Preparation Of Porous Carbons With Ultra-High Specific Surface Areas And The Study On The Capacitive Performance

Supercapacitors have the advantages of wide temperature range,high safety,long cycle life,large power density,and fast charging speed.They are widely used in new energy vehicles and some new electronic equipment.Electrode materials are a key factor that affects the performance of supercapacitors,the preparation of electrode materials with excellent performance is the focus of current research.Carbon materials are widely used as electrode materials for supercapacitors due of their stable physical and chemical properties,abundant sources and large surface area.In this paper,polyurethane foam and macroporous resin as carbon precursors were used to prepare porous carbon materials with ultra-high specific surface area by one-step chemical activation.The samples were analyzed by BET,XRD,Raman,TEM,SEM and XPS,and the effects of surface area,pore size and heteroatom doping on the capacitance were investigated.The details are as follows:1.Preparation and supercapacitors capacitive properties of nitrogen-doped carbon material with high specific surface areaPorous carbon materials with ultra-high specific surface area were prepared by chemical activation using polyurethane foam as carbon source and nitrogen source and KOH as activator.The experimental results show that the one-step method is simpler than two-step method,and the yield of the carbon material is higher and the specific surface area is larger..The carbon material FC700 activated at 700 oC has the highest surface area(3738 m² g^-1)and the largest pore volume(1.69 cm³ g^-1).This is due to the full interaction of KOH with polyurethane foam by one-step activation.In the three electrode system,the specific capacitance of FC700 is reaches 459 F g^-1.Assembled a symmetrical supercapacitor,the specific capacitance in KOH and LiNO3electrolytes can reach 368 F g^-1 and 336 F g-1,and the corresponding energy densities can reach 12.8 Wh kg^-1 and 37.8 Wh kg^-1.After 10000 cycles,FC700 still shows good stability.The excellent capacitance performance of FC700 can be attributed to high specific surface area,large pore volume and nitrogen atom doping.2.Preparation and supercapacitors capacitive properties of oxygen-doped carbon materialsUsing macroporous resin?AB-8?as carbon source,KOH as activator and oxygen source,oxygen doped porous carbon materials were prepared by one-step chemical activation method.The 600? activated sample PC600 has the largest specific surface area,pore volume and oxygen content,which are 3646 m² g^-1 and 1.89 cm³ g^-1 and12%,respectively.PC600 was tested in a 6 M KOH aqueous electrolyte,a high specific capacitance of 456 F g^-1 is achieved at a constant charge and discharge current of 0.5 A g^-1,and the specific capacitance is maintained at 325 F g^-1 at 50 A g^-1.In the two-electrode system with KOH and LiNO3 as electrolyte,the total specific capacitance is 95 F g^-1(single-electrode capacitance is 380 F g^-1)and 81 F g^-1(single-electrode capacitance is 324 F g^-1).After 10,000 charge-discharge cycles with a current density of 2 A g^-1,long-cycle stability of 97.89%and 93.83%of the initial capacitance was observed.It has a high energy density of 13.1 and 35.4 wh kg^-1 at a power density of 250 and 450 W kg^-1.