Preparation Of Fiber-based Carbon Materials And Its Structure And Electrochemical Properties

As the resources and ecological crisis intensify,the development of low-cost,environmentally-friendly biomass materials have become one of the hotspots.Biomass resources are widely available,and it's the key to how to achieve efficient use of biomass.One of the important ways to efficiently utilize biomass resources is to develop electrochemical energy storage materials,especially for the application of supercapacitors electrode materials.The biomass material,especially the lignocellulosic raw materials have natural multi-stage porous structure,and have a rich pore structure on both the surface and the inside.After high temperature carbonization,the porous structure can still be retained.Therefore,it is advantageous to use lignocellulosic raw materials as electrode materials for supercapacitors after carbonization.Although the lignocellulosic raw materials have a rich pore structure,due to their wide sources and individual differences,leading to the structure of the carbonized electrode materials are greatly different and the unreasonable distribution of the pore structure,which also limits the use of biomass materials in the supercapacitors.Then,how to achieve the regulation of thier surface pore structure has become a key issue of the application in the supercapacitors.Based on the above analysis,the main research contents of this paper are as follows:(1)Firstly,Industrial filter paper was used as a template for lignocellulosic materials,Pluronic F127 as soft template and 3-aminophenol as nitrogen precursor.The mesoporous prepolymer self-assembly of the fiber raw materials was controlled by hydrothermal synthesis to regulate the surface pore structure.Nitrogen and oxygen doped lignocellulosic carbon materials were then prepared by carbonization and KOH activation.The results showed that the obtained carbon materials have a high specific surface area(1559 m2 g-1)and pore volume(0.80 cm3 g-1),and a well-developed pore structure.The total nitrogen and oxygen atom content can reach 17.25%.In the three-electrode system,the prepared lignocellulosic carbon material exhibited good electrochemical performance,taking 700? activation sample as an example,at a current density of 1 A g-1,the specific capacitance in a 6 M KOH electrolyte solution is 284 F g-1,at a current density of 20 A g-1,its specific capacitance can still be maintained at 173 F g-1.After 10,000 charge and discharge cycles,its capacitance retention was 98.6%,showing good electrochemical stability.(2)Industrial filter paper was used as a raw material template for lignocellulosic materials.By controlling the carbonization temperature from 600? to 800?,and then by carbonization and KOH activation,nitrogen and oxygen doped wood fiber-based carbon materials were prepared.Studies have shown that the wood fiber-based carbon material sample prepared at 600? in the three-electrode system and in the 6M KOH electrolyte solution,the specific capacitance can reach 325 F g 1 at a current density of 1 A g-1,even at a large current density of 50 A g-1,its specific capacitance can still remain 176 F g-1.The specific capacitance retention was 99%after 10,000 charge and discharge cycles.In the two-electrode system,the assembled button cell has a high specific capacitance of 300.8 F g-1 and good rate performance(capacitance retention of 69%from 0.1 to 20 A g-1)and good cycle life stability(capacitance retention is 97%after 10,000 cycles).(3)Poplar wood was used as biomass carbon-based material,Firstly,the wood flour raw material was delignified,and then the mesoporous prepolymer self-assembly is controlled by hydrothermal synthesis to control the pore structure.Finally,the wood fiber-based carbon material was prepared by carbonization and different activation methods of KOH.The results showed that samples with highly ordered mesoporous structure were prepared at 600?.And after KOH chemical activation,the specific surface area is as high as 1573.36 m2 g-1.In the three-electrode system of 6M KOH,the specific capacitance can reach 310 F g-1 at a current density of 0.5 A g-1,and the specific capacitance can still reach 215 F g-1 at a large current density of 20 A g-1.And only 4%loss of capacitance after 10,000 charge and discharge cycles.In the two-electrode system,the specific capacitance can reach 266 F g-1 and good rate performance(capacitance retention of 67%from 0.1 to 10 A g-1)and good cycle life stability.Its high power density characteristics also suggest its potential as a supercapacitor electrode material.