Study On Preparation And Electrochemical Performance Of Porous Carbon Composite Materials

Energy is the foundation of modern economic and social development.In the past few decades,rechargeable lithium-ion batteries(LIBs)have been the main energy storage devices for portable electronic devices and electronic vehicles.However,the electrochemical performance of current commercial LIBs can not meet the demands of batteries in modern society.Lithium-sulfur battery,as a kind of lithium battery,generally uses sulfur as the cathode materials,which has higher theoretical specific capacity and battery theoretical specific energy than LIBs,which are 1675 mAh·g-1 and 2600 Wh·kg1.Moreover,elemental sulfur is widely distributed on the earth,low in price,and environmentally friendly,and it is a kind of lithium battery which have more research value and potentiality.However,the low conductivity of the elemental sulfur of lithium-sulfur batteries,the shuttle effect of poly sulfides,and the large volume changes of sulfur anode all restrict the commercial application of lithium-sulfur batteries.The design and manufacture of nanostructured electrode materials is a common way to solve the two problems.In summary,this project explores from the two perspectives of LIBs and lithium-sulfur batteries.On the one hand,based on the work of the previous research group,the V2O5 is used as a template,the reasonable nano-structured porous composite carbon materials constructed by structural design experiments were perfected;on the other hand,small-molecule organic monomer pyrrole was used as raw materials to prepare sulfonic acid-modified porous carbon materials at low temperatures.The main research results include:(1)On the basis of the work of the previous research group,compared the 2D mesoporous nanomesh structure composed of N-doped carbon-coated V2O3 nanowires prepared by freeze drying(V2O3@N-C Nm),pure V2O3 nanomesh(V2O3 Nm)and the V2O3@N-C nanocomposite prepared by conventional drying(V2O3@N-C Nc)structure,in-depth exploration of the advantages of the V2O3@N-C Nm.The excellent electrochemical performance of V2O3@N-C Nm as LIBs anode is mainly due to its unique nano-network structure,which can promote the lithiation/delithiation process.In addition,its nitrogen-doped carbon conductive shell can enhance conductivity and effectively limit the volume changes of V2O3.(2)Different from the existing common polymer high-temperature carbonization method,this part uses small molecule pyrrole monomer as the raw materials,and mixes with concentrated sulfuric acid at a lower temperature to cause a sulfonation reaction.At the same time,excessive concentrated sulfuric acid will carbonize the pyrrole.After centrifugal washing and drying,sulfonic acid group modified carbon material(C-SO3H)will be generated.After being carbonized by concentrated sulfuric acid,pyrrole has more pores and good electrical conductivity.The sulfonic acid group can promote the adsorption of polysulfide.In addition,sulfonic acid groups can act as active sites to improve the utilization of active sulfur.Electrochemical tests were performed on a lithium-sulfur battery assembled with a carbon/sulfur composite cathode prepared by sulfur-carrying C-SO3H,and the results show that it has good electrochemical performance.