Research On Femtosecond Laser Fabrication Technology For Graphene Oxide Based Micro Energy Storage Devices

With the rapid development of semiconductor industry and increasing upgrade of advanced manufacture,the fabrication of the electric devices with miniaturization,flexibility and high integration has become an important research field.To obtain the good compatibility of future micro electric devices,the demand of electrochemical performance,miniaturization and integration for present energy storage devices will be put up.For graphene based two dimensional materials,owing to the specific energy band structure and superior physical and chemical characteristics,it will have a huge application prospect in the field of energy storage,photovoltaic conversion and signal collection.Due to graphene oxide as a derivative of graphene,via the method of laser irradiation,it can fastly reduce graphene oxide and obtain the reduced graphene oxide with surface micro-nano structure.Comparing with other machining methods,femtosecond laser can easily realize the modulation of physicochemical property and surface functionalization,by the ultrahigh peak intensity and ultrafast pulse time.In this paper,we put up a method of femtosecond laser induced graphene oxide surface micro-nano structure and ultrafast reduction.The theory and experiment study of femtosecond laser induced graphene oxide with surface micro-nano structure were carried out.The micro energy storage devices with flexibility and high integration was fabricated,electrochemical performance of devices was tested.Main work are as follows:According to optical nonlinear obsorption characteristics of graphene oxide,the theoretical model of photo-induced free electron of graphene oxide by femtosecond laser was put up.The electric field distribution characteristic of graphene oxide of femtosecond laser irradiated region was analyzed.The formation mechanism of surface plasmon of graphene oxide was studied.Combination with the electromagnetic field equation and dielectric function theory,the periodic characteristic of surface plasmon induced by the interaction of electric field of femtosecond laser at graphene oxide with random surface characteristic was researched.Based on the two temperature model with coupling of electron and photon,the formation of graphene oxide nanostructure under the interaction of periodic oscillation energy field was analyzed.The accuracy of theoretical model was verified by the results of experiment.To micro-nano structure morphology characteristic and ultrafast reduction of graphene oxide by the machining of femtosecond laser,the process experiment was carried out.The influence rule of laser intensity and pulse number for change of micro-nano structure morphology was analyzed.To obtain the ablation threshold of graphene oxide,the ablation characteristic of graphene oxide by the irradiation of laser with the wavelength of 1030 nm and 257 nm was studied.The coupling interation of micro-nano structure and incident laser electric field was simulated,the change mechanism of periodic micro-nano structure morphology was revealed.Combination with the phase characteristics,chemical elements and conductive performance of graphene oxide,the influence of laser intensity on reduction characteristic of graphene oxide was researched,the relationship of formation of micro-nano structure and ultrafast reduction was analyzed.Based on the micro-machining of femtosecond laser,the optimized processing parameters of graphene oxide electrode was obtained,the planar interdigital graphene oxide micro supercapacitors with flexibility was constructed.The influence rule of electrode shapes and the interdigital interspace for the electrochemical performance of electrodes was analyzed.According to double electric layer and Nernst-Planck equation,the influence of electrode surface morphology and porousness for the interface electron distribution and dynamical process of electrodes were researched.To measurement the electrochemical performance of flexibile graphene oxide micro supercapacitors with the interdigital interspace of 10?m by the femtosecond laser machining,the rate capability and cycle stability of micro supercapacitors were calculated and analyzed.The preparation technology of graphene oxide based flexible energy storage device was studied.Based on the advantage of femtosecond laser micro machining,the processing method of reduced graphene oxide/ruthenium oxide micro supercapacitors by femtosecond laser processing was explored,the electrochemical reaction mechanism of faradic pseudocapacitance electrodes was analyzed.Based on the high volume capacitance of MXene(Ti₃C₂T_x),the morphology and phase change characterisitc of MXene by femtosecond laser micro machining were researched,the volume capacity and energy density of MXene micro supercapacitors were tested.The asymmetric micro supercapacitors of reduced graphene oxide/ruthenium oxide and MXene were constructed,the electrode material and working voltage range were matched and choosed,the electrochemical performance of asymmetric micro supercapacitors were studied by the cyclic voltammetry curves and galvanostatic discharge-charge profiles.The process strategy of flexible double-side micro supercapacitors array by femtosecond laser machining was put forward,the flexible spiral electrodes array with‘flower petal'shape was designed to come true the modulation of voltage output and capacitance.