Construction Of Nano-Carbon Based Electrode Materials And Their Application In Supercapacitors

With the continuous depletion of traditional fuels and the acceleration of environmental pollution,it is urgent to develop new energy storage devices to solve the contradiction between environment and energy.Supercapacitor shows a good industrial development trend.But the defect of low energy density limits its further application.In order to solve this problem,we can take effective measures to improve the current electrode materials or to develop new electrode materials.Therefore,by adjusting the structure and morphology of carbon and introducing heteroatoms,the nano-carbon based materials with excellent properties are developed,which can be used as active materials of double layer capacitors or as substrate to carry pseudo-capacitors materials,and to construct symmetrical or asymmetric supercapacitors to improve energy density.(1)Nitrogen and oxygen co-doped two-dimensional porous carbon materials were prepared by using graphene oxide template and structure directing agent by an electrostatic self-assembly process with cationic polyacrylamide and subsequent carbonization and KOH activation.The optimized PCN-3 material has the characteristics of large contact surface area,shorter ion diffusion path and abundant nitrogen and oxygen atoms on the surface(2.02 at.%N and 11.42 at%O).Therefore,the PCN-3 electrode exhibits a high specific capacitance of 242 F g-1(325.7 F cm-3)at 0.5 A g-1,good rate capability and superb cycling stabilization.In addition,the PCN-3//PCN-3 symmetrical supercapacitor delivers a high volumetric energy density of 22.1 Wh L-1 in 1 mol L-1 Na2SO4,showing good cycle stability(97.8%after 10000 cycles).(2)CNTs/microporous carbon composites with unique structure were synthesized by carbonization and activation of carbon nanotubes(CNTs)loaded with polyaniline particles.Optimal CNTs@NC-4 materials have high specific surface area,abundant micropore content and abundant nitrogen/oxygen heteroatoms(2.9 at.%N and 10.8 at.%O).It shows a high specific capacitance of 310 F g-1 at 0.5 A g-1,good rate capability and superb cycling stabilization.In addition,the CNTs@NC-4//CNTs@NC-4 symmetrical supercapacitor delivers high energy density of 18.6 Wh kg-1 in 1 mol L-1 Na2SO4,exhibting superior cycle stability(92%after 10000 tests).(3)The nano-carbon/CoNi hydrotalcite composites with three-dimensional core-shell structure were prepared by solution deposition method using nitrogen doped carbon/CNTs composite as substrate.Due to the reasonable design of the material structure and the synergistic effect between the components,the optimal N-CNTs@Co2Ni1-LDH material has high specific surface area,stable structure and good conductivity.It exhibits a high specific capacity of 693 C g-1 at 1 A g-1,excellent rate characteristics and cycle stability.In addition,the asymmetric supercapacitor delivers a high energy density of 51.3 Wh kg-1 and superb cycling stabilization.(92%after 10000 cycles).