Synthesis And Performance Of Porous Carbon @MoS₂ Composite Nanofibers For Lithium-sulfur Batteries

It is urgent to develop the two times battery system with high energy density and low cost in the upgrading of electronic products.Lithium-sulfur batteries are considered to be one of the potential energy storage systems because of their high theoretical capacity(1675 mA h g^-1)and high specific energy(2600 W h Kg^-1)and the low cost pollution-free sulfur elemental.But the shortcomings constrain the march towards commercialization.The insulation of sulfur and lithium sulfide lead to low utilization of sulfur and real capacity of active substances,the volume change of sulfur in the process of lithium/lithium intercalation is easy to destroy the material structure,and the intermediate products dissolved in electrolyte produce shuttle effect and reduce the coulombic efficiency,these problems seriously affect the actual capacity and cyclic performance of lithium-sulfur battery.How to change this situation is the key to improve the actual capacity and cycle performance of lithium sulfur batteries.Considering that carbon fibers have the advantages of high specific surface area,high electronic conductivity and buffer volume expansion of fiber networks,the porous graphitized carbon/sulfur composite fibers were prepared by electrospinning technology with ferric acetylacetonate and PVP as raw materials.The graphitized carbon/molybdenum disulfide@sulfur composite fibers were obtained by further growth of molybdenum disulfide on the composite fibers surface,the above materials all showed excellent properties,and the work of this paper is as follows:?1?Preparation and electrochemical properties of porous graphite carbon fiber/sulfur composites with 3D structure.Using iron oxide as pore-forming agent and catalyst,PAN as carbon source,the composite nanofibers were prepared by electrospinning,annealing and acidification of the fibers,and then heat-treated at 155?with a certain proportion of sulfur.As a pore-making agent,ferric oxide is used to disperse several nanometer sulfur particles in porous composite fibers,to prevent sulfur particles from agglomeration,to improve the conductivity of carbon fiber,and to physically limit the reaction space of sulfur,and as a catalyst,to make the carbon graphite around the pores further improve the conductivity.This composite fiber is used as a self-supporting material.The initial reversible capacity is high to 1250 mA h g^-1 at 0.1C,and the capacity remains at 720 mA h g^-1 after 200 cycles at 1C,even if the reversible capacity of the 2C high charge/discharge ratio is still up to 670 mA h g^-1.?2?Study on preparation and electrochemical properties of G-CNFs@MoS₂/S composites.We grow MoS₂ on the surface of the fiber mentioned above,the G-CNFs@MoS₂/S composites were obtained.Iron oxide are corroded to leave room,which can effectively alleviate the volume change caused by charging and discharging.As a charge-discharge reaction site,MoS₂ nanosheets effectively restrict the diffusion of polysulfides,thus alleviating the shuttle effect.As a charge-discharge reaction site,MoS₂ nanosheets effectively restrict the diffusion of polysulfides,thus alleviating the shuttle effect.The results showed that the material exhibited good electrochemical properties Its initial specific capacity reaches 1351 mA h g^-11 at 0.1C current density,the specific capacity remains 910 mA h g^-1 after 200 cycles at 0.1C,and its reversible capacity remains 524 mA h g^-1 after 500 cycles at 1C.