Construction And Supercapacitor Performance Of Pomegranate-Like Porous Carbon Micro Spheres

Environmental issues and energy development are two major challenges facing the world today.The problem of environmental pollution has been widely concerned in recent years.The main pollution source is the combustion of fossil energy.Therefore,developing efficient and clean energy is an effective way to solve energy shortages and environmental pollution.As an emerging energy storage device,supercapacitor can achieve fast charge and discharge,has the ability to input or output power with high power and cycle stability of more than 10,000 cycles.In view of the large power density of supercapacitors,they offer significant advantages in vehicle traction power and fast start energy.However,due to its low energy density,it cannot be used as the main power source for electric vehicles.Therefore,the development of supercapacitors with high energy density has become a research hotspot.The electrode material is the core of the supercapacitor.Among them,carbon material is the main electrode material of electric double layer supercapacitor.Its excellent cycle performance,safety and stability make it the first choice for commercial supercapacitors.However,its mass specific capacity and volume specific capacity are relatively low,which greatly limits the increase in energy density.Therefore,it is particularly important to design and prepare carbon materials with high mass specific capacity and volume specific capacity.Based on the above ideas,the pomegranate-like porous carbon spheres(PCS)with high tap density were synthesized by spray drying method.A series of characterization methods were used to characterize the microstructure and chemical structure of the materials,and the electrochemical properties of the materials were tested as supercapacitor electrode materials.The main research results of this paper as follows:(1)Phenolic resin spheres were obtained by rapid polymerization using 3-aminophenol and formaldehyde solution as raw materials.The organic ball has uniform size and good dispersibility.The organic particles were dispersed in deionized water,and by spray drying,resin microspheres having a pomegranate-like structure were obtained in one step.The function of the amino group in 3-aminophenol was explored.On the one hand,with amino group as a catalyst,the phenolic reaction was promoted rapidly and the introduction of ammonia was avoided,and on the other hand,the in-situ doping of nitrogen was achieved.PCS with high specific surface area and N,O co-doping were prepared by further carbonization and activation steps.(2)The microstructure and chemical structure of the obtained porous carbon materials were characterized by XRD,XPS,SEM,TEM and infrared spectroscopy.The presence of a large number of aromatic hydrocarbon functional groups and the bonding of carbon-carbon double bonds in the infrared spectrum demonstrates that the pomegranate-like resin microspheres obtained by spray drying have a more stable structure.The closest packing of nano-carbon spheres was observed from the SEM,which effectively improved the tap density of the porous carbon material.(3)The material was prepared as an electrode sheet and tested for electrochemical performance in a supercapacitor.PCS exhibit excellent rate performance and high specific capacity.As the loading of the active material increased to the commercial grade(11 mg/cm~2),there was no significant decrease in specific capacitance.The capacity is not attenuated after 10000 cycles,showing excellent commercial potential.Supercapacitors with PCS as active materials can achieve a power output of up to 12.5kW/kg.PCS have the most balanced mass specific capacity and volume specific capacity compared to the specific capacitance in other literatures.The structural advantage of PCS is the orderly accumulation of carbon nanospheres.On the one hand,the problem of disordered agglomeration common to nano-materials is avoided,and on the other hand,the amount of binder required is reduced.Through comparative experiments,we found that excessive binders would occupy part of the active sites,hinder ion migration channels,and significantly reduce the specific capacitance of the active material.The most intuitive performance is the increase of the tap density,which leads to an increase in volumetric capacity.