Study On Graphene Prepared By Electrochemical Exfoliation For Flexible Supercapacitor

The rapid development of flexible and wearable electronic products promotes the strong demand for miniaturized and bendable energy storage devices.Supercapacitors have attracted wide attention as a kind of lightweight,thin,safe and high-performance energy storage devices,especially flexible planar micro-supercapacitors with graphene as electrode material.Although remarkable progress has been made in the design and development of graphene-based flexible planar micro-supercapacitors in recent years,they still face many difficulties.For example,the simple,fast and low-cost preparation methods of high-quality graphene,micro fabrication technology of graphene electrodes,and selection of flexible substrates.Based on the above problems,this dissertation takes the high-quality electrochemical exfoliated graphene as the research object,adopts a novel microfabrication process to prepare paper-based flexible planar integrated micro-supercapacitors and carries out in-depth research on it,mainly including the following contents:?1?High quality graphene is obtained from graphite papers by electrochemical exfoliation in concentrated sulfuric acid and ammonium sulfate electrolyte solution.In order to meet the requirements of cheap and environmentally friendly substrates,renewable and porous papers are used as flexible substrates for supercapacitors.Inspired by the photosensitive seal technology in daily application,a novel and ingenious photosensitive seal assisted impression technology is developed to form planar interdigital electrodes patterns on the flexible paper substrate,and then the paper-based graphene interdigital electrodes are made by self-deposition of graphene.Finally,the whole solid state flexible planar micro-supercapacitor is encapsulated with gel electrolyte.The experimental results show that the paper-based flexible supercapacitor has the high specific capacitance of 4.02mF·cm^-2,the power density of 0.43mW·cm^-2and the energy density of 0.52?Wh·cm^-2.It also shows good flexibility and stable electrochemical performance under bending state,and has excellent cycle life.?2?High quality graphene can also be rapidly prepared by electrochemical exfoliation in concentrated sulfuric acid and dilute sulfuric acid solution.Based on the photosensitive assisted impression technology,a simpler and low-cost laser engraving assisted mask technology is proposed.The technique is based on self-deposited electrochemical exfoliation of graphene to produce flexible paper-based planar supercapacitors.The experimental results show that the flexible paper-based planar graphene micro-supercapacitor prepared by this technology has excellent electrochemical performance,with a significant area specific capacitance of 3.1m F·cm^-2,a power density of 0.38mW·cm^-2,and an energy density of 0.5?Wh·cm^-2.The exciting thing is that even after 10,000 cycles,the capacitance only loses 4.2%.Under different bending conditions,paper-based graphene flexible supercapacitor has almost no significant performance loss.In addition,the effects of voltage scanning rate,current density,interdigitated electrode spacing and electrode thickness on the capacitance are further investigated.The paper-based flexible supercapacitors designed in this dissertation with electrochemical exfoliated graphene as electrode material have good electrochemical stability,super long cycle life and excellent mechanical flexibility,which have great potential for integration into wearable and portable energy storage products.More importantly,the photosensitive assisted impression technology and laser engraving assisted mask technology developed in this dissertation have the characteristics of practicality,safety,and low cost,paving the way for large-scale production of paper-based electrodes and other microstructures with complex patterns.