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Depth profiling the solid electrolyte interpahase on lithium titanate (Li4Ti5O12) using synchrotron-based photoelectron spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0003-2538-8104
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
2015 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 294, 173-179 p.Article in journal (Refereed) Published
Abstract [en]

The presence of a surface layer on lithium titanate (Li4Ti6O12, LTO) anodes, which has been a topic of debate in scientific literature, is here investigated with tunable high surface sensitive synchrotron-based photoelectron spectroscopy (PES) to obtain a reliable depth profile of the interphase. Li vertical bar vertical bar LTO cells with electrolytes consisting of 1 M lithium hexafluorophosphate dissolved in ethylene carbonate:diethyl carbonate (LiPF6 in EC:DEC) were cycled in two different voltage windows of 1.0-2.0 V and 1.4-2.0 V. LTO electrodes were characterized after 5 and 100 cycles. Also the pristine electrode as such, and an electrode soaked in the electrolyte were analyzed by varying the photon energies enabling depth profiling of the outermost surface layer. The main components of the surface layer were found to be ethers, P-O containing compounds, and lithium fluoride.

Place, publisher, year, edition, pages
2015. Vol. 294, 173-179 p.
Keyword [en]
Li-ion batteries, LTO, PES, XPS, Surface layer, SEI
National Category
Energy Engineering Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-261214DOI: 10.1016/j.jpowsour.2015.06.038ISI: 000358968400022OAI: oai:DiVA.org:uu-261214DiVA: diva2:852181
Funder
Swedish Energy Agency
Available from: 2015-09-08 Created: 2015-08-31 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Lithium titanate as anode material in lithium-ion batteries: -A surface study
Open this publication in new window or tab >>Lithium titanate as anode material in lithium-ion batteries: -A surface study
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The ever increasing awareness of the environment and sustainability drives research to find new solutions in every part of society. In the transport sector, this has led to a goal of replacing the internal combustion engine (ICE) with an electrical engine that can be powered by renewable electricity. As a battery for vehicles, the Li-ion chemistries have become dominant due to their superior volumetric and gravimetric energy densities. While promising, electric vehicles require further improvements in terms of capacity and power output before they can truly replace their ICE counterparts. Another aspect is the CO2 emissions over lifetime, since the electric vehicle itself presently outlives its battery, making battery replacement necessary. If the lifetime of the battery could be increased, the life-cycle emissions would be significantly lowered, making the electric vehicle an even more suitable candidate for a sustainable society. In this context, lithium titanium oxide (LTO) has been suggested as a new anode material in heavy electric vehicles applications due to intrinsic properties regarding safety, lifetime and availability. The LTO battery chemistry is, however, not fully understood and fundamental research is necessary for future improvements. The scope of this project is to investigate degradation mechanisms in LTO-based batteries to be able to mitigate these and prolong the device lifetime so that, in the end, a suitable chemistry for large scale applications can be suggested. The work presented in this licentiate thesis is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) was applied to determine whether the usage of LTO would prevent anode-side electrolyte decomposition, as suggested from the intercalation potential being inside the electrochemical stability window of common electrolytes. It has been found that electrolyte decomposition indeed occurs, with mostly hydrocarbons of ethers, carboxylates, and some inorganic lithium fluoride as decomposition products, and that this decomposition to some extent ensued irrespective of electrochemical battery operation activity. Second, an investigation into how crossover of manganese ions from Mn-based cathodes influences this interfacial layer has been conducted. It was found, using a combination of high-energy x-ray photoelectron spectroscopy (HAXPES) and near-edge x-ray absorption fine structure (NEXAFS) that although manganese is present on the LTO anode surface when paired with a common manganese oxide spinel cathode, the manganese does little to alter the surface chemistry of the LTO electrode.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. 46 p.
Keyword
titanate battery anode SEI
National Category
Other Chemical Engineering
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-267567 (URN)
Presentation
2015-12-17, Beurlingrummet, Lägerhydsvägen 1, Uppsala, 13:59 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Available from: 2015-11-26 Created: 2015-11-24 Last updated: 2015-11-26Bibliographically approved
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Nordh, TimYounesi, RezaBrandell, DanielEdström, Kristina

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