K–O<sub>2</sub> electrochemistry: achieving highly reversible peroxide formation

Reinsberg, Philip Heinrich; Koellisch, Andreas; Bawol, Pawel Peter; Baltruschat, Helmut

doi:10.1039/c8cp06362a

Cited by 17 publications

(25 citation statements)

References 27 publications

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“…To achieve high energy density KOB, future studies should therefore aim to increase both cathode porosity and mass transport. Promising approaches to further increase mass transport, which we are currently investigating, are tuning of oxygen solubility [43] and superoxide solvation [44] of the electrolyte, as well as changing the oxygen pressure [40,43] . In summary, our results demonstrate that PTFE treatment improves mass transport and enhances the discharge performance of carbon cathodes in KOB.…”

Section: Discussionmentioning

confidence: 65%

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

Küpper

Jakobi

Simon

2021

Batteries & Supercaps

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Potassium‐oxygen batteries (KOB) are a promising energy storage technology with high theoretical energy of 935 Wh/kg and long cycle life. Potential applications require the development of affordable cathode materials with high practical capacity. In this article, we show that low‐cost polytetrafluoroethylene (PTFE) treatment increases the discharge performance of a commercial carbon paper cathode. Cross‐sectional scanning electron microscopy reveals that PTFE alleviates mass transport limitations and facilitates homogeneous deposition of the discharge product potassium superoxide (KO2) within the cathode pore structure. Using electrochemical impedance spectroscopy, we found that PTFE, in combination with the appropriate electrolyte volume, can prevent pore flooding by the electrolyte. Free volume permits fast, gaseous oxygen transport throughout the cathode, which lowers mass transfer resistances and improves the rate capability. Moreover, PTFE enables high pore volume filling by KO2 and, in turn, high discharge capacity. Our results demonstrate that controlling the mass transport is essential for high‐performance cathodes for KOB.

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Section: Discussionmentioning

confidence: 65%

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

Küpper

Jakobi

Simon

2021

Batteries & Supercaps

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“…Though metal‐air battery research is a common research topic nowadays, the performance of this type of battery still remains insufficient and a lot of work still needs to be done. Li‐O 2 , [1–8] Na‐O 2 , [9–12] and Mg‐O 2 [13–15] systems already were topic of research and looking towards further cations like potassium [16–18] and calcium seems reasonable, as the ORR product distribution depends on the cation [4,19–22] . The use of more abundant active materials than lithium for the anode may also be necessary for a wider application.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Reduction of O₂ in Ca²⁺‐Containing DMSO: Role of Roughness and Single Crystal Structure

et al. 2021

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In this study, the oxygen reduction reaction (ORR) in Ca2+‐containing dimethyl sulfoxide (DMSO) at well‐ordered and rough electrode surfaces is compared by using cyclic voltammetry, differential electrochemical mass spectrometry, rotating ring disk electrode, and atomic force microscopy measurements. Slightly soluble CaO2 is the main product during early ORR on gold electrodes; after completion of a monolayer of CaO and/or CaO2, which is formed in parallel and in competition to the peroxide, only superoxide is formed. When the monolayer is completely closed on smooth annealed Au, no further reduction occurs, whereas on rough Au a defect‐rich layer allows for continuous formation of superoxide. CaO2 formed either via two subsequent 1 normale- transfer steps or by disproportionation of superoxide may be deposited on top of the CaO/CaO2 adsorbate layer. The slow dissolution of the peroxide particles is demonstrated by AFM. Whereas a smooth CaO/CaO2‐covered electrode shows severe deactivation and a CaO/CaO2‐covered rough electrode allows for diffusion‐limited superoxide formation, on single crystals peroxide formation is more pronounced. The reason is most likely the lack of nucleation sites for the blocking CaO/CaO2 layer. RRDE investigations showed sluggish reoxidation kinetics of the dissolved peroxide, which are most likely due to ion pairing with Ca2+. The apparent transfer coefficient is estimated by using variation of the electrode roughness, confirming the result of the usual Tafel analysis and indicating an equilibrated first 1 normale- transfer.

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“…The homogenous formation of Li 2 O 2 was also investigated using the RRDE by analyzing the rotational dependency of the collection efficiency . In more recent work in the field of metal‐air batteries with a RRDE even the evolution of superoxide during charge was reported . In these experiments, we used KClO 4 and LiClO 4 supporting salts in a TEGDME based electrolyte.…”

Section: Resultsmentioning

confidence: 99%

“…[33,34,44] In more recent work in the field of metal-air batteries with a RRDE even the evolution of superoxide during charge was reported. [31,45,46] In these experiments, we used KClO 4 and LiClO 4 supporting salts in a TEGDME based electrolyte. The experimental data in oxygen containing electrolyte is shown in Figure 6.…”

Section: Electrochemical Studies In Tegdme-based Electrolytesmentioning

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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K–O₂ electrochemistry: achieving highly reversible peroxide formation

Abstract: Differential electrochemical mass spectrometry and classical electrochemical methods reveal that electrochemically produced K2O2 can be reversibly reoxidized to O2.

Cited by 17 publications

References 27 publications

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

Electrochemical Reduction of O₂ in Ca²⁺‐Containing DMSO: Role of Roughness and Single Crystal Structure

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

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K–O2 electrochemistry: achieving highly reversible peroxide formation

Abstract: Differential electrochemical mass spectrometry and classical electrochemical methods reveal that electrochemically produced K2O2 can be reversibly reoxidized to O2.

Cited by 17 publications

References 27 publications

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

PTFE Enhances Discharge Performance of Carbon Cathodes in Potassium‐Oxygen Batteries**

Electrochemical Reduction of O2 in Ca2+‐Containing DMSO: Role of Roughness and Single Crystal Structure

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

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Product

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K–O₂ electrochemistry: achieving highly reversible peroxide formation

Electrochemical Reduction of O₂ in Ca²⁺‐Containing DMSO: Role of Roughness and Single Crystal Structure

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