Research On The Performance Of Planar On-chip Micro-supercapacitors Based On Graphene And Carbon Nanotube Composite Electrodes

The development of micro-electronic equipment promotes the research of micro-energy storage devices.In the development of high-performance energy storage solutions,micro-supercapacitors are a technology worth exploring.The performance of micro-supercapacitors is mainly determined by electrode materials.Among them,carbon-based electrode materials have been widely studied.Graphene has become an ideal material for supercapacitors due to its high specific surface area.Graphene quantum dots are a kind of particle size smaller than the 10 nm zero-dimensional carbon material not only has a high specific surface area,but also has rich edge defects and more active sites,which greatly improves the electron mobility.The addition of nitrogen and oxygen to the graphene quantum dots will also improve the ion adsorption capacity and surface hydrophilicity of the material,so the nitrogen and oxygen co-doped graphene quantum dots become another better choice for electrode materials.However,they are stacked and agglomerated due to van der Waals force during the drying process of forming a thin film,resulting in a smaller available specific surface area and a decrease in the performance of the capacitor.As a carbon-based electrode material,carbon nanotubes have a lower surface area compared with graphene,which has always been a bottleneck in research.If carbon nanotubes are compounded into graphene,not only the stacking and agglomeration problems be solved,the added carbon nanotubes will also can be used as a supplementary electrode to improve the capacitance characteristics.The surface of carbon nanotubes can also quickly transfer and transmit electrons to improve the power characteristics of capacitors.Finally,carbon nanotubes have excellent mechanical properties and high toughness.After adding carbon nanotubes,supercapacitors and flexible PET substrates can be improved.It is possible to prepare capacitors on flexible PET substrates.In general,carbon nanotubes act as Spacer support,conduction and activation electrodes,and cooperate with graphene to improve the performance of micro-supercapacitors.Through theoretical analysis and experimental exploration,the final experimental plan was to prepared micro-supercapacitors at a ratio of 5:1 and 10:1according to reduced graphene oxide and carbon nanotubes,graphene quantum dots and carbon nanotubes respectively,and then prepared reduced graphene oxide,graphene quantum dots and carbon nanotubes substrates for comparative experiments,and then compared the electrode widths and the gaps are set to 50μm/50μm and 100μm/100μm width for comparison,and finally transferred to a flexible PET substrate.In this paper,by improving the liquid-air interface self-assembly process and photolithography process to prepared planar on-chip micro-supercapacitors,the electrode films are characterized,including atomic force microscopy,transmission electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and Raman spectroscopy.Through the electrochemical workstation to test the electrochemical performance of the micro-supercapacitor,including cyclic voltammetry test,constant current charge and discharge test,AC impedance test and cycle stability test.The film characterization analysis showed that the electrode film formed a film with good continuity and a large area thickness of about 10 nm.The electrochemical test analysis results showed that the most superior performance of the supercapacitor parameter in the above experimental program is the ratio of electrode width to gap of 50μm/50μm,graphene quantum dots:carbon nanotubes is a 10:1 ratio compound,its energy density can reach 30n Wh cm^-2,power density 0.3 W cm^-2,surface capacitance reach 216μF cm^-2.It has high cycle stability.It still has a capacitance retention rate of 95.4%under 10,000cycles of charging and discharging at a sweep rate of 5000 V s^-1.