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Graphene-based Materials for Electrochemical Energy Storage

Yang, Hao
http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095146429831

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
A challenge the world is facing in the 21st century is how to meet the increasing energy needs. Since electricity was discovered and exploited, more and more attention has been focused on effective energy storage technologies. Compared with batteries and fuel cells, supercapacitors can provide a high charging/discharging rate, high power density, and long cycling stability. However, the commercially available supercapacitor technologies suffer from low energy density, which is 1-2 orders lower than batteries. An ideal electrode for supercapacitor should be able to offer high surface area, porous morphology, high mechanical strength, and electrochemical stability. Graphene, as a good electrode candidate with a high surface area, physical and chemical stability and appealing electrical properties arising from its unique honeycomb lattice structure. There have been a variety of synthesis methods developed to produce graphene; however, the cost, throughput, material quality, and electrochemical performance fail to meet the requirements of the energy storage industry. The objective of this PhD research is to develop efficient graphene synthesis methods, improve the energy density of supercapacitors, and exploit supercapacitors in on-chip energy storage applications. The key results and scientific findings from this research are: (1) Three thermally reduced graphene materials have been synthesized, characterized and examined as supercapacitor electrodes. The interlayer spacing revealed by X-ray diffraction (XRD), is in the range of 3.53-3.76 Å and close to the case of graphite, suggesting substantial removal of oxygen groups. X-ray photoelectron spectroscopy (XPS) shows the C/O ratio increases from 2.02 in graphite oxide to 5.11-7.87 in graphene materials, revealing the successful reduction. The nitrogen adsorption isotherm measurement reveals the surface area and pore distribution in the mesopore and micropore range. Ultra-high energy density (as high as 148 Wh/kg) and specific capacitance (as high as 306 F/g) have been demonstrated with prepared graphene electrodes. The enhanced electrochemical performance is attributed to the superior material quality and pore size distribution. Based on the comparison between three graphene materials, it is found that the energy storage performance is not only affected by the reduction extent and surface area of electrode materials, but also the pore size distribution and defects. (2) Micropower sources have gathered a lot of attention due to the rapid development of microelectronic devices, such as microelectromechanical systems, nanorobotics, wireless sensor networks, micro medical devices, etc. Microsupercapacitors can provide fast charge-discharge rate, outstanding power density several orders higher than batteries, and long lifetime up to millions of cycles. This dissertation describes the microfabrication technologies compatible with semiconductor manufacturing, such as photolithography and electrophoretic deposition (EPD), to deposit the synthesized graphene materials on a micro interdigital pattern forming microsupercapacitors. High areal capacitance of 17.36 mF/cm2 and energy density of 2.41 mWh/cm3 have been observed in the graphene microsupercapacitors. The microsupercapacitors also demonstrate outstanding power density of 60.82 W/cm3 and cycling stability with 92% capacitance retention during 10,000 cycles. The appealing properties of this graphene supercapacitor technology may become new paradigm in electrochemical energy storage.
Wu Lu (Advisor)
Marvin White (Committee Member)
James Lee (Committee Member)
177 p.
Electrical Engineering; Energy; Engineering; Materials Science
energy storage; graphene; supercapacitor; electrochemistry; microsupercapacitor

Recommended Citations

Citations

  • Yang, H. (2017). Graphene-based Materials for Electrochemical Energy Storage [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095146429831

    APA Style (7th edition)

  • Yang, Hao. Graphene-based Materials for Electrochemical Energy Storage. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095146429831.

    MLA Style (8th edition)

  • Yang, Hao. "Graphene-based Materials for Electrochemical Energy Storage." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095146429831

    Chicago Manual of Style (17th edition)

osu1512095146429831
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© 2017, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.