Publication Date
2013
Document Type
Thesis
Committee Members
Hong Huang (Advisor), Sharmila Mitra Mukhopadhyay (Committee Member), Dan Young (Committee Member)
Degree Name
Master of Science in Engineering (MSEgr)
Abstract
Carbon-based nancomposites attract much attention as electrode materials in electrochemical energy storage systems due to their low-cost, extraordinary high electrical and thermal conductivity, super high surface area etc. In this research, graphene nanosheets (GNS) and their nanocomposites with manganese oxides (GNS/MnOx) or silicon nanowires (GNS/SiNWs/CF) are studied for their applications in Li-ion batteries and supercapacitors. GNS powders are synthesized via a chemical oxidation of nature graphite followed by appropriate reduction process. GNS/MnOx composites are synthesized rendering MnOx nanoparticles embedded on the surfaces of GNS. SiNWs grown in carbon fibers are mechanically mixed with GNS powders. The impacts of the manganese valence and GNS content in the GNS/MnOx nanocomposites on the lithium storage characteristics in terms of Coulombic efficiency, capacity, cycle life, and rate capability are investigated experimentally. GNS/MnOx hybrid anode material shows a high reversible lithium storage capacity up to 838 mAh/g with a Coulombic efficiency of 65%, good cyclic performance with 0.8% fading per cycle, and high rate capability with 67% at the current density of 800 mA/g. The GNS/SiNWs/CF hybrid exhibits high reversible 1discharge capacity of 975 mAh/g with Coulombic efficiency of 85.7%. Further the capacitive charge storage characteristics of both GNS and GNS/MnOx are studied in ionic liquid electrolytes and aqueous electrolytes, respectively. Supercapacitors consisting of GNS electrodes in EMIMBF4 ionic liquid electrolyte show the high specific capacitance of 109 F/g, good cyclic life of over 1000 cycles, high power density of 44.4 kW/kg, and high energy density of 256 Wh/kg etc. Supercapacitors consisting of GNS/MnO2 nanocomposite electrodes in Na2SO4 aqueous electrolyte deliver specific capacitance up to 164 F/g. This study shows significantly improved electrochemical performances in lithium-ion batteries and supercapacitors by using GNS-based composites.
Page Count
111
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
2013
Copyright
Copyright 2013, some rights reserved. My ETD may be copied and distributed only for non-commercial purposes and may not be modified. All use must give me credit as the original author.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.
