Laser Manufacturing Of Micro-nano Structure Of Graphene Flexible Electrode And Its Application Research In Micro-supercapacitor

The rapid development of wearable and portable electronic devices towards“lightweight”and“miniaturization”has greatly stimulated the strong demand for high energy/power density,lightweight and portable and flexible energy storage devices in modern society.In recent years,with reports on the processing technology of laser-induced porous graphene flexible electrode from polyimide?PI?film,it is possible to manufacture flexible micro-nano energy storage devices on flexible substrates on a large scale with high efficiency and low cost.However,the porous graphene electrode processed by the traditional process is still faced with the bottleneck of low purity,poor wettability,and limited electrochemical performance.Exploring new manufacturing processes for high-efficiency and low-cost processing of graphene electrode with multi-scale micro-nano porous structure as well as pseudocapacitor material-deposited graphene electrode with micro-nano composite structure have become the key to solve the above problems.In view of this,this thesis takes a porous graphene-based in-plane micro-supercapacitor as the research object and conducts a systematic study on its internal design and electrode processing mechanism,electrode micro-nano porous or composite structure manufacturing,structural characterization,charge storage and flexible performance.The main contents of this thesis include:?1?Structure design of in-plane micro-supercapacitor and its electrode processing mechanismAccording to the visual design method,a new in-plane micro-supercapacitor and its interdigital electrode were proposed.Combined with the finite element simulation,the temperature field and its evolution law of the surface and interior of the radiation area with the change of laser power and scanning speed were revealed from the thermal analysis of PI film radiated from static and reciprocating dynamics.On this basis,the interaction mechanism between two types of laser and PI film was clarified from the product induction mechanism,product micro-morphology and its evolution law under different laser powers.?2?Manufacturing and characterization of micro-nano porous structure of graphene flexible electrodeBased on traditional KOH activation process,the activation mechanism of porous graphene and KOH in air ambient was analyzed,and the laser manufacturing process of micro-nano porous structure on the surface of porous graphene was explored.The surface microstructure,internal chemical structure and key physical properties of the graphene flexible electrode before and after manufacturing of micro-nano porous structure were systematically characterized,and the comprehensive effect of KOH activation concentration on the surface morphology,number of graphene layers,defect structure and chemical structure of graphene flexible electrode was studied.Studies reveal that medium concentrations of KOH are able to improve the quality,heteroatoms?nitrogen and oxygen?doping and wettability of porous graphene.Additionally,high concentrations of KOH contribute to the formation of carbon atomic defects and mesoporous structures.?3?Application research of flexible in-plane micro-supercapacitor based on graphene with micro-nano porous structureOn the basis of the manufacturing process of micro-nano porous structure of graphene,the overall performance of flexible in-plane micro-supercapacitor based on graphene with micro-nano porous structure was investigated.The charge storage and flexibility of the micro-supercapacitors were systematically characterized,and the feasibility of practical application was verified.The effect of KOH activation concentration on the cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy was studied.Results show that different concentrations of KOH-activated graphene micro-supercapacitors have good double layer capacitance characteristics and rate performance at low scan rates,and their areal capacitances increase with the increase of KOH concentration.In addition,the micro-supercapacitors also show excellent cycle stability,voltage and areal capacitance series-parallel consistency and flexibility.?4?Manufacturing and performance research of micro-nano composite structure of Fe₃O₄-deposited graphene electrodeThe interaction mechanism between laser and FePI film was mastered,and the laser manufacturing process ofnanoparticles-deposited porous graphene was explored.The surface and transmission micro-morphologies,chemical composition,and key physical properties of the porous graphene before and after the deposition ofnanoparticles were systematically characterized.Through capillary rise test analysis,the effects of various sample widths andnanoparticles deposition concentrations on the capillary performance ofgraphene electrode with micro-nano composite structure and capillary enhancing mechanism were investigated.Results show that the manufacturing of micro-nano composite structure of this electrode is conducive to the formation of mesoporous structure,the improvement of microscopic pore network and the substantial improvement of capillary performance.Additionally,the mentioned effects are more obvious with the increase ofdeposition concentration.?5?Application research of flexible in-plane hybrid micro-supercapacitor based on graphene with micro-nano composite structureOn the basis of the manufacturing process of micro-nano composite structure of graphene,the effect of variousdeposition concentrations on the performance of electrode and in-plane hybrid micro-supercapacitor was further studied.The intercalated pseudocapacitance behavior of the electrode was analyzed and the influence of different deposition concentrations and scan rates on its charge storage contribution rate were revealed.The charge storage and flexibility of the hybrid micro-supercapacitor were systematically characterized,and the effects ofnanoparticle concentration on the cyclic voltammetry,galvanostatic charge-discharge and series-parallel as well as the mechanism of composite structure were fully researched.Results show that the composite electrode is dominated by diffusion-controlled intercalation effect,and the contribution rate decreases with the increase of scan rate.The reversibility of the hybrid micro-supercapacitor decreases with the increase of deposition concentration and scan rate/current density,and the charge storage behavior of the micro-supercapacitor changes from surface capacitance to intercalation with the increase of deposition concentration.In addition,the hybrid micro-supercapacitor also shows good cycle stability and flexibility with the highest areal energy density of 60.20?Wh/cm²,which is better than the most reported in-plane hybrid micro-supercapacitors.