Date of Award

6-1-2014

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Deyang Qu

Second Advisor

Jason Evans

Third Advisor

Jonathan Rochford

Abstract

Bismuth doped manganese dioxide (Chemically modified MnO2) has been synthetized through a co-precipitation method based on patents issued to Ford. The morphology of the chemically modified manganese dioxide has been characterized by SEM; the structural change in chemically modified MnO2 through heat treatment was detected by XRD; the capacity and rate capability of different samples have been investigated with the assistance of classical electrochemical methods. By doping with bismuth, chemically modified MnO2 reveals a longer cycle ability and higher capacity compared to the blank MnO2. Chemically modified MnO2 would keep the amorphous state until being heated up to 750°C. The capacity would decrease to half of the original value after the heat treatment.

Different methods of electrode construction were used to improve the integrity of the electrode. The hybrid supercapacitor based on chemically modified manganese dioxide and active carbon and an alkaline electrolyte was studied. Different cell set-ups for the supercapacitor were proposed. A lager working potential window and longer cell cycle life were gained by using chemically modified manganese dioxide as the positive electrode and active carbon as the negative electrode.

The cyclability of the cell was explored using parallel experiments designed to prove that the dissolution of Mn (III) is the critical factor extending the life of the cell. A sealed, electrode starved coin cell was employed in the cyclability test to reduce the dissolution of Mn (III). A longer cycle life of up to 500 cycles was reached with 60% of original capacity remaining.

Comments

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