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Supercapacitor electrodes, life cycle assessment of lithium-ion and sodium-ion battery packs : innovation report
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Wellings, Jonathan (2021) Supercapacitor electrodes, life cycle assessment of lithium-ion and sodium-ion battery packs : innovation report. EngD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3861883
Abstract
Transport sits as an essential industry within modern human society, both for industry and communities, although it also sits as one of the greatest contributors to global environmental impacts, which fuels to disastrous changes in our climate. This has encouraged the development of electric vehicles to replace the petrol and diesel vehicles that currently populate the globe’s roads. While this can only be part of a greater effort to reduce emissions from the transport sector, many of the critical technologies used in electric vehicles can also be applicable in other applications, such as with trains and other public transport solutions, alongside stationary energy storage units.
One such technology is the energy storage device used in electric vehicles, with both batteries and supercapacitors being examined in this report, driven by industrial interest from the two sponsor companies of this EngD, Johnson Matthey Plc and Ricardo Plc. While batteries offer high energy capacities but low power outputs within energy storage solutions, supercapacitors offer high power outputs but at the cost of smaller energy capacities in comparison to batteries.
Working with the supercapacitors, different attributes of the electrodes were examined to see how different elements affected their performance, with the binders used, mixing methodologies of the inks and electrode wet thicknesses being looked at in a large number of lab scale tests. This was motivated by the desire of sponsor Johnson Matthey to examine supercapacitor materials and production methods for new innovations. Over 100 cells were made and tested to look at these different attributes. This testing showing that a mixture of Carboxy-Methyl Cellulose (CMC) and Styrene–Butadiene Rubber (SBR) binders offered better specific capacity compared with Poly-Vinylidene DiFluoride (PVDF) binders within an active carbon-based electrode.
The mixing methodologies differed, with one method using a high-speed dispersion mixer and the other using a high torque kneader mixer, with the two methods offered a mix of results. Both varied in how they affected the supercapacitor performance, with one offering benefits over the other depending on the wet thicknesses of each electrode, with the high torque mixing methodology showing better performance at the lower wet thicknesses. The wet thickness investigations suggested there was minimal benefit to increasing wet thicknesses due to the minimal increase in capacity retention compared with the increase in required electrode material. This is also an issue given the higher failure rates the higher thicknesses suffered during testing in comparison to the lower thicknesses. SEM examination eventually determined this was likely due to binder pooling on the surface of the thicker electrodes.
The direction of the degree ultimately led away from supercapacitor research and into research on battery production, with an area of interest being the environmental impacts their production had and how different battery chemistries influenced these impacts. To examine the environmental impacts of different battery chemistries, two models were constructed within openLCA, a dedicated life cycle assessment (LCA) software package for life cycle assessments. One of these models examined a lithium-ion battery pack and the other examined a sodium-ion pack, using information on the production of these packs from literature and including all the processes to produce a 60-kWh capacity pack for use in electric vehicles. The models were encouraged by this project’s sponsor Ricardo PLC, who showed interest in this area and the data that came from these models, which could benefit their operations.
These models showed that the sodium-ion battery packs produced higher environmental impacts than their lithium-ion counterparts, with between 18-65% increases over lithiumion depending on the impact category, with sodium-ion’s lower specific capacity being a primary cause of this.
Producing these models did show issues in the use of the openLCA software, such as complex navigation to find certain values within the model and complexity of exported data, with queries raised on how to improve the user experience within this software. This led to the development of three tools, two which modified the lithium-ion model to allow for different scenarios to be examined, while the other processes the data produced by the model and presented it in a clean and readable manner. This not only needed an understanding of programming languages, with Python ultimately being used, needed to produce the tools but also a wide understanding of the battery manufacturing process, with processes and sources of materials being among the most vital areas to examine. This led to the gathering of a wide set of data, which covered active material inputs, national electricity generation mixes and locations of material production among some of the relevant areas, all of which were needed to fuel the functions of the tools.
These tools offered a range of functions, including changes to distance, electricity and battery chemistry data within the model, alongside data processing of the final data on environmental impacts. These were useful for working with the model and improved how a user interacted with it and its data. They allowed for several beneficial comparisons between changes to the lithium-ion battery model and their impacts, including re-location of key material or production location, as well as changes to the cathode active material. They also improved the speed of locating key impact data for comparisons like these. They also open the door for further tools and improvements, such as operation with other LCA software and an expansion of the databases the tools use.
Item Type: | Thesis (EngD) | ||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering T Technology > TL Motor vehicles. Aeronautics. Astronautics |
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Library of Congress Subject Headings (LCSH): | Electric vehicles -- Batteries, Lithium ion batteries, Sodium ion batteries, Electric batteries -- Electrodes, Supercapacitors -- Materials | ||||
Official Date: | 30 September 2021 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Warwick Manufacturing Group | ||||
Thesis Type: | EngD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Coles, Stuart R. ; Greenwood, David ; Kirwan, Kerry ; Dunn, Julian ; Rosario, Leon ; Cookson, James | ||||
Sponsors: | Ricardo PLC ; Engineering and Physical Sciences Research Council | ||||
Format of File: | |||||
Extent: | xix, 145 pages : illustrations | ||||
Language: | eng |
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