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A multi-functional electrolyte for lithium-ion batteries

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dc.contributor.authorWesthoff, Kevin A., author
dc.contributor.authorBandhauer, Todd M., advisor
dc.contributor.authorBradley, Thomas H., committee member
dc.contributor.authorPrieto, Amy L., committee member
dc.date.accessioned2016-08-18T23:10:02Z
dc.date.available2016-08-18T23:10:02Z
dc.date.issued2016
dc.description.abstractThermal management of lithium-ion batteries (LIBs) is paramount for multi-cell packs, such as those found in electric vehicles, to ensure safe and sustainable operation. Thermal management systems (TMSs) maintain cell temperatures well below those associated with capacity fade and thermal runaway to ensure safe operation and prolong the useful life of the pack. Current TMSs employ single-phase liquid cooling to the exterior surfaces of every cell, decreasing the volumetric and gravimetric energy density of the pack. In the present study, a novel, internal TMS that utilizes a multi-functional electrolyte (MFE) is investigated, which contains a volatile co-solvent that boils upon heat absorption in small channels in the positive electrode of the cell. The inert fluid HFE-7000 is investigated as the volatile co-solvent in the MFE (1 M LiTFSI in 1:1 HFE-7000/ethyl methyl carbonate by volume) for the proposed TMS. In the first phase of the study, the baseline electrochemical performance of the MFE is determined by conductivity, electrochemical stability window, half and full cell cycling with lithium iron phosphate (LiFePO4), lithium titanate oxide (Li4Ti5O12), and copper antimonide (Cu2Sb), and impedance spectroscopy measurements. The results show that the MFE containing HFE-7000 has comparable stability and cycling performance to a conventional lithium-ion electrolyte (1 M LiPF6 in 3:7 ethylene carbonate/diethyl carbonate by weight). The MFE-containing cells had higher impedance than carbonate-only cells, indicating reduced passivation capability on the electrodes. Additional investigation is warranted to refine the binary MFE mixture by the addition of solid electrolyte interphase (SEI) stabilizing additives. To validate the thermal and electrochemical performance of the MFE, Cu2Sb and LiFePO4 are used in a full cell architecture with the MFE in a custom electrolyte boiling facility. The facility enables direct viewing of the vapor generation within the channel in the positive electrode and characterizes the galvanostatic electrochemical performance. Test results show that the LiFePO4/Cu2Sb cell is capable of operation even when a portion of the more volatile HFE-7000 is continuously evaporated under an extreme heat flux, proving the concept of a MFE. The conclusions presented in this work inform the future development of the proposed internal TMS.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierWesthoff_colostate_0053N_13627.pdf
dc.identifier.urihttp://hdl.handle.net/10217/176599
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.titleA multi-functional electrolyte for lithium-ion batteries
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineMechanical Engineering
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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