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Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.ORCID iD: 0000-0002-4303-2585
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
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2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 9, 1-12 p., e0163146Article in journal (Refereed) Published
Abstract [en]

Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC's specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes-Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)-and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost.

Place, publisher, year, edition, pages
2016. Vol. 11, no 9, 1-12 p., e0163146
Keyword [en]
Mass balancing, capacitance, electric double layer capacitor, EDLC, electrode, electrolyte, electrode mass ratio, ion size ratio
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:miun:diva-29083DOI: 10.1371/journal.pone.0163146ISI: 000383893200073Scopus ID: 2-s2.0-84992186879OAI: oai:DiVA.org:miun-29083DiVA: diva2:1033887
Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2017-09-04Bibliographically approved
In thesis
1. Low-Cost, Environmentally Friendly Electric Double-Layer Capacitors: Conept, Materials and Production
Open this publication in new window or tab >>Low-Cost, Environmentally Friendly Electric Double-Layer Capacitors: Conept, Materials and Production
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today’s society is currently performing an exit from fossilfuel energy sources. The change to sustainable alternativesrequires inexpensive and environmentally friendly energy storagedevices. However, most current devices contain expensive,rare or toxic materials. These materials must be replaced bylow-cost, abundant, nontoxic components.In this thesis, I suggest the production of paper-based electricdouble-layer capacitors (EDLCs) to meet the demand oflow-cost energy storage devices that provide high power density.To fulfill the requirements of sustainable and environmentallyfriendly devices, production of EDLCs that consist of paper,graphite and saltwater is proposed. Paper can be used as aseparator between the electrodes and as a substrate for theelectrodes. Graphite is suited for use as an active material in theelectrodes, and saltwater can be employed as an electrolyte.Westudied and developed different methods for the productionof nanographite and graphene from graphite. Composites containingthese materials and similar advanced carbon materialshave been tested as electrode materials in EDLCs. I suggest theuse of cellulose nanofibers (CNFs) or microfibrillated cellulose(MFC) as a binder in the electrodes. In addition to improvedmechanical stability, the nanocellulose improved the stabilityof graphite dispersions and the electrical performance of theelectrodes. The influence of the cellulose quality on the electricalproperties of the electrodes and EDLCs was investigated.The results showed that the finest nanocellulose quality is notthe best choice for EDLC electrodes; MFC is recommended forthis application instead. The results also demonstrated thatthe capacitance of EDLCs can be increased if the electrodemasses are adjusted according to the size of the electrolyte ions.Moreover, we investigated the issue of high contact resistancesat the interface between porous carbon electrodes and metalcurrent collectors. To reduce the contact resistance, graphitefoil can be used as a current collector instead of metal foils.Using the suggested low-cost materials, production methodsand conceptual improvements, it is possible to reduce the material costs by more than 90% in comparison with commercialunits. This confirms that paper-based EDLCs are apromising alternative to conventional EDLCs. Our findings andadditional research can be expected to substantially supportthe design and commercialization of sustainable EDLCs andother green energy technologies.

Abstract [sv]

I dagens samhälle pågår en omställning från användning avfossila energikällor till förnybara alternativ. Denna förändringkräver miljövänliga och kostnadseffektiva elektriska energilagringsenheterför att möjliggöra en kontinuerlig energileverans.Dagens energilagringsenheter innehåller ofta dyra, sällsyntaeller giftiga material som behöver bytas ut för att nå hållbaralösningar.I denna avhandling föreslås att tillverka pappersbaseradesuperkondensatorer som möter kraven för kostnadseffektivaelektriska energilagrare med hög effekttäthet. För att nå kravenpå miljömässigt hållbara enheter föreslås användning avendast papper, grafit och saltvatten. Papper kan användas somseparator mellan elektroder likväl som substrat vid elektrodbestrykning.Grafit kan användas som aktivt elektrodmaterialoch saltvatten fungerar som elektrolyt. Olika metoder har härutvecklats för att producera nanografit och grafen från grafit.Dessa material har tillsammans med liknande, kommersiellt tillgängliga,avancerade kolmaterial testats i elektrodkompositerför superkondensatorer. Som bindemedel i dessa kompositerföreslås nanofibrillerad eller mikrofibrillerad cellulosa. Jaghar demonstrerat att nanocellulosa ökar dispersionsstabilitetensamt förbättrar den mekaniska stabiliteten och dom elektriskaegenskaperna i elektroderna. Hur cellulosans kvalitet påverkarelektroderna har undersökts och visar att den finaste kvaliteteninte är det bästa valet för superkondensatorer, istället rekommenderasmikrofibrillerad cellulosa. Utöver detta demonstrerasmöjligheten att öka superkondensatorernas kapacitans genomatt balansera elektrodernas massa med hänsyn till jonernasstorlek i elektrolyten. I avhandlingen diskuteras även svårigheternamed hög kontaktresistans i gränssnittet mellan porösakolstrukturer och metallfolie och hur detta kan undvikas omgrafitfolie används som kontakt.Genom att använda de material, produktionstekniker ochkonceptförbättringar som föreslås i avhandlingen är det möjligtatt reducera materialkostnaderna med mer än 90% i jämförelsemed kommersiella superkondensatorer. Detta bekräftar att pappersbaserade superkondensatorer är ett lovande alternativoch våra resultat tillsammans med vidare utveckling harstor potential att stödja övergången till miljömässigt hållbarasuperkondensatorer och annan grön energiteknik.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2017. 157 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 267
Keyword
Electric Double-Layer Capacitor, Graphite, Cellulose Nanofibers, Large-Scale, Mass Balancing, Metal-Free
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-31539 (URN)978-91-88527-23-3 (ISBN)
Public defence
2017-09-08, M102, Holmgatan 10, Sundsvall, 10:15 (English)
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 6 inskickat.

At the time of the doctoral defence the following papers were unpublished: paper 6 submitted.

Available from: 2017-09-07 Created: 2017-09-04 Last updated: 2017-09-07Bibliographically approved

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