Study On Preparation And Properties Of A New Type Of Three-Dimensional Graphene Cathode Materials For Lithium Sulfur Battery

Lithium sulfur battery is composed of lithium metal as anode, sulfur as cathode of the battery.Its theoretical specific energy can reach 2600Wh/kg, the theoretical of lithium capacity is 3860mAh/g, sulfur is 1675mAh/g, far more than the commercial battery systems.Lithium sulfur battery has great potential for development in recent years, due to the extensive attention of researchers. However, although the lithium sulfur battery has many advantages, but its commercialization by sulfur insulation, polysulfide solution, cycle performance of battery electrode caused by poor mechanical stability factors such as poor capacity attenuation and the limitations.In recent years, researchers are committed to sulfur- carbon composite material to improve the lithium sulfur battery overall performance.Three-dimensional graphene has good conductivity and pore structure for electron and ion transport and has good chemical stability, the elemental sulfur were compounded to form three-dimensional electrode structure is expected to become a good lithium sulfur battery cathode material.In this paper,the three-dimensional graphene was synthesized by hydrothermal method, sulfur and polypyrrole were further composite, two new three-dimensional structure of the nano composite materials obtained.SEM/EDS, FTIR, TGA were take as systematic characterization, finally assemble preparation of lithium sulfur batteries to study its electrochemical performance.First of all, 3D elastic graphene aerogel was prepared by hydrothermal method, effects of some parameters(graphene oxide concentration, carbon nanotubes(CNTs) ratio, etc.) on the elasticity and flexibility through simple and feasible technological process prepared hole size for 5-10μ m three-dimensional elastic graphene areogel. The three-dimensional graphene has good elasticity and flexibility, the compression recovery rate can reach 80%.Then, three-dimensional graphene and sulfur were composite as three-dimensional graphene-sulfur composite material, the material assembled into a lithium sulfur battery electrochemical characterization.The capacity can reach1386mAh/g at 0.5C.But in cycle performance found capacity attenuation is more serious, the reason maybe three-dimensional graphene cannot limit polysulfide dissolution.Finally, based on polypyrrole has very high electrical conductivity, three dimensional graphene sulfur material compound with,polypyrrole can well coated on sulfur layer surface to limit polysulfides dissolving, the materials were assembled into a lithium sulfur battery to study the electrochemical performance. It found that PPy coating layer of three-dimensional graphene- sulfur composite increase the conductivity of the composite and has a significant improvement in limit polysulfides.The specific capacity reached 1365mAh/g at 1C and still has 1097mAh/g capacity even after 600 cycles,the retention rate was 72.4%.