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Large-Scale Graphene Production for Environmentally Friendly and Low-Cost Energy Storage: Production, Coating, and Applications
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (Teknisk Fysik)ORCID iD: 0000-0002-4303-2585
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is great demand for energy-efficient, environmentally sustainable, and cost-effective electrical energy storage devices. One important aspect of this demand is the need for automotive electrification to achieve more energy-efficient transportation at a reasonable cost, thus supporting a fossil-fuel free society. Another important aspect is the requirement for energy storage in the growing field of renewable energy production from wind and solar sources, which generates an irregular supply of electricity due to weather conditions.Much of the research in this area has been conducted in the field of battery technology with impressive results, but the need for rapid storage devices such as supercapacitors is growing. Due to the excellent ability of supercapacitors to handle short peak power pulses with high efficiency along with their long lifetime and superior cyclability, their implementations range from small consumer electronics to electric vehicles and stationary grid applications. Supercapacitors also have the potential to complement batteries to improve pulse efficiency and lifetime of the system, however, the cost of supercapacitors is a significant issue for large-scale commercial use, leading to a demand for sustainable, low-cost materials and simplified manufacturing processes. An important way to address this need is to develop a cost-efficient and environment-friendly large-scale process to produce highly conductive nanographites, such as graphene and graphite nanoplatelets, along with methods to manufacture low-cost electrodes from large area coating.

In this thesis, I present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. The process is based on hydrodynamic tube-shearing and can produce both multilayer graphene and nanometer-thick and micrometer-wide flakes of nanographite. I also describe the production of highly conductive and robust carbon composites based on the addition of nanocellulose during production; these are suitable as electrodes in applications ranging from supercapacitors and batteries to printed electronics and solar cells.Furthermore I demonstrate a scalable route for roll-to-roll coating of the nanographite-nanocellulose electrode material and propose a novel aqueous, low-cost, and metal-free supercapacitor concept with graphite foil functioning as the current collector. The supercapacitors possessedmore than half the specific capacitance of commercial units but achieved a material cost reduction of more than 90 %, demonstrating anenvironment-friendly, low-cost alternative to conventional supercapacitors.

Abstract [sv]

Det finns en stor efterfrågan av energieffektiva, miljömässigt hållbara och kostnadseffektiva elektriska energilagringsenheter. En viktig del av denna efterfrågan kommer från fordonsindustrins behov av elektrifiering, för att uppnå mer energieffektiva fordon till en rimlig kostnad och på så vis bidra till ett fossilfritt samhälle. En annan viktig del är behovet av energilagring för den ökande andelen förnybar energiproduktion från sol- och vindkraft, som genererar elektrisk energi oregelbundet utifrån gällande väderförhållanden. Det pågår mycket forskning inom området för batteriteknik och framgångarna är imponerande men behovet växer också snabbt för snabba energilagrare som exempelvis superkondensatorer. Tack vare superkondensatorernas utmärkta prestanda, när det gäller att hantera korta effektpulser med hög effektivitet tillsammans med dess långa livslängd och överlägsna cyklingsbarhet, sträcker sig applikationerna frånhemelektronik till elfordon och elnätsapplikationer. Superkondensatorer har också potential att komplettera batterier för att uppnå energilagringssystem med ökad pulseffiktivitet och livslängd. Nackdelen är superkondensatorns kostnad, som markant hämmar storskaligkommersialisering, och således kräver utveckling av hållbara och kostnadseffektiva material tillsammans med förenklade tillverkningsmetoder. Ett sätt att lösa detta på, är att utveckla en kostnadseffektiv och miljövänlig process i stor skala för att framställa nanografit med hög elektrisk ledningsförmåga, så som grafén och grafitnanoflak.

I denna avhandling presenterar jag en ny process för att mekaniskt exfoliera grafit till nanografit storskaligt i vattendispersion, med en låg energiåtgång och under kontrollerade skjuvförhållanden. Processen är baserad på hydrodynamisk skjuvning i rör och denproducerar grafen samt nanometertunna och mikrometerbreda flak av nanografit. Som tillägg visar jag också hur robusta kompositer kan tillverkas med hög ledningsförmåga genom att tillsätta nanofibrillerad cellulosa under processen. Dessa kompositer är lämpliga som elektroder i applikationer från superkondensatorer och batterier till tryckt elektronik och solceller.Jag demonstrerar också en skalbar metod för rulle-till-rulle bestrykning av nanografit-nanocellulosa-materialet samt föreslår ett nytt lågkostnads-koncept för metall-fria superkondensatorer med vattenbaserad elektrolyt, där vi använt grafitfolie som kontakt. Superkondensatorerna hade mer än halva den specifika kapacitansen jämfört med kommersiella enheter men materialkostnaden var 90 % lägre, vilket visar på ett miljövänligt lågkostnadsalternativ till konventionella superkondensatorer.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2019. , p. 90
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 297
Keywords [en]
Graphene, Energy storage, Supercapacitors, EDLC
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:miun:diva-36068ISBN: 978-91-88527-99-8 (print)OAI: oai:DiVA.org:miun-36068DiVA, id: diva2:1313051
Public defence
2019-05-10, O102, Holmgatan 10, Sundsvall, 10:15 (English)
Opponent
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 3 (inskickat), delarbete 5 (manuskript).

At the time of the doctoral defence the following papers were unpublished: paper 3 (submitted), paper 5 (manuscript).

Available from: 2019-05-06 Created: 2019-05-02 Last updated: 2019-05-06Bibliographically approved
List of papers
1. 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, p. 2581-2586Article 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 %.

Keywords
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: 2019-05-02Bibliographically approved
2. Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water
Open this publication in new window or tab >>Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water
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2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 4, article id e0154686Article in journal (Refereed) Published
Abstract [en]

The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process.

Place, publisher, year, edition, pages
Nicklas Blomquist, 2016
Keywords
Nano-graphite, Graphite, Graphene, Nanomaterials, Composite materials
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-27600 (URN)10.1371/journal.pone.0154686 (DOI)000375212600060 ()2-s2.0-84966389426 (Scopus ID)
Projects
KEPS
Funder
Swedish Energy Agency
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2019-05-02Bibliographically approved
3. Effects of Geometry on Large-scale Tube-shear Exfoliation of Multilayer Graphene and Nanographite in Water
Open this publication in new window or tab >>Effects of Geometry on Large-scale Tube-shear Exfoliation of Multilayer Graphene and Nanographite in Water
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, no 1, article id 8966Article in journal (Refereed) Published
Abstract [en]

Industrially scalable methods for the production of graphene and other nanographites are needed to achieve cost-efficient commercial products. At present, there are several available routes for the production of these materials but few allow large-scale manufacturing and environmentally friendly low-cost solvents are rarely used. We have previously demonstrated a scalable and low-cost industrial route to produce nanographites by tube-shearing in water suspensions. However, for a deeper understanding of the exfoliation mechanism, how and where the actual exfoliation occurs must be known. This study investigates the effect of shear zone geometry, straight and helical coil tubes, on this system based on both numerical simulation and experimental data. The results show that the helical coil tube achieves a more efficient exfoliation with smaller and thinner flakes than the straight version. Furthermore, only the local wall shear stress in the turbulent flow is sufficient for exfoliation since the laminar flow contribution is well below the needed range, indicating that exfoliation occurs at the tube walls. This explains the exfoliation mechanism of water-based tube-shear exfoliation, which is needed to achieve scaling to industrial levels of few-layer graphene with known and consequent quality.

National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-36084 (URN)10.1038/s41598-019-45133-y (DOI)000472137700062 ()2-s2.0-85067662886 (Scopus ID)
Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-10-16Bibliographically approved
4. Metal-free supercapacitor with aqueous electrolyte and low-cost carbon materials
Open this publication in new window or tab >>Metal-free supercapacitor with aqueous electrolyte and low-cost carbon materials
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 39836Article in journal (Refereed) Published
Abstract [en]

Electric double-layer capacitors (EDLCs) or supercapacitors (SCs) are fast energy storage devices with high pulse efficiency and superior cyclability, which makes them useful in various applications including electronics, vehicles and grids. Aqueous SCs are considered to be more environmentally friendly than those based on organic electrolytes. Because of the corrosive nature of the aqueous environment, however, expensive electrochemically stable materials are needed for the current collectors and electrodes in aqueous SCs. This results in high costs for a given energy-storage capacity. To address this, we developed a novel low-cost aqueous SC using graphite foil as the current collector and a mix of graphene, nanographite, simple water-purification carbons and nanocellulose as electrodes. The electrodes were coated directly onto the graphite foil by using casting frames and the SCs were assembled in a pouch cell design. With this approach, we achieved a material cost reduction of greater than 90% while maintaining approximately one-half of the specific capacitance of a commercial unit, thus demonstrating that the proposed SC can be an environmentally friendly, low-cost alternative to conventional SCs.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
Keywords
Supercapacitor, EDLC, Graphene, Graphite, Nanoparticles
National Category
Composite Science and Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-29827 (URN)10.1038/srep39836 (DOI)000391182900001 ()2-s2.0-85008701942 (Scopus ID)
Funder
Swedish Energy Agency
Note

Published online:05 January 2017

Available from: 2017-01-06 Created: 2017-01-06 Last updated: 2019-05-02Bibliographically approved
5. Influence of Substrate in Slot-die Coating of Nanographite/Nanocelluose Electrodes for Supercapacitors
Open this publication in new window or tab >>Influence of Substrate in Slot-die Coating of Nanographite/Nanocelluose Electrodes for Supercapacitors
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-36085 (URN)
Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-05-06Bibliographically approved

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