Studies On The Preparation Of IL/Polymer Composites And Their Electrochemical Capacitance Performance

Supercapacitor is a new kind of energy storage device in the field of electrochemical research.Compared with the traditional battery,it has some advantages,such as short charging time,long cycle life,environment friendliness and high energy density,and has attracted much attention in many fields.Supercapacitors include electric double layer capacitors and pseudostructures.Normally,electrode material is the most important for a supercapacitor capacitor.Therefore,the design of high performance electrode material for supercapacitor is a hot topic.Carbon materials have good conductivity,high thermal conductivity,high specific surface area,adjustable pore structure,good mechanical and thermal stability and other advantages.Furthermore,the conductive polymers are also regarded as electrode materials for capacitor because they have low cost,low environmental pollution,and in the doping state they have high conductivity,wide voltage window,large storage capacity,reversibility and adjustability.As"green solvents",ionic liquids have been studied further due to their unique physical and chemical properties,such as wide electrochemical windows,good electrical conductivity,good light transmission,high refractive index,non-volatility,wide liquid,high specific heat capacity and energy storage,negligible vapor pressure,high thermal stability,selective dissolution and design feasibility.In this paper,several kinds of nanocomposite electrode materials based on ionic liquids for the electrochemical performance of supercapacitors were designed and synthesized.Therefore,the main purpose of this research is to explore and develop the application of ionic liquids in electrochemical research.1.This thesis introduces the concept,classification and application of"green solvent"ionic liquids in green chemistry.In addition,the concept of supercapacitor,classification and the factors influenced performance of its capacitance are briefly described.2.Twoacidicionicliquidswereprepared,including1-vinyl-3-carboxymethylimidazole?[VCMIm]Cl?ionicliquid,1-?4-sulfonic acid?-butyl-3-vinylimidazolium hydrogen sulfate?[SBVIm][HSO₄]?ionic liquid,and their structures were characterized by ¹H NMR and ¹³C NMR,and the melting points were also measured.3.PPy nancomposite electrode was prepared by in-situ oxidative polymerization method using ferric chloride?FeCl₃?as oxidants and ionic liquid as dopants that adjusting the type of dopant,feed ratio with dopant and oxidant.The morphology of the as-prepared materials were characterized,and the electrochemical properties of the material in the potassium chloride electrolyte were also measured.The electrode material for supercapacitor with better performance was prepared by adjusting the amount of oxidant and dopant.It was found when the ratio of the oxidant to the pyrrole monomer was 2:1,the specific capacitance of the obtained PPy was the highest.The concentration and type of the dopant also have an influence on PPy morphology and electrochemical properties.The dopant-free PPy is a flat cubic shape,while nano-sheet and spherical could be obtained using[VCMIm]Cl ionic liquid and[SBVIm][HSO₄]ionic liquid as dopant.When the concentration of[VCMIm]Cl ionic liquid as dopant increases,microstructure of nanocomposite material gradually changes from nanorods to nanometer flakes with certain degree of regularity,but the concentration continues to increase it aggregates.When the ratio of[VCMIm]Cl to is 3:1,the specific capacitance reached 520F g^-1 and the capacity remains 82%after 800 cycles.However,using the specific capacitance of[SBVIm][HSO₄]ionic liquid as dopant,the specific capacitance is 306 F g^-1.From the above results,both of the specific capacitances are higher than the one of the pure polypyrrole(153 F g^-1).4.1-vinyl-3-cyanomethylimidazoliumbromide?CMVImBr?andpoly[3-cyanomethyl-1-vinylimidazoliumbis?trifluoromethanesulfonyl?imide]?PCMVIm-Tf₂N?were prepared via simple radical polymerization and ion exchange,and characterized.Then,the porous nitrogen-doped carbon film was prepared via the template-free method and the Pyrolysis carbonization at different temperatures using the composite film of the poly?ionc liquid?and the carboxymethyl chitosan?CMCS?as the precursor.The obtained carbon material has large specific surface areaand high nitrogen content.The carbon material is used as a supercapacitor electrode material for electrochemical performance measurement.The material exhibits high capacitance performance and good cycle stability.The specific capacitance is 633 F g^-1 at a current density of 0.1 A g^-1.When the current density is 3 A g^-1,the specific capacitance retention rate is almost unchanged after 10,000 cycles.