Preparation Of Heteroatoms Doped Carbon Materials And Their Electrochemical Properties

The development and progress of human society have driven large scale energy consumption and the energy crisis has intensified.The advanced energy storage technology is particularly important in today's society.Taking into account the energy density,power density,life,efficiency,safety and cost and other factors,lithium ion batteries has achieved great success.At present,the negative electrode of commercial lithium-ion batteries is mainly graphite,however,the low specific capacity of commercially used graphite anode material(372 mA h g-1)impedes the development of the lithium ion batteries.Various carbon-based,silicon-based,transition metal oxide or sulfide,and carbon-based electrode materials(carbon nanotubes,graphene,and porous carbon)have become very promising substitutes for the negative electrode materials of lithium ion batteries due to their high surface area,excellent electrical conductivity and structural stability.In addition,since the storage of sodium resources on the earth is much higher than that of lithium resources,sodium ion batteries has also gradually become a research direction for energy storage in the future.In this work,the nanorod-like graphene materials with high heteroatom content(nitrogen content 12.5 at.%,Sulfur content 3.7 at.%)and high specific surface area(686 m2 g-1)were prepared and applied to the negative electrode of lithium ion and sodium ion batteries for improving the performance of the batteries.In addition,the carbon fiber paper was treated with nitric acid and sulfuric acid,and then oxidized with potassium permanganate solution to modify its surface with oxygen-containing functional groups,Surface modified carbon fiber paper has good wettability to lithium metal and sodium metal,and has potential application value in lithium metal and sodium metal negative electrode.Specific work is as follows:1.Acid treatment and potassium permanganate oxidation to modify the surface of carbon fibers.A mixed solution of nitric acid and sulfuric acid as an oxidant to treat the carbon fiber paper to change the wettability of the surface,the potassium permanganate solution furtherly oxidized the carbon fiber paper.Lithium and sodium metal negative were prepared by contacting the molten lithium metal and sodium metal with the treated carbon fiber paper,respectively.2.Preparation of a nitrogen and sulfur double-doped nanorods-like graphene material.Polyphenylene sulfide(PPS)was used as a precursor of sulfur and carbon and crab shell was used as a biological template,regulating the calcination temperature in ammonia gas could control the doping amount of nitrogen and sulfur and obtained ordered and high doping amount carbon nanorods structure.3.High heteroatom content of nanorods-like graphene materials used in lithiumion batteries and sodium ion batteries anode.The material was coated on a copper foil to prepare a electrode slice and tested in the coin cell for electrochemical performance.It was found that the material calcined at 700 ? has the highest heteroatom content and the best electrochemical performance.For lithium ion batteries,the capacity was maintained at 2154 mA h g-1 at a current of 0.1 A g-1 for 100 cycles and was maintained at 625 mA h g-1 at a current of 5 A g-1 for 1000 cycles.For sodium ion batteries,the capacity was maintained at 303 mA h g-1 at a current of 0.1 A g-1 for 100 cycles and was maintained at 230 mA h g-1 at a current of 1 A g-1 for 3000 cycles.