Preparation And Modification Of Supercapacitor Electrode Materrial Zctivated Carbon Fiber Fabric

Carbon materials are the first commercial electrode materials for supercapacitor application.Carbon materials have natural abundances.Their abundant pore structure make them possible to physically absorb and desorb charges on the surface based on double layer principle,which resulting good energy storage performance and long service life.As for flexible electrode application,carbon materials act as both electrochemical active materials and electrode materials.Design of composite material system based on carbon substrate can endow the flexible electrode with better electrochemical performance.Activated carbon has typical structural characteristics of carbon materials.Various fiber technologies enable activated carbon materials to be applied to flexible electrodes.Most activated carbon fibers are made from petrochemical products.In recent years,renewable and low-pollution biomass-based materials have attracted more attention.In this thesis,The natural cotton fabric was used as raw material,and the activated carbon fiber fabric was synthesized by impregnation with ZnCl₂ to change the carbonization temperature to synthesize the three-dimensional network structure.The results show that ZnCl₂can produce a trapezoidal heat-resistant structure for cotton fabric pretreatment,prevent the fiber surface from being destroyed at the initial stage of oxidation,and improve the thermal oxidation stability of the fiber.The appropriate carbonization temperature can increase the graphite crystallinity of the activated carbon fiber fabric and increase its Conductivity,and too high temperature will cause the surface of the fiber to break,resulting in a decrease in mechanical properties.Therefore,under the premise of excellent electrical conductivity,the mechanical properties should be guaranteed as much as possible,when the carbonization temperature is 1000°C.When the activated carbon fiber fabric has good electrical conductivity,mechanical properties,a large specific surface area,and a rich small pore size mesopores,it is a typical mesoporous carbon.Using the activated carbon fiber fabric prepared above,the surface was oxidatively modified by a liquid phase method by adjusting different immersion time,nitric acid concentration,and immersion temperature.The results show that with the increase of immersion time,the increase of nitric acid concentration and the increase of immersion temperature,the specific surface of activated carbon fiber fabrics first rises and then decreases,the mechanical properties are reduced to different degrees,and the electrical conductivity is increased.The oxygen-containing functional groups on the surface also tend to increase,and the carboxyl group increases at the fastest rate.When the immersion time is 6 h,the immersion temperature is 60°C,and the nitric acid concentration is 10 mol·L^-1,not only a large number of hydroxyl groups,lactone groups,phenolic hydroxyl groups and the like are introduced,but also the pore structure of the activated carbon fiber fabric is not produced.Excessive influence,while also increasing its specific surface,maintaining good mechanical properties and electrical conductivity.The modified activated carbon fiber fabric has good electrochemical performance,and its specific capacitance is 162.5 F·g^-11 at a current density of 0.5 A·g^-1,which is about twice that before the modification.The surface coating of the metal oxide is carried out by using the activated carbon fiber woven fabric before and after the above modification.The composite electrode of the active material was constructed by hydrothermal method of loading MnO₂ on the surface of the activated carbon fiber fabric.The surface of the modified fiber is evenly wrapped with?-MnO₂,and interlaced with each other to form a sheet-like structure.This structure can effectively obtain a large specific surface area and increase the contact area between the composite material and the electrolyte,which is in the electrolyte solution.The movement enhances smoother passages while increasing the utilization of active substances and the nature of diffusion transfer.The MnO2 attached to the surface of the unmodified activated carbon fiber fabric is not uniform,and the phenomenon of unwrapping or over-wrapping occurs.The composites showed good electrochemical performance before and after nitric acid modification.The specific capacitance was 250 F·g^-11 and 462 F·g^-11 at 0.5 A·g^-11 current density.