A rechargeable redox battery utilizing ruthenium complexes with non-aqueous organic electrolyte

Matsuda, Yoshiharu; Tanaka, Kazuhiro; Okada, Mieko; Takasu, Yoshio; Morita, Masayuki; Matsumura-Inoue, Takeko

doi:10.1007/bf01016050

Cited by 178 publications

(131 citation statements)

References 7 publications

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“…Organic electrolytes often have wider potential windows than that of water and, consequently, there is a lot of interest in high energy density, organic RFB systems and systems based on Ru [4], V [5], Mn [6], and Cr [7] complexes have been reported. In a similar approach to that used in the popular aqueous all-vanadium RFBs [8], the same chemical species is often used on each side of non-aqueous RFBs, mitigating the effects of transfer of redox species between compartments and increasing the coulombic efficiency [3].…”

Section: Introductionmentioning

confidence: 99%

Room temperature ionic liquid electrolytes for redox flow batteries

Ejigu

Greatorex-Davies

Walsh

2015

Electrochemistry Communications

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Section: Introductionmentioning

confidence: 99%

Room temperature ionic liquid electrolytes for redox flow batteries

Ejigu

Greatorex-Davies

Walsh

2015

Electrochemistry Communications

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“…When supported by alkali and alkaline-earth-metal salts, the cations coordinate with acac -ligands harvested from the M(acac) 3 and shift equilibrium reduction potentials; this coordination does not occur in the presence of tetraethylammonium cations, however. 16,23,24 Tetraalkylammonium salts have consequently been preferred as supporting electrolytes for nonaqueous RFB research.Nonaqueous RFB cells based on several metal/organic coordination complexes have been hypothesized to charge and discharge via single-electron disproportionation and comproportionation mechanisms, respectively, 2,3,6,8,9 but the chromium system exhibits unexpected charge/discharge behavior in light of this proposed electrochemistry. The present study aims to illuminate the chemical or electrochemical processes responsible for the unusual cycling responses of Cr(acac) 3 cells.…”

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confidence: 99%

Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Saraidaridis

Bartlett

Monroe

2016

J. Electrochem. Soc.

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Chromium acetylacetonate, or Cr(acac) 3 , is a promising active species for high-energy-density symmetric redox flow batteries because the neutral complex supports multiple charge-transfer reactions with widely separated redox potentials. Voltammetric and spectroelectrochemical measurements were performed to probe the mechanism of the first electrochemical disproportionation of Cr(acac) 3 -i.e., the cell reaction associated with the two redox couples immediately adjacent to the equilibrium potential of a freshly prepared nonaqueous Cr(acac) 3 solution. Substantially different limiting currents are observed for the positive and negative half-reactions, suggesting that at least one deviates from the similar outer-sphere single-electron transfer mechanisms proposed earlier. Spectroelectrochemical chronoamperometry suggests ligand dissociation in the negative reaction, and consequent structural reorganization of the Cr(acac) 3 complex. Vanadium acetylacetonate was investigated for comparison, and no ligand dissociation was observed. A negative half-reaction mechanism consistent with the voltammetric and spectroelectrochemical data is proposed, and used to rationalize observations of charge/discharge behavior in cycling Cr (acac) As researchers have identified the economic benefits that largescale energy storage delivers to the grid, research into redox flow batteries (RFBs) has expanded.1 In efforts to increase energy density or decrease active-species loading, researchers have targeted nonaqueous RFB chemistries, which can produce operating potentials outside the stability window of water.2-8 Several nonaqueous chemistries are based on transition-metal-centered coordination complexes. 2,3,[6][7][8][9] Chromium acetylacetonate, or Cr(acac) 3 , appears especially promising as an RFB active species: it has five accessible redox states, and there is a wide voltage separation between the first reduced and first oxidized states of the neutral complex. The Cr(acac) 3 complex has also been used for catalysis 10 and as a standard for atomic absorption spectra.11 Whereas vanadium acetylacetonate, or V(acac) 3 , appears to support outer-sphere electron transfer for both single-electron addition and withdrawal in certain nonaqueous electrolytes, and to undergo both charge exchanges with relatively facile kinetics, 12 the voltammetric response of Cr(acac) 3 is harder to interpret. Experimental efforts to clarify the electrochemistry of Cr(acac) 3 have been challenging because the reaction mechanism apparently varies with the choices of solvent, supporting electrolyte, and working electrode. 13-17The literature describing nonaqueous Cr(acac) 3 electrochemistry does not provide a consensus about the mechanisms for either the first reduction or first oxidation of the neutral complex. The electrochemical response during reduction depends heavily upon solvent, with different behavior observed in dimethylsulfoxide, 13,15,18,19 N,N-dimethylformamide, 15 dichloromethane, 14 acetonitrile, 15,17,20 and others. 15 Various mechanisms have...

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“…6 Non-aqueous solvents, on the other hand, exhibit wider electrochemical potential windows, offering the possibility for higher power and energy densities. Several non-aqueous electrolytes using metal-ligand complexes as the active-redox species in organic solvents have exhibited cell potentials above 2 V. [7][8][9] The nonaqueous vanadium acetylacetonate (V(acac) 3 ) in acetonitrile (∼2.2 V) has a theoretical energy density of 18 Wh l −1 due to the relatively low solubility of this complex whereas the aqueous all vanadium (1.29 V) exhibits an average energy density of 25 Wh l −1 . 6,10 Current investigations are focused on increasing the solubility of both the redox-active species and supporting electrolyte in organic solvents to achieve higher performance for practical applications.…”

mentioning

confidence: 99%

Performance of a Non-Aqueous Vanadium Acetylacetonate Prototype Redox Flow Battery: Examination of Separators and Capacity Decay

Escalante-García

Wainright

Thompson

et al. 2014

J. Electrochem. Soc.

126

119

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Non-aqueous electrolytes are stable over wide electrochemical potential windows, generally >2 V, and therefore hold promise for enabling higher energy and power density redox flow batteries (RFBs). Nevertheless, the development of non-aqueous RFBs is at an early stage and significant research efforts are needed to demonstrate non-aqueous RFBs with performance characteristics that exceed those of aqueous RFBs. The membrane or separator is a critical component that to a great extent determines the performance of RFB systems for practical applications. In this work, the performance of a RFB was evaluated with Nafion 1035 membranes and Daramic 175 SLI microporous separators. The non-aqueous electrolyte was based on vanadium (III) acetylacetonate. This chemistry possesses two couples over ∼2.2 V. Charge-discharge cycles were performed in a RFB at a current density of 10 mA cm −2 . Coulombic and energy efficiencies of 91% and 80% were achieved using the Nafion membrane. A similar RFB using the Daramic microporous separator achieved columbic and energy efficiencies of 73% and 68%, respectively. The source of capacity decay during multiple charge-discharge cycles was also investigated. The loss in the capacity was related to the poor chemical stability of the vanadium acetylacetonate in the positive electrolyte during battery cycling. Redox flow batteries (RFBs) have emerged as very attractive options for large-scale energy storage applications and, could facilitate the integration of renewable energy resources (e.g. wind and solar) with the current electricity grid.1,2 RFBs are electrochemical devices that store electrical energy in soluble electro-active species in a liquid electrolyte. The electro-active species are stored externally in separate reservoirs and are pumped through the battery stack during operation. The energy is stored or delivered by means of a redox reaction between the two species with different standard electrode potentials, separated by a membrane.2,3 Unlike conventional batteries, RFBs are more attractive for large scale energy storage because they offer more flexible operation, simple electrode reactions, longer cycle life, higher overall energy efficiencies and easier scale-up. 4 Nonetheless, RFB technology is still in an early stage; challenges that remain in the quest to produce devices with high power and energy density at low cost include the discovery or development of stable, high energy density redox electrolytes, and efficient and low cost membranes or separators. 1,5 Aqueous and non-aqueous chemistries are being investigated for use in RFBs. The cell potential of aqueous RFBs is limited to less than ∼1.6 V primarily due to the electrochemical stability of water at carbon/graphite electrodes.6 Non-aqueous solvents, on the other hand, exhibit wider electrochemical potential windows, offering the possibility for higher power and energy densities. Several non-aqueous electrolytes using metal-ligand complexes as the active-redox species in organic solvents have exhibited cell potentials ab...

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A rechargeable redox battery utilizing ruthenium complexes with non-aqueous organic electrolyte

Cited by 178 publications

References 7 publications

Room temperature ionic liquid electrolytes for redox flow batteries

Room temperature ionic liquid electrolytes for redox flow batteries

Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Performance of a Non-Aqueous Vanadium Acetylacetonate Prototype Redox Flow Battery: Examination of Separators and Capacity Decay

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