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Rechargeability of aqueous sulfate Zn/MnO2 batteries enhanced by accessible Mn2+ ions
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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Number of Authors: 52018 (English)In: Energy storage materials, ISSN 2405-8289, Vol. 15, p. 351-360Article in journal (Refereed) Published
Abstract [en]

The Zn/MnO2 battery is safe, low cost and comes with a high energy density comparable to Li-ion batteries. However, irreversible spinel phases formed at the MnO2 electrode limits its cyclability. A viable solution to overcome this inactive phase is to use an aqueous ZnSO4-based electrolyte, where pH is mildly acidic leading to a different reaction mechanism. Most importantly, the addition of MnSO4 achieves excellent cyclability. How accessible Mn2+ ions in the electrolyte enhances the reversibility is presented. With added Mn2+, the capacity retention is significantly improved over 100 cycles. Zn2+ insertion plays an important role on the reversibility and a hydrated layered Zn-buserite structure formed during charge is reported. Furthermore, Zn4SO4(OH)(6) center dot 5H(2)O precipitates during discharge but is not involved in the electrochemical reaction. This precipitate both buffers the pH and partly insulates the surface. Described in operando study show how the phase transformations and the failure mechanisms depend on the presence of Mn2+-ions in the electrolyte. These results give insight necessary to improve this battery further to make it a worthy contender to the Li-ion battery in large scale energy storage solutions.

Place, publisher, year, edition, pages
2018. Vol. 15, p. 351-360
National Category
Materials Engineering Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-163000DOI: 10.1016/j.ensm.2018.06.019ISI: 000449521500037OAI: oai:DiVA.org:su-163000DiVA, id: diva2:1270148
Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-17Bibliographically approved
In thesis
1. Rechargeable Aqueous Batteries Based on Available Resources: Investigation and Development towards Efficient Battery Performance
Open this publication in new window or tab >>Rechargeable Aqueous Batteries Based on Available Resources: Investigation and Development towards Efficient Battery Performance
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Batteries employing water based electrolytes enable extremely low manufacturing costs and are inherently safer than Li-ion batteries. Batteries based on zinc, manganese dioxide, iron, and air have high energy relevancy, are not resource restricted, and can contribute to large scale energy storage solutions. Zinc has a rich history as electrode material for primary alkaline Zn–MnO2 batteries. Historically, its use in secondary batteries has been limited because of morphological uncertainties and passivation effects that may lead to cell failure. Manganese dioxide electrodes are ineffective as rechargeable electrodes because of failure mechanisms associated with phase transformations during cycling. The irreversibility of manganese dioxide is strongly correlated to the formation of the electrochemically inactive spinel, Mn3O4/ZnMn2O4. The development of the iron electrode for Fe–air batteries was initiated in late the 1960s and these batteries still suffer from charging inefficiency, due to the unwanted hydrogen evolution reaction. Meanwhile, the air electrode is limited in long-term operation because of the sluggish oxygen evolution and reduction kinetics. These limitations of the Fe–air battery yield poor overall efficiencies, which bring vast energy losses upon cycling.

Herein, the limitations described above were countered for rechargeable Zn–MnO2 and Fe–air batteries by synthesizing electrode materials and modifying electrolyte compositions. The electrolyte mixture of 1 M KOH + 3 M LiOH for rechargeable alkaline Zn–MnO2 batteries limited the formation of the inactive spinels and improved their cycle life significantly. Further, the formation of the inactive spinels was overcome in mildly acidic electrolytes containing 2 M ZnSO4, enabling the cells to cycle reversibly at lower pH via a distinctive reaction mechanism. The iron electrodes were improved with the addition of stannate, which suppressed hydrogen evolution. Furthermore, optimal charge protocols of the iron electrodes were identified to minimize the hydrogen evolution rate. On the air electrode, the synthesized NiCo2O4 showed excellent bifunctional catalytic activity for oxygen evolution and reduction, and was incorporated to a flow assisted rechargeable Fe–air battery, in order to prove the practicability of this technology. Studies of the electrode materials on the micro, macro, nano, and atomic scales were carried out to increase the understanding of the nature of and interactions between of these materials. This included both in operando and ex situ characterization. X-ray and neutron radiation, and analytical- and electrochemical methods provided insight to improve the performance and cycle life of the batteries.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2019. p. 66
Keywords
rechargeable aqueous batteries, alkaline electrolytes, aqueous sulfate electrolytes, zinc electrodes, manganese dioxide electrodes, iron electrodes, air electrodes, oxygen electrocatalysts
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-163154 (URN)978-91-7797-552-6 (ISBN)978-91-7797-553-3 (ISBN)
Public defence
2019-02-15, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2019-01-23 Created: 2018-12-17 Last updated: 2019-01-22Bibliographically approved

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