Nonaqueous hybrid redox flow energy storage with a sodium–TEMPO chemistry and a single-ion solid electrolyte separator

Yu, Xingwen; Manthiram, Arumugam

doi:10.1039/d1ya00010a

Cited by 4 publications

(2 citation statements)

References 34 publications

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“…The TEMPO radical undergoes electrochemical oxidation to generate TEMPO + , an oxoammonium species that can be reduced back to TEMPO. The reversible electron transfer exhibits a positive redox potential and fast electron-transfer kinetics, all advantageous properties for a RFB catholyte. , The first electrochemical characterization of TEMPO dates back to the 1970s by Tamura and co-workers . Since then, TEMPO has been used as a catholyte in a variety of both aqueous and nonaqueous RFB systems. − Recent approaches have expanded to investigate a variety of TEMPO derivatives as well as the incorporation of ionic liquid as the supporting electrolyte.…”

Section: Introductionmentioning

confidence: 99%

“…The reversible electron transfer exhibits a positive redox potential and fast electron-transfer kinetics, all advantageous properties for a RFB catholyte. 14,15 The first electrochemical characterization of TEMPO dates back to the 1970s by Tamura and co-workers. 16 Since then, TEMPO has been used as a catholyte in a variety of both aqueous and nonaqueous RFB systems.…”

Section: ■ Introductionmentioning

confidence: 99%

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Probing Redox Properties of Extreme Concentrations Relevant for Nonaqueous Redox-Flow Batteries

Stumme

Perera

Horvath

et al. 2023

ACS Appl. Energy Mater.

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Redox-flow batteries are an emerging energy storage technology that can pair with intermittent renewable energy technologies. There remains a need, however, to understand physicochemical relationships among the solvent, electrolyte salt, and redox-active molecules that comprise catholyte and anolyte solutions. To examine this relationship, we detail a systematic study wherein the concentrations of the redox-active molecule 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and TBAPF 6 electrolyte salts are varied over concentrations of 1 mM to over 1000 mM in acetonitrile. Three series were investigated:(1) varying the concentration of TEMPO while holding the concentration of TBAPF 6 constant, (2) varying the concentration of TBAPF 6 while holding the concentration of TEMPO constant, and (3) varying both the concentration of TEMPO and TBAPF 6 with a 5:1 TBAPF 6 :TEMPO ratio. Cyclic voltammetry data from macro-and microelectrodes were used to quantify diffusion coefficients and heterogeneous electron transfer rates, and these metrics were connected to the conductivity and viscosity to develop clear trends over the entire concentration range. Fundamental chemical interactions that lead to changes in physical properties were implicated via vibrational spectroscopy and molecular dynamics (MD) simulations. Trends in conductivity and viscosity for systems were inversely related and correlated to trends in diffusion coefficients and heterogeneous electron transfer rates. Intuitively, faster diffusion and electron-transfer rates occurred with lower TEMPO concentrations and higher TBAPF 6 concentrations, with the majority of conditions falling in the general proximity of literature values (k 0 = 0.1−0.5 cm/s, D ≈ (2.0−4.0) × 10 −5 cm 2 /s). At the highest TBAPF 6 concentrations, vibrational spectroscopy and MD simulations show that intermolecular interactions were more nuanced, and solvation and ion-pairing effects begin to influence electrochemical and physical properties. This functional approach including electrochemical and physical characterization paired with MD simulations provides a template for methodically studying systems for redox flow battery applications.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Probing Redox Properties of Extreme Concentrations Relevant for Nonaqueous Redox-Flow Batteries

Stumme

Perera

Horvath

et al. 2023

ACS Appl. Energy Mater.

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Gel Adsorbed Redox Mediators Tempo as Integrated Solid‐State Cathode for Ultra‐Long Life Quasi‐Solid‐State Na–Air Battery

Xu,

Zhang,

Peng

et al. 2023

Advanced Energy Materials

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In metal–air batteries, the integrated solid‐state cathode is considered a promising design because it can solve the problem of high interfacial resistance of conventional solid‐state cathodes. However, solid discharge products cannot be efficiently decomposed in an integrated solid‐state cathode, resulting in batteries that are unable to operate for long periods of time. Herein, an integrated solid‐state cathode (Gel‐Tempo cathode) of sodium–air batteries (SABs) capable of promoting efficient decomposition of discharge product Na2O2 is designed. The Gel‐Tempo cathode is synthesized by cationic–π interaction of redox mediator 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (Tempo) and ionic liquid with carbon nanotubes. The Gel‐Tempo cathode serves multiple functions as a redox mediator, flame retardancy, and high stability to air. In quasi‐solid‐state SABs, the Gel‐Tempo cathode reduces overpotential to 1.15 V and improves coulomb efficiency to 84.5% (at a limited discharge capacity of 3000 mAh g−1) compared to gel cathodes. Experiments and density functional theory calculations indicate that Tempo significantly reduces the Gibbs free energy in the decomposition reaction of Na2O2, and high Tempo content is more conducive to enhancing the decomposition kinetics of Na2O2 and hence resulting in an ultra‐long cycle life (1746 h). This work is crucial to promote practical applications of SABs, providing guidelines for functionalization design of integrated solid‐state cathodes for metal–air batteries.

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Imidazolium-functionalized liquid ferrocene derivative positive material enables robust cycling stability of non-aqueous redox flow battery

Zhen

Zhang

2023

Chemical Engineering Journal

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Nonaqueous hybrid redox flow energy storage with a sodium–TEMPO chemistry and a single-ion solid electrolyte separator

Abstract: Integration of a sodium anode chemistry and a TEMPO cathode chemistry enables the advancement of a high voltage nonaqueous hybrid flow battery (HFB). A single-ion solid-electrolyte separator ensures a crossover-free operation of the HFB.

Cited by 4 publications

References 34 publications

Probing Redox Properties of Extreme Concentrations Relevant for Nonaqueous Redox-Flow Batteries

Probing Redox Properties of Extreme Concentrations Relevant for Nonaqueous Redox-Flow Batteries

Gel Adsorbed Redox Mediators Tempo as Integrated Solid‐State Cathode for Ultra‐Long Life Quasi‐Solid‐State Na–Air Battery

Imidazolium-functionalized liquid ferrocene derivative positive material enables robust cycling stability of non-aqueous redox flow battery

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