Modification Of Starch-Based Activated Carbon And Its Electrochemical Performance As Supercapacitor Electrode Material

Super capacitors,as a new type of green energy storage device,have many advantages such as high power density,long cycle life,wide operating temperature and green pollution-free compared with other electrochemical devices,filling the gap of traditional capacitors and batteries.Among them,the characteristics of electrode materials determine the electrochemical performance of supercapacitors.Among the many electrode materials,carbon materials are the earliest developed and widely used electrode materials,and have always been the mainstream electrode material for supercapacitors.As a carbon source of biomass,starch has become a new source of carbon for supercapacitor carbon electrode materials due to its natural particle morphology and high carbon content.At present,the research on starch-based carbon materials has entered a new stage.How to further increase the specific capacitance of starch-based carbon materials has become an urgent problem to be solved.As we all know,the electrochemical performance of carbon electrode materials is affected by many factors.Therefore,based on the previous research,this paper modified the starch-based activated carbon to improve the electrochemical performance of carbon electrode materials.The research content of this article mainly includes the following three aspects:?1?The increase in the degree of graphitization of carbon materials helps to increase the electronic conductivity of the material and reduce the internal resistance of the material,thereby increasing the electrochemical performance of the material.In the third chapter of the experiment,using commercially available potato starch as the raw material,it was dipped in diammonium phosphate and lyophilized,then pre-carbonized to obtain starch carbon particles.Subsequently,in the process of KOH activation,by adding different transition metal salts?FeCl₂?4H₂O,CoCl₂?6H₂O,NiCl₂?6H₂O?,using a one-step low-temperature catalytic activation method,a highly graphitized starch-based activated carbon was obtained.The effects of different catalysts on the microstructure and electrochemical properties of starch carbon particles during heat treatment are discussed.After comparison,FeCl₂?4H₂O has a good catalytic effect on starch granules during heat treatment.After that,the influence of the amount of FeCl₂?4H₂O on the electrochemical performance of the material was explored to determine the optimal amount of addition.Under this condition,the resistivity of the graphitized potato starch-based activated carbon decreased to 0.187??cm,and the specific surface area reached2369m²/g.At a current density of 1A/g,its specific capacity is 198F/g,which effectively increases the specific capacitance of the material.And after 1000 cycles,the capacity retention rate can reach 99%,showing good electrochemical performance.Finally,taking the above-mentioned optimal sample carbon as the active material,the optimal beating process ratio was determined by changing the beating ratio of the active material and the conductive agent.When the content of the conductive agent is 5%,the electrochemical performance of the electrode material is optimized.Under the current density of 1A/g,its specific capacity can reach 222F/g.?2?Graphene has a high specific surface area,high conductivity,and high specific capacity,and is an ideal electrode material.Introducing it into activated carbon can effectively improve the electronic conductivity and specific surface area of activated carbon,thereby increasing the specific capacity of electrode materials.In the fourth chapter of the experiment,potato starch carbon particles were obtained by using commercially available potato starch as the raw material,and stable pre-carbonization with diammonium phosphate.Subsequently,two different composite methods were used to obtain graphene composite activated carbon materials with high performance.At the same time,the effect of graphene content on the microstructure,specific surface area and electrochemical performance of the composites was discussed.Through experimental comparison,the composite material obtained has a higher specific surface area and electrochemical performance by combining first and then activating.When the mass ratio of graphene to starch carbon is 8%,the specific surface area of the composite material is as high as 3023m²/g.Under the current density of 1A/g,the specific capacity can reach 241F/g.?3?The method of doping the carbon material with nitrogen atoms can change the surface chemical properties of the carbon material,improve the wettability of the electrode,and increase the diffusion rate of electrolyte ions;nitrogen atoms form a nitrogen-containing functional group after entering the carbon skeleton,and these nitrogen-containing functional groups can cause a pseudocapacitance of the electrode material,thereby increasing the specific capacity of the material.In the experiment in Chapter five,using corn starch as a raw material,after dicarbonate stabilized pre-carbonization and KOH activation,corn starch-based activated carbon was obtained.Subsequently,the post-treatment nitrogen doping method was used to dope the activated carbon with different nitrogen sources?urea,dicyandiamide,melamine?to obtain corn starch-based nitrogen doped activated carbon.The nitrogen doping effect and electrochemical performance of different nitrogen sources were explored.After,based on the above-mentioned optimal nitrogen source,a series of corn starch-based nitrogen-doped activated carbon was obtained by changing the heat treatment temperature and the nitrogen-doping ratio.The effects and electrochemical performance of nitrogen doping were discussed,and the optimal nitrogen doping process conditions were determined.Through experimental comparison,when the nitrogen-doping temperature is 800?and the mass ratio of activated carbon to melamine is 1:3,the prepared starch-based nitrogen-doped activated carbon has a nitrogen atom ratio of 7.31%and a specific surface area of 2144m²/g.At a current density of 1A/g,the specific capacity reaches 231F/g,which effectively improves the electrochemical performance of activated carbon.