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Källquist, I., Naylor, A. J., Baur, C., Chable, J., Kullgren, J., Fichtner, M., . . . Hahlin, M. (2019). Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes. Chemistry of Materials, 31(16), 6084-6096
Open this publication in new window or tab >>Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 16, p. 6084-6096Article in journal (Refereed) Published
Abstract [en]

The increased energy density in Li-ion batteries is particularly dependent on the cathode materials that so far have been limiting the overall battery performance. A new class of materials, Li-rich disordered rock salts, has recently been brought forward as promising candidates for next-generation cathodes because of their ability to reversibly cycle more than one Li-ion per transition metal. Several variants of these Li-rich cathode materials have been developed recently and show promising initial capacities, but challenges concerning capacity fade and voltage decay during cycling are yet to be overcome. Mechanisms behind the significant capacity fade of some materials must be understood to allow for the design of new materials in which detrimental reactions can be mitigated. In this study, the origin of the capacity fade in the Li-rich material Li2VO2F is investigated, and it is shown to begin with degradation of the particle surface that spreads inward with continued cycling.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-394265 (URN)10.1021/acs.chemmater.9b00829 (DOI)000483435400005 ()
Funder
Swedish Research Council, 2016-03545EU, Horizon 2020, 711792EU, Horizon 2020, 730872StandUpSwedish National Infrastructure for Computing (SNIC)
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-09Bibliographically approved
Massel, F., Hikima, K., Rensmo, H., Suzuki, K., Hirayama, M., Xu, C., . . . Duda, L. (2019). Excess lithium in transition metal layers of epitaxially grown thin film cathodes of Li2MnO3 leads to rapid loss of covalency during first battery cycle. The Journal of Physical Chemistry C, 123(47), 28519-28526
Open this publication in new window or tab >>Excess lithium in transition metal layers of epitaxially grown thin film cathodes of Li2MnO3 leads to rapid loss of covalency during first battery cycle
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 47, p. 28519-28526Article in journal (Refereed) Published
Abstract [en]

We have investigated the initial-cycle battery behavior of epitaxial thin films of Li2MnO3-cathodes by employing resonant inelastic X-ray scattering (RIXS) at the O K- and Mn L3-edges. Thin films (25 nm thickness) with Li/Mn-ratios of 2.06 (stoichiometric) and 2.27 (over-stoichiometric), respectively, were epitaxially grown by pulsed laser deposition and electrochemically cycled as battery cathodes in half-cell setup, stopped at potentials for full charge (delithiation) and complete discharge (relithiation), respectively, for X-ray analysis. Using RIXS, we find that significant anionic reactions take place in both materials upon initial delithiation. However, no signatures of localized oxygen holes are found in O K-RIXS of the Li2MnO3 regardless of Li/Mn-ratio. Instead, the top of the oxygen valence band is depleted of electrons forming delocalized empty states upon delithiation. Mn L-RIXS of the over-stoichiometric cathode material shows a progressive loss of charge transfer state intensity during the first battery cycle, revealing a more rapid loss of Mn--O covalency in the over-stoichiometric material.

Keywords
Li-ion battery, Li-rich lithium manganese oxide cathode, pulsed laser deposition (PLD), thin film, resonant inelastic X-ray scattering (RIXS), soft X-ray absorption spectroscopy (XAS)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390620 (URN)10.1021/acs.jpcc.9b06246 (DOI)000500417600001 ()
Funder
Swedish Research Council, 2014-6019Swedish Research Council, 2016-03545Swedish Research Council, 2018-06465StandUpSwedish Energy Agency, 40495-1
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-12-20Bibliographically approved
Baur, C., Källquist, I., Chable, J., Chang, J. H., Johnsen, R. E., Ruiz-Zepeda, F., . . . Fichtner, M. (2019). Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes. Journal of Materials Chemistry A, 7(37), 21244-21253
Open this publication in new window or tab >>Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 37, p. 21244-21253Article in journal (Refereed) Published
Abstract [en]

Lithium-rich transition metal disordered rock salt (DRS) oxyfluorides have the potential to lessen one large bottleneck for lithium ion batteries by improving the cathode capacity. However, irreversible reactions at the electrode/electrolyte interface have so far led to fast capacity fading during electrochemical cycling. Here, we report the synthesis of two new Li-rich transition metal oxyfluorides Li2V0.5Ti0.5O2F and Li2V0.5Fe0.5O2F using the mechanochemical ball milling procedure. Both materials show substantially improved cycling stability compared to Li2VO2F. Rietveld refinements of synchrotron X-ray diffraction patterns reveal the DRS structure of the materials. Based on density functional theory (DFT) calculations, we demonstrate that substitution of V3+ with Ti3+ and Fe3+ favors disordering of the mixed metastable DRS oxyfluoride phase. Hard X-ray photoelectron spectroscopy shows that the substitution stabilizes the active material electrode particle surface and increases the reversibility of the V3+/V5+ redox couple. This work presents a strategy for stabilization of the DRS structure leading to improved electrochemical cyclability of the materials.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-396724 (URN)10.1039/c9ta06291b (DOI)000489345300018 ()
Funder
EU, Horizon 2020, 711792EU, Horizon 2020, 730872
Available from: 2019-12-05 Created: 2019-12-05 Last updated: 2019-12-12Bibliographically approved
Maibach, J., Källquist, I., Andersson, M., Urpelainen, S., Edström, K., Rensmo, H., . . . Hahlin, M. (2019). Probing a battery electrolyte drop with ambient pressure photoelectron spectroscopy. Nature Communications, 10, Article ID 3080.
Open this publication in new window or tab >>Probing a battery electrolyte drop with ambient pressure photoelectron spectroscopy
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 3080Article in journal (Refereed) Published
Abstract [en]

Operando ambient pressure photoelectron spectroscopy in realistic battery environments is a key development towards probing the functionality of the electrode/electrolyte interface in lithium-ion batteries that is not possible with conventional photoelectron spectroscopy. Here, we present the ambient pressure photoelectron spectroscopy characterization of a model electrolyte based on 1M bis(trifluoromethane)sulfonimide lithium salt in propylene carbonate. For the first time, we show ambient pressure photoelectron spectroscopy data of propylene carbonate in the liquid phase by using solvent vapor as the stabilizing environment. This enables us to separate effects from salt and solvent, and to characterize changes in electrolyte composition as a function of probing depth. While the bulk electrolyte meets the expected composition, clear accumulation of ionic species is found at the electrolyte surface. Our results show that it is possible to measure directly complex liquids such as battery electrolytes, which is an important accomplishment towards true operando studies.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390789 (URN)10.1038/s41467-019-10803-y (DOI)000475295300002 ()31300638 (PubMedID)
Funder
Swedish Research Council, 2016-03545Swedish Research Council, 2012-4681Swedish Research Council, 2014-6019Swedish Research Council, 2018-06465Swedish Energy Agency, 40495-1StandUpCarl Tryggers foundation
Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-15Bibliographically approved
Naylor, A. J., Maibach, J., Källquist, I., Makkos, E., Roberts, M., Younesi, R., . . . Edström, K. (2018). Energy-tuned photoelectron spectroscopy of lithium-ion battery cathodes: revealing oxygen redox activity and investigating new materials. In: ECS Meeting Abstracts MA2018-02 AiMES 2018 Meeting: . Paper presented at ECS AiMES 2018. Cancun, Mexico, September 30 – October 4, 2018..
Open this publication in new window or tab >>Energy-tuned photoelectron spectroscopy of lithium-ion battery cathodes: revealing oxygen redox activity and investigating new materials
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2018 (English)In: ECS Meeting Abstracts MA2018-02 AiMES 2018 Meeting, 2018Conference paper, Oral presentation with published abstract (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-374701 (URN)
Conference
ECS AiMES 2018. Cancun, Mexico, September 30 – October 4, 2018.
Available from: 2019-01-23 Created: 2019-01-23 Last updated: 2019-01-24Bibliographically approved
Ottosson, M., Boman, M., Berastegui, P., Andersson, Y., Hahlin, M., Korvela, M. & Berger, R. (2018). Response to the comments by P. Szakalos, T. angstrom kermark and C. Leygraf on the paper "Copper in ultrapure water, a scientific issue under debate" [Letter to the editor]. Corrosion Science, 142, 308-311
Open this publication in new window or tab >>Response to the comments by P. Szakalos, T. angstrom kermark and C. Leygraf on the paper "Copper in ultrapure water, a scientific issue under debate"
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2018 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 142, p. 308-311Article in journal, Letter (Other academic) Published
Keywords
Copper, XPS, AES, Oxidation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-366387 (URN)10.1016/j.corsci.2018.02.003 (DOI)000444933400030 ()
Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2018-11-21Bibliographically approved
Massel, F., Ahmadi, S., Hahlin, M., Liu, Y.-S., Guo, J.-H., Edvinsson, T., . . . Duda, L. (2018). Transition metal doping effects in Co-phosphate catalysts for water splitting studied with XAS. Journal of Electron Spectroscopy and Related Phenomena, 3-7
Open this publication in new window or tab >>Transition metal doping effects in Co-phosphate catalysts for water splitting studied with XAS
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2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, p. 3-7Article in journal (Refereed) Published
Abstract [en]

Metal oxides as oxygen evolution reaction (OER) catalysts for water splitting are ubiquitous in research and application. Pure and doped (or hybrid) Co oxide systems are of particular interest due to their good efficiency. However, the electronic effects of different dopants are still unclear in many of these systems. We present a study of doped Co-phosphate (P-i) films deposited electrochemically from aqueous solutions of neutral pH using an X-ray absorption spectroscopy (XAS), a technique that can reveal important information about catalytically active states. These hybrid films, obtained from solutions containing both Co ions and another transition metal (TM) ion (TM = Mn, Fe, Ni), were analyzed with XAS at the TM L-edges and the O K-edge. We find that a large concentration of Co3+-ions in the films and a low-lying edge of the O 2p conduction band (CB) are good indicators for the OER efficiency of the films. Our results show that native Co-P-i is close to optimal for the OER activity at low deposition potential. However, Mn- and Ni-doped systems have promising properties when deposited at higher potentials because these ions tend to stabilize the Co3+-state in the films as well as the position of the O 2p-edge CB (a few tenths of 1 eV), in contrast to native Co-Pi films.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
X-ray absorption spectroscopy, Catalysis, Oxygen evolution reaction, Co-, K-edge, TM L-edge
National Category
Nano Technology Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-336539 (URN)10.1016/j.elspec.2017.09.012 (DOI)000428825400002 ()
Funder
Swedish Research Council
Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2018-06-07Bibliographically approved
Lindgren, F., Rehnlund, D., Källquist, I., Nyholm, L., Edström, K., Hahlin, M. & Maibach, J. (2017). Breaking Down a Complex System: Interpreting PES Peak Positions for Cycled Li-ion Battery Electrodes. The Journal of Physical Chemistry C, 121, 27303-27312
Open this publication in new window or tab >>Breaking Down a Complex System: Interpreting PES Peak Positions for Cycled Li-ion Battery Electrodes
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, p. 27303-27312Article in journal (Refereed) Published
Abstract [en]

Photoelectron spectroscopy (PES) is an important technique for tracing and understanding the side reactions responsible for decreasing performance of Li-ion batteries. Interpretation of different spectral components is dependent on correct binding energy referencing and for battery electrodes this is highly complex. In this work, we investigate the effect on binding energy reference points in PES in correlation to solid electrolyte interphase (SEI) formation, changing electrode potentials and state of charge variations in Li-ion battery electrodes. The results show that components in the SEI have a significantly different binding energy reference point relative to the bulk electrode material (i.e. up to 2 eV). It is also shown that electrode components with electronically insulating/semi-conducting nature are shifted as a function of electrode potential relative to highly conducting materials. Further, spectral changes due to lithiation are highly depending on the nature of the active material and its lithiation mechanism. Finally, a strategy for planning and evaluating PES experiments on battery electrodes is proposed where some materials require careful choice of one or more internal reference points while others may be treated essentially without internal calibration.

National Category
Physical Sciences Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-336952 (URN)10.1021/acs.jpcc.7b08923 (DOI)000418393900008 ()
Funder
Swedish Energy Agency, 40495-1EU, FP7, Seventh Framework Programme, Eurolion & HiCSwedish Research Council, 2016-03545VINNOVA, High Voltage ValleyStandUp
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2018-02-16Bibliographically approved
Ottosson, M., Boman, M., Berastegui, P., Andersson, Y., Hedlund, M., Korvela, M. & Berger, R. (2017). Copper in ultrapure water, a scientific issue under debate. Corrosion Science, 122, 53-60
Open this publication in new window or tab >>Copper in ultrapure water, a scientific issue under debate
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2017 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 122, p. 53-60Article in journal (Refereed) Published
Abstract [en]

The corrosion properties of copper in ultrapure water have been studied experimentally by submerging copper samples (99.9999%) in pure water for up to 29 months. The surface was first electropolished at ambient temperature, then exposed to hydrogen gas treatment at 300-400 degrees C, thereby reducing the bulk hydrogen content to 0.03 ppm. These copper samples, the water and the glassware were all then subjected to precise chemical analysis. Great care was taken to avoid contamination. After exposure, only similar to 6 mu g/L copper had accumulated in the water phase. Electron spectroscopy could not detect Cu2O or any other oxidation products containing copper.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2017
Keywords
Copper, XPS, AES, Oxidation
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-330714 (URN)10.1016/j.corsci.2017.03.014 (DOI)000404490600006 ()
Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2017-12-28Bibliographically approved
Björklund, E., Brandell, D., Hahlin, M., Edström, K. & Younesi, R. (2017). How the Negative Electrode Influences Interfacial and Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2 Cathodes in Li-Ion Batteries. Journal of the Electrochemical Society, 164(13), A3054-A3059
Open this publication in new window or tab >>How the Negative Electrode Influences Interfacial and Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2 Cathodes in Li-Ion Batteries
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2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. A3054-A3059Article in journal (Refereed) Published
Abstract [en]

The cycle life of LiNi1/3Co1/3Mn1/3O2 (NMC) based cells are significantly influenced by the choice of the negative electrode. Electrochemical testing and post mortem surface analysis are here used to investigate NMC electrodes cycled vs. either Li-metal, graphite or Li4Ti5O12 (LTO) as negative electrodes. While NMC-LTO and NMC-graphite cells show small capacity fading over 200 cycles, NMC-Li-metal cell suffers from rapid capacity fading accompanied with an increased voltage hysteresis despite the almost unlimited access of lithium. X-ray absorption near edge structure (XANES) results show that no structural degradation occurs on the positive electrode even after >200 cycles, however, X-ray photoelectron spectroscopy (XPS) results shows that the composition of the surface layer formed on the NMC cathode in the NMC-Li-metal cell is largely different from that of the other NMC cathodes (cycled in the NMC-graphite or NMC-LTO cells). Furthermore, it is shown that the surface layer thickness on NMC increases with the number of cycles, caused by continuous electrolyte degradation products formed at the Li-metal negative electrode and then transferred to NMC positive electrode.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-338161 (URN)10.1149/2.0711713jes (DOI)000418409800021 ()
Funder
Swedish Energy Agency, 37725-1; 40495-1StandUp
Available from: 2018-01-08 Created: 2018-01-08 Last updated: 2019-04-11Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5680-1216

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