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Lithium iron phosphate coated carbon fiber electrodes for structural lithium ion batteries
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.ORCID iD: 0000-0002-2029-4945
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050Article in journal (Refereed) Accepted
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: urn:nbn:se:kth:diva-227292DOI: 10.1016/j.compscitech.2018.04.041OAI: oai:DiVA.org:kth-227292DiVA, id: diva2:1204182
Funder
Swedish Energy Agency, 37712-1
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-05-07
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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