Laser Regulation Of Graphene Self-assembled Film Structures And Their Application In Flexible Supercapacitors

As an important green energy storage device,micro flexible supercapacitor has the characteristics of small size,high power density and rapid charge and discharge,so it has a broad application prospect.Electrode materials play an important role in the performance of micro flexible supercapacitors.Graphene,as a unique carbon nanomaterial with two-dimensional structure,has good mechanical and electrochemical properties.The development of a simple,efficient and low-pollution process to reduce graphene oxide materials to form graphene film electrodes with porous structure is one of the important research directions to improve the performance of flexible supercapacitors.In this paper,graphene thin films were designed and modified by electrophoretic deposition,laser processing and laser cutting technology,and two-dimensional graphene thin films with high electrical conductivity,high flexibility and high electrochemical properties were obtained.It is used to prepare micro flexible supercapacitors to improve the electrochemical performance and stability of the devices.The research content of this paper is mainly divided into the following two aspects:（1）Using copper foil as anode and graphite rod as cathode,electrophoretic deposition was carried out in graphene oxide aqueous solution,and uniform and compact graphene oxide（GO）thin films with a thickness of～10μm were deposited on copper foil.The ultra-thin GO film was reduced by laser at 450 nm,so as to reduce the oxygen-containing functional groups of the sample,increase the porosity and graphitization of the graphene film,and improve the electrical conductivity and energy storage properties of the film.Then the thin film was cut by a 1064 nm fiber laser to form a finger electrode based on ultra-thin reduced graphene oxide（RGO）.At the same time,the sample at the edge of the cutting point was further activated to improve the conductivity and electrochemical performance.Ultra-thin flexible graphene finger supercapacitors were assembled by coating polydimethylsiloxane and selective etching with ferric chloride using H₃PO₄/PVA as gel electrolyte.Due to the reduction and hole-making effect of laser,the device can reach the volume specific capacity of 1.938 F cm^-3,and the power density and energy density can reach 4 m W cm^-3 and 0.172 m Wh cm^-3 respectively.（2）The surface of chopped carbon fiber（CF）was oxidized by solution oxidation method,and a hydrophilic GO layer was formed on its surface.The treated CF was mixed into the aqueous solution of graphene oxide to form a uniform mixed solution of CF-GO.After adding an appropriate amount of mixed solution to a specific container,due to the difference of specific gravity and deposition rate of CF and GO,graphene composite films with double-sided structure of GO enrichment layer and CF enrichment layer were formed.The flexible supercapacitor was assembled with H₃PO₄/PVA as gel electrolyte film and CF-GO composite film as electrode.With the help of the high conductivity and structural toughness of CF,the structural strength of the device is improved and the internal resistance of the device is reduced.At the same time,the CF enrichment layer is treated by laser method,and a large number of holes are formed on the surface of GO by the pore-making and reduction effect of laser treatment,the oxygen-containing functional groups on the surface of GO are removed,the conductivity of RGO film is improved,and the specific capacity and power density of the device are improved.The area specific capacitance of the optimized device can reach 102.4 m F cm^-2 at current density of 1.6 m A cm^-2.Compared with the pre-laser treatment and pure graphene devices,it increased by 7429% and 248% respectively.