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Paper-based Supercapacitors
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (Material Physics)
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The growing market of mobile electronic devices, renewable off-grid energy sources and electric vehicles requires high-performance energy storage devices. Rechargeable batteries are usually the first choice due to their high energy density. However, supercapacitors have a higher power density and longer life-time compared to batteries. For some applications supercapacitors are more suitable than batteries. They can also be used to complement batteries in order to extend a battery's life-time. The use of supercapacitors is, however, still limited due to their high costs. Most commercially available supercapacitors contain expensive electrolytes and costly electrode materials.

In this thesis I will present the concept of cost efficient, paper-based supercapacitors. The idea is to produce supercapacitors with low-cost, green materials and inexpensive production processes. We show that supercapacitor electrodes can be produced by coating graphite on paper. Roll-to-roll techniques known from the paper industry can be employed to facilitate an economic large-scale production. We investigated the influence of paper on the supercapacitor's performance and discussed its role as passive component. Furthermore, we used chemically reduced graphite oxide (CRGO) and a CRGO-gold nanoparticle composite to produce electrodes for supercapacitors. The highest specific capacitance was achieved with the CRGO-gold nanoparticle electrodes. However, materials produced by chemical synthesis and intercalation of nanoparticles are too costly for a large-scale production of inexpensive supercapacitor electrodes. Therefore, we introduced the idea of producing graphene and similar nano-sized materials in a high-pressure homogenizer. Layered materials like graphite can be exfoliated when subjected to high shear forces. In order to form mechanical stable electrodes, binders need to be added. Nanofibrillated cellulose (NFC) can be used as binder to improve the mechanical stability of the porous electrodes. Furthermore, NFC can be prepared in a high-pressure homogenizer and we aim to produce both NFC and graphene simultaneously to obtain a NFC-graphene composite. The addition of 10% NFC in ratio to the amount of graphite, increased the supercapacitor's capacitance, enhanced the dispersion stability of homogenized graphite and improved the mechanical stability of graphite electrodes in both dry and wet conditions. Scanning electron microscope images of the electrode's cross section revealed that NFC changed the internal structure of graphite electrodes depending on the type of graphite used. Thus, we discussed the influence of NFC and the electrode structure on the capacitance of supercapacitors.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2014. , 65 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 112
Keyword [en]
graphene, graphite, paper, nano fibrillated cellulose, supercapacitor, electric double-layer capacitor, energy storage, roll-to-roll, coating, kinetic energy recovery
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:miun:diva-22410ISBN: 978-91-87557-68-2 (print)OAI: oai:DiVA.org:miun-22410DiVA: diva2:732015
Presentation
2014-06-12, O 102, Mid Sweden University, Holmgatan 10, Sundsvall, 10:15 (English)
Opponent
Supervisors
Available from: 2014-08-18 Created: 2014-07-03 Last updated: 2015-03-13Bibliographically approved
List of papers
1. Supercapacitors with graphene coated paper electrodes
Open this publication in new window or tab >>Supercapacitors with graphene coated paper electrodes
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2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, 481-485 p.Article in journal (Refereed) Published
Abstract [en]

Paper based supercapacitors are prepared by stacking a paper between two graphene electrodes and soaking these in an aqueous electrolyte. We demonstrate that supercapacitors can easily be manufactured by using proven paper technologies. Several different electrode materials were compared and two types of contacting material, silver and graphite foil were tested. The influence of the paper used as separator was also investigated. The supercapacitors with a graphene-gold nanoparticle composite as electrodes showed a specific capacitance of up to 100 F/g and an energy density of 1.27 Wh/kg. The energy density can further be increased by using other electrolytes. The silver contacts showed a pseudo capacitance, which the graphite contacts did not. The papers tested had a minor effect on the capacitance, but they have an influence on the weight and the volume of the supercapacitor.

Keyword
Coating; Graphene; Graphite; Paper; Supercapacitor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-16880 (URN)10.3183/NPPRJ-2012-27-02-p481-485 (DOI)000315696000044 ()2-s2.0-84865260056 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2013-04-04 Created: 2012-08-29 Last updated: 2017-12-07Bibliographically approved
2. Enhanced electrical and mechanical properties of nanographite electrodes for supercapacitors by addition of nanofibrillated cellulose
Open this publication in new window or tab >>Enhanced electrical and mechanical properties of nanographite electrodes for supercapacitors by addition of nanofibrillated cellulose
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2014 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 12, 2581-2586 p.Article in journal (Refereed) Published
Abstract [en]

Graphene and porous carbon materials are widely used as electrodes in supercapacitors. In order to form mechanically stable electrodes, binders can be added to the conducting electrode material. However, most bindersdegrade the electrical performance of the electrodes. Here we show that by using nanofibrillated cellulose(NFC) as binder the electrical properties, such as capacitance, were enhanced. The highest capacitance was measured at a NFC content of approximately 10% in ratio to the total amount of active material. NFC is a good ionconductor and improves the access of ions in the electrodes. Thus, electrodes made of a mixture of nanographite and NFC achieved larger capacitances in supercapacitors than electrodes with nanographite only. In addition to electrical properties, NFC enhanced the mechanical stability and wet strength of the electrodes significantly. Furthermore, NFC stabilized the aqueous nanographite dispersions, which improved the processability. Galvanostatic cycling was performed and an initial transient behaviour of the supercapacitors during the first cycles was observed. However, stabilized supercapacitors showed efficiencies of 98–100 %.

Keyword
Graphene, Graphite, Nanofibrillated cellulose, Nanographite, Paper, Supercapacitor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-22579 (URN)10.1002/pssb.201451168 (DOI)000345830900043 ()2-s2.0-84914820272 (Scopus ID)
Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved

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