Date of Award

Fall 2012

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Materials Science and Engineering

Supervisor

Igor Zhitomirsky

Language

English

Abstract

The development of all-electric or plug-in hybrid vehicles requires the use of advanced energy storage devices with high power. Dedicated for energy storage, electrochemical supercapacitors (ES) offer the advantage of high power density. High power ES can provide load-leveling for batteries and fuel cells during starting, acceleration, hill climbing and braking. ES are important for reducing cycling of batteries, thus extending their lifetime by energy storage and delivery during fast transient operations such as in braking (storage) or start up and acceleration (supply).

The interest in polypyrrole (PPY) for the application in ES is attributed to the high specific capacitance (SC) of this material. The possibility of PPY deposition on stainless steel substrates is important for the practical applications of PPY films in ES, using low cost stainless steel current collectors. The important task is to avoid anodic dissolution of the substrates during PPY electropolymerization. Polypyrrole (PPY) films were electrochemically deposited on stainless steel substrates or Ni plaque from aqueous pyrrole solutions containing anionic additives. The method resulted in the formation of adherent and uniform films. The deposition yield was investigated at galvanostatic conditions. It was found that anionic additives can be used for the dispersion of multiwall carbon nanotubes (MWCNTs) and fabrication of composite PPY–MWCNT films. The deposition yield was studied under galvanostatic conditions. The mechanism of PPY–MWCNTs deposition was discussed. The incorporation of MWCNTs into the PPY during electropolymerization resulted in the formation of porous films. The films were investigated for the application in electrodes of electrochemical supercapacitors. Electrochemical testing in the 0.5M Na2SO4 electrolyte solutions showed a capacitive behaviour in a voltage window of -0.5 to +0.4 V versus a saturated calomel electrode. The results indicated that the PPY–MWCNT films deposited on the stainless steel and nickel plaque substrates are promising electrode materials for ES.

McMaster University Library

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