The Construction Of Nanoarray Oxides Materials And Their Applications In Aqueous Electrochemical Energy Storage

With the rapid consume of fossil energy, the demand of new energy is getting more urgent. Electrochemical energy storage attracted worldwide attention because it is a kind of environmental friendly, safe, and renewed energy system. As two major important devices for electrochemical energy storage, batteries and supercapacitors have attracted worldwide attention and they cost considerable efforts. The main factors to affect the performance of the electrode materials include phase state, sizes, structure and so on. Nanoarrays, as a kind of highly order nanostructure, have become a promising candidate for electrode materials. The performance is highly dependent on the structures, so it is necessary to optimize the growth process and structure of the materials. Up to date, the investigated materials in supercapacitors are mostly directed towards the cathode materials, whereas there are only a few reports on the anode materials. It needs to devote more efforts to research how to pair the anode and cathode to combine as a total electrochemical energy storage. To address these concerns, the details of this essay are summarized as follows:1) We have developed a multi-step hydrothermal reaction and a following calcination process to fabricate hierarchical Co3O4@NiO nanostrips@nanorods arrays directly grown on conductive substrate. Co2(OH)2CO3 nanowires were firstly grown on the nickel foam to form a well-aligned array-like structure. Afterwards, the Co2(OH)2CO3 nanowires were converted into Co(OH)2 nanostrips by a secondary hydrothermal treatment, which dissolved and recrystallized the precursor nanowires. Thirdly, the Ni2+ salt was subsequently added and precipitated to obtain a hierarchical structure. Due to the unique architecture, the hierarchical nanoarrays exhibited an outstanding capacitive performance (2.91 mAh cm-2 or 26 F cm-2) as the positive electrodes.2) We have successfully fabricated hierarchical CoxFe3-xO4 nanoarray which composed of well aligned nanowire@nanorods arrays on Cu foam by a simple two-step hydrothermal reaction and a following annealing treatment. The hierarchical CoxFe3-xO4 nanoarray could work as an anode thanks to the redox reactions of Fe. The novel structure of hierarchical CoxFe3-xO4 nanoarray. The hierarchical architecture showed a high areal capacity and excellent rate capability, owing to the high mass loading and high porosity of the active materials, and the direct contact to the current collector underlying. In addition, by employing hierarchical Co3O4@Ni-Co-O nanoarray as the cathode electrode, a new battery system was established, which delivered a high energy density of ～2.08 m Wh cm-2, and a power density of-42.56 mW cm-2 with less than 3 min for one charge-discharge cycle. Combination of these features endows the double hierarchical nanoarray s-based aqueous battery as one of the most potential candidates for next generation energy storage devices.3) The fabrication and application of the flexible and transparent film electrodes is the tendency of scientific research, which could make the electric device portable and wearable. We fabricate a new transparent electrode by painting Ag nanowire film on the PET firstly, followed by electrodepositing Ni(OH)2 nanowire. The sample retain a comparable high transmittance and highly order array structure. Because of the good conductivity of Ag nanowire and psudocapacitive Ni, the transparent electrode deliver a high capacitance, good rate ability and good cycling stability. The enhancement of transparent electrode could broaden the application of the nanoarrays-based materials.