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The influence of electrode and separator thickness on the cell resistance of symmetric cellulose–polypyrrole-based electric energy storage devices
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.ORCID iD: 0000-0002-5496-9664
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
2014 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 272, 468-475 p.Article in journal (Refereed) Published
Abstract [en]

The influence of the cell design of symmetric polypyrrole and cellulose-based electric energy storage devices on the cell resistance was investigated using chronopotentiometric and ac impedance measurements with different separator and electrode thicknesses. The cell resistance was found to be dominated by the electrolyte and current collector resistances while the contribution from the composite electrode material was negligible. Due to the electrolyte within the porous electrodes thin separators could be used in combination with thick composite electrodes without loss of performance. The paper separator contributed with a resistance of similar to 1.5 Omega mm(-1) in a 1.0 M NaNO3 electrolyte and the tortuosity value for the separator was about 2.5. The contribution from the graphite foil current collectors was about similar to 0.4-1.1 Omega and this contribution could not be reduced by using platinum foil current collectors due to larger contact resistances. The introduction of chopped carbon fibres into the electrode material or the application of pressure across the cells, however, decreased the charge transfer resistance significantly. As the present results demonstrate that cells with higher charge storage capacities but with the same cell resistance can be obtained by increasing the electrode thickness, the development of paper based energy storage devices is facilitated.

Place, publisher, year, edition, pages
2014. Vol. 272, 468-475 p.
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-218812DOI: 10.1016/j.jpowsour.2014.08.041ISI: 000344208700058OAI: oai:DiVA.org:uu-218812DiVA: diva2:697361
Available from: 2014-02-18 Created: 2014-02-18 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Nanocomposites of Cellulose and Conducting Polymer for Electrical Energy Storage
Open this publication in new window or tab >>Nanocomposites of Cellulose and Conducting Polymer for Electrical Energy Storage
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The world’s increased energy storage demand, as well as the environmental concerns related to the combustion of fossil fuels, has triggered a transition to intermittent renewable energy sources as well as to electrical and hybrid vehicles. Current day rechargeable batteries are, due to the invention and development of lithium ion batteries, technologically well positioned to answer to some of these demands. Conventional batteries, however, utilize inorganic materials of limited supply that require large amounts of energy during refining and processing. The materials also add a significant cost to the final product, making the rechargeable batteries less attractive for large scale applications. During the last decade, significant efforts have been made to find suitable organic matter based electrode materials that can replace the inorganic materials. One class of organic materials that can be used for electrical energy storage, or be included as components in organic matter based energy storage systems, is conducting polymers.

The aim of this thesis was to investigate the possibilities and limitations of using the conducting polymer polypyrrole in energy storage applications. The polymer was synthesized onto cellulose extracted from the Cladophora sp. algae, and the result was a flexible composite material. Symmetrical energy storage devices constructed with the composite material were shown to exhibit a pseudocapacitive behavior. The resistance in the cells was investigated and was found to scale linearly with the separator thickness. Cells could be cycled for 4,000 cycles without significant capacitance loss and cells that were overcharged to 1.8 V cell potential, were found to be protected by a resistive potential drop. Devices were constructed as proof-of-concept and were used to power a remote control and a digital thermometer.

The self-discharge in polypyrrole was studied extensively. It was found that oxygen was responsible for the oxidation of the reduced electrode, while the positive electrode self-discharged due to a faradaic reaction. Through spectroscopy and the temperature dependence of the self-discharge, it was suggested that the self-discharge of oxidized polypyrrole is linked to the degradation at high potentials, commonly referred to as overoxidation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 60 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1125
Keyword
Polypyrrole, Nanocomposites, Energy storage, Conducting polymers, Cellulose
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-218815 (URN)978-91-554-8883-3 (ISBN)
Public defence
2014-04-04, Å4001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2014-03-13 Created: 2014-02-18 Last updated: 2014-04-29
2. On the electrochemical performance of energy storage devices composed of cellulose and conducting polymers
Open this publication in new window or tab >>On the electrochemical performance of energy storage devices composed of cellulose and conducting polymers
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Applications that require electrical energy storage are becoming increasingly diverse. This development is caused by a number of factors, such as an increasing global energy demand, the advent of electric vehicles, the utilization of intermittent renewable energy sources, and advances in disposable and organic electronics. These applications will set different demands on their electrical energy storage and, thus, there will be no single technology used for all applications. For some applications the choice of energy storage materials will be extremely important. Conventional batteries and supercapacitors rely on the use of nonrenewable inorganic materials mined from depleting ores, hence, requiring large amounts of energy for their processing. Such materials also add a significant cost to the final product, making them less attractive for large scale applications. Conducting polymers, on the other hand, constitute a class of materials that can be used for organic matter based energy storage devices.

The aim of this thesis was to investigate the use of a composite consisting of the conducting polymer polypyrrole (PPy) and cellulose derived from Cladophora sp. algae for electrical energy storage. The polymer was coated onto the cellulose fibers by chemical polymerization resulting in a flexible material with high surface area. By using this composite as electrodes, electrochemical cells consisting of disposable and non-toxic materials can be assembled and used as energy storage devices. The resistances of these prototype cells were found to be dominated by the resistance of the current collectors and to scale with the thickness of the separator, and can hence be reduced by cell design. By addition of nanostructured PPy, the weight ratio of PPy in the composite could be increased, and the cell voltages could be enhanced by using a carbonized negative electrode. Composites of cellulose and poly(3,4-ethylenedioxythiophene) could also be synthesized and used as electrode materials. The porosities of the electrodes were controlled by mechanical compression of the composite or by coating of surface modified cellulose fibers with additional PPy. Finally, the self-discharge was studied extensively. It was found that oxygen was responsible for the oxidation of the negative electrode, while the rate of self-discharge of the positive electrode increases with increasing potential. Through measurements of the charge prior to and after self-discharge, as well as with an electrochemical quartz crystal microbalance, it was found that the self-discharge of the positive electrode was linked to an exchange of the counter ions by hydroxide ions. It is also demonstrated that the self-discharge rate of a symmetric PPy based device can be decreased dramatically by proper balancing of the electrode capacities and by reducing the oxygen concentration. The results of this work are expected to contribute towards future industrial implementation of electric energy storage devices based on organic materials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1403
Keyword
polypyrrole, supercapacitors, self-discharge
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-300917 (URN)978-91-554-9651-7 (ISBN)
External cooperation:
Public defence
2016-09-30, Å80121, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2016-09-09 Created: 2016-08-16 Last updated: 2016-09-13

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Tammela, PetterStrømme, MariaNyholm, Leif

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