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

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 (CoZnC@NC) is synthesized simple post-carbonization. The obtained CoZnC@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 CoZnC@NC catalyst is quite suitable for boosting the adsorption and redox conversion kinetics of soluble polysulfides. When acting as the separator interlayer, CoZnC@NC contributes to improved Li-S batteries with a high discharge specific capacity of 1659.8 mA h g 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 CoZnC@NC-based battery can maintain a high discharge capacity of 734.0 mA h g at 5.0C, along with delivering a stable reversible capacity of 805.4 mA h g (∼5 mA h cm) after 50 cycles even under a high sulfur loading of 6.2 mg cm. This study affords a viable way to construct highly dispersed bimetal/carbon composites for efficient catalysts and renewable energy devices.