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Research On The Performance Of Supercapacitors Based On Biomass Activated Carbon Materials

Posted on:2021-04-02Degree:MasterType:Thesis
Country:ChinaCandidate:H K DengFull Text:PDF
GTID:2392330614460133Subject:Power engineering
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As a new type of electrical energy storage components,supercapacitors have the characteristics of short charging time,long service life,large power density and wide application temperature range,and have received extensive attention and research from researchers.There are two main factors that affect the performance of supercapacitors,one is the electrode material,and the other is the selected electrolyte system.Among various electrode materials,carbon materials are widely used as electrode materials for supercapacitors due to their simple preparation and large specific surface area,high electrical conductivity and electrochemical performance.Biomass has a wide range of sources and low prices,and it is a renewable resource.Research and development of high-performance biomass activated carbon electrode materials is one of the research hotspots of supercapacitor electrode materials.In order to reasonably use and transform biomass energy and reduce pollution,based on this paper,agricultural waste soybean meal is used as raw material to prepare high-performance activated carbon materials through different processes.And on this basis,by further changing the electrolyte system to enhance the electrochemical performance of the capacitor.Firstly,soybean meal is used as raw material,and KOH is used as an activator.Using the characteristics of soybean meal rich in a large amount of protein,nitrogen,oxygen and other elements,through direct carbonization and steam thermal pre-carbonization,biomass is synthesized at different temperatures and different activator ratios Activated carbon.The characterization results show that the synthesis with the mass ratio of alkali to biomass of 2:1 and activation temperature of 800?is the best structural and electrochemical performance sample in the direct carbonization method.The specific surface area of the activated carbon is 1,766.4 m~2/g,and the specific capacitance reaches 160.6 F/g when the current density is 1 A/g.The samples subjected to steam thermal pre-carbonization achieved the best specific surface area of 2,128.2 m~2/g,and the best specific capacitance of 181.7 F/g at 1 A/g current density.Then,nitrogen doping is used to improve the material heteroatom defect.By adding a urea solution in the preparation process,the concentration of added urea is adjusted,and the influence of nitrogen doping on the performance of the material as an electrode of the supercapacitor is explored.The results show that the doping efficiency is the most obvious when the concentration of added urea is 0.5 mol/L.The absolute C-N content of the nitrogen-doped soybean meal biomass activated carbon is 10.57%,which contains 1.71%pyrrole nitrogen and 1.89%pyridine nitrogen.And the sample after nitrogen treatment has higher specific capacitance than before.Finally,in order to further study the effect of the electrolyte system on the supercapacitor,new reagents sodium carboxylate and calcium reagent sodium carboxylate were introduced.By adjusting the concentration of the introduced reagent,the effect of the new redox active electrolyte system on the specific capacitance of the material was explored.The results show that when sodium carboxylate is added to the alkaline electrolyte,it cannot bring about an increase in specific capacitance.But sodium carboxylate additives can expand the voltage window range.In the electrolyte system CN-2,the voltage window is expanded from-0.8V?0V to-1V?0.4V,and when the voltage window is-1V?0.2V,the electrochemical performance did not decay,and it brought a 0.4V increase in voltage range steadily.After adding the calcium reagent sodium carboxylate,the specific capacitance of the supercapacitor has been doubled.In the electrolyte system CS-1,the specific capacitance was measured at a current density of 1 A/g to reach 438.1 F/g,which is 1.9 times that of sodium calcium carboxylate not added.
Keywords/Search Tags:biomass, activated carbon, supercapacitor, nitrogen doping, electrolyte
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