WO2023227227A1 - Redox flow battery - Google Patents

Redox flow battery Download PDF

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Publication number
WO2023227227A1
WO2023227227A1 PCT/EP2022/064424 EP2022064424W WO2023227227A1 WO 2023227227 A1 WO2023227227 A1 WO 2023227227A1 EP 2022064424 W EP2022064424 W EP 2022064424W WO 2023227227 A1 WO2023227227 A1 WO 2023227227A1
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WO
WIPO (PCT)
Prior art keywords
flow battery
ion
battery according
redox flow
redox
Prior art date
Application number
PCT/EP2022/064424
Other languages
French (fr)
Inventor
Ilaria PUCHER
Eneko AZACETA
Elisa MUSELLA
Original Assignee
Green Energy Storage S.R.L.
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Filing date
Publication date
Application filed by Green Energy Storage S.R.L. filed Critical Green Energy Storage S.R.L.
Priority to PCT/EP2022/064424 priority Critical patent/WO2023227227A1/en
Publication of WO2023227227A1 publication Critical patent/WO2023227227A1/en

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/86Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96Carbon-based electrodes
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/18Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184Regeneration by electrochemical means
    • H01M8/186Regeneration by electrochemical means by electrolytic decomposition of the electrolytic solution or the formed water product
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/18Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184Regeneration by electrochemical means
    • H01M8/188Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00Electrolytes
    • H01M2300/0002Aqueous electrolytes
    • H01M2300/0005Acid electrolytes
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00Electrolytes
    • H01M2300/0002Aqueous electrolytes
    • H01M2300/0005Acid electrolytes
    • H01M2300/0011Sulfuric acid-based
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30Hydrogen technology
    • Y02E60/50Fuel cells

Definitions

  • the invention relates to a redox flow battery, to an energy storage system including said redox flow battery, as well as to methods for delivering and/or storing electricity by means of said redox flow battery.
  • electrochemical storage and conversion plays a key role.
  • researchers are focusing their attention on finding new materials in order to boost performance: environmental sustainability is essential considering the urgent need for large-scale production and diffusion.
  • Redox flow batteries offer a unique advantage of energy and power independence.
  • RFBs consist of tanks of electrolyte that store chemical energy and electrochemical cells that reversibly convert chemical energy into electrical energy.
  • Aqueous ones offer advantages in terms of safety, toxicity, and cost over their non-aqueous counterparts.
  • Manganese-based RFBs suffer as main drawback for the formation of solid MnC in the electrolyte, which takes places naturally by Mn 3+ disproportionation or electrochemically. Solid Mn02 tends to precipitate, subtracting the active species to the redox reaction and causing detrimental consequences for the functioning of the RFB (clogging, deposits on the electrode surface), that lead to a loss of efficiency of the RFB with time.
  • a first object of the present invention is therefore to provide a manganese-based redox flow battery capable of overcoming the technological limits of the prior art.
  • the Applicant has in fact surprisingly found out that Sn ion is a novel additive for manganese-based redox flow batteries which has a beneficial role for manganese redox mechanisms.
  • the Applicant has indeed surprisingly found out that a specific manganese-based electrolyte including a tin ion as suppression agent allows one-electron (1 ) redox mechanism avoiding Mn 3+ disproportionation into solid manganese oxide compounds which tends to irreversibly precipitate with a detrimental effect on coulombic efficiency and cycle life of the battery.
  • the present invention relates to a redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes, to charge and discharge the battery, wherein:
  • said positive electrode electrolyte comprises at least one manganese ion and at least one tin ion;
  • said negative electrode electrolyte comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
  • the operating principle of the redox flow battery according to the present invention is based on the manganese redox mechanism.
  • the Applicant surprisingly found out that tin suppresses Mn 3+ disproportionation into solid manganese oxide compounds, which tend to irreversibly precipitate.
  • the battery can advantageously operate such that the positive electrode electrolyte has an SOC limit of to 90% when calculated on the assumption of one-electron reaction, without detrimental effects on coulombic efficiency and cycle life of the battery.
  • the present invention relates also to an energy storage or delivery system comprising at least one redox-flow battery according to the first aspect of the present invention and at least one connection means apt to connect said at least one redox-flow battery to an external power source or to a load.
  • Figure 1 schematically shows the redox flow battery used in the experiments according to Examples 1 -3;
  • Figure 2 shows the first charge/discharge cycle obtained with the experiment according to Example 1 ;
  • FIG. 3 shows the electrochemical behavior obtained with the experiment according to Examples 2 and 3.
  • the present invention relates to a redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes, to charge and discharge the battery, wherein:
  • said positive electrode electrolyte comprises at least one manganese ion and at least one tin ion;
  • said negative electrode electrolyte comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
  • the operating principle of the redox flow battery according to the present invention is based on the manganese one-electron (1 ) redox mechanism.
  • the battery can advantageously operate such that the positive electrode electrolyte has an SOC of up to 90% when calculated on the assumption of one-electron, without detrimental effects on capacity and coulombic efficiency and cycle life of the battery.
  • the present invention may present in one or more of the above aspects one or more of the characteristics disclosed hereinafter.
  • a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell.
  • said positive electrode electrolyte and said negative electrode electrolyte are aqueous electrolytes.
  • the positive electrode electrolyte comprises at least one manganese ion.
  • said positive electrode electrolyte comprises said at least one manganese ion in a concentration of from 0.1 M to 4.2 M, more preferably in a concentration of from 1 M to 3.5 M, even more preferably in a concentration of from 1 .5 M to 3 M.
  • the redox reaction of said at least one manganese ion is:
  • a tin ion in said positive electrode electrolyte disproportionation of Mn 3+ into solid manganese oxide compounds is suppressed, thus avoiding its irreversible precipitation in the electrolyte and the resulting loss of capacity and penalty in efficiency of the battery.
  • the positive electrode electrolyte comprises also a tin ion.
  • said positive electrode electrolyte comprises said tin ion in a concentration of from 0.1 M to 8 M, more preferably in a concentration of from 0.25 M to 6 M, even more preferably in a concentration of from 0.5 M to 5 M.
  • the molar ratio between said at least one manganese ion and said tin ion ranges from 0.1 to 2, more preferably from 0.25 to 1 .5.
  • said at least one tin ion is selected from the group consisting of: divalent tin ion (Sn 2+ ) and tetravalent tin ion (Sn 4+ ).
  • Said tetravalent tin ion can be advantageously added to the electrolyte as such, or prepared in situ, by adding to the electrolyte a divalent tin ion and oxidizing it to tetravalent tin (referred to also as “tin(IV)”) using a chemical oxidation method, an electrochemical oxidation method or any alternative process known to the skilled person.
  • tin(IV) tetravalent tin
  • Said electrolyte may further advantageously contain at least one solvation agent, for example acetonitrile.
  • the present invention refers to a redox flow battery wherein the positive electrode electrolyte comprises at least one manganese ion and at least one tetravalent tin ion.
  • the present invention refers therefore also to a redox flow battery wherein the positive electrode electrolyte comprises at least one manganese ion and at least one tin ion selected from divalent tin ion and tetravalent tin ion, and at least one solvation agent, preferably acetonitrile.
  • the positive electrode electrolyte has a pH of from 0 to 2.
  • said positive electrode electrolyte comprises at least one acid in a concentration equal to or lower than 4 M, more preferably in a concentration equal to or lower than 3.5 M, even more preferably in a concentration equal to or lower than 3 M.
  • said at least one acid is selected from the group consisting of: sulfuric acid, hydrochloric acid, phosphoric acid, diphosphoric acid, and nitric acid. More preferably, said at least acid is sulfuric acid (H2SO4).
  • the positive electrode electrolyte of the RFB according to the present invention advantageously comprises also at least one anion, in such quantity as to maintain the charge balance of the electrolyte.
  • Said anion is preferably selected from the group consisting of SO4 2 -, Ch, Br, PO4 2 -, P2O7 4 - and NO3-.
  • the positive electrode electrolyte of the RFB according to the present invention may also comprise further components, such as suspension stabilizers, cosolvents, organic solvents, surfactants, wetting, solvation and dispersing agents.
  • the negative electrode electrolyte of the redox flow battery according to the invention comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
  • the redox potential difference between negative electrode electrolyte and positive electrode electrolyte should advantageously be as high as possible.
  • said at least one active redox species of the negative electrode electrolyte is selected from the group consisting of: a proton, a nickel ion, a cobalt ion, an iron ion, a lead ion, a copper ion, a sulfur ion, a sulfide ion, a zinc ion, a titanium ion, a vanadium ion, a tin ion, a cerium ion, a chromium ion, an iron ion, quinones derivatives thereof, anthraquinones or derivatives thereof, viologens or derivatives thereof, indigo or derivatives thereof, naphtalenediimide or derivatives thereof, diazaanthracenedione or derivatives thereof.
  • said at least one active redox species of the negative electrode electrolyte has an E° of at least 0.6V lower than the E° of the reaction (1 ).
  • said at least one active redox species of the negative electrode electrolyte is a proton and in said negative electrode electrolyte the redox reaction of said proton is
  • redox flow battery basic construction components of a redox flow battery are battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes. Said components have features and may be assembled according to well-known common praxis in the relevant art for carrying out its charging/discharging operations.
  • the positive electrode and the negative electrode of the redox flow battery may be made of the same material or may be made of respectively different materials.
  • Materials suitable for the positive and/or negative electrode of the redox flow battery according to the invention are preferably selected from the group consisting of: a) a composite material comprising at least metal selected from the group consisting of: Ru, Ti, Ir, Mn, Pd, Au, Ti, Sn, Ce, Pt, an alloy thereof, and/or an oxide thereof; b) a carbon composite including the composite material according to letter a); c) a dimensionally stable electrode (DSE) including the composite material according to letter a); d) a conductive polymer; e) graphite and its derivatives, comprising nanosized materials; f) glassy carbon, g) conductive diamond or conductive diamond-like carbon (DLC); h) a nonwoven fabric made of carbon fiber; i) a woven fabric made of carbon fiber; l) a nonwoven fabric made of graphite fiber; and
  • the positive electrode of the redox flow battery is a carbon-based electrode, preferably selected from the group consisting of: a graphite-felt, activated graphite-felt , a carbon felt, a graphite cloth, a graphite nanoparticle, a graphite nanofiber, a carbon cloth, a carbon nanotube, a carbon nanoparticle, or a carbon nanofiber activated electrode.
  • the positive electrode of the redox flow battery according to the invention is a graphite-felt activated electrode.
  • the present invention relates also to an energy storage or delivery system comprising at least one redox-flow battery according to the first aspect of the present invention and at least one connection means apt to connect said at least one redox-flow battery to an external power source or to a load.
  • the present invention relates also to a method of storing electricity by means of the redox-flow battery according to the present invention, and to a method of delivering electricity by means of the redox-flow battery according to the present invention.
  • the present invention relates also to a method of storing electricity comprising the steps of: a) providing a redox-flow battery according to the present invention; b) electrically connecting said redox-flow battery to a power source; and to a method of delivering electricity comprising the steps of: a) providing a redox-flow battery according to according to the present invention; b) electrically connecting said redox-flow battery to a load.
  • H2 was generated in the electrochemical cell. Gas bubbling revealed H2 generation during charge. During discharge, H2 was flowed into the cell at 1 .5 bar of pressure.
  • Example 1 MnSC 0.5 M; SnCk 0.125 M and H2SO4 3 M; 20 mL deionized water.
  • the battery charge process was limited to 241 mAh (corresponding to 90%SOC calculated assuming one electron redox mechanism, with a theoretical 100%SOC of 268mAh).
  • Charge/discharge process were performed at 0.43 mA/cm 2 current density.
  • Example 2 MnSO4-0.5 M, H2SO4 3 M, 20 mL 20%v/v acetonitrile/deionized water. Charge/discharge process were performed at 0.43 mA/cm 2 current density.
  • Example 3 MnSO4-0.5 M, H2SO4, 3 M; 20 mL 20%v/v acetonitrile/deionized water and charged to 220 mAh at 22mA/cm 2 . Then, SnSCkO.125 M (Fisher Scientific, 95%) was added and, from the reaction between Mn 3+ and Sn 2+ , Mn 2+ and Sn 4+ was generated. Is this example, the battery charge process was limited to 241 mAh (corresponding to 90%SOC calculated assuming one electron redox mechanism, with a theoretical 100%SOC of 268mAh). Charge/discharge process were performed at 0.43 mA/cm 2 current density.
  • the catholyte was pumped into the cell at 100 mL/min flow rate at room temperature. Hydrogen gas flow was supplied only during discharge at a pressure of 1 .5 bar.
  • the electrochemical cell was composed of two end plates that sandwiched the rest of the components: two polypropylene isolating plates, two copper current collectors, bipolar plate with flow fields (double serpentine type for cathode and interdigit for the anode side).
  • a 2.5 mm thick activated commercial graphite-felt (SGL-GFD 2.5 EA activated) cathode with an active area of 5x5 cm 2 was used.
  • a 5x5 cm 2 active area gas diffusion layer electrode with 0.5 mg/cm 2 Pt catalyst was used as anode (Quintech - BC-H100-05S).
  • Charge-discharge processes were carried out at 4C, with respect to the nominal capacity of the catholyte, or specified in each case.
  • the lower and upper potential limits were 0.6V and 1 .7 V, respectively.
  • Figure 2 shows the cycles obtained. Reversible charge/discharge processes delivering a discharge capacity of 220 mAh, without visual detection of deposits on tubes and electrolyte tank, serves to demonstrate that Sn 4+ is acting as a precipitation suppression agent. The interaction of Cl’ and related side reaction such CI2 evolution, might interfere and lead to a lower coulombic efficiency.
  • Example 2 depicted in figure 3 as Sn - Free (Ex. 2), an electrolyte with 0.5M Mn 2+ and 20% of acetonitrile which was intended to act as solvation agent was used. In this case, the system reached the cutoff limit at 195 mAh, with a large quantity of precipitates on cell tubing, electrolyte tank and within the cell that made the battery unfeasible. This example showed that acetonitrile by itself does not show the role of precipitation suppression agent for the Mn system.
  • Example 3 depicted in figure 3 as Sn(IV) - Cycle 1 and Cycle 2 (Ex. 3), an aqueous electrolyte containing 0.5M Mn 2+ , 0.125M Sn 4+ obtained by in situ a chemical oxidation of divalent tin ion and 20% of acetonitrile, was used.
  • the charge process was limited to 90% state of charge calculated for one-electron mechanism (241 mAh) and the lack of solids and precipitates in the cell tubing/tank demonstrates that Sn 4+ acts as precipitation suppressing agent.
  • the discharge capacity of 231 mAh demonstrated also the reversibility of the system which cannot be reached in absence of tin.

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
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Abstract

The invention relates to a redox flow battery, to an energy storage system including said redox flow battery, as well as to methods for delivering and/or storing electricity by means of said redox flow battery.

Description

“REDOX FLOW BATTERY”
DESCRIPTION
FIELD OF THE INVENTION
The invention relates to a redox flow battery, to an energy storage system including said redox flow battery, as well as to methods for delivering and/or storing electricity by means of said redox flow battery.
BACKGROUND
Global energy demand doubles every 15 years, and it is forecasted to keep on increasing in the next future with a parallel growing and urgent demand of high-energy resources. However, more than 60% of global electrical energy is produced from coal and from natural gas with an associated huge emission of CO2, which is considered the main contributor to greenhouse effect and global warming.
Because of such detrimental environmental effects, replacing fossil fuels with renewable energy sources - primarily with wind and solar energy - has become imperative. The most relevant problem is that they are intermittent and cannot guarantee a continuous flow of energy. Since our reliance on renewable energy needs to grow, there is an increasing need to store it for times when energy cannot be harvested.
Among possible alternatives, electrochemical storage and conversion plays a key role. Researchers are focusing their attention on finding new materials in order to boost performance: environmental sustainability is essential considering the urgent need for large-scale production and diffusion.
Redox flow batteries (RFBs) offer a unique advantage of energy and power independence. RFBs consist of tanks of electrolyte that store chemical energy and electrochemical cells that reversibly convert chemical energy into electrical energy.
Various types of RFBs have been developed up to now, and they can be classified into two types according to the electrolyte: aqueous and non-aqueous RFBs. Aqueous ones offer advantages in terms of safety, toxicity, and cost over their non-aqueous counterparts.
Although the energy storage systems that use aqueous RFBs are the subject of considerable and ever-increasing interest given their potential, to date the Applicant has found that significant technological and functional limits remain in this sector. Among various redox active species for RFBs, manganese-based RFBs have attracted attention in view of the highly interesting characteristics of manganese as redox active species, through the following one-electron mechanism (Eq. 1 )
Mn2+ <- Mn3+ + e~ (1 ) which has a high redox potential of 1 .51 V (vs SHE) and a high solubility in aqueous media, allowing to obtain a high energy density.
Manganese-based RFBs, however, suffer as main drawback for the formation of solid MnC in the electrolyte, which takes places naturally by Mn3+ disproportionation or electrochemically. Solid Mn02 tends to precipitate, subtracting the active species to the redox reaction and causing detrimental consequences for the functioning of the RFB (clogging, deposits on the electrode surface), that lead to a loss of efficiency of the RFB with time.
To date, several strategies to suppress Mn02 formation in a battery are known, among which the use of additives to suppress Mn02 formation by Mn3+ disproportionation and limiting the charge process to 90% SOC are the most widespread.
The Applicant observed that such strategies present several technological and functional limits and surprisingly found out that a novel additive can be exploited in a manganese- based electrolyte for the functioning of a RFB.
SUMMARY OF INVENTION
A first object of the present invention is therefore to provide a manganese-based redox flow battery capable of overcoming the technological limits of the prior art.
In accordance with the present invention, the Applicant has in fact surprisingly found out that Sn ion is a novel additive for manganese-based redox flow batteries which has a beneficial role for manganese redox mechanisms.
The Applicant has indeed surprisingly found out that a specific manganese-based electrolyte including a tin ion as suppression agent allows one-electron (1 ) redox mechanism avoiding Mn3+ disproportionation into solid manganese oxide compounds which tends to irreversibly precipitate with a detrimental effect on coulombic efficiency and cycle life of the battery.
The electrochemical exploitation of such reversible one-electron redox mechanism (1 ), avoiding the detrimental effect of Mn3+ disproportionation, is of high interest as it provides an efficient and cost-effective battery system. Therefore, in a first aspect the present invention relates to a redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes, to charge and discharge the battery, wherein:
- said positive electrode electrolyte comprises at least one manganese ion and at least one tin ion;
- said negative electrode electrolyte comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
The operating principle of the redox flow battery according to the present invention is based on the manganese redox mechanism. The Applicant surprisingly found out that tin suppresses Mn3+ disproportionation into solid manganese oxide compounds, which tend to irreversibly precipitate. In this way the battery can advantageously operate such that the positive electrode electrolyte has an SOC limit of to 90% when calculated on the assumption of one-electron reaction, without detrimental effects on coulombic efficiency and cycle life of the battery.
In a further aspect, the present invention relates also to an energy storage or delivery system comprising at least one redox-flow battery according to the first aspect of the present invention and at least one connection means apt to connect said at least one redox-flow battery to an external power source or to a load.
The advantages of the energy storage or delivery system according to this further aspect have been already outlined with reference to the above redox flow battery according to the first aspect of the invention and are not repeated herewith.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure 1 schematically shows the redox flow battery used in the experiments according to Examples 1 -3;
Figure 2 shows the first charge/discharge cycle obtained with the experiment according to Example 1 ; and
Figure 3 shows the electrochemical behavior obtained with the experiment according to Examples 2 and 3. DETAILED DESCRIPTION OF THE INVENTION
In a first aspect, the present invention relates to a redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes, to charge and discharge the battery, wherein:
- said positive electrode electrolyte comprises at least one manganese ion and at least one tin ion;
- said negative electrode electrolyte comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
The operating principle of the redox flow battery according to the present invention is based on the manganese one-electron (1 ) redox mechanism.
The Applicant surprisingly found out that tin suppresses Mn3+ disproportionation into solid manganese oxide compounds, which tend to irreversibly precipitate. In this way, the battery can advantageously operate such that the positive electrode electrolyte has an SOC of up to 90% when calculated on the assumption of one-electron, without detrimental effects on capacity and coulombic efficiency and cycle life of the battery.
Within the framework of the present description and in the subsequent claims, except where otherwise indicated, all the numerical entities expressing amounts, parameters, percentages, and so forth, are to be understood as being preceded in all instances by the term "about". Also, all ranges of numerical entities include all the possible combinations of the maximum and minimum values and include all the possible intermediate ranges, in addition to those specifically indicated herein below.
The present invention may present in one or more of the above aspects one or more of the characteristics disclosed hereinafter.
In the redox flow battery of the present invention, a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell.
Preferably, said positive electrode electrolyte and said negative electrode electrolyte are aqueous electrolytes.
The positive electrode electrolyte comprises at least one manganese ion. Preferably, said positive electrode electrolyte comprises said at least one manganese ion in a concentration of from 0.1 M to 4.2 M, more preferably in a concentration of from 1 M to 3.5 M, even more preferably in a concentration of from 1 .5 M to 3 M.
Advantageously, in said positive electrode electrolyte the redox reaction of said at least one manganese ion is:
Mn2+ <-> Mn3+ + e~ (1 ) and hence, manganese(lll) can be generated during battery charge and depleted during battery discharge. By way of the presence of a tin ion in said positive electrode electrolyte, disproportionation of Mn3+ into solid manganese oxide compounds is suppressed, thus avoiding its irreversible precipitation in the electrolyte and the resulting loss of capacity and penalty in efficiency of the battery.
The positive electrode electrolyte comprises also a tin ion.
Preferably, said positive electrode electrolyte comprises said tin ion in a concentration of from 0.1 M to 8 M, more preferably in a concentration of from 0.25 M to 6 M, even more preferably in a concentration of from 0.5 M to 5 M.
Preferably, the molar ratio between said at least one manganese ion and said tin ion ranges from 0.1 to 2, more preferably from 0.25 to 1 .5.
Preferably, said at least one tin ion is selected from the group consisting of: divalent tin ion (Sn2+) and tetravalent tin ion (Sn4+).
Said tetravalent tin ion can be advantageously added to the electrolyte as such, or prepared in situ, by adding to the electrolyte a divalent tin ion and oxidizing it to tetravalent tin (referred to also as “tin(IV)”) using a chemical oxidation method, an electrochemical oxidation method or any alternative process known to the skilled person.
Said electrolyte may further advantageously contain at least one solvation agent, for example acetonitrile.
In a preferred embodiment, therefore, the present invention refers to a redox flow battery wherein the positive electrode electrolyte comprises at least one manganese ion and at least one tetravalent tin ion.
In a further preferred embodiment, the present invention refers therefore also to a redox flow battery wherein the positive electrode electrolyte comprises at least one manganese ion and at least one tin ion selected from divalent tin ion and tetravalent tin ion, and at least one solvation agent, preferably acetonitrile.
Preferably, in the redox flow battery according to the invention, the positive electrode electrolyte has a pH of from 0 to 2.
Preferably, said positive electrode electrolyte comprises at least one acid in a concentration equal to or lower than 4 M, more preferably in a concentration equal to or lower than 3.5 M, even more preferably in a concentration equal to or lower than 3 M.
Preferably, said at least one acid is selected from the group consisting of: sulfuric acid, hydrochloric acid, phosphoric acid, diphosphoric acid, and nitric acid. More preferably, said at least acid is sulfuric acid (H2SO4).
The positive electrode electrolyte of the RFB according to the present invention advantageously comprises also at least one anion, in such quantity as to maintain the charge balance of the electrolyte. Said anion is preferably selected from the group consisting of SO42-, Ch, Br, PO42-, P2O74- and NO3-.
The positive electrode electrolyte of the RFB according to the present invention may also comprise further components, such as suspension stabilizers, cosolvents, organic solvents, surfactants, wetting, solvation and dispersing agents.
The negative electrode electrolyte of the redox flow battery according to the invention comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
As the skilled person knows, to ensure a high energy density, the redox potential difference between negative electrode electrolyte and positive electrode electrolyte should advantageously be as high as possible.
Preferably, said at least one active redox species of the negative electrode electrolyte is selected from the group consisting of: a proton, a nickel ion, a cobalt ion, an iron ion, a lead ion, a copper ion, a sulfur ion, a sulfide ion, a zinc ion, a titanium ion, a vanadium ion, a tin ion, a cerium ion, a chromium ion, an iron ion, quinones derivatives thereof, anthraquinones or derivatives thereof, viologens or derivatives thereof, indigo or derivatives thereof, naphtalenediimide or derivatives thereof, diazaanthracenedione or derivatives thereof.
Preferably, said at least one active redox species of the negative electrode electrolyte has an E° of at least 0.6V lower than the E° of the reaction (1 ). Preferably, said at least one active redox species of the negative electrode electrolyte is a proton and in said negative electrode electrolyte the redox reaction of said proton is
2H+ + 2e~ H2 (2).
As the skilled person knows, basic construction components of a redox flow battery are battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes. Said components have features and may be assembled according to well-known common praxis in the relevant art for carrying out its charging/discharging operations.
The positive electrode and the negative electrode of the redox flow battery may be made of the same material or may be made of respectively different materials. Materials suitable for the positive and/or negative electrode of the redox flow battery according to the invention are preferably selected from the group consisting of: a) a composite material comprising at least metal selected from the group consisting of: Ru, Ti, Ir, Mn, Pd, Au, Ti, Sn, Ce, Pt, an alloy thereof, and/or an oxide thereof; b) a carbon composite including the composite material according to letter a); c) a dimensionally stable electrode (DSE) including the composite material according to letter a); d) a conductive polymer; e) graphite and its derivatives, comprising nanosized materials; f) glassy carbon, g) conductive diamond or conductive diamond-like carbon (DLC); h) a nonwoven fabric made of carbon fiber; i) a woven fabric made of carbon fiber; l) a nonwoven fabric made of graphite fiber; and m) a woven fabric made of graphite fiber.
Advantageously, the positive electrode of the redox flow battery is a carbon-based electrode, preferably selected from the group consisting of: a graphite-felt, activated graphite-felt , a carbon felt, a graphite cloth, a graphite nanoparticle, a graphite nanofiber, a carbon cloth, a carbon nanotube, a carbon nanoparticle, or a carbon nanofiber activated electrode. In a preferred embodiment, the positive electrode of the redox flow battery according to the invention is a graphite-felt activated electrode.
In a still further aspect, the present invention relates also to an energy storage or delivery system comprising at least one redox-flow battery according to the first aspect of the present invention and at least one connection means apt to connect said at least one redox-flow battery to an external power source or to a load.
The advantages of the energy storage or delivery system according to this further aspect have been already outlined with reference to the above redox flow battery according to the first aspect of the invention and are not repeated herewith.
In further aspects, the present invention relates also to a method of storing electricity by means of the redox-flow battery according to the present invention, and to a method of delivering electricity by means of the redox-flow battery according to the present invention.
In particular, the present invention relates also to a method of storing electricity comprising the steps of: a) providing a redox-flow battery according to the present invention; b) electrically connecting said redox-flow battery to a power source; and to a method of delivering electricity comprising the steps of: a) providing a redox-flow battery according to according to the present invention; b) electrically connecting said redox-flow battery to a load.
The advantages of the methods according to these further aspects have been already outlined with reference to the above redox flow battery according to the first aspect of the invention and are not repeated herewith.
Features and advantages of the invention will also appear more clearly from the following non-limiting examples.
EXPERIMENTAL PART
The following electrochemical experiments according to Examples 1 -3 were carried out in a H2-Mn redox flow battery. In the redox flow battery used for the experiments, hydrogen redox reaction is used at the negative electrode electrolyte, as follows (2):
2H+ + 2e~ H2 (2). In this way, during charge, H2 was generated in the electrochemical cell. Gas bubbling revealed H2 generation during charge. During discharge, H2 was flowed into the cell at 1 .5 bar of pressure.
For the positive electrolyte formulation in Examples 1 to 3, MnSC -FW (Sigma-Aldrich; >99.0%), SnCk H2O (Fisher Scientific, 98%), SnSC (Fisher Scientific, 95%), H2SO4 (Fisher scientific, 96%) and acetonitrile (Fisher Scientific, high quality grade) were used. The positive electrolyte formulation in each example is enlisted:
• Example 1: MnSC 0.5 M; SnCk 0.125 M and H2SO4 3 M; 20 mL deionized water. In this example, the battery charge process was limited to 241 mAh (corresponding to 90%SOC calculated assuming one electron redox mechanism, with a theoretical 100%SOC of 268mAh). Charge/discharge process were performed at 0.43 mA/cm2 current density.
• Example 2 (reference example): MnSO4-0.5 M, H2SO4 3 M, 20 mL 20%v/v acetonitrile/deionized water. Charge/discharge process were performed at 0.43 mA/cm2 current density.
• Example 3: MnSO4-0.5 M, H2SO4, 3 M; 20 mL 20%v/v acetonitrile/deionized water and charged to 220 mAh at 22mA/cm2. Then, SnSCkO.125 M (Fisher Scientific, 95%) was added and, from the reaction between Mn3+ and Sn2+, Mn2+ and Sn4+ was generated. Is this example, the battery charge process was limited to 241 mAh (corresponding to 90%SOC calculated assuming one electron redox mechanism, with a theoretical 100%SOC of 268mAh). Charge/discharge process were performed at 0.43 mA/cm2 current density.
In every case, the catholyte was pumped into the cell at 100 mL/min flow rate at room temperature. Hydrogen gas flow was supplied only during discharge at a pressure of 1 .5 bar.
The redox flow battery used in the experiments is schematically depicted in Figure 1 and was composed by the components indicated by the following reference numbers:
1 - positive electrode electrolyte tank (catholyte tank);
2 - negative electrode electrolyte tank (hydrogen tank);
3 - cell;
4 - current collector; 5 - current collector;
6 - isolating plate;
7 - isolating plate;
8 - end-plate;
9 - end-plate;
10 - pump;
1 1 - membrane;
12 - catalyst;
13 - bipolar plate - flow field;
14 - bipolar plate - flow field;
15 - liquid diffusion electrode;
16 - gas diffusion electrode;
The electrochemical cell was composed of two end plates that sandwiched the rest of the components: two polypropylene isolating plates, two copper current collectors, bipolar plate with flow fields (double serpentine type for cathode and interdigit for the anode side). A 2.5 mm thick activated commercial graphite-felt (SGL-GFD 2.5 EA activated) cathode with an active area of 5x5 cm2 was used. Finally, a 5x5 cm2 active area gas diffusion layer electrode with 0.5 mg/cm2 Pt catalyst was used as anode (Quintech - BC-H100-05S).
Charge-discharge processes were carried out at 4C, with respect to the nominal capacity of the catholyte, or specified in each case. The lower and upper potential limits were 0.6V and 1 .7 V, respectively.
Example 1
In this experiment, a H2-Mn battery with 20 mL of 0.5 M Mn2+ and 0.125 M SnCk electrolyte was used with a nominal capacity of 268 mAh and charge capacity limited to 90% SoC (241 mAh) to avoid electrochemical formation of MnO2.
Figure 2 shows the cycles obtained. Reversible charge/discharge processes delivering a discharge capacity of 220 mAh, without visual detection of deposits on tubes and electrolyte tank, serves to demonstrate that Sn4+ is acting as a precipitation suppression agent. The interaction of Cl’ and related side reaction such CI2 evolution, might interfere and lead to a lower coulombic efficiency.
Examples 2 and 3
In these experiments, the possibility of using tetravalent tin obtained by a chemical oxidation of divalent tin ion in a H2-Mn battery with 0.5 M Mn2+ was shown.
In Example 2 depicted in figure 3 as Sn - Free (Ex. 2), an electrolyte with 0.5M Mn2+ and 20% of acetonitrile which was intended to act as solvation agent was used. In this case, the system reached the cutoff limit at 195 mAh, with a large quantity of precipitates on cell tubing, electrolyte tank and within the cell that made the battery unfeasible. This example showed that acetonitrile by itself does not show the role of precipitation suppression agent for the Mn system.
In Example 3 depicted in figure 3 as Sn(IV) - Cycle 1 and Cycle 2 (Ex. 3), an aqueous electrolyte containing 0.5M Mn2+, 0.125M Sn4+ obtained by in situ a chemical oxidation of divalent tin ion and 20% of acetonitrile, was used. The charge process was limited to 90% state of charge calculated for one-electron mechanism (241 mAh) and the lack of solids and precipitates in the cell tubing/tank demonstrates that Sn4+ acts as precipitation suppressing agent. The discharge capacity of 231 mAh demonstrated also the reversibility of the system which cannot be reached in absence of tin.

Claims

1 . A redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte are supplied to a battery cell including a positive electrode, a negative electrode, a membrane interposed between electrodes, to charge and discharge the battery, wherein:
- said positive electrode electrolyte comprises at least one manganese ion and at least one tin ion;
- said negative electrode electrolyte comprises at least one active redox species that couples with the manganese ion of the positive electrode electrolyte.
2. The redox flow battery according to claim 1 , wherein said positive electrode electrolyte comprises said at least one manganese ion in a concentration of from 0.1 M to 4.2 M.
3. The redox flow battery according to claim 2, wherein said positive electrode electrolyte comprises said at least one manganese ion in a concentration of from 1 M to 3.5 M.
4. The redox flow battery according to claim 3, wherein said positive electrode electrolyte comprises said at least one manganese ion in a concentration of from 1 .5 M to 3 M.
5. The redox flow battery according to any one of claims 1 -4, wherein in said positive electrode electrolyte the redox reaction of said at least one manganese ion is
Mn2+ <H> Mn3+ + e~
6. The redox flow battery according to any one of claims 1 -5, wherein said positive electrode electrolyte comprises a manganese(lll) species.
7. The redox flow battery according to any one of claims 1 -6, wherein said positive electrode electrolyte comprises said tin ion in a concentration of from 0.1 M to 8 M.
8. The redox flow battery according to claim 7, wherein said positive electrode electrolyte comprises said tin ion in a concentration of from 0.25 M to 6 M.
9. The redox flow battery according to claim 8, wherein said positive electrode electrolyte comprises said tin ion in a concentration of from 0.5 M to 5 M.
10. The redox flow battery according to any one of claims 1 -9, wherein the molar ratio between said at least one manganese ion and said tin ion ranges from 0.1 to 2.
1 1 . The redox flow battery according to claim 10, wherein the molar ratio between said at least one manganese ion and said at least a complexing agent ranges from 0.25 to 1 .5.
12. The redox flow battery according to any one of claims 1 -1 1 , wherein said tin ion is selected from the group consisting of: divalent tin ion (Sn2+) and tetravalent tin ion (Sn4+).
13. The redox flow battery according to any one of claims 1 -12, wherein said tin ion is a tetravalent tin ion.
14. The redox flow battery according to any one of claims 1 -12, wherein said tin ion is selected from the group consisting of: a divalent tin ion and a tetravalent tin ion and the positive electrode electrolyte comprises at least one solvation agent, preferably acetonitrile.
15. The redox flow battery according to any one of claims 1 -14, wherein said positive electrode electrolyte has a pH of from 0 to 2.
16. The redox flow battery according to any one of claims 1 -15, wherein said positive electrode electrolyte comprises at least one acid in a concentration equal to or lower than 4 M.
17. The redox flow battery according to claim 16, wherein said positive electrode electrolyte comprises at least one acid in a concentration equal to or lower than 3.5 M.
18. The redox flow battery according to claim 17, wherein said positive electrode electrolyte comprises at least one acid in a concentration equal to or lower than 3 M.
19. The redox flow battery according to any one of claims 16-18, wherein said at least acid is selected from the group consisting of: sulfuric acid, hydrochloric acid, phosphoric acid, diphosphoric acid, and nitric acid.
20. The redox flow battery according to claim 19, wherein said at least acid is sulfuric acid.
21. The redox flow battery according to any one of claims 1 -20, wherein said positive electrode electrolyte comprises at least one anion selected from the group consisting of SO42’, Ch, Br, PO4 2 ”, P2O74- and NO3-.
22. The redox flow battery according to any one of claims 1 -21 , wherein said at least one active redox species of the negative electrode electrolyte is selected from the group consisting of: a proton, a nickel ion, a cobalt ion, an iron ion, a lead ion, a copper ion, a sulfur ion, a sulfide ion, a zinc ion, a titanium ion, a vanadium ion, a tin ion, a cerium ion, an iron ion, quinones derivatives thereof, anthraquinones or derivatives thereof, viologens or derivatives thereof, indigo or derivatives thereof, naphtalenediimide or derivatives thereof, diazaanthracenedione or derivatives thereof.
23. The redox flow battery according to any one of claims 1 -22, wherein said at least one active redox species of the negative electrode electrolyte has an E° of at least 0.6V lower than the E° of the reaction:
Mn2+ <H> Mn3+ + e
24. The redox flow battery according to any one of claims 1 -22, wherein said at least one active redox species of the negative electrode electrolyte is a proton and in said negative electrode electrolyte the redox reaction of said proton is
2H+ + 2e~ H2 .
25. The redox flow battery according to claim 1 -23, wherein said positive electrode and/or said negative electrode are made of a material selected from the group consisting of: a) a composite material comprising at least metal selected from the group consisting of: Ru, Ti, Ir, Mn, Pd, Au, Ti, Sn, Ce, Pt, an alloy thereof, and/or an oxide thereof; b) a carbon composite including the composite material according to letter a); c) a dimensionally stable electrode (DSE) including the composite material according to letter a); d) a conductive polymer; e) graphite and its derivatives, comprising nanosized materials; f) glassy carbon, g) conductive diamond or conductive diamond-like carbon (DLC); h) a nonwoven fabric made of carbon fiber; i) a woven fabric made of carbon fiber; l) a nonwoven fabric made of graphite fiber; and m) a woven fabric made of graphite fiber.
26. The redox flow battery according to any one of claims 1 -25, wherein said positive electrode is a carbon-based electrode and is selected from the group of: a graphite-felt, an activated graphite-felt, ta carbon felt, a graphite cloth, a graphite nanoparticle, a graphite nanofiber, a carbon cloth, a carbon nanotube, a carbon nanoparticle, or a carbon nanofiber activated electrode.
27. The redox flow battery according to claim 26, wherein said carbon-based electrode is a graphite-felt activated electrode.
28. A method of storing electricity comprising the steps of: a) providing a redox-flow battery according to any one of claims 1 to 27; b) electrically connecting said redox-flow battery to a power source.
29. A method of delivering electricity comprising the steps of: a) providing a redox-flow battery according to any one of claims 1 to 27; b) electrically connecting said redox-flow battery to a load.
PCT/EP2022/064424 2022-05-27 2022-05-27 Redox flow battery WO2023227227A1 (en)

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Citations (4)

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Publication number Priority date Publication date Assignee Title
EP2387092A1 (en) * 2010-03-12 2011-11-16 Sumitomo Electric Industries, Ltd. Redox flow battery
WO2018025737A1 (en) * 2016-08-02 2018-02-08 住友電気工業株式会社 Redox flow battery and method for operating redox flow battery
CN112805244A (en) * 2018-08-30 2021-05-14 帝化株式会社 Titanyl sulfate hydrate powder, method for producing aqueous solution of titanyl sulfate, method for producing electrolyte, and method for producing redox flow battery
CN113707925A (en) * 2021-08-24 2021-11-26 复旦大学 Tin-manganese aqueous flow battery

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2387092A1 (en) * 2010-03-12 2011-11-16 Sumitomo Electric Industries, Ltd. Redox flow battery
WO2018025737A1 (en) * 2016-08-02 2018-02-08 住友電気工業株式会社 Redox flow battery and method for operating redox flow battery
CN112805244A (en) * 2018-08-30 2021-05-14 帝化株式会社 Titanyl sulfate hydrate powder, method for producing aqueous solution of titanyl sulfate, method for producing electrolyte, and method for producing redox flow battery
US20210309536A1 (en) * 2018-08-30 2021-10-07 Tayca Corporation Titanyl sulfate hydrate powder, method for producing titanyl sulfate hydrate powder, method for producing aqueous titanyl sulfate solution, method of producing electrolyte solution, and method for producing redox flow battery
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