Preparation And Performance Study Of Silicon Nanowire Array/PEDOT Supercapacitor Electrode Material

With the development of new energy sources such as wind energy,solar energy,hydropower,and biomass energy,new types of energy storage equipment have also emerged,such as solar cells,lithium ion batteries,and super capacitors.Compared with other energy storage devices,supercapacitors have the advantages of fast charging,long service life,stability,and no toxicity.Silicon,as the second most abundant element on earth,is the most researched element among all chemical elements.At the same time,silicon is used frequently in manufacturing computer chips and related hardware,and most semiconductor components are prepared with silicon as the raw material.Therefore,the preparation of electrode materials for supercapacitors based on silicon can be combined with the current silicon industry,which is could be easily conducive to the integration of capacitors and other electronic device chips.It has important scientific significance and long-term application prospects.Compared with planar silicon,silicon nanowire arrays?SiNWs?have a larger specific surface area,which facilitates the contact between the active layer and the electrolyte and increases the specific capacitance of the electrode material.In this thesis,SiNWs is used as the substrate,and the conductive polymer PEDOT is electroplated on the surface to prepare SiNWs/PEDOT composite supercapacitor electrode and devices,and the performances of the electrodes is optimized.The specific research work is as follows:1.Effect of Electrolyte on the Performance of PEDOTThe conductive polymer PEDOT was prepared on a silicon substrate by a constant voltage method using the ionic liquid as the electrolyte.In the experiment,the composition and morphology of PEDOT were characterized by scanning electron microscopy?SEM?,X-ray diffractometer?XRD?,and Fourier infrared spectrometer.A series of electrochemical performance tests were performed on the electrode materials through electrochemical workstations,such as cyclic voltammetry,AC impedance,and constant current charge and discharge.The experiment focused on the effects of different stages of the plating solution,which means the oligomers formed in the electrolyte during the electropolymerization,on the morphology,adhesion on the silicon substrate,and electrochemical performance of the conductive polymer PEDOT.2.SiNWs/PEDOT Supercapacitor Electrodes and Its DeviceSiNWs/PEDOT supercapacitors electrodes and devices were prepared by a simple solution method.SiNWs substrates were fabricated by metal ion assisted etching method.In order to study the influence of different SiNWs morphology on the properity of SiNWs/PEDOT electrodes,the TMAH solution was used to control the substrate's morphology.In addition,different electrolytes on the electrochemical performance of electrode materials were studied.On this basis,the mechanism of charge transport and storage in electrode materials was further explored.After optimization,the SiNWs/PEDOT electrode material has an area specific capacitance of 106.5 mF/cm² at a current density of 0.5 mA/cm².The specific capacitance of the prepared symmetric supercapacitor is 85.3 mF/cm² when the current density is 0.25 mA/cm².3.SiNWs/PEDOT/MnO₂ Electrode MaterialsThe morphology of etched SiNWs was tuned bya saturated phosphorus pentachloride solution.According to the previous experimental results,the ternary composite electrode material SiNWs/PEDOT/MnO₂ was prepared on the surface of the silicon nanoarray/PEDOT by the solution dipping method,where the conductive polymer PEDOT was used as the binder between silicon substrates and MnO₂.Then ternary composite electrode material was characterized by SEM,XRD and XPS.Additionally,a new electrode structure was designed using PEDOT:PSS as the charge transport layer of the electrode material,and the effects deposition time of PEDOT and immersion time of KMnO₄ on the electrode material properties were studied.Under simple optimization conditions,in a 1 M sodium sulfate electrolyte,the area specific capacitance of the electrode reached 233 mF/cm² when the current density was 2mA/cm².