Construction Of Porous Carbon-based Materials Derived From Biomass And Its Application In Lithium-sulfur Batteries

Energy as the basics of human society produces,that is an inevitable trend to choose high-quality energy and advanced energy technology to replace the traditional non-renewable energy.Electrochemical energy storage systems have attracted much attention,among which lithium-sulfur battery is expected to become a new generation of commercial energy storage batteries after lithium-ion battery,due to its high theoretical specific capacity(1675 mAh g^-1)and theoretical specific energy(2600 Wh kg^-1).In the lithium-sulfur battery,the active material（S）of the cathode and reaction product（Li₂S/Li₂S₂）with poor electrical conductivity,which require the substance with good electrical conductivity to provide the electron transport channel.In this paper,biomass materials with rich storage and unique structure were used as carbon sources,investigating the application of carbon materials constructed by different methods in lithium-sulfur battery.1.The yeast cultured in glucose was used as carbon source,and KOH was used as activator to investigate the effects of different carbonization temperatures on the structural morphology of the materials.The results show that the microporous carbon materials（MPCs）prepared at 800℃ have a very high specific surface area(2410 m² g^-1),and the specific capacity of the first discharge as cathode material is as high as 1502mAh g^-1 at 0.2C.2.Algal biology（nori）was used as carbon source,and KOH of different concentrations was used as activator to treat precursor materials.The results show that the carbon material prepared at 2 M KOH and 800℃ exhibits honeycomb structure.As substrate materials of sulfur that is benefits for ion transport and electrolyte penetration.Simultaneously,that can alleviate volume expansion effect during charge/discharge process.In addition,transition metal oxide was added to the carbon material to obtain CoO modified honeycomb porous carbon material（CoO-HPC）.As a cathode material,the first discharge specific capacity is as high as 1215 mAh g^-1 at 0.5C,and the specific capacity remains 655 mAh g^-1 after 100 cycles.That is greatly improved compared with unmodified HPC carbon material,which is only 542 mAh g^-1 after 100 cycles.3.Porous carbon materials were prepared by using different activation methods to treat purple sweet potato that with pore structure.The effects of activator types and activation methods on the morphology,structure and electrochemical properties of the materials were studied.The results showed that when the molar ratio of KOH and Zn（OAC）₂·2H₂O was 1:1,the carbon materials possess more porous structures than those treated by other methods.High quality structure is great importance to the performance of materials.In lithium-sulfur batteries,carbon materials with rich pore structures also exhibit excellent electrochemical performance.