Study On Preparation And Performance Of Asymmetric Supercapacitor

As a new type of energy storage device between traditional electrostatic capacitor and rechargeable batteries, asymmetric supercapacitor（ASC） is regarded as the best energy storage device for its high energy density and power density, which was defined for its anode material and cathode material. Considering the research background and approach, this thesis starts from the synthetic of nano-size electrode materials, and deep in searching the best couple to assemble into an ASC device, the main contents are as follows:Firstly, sulfur-doping Co₃O₄（S-Co₃O₄） nanowires have been synthesized as cathode material using nitric acid cobalt as cobalt, and vulcanizing its surface with thioacetamide. The areal capacitance and galvanostatic areal capacitances respectively reach a relatively high values of 0.55F/cm² at 10mV/s and 0.68F/cm² at 10 mA/cm²,which is over eleven times higher than those of the as grown Co₃O₄ nanowire electrode.Besides, the areal capacitance remains more than 92% after 10000 cycles,demonstrating its excellent capacitance stability as negative electrode.After it, we synthesize MnO₂ nanoparticles as anode material by anodic electrodeposition method and explore different electrodeposition time effects on the electrochemical performance. Flexible ASCs are also fabircated by using S-Co₃O₄ nanowires as negative electrode and MnO₂ as positive electrode. An excellent gravimetric energy density of 0.86 mWh/cm3 was achieved at an average power density of 0.79W/cm3 for the MnO₂ //S-CO₃O₄ ASC device. Moreover, stable cycle capability was also achieved.Nanomaterial cobalt sulfide（Co S） was fabricated on a carbon cloth substrate by two-step hydrothermal method. The composition and morphology of the material were characterized by X-ray diffraction patterns, Scanning Electron Microscppe（SEM）,Transmission Electron Microscope（TEM） and X-ray photoelectron spectroscopy（XPS）.The electrochemical measurements were performed in a three-electrode system. Theresult shows that Co S nanomaterial achieved an areal capacitance of 1.98 F/cm² at2mA/cm² in a 5 M LiCl solution, while the IR drop is only-0.018 V. Moreover, the CoS nanomaterial has an long-term cycling stability with more than 85.7% capacitance retention after 10000 cycles, confirming its larger capacitance, good redox activity and electrochemical stability.