Study On Preparation And Electrochemical Performances Of Carbon/Sulfur Composite Cathode Material

In recent years,along with the rapid development of economy,people's demand for energy is growing exponentially,especially in the research and development of battery become focus of attention of people.Lithium battery become the preferred source of all kinds of electronic products and electric vehicles for their advantages in high energy density,no memory effect and the friendly environment.Element sulfur as the positive material for lithium batteries become a new generation of high-energy lithium-ion battery's first choice,because of its low cost,natural abundance and high specific energy.In this system,however,there are still shortages such as low utilization rate of active material and poor circulation performance,in order to solve these problems,it is necessary to improve the conductivity of the cathode materials and to inhibit the dissolution of polysulfide.The activated carbon material are chosen as the matrix of sulfur-based composites because of the high specific surface area and good electrical conductivity,to improve the performance of the composite materials.In this paper,high specific surface area activated carbons are prepared by rice husk and alkali lignin,and by the melting diffusion method to synthesize carbon/sulfur compound material.By comparing the introduction of commercial activated carbon with the self-made,founding that the electrochemical performance of carbon/sulfur composite electrode prepared by alkali lignin is better than that of commercial activated carbon and rice hull.It is found that the structure of carbon has a crucial effect on the electrochemical properties of carbon/sulfur composites.This paper in order to prepare more suitable activated carbon to synthesis sulfur,mainly discussing the kinds of activator,impregnation ratio,activation temperature and activation time affect carbon structure.The results show that activated carbon prepared with phosphoric acid as activator,impregnation ratio of 1:3,activation temperature of 550? and activation time of 1.5h is most suitable as the matrix material of sulfur.On the basis of the above research,by using alkali lignin as carbon source,only change the impregnation ratio on this occasion,the result found that the impregnation ratio of 1:4,the activated carbon suitable for sulfur as matrix material.The initial discharge capacity of carbon/sulfur composites can reach up to 908mAh/g,and also keep on top of 100mAh/g after 100 times,the performance is better than using cellulose as carbon source.In order to improve the attenuation of composite materials,using of ether electrolyte in the assembly of the battery,the charging and discharging of lithium-sulfur battery is further analyzed.