Study Of Porous Carbon Foams For Supercapacitor

Energy crisis and environmental pollution push the development of new energy storage devices.Supercapacitors have become a research hotspot in the electrochemical field due to the advantages of high specific capacitance values,fast charge/discharge rate,long cycle stability and environmental friendliness.The electrode material is a key factor in determining the performance of a supercapacitor.In particular,self-supporting electrodes have shown great advantages in energy storage devices in recent years.Melamine sponge is a three-dimensional network structure resin polymer with low-density,high-porosity,low cost and environmental friendliness,which is very suitable for preparing self-supporting electrode materials.In this paper,melamine sponge is used as the self-supporting electrode,and the structure and composition of the carbon sponges are optimized by adjusting different parameters to improve the capacitance performance and practical application.There are three parts in our work:1.Preparation of porous carbon sponges by high temperature pyrolysis for supercapacitor electrodesNitrogen/oxygen co-doped carbons sponges（NOCSs）prepared from carbonizedmelamine sponges has the advantages of light weight,large porosity,large surface area and incorporation of heteroatoms such as nitrogen and oxygen elements,which can can generate pseudocapacitance through reversible redox reactions on the basis of electric double-layer capacitance.The carbon sponges can be directly applied as the supercapacitor electrodes without any additives and binders.The influence of carbonization temperatures from 650 to 950°C on the heteroatom（N and O）content,surface area,graphitization degree,and capacitor performance of carbon sponges are systematically investigated,and it is found that NOCS-850 delivers a better overall capacitive properties for balanced heteroatom content,surface area,and graphitization degree.Therefore,NOCS-850 shows great advantages in terms of specific capacitance and cycle stability.A red light-emitting diode can be successfully lighted by three connected all-solid-statesupercapacitorsofNOCS-850,illustratingits potential application inenergy storage field.2.Preparation of porous carbon sponges by chemical activation for supercapacitor electrodesChemical activation plays an important role in improving the capacitance performance of carbon materials.The characteristics of low density and high-porosity,enabling chemical activator easily and thoroughly permeating all parts of melamine sponges during the impregnation process.We provide a facile chemical activation method to prepare NOCSs with melamine sponges and KOH as the carbon precursor and activating agent,respectively.Regulating the structure and composition of carbon sponges by controlling the mass ratio of melamine sponges to KOH.After KOH activation and pyrolysis strategy,the prepared nitrogen oxygen co-doped carbon sponges basically keep the original structure of melamine sponges and show hierarchically pore structures,which offers a continuous pathway for electron transport and ensure the rate capability.The electrochemical characterizations demonstrated that when the mass ratio of melamine sponge to KOH is 1:7,the prepared NOCS-3 shows the advantages of high conductivity,large specific surface area and moderate amount of nitrogen and oxygen active groups,which increases the contributions of electric double layer capacitance and pseudocapacitance,further improving rate performance and potential practical applicationon the basis of experiment 1.3.Preparation of flexible carbon sponges by loading ZIF-8 on melamine sponges for flexible supercapacitor electrodesCarbon sponges as electrode materials can not only make a positive contribution to capacitive performance,but also provide abundant loading sites for supporting active species due to the three-dimensional porous structure and large specific surface area.According to the previous research,the content of pseudocapacitance active groups of carbon sponges is relatively low,which limits the improvement of pseudocapacitance and rate performance.We synthesized ZIF-8 by hydrothermal method with Zn Cl₂ and 2-methyl imidazole as raw materials,loaded on melamine sponge and then carbonized at 850°C.The prepared carbon foam composites have a relatively high content of nitrogen-containing active groups and good flexibility,which can not only improve the specific capacitance value,but also effectively improve the cycle life in the application of supercapacitor as electrode materials.