Preparation And Electrochemical Performance Of Sulfur Cathode Material Of Carbon Aerogel Modified With Polyhydroxy Cyclic Compound

Lithium-sulfur batteries have attracted great attention due to their very high theoretical capacity and energy density,and are widely regarded as potential next-generation energy storage devices.But there are still some obstacles to overcome in its application.Much works have been focused on how to improve the redox reversibility and inhibit the loss of sulfur to maintain the capacity.This paper develops a new strategy,based on the intelligent electric-field response to build the surface structure and design a special molecular film with quaternary ammonium groups,the response film bonded to the carbon aerogel is used as a switch to control the polysulfide channel.At the same time,the prepared carbon aerogel?CA?exhibits a highly cross-linked 3D framework,abundant hierarchical pore channels and high specific surface area.The quaternary ammonium group modified carbon aerogel was prepared by surface film bonding on KOH activated CA with a specific surface area of1585 m² g^-1.The materials were further characterized by various means including BET.The results show that the composite sulfur cathode with selective film has outstanding high discharge capacity and long-term cycle stability.The cathode with 61.6 wt%sulfur loading showed an initial specific capacity of 1307 mAh g^-1 at 0.2 C and maintained a capacity of 84.0%after 100 cycles.The improved electrochemical performance mainly benefits from the switching function and selective control of the self-responsive film,effectively preventing polysulfide from escaping from the cathode,suppressing the shuttle effect and improving the utilization of sulfur.In addition,the adsorption calculation by the density functional theory?DFT?shows the trapping role of beta-cyclodextrin quaternary ammonium?CDQA?to polysulfides.DFT simulation further supports the restriction and self-response mechanisms.In this paper,a new strategy of surface film is carried out.At the same time,this paper also focuses on the regulation of the internal structure of carbon aerogel,and further regulates the porous structure of carbon matrix based on template method.The pseudopolyrotaxane?PPR?was synthesized by coating?-cyclodextrin with polyethylene glycol,and PPR-CA was prepared by sol-gel method.PPR effectively regulates and forms a porous structure.The porous carbon matrix will provide a structural basis for high sulfur loading and will facilitate the full utilization of sulfur active materials.The PPRx-CA/S electrode exhibits excellent electrochemical performance.In particular,PPR2-CA/S exhibited a uniform particle size and uniform pore structure.The first charge and discharge capacity of PPR2-CA/S with a sulfur loading of 75.02 wt%reached 1158 mAh g^-1 at 0.2 C rate.The composite achieved a first capacity of 1049 mAh g^-1 at 0.5 C,and still achieved a capacity retention of 76%after 300 cycles.The uniform porous structure of PPRx-CA can effectively store high content of active sulfur source,prevent sulfur agglomeration and adsorb polysulfide,enhance the conductivity of composite materials,and inhibit the"shuttle effect"of battery charging and discharging process.