Access Type

Open Access Thesis

Date of Award

January 2014

Degree Type

Thesis

Degree Name

M.S.

Department

Physics and Astronomy

First Advisor

Gholam-Abbas Nazri

Second Advisor

Ratna Naik

Abstract

With the rapid development of electric-based transportation and introduction of various hybrids, plug-in and full electric vehicles, there is an urgent need to develop a high power energy storage system to complement the high energy density batteries, to extend the range and life of HEVs and EVs. In this work, we have developed and optimized a unique composite material that can serve as electrode materials for high power supercapacitor for various applications. The material is prepared form high surface area graphene-like carbon made from exfoliated graphite flakes through thermal shock process. The expanded graphite then is mixed with functionalized stacked cone carbon nano-fiber. The mixture was impregnated with nano size manganese oxide, MnO2, to further enhance the energy storage density and the high rate capability of the composite material. The formulation of our composite mixture contains, [(graphene) - (carbon nano-fiber), (MnO2)]. The optimized composite mixture was impregnated into metal foam that served as a current collector in an electrochemical cell.

The X-ray diffraction of the composite has shown formation mixed phases of MnO2, and SEM results indicate uniform deposition of oxide on graphene-like carbon and on carbon nano-fibers. The electrochemical performance of the composite was tested for its energy storage capacity (F/g) and for its high rate capability using cyclic voltammetry. The stability of the composite was also tested during multiple charge-discharge cycles. The composite electrode provides exceptionally high charge storage capacity (over 300 F/g), with high charge-discharge cycling stability over 500 deep cycles. Further optimization and scale - up of the composite material is in progress.

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