Application Of Complex Metal Compound And Carbon Material In Lithium Sulfur Battery

The energy density of commercial lithium-ion batteries is approaching the limit,but it still cannot meet the needs of rapid social development.The lithium-sulfur battery is one of the most promising next-generation energy storage battery systems,and its theoretical energy density is five times that of lithium-ion batteries,and sulfur is cheap and environmentally friendly.However,the development of Li-S batteries is actually hindered by some key problems,especially the dissolution of polysulfides,which leads to fast capacity decay and low coulombic efficiency.In addition,poor conductivity of sulfur results in lower utilization.This paper studied the electrochemical performance of multi-walled carbon nanotubes and graphene oxide in lithium-sulfur batteries,and improving the cycle stability by modification treatment.Then,this paper prepared the porous carbon by using the asphalt,and the cerium oxide is compounded with the porous carbon to obtain a sulfur positive electrode having good cycle stability.From the viewpoint of material adsorption,this paper prepared oxidized carbon nanotubes by a mild oxidation method.Compared to carbon nanotubes,the conductivity of oxidized carbon nanotubes is reduced,but the pore volume and the incorporation of oxygen are increased.The larger pore volume can form a strong physical adsorption,and the incorporated oxygen can be used as a polar site to form chemisorption with the polysulfide.Combined with physical and chemical adsorption,oxidized carbon nanotubes have better cycle stability at small current density.In addition,this work used the reduced graphene oxide as a carbon carrier and combine the molybdenum disulfide with the reduced graphene oxide by hydrothermal method.The composite material has adsorption and catalysis for polysulfide,which can lower polarization and charge transfer impedance of the lithium-sulfur battery.Through the exploration of the preliminary experimental process,this paper found that the combination of polar compounds and carbon materials can effectively improve the cycle stability of the battery.A reasonable structure is designed to obtain a cathode material with a large sulfur content.This paper prepared porous carbon with a large specific surface area by using inexpensive asphalt as a carbon source and potassium hydroxide as an activator.This porous carbon has a developed pore structure and can accommodate a large sulfur load.On the basis of this porous carbon,the nano-cerium oxide was supported in the porous carbon by the liquid phase impregnation method to improve the cycle stability of the lithium-sulfur battery.The addition of molybdenum disulfide and cerium oxide can significantly improve the cycle stability of lithium-sulfur batteries.The use of bitumen as a carbon source for the preparation of porous carbon has a great cost advantage,and can be applied to lithium-sulfur batteries on a large scale through post-treatment.The oxidized carbon nanotubes have better cycle performance at a small current density,and can be used as a conductive additive for lithium-sulfur batteries in the future.