ (∼5 mA h cm⁻²) after 50 cycles even under a high sulfur loading of 6.2 mg cm⁻². This study affords a viable way to construct highly dispersed bimetal/carbon composites for efficient catalysts and renewable energy devices.