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Synthetic Pathway Determines the Nonequilibrium Crystallography of Li- and Mn-Rich Layered Oxide Cathode Materials
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0001-8148-8615
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0002-4577-0792
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0001-9304-8975
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.ORCID iD: 0000-0003-1874-932x
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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
AMER CHEMICAL SOC American Chemical Society (ACS), 2021. Vol. 4, no 2, p. 1924-1935
Keywords [en]
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: urn:nbn:se:uu:diva-440091DOI: 10.1021/acsaem.0c03027ISI: 000621660800092OAI: oai:DiVA.org:uu-440091DiVA, id: diva2:1544970
Funder
Swedish Foundation for Strategic Research StandUpSwedish Energy AgencySwedish Research Council, 349-2014-3946Swedish Research Council, 2016-06959Available from: 2021-04-16 Created: 2021-04-16 Last updated: 2024-04-24Bibliographically approved
In thesis
1. Synthesis–Structure–Property Relationships in Li- and Mn-rich Layered Oxides
Open this publication in new window or tab >>Synthesis–Structure–Property Relationships in Li- and Mn-rich Layered Oxides
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The commercialisation of Li-ion batteries over the last decade has provided additional impetus for the improvement of existing energy storage technologies. Towards this, a major portion of the global efforts includes exploratory research aimed at the development of new material chemistries. Aligning with this theme, this Thesis explores the synthesis–structure–property relationships in Li- and Mn-rich layered oxides, a cost-effective high-capacity material system that shows promise as a positive electrode material for future Li-ion batteries. The compositional and crystallographic diversity of Li- and Mn-rich layered oxides make them particularly susceptible to synthesis-dependent variations and exacerbates structural characterisation. Therefore, understanding how synthetic variations influence their structural and electrochemical properties is a crucial step in realising their potential as positive electrode materials.

Even for simple compositions like Li2MnO3, dissimilar crystallographic ordering and particle morphologies are produced depending on whether a solid-state or sol-gel synthesis approach was implemented. Subsequently, due to the higher degree of structural disorder and larger surface area, the sol-gel sample exhibited higher initial electrochemical capacities. The structural features present in these compounds such as cation site-mixing and stacking faults, manifest over varying crystallographic regimes. Hence, complementary characterisation techniques that probe different structural length scales are necessary for an accurate structural characterisation of these compounds. This factor, together with their complex crystallography, have led to contradictory single- and multi-phase structure models being reported for complex Li- and Mn-rich layered oxides. By using a combination of diffraction, spectroscopic techniques and magnetic measurements it was discovered that Li1.2Mn0.54Ni0.13Co0.13O2 can exist in both single- and multi-phase structural forms if synthesised through sol-gel and solid-state methods, respectively. Further studies following the same theme revealed that when synthesised under common laboratory conditions these compounds are metastable. Here, the composition and synthesis play a critical role in the thermodynamic and kinetic factors affecting the resultant phase, domain structure and degree of cationic order. Finally, to encompass all the structural features contained in Li- and Mn-rich layered oxides, a supercell-based structure model for Li- and Mn-rich layered oxides, using Li1.2Mn0.6Ni0.2O2 as an example, is presented. Summing all the work together from the thesis, a critical evaluation of commonly used characterisation techniques is also provided as a guideline for future research in this field.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2021. p. 85
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2048
Keywords
Li- and Mn-rich layered oxides, Li-ion battery cathode materials, synthesis–property relationships, stacking faults, anionic redox materials
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-440399 (URN)978-91-513-1220-0 (ISBN)
Public defence
2021-06-14, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2021-05-24 Created: 2021-04-22 Last updated: 2021-06-21
2. Combining operando X-ray scattering and magnetometry to investigate conversion type electrode materials
Open this publication in new window or tab >>Combining operando X-ray scattering and magnetometry to investigate conversion type electrode materials
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
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
Iron oxides, lithium ion batteries, conversion reaction, operando characterization, magnetometry, XRD, SAXS
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-527112 (URN)978-91-513-2140-0 (ISBN)
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

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Menon, Ashok S.Ulusoy, SedaOjwang, Dickson O.Riekehr, LarsSalazar-Alvarez, GermanSvedlindh, PeterEdström, KristinaGómez, Cesar PayBrant, William

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