Synthesis Of Several Metal Oxides Nanomaterials And Their Pseudocapacitors Property

Electrochemical capacitors, also named supercapacitors, combined with high power density, fast charge and discharge, long cycle life, environmental friendliness, are one new kind of efficient and practical energy storage devices between batteries and capacitors. In this Master thesis, we focused on the design and synthesis of metal oxides(MnO2, WO3, etc.) and their composites, and explored their applications in flexible supercapacitors and electrochromic energy storage devices. The main work and findings are listed below:1. The synthesis and electrochemical performance of amorphous MnO2 nanostructures was researched. Doped worm-like amorphous MnO2 nanowires were obtained by electrodeposition, and the amorphous MnO2 electrode achieved a high specific capacitance of 334.7 F g-1 at 1 A g-1. Flexible supercapacitors based on the amorphous MnO2 nanowires electrodes showed good flexibility and electrochemical performance, with on decay under folding condition.2. Hydrogenation can significantly enhance the carrier densities of ZnO nanowires and improve their electrical and electrochemical activity. Highly conductive HZnO@MnO2 core-shell structure with improved electrochemical performance was designed. Flexible supercapacitors based on the HZnO@MnO2 core-shell electrodes were assembled. A self-powered system contained energy collection part(dye-sensitized solar cells based on TiO2) and energy storage part(supercapacitors based on HZnO@Mn O2) was designed, which broadened the application of supercapacitors.3. Asymmetric supercapacitors based on MnO2 as positive electrodes and metal oxides(Fe2O3 and MoO3) as negative electrodes was explored. A flexible asymmetric MnO2//Fe2O3 supercapacitor was assembled, whose positive electrode α-MnO2 was obtained by hydrothermal method and negative electrode amorphous Fe2O3 was derived from sacrificial template-accelerated hydrolysis, enhancing the work voltage window(1.6 V) and energy density(0.5 mWh cm-3). In addition, reciprocal alternate deposition strategy using metal oxide/carbon nanotube was developed. Multilayer CNT-MnO2//CNT-MoO3 asymmetric supercapacitors showed a high energy density of 1.7 mWh cm-3.4. WO3 film electrodes were fabricated by evaporation process. Large-scale pseudocapacitive glass windows(15 cm×15 cm) combining electrochromism and energy storage were invented. The charge storage mechanism of WO3 film is thickness-dependent, and 100 nm film showed excellent capacitive charge storage property in terms of capacity density(more than 95% stored charges is attributed to capacitive effects at 100 mV s-1). Furthermore, pseudocapacitance is responsible for around 70% of the capacitive charge storage in 100 nm film based on the electrochemical impedance spectroscopy analysis.