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Carbon Fibres for Multifunctional Lithium-Ion Batteries
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.ORCID iD: 0000-0002-2029-4945
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The transportation industry today faces many challenges because of the rapid movement towards electrification. One major challenge is the weight of the battery, which limits the effectiveness of the vehicles. One of the possible routes to reduce the weight on a system-level is introducing structural batteries, batteries that simultaneously storeenergy and hold a mechanical load. Placing these batteries in a load-bearing part of the structure reduces weight and increases effectiveness on a system level. Carbon fibres are especially suited for structural batteries because of the high performance as reinforcement material in a polymer composite, as well as the ability to insert lithium to function as negative electrodes in batteries.

Another field that has attracted attention the latest years is flexible batteries due to the emerging of flexible displays and wearable electronics. Carbon fibres can be a suitable material in flexible batteries due to the good conductivity, mechanical integrity and ability to forman integrated flexible film with cellulose nanofibrils (CNF) as binder.

This thesis focuses on the usage of carbon fibres in structural and flexible batteries. Lignin based and commercial carbon fibres are evaluated as negative electrodes using a combination of electrochemical methods, material characterization and mechanical testing. Further, the diffusion is characterized using nuclear magnetic resonance spectroscopy, revealing an inequality of axial and radial diffusion in carbon fibres. The carbon fibres with a largely disordered structure show most promise as a negative electrode, with a capacity similar to graphite and having a high coulombic efficiency.

Carbon fibres used as current collectors are evaluated as well, both continuous LiFePO4 coated carbon fibres with electrophoretic deposition for structural positive electrode applications and chopped carbonfibres bounded by CNF as a layer in a flexible electrode. The LiFePO4 coated carbon fibres show promise as a structural electrode with moderatecapacity, high coulombic efficiency, good rate performance and good adhesion between fibres and coating. The flexible electrodes with carbon fibres as current collectors perform well with a high capacity, good rate performance, low weight and high flexibility. The electrodes withstand bending for 4000 times without any performance degradation.

Place, publisher, year, edition, pages
Kungliga tekniska högskolan, 2018. , p. 78
National Category
Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-227296ISBN: 978-91-7729-763-5 (print)OAI: oai:DiVA.org:kth-227296DiVA, id: diva2:1204222
Public defence
2018-05-30, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 37712-1
Note

QC 20180507

Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-05-07Bibliographically approved
List of papers
1. High Precision Coulometry of Commercial PAN-Based Carbon Fibers as Electrodes in Structural Batteries
Open this publication in new window or tab >>High Precision Coulometry of Commercial PAN-Based Carbon Fibers as Electrodes in Structural Batteries
2016 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 8, p. A1790-A1797Article in journal (Refereed) Published
Abstract [en]

Carbon fibers have the combined mechanical and electrochemical properties needed to make them particularly well suited for usage as electrodes in a structural lithium-ion battery, a material that simultaneously works as a battery and a structural composite. Presented in this paper is an evaluation of commercial polyacrylonitrile-based carbon fibers in terms of capacity and coulombic efficiency, as well as a microstructural and surface evaluation. Some polyacrylonitrile based carbon fibers intercalate lithium ions, resulting in a similar capacity as state-of-the-art graphite based electrodes, presently the most commonly used negative electrode material. Using high precision coulometry, we found a capacity of around 250-350 mAh/g and a very high coulombic efficiency of over 99.9% after ten cycles, which is even higher than a commercial state-of-the art graphitic electrode evaluated as reference. The high coulombic efficiency is attributed to the very low surface area of the carbon fibers, resulting in a small and stable solid-electrolyte interface layer. A highly graphitized ultra high modulus carbon fiber was evaluated as well and, compared to the other fibers, less lithium was inserted (corresponding to approximately 150 mAh/g). We show that the use of carbon fibers as an electrode material in a structural composite battery is indeed viable.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-190528 (URN)10.1149/2.0041609jes (DOI)000379688000041 ()2-s2.0-84978063168 (Scopus ID)
Funder
Swedish Energy Agency, 37712-1
Note

QC 20160816

Available from: 2016-08-16 Created: 2016-08-12 Last updated: 2018-05-07Bibliographically approved
2. Lignin-based carbon fibers for renewable and multifunctional lithium-ion battery electrodes
Open this publication in new window or tab >>Lignin-based carbon fibers for renewable and multifunctional lithium-ion battery electrodes
Show others...
2018 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 2, p. 81-90Article in journal (Refereed) Published
Abstract [en]

Lignin-based carbon fibers (LCFs) from the renewable resource softwood kraft lignin were synthesized via oxidative thermostabilization of pure melt-spun lignin and carbonization at different temperatures from 1000 degrees C to 1700 degrees C. The resulting LCFs were characterized by tensile testing, scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal Raman spectroscopy. The microstructure is mainly amorphous carbon with some nanocrystalline domains. The strength and stiffness are inversely proportional to the carbonization temperature, while the LCFs carbonized at 1000 degrees C exhibit a strength of 628 MPa and a stiffness of 37 GPa. Furthermore, the application potential of LCFs was evaluated as negative electrodes in a lithium-ion battery (LIB) by electrochemical cycling at different current rates in a half-cell setup. The capacity drops with the carbonization temperature and the LCFs carbonized at 1000 degrees C have a capacity of 335 mAh g(-1). All LCFs showed good cycling stability. Because of the mechanical integrity and conductivity of the LCFs, there is no need to apply current collectors, conductive additives or binders. The advantage is an increased gravimetric energy density compared to graphite, which is the most common negative electrode material. LCFs show a promising multifunctional behavior, including good mechanical integrity, conductivity and an ability to intercalate lithium for LIBs.

Place, publisher, year, edition, pages
Walter de Gruyter, 2018
Keywords
lignin-based carbon fibers, lithium-ion battery, melt-spinning, multifunctional, softwood kraft lignin
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-222403 (URN)10.1515/hf-2017-0044 (DOI)000423540500001 ()2-s2.0-85041645591 (Scopus ID)
Note

QC 20180219

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-05-24Bibliographically approved
3. Lithium iron phosphate coated carbon fiber electrodes for structural lithium ion batteries
Open this publication in new window or tab >>Lithium iron phosphate coated carbon fiber electrodes for structural lithium ion batteries
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2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 162, p. 235-243Article in journal (Refereed) Published
Abstract [en]

A structural lithium ion battery is a material that can carry load and simultaneously be used to store electrical energy. We describe a path to manufacture structural positive electrodes via electrophoretic deposition (EPD) of LiFePO4 (LFP), carbon black and polyvinylidene fluoride (PVDF) onto carbon fibers. The carbon fibers act as load-bearers as well as current collectors. The quality of the coating was studied using scanning electron microscopy and energy dispersive X-ray spectroscopy. The active electrode material (LFP particles), conductive additive (carbon black) and binder (PVDF) were found to be well dispersed on the surface of the carbon fibers. Electrochemical characterization revealed a specific capacity of around 60–110 mAh g−1 with good rate performance and high coulombic efficiency. The cell was stable during cycling, with a capacity retention of around 0.5 after 1000 cycles, which indicates that the coating remained well adhered to the fibers. To investigate the adhesion of the coating, the carbon fibers were made into composite laminae in epoxy resin, and then tested using 3-point bending and double cantilever beam (DCB) tests. The former showed a small difference between coated and uncoated carbon fibers, suggesting good adhesion. The latter showed a critical strain energy release rate of ∼200–600 J m−2 for coated carbon fibers and ∼500 J m−2 for uncoated fibers, which also indicates good adhesion. This study shows that EPD can be used to produce viable structural positive electrodes.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-227292 (URN)10.1016/j.compscitech.2018.04.041 (DOI)000438180500028 ()2-s2.0-85046657191 (Scopus ID)
Funder
Swedish Energy Agency, 37712-1
Note

QC 20180530

Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2019-09-19Bibliographically approved
4. Flexible and lightweight lithium-ion batteries based on cellulose nanofibrils and carbon fibers.
Open this publication in new window or tab >>Flexible and lightweight lithium-ion batteries based on cellulose nanofibrils and carbon fibers.
(English)In: Journal of Power SourcesArticle in journal (Other academic) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-205656 (URN)
Note

QC 20170421

Available from: 2017-04-21 Created: 2017-04-21 Last updated: 2018-05-07Bibliographically approved
5. Li4Ti5O12 flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries
Open this publication in new window or tab >>Li4Ti5O12 flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries
2017 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 39, p. 140-150Article in journal (Refereed) Published
Abstract [en]

TEMPO oxidized cellulose nanofibrils (TOCNF) were used as binder material to prepare bendable Li4Ti5O12 (LTO) electrodes. Carbon fiber (CF) layers were integrated as current collectors to enhance the mechanical properties and to increase the specific energy of the electrodes. These electrodes combined with CF current collectors (LTO/CF) show good electrochemical properties and are flexible, sustainable, mechanical and chemical stable, lightweight and produced by a water-based easy filtration process. An increase of the active material weight (LTO) from around 19% to 71% of the electrode and current collector combined weight is demonstrated with CF compared with a copper current collector. Additionally, preparation of the current collector material is non-expensive, quick and easy compared to that of carbon nanotube or graphene. To test the flexible battery application, 4000 times repeated bending was carried out on both the LTO electrodes and the LTO/CF electrodes. This had no significant effect on the morphology, mechanical and electrochemical properties of neither the LTO nor the LTO/CF electrodes. Addition of the CF layer improves the mechanical properties and specific capacity of the LTO-electrode. A thicker LTO electrode with only 2 wt% TOCNF is demonstrated which is promising for thicker electrodes with high energy density. A full cell was assembled with the LTO/CF as negative electrode and LiFePO4 (LFP)/CF as positive, which exhibited a stable cycling performance and good energy density.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Carbon fiber current collector, Flexible lithium ion batteries, Li4Ti5O12 electrodes, Lightweight, TEMPO-oxidized CNF, Water-based binder
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-212239 (URN)10.1016/j.nanoen.2017.06.043 (DOI)000408878200014 ()2-s2.0-85021718504 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Energy Agency, 37712-1
Note

QC 20170822

Available from: 2017-08-22 Created: 2017-08-22 Last updated: 2019-12-20Bibliographically approved
6. Inequality of Axial and Radial Diffusion of Inserted Lithium Ions in Carbon Fibres as Revealed by Pulsed-Field Gradient NMR
Open this publication in new window or tab >>Inequality of Axial and Radial Diffusion of Inserted Lithium Ions in Carbon Fibres as Revealed by Pulsed-Field Gradient NMR
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Nuclear Magnetic Resonance (NMR) studies has characterized lithiated polyacrylonitrile-based carbon fibres. The local dynamics has been probed by spin-lattice and spin-spin relaxation measurements and long range motion (diffusion) by pulsed field gradient NMR. Differences in fibre orientation was investigated by axially and radially aligned samples. One single peak related to lithium insertion was observed around 12-25 ppm, increasing with lithium load. A small effect of fibre orientation was observed on the relaxation behavior. The diffusion though was found to be around three times higher in axial compared to radial direction of the carbon fibres. This is believed to be due to the microstructure, with oriented crystallites along the carbon fibres contributing more in the axial direction to the average measured diffusion. The diffusion coefficients varied from around 10-12 m2/s to 4·10-12 m2/s, increasing with lithium load.

National Category
Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-227304 (URN)
Funder
Swedish Energy Agency, 37712-1
Note

QC 20180604

Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-04Bibliographically approved

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Output format
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