Porous Carbon And Its Electrical Storage Properties Were Prepared By Melting Mixed Salt/Alkali Activation Method

The energy crisis has become a major problem that needs to be solved in the development of today’s society,and one of the solutions is to improve the efficiency of energy conversion.Two of today’s more efficient components are rechargeable batteries and supercapacitors.Supercapacitors are widely concerned because of their high power density,long cycle life and wide operating temperature limit.However,the current activated carbon has the problems of low capacitance,poor conductivity and uncoordinated structure.Therefore,how to improve the structure and surface state of carbon materials has become a research direction to improve the performance of supercapacitors.With ginkgo leaf as raw material,this paper uses the molten salts/alkalies chemical activation of the prepared high specific surface area,uniform pore size distribution,containing N and S heterogeneous elements doped hierarchical porous carbon materials,and the field emission scanning electron microscopy（FESEM）and high resolution transmission electron microscopy（HETEM）,specific surface area test（BET）,Raman spectroscopy（Raman）and X-ray photoelectron spectroscopy（XPS）had been used to characterize the morphology,structure and composition of porous carbon materials.Cyclic voltammetry（CV）,constant current charge-discharge（GCD）and alternating current impedance spectroscopy（EIS）tests were carried out in 6 M KOH aqeous electrolyte by two-electrode method to investigate the electrochemical properties of porous carbon materials.Specific research contents are as follows:（1）Used ginkgo biloba leaves as raw materials,KCl and Ca Cl₂ as activators,porous carbon materials with heterogeneous atoms such as N,S and O（2.06%,0.55%and 11.04%,respectively）and suitable pore size distribution were prepared by the method of mixed molten salts activation in argon atmosphere.The porous carbon materials were electrochemical tested by electrochemical workstation and battery tester.The experimental results show that the sample has a specific capacitance of 150F g^-1(the current density is 0.05 A g^-1),and the capacitance retention rate is 94.2%after circulating 10000 times under the current density of 1 A g^-1,showing good cyclic stability.EIS test results also show that the resistance of the sample is smaller（internal resistance is 0.7Ω）as well as good diffusion property and electrical conductivity.（2）Used ginkgo biloba leaves as raw materials,KCl and K₂CO₃ as activators,porous carbon materials with heterogeneous atoms,up to 1675.29 m² g^-1high specific surface area and suitable pore size distribution were preparedby the method of mixed molten salts activation in argon atmosphere.The experimental results showed that at the current density of 0.05A g^-1,the specific capacitance of the sample was 215.18 F g^-1,and even at the current density of 20 A g^-1,the specific capacitance remained at169.82 F g^-1.When the power density is 25.42 W kg^-1,the energy density is 7.47 Wh kg^-1.After 10000 cycles,the capacitance retention rate is 98.4%.Resistanceof the supercapacitor is small（internal resistance is 0.9Ω,the charge transfer resistance of only 0.3Ω）.（3）Used ginkgo biloba leaves as raw materials,Na OH and KOH as activators,porous carbon materials with heterogeneous atoms,up to 1975 m² g^-1 high specific surface area and suitable pore size distribution were prepared by the method of mixed molten salts activation in argon atmosphere.The experimental results show that the specific capacitance of the sample is 333.4 F g^-1 at the current density of 0.1 A g^-1.When the current density is 20 A g^-1,the specific capacitance remains 277.5 F g^-1,showing good rate performance.Moreover,under the current density of 5 A g^-1,after10000 cycles of constant current charging and discharging,the capacitance retention rate is 94.4%,showing a good rate performance.