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Inequality of Axial and Radial Diffusion of Inserted Lithium Ions in Carbon Fibres as Revealed by Pulsed-Field Gradient NMR
KTH, Superseded Departments (pre-2005), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, Superseded Departments (pre-2005), Physics.ORCID iD: 0000-0002-0231-3970
KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.ORCID iD: 0000-0001-9203-9313
(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: urn:nbn:se:kth:diva-227304OAI: oai:DiVA.org:kth-227304DiVA, id: diva2:1204232
Funder
Swedish Energy Agency, 37712-1
Note

QC 20180604

Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-04Bibliographically approved
In thesis
1. Carbon Fibres for Multifunctional Lithium-Ion Batteries
Open this publication in new window or tab >>Carbon Fibres for Multifunctional Lithium-Ion Batteries
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:nbn:se:kth:diva-227296 (URN)978-91-7729-763-5 (ISBN)
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

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