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Anti-Ageing Strategies: How to avoid failure in sodium-ion batteries
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0002-2293-1901
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to move away from fossil fuels, batteries are one of the most important technologies to store energy from renewable sources. The rapid demands of battery applications put pressure on supply chains of raw materials, such as lithium, nickel, copper, aluminium and cobalt. There is a concern about the availability of such elements in the future. Sodium-ion batteries based on naturally abundant elements have become an attractive alternative to lithium-ion batteries due to their potential to reduce the cost and to improve the sustainability of batteries. A low electrochemical cycling stability of these Na-ion batteries can hinder long-term implementation in large-scale applications. It is necessary to understand what can lead to ageing and electrochemical cycling failure in sodium-ion batteries and how such detrimental side-reactions can be prevented. Compared to lithium-ion batteries, the research on sodium-ion batteries is not as mature yet.

This thesis work sheds light on the ageing mechanisms at the electrode/electrolyte interfaces and in the bulk of electrode materials with the help of a variety of spectroscopic and electrochemical methods. The electrochemical properties at the anode/electrolyte interface have been carefully investigated with different galvanostatic cycling protocols and x-ray photoelectron spectroscopy (XPS). The solid electrolyte interphase (SEI) in sodium-ion batteries is known to be inferior to its Li-analogue and hence, its long-term stability needs to be thoroughly investigated in order to improve it. Fundamental properties of the SEI in regards to formation, growth and dissolution are investigated on platinum and carbon black electrodes in different electrolyte systems. As well as the use of unconventional additives have proven to saturate the electrolyte and to mitigate SEI dissolution. This work shows one of the few studies highlighting SEI dissolution using electrochemical cycling tests coupled with pauses, in order to detect SEI ageing in batteries. Ageing mechanisms in manganese-based cathodes have also been studied due to the abundance of manganese and their electrochemical performance at high voltages with synchrotron-based XPS, x-ray absorption spectroscopy (XAS), resonant inelastic x-ray scattering (RIXS) and muon spin relaxation measurements coupled with electrochemical techniques. Surface-sensitive studies revealed how capacity losses stem from electrolyte degradation which results in a redox gradient between surface and bulk electrode. The work also shows how anionic redox contributions and incomplete phase transitions are reasons of additional capacity losses observed in manganese-based cathodes. Furthermore, it shows how a low Na-mobility is also an indicator for inferior long-term cycling properties leading capacity losses.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2021. , p. 56
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2056
Keywords [en]
sodium-ion batteries, manganese-based cathodes, solid electrolyte interphase, ageing mechanism
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-449511ISBN: 978-91-513-1252-1 (print)OAI: oai:DiVA.org:uu-449511DiVA, id: diva2:1582621
Public defence
2021-09-24, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2021-09-02 Created: 2021-08-02 Last updated: 2021-09-22
List of papers
1. Strategies for Mitigating Dissolution of Solid Electrolyte Interphases in Sodium-Ion Batteries
Open this publication in new window or tab >>Strategies for Mitigating Dissolution of Solid Electrolyte Interphases in Sodium-Ion Batteries
2021 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 60, no 9, p. 4855-4863Article in journal (Refereed) Published
Abstract [en]

The interfacial reactions in sodium-ion batteries (SIBs) are not well understood yet. The formation of a stable solid electrolyte interphase (SEI) in SIBs is still challenging due to the higher solubility of the SEI components compared to lithium analogues. This study therefore aims to shed light on the dissolution of SEI influenced by the electrolyte chemistry. By conducting electrochemical tests with extended open circuit pauses, and using surface spectroscopy, we determine the extent of self-discharge due to SEI dissolution. Instead of using a conventional separator, beta-alumina was used as sodium-conductive membrane to avoid crosstalk between the working and sodium-metal counter electrode. The relative capacity loss after a pause of 50 hours in the tested electrolyte systems ranges up to 30 %. The solubility of typical inorganic SEI species like NaF and Na2CO3 was determined. The electrolytes were then saturated by those SEI species in order to oppose ageing due to the dissolution of the SEI.

Place, publisher, year, edition, pages
John Wiley & Sons, 2021
Keywords
Sodium-ion batteries, solid electrolyte interphase
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-449512 (URN)10.1002/ange.202013803 (DOI)000605709700001 ()33169891 (PubMedID)
Funder
Swedish Research Council Formas, 2016-01257
Available from: 2021-08-01 Created: 2021-08-01 Last updated: 2024-01-15Bibliographically approved
2. Capacity losses due to solid electrolyte interphase formation and sodium diffusion in sodium-ion batteries
Open this publication in new window or tab >>Capacity losses due to solid electrolyte interphase formation and sodium diffusion in sodium-ion batteries
2021 (English)In: Article in journal (Other academic) Submitted
Keywords
Solid electrolyte interphase, sodium-ion batteries
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-449513 (URN)10.21203/rs.3.rs-623903/v1 (DOI)
Available from: 2021-08-01 Created: 2021-08-01 Last updated: 2023-10-25
3. Understanding charge compensation mechanisms in Na0.56Mg0.04Ni0.19Mn0.70O2
Open this publication in new window or tab >>Understanding charge compensation mechanisms in Na0.56Mg0.04Ni0.19Mn0.70O2
Show others...
2019 (English)In: Communications Chemistry, E-ISSN 2399-3669, Vol. 2, article id 125Article in journal (Refereed) Published
Abstract [en]

Sodium-ion batteries have become a potential alternative to Li-ion batteries due to the abundance of sodium resources. Sodium-ion cathode materials have been widely studied with particular focus on layered oxide lithium analogues. Generally, the capacity is limited by the redox processes of transition metals. Recently, however, the redox participation of oxygen gained a lot of research interest. Here the Mg-doped cathode material P2-Na0.56Mg0.04Ni0.19Mn0.70O2 is studied, which is shown to exhibit a good capacity (ca. 120 mAh/g) and high average operating voltage (ca. 3.5 V vs. Na+/Na). Due to the Mg-doping, the material exhibits a reversible phase transition above 4.3 V, which is attractive in terms of lifetime stability. In this study, we combine X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy techniques to shed light on both, cationic and anionic contributions towards charge compensation.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390622 (URN)10.1038/s42004-019-0227-z (DOI)000494732500002 ()
Funder
EU, Horizon 2020, 730872Swedish Research Council Formas, 2016-01257StandUp
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2021-08-02Bibliographically approved
4. Understanding the redox process upon electrochemical cycling of the P2-Na0.78Co1/2Mn1/3Ni1/6O2 electrode material for sodium-ion batteries
Open this publication in new window or tab >>Understanding the redox process upon electrochemical cycling of the P2-Na0.78Co1/2Mn1/3Ni1/6O2 electrode material for sodium-ion batteries
Show others...
2020 (English)In: Communications Chemistry, E-ISSN 2399-3669, Vol. 3, article id 9Article in journal (Refereed) Published
Abstract [en]

The inclusion of nickel and manganese in layered sodium metal oxide cathodes for sodium ion batteries is known to improve stability, but the redox behaviour at high voltage is poorly understood. Here in situ X-ray spectroscopy studies show that the redox behaviour of oxygen anions can account for an increase in specific capacity at high voltages. Rechargeable sodium-ion batteries have recently attracted renewed interest as an alternative to Li-ion batteries for electric energy storage applications, because of the low cost and wide availability of sodium resources. Thus, the electrochemical energy storage community has been devoting increased attention to designing new cathode materials for sodium-ion batteries. Here we investigate P2- Na0.78Co1/2Mn1/3Ni1/6O2 as a cathode material for sodium ion batteries. The main focus is to understand the mechanism of the electrochemical performance of this material, especially differences observed in redox reactions at high potentials. Between 4.2 V and 4.5 V, the material delivers a reversible capacity which is studied in detail using advanced analytical techniques. In situ X-ray diffraction reveals the reversibility of the P2-type structure of the material. Combined soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering demonstrates that Na deintercalation at high voltages is charge compensated by formation of localized electron holes on oxygen atoms.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2020
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-406713 (URN)10.1038/s42004-020-0257-6 (DOI)000511399600001 ()
Funder
Swedish Research Council, 2017-05466StandUp
Available from: 2020-03-13 Created: 2020-03-13 Last updated: 2021-08-02Bibliographically approved
5. Oxygen Redox Activity through a Reductive Coupling Mechanism in the P3-Type Nickel-Doped Sodium Manganese Oxide
Open this publication in new window or tab >>Oxygen Redox Activity through a Reductive Coupling Mechanism in the P3-Type Nickel-Doped Sodium Manganese Oxide
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2020 (English)In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 3, no 1, p. 184-191Article in journal (Refereed) Published
Abstract [en]

Increasing dependence on rechargeable batteries for energy storage calls for the improvement of energy density of batteries. Toward this goal, introduction of positive electrode materials with high voltage and/or high capacity is in high demand. The use of oxygen chemistry in lithium and sodium layered oxides has been of interest to achieve high capacity. Nevertheless, a complete understanding of oxygen-based redox processes remains elusive especially in sodium ion batteries. Herein, a novel P3-type Na0.67Ni0.2Mn0.8O2, synthesized at low temperature, exhibits oxygen redox activity in high potentials. Characterization using a range of spectroscopic techniques reveals the anionic redox activity is stabilized by the reduction of Ni, because of the strong Ni 3d-O 2p hybridization states created during charge. This observation suggests that different route of oxygen redox processes occur in P3 structure materials, which can lead to the exploration of oxygen redox chemistry for further development in rechargeable batteries.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
sodium ion batteries, layered oxides, anion redox, P3 structure, reductive coupling mechanism, resonant inelastic X-ray scattering
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407185 (URN)10.1021/acsaem.9b02171 (DOI)000510104700024 ()
Available from: 2020-03-20 Created: 2020-03-20 Last updated: 2021-08-02Bibliographically approved
6. Vacancy-Enhanced Oxygen Redox Reversibility in P3-Type Magnesium-Doped Sodium Manganese Oxide Na0.67Mg0.2Mn0.8O2
Open this publication in new window or tab >>Vacancy-Enhanced Oxygen Redox Reversibility in P3-Type Magnesium-Doped Sodium Manganese Oxide Na0.67Mg0.2Mn0.8O2
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2020 (English)In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 3, no 11, p. 10423-10434Article in journal (Refereed) Published
Abstract [en]

Lithium-rich layered oxides and sodium layered oxides represent attractive positive electrode materials exhibiting excess capacity delivered by additional oxygen redox activity. However, structural degradation in the bulk and detrimental reactions with the electrolyte on the surface often occur, leading to limited reversibility of oxygen redox processes. Here, we present the properties of P3-type Na0.67Mg0.2Mn0.8O2 synthesized under both air and oxygen. Both materials exhibit stable cycling performance in the voltage range of 1.8-3.8 V, where the Mn3+/Mn4+ redox couple entirely dominates the electrochemical reaction. Oxygen redox activity is triggered for both compounds in the wider voltage window 1.8-4.3 V with typical large voltage hysteresis from nonbonding O 2p states generated by substituted Mg. Interestingly, for the compound prepared under oxygen, an additional novel reversible oxygen redox activity is shown with an exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition-metal layers is shown to play a critical role not only in forming unpaired O 2p states independent of substituted elements but also in stabilizing the P3 structure during charge with reduced structural transformation to the O'3 phase at the end of discharge. This study reveals the important role of vacancies in P3-type sodium layered oxides to increase energy density using both cationic and anionic redox processes.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
sodium-ion batteries, positive electrode materials, P3 structure, transition-metal vacancies, oxygen redox
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-435139 (URN)10.1021/acsaem.0c01352 (DOI)000595488500017 ()
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2021-08-02Bibliographically approved
7. Na-ion mobility in P2-Na0.5MgxNi0.17-xMn0.83O2 (0 <= x <= 0.07)  from electrochemical and muon spin relaxation studies
Open this publication in new window or tab >>Na-ion mobility in P2-Na0.5MgxNi0.17-xMn0.83O2 (0 <= x <= 0.07)  from electrochemical and muon spin relaxation studies
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2021 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 23, no 42, p. 24478-24486Article in journal (Refereed) Published
Abstract [en]

Sodium transition metal oxides with a layered structure are one of the most widely studied cathode materials for Na+-ion batteries. Since the mobility of Na+ in such cathode materials is a key factor that governs the performance of material, electrochemical and muon spin rotation and relaxation techniques are here used to reveal the Na+-ion mobility in a P2-type Na0.5MgxNi0.17-xMn0.83O2 (x = 0, 0.02, 0.05 and 0.07) cathode material. Combining electrochemical techniques such as galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique with mu+SR, we have successfully extracted both self-diffusion and chemical-diffusion under a potential gradient, which are essential to understand the electrode material from an atomic-scale viewpoint. The results indicate that a small amount of Mg substitution has strong effects on the cycling performance and the Na+ mobility. Amongst the tested cathode systems, it was found that the composition with a Mg content of x = 0.02 resulted in the best cycling stability and highest Na+ mobility based on electrochemical and mu+SR results. The current study clearly shows that for developing a new generation of sustainable energy-storage devices, it is crucial to study and understand both the structure as well as dynamics of ions in the material on an atomic level.

Place, publisher, year, edition, pages
Royal Society of ChemistryRoyal Society of Chemistry, 2021
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-449514 (URN)10.1039/d1cp03115e (DOI)000711105100001 ()34698733 (PubMedID)
Funder
Swedish Research Council Formas, 2016-01257StandUpSwedish Research Council, 2017-05078Swedish Foundation for Strategic Research
Note

Title in dissertation list of papers: Na-mobility in P2-type Na0.5MgxNi0.17−xMn0.83O2 (0 ≤ x ≤ 0.07) from electrochemical and muon-spin relaxation studies

Available from: 2021-08-01 Created: 2021-08-01 Last updated: 2024-01-15Bibliographically approved

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