| Electric double-layer supercapacitor（EDLC）has become one of the most efficient energy storage devices because of its fast charging and discharging speed,high safety,high power density and long cycle life.It is of great strategic significance to the development of carbon neutralization and national energy security in China.However,the problems of low energy density,serious capacitance loss under high current density and high preparation cost seriously restrict the development and commercial application of electric double-layer supercapacitors in the field of energy storage.In this paper,the energy density of the device is improved by improving the specific capacitance of electrode materials and broadening the operating voltage window of the electric double-layer supercapacitor,and the cost of the supercapacitor is reduced by improving the preparation yield of carbon materials and optimizing the device assembly process,so as to enhance its application potential.The main results are as follows:Using cellulose as precursor,L-cysteine and melamine as sulfur and nitrogen sources,cellulose based porous activated carbon was prepared by high temperature carbonization followed by high temperature KOH activation process.The effects of melamine and L-cysteine on the thermal stability,yield and microstructure of cellulose during carbonization were investigated.The results show that the introduction of melamine and L-cysteine can inhibit the escape of small molecular gases during cellulose pyrolysis and improve the thermal stability of the materials.Finally,the yield of cellulose based carbon materials can be increased to 20%.The results of electrochemical performance test show that when the current density is 1 A g-1,6 m KOH is used as electrolyte in the three electrode system,the specific capacitance of the prepared cellulose based carbon material is up to 301 F g-1.In the two electrode system,10 mol kg-1 Na OTF was used as electrolyte,and the current density was 1A g-1,the specific capacitance of the prepared cellulose based carbon material is up to 45 F g-1,At 50 A g-1,the capacitance can be maintained at 27 F g-1,and the capacitance retention rate is 60%.The energy density is 38.5 wh kg-1@1.23 k W kg-1.Using commercial activated carbon YP-50F as electrode carbon material and lithium sulfate as electrolyte,from the point of view of process optimization,lithium sulfate and carbon were directly mixed to construct an electrolyte——electrode material integrated double-layer supercapacitor.In addition,by exploring the microstructure of the interface between electrolyte and electrode,it is found that lithium sulfate adheres to the carbon surface,hinders the direct contact between water and carbon,and inhibits the high-voltage polarization of water,so as to broaden the voltage window,secondly,the lithium sulfate on the carbon surface dissolves to form ions,which are preferentially adsorbed in the process of charging and discharging,which shortens the ion transmission distance,widens the voltage window and accelerates the charging and discharging rate.The operation voltage window can be widened to 2.1 V,When the current density is 1 A g-1,the mass specific capacitance is 32F g-1,When the current density is 4 A g-1,the voltage drop is only 0.08 V,The scanning speed can reach 6 V s-1,The energy density is 19.3 Wh kg-1@1049.2 W kg-1,under the current density of 1 A g-1,after 6000 times of constant current charge discharge test,the mass specific capacitance retention rate is still as high as 80%.In addition,from the perspective of process flow,this method saves the process of electrolyte configuration and electrode material adaptation,does not need conductive agent,and does not need to stand after assembly.It has the advantages of simple preparation process,assembly time,simple device operation and easy industrialization. |
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