Design Of Sulfur Host With Adsorption-catalysis And Study On Performance Of Lithium-sulfur Batteries

With the development of society,nowadays the energy storage system is hard to meet the needs of our daily life.Thus,it is urgent to develop a new type of energy storage system.Due to its high energy density,low cost,and non-toxicity,lithium-sulfur batteries are considered as one of the most promising next-generation energy storage systems.However,at present,the cathode materials of lithium-sulfur batteries are faced with the challenges of low electron and ion conductivity,the dissolution of intermediate products of lithium sulfide,and the poor reaction kinetics.To solve these problems,the physical-chemical and electrochemical properties of the cathode materials with defect prussian blue/carbon nanotubes and defect molybdenum disulphide/graphene were studied.The main research contents include the following two aspects:(1)A simple three-dimensional nanocomposite with a necklace-like structure was prepared by a simple liquid phase method,which contained carbon nanotubes and defective prussian blue nanocrystals.In this structure,the three-dimensional carbon nanotube conductive framework can provide efficient ion/electron channels.The rich lewis acid sites in prussian blue can effectively capture soluble polysulfides,while the defects can further provide sites for cata lytic conversion.The prepared sulfur@prussian blue/carbon nanotube composite cathode materials exhibit a high specific capacity,stable cycle performance,and fast kinetics.More importantly,whether it is theoretical calculations or experimen ts suggest that the adsorption capacity and conversion kinetics of prussian blue materials for polysulfides are highly dependent on the number of defects.This may further clarify the relationship between lewis acid sites and soluble polysulfide on the surface of Prussian blue crystal.(2)An ultra-thin molybdenum disulfide nanosheet was prepared by the hydrothermal method,then the ultra-thin molybdenum disulfide nanosheet was treated with Ar/N₂ plasma,thereby defective ultra-thin molybdenum disulfide nanosheets and defective ultra-thin molybdenum disulfide nanosheets with defects simultaneously doped with nitrogen were prepared.Then,pure molybdenum disulfide,argon plasma treatment,and nitrogen plasma treatment of molybdenum disulfide were mixed with reduced graphene oxide by ultrasonication in ethanol,respectively.Then,three types of molybdenum disulfide/reduced graphene oxide nanocomposite sulfur hosts were prepared.Among them,the reduced graphene oxide exhibits good electrical conductivity,which can provide good electron/ion transmission channels.Molybdenum disulfide can provide lewis acid sites to adsorb polysulfides,confirmed by the corresponding electrochemical experiments that the defect-containing molybdenum disulfide exhibits higher conversion kinetics and adsorption capacity than the pure molybdenum disulfide,and nitrogen doping further promotes the adsorption and catalytic conversion capacity of polysulfide.These findings may further inspire the method of plasma treatment for manufacturing defects to prepare corresponding positive effects on other electrochemical conversion systems.