Research Of Sulfur Doped Graphene Flexible Electrode Materials And Their Performance Based Supercapacitors

As a new energy storage device,supercapacitors have been widely concerned by researchers due to high power density,long cycle life,fast charge and discharge speed,and environmental friendliness.The demand for flexible wearable electronic devices with aesthetic appeal and versatility has stimulated the rapid development of flexible supercapacitors with high electrochemical performance and mechanical flexibility.Since electrode materials are one of the key factors that affect the energy storage performance of flexible supercapacitors,the development of flexible electrode materials with high specific capacitance has become an important research direction.The energy storage performance and practical application of flexible electrode materials are affected by other factors such as the preparation method of the electrode material,its structure,and the thickness of the electrode material.In this thesis,from the method of preparing high specific capacitance sulfur-doped graphene-based electrode materials,the influencing factors of sulfur-doped graphene electrode materials with different structures on the electrochemical performance were investigated.Possibility of application of hetero graphene electrode materials in wearable electronic devices.The research content of this thesis mainly includes the following three parts:?1?This chapter uses a simple method to dope large-sized heteroatoms?S?into graphene:graphene oxide film is used as a precursor,based on in-situ thermal reduction to prepare sulfur-doped graphene film.The decomposed gas product of SO₂enables the doping and reduction of graphene oxide to proceed simultaneously.The prepared flexible S-doped graphene film?SGF?has a fluffy fold structure,and the effect of the amount of reducing agent on the performance is discussed.When the mass ratio of reducing agent Na HSO₃ to graphene oxide is 10:1,the SGF electrode material specific capacitance can reach 232.8 F g^-1.?2?In this chapter,the template method is used to prepare sulfur-doped porous graphene foam.The self-assembly properties of graphene oxide are used to prepare the porous graphene foam using the template method.Using foamed nickel as a template,the number of graphene oxide solution depositions was controlled to achieve a controlled amount.Based on the in-situ thermal reduction method,foamed nickel-sulfur doped porous graphene was prepared,and the foamed nickel template was removed by HCl to obtain Sulfur-doped porous graphene foam.The prepared sulfur-doped porous graphene foam has a macro-porous and microporous structure,and the surface has a regular hexagonal fold structure.We also discussed the effect of the amount of reducing agent on the electrochemical performance of S-doped porous graphene foam?S-PGF?.Among them,as the amount of reducing agent increases,the specific capacitance of S-PGF shows a tendency of increasing first and then decreasing.When the mass ratio of reducing agent Na HSO₃ to graphene oxide is 20:1,the specific capacitance reaches 241.6 F g^-1 when the mass of a single electrode is 2.3 mg cm^-2.?3?In order to further study the effect of area density and thickness of SGF electrode materials on the electrochemical performance of flexible supercapacitors,SGF with different thickness and area density were prepared.With the increase of area density and thickness,the area specific capacitance has an approximately proportional relationship with the area density and thickness of SGF.When the area density of SGF reaches 7.9 mg cm^-2,its area is at a current density of 1 m A cm^-2.The specific capacitance reaches 672.5 m F cm^-2.With a single-electrode area density of 4 mg cm^-2 and a current density of 2 m A cm^-2,after 10,000 cycles,the specific capacity retention rate was 94.1%.The SGF as the electrode material,a symmetrical SGF//SGF all-solid-state supercapacitor device was assembled,and its electrochemical performance was tested.The results showed that the power density was 12.17 Wh kg^-1 at a power density of 499.85 W kg^-1.The all-solid-state flexible device is bent at any angle,and its performance is not affected,which makes SGF electrode materials have potential applications in flexibility in the device.