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Exploring structural carbon fiber composites for mass-less energy and actuation
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.ORCID iD: 0000-0002-1194-9479
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The energy consumption in transport is today a large contributor to global greenhouse emissions. One way of reducing these emissions is by electrification, which is an ongoing journey for the vehicle industry. The aeronautical industry has started investigations but are limited by the relatively low specific energy of batteries.

One way to improve the specific energy of batteries is by making them multifunctional by combining them with other functions of the vehicle. When the battery is combined with a structural material, the resulting material is referred to as a structural battery. This structural battery ultimately performs the fundamental function of mechanical rigidity and the battery function provides almost mass-less energy. The idea of structural batteries has been around for a while, but its actual construction has not yet been understood.

This thesis is focused on exploring the design and implications of structural batteries made from carbon fiber composites. The first section is focused on the construction of the structural battery. Specifically investigating a structural carbon fiber negative electrode with regards to its manufacturing, electrochemical properties and mechanical properties. The results show that the construction of a negative electrode for structural batteries is achievable. The next section is using the findings from the first section in exploring the implications of implementing a structural battery into vehicles with regards to weight saving and life cycle characteristics. The findings show that the structural batteries have the potential to decrease both weight and life cycle burdens. The last section presents the use of the structural carbon fiber negative electrodes as a morphing material controlled by applied electrical power. The morphing deformations are large and stationary when power is removed but the morphing rate of the material is limited. Additionally, it is solid state, lightweight and has an elastic modulus higher than aluminum with large morphing deformations.

The long-term outcomes of a thesis are hard to predict, but the findings herein conclude that the technology of structural batteries have the potential to disrupt energy storage in transportation, as well as traditional actuation and morphing technologies.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. , p. 86
Series
TRITA-SCI-FOU ; 2020:15
National Category
Composite Science and Engineering
Research subject
Aerospace Engineering
Identifiers
URN: urn:nbn:se:kth:diva-273192ISBN: 978-91-7873-552-5 (print)OAI: oai:DiVA.org:kth-273192DiVA, id: diva2:1429398
Public defence
2020-06-03, Live-streaming: https://kth-se.zoom.us/j/64148260640 If you lack computer or computer skills, contact Dan Zenkert, danz@kth.se, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20200512

Available from: 2020-05-12 Created: 2020-05-11 Last updated: 2020-05-26Bibliographically approved
List of papers
1. Structural lithium ion battery electrolytes via reaction induced phase-separation
Open this publication in new window or tab >>Structural lithium ion battery electrolytes via reaction induced phase-separation
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2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 48, p. 25652-25659Article in journal (Refereed) Published
Abstract [en]

For the realization of structural batteries, electrolytes where both higher ionic conductivity and stiffness are combined need to be developed. The present study describes the formation of a structural battery electrolyte (SBE) as a two phase system using reaction induced phase separation. A liquid electrolyte phase is combined with a stiff vinyl ester based thermoset matrix to form a SBE. The effect of monomer structure variations on the formed morphology and electrochemical and mechanical performance has been investigated. An ionic conductivity of 1.5 x 10(-4) S cm(-1), with a corresponding storage modulus (E') of 750 MPa, has been obtained under ambient conditions. The SBEs have been combined with carbon fibers to form a composite lamina and evaluated as a battery half-cell. Studies on the lamina revealed that both mechanical load transfer and ion transport are allowed between the carbon fibers and the electrolyte. These results pave the way for the preparation of structural batteries using carbon fibers as electrodes.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-220591 (URN)10.1039/c7ta04684g (DOI)000417953100058 ()2-s2.0-85038213596 (Scopus ID)
Note

QC 20180117

Available from: 2018-01-17 Created: 2018-01-17 Last updated: 2020-05-11Bibliographically approved
2. Multifunctional performance of a carbon fiber UD lamina electrode for structural batteries
Open this publication in new window or tab >>Multifunctional performance of a carbon fiber UD lamina electrode for structural batteries
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2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 168, p. 81-87Article in journal (Refereed) Published
Abstract [en]

In electric transportation there is an inherent need to store electrical energy while maintaining a low vehicle weight. One way to decrease the weight of the structure is to use composite materials. However, the electrical energy storage in today's systems contributes to a large portion of the total weight of a vehicle. Structural batteries have been suggested as a possible route to reduce this weight. A structural battery is a material that carries mechanical loads and simultaneously stores electrical energy and can be realized using carbon fibers both as a primary load carrying material and as an active battery electrode. However, as yet, no proof of a system-wide improvement by using such structural batteries has been demonstrated. In this study we make a structural battery composite lamina from carbon fibers with a structural battery electrolyte matrix, and we show that this material provides system weight benefits. The results show that it is possible to make weight reductions in electric vehicles by using structural batteries. 

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Carbon fibers, Electrodes, Electrolytes, Vehicles, Battery electrode, Electric transportation, Electrical energy, Electrical energy storages, Mechanical loads, Multifunctional performance, Structural batteries, Weight reduction, Secondary batteries
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-236594 (URN)10.1016/j.compscitech.2018.08.044 (DOI)000452342800010 ()2-s2.0-85053778783 (Scopus ID)
Note

QC 20181126

Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2020-05-11Bibliographically approved
3. Characterization of the adhesive properties between structural battery electrolytes and carbon fibers
Open this publication in new window or tab >>Characterization of the adhesive properties between structural battery electrolytes and carbon fibers
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2020 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 188, article id 107962Article in journal (Refereed) Published
Abstract [en]

Structural batteries can simultaneously store electrical energy and carry mechanical load, being similar to both laminated carbon fiber composites and lithium ion batteries. The matrix in a structural battery must both conduct ions and transfer load between the fibers, made possible with a phase-separated combination of a solid polymer and a liquid electrolyte. This leads to a trade-off between the polymer contact creating adhesion and liquid contact creating ionic conductivity. Here we investigate the fiber-matrix adhesion between carbon fibres with different sizing and two different matrix systems, using microbond testing supported by transverse tensile tests. The results show that the mechanical adhesion of the fiber-matrix interface is lower than that of a commercial non-ion conducting polymer matrix but sufficient for structural battery applications.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2020
Keywords
Functional composites, Carbon fibres, Fibre/matrix bond, Interfacial strength, Scanning electron microscopy (SEM)
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-270887 (URN)10.1016/j.compscitech.2019.107962 (DOI)000515192300014 ()2-s2.0-85077147525 (Scopus ID)
Note

QC 20200325

Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-05-11Bibliographically approved
4. Model of a structural battery and its potential for system level mass savings
Open this publication in new window or tab >>Model of a structural battery and its potential for system level mass savings
2019 (English)In: Multifunctional Materials, ISSN 2399-7532, article id 035002Article in journal (Refereed) Published
Abstract [en]

Structural batteries are materials that can carry mechanical load while storing electrical energy. This is achieved by combining the properties of carbon fiber composites and lithium ion batteries. There are many design parameters for a structural battery and in order to understand their impact and importance, this paper presents a model for multifunctional performance. The mechanical behavior and electrical energy storage of the structural battery are matched to the mechanical behavior of a conventional carbon fiber composite, and the electrical energy storage of a standard lithium ion battery. The latter are both monofunctional and have known performance and mass. In order to calculate the benefit of using structural batteries, the mass of the structural battery is compared to that of the two monofunctional systems. There is often an inverse relationship between the mechanical and electrochemical properties of multifunctional materials, in order to understand these relationships a sensitivity analysis is performed on variables for the structural battery. This gives new insight into the complex multifunctional design of structural batteries.

The results show that it is possible to save mass compared to monofunctional systems but that it depends strongly on the structure it is compared with. With improvements to the design of the structural battery it would be possible to achieve mass saving compared to state-of-the-art composite laminates and lithium ion batteries.

Keywords
multifunctional material, modelling, multifunctional efficiency, weight saving
National Category
Composite Science and Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-258202 (URN)10.1088/2399-7532/ab3bdd (DOI)
Funder
Swedish Research Council Formas, 2017-03898Swedish Research Council Formas, 621-2014-4577VinnovaSwedish Energy AgencyClean Sky 2, 738085
Note

QC 20190917

Available from: 2019-09-10 Created: 2019-09-10 Last updated: 2020-05-11Bibliographically approved
5. Prospective Life Cycle Assessment of a Structural Battery
Open this publication in new window or tab >>Prospective Life Cycle Assessment of a Structural Battery
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2019 (English)In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 20, article id 5679Article in journal (Refereed) Published
Abstract [en]

With increasing interest in reducing fossil fuel emissions, more and more development is focused on electric mobility. For electric vehicles, the main challenge is the mass of the batteries, which significantly increase the mass of the vehicles and limits their range. One possible concept to solve this is incorporating structural batteries; a structural material that both stores electrical energy and carries mechanical load. The concept envisions constructing the body of an electric vehicle with this material and thus reducing the need for further energy storage. This research is investigating a future structural battery that is incorporated in the roof of an electric vehicle. The structural battery is replacing the original steel roof of the vehicle, and part of the original traction battery. The environmental implications of this structural battery roof are investigated with a life cycle assessment, which shows that a structural battery roof can avoid climate impacts in substantive quantities. The main emissions for the structural battery stem from its production and efforts should be focused there to further improve the environmental benefits of the structural battery. Toxicity is investigated with a novel chemical risk assessment from a life cycle perspective, which shows that two chemicals should be targeted for substitution.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
LCA, chemical risk assessment, multifunctional material, environmental engineering, lightweight, prospective
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-265456 (URN)10.3390/su11205679 (DOI)000498398900136 ()2-s2.0-85073981782 (Scopus ID)
Note

QC 20191212

Available from: 2019-12-12 Created: 2019-12-12 Last updated: 2020-05-11Bibliographically approved
6. A residual performance methodology to evaluate multifunctional systems
Open this publication in new window or tab >>A residual performance methodology to evaluate multifunctional systems
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The development of multifunctional materials and structures is receiving increasing interest for many applications and industries; it is a promising way to increase system-wide efficiency and improve the ability to meet environmental targets. However, quantifying the advantages of a multifunctional solution over monofunctional systems can be challenging. One approach is to calculate a reduction in mass, volume or other penalty function. Another approach is to use a multifunctional efficiency metric. However, either approach can lead to results that are unfamiliar or difficult to interpret and implement for an audience without a multifunctional materials or structures background. Instead, we introduce a comparative metric for multifunctional materials that correlates with familiar design parameters for monofunctional materials. This metric allows the potential benefits of the multifunctional system to be understood easily without needing a holistic viewpoint. The analysis is applied to two different examples of multifunctional systems; a structural battery and a structural supercapacitor, demonstrating the methodology and its potential for state-of-the-art structural power materials to offer a weight saving over conventional systems. This metric offers a new way to communicate research on structural power which could help identify and prioritise future research.

National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-273188 (URN)10.1088/2399-7532/ab8e95 (DOI)
Available from: 2020-05-11 Created: 2020-05-11 Last updated: 2020-05-11
7. Shape-morphing carbon fiber composite using electrochemical actuation
Open this publication in new window or tab >>Shape-morphing carbon fiber composite using electrochemical actuation
2020 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 117, no 14, p. 7658-7664Article in journal (Refereed) Published
Abstract [en]

Structures that are capable of changing shape can increase efficiency in many applications, but are often heavy and maintenance intensive. To reduce the mass and mechanical complexity solid-state morphing materials are desirable but are typically nonstructural and problematic to control. Here we present an electrically controlled solid-state morphing composite material that is lightweight and has a stiffness higher than aluminum. It is capable of producing large deformations and holding them with no additional power, albeit at low rates. The material is manufactured from commercial carbon fibers and a structural battery electrolyte, and uses lithium-ion insertion to produce shape changes at low voltages. A proof-of-concept material in a cantilever setup is used to show morphing, and analytical modeling shows good correlation with experimental observations. The concept presented shows considerable promise and paves the way for stiff, solid-state morphing materials.

National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-273191 (URN)10.1073/pnas.1921132117 (DOI)000524486300023 ()32213583 (PubMedID)2-s2.0-85083089857 (Scopus ID)
Note

QC 20200526

Available from: 2020-05-11 Created: 2020-05-11 Last updated: 2020-05-26Bibliographically approved

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