Preparation Of Phenolic Resin-Based Porous Caebon For Application In Supercapacitors

Electric double-layer capacitors?EDLCs?,as energy storage devices between battery and conventional electrostatic capacitor,have attracted increasing interests due to their rapid charge-discharge efficiency,high power density,outstanding cycling stability and environmental friendliness.EDLCs store energy by the accumulation of charges at the electrode/electrolyte double layer interfaces.Carbon materials are the most widely used electrodes for EDLCs.Amongst them,porous carbon materials are very popular as electrode materials for supercapacitors.Phenolic resin is a traditional polymer material in daily life.Phenolic resin is the most popularly used precursor for porous carbon electrode material due to its high char yield,low cost and controllable pore size.However,phenolic resin-based porous carbon electrode materials suffer from poor electrical conductivity and low specific surface area.In this paper,three dimensional graphene as the modification filler was incorporated to phenolic resin to prepare three dimensional graphene/phenolic resin conductive composite with good mechanical properties.And the phenolic resin composites were used as carbonaceous precursors to prepare porous carbon electrode materials.In addition,hydrothermal synthesis of phenolic resin by different methods was used to prepare porous carbon for supercapacitors.Three dimensional?3D?graphene/phenolic resin?3DGP?composites were synthesized via in-situ polymerization in graphene hydrogels.The prepared composite can retain the complete 3D network structure to achieve good dispersion of graphene sheets forming 3D conducting network in polymer.The mechanical and electrical properties were measured,and the results showed that the composite possessed good electrical conductivity and compressive property.The compressive strength of the composite increased by 14.24%to 441.11 MPa compared with that of pure phenolic resin.And 3D graphene/phenolic resin-based porous carbon composite electrode materials with enhanced conductivity were prepared by carbonizing 3DGP composites and potassium hydroxide activation.The prepared porous carbon composite electrode materials exhibited an improved graphitization degree and enhanced conductivity by introducing 3D graphene.The electrochemical measures of the obtained 3D graphene/phenolic resin-based porous carbon composite electrode materials were performed.The gravimetric specific capacitance was up to 215.3 F·g^-1 at 0.1 A·g^-1.The capacity retention was 96.6%after5000 cycles at a scan rate of 50 mV·s^-1.Porous carbon electrode materials were prepared by carbonizing phenolic resin synthesized by hydrothermal treatment.Pomegranate-like porous carbon electrode materials were synthesized by carbonizing phenolic resin prepared by adding phenolic resin monomer mixture into KOH aqueous solution and hydrothermal treatment.The results indicated that the obtained porous carbon electrode material was microporous material with specific surface area as high as 2199.9 m²·g^-1.The porous activated carbon showed a high specific capacitance of 341.3 F·g^-11 at 0.1 A·g^-1,good rate capability of 71.0%in the range of 0.1–5 A·g^-11 and excellent cycling stability(only 3.9%loss in specific capacitance after 5000 cycles at a scan rate of 50 mV·s^-1)as a supercapacitor electrode material.Further measurements were conducted in a two electrode symmetric cell configuration.The energy densities of the assembled symmetrical supercapacitor were49.6 W·kg^-1 and 1.8 kW·kg^-11 with the corresponding power densities of 17.0 Wh·kg^-1 and8.5 Wh·kg^-1,respectively.Further work,phenolic resin spheres were synthesized by a hydrothermal route,using nanodiamonds?5 nm?as nucleation sites,which is beneficial to promote non-spontaneous nucleation,to make the phenolic resin spheres small.And the phenolic resin spheres were used as carbonaceous precursors to prepare carbon spheres by carbonization under vacuum at 800?C.The results showed that the phenolic resin spheres with controlled size were synthesized successfully.And the carbon spheres with controlled size were further prepared.The electrochemical measures of the obtained carbon spheres electrode materials were performed.The carbon spheres prepared by non-spontaneous nucleation showed a high specific capacitance at 2 mV·s^-1,which is twice as much as that of the carbon spheres prepared by spontaneous nucleation.