Application Of Transition Metal/Carbon Nanocomposites In Lithium Sulfur Battery And Oxygen Reduction

In the field of energy storage and conversion,new energy technologies such as lithium sulfur batteries or fuel cells cannot be widely applied due to various problems in sulfur cathode or oxygen reduction reactions,so new multi-functional materials need to be found.Carbon nanomaterials have attracted much attention because of their excellent electrical and chemical properties,but the commercial carbon nanomaterials have unsatisfied properties such as poor catalysis or adsorption capacity,which limit their further applications in the field of batteries.An effective solution is to combine with metal compounds which can greatly improve the electrochemical properties of carbon nanomaterials.However,due to the wide variety of metal compounds and the the tedious preparation process,there are still many challenges if we want to obtain carbon and metal compounds with excellent morphology and performance through a simple preparation processes.This thesis aims to prepare a carbon nanocomposites loaded with a metal compound by a simple experimental method,and the main contents of this article are as follows:(1)Ti-N-C material was prepared by one-step calcination method using melamine and titanium sulfate as precursors,and then Ti-N-C materials was applied to the cathode carrier material of lithium sulfur battery.The morphology,structure and groups of Ti-N-C material were analyzed by SEM,TEM,XRD,XPS and other characterization methods.It was found that Ti-N-C material is ultra-thin carbon nanosheets with a large number of TiN particles in the form of quantum dots attaching to its surface.After that,we studied the performance of lithium-sulfur battery with Ti-N-C material as sulfur carrier.The results show that Ti-N-C material has excellent catalytic ability,which can accelerate the conversion of lithium-sulfurate intermediate in battery reaction and greatly improving the cycle and rate performances of the battery.This Ti-N-C materials is a new type of sulfur carrier material with good application prospect.(2)Using melamine,titanium sulfate and ferric sulfate as precursors,Fe/Ti-N-C material was prepared by immersing the precursors with sulfuric acid and followed by a calcination process.The morphology,structure and composition of Fe/Ti-N-C material were analyzed by means of SEM,TEM,XRD and XPS.It was found that the Fe/Ti-N-C material is bamboo-like carbon nanotubes and there are a large amount ofTiN particles in the form of quantum dots attached to the carbon nanotubes wall.Then the sample was applied to the catalytic material of oxygen reduction reaction.After studying the oxygen reduction catalytic properties of the material,we found that the Fe/Ti-N-C material has slightly better catalytic performance than the Pt/C material,and its cycle performance and resistance to methanol poisoning are excellent,which prove that Fe/Ti-N-C material is a promising non-platinum oxygen reduction catalyst.(3)Co-SNBCNT material was prepared by one-step calcination method using thiourea,cobalt nitrate,boric acid and polyethylene glycol 2000 as precursors.Then the morphology,structure and composition of Co-SNBCNT were analyzed by SEM,XRD and XPS.It was found that the Co-SNBCNT material has a morphology of transparent and hollow carbon nanotubes,which is obvious different with that of the sample SNBC material prepared without adjunction of Co salt don't have.Furthermore,the oxygen reduction catalytic performance of Co-SNBCNT materials was studied.It was found that the catalytic performance of Co-SNBCNT material was comparable to that of Pt/C material,and its cycle performance and resistance to methanol poisoning were superior to Pt/C materials.