Research On The Controllable Preparation Of Porous Carbon Microspheres And Its Supercapacitor Performance

Supercapacitors which are considered to be a promising energy storage equipment have great market potentials because of higher power energy,longer cycle stability and faster charging and discharging ability.Electrode material is one of the important factors to decide the supercapacitor performance.Porous carbon materials with hierarchical porous structure are of current great interest and high degree of attention for scientific researcher on account of their unique features,such high specific surface area,uniform and tunable pore size,good conductivity and stability.In order to prepare the novel porous carbon materials for supercapacitors,we explored a new and simple process to prepare the porous carbon spheres and investigated the electrochemical performance in alkaline electrolyte and neutral electrolyte,respectively.In this research,porous carbon spheres were produced based on the use of the starch as carbon precursor by means of these pretreatments using Potassium aluminum sulfate solution and calcium carbonate,the influence factors in the synthesis of hollow carbon microspheres were studied,mainly including the carbonizing temperatures and the concentrations of calcium chloride solution.The microstructure,pore structure and surface functional groups of the carbon materials were characterized by Scanning Eletron Microscope(SEM),X-ray Diffraction(XRD),X-ray Photoelectron Spectroscopy(XPS)and N2 adsorption/desorption isotherms(BET).The electrochemical performances were measured by cyclic voltammetry,constant current charge and discharge and circulation performance test.The effects of structure properties to the supercapacitor performances were analysed by combining the electrochemical testing results and the microstructure and surface functional groups of the carbon materials.The results showed that the nitrogen-doped hollow mesoporous carbon spheres can be prepared with a good dispersion and a controllable particle size distribution by one step carbonization and nitrating method.The surface area was 1179.0 m2 g-1,the specific capacitance was 300 F g-1 when the current density was 0.5 A g-1 in 6 M potassium hydroxide solution,when 20 A g-1 was 228 F g-1,the capacity retention ratio was 76%;nevertheless,the specific capacitance was 183.6 F g-1 when the current density was 1 A g-1 in 1 M neutral sodium sulfate aqueous electrolyte,when 1 A g-1 was 123 F g-1,the capacity retention ratio was 66.9%.The potassium hydroxide solution is a kind of corrosive liquid,especially at high concentration,this limits its application in commercial supercapacitors.The results showed that this material owned higher specific capacitance in 1 M neutral sodium sulfate aqueous electrolyte,moreover,neutral electrolyte costed lower and was friendly to the environment.