Additive Manufacturing of Hybrid Composites for Flexible Electronic Application
Date
2023-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
New York State College of Ceramics at Alfred University. Inamori School of Engineering.
Abstract
Material extrusion 3D printing is capable of fabricating complex macrostructures and designing microstructures for next-generation flexible electronics. Thick electrodes are promising to increase the mass loading of active materials in supercapacitors, but the 3D geometries and microstructures in thick electrodes still hinder the development with high electron and ion exchange rate and accessible active sites. The scaffold 3D electrodes of reduced graphene oxide:manganese oxide/carbon nanotube (rGO:MnOx/CNT) with highly-ordered microstructure were manufactured by material extrusion 3D printing, freeze-drying, and thermal treatment. The increasing amount of MnOx/CNT composites improved the areal capacitance. And the rate capability remained stable at different thicknesses. A 2 mm thick rGO:MnOx/CNT (weight ratio 5:3) electrode exhibited an excellent area capacitance contributed by the highly ordered rGO networks.
Fiber-shaped supercapacitors are attractive as an energy storage unit due to their excellent flexibility. However, fabricating robust fibers with large yields remained a challenge. The present study fabricated the core-sheath fibers through coaxial extrusion printing. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties was extruded from the outer channel, while GO slurry was extruded from the inner channel simultaneously. The followed freeze-drying process protected GO sheets from agglomeration, providing more efficient chemical reduction. After reduction, rGO sheets were separated and expanded to fill in the CMC sheath, which eliminated the delamination between the CMC sheath and rGO core.
Apart from the 1D core-sheath fiber electrode, 3D printed electrode with core-sheath structure provided a solution for the development of thick supercapacitors. Specifically, 3D thick rGO/CNT-rGO/CNT/MnO@CNT (rGC-rGCMC) electrodes with controlled lattice architectures, core-sheath structure, and hierarchical porosity were prepared. The electrodes with different volume ratios of core to sheath, including 100%-0%, 0%-100%, 20%-80%, 30%-70%, 40%-60%, and 50%-50%, were investigated to explore the influences of core-sheath structure on thick electrodes. All capacitance decays from core-sheath electrodes (20%-80%, 30%-70%, 40%-60%, and 50%-50%) were smaller than rGCMC (0%-100%) electrodes, indicating the improved rate capability from the core-sheath structure. Compared 30%-70% core-sheath electrodes with electrodes made of homogenous 30% rGC and 70% rGCMC mixture (30%+70%), lower capacitance (382.27 mF cm^-2 and 25.66 F g^-1 at 0.5 mA cm^-2) of 30%+70% mixture electrode without core-sheath structure suggested less efficiency to harvest electrons from the redox reactions. Electrochemical impedance spectroscopy (EIS) data further supported and explained the resistances of thick electrodes with different volume ratios.
Description
Thesis completed in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Science and Engineering at the Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis
item.page.format
Keywords
Supercapacitors, Three-dimensional printing, 3D printing, Composite materials