Research On The Preparation,and Surface Modification Of Porous Carbon Materials And The Properties For Lithium-sulfur Batteries

The lithium-sulfur battery with many advantages,like the high energy density of 2500 Wh·kg^-1and a theoretical specific capacity of 1675 m Ah·g^-1,is becoming a popular research topic for the next generation of new energy storage battery.It is also cheap in resource materials of sulfur,nontoxic,and highly abundant.However,there are a few shortcomings,such as the low conductivity and its shuttle effect,which restrict the commercialization of lithium-sulfur batteries.Based on previous studies,we research the catalytic properties of phosphorus-containing modified porous carbon materials influence on their electrochemical properties and explore the commercial porous carbon modification.Then we prepare porous carbon material as a cathode for lithium-sulfur battery by burning straw and improve the electrochemical performance by modification.From the perspective of catalysis and chemisorption,we prepare the rGO from graphite oxide by high temperature reduction.Then the r GO was added to the methylphosphonic acid methanol solution at 110°C,and the phosphorus-containing groups were combined with r GO by high temperature reduction oxidation.The sulfur was loaded into the carbon material matrix by a melting met hod to prepare a sulfur/carbon composite with a sulfur loading of more than 60 wt.%.As shown in the results,although the content of phosphorus was tiny,the electrochemical performance of the battery was still greatly improved under the destruction of the pore structure of the carbon material substrate.It is mainly ascribed to the contribution of chemisorption and catalysis,which can improve greatly the electrochemical performance of battery.Based on the results of previous experiments,we make a modificationon commercialized porous carbons for lithium-sulfur batteries to improve the performance of batteries.At the same time,we prepare the porous carbon by burning straw to obtain commercially available,high performance,non-polluting materials for lithium-sulfur batteries and promote the commercialization of the lithium-sulfur battery.In addition,we also prepare the porous carbon by using straw as biomass precursor material and zinc chloride as pore-forming activator.The porous carbon has excellent pore structure,which exhibits excellent electrochemical performance as a lithium-sulfur battery cathode material carrier.Based on this,the hydrothermal method is used to generate microcrystalline iron sulfide in situ on KMC,and its catalysis and chemisorption are used to enhance its discharge capacity and cycle stability of the battery.At the same time,we use the FeSe₂ as the additives to enhance its electrochemical performance.The results show that the phosphorus-containing modified carbon materials allows to improve the performance of lithium-sulfur batteries,but it may make a destruction of the pore structure of carbon materials.The carbon material prepared from agricultural waste straw has the advantages of small pore size,large specific surface area,low cost of raw materials,simple process.The carbon material is sulfur-supported by the melting method,the performance of lithium-sulfur battery is excellent.It can provide a practical solution for lithium-sulfur battery commercial application.Finally,the transition metal chalcogenide is used as adsorbent and catalyst to modify the porous carbon material,which can also improve the battery performance.