Document Type

Dissertation

Date of Award

5-31-2015

Degree Name

Doctor of Philosophy in Chemistry - (Ph.D.)

Department

Chemistry and Environmental Science

First Advisor

S. Mitra

Second Advisor

Edgardo Tabion Farinas

Third Advisor

Tamara M. Gund

Fourth Advisor

Haidong Huang

Fifth Advisor

Pradyot Patnaik

Abstract

Flexible electronics such as wearable equipment, displays, cell phones and smart cards require flexible power sources like batteries. In this thesis, the development of flexible batteries and supercapacitors are presented. Different types of flexible batteries including zinc carbon batteries, primary alkaline batteries, secondary alkaline batteries and zinc air cells are presented, These were designed, fabricated and improved using polymers and nano-carbons like carbon nanotubes (CNTs). CNTs are found to be effective as conductive additives compared to the traditional graphite. Purification is important to remove impurities that lead to side reactions/ corrosions. However, further treatment like carboxylation lead to higher electric resistance caused by the defects on CNT surface, which are created during the CNT acid treatment and functionalization. In case of secondary alkaline cells, CNTs can also provide channel for electrolyte to facilitate the recharge process.

Throughout the research in developing flexible batteries, it is found that polymers like polyethylene oxide (PEO) are used as binders to maintain flexibility; poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to be an effective conductive additive in acidic/neutral conditions; polyvinyl alcohol (PVA)-poly (acrylic acid) (PAA) copolymer separator membrane is found to be an effective separator and electrolyte storage in alkaline electrolyte.

Efforts are also made to generate highly defective and oxidized CNTs for fabrication of supercapacitor electrodes is also presented. CNTs are treated under microwave conditions for different durations to generate varying amounts of defects and oxidation levels. This is evidenced by the increase in BET surface area, D to G ratio and oxygen content with increase in treatment time. Under the given conditions, a treatment time of 40 min is found to be optimum, beyond which the increase in any of these properties as well as in specific capacitance is minimal. The increase in surface area enhances the double layer capacitance while the oxygenation may lead to pseudocapacitance. Together these make microwave treatment of CNTs an attractive approach to enhance supercapacitor performance.

Included in

Chemistry Commons

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