Preparation And Research On The Supercapacitive Properties Of Graphene- Based All Carbon 3D Structure

Compared with traditional battery,the advantages of supercapacitor in cycle life,power density and environmental protection have caused widespread concern and research,but on the other hand,the energy density of supercapacitors is low,which limits its further development in the application,and electrode materials are particularly critical.Graphene has received widespread attention since its inception.In the field of electrochemical energy storage,graphene also has a theoretical specific capacitance much higher than other carbon materials,reaching 550 F/g,so graphene is considered to replace traditional carbon materials for supercapacitors,but on the other hand,graphene itself has a problem of extremely easy stacking,which leads to a reduction in its specific surface area,so the specific capacitance of graphene is currently lower than 200 F/g,based on this,how to effectively reduce the stacking of graphene itself becomes the key to the problem.The main content of this paper is also based on this scientific issue,the specific content is as follows:The main idea of this paper is to further reduce the stacking degree of graphene by introducing carbon nanotubes and carbon onions based on synthetic porous graphene hydrogel.The nanopores on the surface of porous graphene can shorten the ion transport path,and the interconnection between the carbon nanotubes and the graphene sheets can construct a conductive network to reduce the internal resistance of the material,and the introduction of the carbon onion allows the electrolyte to be stored inside the material,thereby improving the rate performance of the material.Therefore,0D carbon onion,1D carbon nanotubes,2D porous graphene oxide self-assembled to the 3D all carbon structure is considered to be a suitable electrode material.By optimizing the concentration of carbon nanotubes and carbon onions,the electrochemical performance of the all-carbon 3D structure electrode is optimal when the concentrations of carbon nanotubes and carbon onions are 0.05 mg/mL and 0.03 mg/mL,respectively.Under the three-electrode test conditions,when the current density is 0.5 A/g,the capacitance of the electrode is as high as 238.1 F/g.Under the two-electrode test condition,the specific capacitance can still be maintained at 229.0 F/g at a current density of 0.5 A/g.At a current density of 10 A/g,the device's capacitance retention reached 80.8%,while the assembled symmetrical device exhibited excellent cycle performance,and the capacitance retention was 93%after 10,000 cycles.According to the energy density of the device,the electrochemical properties of the electrode material under the organic electrolyte were explored.It was found that when the EMIMBF₄ diluted with acetonitrile was used as the electrolyte,the voltage window of the device could be expanded to 2 V,in order to further improve the specific capacitance under the organic electrolyte,we use EMIMBF₄ diluted in acetonitrile as the base electrolyte.By introducing p-phenylenediamine as an additive to increase the specific capacitance of the device,it was found that when the doping amount of p-phenylenediamine is 0.12 M,the device exhibits the highest capacitance.At a current density of 0.5 A/g,the capacitance is only 11%lower than the specific capacitance of the aqueous electrolyte,reaching 202.8 F/g.The device exhibits a higher energy density under organic electrolytes,reaching 28.2 Wh/kg,which is significantly higher than the energy density of the device under aqueous electrolyte?5.1 Wh/kg?.