Date of Award

12-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Packaging Science

Advisor

Darby, Duncan

Committee Member

Tonkin , Charles

Committee Member

O'Hara , Liam

Committee Member

Ray , William

Abstract

Living in a world full of portable electronics, there is great need for energy storage devices. Currently, limitations for storage involve power inefficiencies as well as bulkiness. This is why printable charge storage devices that display good electrochemical performance are needed. It is for this reason that research into the production and packaging of carbon nanotube based super capacitors was carried out.
A super capacitor can be built by using high surface area multi-walled carbon nanotubes suspended in an ionic liquid. The two active electrodes are made from a combination of the multi-walled carbon nanotubes and an ionic liquid, ground into a gel, and then formulated into a printable functional ink. The super capacitor is then built upon a conducting carbon foam substrate where the two electrodes are printed and sandwiched on top of a membrane that allows ion-ion transfer without allowing any physical exchange of nanotube particles.
The purpose of this research was to find a printing method or technique that produced functional carbon nanotube based electrodes for supercapacitor assembly. This process involved changing printing variables such as the mesh count for the screen, the type of stencil used, and the thickness of the emulsion applied.
Other variables altered for this study focused on the ink formulation portion of the testing. These variables included creating a medium that dispersed the carbon nanotubes, chemical carrier agents for the carbon nanotubes and ionic liquid, ionic liquid selection, concentration of the chemical to the bucky gel relationship, temperature used for curing the ink, and the influence of adhesive agents present in the ink.
The printed electrodes were assembled with the separator membrane into supercapacitors that were then measured in the electrochemical cell. The charge/discharge curves were used to calculate the current density and specific capacitance of each combination of supercapacitors.
Supercapacitors made of printed electrodes that were 40% bucky gel and 60% 1-methyl-2-pyrrolidinone (with the bucky gel as 9.82% multi-walled carbon nanotubes, 88.42% ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate, and 1.76% Teflon¨ binder) were found to perform the best out of all other combinations of electrodes printed on carbon foam substrate. All printed electrodes had measurable results except for those printed on aluminum substrate.

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