| Supercapacitors have received great attention due to their unique advantages,such as high power density,long service life,wide operating temperature range,and no memory effect,etc.Electrode materials are one of the key factors affecting the performance of supercapacitors.Carbon materials with various morphologies and microstructures are the focus of current research.In this paper,we investigate the effective preparation methods and synthesis of porous carbon materials with different morphological structures to enhance the performance of supercapacitors.The main studies are as follows:1)Using phenol and formaldehyde as carbon sources,monodisperse phenol formaldehyde resin polymer nanospheres were prepared as cores by low-concentration hydrothermal polymerization,and the surface structure was modulated by introducing melamine-formaldehyde/silica composites on their surfaces.Porous carbon spheres with different degrees of surface folds（FCS）were prepared by adjusting the addition of ethyl orthosilicate.The folded structure has a great influence on the supercapacitor performance,and FCS-0.4 has a capacitance value of 207 F·g-1 at 0.5 A·g-1 in the three-electrode test,which is much larger than that of FCS-0(91.5 F·g-1)without the introduction of the folded structure.In addition,81%of the initial performance is maintained after 10,000charge/discharge cycles in the two-electrode system.The pleated structure plays an important role in regulating the material morphology and improving the electrochemical properties,which provides a good idea for the preparation of functional carbon materials with other structures.2)The analysis based on 1)concludes that the solid structure severely limits the performance of the supercapacitor.Therefore,in this work,a soft-template method and m-aminophenol resin was chosen as the carbon source to synthesize mesoporous cavity carbon spheres by in situ doping with nitrogen elements.An oil-in-water nanoemulsion system formed by nonionic surfactant F127 and glyceryl trioleate was used as the soft template,and ethyl orthosilicate was used to promote the uniform polymerization and growth of the resin on the soft template surface,and to assist in regulating the structure of the material surface.After carbonization,nitrogen-doped cavity carbon nanospheres（NCCS）were obtained.Thanks to the cavity structure and nitrogen doping properties,the prepared mesoporous carbon nanospheres NCCS-1.4 have a high specific capacitance of 268.5 F·g-1 at a current density of 0.5 A·g-1 in the three-electrode system.In addition,the cycling stability test results in the symmetrical electrode system showed that the material properties were maintained at 93.2%after 10,000 charge/discharge cycles at 5 A·g-1.3)Based on the previous work,we continued to explore other methods for hollow structure preparation.Nitrogen-doped hollow carbon nanospheres（NHCS）were synthesized using a self-sacrificing template method with Polystyrene/polyacrylonitrile（PSPAN）composite spheres as the template,dopamine as the carbon and nitrogen source,and silica shell as the structural immobilization framework.Due to its hollow structure,abundant mesopores and nitrogen doping properties,NHCS-50 has a high specific capacitance of 262 F·g-1 at a current density of 0.5 A·g-1 in the three-electrode system.After10,000 cycles of charge/discharge testing in the two-electrode system,the material can still maintain 93.5%of the initial performance with excellent stability.This result is expected to provide a new idea for the preparation of mesoporous hollow carbon nanospheres with high specific surface area. |
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