One-step Synthsis Of Porous Carbon Hybridized By Chromium Nitride And The Study On Its Application In The Cathodes Of LI-S Batteries

Lithium-sulfur batteries have become one of the most potential next-generation rechargeable batteries to replace lithium-ion batteries due to their high theoretical capacity,inexpensive and environment-friendly sulfur cathode.However,due to the insulation of sulfur and Li₂S,the loss of active materials resulting from the diffusion of soluble intermediates,and the volume change of the sulfur cathode during charge and discharge,the lifespan and kinetics of lithium-sulfur batteries are difficult to satisfy commercial levels.To overcome the above shortcomings,many modification materials have been proposed.Among them,transition metal nitrides（TMNs）have become ideal host materials for lithium-sulfur batteries due to their outstanding physical and chemical properties of high electrical conductivity,excellent catalytic ability,chemical and thermal stability.However,the cumbersome synthesis method of TMNs limits its large-scale application.In this paper,according to the failure mechanism of lithium-sulfur batteries,N-doped porous carbon hybridized by chromium nitride（CrN@NPGC）composite was designed and synthesized through a simple one-step method.The use of urea instead of NH₃ as the nitrogen source in the synthesis of CrN@NPGC makes the method more practical.The structural characterization of CrN@NPGC demonstrated that CrN nanocrystals were uniformly distributed on the surface of the hierarchical porous carbon.Li₂S deposition experiments explored that CrN nanocrystals can act as Li₂S nucleation sites to promote its nucleation and induce three-dimensional growth of Li₂S,relieving the premature passivation of the cathode material surface during the discharge process,and effectively improve the electrochemical performance.Therefore,the specific capacity of CrN@NPGC-based lithium-sulfur batteries delivered a capacity of 1591 m A h g^-1 at 0.1 C.Even at a high current density of 6 C,there is still a capacity of 543 m A h g^-1.After 500 cycles at 0.5 C,the average decay rate per cycle is only 0.078%.These excellent electrochemical performances reflect the high sulfur utilization,excellent rate capability,fast reaction kinetics,and good cycling stability of CrN@NPGC-based lithium-sulfur batteries.In this paper,the structure of the sulfur host material is designed on the basis of the expected performance of lithium-sulfur batteries,and the material was synthesized by a simplified method and its action mechanism was systematically explored.