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Combining operando X-ray scattering and magnetometry to investigate conversion type electrode materials
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.ORCID iD: 0000-0002-4577-0792
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
Abstract [en]

The transition towards a society with full electromobility depends heavily on the battery systems, which raises concerns about the environmental friendliness and sustainability of the current products on the market. Magnetite (Fe3O4) from the conversion type electrode family is one of the promising candidates in the search for a sustainable battery technology owing to its high theoretical storage capacity, high abundance, and low toxicity. However, the material suffers severely from capacity degradation in its practical use and hence requires better understanding and adjustments to reach its full potential.

Developing nanostructured electrode materials is one of the strategies to enhance its storage capacity, stability, and charging rate. Therefore, this thesis starts with synthesis and chemical lithiation of cubic (ferrimagnetic) Fe3O4 nanoparticles that are used as a model system to establish relationships between structural and magnetic properties upon lithiation. The thesis then explores the relationship between particle size, composition, crystal structure, and electrochemical performance of Fe3O4 electrodes via multi-operando techniques during cycles of lithiation and delithiation reactions. Magnetometry, known for its sensitivity to the chemical, compositional, and agglomeration state of the materials was exploited to measure the magnetic signal of the electrodes under operando conditions as a complement to operando SAXS and WAXS measurements. The results from the operando studies indicated that during electrochemi calcycling; LiFeO2, FeO and metallic iron (Fe) are produced as intermediate compounds, but their stability regions differ greatly when using nanoparticles or bulk materials and also when compared against ex-situ analyzed specimens. In addition, commercial micron- and nanosized (paramagnetic) Co3O4 particles were employed to study evolution of structural and magnetic properties over cycles to shed light on the size-dependent reaction kinetics. The obtained results revealed that nanosizing leads to improved electrochemical performance, variations in surface reaction kinetics, and differences in aging mechanisms. The magnetic measurements were crucial in determining surface capacitance reactions that involve gel-like polymeric layer growth and degradation during Li removal and uptake.

Lastly, the magnetic properties of layered NMC-based cathode materials were studied. The differences in their magnetic properties provided important information on the transition metal ordering depending on the choice of synthesis method that is used. Magnetization measurements were used in combination with diffraction data to choose an appropriate structure model to describe actual atomic arrangement in each material. Consequently, the findings in this thesis suggest that (operando) magnetometry can be employed as a complementary tool to elucidate structural details of battery electrodes, potentially revealing insights beyond the detection limits of volume-averaged X-ray scattering techniques.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. , p. 70
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2405
Keywords [en]
Iron oxides, lithium ion batteries, conversion reaction, operando characterization, magnetometry, XRD, SAXS
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:uu:diva-527112ISBN: 978-91-513-2140-0 (print)OAI: oai:DiVA.org:uu-527112DiVA, id: diva2:1853956
Public defence
2024-06-14, Lecture hall Sonja Lyttkens, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2024-05-21 Created: 2024-04-24 Last updated: 2024-05-21
List of papers
1. Elucidating the Lithiation Process in Fe3−δO4 Nanoparticles by Correlating Magnetic and Structural Properties
Open this publication in new window or tab >>Elucidating the Lithiation Process in Fe3−δO4 Nanoparticles by Correlating Magnetic and Structural Properties
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2024 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 16, no 12, p. 14799-14808Article in journal (Refereed) Published
Abstract [en]

Due to their high potential energy storage, magnetite (Fe3O4) nanoparticles have become appealing as anode materials in lithium-ion batteries. However, the details of the lithiation process are still not completely understood. Here, we investigate chemical lithiation in 70 nm cubic-shaped magnetite nanoparticles with varying degrees of lithiation, x = 0, 0.5, 1, and 1.5. The induced changes in the structural and magnetic properties were investigated using X-ray techniques along with electron microscopy and magnetic measurements. The results indicate that a structural transformation from spinel to rock salt phase occurs above a critical limit for the lithium concentration (xc), which is determined to be between 0.5< xc ≤ 1 for Fe3−δO4. Diffraction and magnetization measurements clearly show the formation of the antiferromagnetic LiFeO2 phase. Upon lithiation, magnetization measurements reveal an exchange bias in the hysteresis loops with an asymmetry, which can be attributed to the formation of mosaic-like LiFeO2 subdomains. The combined characterization techniques enabled us to unambiguously identify the phases and their distributions involved in the lithiation process. Correlating magnetic and structural properties opens the path to increasing the understanding of the processes involved in a variety of nonmagnetic applications of magnetic materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
Keywords
iron oxide, lithiation, structural transformation, diffraction, magnetism
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-526226 (URN)10.1021/acsami.3c18334 (DOI)001184842100001 ()38478774 (PubMedID)
Funder
Swedish Research Council, 2016-06959
Available from: 2024-04-05 Created: 2024-04-05 Last updated: 2024-04-24Bibliographically approved
2. Unraveling particle size dependent reaction kinetics in Fe3O4 via operando multi-technique approach
Open this publication in new window or tab >>Unraveling particle size dependent reaction kinetics in Fe3O4 via operando multi-technique approach
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(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Keywords
conversion reaction, particle size, operando, SAXS, WAXS, magnetometry
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-527110 (URN)
Available from: 2024-04-24 Created: 2024-04-24 Last updated: 2024-04-24
3. Identifying intermediaries in conversion-type lithium-ion battery anode materials with operando diffraction and operando magnetization measurements
Open this publication in new window or tab >>Identifying intermediaries in conversion-type lithium-ion battery anode materials with operando diffraction and operando magnetization measurements
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(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-527111 (URN)
Available from: 2024-04-24 Created: 2024-04-24 Last updated: 2024-04-24
4. Synthetic Pathway Determines the Nonequilibrium Crystallography of Li- and Mn-Rich Layered Oxide Cathode Materials
Open this publication in new window or tab >>Synthetic Pathway Determines the Nonequilibrium Crystallography of Li- and Mn-Rich Layered Oxide Cathode Materials
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2021 (English)In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 4, no 2, p. 1924-1935Article in journal (Refereed) Published
Abstract [en]

Li- and Mn-rich layered oxides show significant promise as electrode materials for future Li-ion batteries. However, an accurate description of its crystallography remains elusive, with both single-phase solid solution and multiphase structures being proposed for high performing materials such as Li1.2Mn0.54Ni0.13Co0.13O2. Herein, we report the synthesis of single- and multiphase variants of this material through sol-gel and solid-state methods, respectively, and demonstrate that its crystallography is a direct consequence of the synthetic route and not necessarily an inherent property of the composition, as previously argued. This was accomplished via complementary techniques that probe the bulk and local structure followed by in situ methods to map the synthetic progression. As the electrochemical performance and anionic redox behavior are often rationalized on the basis of the presumed crystal structure, clarifying the structural ambiguities is an important step toward harnessing its potential as an electrode material.

Place, publisher, year, edition, pages
American Chemical Society (ACS)AMER CHEMICAL SOC, 2021
Keywords
Li- and Mn-rich layered oxides, Li-ion battery cathodes, synthesis-structure relationships, anionic redox materials, stacking faulted materials
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-440091 (URN)10.1021/acsaem.0c03027 (DOI)000621660800092 ()
Funder
Swedish Foundation for Strategic Research StandUpSwedish Energy AgencySwedish Research Council, 349-2014-3946Swedish Research Council, 2016-06959
Available from: 2021-04-16 Created: 2021-04-16 Last updated: 2024-04-24Bibliographically approved

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