Design And Electrochemical Performance Of Polyaniline-based Supercapacitor Electrode Materials

Supercapacitors have attracted great attention because of their unique charging and discharging properties,but their lower energy density limits their applications.The selection of electrode materials is the key to solve this problem.To address this problem,this thesis investigates the factors influencing the morphology regulation of polyaniline and its derivatives and its relationship with electrochemical performance,with polyaniline as the core.Firstly,the morphology modification of polyaniline nanomaterials is studied,and then the cheap polyaniline is carbonized as a precursor,and the obtained highly conductive polyaniline-based carbon is surface modified and loaded with manganese dioxide as a substrate,so as to achieve a supercapacitor electrode material with low cost and good performance.The main contents are as follows:（1）Polyaniline nanobelts were synthesized at low temperature using the induction of aniline polymerization by p-phenylenediamine combined,as strong microscopic mixing by a rotating packed bed.It was shown that low temperature and suitable amount of p-phenylenediamine addition were crucial for the formation of polyaniline nanobelt,and the product obtained was polyaniline nanofibers at elevated temperature or decreasing amount of p-phenylenediamine addition.The degree of micro-mixing of the system before the reaction has a great influence on the homogeneity of the nanobelts.The poor microscopic mixing ability of the conventional mechanical stirrer resulted in significant differences in the number of p-phenylenediamine molecules around the newly generated polyaniline nanofibers and non-uniform product morphology,along with the formation of wider nanobelts and normal nanofibers.In contrast,the rotating filled bed was able to achieve a molecular level of mixing,resulting in the formation of homogeneous nanobelts with good electrical conductivity and fast ion diffusion behavior,which exhibited better electrochemical properties with a specific capacitance of 304.4 F/g@0.5 A/g.（2）After carbonization and KOH activation,polyaniline nanofibers with good electrochemical properties were obtained by using polyaniline nanofibers with p-phenylenediamine modified morphology as precursors.It was shown that p-phenylenediamine could increase the specific capacitance of polyaniline-based carbon nanofibers by up to 42.5%by modulating the morphology without changing the molecular structure and functional group ratio.The carbonization temperature affects the graphitization degree and nitrogen atom doping of polyaniline-based carbon nanofibers,while the excess of activator can lead to fracture or even sintering of carbon nanofibers.At a carbonization temperature of 700°C and an activator mass ratio of 0.5,the polyaniline-based carbon nanofibers with p-phenylenediamine modified morphology improved the specific capacitance by 165.6%compared to the untreated ones.In addition,the specific capacitance remained at 254.0 F/g@0.5 A/g when the electrode loading mass was as high as 16 mg/cm²,which has good application prospects.（3）The polyaniline-based carbon nanofibers/MnO₂ composites were prepared by using the redox reaction between carbon and potassium permanganate,with surface-modified polyaniline-based carbon nanofibers as the substrate.Under the same conditions,it was shown that acid treatment would introduce a large number of oxygen-containing functional groups on the surface of carbon fibers,resulting in the change of MnO₂ morphology from acicular to lamellar and crystalline shape fromα（m）toδ,while the specific capacitance of the composites could be enhanced by up to 87.6%.Regarding the reaction conditions,an increase in the reaction temperature leads to the formation of larger grains of MnO₂ on the carbon surface,while an increase in the ratio of reactants leads to a peak valley in the size of the resulting MnO₂ crystal particles.In addition,the mode of potassium permanganate addition also influences the morphology and electrochemical properties of the generated MnO₂.After optimization of the conditions,the specific capacitance of polyaniline-based carbon nanofiber/MnO₂ composite can achieve 166.7 F/g@0.5 A/g.This thesis has 37 figures,9 tables and 108 references.