| Supercapacitors have attracted wide interest because they can safely provide high power and can be quickly charged with extremely long cycle life.This dissertation studys activated carbon materials and transition metal compound materials respectively,and solves the problems of low surface area and low specific capacitance of activated carbon.Meanwhile,it is solving the shortcomings of transition metal layered hydroxides,such as poor conductivity,and easy accumulation and agglomeration between sheets.The specific research content is as follows:Nitrogen and oxygen-doped hierarchically porous carbons(NOHPCs)were successfully prepared using soybean as a carbon source based on the neutralization reaction concept.By controlling the pH value and carbonization temperature of the reaction system,an electrode material with excellent performance can be obtained.When the pH value of the reaction system is 11.5 and the carbonization temperature is 900℃,the obtained NOHPC-900-11.5 sample has the best performance.When assembling supercapacitors,in a three-electrode device with 1 M H2SO4 electrolyte,NOHPC-900-11.5 exhibited a high specific capacitance of 380 F g-1.In a two-electrode device with an electrolyte of 1 M Na2SO4,the symmetrical supercapacitor assembled based on NOHPC-900-11.5 still maintains high capacitance after 20,000 cycles,showing good cycle stability.It is worth noting that when using Tetraethylazanium tetrafluoroborate in propylene carbonate(TEATFB/PC)and 1-ethyl-3methylimidazolium bis[(trifluoromethyl)sulfonyl]imide(EMIMNTF2)as electrolytes,symmetric supercapacitors achieve high energy densities of 31.4 Wh kg-1 and 71.6 Wh kg-1.NiCoAl layered double hydroxide nanosheets were successfully prepared by a one-step solvothermal method.The shape and size of the obtained nanosheets can be adjusted by adjusting the solvothermal time and the molar concentration ratio of Ni2+/Co2+,and the conductivity and electrochemical activity of the NiCoAl layered double hydroxide can be improved by aluminum doping,thereby,the best performance electrode material is obtained.The results show that when the solvothermal time is 9 h and the molar concentration ratio of Ni2+/Co2+is 1:1,NiCoAl-LDHN-9 has the best morphology and the best electrochemical performance.When assembled into asymmetric supercapacitors with commercial activated carbon,it also exhibits excellent electrochemical performance in terms of energy density(35.9 Wh kg-1 at 225.8 W kg1)and cycle life(capacitance retention rate 87.1%after 10,000 cycles).NiCoAl-LDHN9 has the potential to become promising candidate electrode materials for highperformance supercapacitors. |
