| Energy strategy is an important subject of sustainable economic development in China,and energy storage devices are one of the important roles in energy strategy.As a new type of super material,graphene has very broad application prospects in the fields of new energy,portable electronics and wearable devices because of its many novel physical and chemical properties.In this theses,a self-made laser engraving machine is used to prepare graphene supercapacitors using laser direct writing method based on two different flexible substrates.The main research contents include the following aspects:（1）Design and development of self-made laser engraving machine for the preparation of graphene electrodes.The hardware core of the self-made laser engraving machine is composed of three parts:the Arduino UNO single chip microcomputer,the stepper components obtained by disassembling the used optical drive and the laser head.The software part takes the open source project GRBL as the core,and uses it to generate standard g-codes to control the laser engraving machine to complete various conventional motion paths such as points,arcs,circles,and spirals.After testing,the precision of the self-made laser engraving machine reaches 0.3mm,which can achieve high precision,high efficiency,flexible and controllable preparation of graphene electrodes.（2）Based on the graphene oxide（GO）film as the substrate material,a patterned electrode made of reduced graphene is prepared by laser direct writing on GO film by the self-made laser engraving machine.The PVA/H2SO4 gel electrolyte is used to provide conductive ions,and then the patterned graphene electrode is packaged into a supercapacitor.SEM,TEM and Raman spectroscopy are used to perform physical characterizations of the prepared graphene electrode material.The characterization results show that the electrode material is composed of a multi-layer graphene nanosheet structure.The prepared graphene supercapacitors are further investigated by cyclic voltammetry,galvanostatic charge discharge,AC impedance analysis and cycle life.The results show that the cyclic voltammetry curve shows a regular rectangular curve with an area specific capacitance of 2.03 m F cm-2 at a low scan rate of 5 m V s-1,and the coulomb efficiency remains at 92%or more after 10,000 times of long-term life testing,showing excellent cycle stability.（3）Based on a commercial polyimide（PI）film as the substrate material,a laser-induced graphene（LIG）electrode is fabricated by laser direct writing technology.The LIG electrode is evenly coated with PVA/H2SO4 gel electrolyte,and then packaged to form a graphene supercapacitor.SEM,TEM,and Raman spectroscopy are used to investigate the electrode morphology and pore size of LIG prepared based on PI thin films,which show LIG has randomly stacked graphene nanosheet structure.And then,cyclic voltammetry,galvanostatic charge discharge,AC impedance analysis and cycle life have been characterized the electrochemical performances of LIG supercapacitors.It has been found that the area specific capacitance of LIG supercapacitor reaches 2.47m F cm-2 at a low scan rate of 5 m V s-1,and the coulomb efficiency still remained at about 90%of the initial value after 10,000 charge and discharge lifespans,which shows LIG supercapacitor has good electrochemical performance.Using self-made laser engraving machine to directly write graphene electrodes on flexible substrates and assembling them into graphene supercapacitors bring new ideas and exploration directions for the preparation processes of new generation micro supercapacitors and other types of micro-nano devices.This new non-polluting,high-precision manufacturing process has improved in terms of productivity and efficiency compared with the traditional manufacturing process,and has truly realized a large batch,large area,and controllable preparation of various micro-nano devices in a short time.In addition,the flexible device preparation method can integrate micro supercapacitors with MEMS and CMOS in microcircuits,providing new thinking directions for energy supply in next-generation integrated circuits.Micro supercapacitors are built on flexible substrates,and their bending characteristics also provide a flexible solution to the energy supply problem in wearable devices in the future. |
