Large-scale Preparation Of Graphitized Porous Carbon Material And Its Preliminary Application In Lithium-Sulfur Batteries

With the limitation of conventional energy and the increasingly prominent environmental problems,the electrochemical storage system of new energy characterized by environmental protection and renewable has been paid more and more attention.In the existing electrochemical energy storage battery system,the theoretical specific capacity of lithium-sulfur battery with elemental sulfur as the positive electrode is as high as 2600 Wh kg^-1,which is 8-10 times that of lithium-ion battery.In addition,the elemental sulfur has many outstanding advantages,such as abundant reserves,low price and environment-friendly,so the battery system has commercial value.However,elemental sulfur does not conduct electricity and can not be directly used as the cathode of lithium-sulfur battery.In order to enhance the conductivity of cathode materials for lithium-sulfur batteries,it is necessary to add suitable conductive materials to elemental sulfur to improve the conductivity of cathode materials.Porous carbon materials have many advantages,such as developed pore structure,excellent electrical conductivity,high stability,adjustable structure,low cost and so on.Therefore,porous carbon materials are often introduced into the cathode materials of lithium-sulfur batteries as conductive additives,which can effectively solve the problem of poor conductivity of elemental sulfur on the one hand,and disperse elemental sulfur better and reduce the loss on the other hand.Improve the utilization of elemental sulfur,and then improve the cycle performance and stability of the battery.This requires porous carbon materials to have high specific surface area,developed pores and excellent electrical conductivity.In fact,these structural factors often contradict and restrict each other.The development of pore structure will lead to the decrease of electrical conductivity of materials.Therefore,it is urgent to develop a new type of carbon material to balance the seesaw effect among these structural factors and optimize its pore structure and electrical conductivity at the same time.This paper mainly studies the design and preparation of porous carbon with high porosity and high graphitization degree,and discusses the feasibility of large-scale preparation of this kind of materials.The specific conclusions are as follows:?1?Using polymer carbonization method,using glycerol as carbon source,ferric chloride as pore-forming agent and graphitization catalyst,and introducing lithium acetate as weak acidic environment,rod polymer carbon precursors were synthesized by hydrothermal reaction.the effects of reaction temperature and reaction time on the morphology of the materials were investigated.Porous carbon materials with well-developed pore structure and certain graphitization structure were prepared by carbonization and iron removal of rod-like polymer.The BET specific surface area and total pore volume were 1675 m² g^-1 and 4.0 cm³g^-1 respectively.The lithium-sulfur battery assembled by this kind of graphitized porous carbon and elemental sulfur has a cycle specific capacity of 1269 mAh g^-1 at 0.2C and a capacity of 890 mAh g^-1 after 300 cycles at 0.5C.?2?The feasibility of large-scale preparation of polymer carbon precursors was explored,and rod-like polymer carbon precursors were synthesized in batches,and the prepared slurries were spray dried to obtain powdered particles with a particle size of about 20?m.The carbon material obtained by carbonization and iron removal of the polymer sample has a BET specific surface area of 1594 m² g^-1 and a total pore volume of 3.5 cm³ g^-1.The samples were characterized by XRD diffraction and scanning electron microscope.The data show that the samples are in good agreement with the samples synthesized in the small kettle.