| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 100 === This research can be divided into three parts: the intercalation of (1) MnO nanoparticles, (2) Ag nanoparticles and nanowires, and (3) ZnO nanoparticles into graphene nanosheets (GNs), forming three-dimensional hybrids as anode materials for high-performance Li-ion batteries.
(1) A composite of GNs supported by MnO nanocrystals has been fabricated through a simple chemical-wet impregnation followed by the thermal reduction route. The hybrid contains of MnO nanoparticles with an average size of 20-40 nm uniformly dispersed on GNs as observed by transmission electron microscopy. The MnO/GN composite anode delivers a reversible capacity of 635 mAh/g at 0.2 C. The GN plays a buffer effect role in this hybrid material that improves the Coulombic efficiency (92.7%) at the 1st cycle and rate capacity (capacity retention (5 C/0.2 C)>70%). This illustrates the superior performance of MnO/GN composite anode in Li-ion batteries.
(2) An efficient microwave synthesis was employed to fabricate different structures of Ag nanostructures, i.e., nanoparticles and nanowires. The simple chemical-wet impregnation followed by the thermal reduction route was adopted to prepare Ag nanoparticles/GN (Ag-NP-GN) and Ag nanowires/GN (Ag-NW-GN) anode materials. The Ag-NW-GN composite anode material delivers a high capacity of 1723 mAh/g at 0.1 C, a low irreversible capacity at 1st cycle, and an improved rate capability (capacity retention (5 C/0.1 C) > 65%) as well.
(3) The hexagonal ZnO nanoparticles were synthesized by using the microwave-assisted method. Again, the simple chemical-wet impregnation followed by the thermal reduction route was applied to fabricate ZnO nanoparticles/GN (GN-ZnO) composite anode materials. The hybrid, consisted of as-grown ZnO nanoparticles with an average size of 100 nm, exhibits a well-defined wurtzite crystal structure. Experimental result showed that the GN-ZnO composite anode displays a high capacity of 1048 mAh/g at 0.1 C, a low irreversible capacity at 1st cycle, and an enhanced rate capability (capacity retention (5 C/0.1 C) > 60%) as well.
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