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Structural and Electrochemical Relations in Electrode Materials for Rechargeable Batteries
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala universitet.ORCID iD: 0000-0001-8739-4054
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rechargeable batteries have already conquered the market of portable electronics (i.e., mobile phones and laptops) and are set to further enable the large-scale deployment of electric vehicles and hybrid electric vehicles in a not too distant future. In this context, a deeper understanding of the fundamental processes governing the electrochemical behavior of electrode materials for batteries is required for further development of these applications. The aims of the work described in this thesis have been to investigate how electrochemical properties and structural properties of novel electrode materials relate to each other. In this sense, electrochemical characterization, structural analysis using XRD and their combined simultaneous use via in operando XRD experiments have played a crucial part.

The investigations showed that: Two oxohalides, Ni3Sb4O6F6 and Mn2Sb3O6Cl, react with Li-ions in a complex manner involving different types of reaction mechanisms at low voltages in Li half cells. In operando XRD show that both of these materials are reduced in a conversion reaction via an in situ formation of nanocomposites, which proceed to react reversibly with Li-ions in a combination of alloying and conversion reactions.

Carbon-coated Na2Mn2Si2O7 was synthesized and characterized as a possible positive electrode material for non-aqueous Na-ion batteries. DFT calculations point to a structural origin of the modest electrochemical behavior of this material. It is suggested that structural rearrangements upon desodiation are associated with large overpotentials.

It is demonstrated via an in operando synchrotron XRD study that Fe(CN)6 vacancies in copper hexacyanoferrate (CuHCF) play an important role in the electrochemical behavior toward Zn2+ in an aqueous CuHCF/Zn cell. Furthermore, manganese hexacyanomanganate (MnHCM) is shown to react reversibly with Li+, Na+ and K+ in non-aqueous alkali metal half cells. In contrast to CuHCF, which is a zero-strain material, MnHCM undergoes a series of structural transitions (from monoclinic to cubic) during electrochemical cycling.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1599
Keyword [en]
batteries, electrochemical energy storage, oxohalides, conversion, alloy, pyrosilicate, CuHCF, MnHCM, XRD, XANES, in operando
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-334078ISBN: 978-91-513-0155-6 (print)OAI: oai:DiVA.org:uu-334078DiVA, id: diva2:1158660
Public defence
2018-01-12, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-12-21 Created: 2017-11-20 Last updated: 2018-03-08
List of papers
1. Ni3Sb4O6F6 and Its Electrochemical Behavior toward Lithium-A Combination of Conversion and Alloying Reactions
Open this publication in new window or tab >>Ni3Sb4O6F6 and Its Electrochemical Behavior toward Lithium-A Combination of Conversion and Alloying Reactions
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2016 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 18, p. 6520-6527Article in journal (Refereed) Published
Abstract [en]

A group of oxohalides, where Ni3Sb4O6F6 is one example, has been investigated with respect to its electrochemical reactions toward Li+/Li. In situ and ex situ XRD measurements reveal that the original structure collapses and the material becomes amorphous upon insertion of Li at low potentials versus Li+/Li. With continued cycling, a nanocrystalline phase of NiSb, which reacts reversibly with Li, appears and steadily grows more stable. Electrochemical experiments (i.e., chronopotentiometry and cyclic voltammetry) show that multiple reactions of both conversion- and alloying-type are active in the system. High storage capacities are achieved initially but with rapid fading as a consequence of a limited reversibility of the Ni2+/Ni redox process, as shown by X-ray absorption spectroscopy of the first discharge/charge cycle. Stable cycling can be achieved by optimizing the cutoff potentials (i.e., excluding poorly reversible reactions at high and low voltages, respectively), yielding long-term cycling with a practical gravimetric capacity of similar to 200 mAh g(-1).

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-307284 (URN)10.1021/acs.chemmater.6b01914 (DOI)000384399000015 ()
Funder
Swedish Research Council, 2011-6512
Available from: 2016-11-11 Created: 2016-11-11 Last updated: 2017-11-29Bibliographically approved
2. Investigation of the Structural and Electrochemical Properties of Mn2Sb3O6CI upon Reaction with Li Ions
Open this publication in new window or tab >>Investigation of the Structural and Electrochemical Properties of Mn2Sb3O6CI upon Reaction with Li Ions
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 11, p. 5949-5958Article in journal (Refereed) Published
Abstract [en]

The structural and electrochemical properties of a quaternary layered compound with elemental composition Mn2Sb3O6Cl have been investigated upon reaction with lithium in Li half cells. Operando XRD was used to investigate the potential impact of this particular layered structure on the lithiation process. Although the results suggest that the material is primarily reacted through a conventional conversion mechanism, they also provide some hints that the space between the slabs may act as preferential entry points for lithium ions but not for the larger sodium ions. Cyclic voltammetry, galvanostatic cycling, HRTEM, SAED, and EELS analyses were performed to unravel the details of the reaction mechanism with the lithium ions. It is found that two pairs of reactions are mainly responsible for the reversible electrochemical cycling of this compound, namely, the alloying of Li-Sb and the conversion of MnxOy to metallic Mn with concomitant formation of Li2O upon lithium uptake. A moderate cycling stability is achieved with a gravimetric capacity of 467 mAh g(-1) after 100 cycles between 0.05 and 2.2 V vs Li+/Li despite the large particle sizes of the active material and its nonoptimal inclusion into composite coatings. The electrochemical activity of the title compound was also tested in Na half cells between 0.05 and 2 V vs Ne/Na. It was found that a prolonged period of electrochemical milling is required to fully gain access to the active material, after which the cell delivers a capacity of 350 mAh CI. These factors are demonstrated to clearly limit the ultimate performances for these electrodes.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Nano Technology Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-320200 (URN)10.1021/acs.jpcc.6b13092 (DOI)000397546300011 ()
Funder
Swedish Research Council, 2011-6512Swedish Research Council Formas, 245-2014-668Knut and Alice Wallenberg FoundationStandUp
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-12-30
3. Manganese Pyrosilicates as Novel Positive Electrode Materials for Na-Ion Batteries
Open this publication in new window or tab >>Manganese Pyrosilicates as Novel Positive Electrode Materials for Na-Ion Batteries
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A carbon-coated pyrosilicate, Na2Mn2Si2O7/C, was synthesized and characterized for use as a new positive-electrode material for sodium ion batteries. The material consists of primary 20-80 nm particles embedded in a ≈10 nm-thick conductive carbon matrix. Reversible insertion of Na+ ions is clearly demonstrated with ≈25% of its theoretical capacity (165 mAh/g) accessible at room temperature at a low cycling rate. The material yields an average potential of 3.3 V vs. Na+/Na on charge and 2.2 V on discharge. DFT calculations predict an equilibrium potential for Na2Mn2Si2O7 in the range of 2.8-3.0 V vs. Na+/Na, with a possibility of a complete flip in the connectivity of neighboring Mn-polyhedra – from edge-sharing to disconnected and vice versa. This significant rearrangement in Mn coordination  (≈2 Å) and large volume contraction (>10%) could explain our inability to fully desodiate the material, and illustrates well the need for a new electrode design strategy beyond the conventional “down-sizing/coating” procedure.

National Category
Inorganic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:uu:diva-334063 (URN)
Funder
StandUp
Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2018-01-08
4. Structural-electrochemical relations in the aqueous copper hexacyanoferrate-zinc system examined by synchrotron X-ray diffraction
Open this publication in new window or tab >>Structural-electrochemical relations in the aqueous copper hexacyanoferrate-zinc system examined by synchrotron X-ray diffraction
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2017 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 369, p. 146-153Article in journal (Refereed) Published
Abstract [en]

The storage process of Zn2+ in the Prussian blue analogue (PBA) copper hexacyanoferrate (Cu[Fe(CN)6]2/3-nH2O - CuHCF) framework structure in a context of rechargeable aqueous batteries is examined by means of in operando synchrotron X-ray diffraction. Via sequential unit-cell parameter refinements of time-resolved diffraction data, it is revealed that the step-profile of the cell output voltage curves during repeated electrochemical insertion and removal of Zn2+ in the CuHCF host structure is associated with a non-linear contraction and expansion of the unit-cell in the range 0.36 < x < 1.32 for Znx/3Cu[Fe(CN)6]2/3-nH2O. For a high insertion cation content there is no apparent change in the unit-cell contraction. Furthermore, a structural analysiswith respect to the occupancies of possible Zn2+ sites suggests that the Fe(CN)6 vacancies within the CuHCF framework play an important role in the structural-electrochemical behavior of this particular system. More specifically, it is observed that Zn2+ swaps position during electrochemical cycling, hopping between cavity sites to vacant ferricyanide sites.

Keyword
Prussian blue analogues, Copper hexacyanoferrate, Zinc, Aqueous electrochemical energy storage, In operando X-ray diffraction, Synchrotron radiation
National Category
Inorganic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:uu:diva-334062 (URN)10.1016/j.jpowsour.2017.09.079 (DOI)000413799900018 ()
Funder
Swedish Research Council, 2011-6512Swedish Research Council Formas, 245-2014-668
Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2018-02-05Bibliographically approved
5. A comparative study of manganese hexacyanomanganate as a positive electrode for non-aqueous Li-, Na- and K-ion batteries
Open this publication in new window or tab >>A comparative study of manganese hexacyanomanganate as a positive electrode for non-aqueous Li-, Na- and K-ion batteries
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(English)Manuscript (preprint) (Other academic)
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-334075 (URN)
Funder
StandUp
Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-12-30

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