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Lithium-intercalated Carbon Fibres : Towards the Realisation of Multifunctional Composite Energy Storage Materials
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lightweight design is a major improvement path for sustainable transport asit contributes to lower vehicles energy consumption and gas emissions. Anovel solution to weight savings is to store energy directly in the mechanicalstructure of the vehicle with a multifunctional material, called structural battery,which could simultaneously bear mechanical loads and store electricalenergy. This is especially possible because the carbon fibre is a high performancemechanical reinforcement for polymer composites and can also be usedas a lithium-intercalating electrode in lithium-ion batteries. In this thesis, theperformance of carbon fibres for use as a lithium-intercalating structural electrodeis investigated.Electrochemical characterisation has shown that intermediate modulus polyacrylonitrile- based carbon fibres which have the highest strength also offerthe most promising electrochemical capacities when compared to other fibregrades with different microstructures. The measured capacity of fibre bundleswas highly dependent on the current rate and at low rate the capacitiesclose to that of graphite electrodes were measured. In a mechanical characterisationthe carbon fibre was not affected by the number of electrochemicalcycles, up to 1000 cycles, but rather by the amount of intercalated lithium.The tensile stiffness appeared to remain unchanged, but during lithation thetensile strength dropped and partly recovered during delithiation due to afirst-cycle irreversible drop. A longitudinal expansion of the carbon fibre wasalso measured during lithiation. An irreversible expansion in the delithiatedfibres highlighted that the first cycle-capacity loss is partly due to intercalatedlithium which is trapped in the carbon fibre. From these results, the carbonfibre is without doubts suitable for structural battery applications.A mechanical-electrochemical coupling in lithium-intercalated carbon fibreswas also measured, highlighting a piezo-electrochemical transducer effect resultingin new functionalities for lithium-intercalated carbon fibres. The longitudinalexpansion strain can be used for mechanical actuation. A responseof the cell open-circuit potential to an applied mechanical strain can be usedfor strain sensing.

Abstract [sv]

Lättviktsdesign är en stor väg till förbättring för hållbara transporter eftersomdet bidrar till lägre energiförbrukning och utsläpp för fordon. Ett ny lösningpå viktbesparing är att lagra energi direkt i den mekaniska fordonskroppenmed ett multifunktionellt material, kallat strukturellt batteri, som samtidigtskulle kunna bära mekaniska belastningar och lagra elektrisk energi. Dettaär möjligt eftersom kolfibrer är en högpresterande mekanisk förstärkningav polymerkompositer och också kan användas för en litium-interkalerandeelektrod i litiumjonbatterier. I denna avhandling har användandet av kolfibrersom en litium-interkalerande strukturell elektrod undersöks.Elektrokemisk karakterisering har visat att mellanmodul-polyakrylnitrilbaseradekolfibrer som har den högsta styrkan även erbjuder de mest lovandeelektrokemiska egenskaperna jämfört med andra fibersorter med annorlundamikrostrukturer. Den uppmätta kapaciteten hos fibrerknippen var starkt beroendeav den aktuella spänningen och vid låg spänning kapaciteter nära denför grafitelektroder mättes. Vid en mekanisk belastning påverkas kolfibrerninte av antalet elektrokemiska cykler, upp till 1000 cykler, utan snarare avmängden interkalerad litium. Dragstyvheten verkade vara oförändrat, menunder litiering sjönk draghållfastheten som dock delvis återhämtade sig efterdelitiering men med en irreversibel förlust efter den första cykeln. Enlängdexpansion av kolfibern mättes under litiering. En irreversibel expansionefter delitiering av fibrer betonade att kapacitetsförlusten efter förstacykeln berodde delvis på interkalerat litium, som är instängt i kolfibrerna.Utifrån dessa resultat är kolfibrer utan tvivel lämpliga för strukturella batteritillämpning.En mekanisk-elektrokemisk koppling i litiuminterkalerade kolfibrer mättesockså, vilket belyser en piezo-elektrokemisk effekt som kan ge nya funktionerför litium-interkalerande kolfibrer. Expansionen kan användas för mekaniskaktivering. Det svaret hos cellpotentialen vid en mekanisk deformation kananvändas för deformationsavkänning.

Place, publisher, year, pages
Stockholm: KTH Royal Institute of Technology, 2014. xi, 61 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2014:07
National Category
Engineering and Technology
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-144323 (URN)978-91-7595-072-3 (ISBN)oai:DiVA.org:kth-144323 (OAI)diva2:712999 (DiVA)
Public defence
2014-05-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Projects
Kombatt
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20140423

Available from2014-04-23 Created:2014-04-17 Last updated:2014-04-23Bibliographically approved
List of papers
1. PAN-based carbon fiber negative electrodes for structural lithium-ion batteries
Open this publication in new window or tab >>PAN-based carbon fiber negative electrodes for structural lithium-ion batteries
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2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 158, no 12, A1455-A1460Article in journal (Refereed) Published
Abstract [en]

Several grades of commercially-available polyacrylonitrile (PAN)-based carbon fibers have been studied for structural lithium-ion batteries to understand how the sizing, different lithiation rates and number of fibers per tow affect the available reversible capacity, when used as both current collector and electrode, for use in structural batteries. The study shows that at moderate lithiation rates, 100 mA g-1, most of the carbon fibers display a reversible capacity close to or above 100 mAh g-1 after ten full cycles. For most of the fibers, removing the sizing increased the capacity to some extent. However, the main factor affecting the measured capacity was the lithiation rate. Decreasing the current by a tenth yielded an increase of capacity of around 100 for all the tested grades. From the measurements performed in this study it is evident that carbon fibers can be used as the active negative material and current collector in structural batteries. © 2011 The Electrochemical Society.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-80613 (URN)10.1149/2.053112jes (DOI)000297979300031 ()2-s2.0-81355132992 (ScopusID)
Funder
TrenOp, Transport Research Environment with Novel PerspectivesStandUpSwedish Foundation for Strategic Research
Note
<p>Source: Scopus. QC 20120210</p>Available from2012-02-10 Created:2012-02-10 Last updated:2014-04-23
2. Impact of electrochemical cycling on the tensile properties of carbon fibres for structural lithium-ion composite batteries
Open this publication in new window or tab >>Impact of electrochemical cycling on the tensile properties of carbon fibres for structural lithium-ion composite batteries
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2012 (English)In: Composites Science And Technology, ISSN 0266-3538, Vol. 72, no 7, 792-798Article in journal (Refereed) Published
Abstract [en]

Carbon fibres are particularly well suited for use in a multifunctional lightweight design of a structural composite material able to store energy as a lithium-ion battery. The fibres will in this case act as both a high performance structural reinforcement and one of the battery electrodes. However, the electrochemical cycling consists of insertions and extractions of lithium ions in the microstructure of carbon fibres and its impact on the mechanical performance is unknown. This study investigates the changes in the tensile properties of carbon fibres after they have been subjected to a number of electrochemical cycles. Consistent carbon fibre specimens were manufactured with polyacrylonitrile-based carbon fibres. Sized T800H and desized IMS65 were selected for their mechanical properties and electrochemical capacities. At the first lithiation the ultimate tensile strength of the fibres was reduced of about 20% but after the first delithiation some strength was recovered. The losses and recoveries of strength remained unchanged with the number of cycles as long as the cell capacity remained reversible. Losses in the cell capacity after 1000 cycles were measured together with smaller losses in the tensile strength of the lithiated fibres. These results show that electrochemical cycling does not degrade the tensile properties which seem to depend on the amount of lithium ions inserted and extracted. Both fibre grades exhibited the same trends of results. The tensile stiffness was not affected by the cycling. Field emission scanning electron microscope images taken after electrochemical cycling did not show any obvious damage of the outer surface of the fibres.

Keyword
Carbon fibres, Hybrid composites, Strength, Mechanical properties, Electrochemical cycling
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-95102 (URN)10.1016/j.compscitech.2012.02.006 (DOI)000302987800005 ()2-s2.0-84858793641 (ScopusID)
Funder
Swedish Foundation for Strategic Research StandUpTrenOp, Transport Research Environment with Novel Perspectives
Note
<p>QC 20120522</p>Available from2012-05-22 Created:2012-05-14 Last updated:2014-04-23
3. Expansion of carbon fibres induced by lithium intercalation for structural electrode applications
Open this publication in new window or tab >>Expansion of carbon fibres induced by lithium intercalation for structural electrode applications
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2013 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 59, 246-254Article in journal (Refereed) Published
Abstract [en]

Carbon fibres (CFs) can work as lightweight structural electrodes in CF-reinforced composites able to store energy as lithium (Li)-ion batteries. The CF has high stiffness and strength-to-weight ratios and a carbonaceous microstructure which enables Li intercalation. An innovative in situ technique for studying the longitudinal expansion of the CF and the relationship with the amount of intercalated Li is described in the present paper. The polyacrylonitrile-based CFs, T800H and unsized IMS65, were chosen for their electrochemical storage capacities. It was found that the CF expands during lithiation and contracts during delithiation. At the first electrochemical cycle, the expansion is partly irreversible which supports that the first-cycle capacity loss partly relates to Li trapped in the CF structure. For the following cycles, the capacity and the expansion are reversible. The expansion, which might relate to tensile stress, increases up to 1% as the measured capacity approaches the theoretical limit of 372 mAh/g for Li storage in graphite. Minor additional expansions due to the uneven distribution of intercalated Li in the CF structure were measured before and after lithiations. Using scanning electron microscope images the transverse expansion of fully lithiated CFs was estimated to about 10% of the cross-section area.

Publisher, range
Elsevier, 2013
Keyword
Ion Batteries, Graphite, Modulus
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-122874 (URN)10.1016/j.carbon.2013.03.015 (DOI)000320489300025 ()2-s2.0-84877692135 (ScopusID)
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilStandUp
Note
<p>QC 20130529</p>Available from2013-05-28 Created:2013-05-28 Last updated:2014-04-23Bibliographically approved
4. The effect of lithium-intercalation on the mechanical properties of carbon fibres
Open this publication in new window or tab >>The effect of lithium-intercalation on the mechanical properties of carbon fibres
2014 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 68, 725-733Article in journal (Refereed) Published
Abstract [en]

Carbon fibres (CFs) can be used as lightweight structural electrodes since they have high specific tensile stiffness and ultimate tensile strength (UTS), and high lithium (Li)-intercalation capability. This paper investigates the relationship between the amount of intercalated Li and the changes induced in the tensile stiffness and UTS of polyacrylonitrile-based CF tows. After a few electrochemical cycles the stiffness was not degraded and independent of the measured capacity. A drop in the UTS of lithiated CFs was only partly recovered during delithiation and clearly larger at the highest measured capacities, but remained less than 40% at full charge. The reversibility of this drop with the C-rate and measured capacity supports that the fibres are not damaged, that some Li is irreversibly trapped in the delithiated CFs and that reversible strains develop in the fibre. However, the drop in the strength does not vary linearly with the measured capacity and the drop in the ultimate tensile strain remains lower than the CF longitudinal expansion at full charge. These results suggest that the loss of strength might relate to the degree of lithiation of defectives areas which govern the tensile failure mode of the CFs.

Keyword
Electrochemical cycle, Lithium Intercalation, Longitudinal expansions, Loss of strength, Reversible strain, Tensile failures, Tensile stiffness, Ultimate tensile strength
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-140797 (URN)10.1016/j.carbon.2013.11.056 (DOI)000330814200074 ()2-s2.0-84891558526 (ScopusID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note
<p>QC 20140203</p>Available from2014-02-03 Created:2014-01-31 Last updated:2014-04-23Bibliographically approved
5. Piezo-electrochemical effect in lithium-intercalated carbon fibres
Open this publication in new window or tab >>Piezo-electrochemical effect in lithium-intercalated carbon fibres
2013 (English)In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 35, 65-67Article in journal (Refereed) Published
Abstract [en]

In this paper we have conducted experiments to investigate the coupling between electrochemical and mechanical properties of lithium (Li)-intercalating carbon fibres (CFs). The results show promising potential for new functionalities of CFs for electrochemical actuation, sensing and energy harvesting. Li-intercalation at 1 C-rate in CFs subjected to a constant tensile extension induced a free reversible longitudinal expansion strain of approximately 0.30% which can be used as mechanical actuation. Varying the tensile extension of lithiated CFs resulted in a piezoelectric response of the open-circuit potential, in the range of several mV, enabling strain sensing. If the electrical potential is kept constant during a tensile extension a piezo-electrochemical current response is found with about 50% mechanical to electrical energy conversion efficiency, enabling energy harvesting.

Publisher, range
Elsevier, 2013
Keyword
Carbon fibres, Electrochemical actuation, Lithium intercalation, Piezo-electrochemical effect, Piezoelectric effect, Lithium-intercalated carbon, Longitudinal expansions, Mechanical actuations, Open-circuit potential, Piezoelectric response, Carbon fibers, Energy conversion, Energy harvesting, Intercalation, Mechanical properties, Piezoelectricity, Lithium
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-133822 (URN)10.1016/j.elecom.2013.07.040 (DOI)000326428800017 ()2-s2.0-84882777828 (ScopusID)
Funder
StandUpSwedish Foundation for Strategic Research Swedish Research Council
Note
<p>QC 20131129</p>Available from2013-11-19 Created:2013-11-11 Last updated:2014-04-23Bibliographically approved
6. Lithium-intercalated Carbon Fibers as Piezo-electrochemical Transducer for Energy Harvesting
Open this publication in new window or tab >>Lithium-intercalated Carbon Fibers as Piezo-electrochemical Transducer for Energy Harvesting
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-144415 (URN)
Note
<p>QS 2014</p>Available from2014-04-23 Created:2014-04-23 Last updated:2014-04-23Bibliographically approved

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