Singulett‐Sauerstoff in der aprotischen Natrium‐O<sub>2</sub>‐Batterie

Schafzahl, Lukas; Mahne, Nika; Schafzahl, Bettina; Wilkening, Martin; Slugovc, Christian; Borisov, Sergey M.; Freunberger, Stefan

doi:10.1002/ange.201709351

Cited by 18 publications

(16 citation statements)

References 38 publications

(29 reference statements)

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“…[16] Thedifferent chemical stability between NaO 2 and KO 2 can be related to their thermodynamic properties. [24,25] Even though both NaO 2 and KO 2 have been identified as discharge products,o nly KO 2 is thermodynamically stable.H ence,t he spontaneous disproportionation route to peroxide is prohibited in K-O 2 cells,which distinguishes them from Na-O 2 cells. [13,14] Theincreased charge overpotential triggers parasitic reactions and dramatically decreased cell efficiency.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…Ar ecent study also indicates that the disproportionation pathway from superoxide to peroxide, as well as the high voltage to electrochemically decompose peroxide (Li 2 O 2 or Na 2 O 2 ), can even generate singlet oxygen and accounts for electrolyte decompositions. [24,25] Even though both NaO 2 and KO 2 have been identified as discharge products,o nly KO 2 is thermodynamically stable.H ence,t he spontaneous disproportionation route to peroxide is prohibited in K-O 2 cells,which distinguishes them from Na-O 2 cells. On the other hand, the reactivity of superoxide also relies on its solubility in the electrolyte.A lthough NaO 2 and KO 2 are almost insoluble in all organic solvents,i ti ss peculated that the precipitation of solid Na 2 O 2 ·2 H 2 Ow ould induce the dissolution of NaO 2 and continuously release O 2 À .…”

Section: Angewandte Chemiementioning

confidence: 99%

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The Long‐Term Stability of KO₂ in K‐O₂ Batteries

et al. 2018

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The rechargeable K-O 2 battery is recognized as ap romising energy storage solution owingt oi ts large energy density,l ow overpotential, and high coulombic efficiency based on the single-electron redoxc hemistry of potassium superoxide.H owever,t he reactivity and long-term stability of potassium superoxide remains ambiguous in K-O 2 batteries. Parasitic reactions are explored and the use of ion chromatography to quantify trace amounts of side products is demonstrated. Both quantitative titrations and differential electrochemical mass spectrometry confirm the highly reversible single-electron transfer process,w ith 98 %c apacity attributed to the formation and decomposition of KO 2 .Incontrast to the Na-O 2 counterparts,r emarkable shelf-life is demonstrated for K-O 2 batteries owing to the thermodynamic and kinetic stability of KO 2 ,which prevents the spontaneous disproportionation to peroxide.T his work sheds light on the reversible electrochemical process of K + + e À + O 2 $KO 2 .

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Section: Angewandte Chemiementioning

confidence: 99%

Section: Angewandte Chemiementioning

confidence: 99%

The Long‐Term Stability of KO₂ in K‐O₂ Batteries

et al. 2018

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“…Thus, besides the generation of triplet oxygen, the generation of singlet oxygen needs to be understood in detail in order to develop strategies to avoid its formation and thus to diminish the degradation of the cathode materials. The formation of singlet oxygen has also been detected as the main driver for degradation in Na/O 2 cells …”

Section: Introductionmentioning

confidence: 99%

Pathways to Triplet or Singlet Oxygen during the Dissociation of Alkali Metal Superoxides: Insights by Multireference Calculations of Molecular Model Systems

Zaichenko

Schröder

Janek

et al. 2020

Chemistry A European J

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Recent experimental investigations demonstrated the generation of singlet oxygen during charging at high potentials in lithium/oxygen batteries. To contribute to the understanding of the underlying chemical reactions a key step in the mechanism of the charging process, namely, the dissociation of the intermediate lithium superoxide to oxygen and lithium, was investigated. Therefore, the corresponding dissociation paths of the molecular model system lithium superoxide (LiO2) were studied by CASSCF/CASPT2 calculations. The obtained results indicate the presence of different dissociation paths over crossing points of different electronic states, which lead either to the energetically preferred generation of triplet oxygen or the energetically higher lying formation of singlet oxygen. The dissociation to the corresponding superoxide anion is energetically less preferred. The understanding of the detailed reaction mechanism allows the design of strategies to avoid the formation of singlet oxygen and thus to potentially minimize the degradation of materials in alkali metal/oxygen batteries. The calculations demonstrate a qualitatively similar but energetically shifted behavior for the homologous alkali metals sodium and potassium and their superoxide species. Fundamental differences were found for the covalently bound hydroperoxyl radical.

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“…Unfortunately, this technology is facing many challenges: During charge and discharge, reactive oxygen species like singlet oxygen and superoxide are formed, which are leading to side reactions with carbon electrodes and the electrolyte. [1][2][3][4][5][6] Moreover, the main discharge products in LiÀ O 2 , NaÀ O 2 , KÀ O 2 and MgÀ O 2 batteries are Li 2 O 2 , NaO 2 , KO 2 and MgO 2 , which are electronically insulating. [7][8][9][10][11][12][13][14][15] For the electrochemical deposition of Li 2 O 2 , Bondue et.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the Mechanism of the Solution‐Mediated Oxygen Reduction in Metal‐O₂ Batteries: The Importance of Ion Association

2019

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One of the bottlenecks in Li−O2 batteries is the film like growth of Li2O2 on the electrode surface during discharge leading to early cell death. To tackle this problem 2,5‐Di‐tert‐1,4‐benzoquinone (DBBQ) was introduced as a soluble redox mediator. This redox mediator is avoiding the Li2O2 layer‐by‐layer growth on the electrode surface and thus leading to higher discharge capacities of the Li−O2 cell. In this study, we investigate the ion pairing between the cation of the conducting salt and the DBBQ monoanion and the resulting impact on the ORR activity of the DBBQ monoanion. We investigate TBA+, K+ and Li+ as cations and TEGDME and DMSO as solvents. We found out that there is a direct correlation between the ORR activity of DBBQ− and the ion pairing of DBBQ− with the cation of the supporting electrolyte: Only if DBBQ is strongly associated with the cations of the electrolyte it will reduce oxygen in the electrolyte. Increasing the Li+ concentration in the electrolyte shifts the ORR potential to more positive electrode potentials. In addition, we are describing a new experimental approach to investigate the kinetics of the homogenous ORR via time resolved mass spectrometry. With this approach we found out, that the reaction Li··· DBBQ(sol)+O2(sol)↔k-1k1 Li··· DBBQ··· O2(sol) is 80 times faster in a TEGDME based electrolyte than in a DMSO‐based electrolyte. We determined k1 with 5.1· 102 s−1 M−1and k-1 with 3.7 102 s−1 M−1 in TEGDME whereas the constants in DMSO are k1 =4.5 s−1 M−1 and k-1 =5.5 s−1 M−1s.

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Singulett‐Sauerstoff in der aprotischen Natrium‐O₂‐Batterie

Abstract: Aprotische Natrium-O 2 -Batterien basieren auf der reversiblen Bildung und Auflçsung von Natriumsuperoxid (NaO 2 )w ährend des Zellbetriebs.N ebenreaktionen des Elektrolyten und der Elektrode mit dem stark nukleophilen und basischen NaO 2 führen zu mangelhafter Zyklenstabilität.

Cited by 18 publications

References 38 publications

The Long‐Term Stability of KO₂ in K‐O₂ Batteries

The Long‐Term Stability of KO₂ in K‐O₂ Batteries

Pathways to Triplet or Singlet Oxygen during the Dissociation of Alkali Metal Superoxides: Insights by Multireference Calculations of Molecular Model Systems

Unraveling the Mechanism of the Solution‐Mediated Oxygen Reduction in Metal‐O₂ Batteries: The Importance of Ion Association

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Singulett‐Sauerstoff in der aprotischen Natrium‐O2‐Batterie

Abstract: Aprotische Natrium-O 2 -Batterien basieren auf der reversiblen Bildung und Auflçsung von Natriumsuperoxid (NaO 2 )w ährend des Zellbetriebs.N ebenreaktionen des Elektrolyten und der Elektrode mit dem stark nukleophilen und basischen NaO 2 führen zu mangelhafter Zyklenstabilität.

Cited by 18 publications

References 38 publications

The Long‐Term Stability of KO2 in K‐O2 Batteries

The Long‐Term Stability of KO2 in K‐O2 Batteries

Pathways to Triplet or Singlet Oxygen during the Dissociation of Alkali Metal Superoxides: Insights by Multireference Calculations of Molecular Model Systems

Unraveling the Mechanism of the Solution‐Mediated Oxygen Reduction in Metal‐O2 Batteries: The Importance of Ion Association

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Singulett‐Sauerstoff in der aprotischen Natrium‐O₂‐Batterie

The Long‐Term Stability of KO₂ in K‐O₂ Batteries

The Long‐Term Stability of KO₂ in K‐O₂ Batteries

Unraveling the Mechanism of the Solution‐Mediated Oxygen Reduction in Metal‐O₂ Batteries: The Importance of Ion Association