WO2017067992A1

WO2017067992A1 - Electrolyte-circulating redox battery operating with a single redox compound

Info

Publication number: WO2017067992A1
Application number: PCT/EP2016/075107
Authority: WO
Inventors: Thibaut Gutel; Lionel Dubois; Arnaud Morin
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2015-10-20
Filing date: 2016-10-19
Publication date: 2017-04-27
Also published as: FR3042651A1; FR3042651B1

Abstract

The invention relates to electrolyte-circulating redox battery cells including: a first compartment including a positive electrode supplied with power by an organic redox compound in an electrolyte, and a second compartment including a negative electrode supplied with power by an organic redox compound in an electrolyte, said first compartment and said second compartment being separated from one another by an ion-conducting membrane. The invention is characterized in that the organic redox compound of the first compartment and the organic redox compound of the second compartment are identical and comprise, respectively, at least one group capable of capturing electrons and at least one group capable of giving up electrons, said organic redox compound including both, as a group or groups capable of capturing electrons, at least one group selected from among the conjugated carbonyl groups, the carboxylate groups and the disulfide groups and, as a group or groups capable of giving up electrons, at least one group selected from among the enolic or enolate groups and the nitroxide groups.

Description

REDOX BATTERY WITH ELECTROLYTE CIRCULATION OPERATING WITH A COMPOUND

UNIQUE REDOX

DESCRIPTION

TECHNICAL AREA

The present invention relates to cells of redox batteries circulating electrolytes (also called redox flow batteries, which corresponds to the English terminology "Redox Flow Batteries" or RFB) including specific electrolytes, which allow in particular to obtain good performance in terms of energy density and power.

Due to their ability to store energy in a simple and efficient way, their long lifetimes and their moderate costs, these batteries are one of the most promising technologies for stationary storage of intermittent renewable energies and can find application, in all areas requiring an autonomous power source, such as the field of automotive power supply.

Electro-circulating redox batteries constitute a particular class of electrochemical energy storage devices, the redox characteristic referring to the oxidation and reduction reactions causing the supply of energy during the discharge process. which reactions take place in separate compartments, in which separate electrolytes circulate.

More specifically, as illustrated in FIG. 1 appended hereto, a single-cell electrolyte circulation redox battery 1 (that is to say that the battery comprises only a single cell) conventionally comprises the assembly of two half-cells or compartments, namely:

a first compartment 3 comprising a positive electrode (or cathode), generally porous, fed by a first electrolyte 7 comprising a redox compound comprising at least one group capable of capturing electrons (ie, in other words, at least one oxidizing group), which is therefore reduced during the discharge process, which first electrolyte is supplied to the compartment via a reservoir 9 storing this electrolyte, which is connected to the first compartment via a supply line 11 provided with a pump 13 and also via a discharge pipe 15 responsible for rerouting the electrolyte from the compartment to the tank;

a second compartment 17 comprising a negative (or anode), generally porous, electrode 19 fed by a second electrolyte 21 comprising a redox compound comprising at least one group capable of giving off electrons (ie, in other words, at least one reducing unit), which therefore undergoes oxidation during the discharge process, which second electrolyte is supplied to the compartment via a reservoir 23 storing this electrolyte, which is connected to the second compartment via a supply pipe 25 provided with a pump 27 and also via an exhaust pipe 29 responsible for rerouting the electrolyte compartment to the tank.

The first compartment and the second compartment are separated from each other by an ionic conductive membrane 31, whose role is to ensure the electroneutrality of the system while avoiding the migration of redox compounds from the first compartment to the second compartment and vice versa.

The first electrolyte can be called a catholyte, while the second electrolyte can be called anolyte.

From an operational point of view, if the redox compound of the first compartment c ^{Y +} and the redox compound of the second compartment A ^{x +} are named, the electrochemical half-reactions occurring at the electrode / electrolyte interfaces can be represented by the reactions following:

* at the positive electrode / electrolyte interface:

_C Y + + _E - _C (Y-D +

* at the negative electrode / electrolyte interface:

A ^{x +} ^ A < ^{x + 1} > ⁺ + e ^"

the electrons from this last half-reaction circulating from the negative electrode to the positive electrode via the external circuit 33, which is thus supplied with electricity.

The amount of redox compounds subjected to these reactions can be adjusted according to energy or capacity requirements and more specifically by playing the volume of reservoirs that feed the compartments into suitable redox compounds, while the size of the electrodes and, more generally, the compartments can be adjusted according to power requirements. Also, redox batteries with electrolyte circulation advantageously make it possible to decouple between power and capacity.

To date, existing electrolyte-circulating redox batteries operate with aqueous electrolytes employing in particular a vanadium-based redox couple. If this type of battery could be used for storage at the scale of an electricity distribution network, the diffusion of these batteries is slowed down because of the limited vanadium resources generating, as a result, high costs of supply, toxicity problems related to the presence of large quantities of solutions of vanadium salts in solution and also solubility of these same salts. Alternatively, as a variant of vanadium, it has been proposed to use a bromine-based redox couple, with however the disadvantage of a high toxicity and severe corrosion problems difficult to manage, proscribing all domestic applications and curbing the large scale industrial applications.

Moreover, it requires the presence, in each of the compartments, two distinct redox compounds, which requires, at the same time, to set up two separate tanks and significant costs, which ensue for the installation of such a battery.

In view of the foregoing, the inventors have set themselves the goal of proposing new redox batteries that make it possible to overcome all or some of the aforementioned drawbacks and, in particular, in particular, the cost problems related to the need to use separate redox compounds for each of the compartments; and installation complexity issues related to the need for separate reservoirs.

STATEMENT OF THE INVENTION

Thus, the invention relates to a redox battery cell with electrolyte circulation comprising: a first compartment comprising a positive electrode fed by an organic redox compound comprised in an electrolyte; and

a second compartment comprising a negative electrode fed by an organic redox compound included in an electrolyte,

said first compartment and said second compartment being separated from each other by an ionic conductive membrane, characterized in that the organic redox compound of the first compartment and the organic redox compound of the second compartment are identical and respectively comprise at least a group capable of collecting electrons and at least one group capable of giving off electrons, said organic redox compound comprising, advantageously, both as a group (s) capable of capturing electrons, at least one group chosen from the conjugated carbonyl groups, the carboxylate groups and the disulfide groups and, as group (s) capable of giving off electrons, at least one group chosen from enolic or enolate groups and nitroxide groups.

Also, the use both at the level of the first compartment and the second compartment of the same redox compound, which is capable of ensuring, by the presence of at least one group capable of capturing electrons and at least one suitable group to give up electrons, the role of oxidizing active material and reducing active material provides the following advantages:

a reduction in costs linked to this simplification and also to the fact that only one redox compound is to be procured or produced; and

elimination of the problems of cross-pollution between the two compartments, as may be the case with cells operating with two distinct compounds and thus fed via two separate tanks.

By organic compound, is meant, conventionally, a compound of carbon chemistry, comprising carbon and hydrogen atoms and one or more heteroatoms selected from oxygen, nitrogen, sulfur, phosphorus, these atoms and these heteroatoms being only linked by covalent bonds, this compound may be in the form of salts.

By oxidizing active material, it is specified that it is the redox compound which picks up one or more electrons, via the aforementioned group, during the reduction step occurring at the positive electrode of the first compartment during the discharge process.

By reducing active material, it is specified that it is the redox compound which yields one or more electrons, via the aforementioned group, during the oxidation step occurring at the negative electrode of the second compartment during the discharge process.

Ion conducting membrane is understood to mean a membrane capable of conducting ions, such as, for example, cations such as protons (in which case we may speak of a proton-conducting membrane or proton conducting membrane), Li ⁺ , Na ⁺ cations. , K ⁺ , Mg ²⁺ , ammonium cations or anions such as OH ^" , amide anions.

The redox compound used in the cells of the invention due to the presence of two types of groups as defined above can be described as a biredox compound, since the group capable of capturing electrons belongs to a first redox couple and the second group capable of giving up electrons belongs to a second redox couple.

Advantageously, the group capable of capturing electrons belongs to a redox couple having a redox potential greater than the redox potential of the redox couple to which belongs the group capable of giving up electrons and, preferably, greater than 1 V (for example, ranging from 1 at 5 V), whereby the resulting cell is capable of delivering a voltage greater than 1 V (for example, ranging from 1 to 5 V).

Also, during the discharge process, in the first compartment, the group capable of capturing electrons undergoes a reduction step while, in the second compartment, the group capable of giving off electrons undergoes an oxidation step, thus generating a cell voltage producing electricity.

Whether for the redox compound present in the first compartment or for the redox compound present in the second compartment, it may be included in the electrolyte at a concentration that may range from 0.1 to 10 mol.L ¹ , given that the higher the redox compound concentration in the first and second compartments, plus it allows to increase the densities of energy and power.

Suitable redox compounds are, advantageously, compounds in which the group or groups capable of capturing electrons are:

conjugated carbonyl groups;

carboxylate groups, such as lithiated carboxylate groups; or disulfide groups;

and / or in which the group or groups capable of giving off electrons are:

enolate or enolate groups; or

nitroxide groups.

Compounds meeting this specificity are compounds comprising, at the same time, at least one group chosen from conjugated carbonyl groups; carboxylate groups, disulfide groups and at least one group selected from enol or enolate groups, nitroxide groups.

It is specified that by conjugated carbonyl group is meant a carbonyl group conjugated with a double bond, such a group being schematized by the following formula:

It is specified that, by enol or enolate group, is meant a group respectively corresponding to the following formulas:

wherein X represents a monovalent cation such as lithium. Redox compounds corresponding to the abovementioned specificities may be quinone compounds, which designate hydrocarbon compounds comprising one or more benzene rings, on which two hydrogen atoms are replaced by two oxygen atoms, thus each forming a double bonding with a carbon atom, such compounds thus comprising two electron-withdrawing conjugated carbonyl groups, which quinone compounds must also be substituted by at least one substituent comprising at least one group capable of giving off electrons, such as a group nitroxide.

The redox compounds of the family of quinone compounds have the advantage of being of low environmental impact, of being often cheap and can be of biological origin (certain quinone compounds found in plants, fungi, bacteria even in some animals).

More specifically, the quinone compounds may be chosen from benzoquinone compounds (such as 1,4-benzoquinone compounds, 1,2-benzoquinone compounds), naphthoquinone compounds (such as 1,4-naphthoquinone compounds, , 2-naphthoquinones, 1,5-naphthoquinone compounds, 1,7-naphthoquinone compounds, 2,3-naphthoquinone compounds, 2,6-naphthoquinone compounds) and anthraquinone compounds (such as anthraquinones, 1,2-anthraquinone compounds, 1,4-anthraquinone compounds, 1,10-anthraquinone compounds, 2,9-anthraquinone compounds, 1,5-anthraquinone compounds, 1,7-anthraquinone compounds, 2,3-anthraquinone compounds, 2,6-anthraquinone compounds), these compounds comprising at least one substituent comprising at least one group capable of giving off electrons, such as a nitroxide group and, optionally, at least one other substituent chosen from - N (CH ₃ ) ₂ , -NH ₂ , -OR, -OH, -SH, -CH ₃ , -SiR ₃ , -F, -Cl, -C ₂ H ₃ , -CHO, -COOCH ₃ , -CF ₃ , -CN, -COOH, -PO ₃ H ₂ , -SO ₃ H, NO ₂ , -COOM, -COOR, -SO ₃ M, -COR, -C = NCHR ^' R ^" , with R,

R ^' and R ^" represent, independently of one another, H or an alkyl group and M represents Li, Na, K or Mg.

Even more specifically, it may be an anthraquinone compound, such as a 9,10-anthraquinone compound, comprising at least one substituent comprising at least one group capable of giving off electrons, a particular redox compound having the characteristics mentioned above, corresponding to the following formula (I):

(I)

wherein X is an organic spacer group or a single bond, i.e. the tetramethylpiperidinyloxy group is directly bonded to one of the ring carbon atoms.

For accuracy, the -X- link intersecting the ring indicates that the tetramethylpiperidinyloxy group can be bonded to any of the carbon atoms of the anthraquinone ring either directly or via the organic spacer group.

More specifically, this redox compound can meet the following formula (II):

(M)

with X being as defined above.

When X represents an organic spacer group, it may be an imidazolium group, the counterion of which may be, for example, a halogen anion, a TFSI anion (TFSI being the abbreviation corresponding to bis (trifluoromethane) sulfonimide), an anion TfO (TfO being the abbreviation corresponding to trifluoromethanesulfonate). During operation of the electrolyte circulating redox battery cell (i.e., when it is in the discharge process), the specific redox compound mentioned above undergoes a reduction reaction at the electrode the first compartment, this reaction being represented by the following chemical equation:

M ⁺ representing a cation;

while the same redox compound undergoes an oxidation reaction at the negative electrode of the second compartment, which reaction can be represented by the following chemical equation:

M ⁺ representing a cation.

Other redox compounds corresponding to the abovementioned specificities may be quinone compounds in their enolate form, that is to say in which the conjugated carbonyl groups = C-CO- are converted into -C = COX- groups (with X being a monovalent cation, such as lithium), which quinone compounds are also substituted by at least one group capable of capturing electrons, such as a carboxylate group, and optionally by another substituent chosen from -N (CH 3) 2, -NH ₂ , -OR, -OH, -SH, -CH ₃ , -SiR ₃ , -F, -Cl, -C ₂ H ₃ , -CHO, -COOCH ₃ , -CF ₃ , -CN, -COOH, -PO ₃ H ₂ , -SO ₃ H, NO ₂ , -COOM, -COOR, -SO 3 M , -COR, -C = NCHR ^' R ^" , with R, R ^' and R ^" representing, independently of one another, H or an alkyl group and M representing Li, Na, K or Mg.

More specifically, it may be a benzoquinone compound in enolate form substituted with at least one carboxylate group, and even more specifically a 1,4-benzoquinone compound substituted with at least one carboxylate group (for example, two carboxylate groups). and optionally another substituent such as those defined above, an example of this type corresponding to the following formula (III):

(III)

in which X ¹ to X ⁴ represents a lithium cation and X ⁵ and X ⁶ represent, independently of one another, a hydrogen atom or a -SO 3 H group, a particular compound corresponding to this specificity being that of following formula:

During the operation of the redox battery cell with electrolyte circulation (that is to say when it is in the process of discharge), the compound The specific redox mentioned above undergoes a reduction reaction of the carboxylate groups at the positive electrode of the first compartment, this reaction being able to be represented by the following chemical equation.

while the same redox compound undergoes an oxidation reaction of the enolate groups at the negative electrode of the second compartment, this reaction being able to be represented by the following chemical equation:

In addition, the electrolyte advantageously comprises an aqueous acid solution, intended to provide, where appropriate, the protons necessary for the redox reactions and, in addition, to ensure the proton conduction of the electrolyte.

For example, it may be an aqueous solution of sulfuric acid, at a concentration ranging from 0.1 to 10 M, and more specifically 1M.

Advantageously, the electrolyte of the first compartment and the electrolyte of the second compartment are identical, that is to say that they respond to the same composition.

As mentioned above, the electrolyte circulation battery cell comprises, in its first compartment and in its second compartment. compartment, respectively a positive electrode and a negative electrode.

By positive electrode is meant, conventionally, in the foregoing and the following, the electrode which acts as a cathode, discharge process, that is to say, in other words, which is the seat a reduction reaction.

By negative electrode is meant, conventionally, in what precedes and what follows, the electrode which acts as anode, when the generator delivers current (that is to say when it is in the process of discharge ), that is, in other words, which is the seat of an oxidation reaction.

Whether for the positive electrode or the negative electrode, from the point of view of the constituent material, it may consist of at least one carbon material and, more specifically, a carbon fiber material (such as a fabric , felt or paper), the fibrous nature of the material having the advantage of being easily impregnated by the electrolyte and therefore a good supply of this electrode by the electrolyte.

In addition, the positive or negative electrode may comprise another carbon material, such as carbon black, which has the advantage, in particular, of improving the electronic conductivity of the positive electrode. It may further comprise an ionic conductive ionomer compound, which may be of the same nature as the ionic conductive membrane.

From a structural point of view, the positive or negative electrode may be in the form of a layer, for example carbon fibers, a first face of which is in contact with the ionic conductive membrane.

This layer can also be advantageously, in contact, at a second face opposite to the first face, with a distribution plate of the electrolyte from a tank external to the cell, etched with a serpentiform channel or several parallel channels, which will supply the electrolyte electrode over its entire surface.

The ionic conductive membrane is conventionally intended to allow the physical separation of the first compartment and the second compartment and must, at the same time, allow the ions produced during the reactions to pass through. redox, to maintain the electroneutrality of the cell while at the same time preventing the migration of redox organic compounds.

From a point of view of the constituent material, the membrane may be an ionically conductive polymer.

Effective candidates for this type of polymer are perfluorosulphonated polymers, such as those deposited under the NAFION® brands of Dupont de Nemours.

These polymers comprise a main chain (also called skeleton) comprising a repeat unit of the tetrafluoroethylene type and a repeating unit derived from the tetrafluoroethylene type grafted with a pendant chain having a terminal group -SO 3 H.

Finally, the invention also relates to an electrolyte circulation battery comprising at least one cell as defined above.

When the battery comprises a single cell, it can be described as single-cell and when the battery comprises several cells, it can be described as multicellular, the different cells can be associated in series and / or in parallel.

Other features and advantages of the invention will emerge from the additional description which follows and which relates to a particular embodiment.

Of course, this additional description is only given as an illustration of the invention and does not in any way constitute a limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of an electrolyte circulation battery.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

EXEM PLE

This example illustrates an electrochemical cell conforming to the invention comprising two compartments: a first compartment and a second compartment comprising, respectively, a positive electrode and a negative electrode, which compartments are separated by a lithium ion conductive polymer membrane and each of these compartments being powered by a specific electrolyte from a dedicated tank.

The positive electrode and the negative electrode consist of a paper-like carbon material (more specifically, the Toray 120 range), on which is deposited a layer comprising a mixture of carbon black (Vulcan XC-72 type). at 4 mg / cm ² ) and an ionic conductive ionomer compound (of the Nafion D2020 12 mg / cm ^{2 type} ).

The positive electrode and the negative electrode are pressed, via the coated surface of the aforementioned layer, on each side of the polymeric Nafion conductive membrane 115.

The other side of the electrodes is in contact with a plate whose function is to supply the electrolyte.

The electrolyte of the first compartment and the electrolyte of the second compartment are identical electrolytes comprising, as redox compound, a compound of the following formula:

Claims

An electrolyte circulating redox battery cell comprising:

a first compartment comprising a positive electrode fed by an organic redox compound comprised in an electrolyte; and

said first compartment and said second compartment being separated from each other by an ionic conductive membrane, characterized in that the organic redox compound of the first compartment and the organic redox compound of the second compartment are identical and respectively comprise at least a group capable of collecting electrons and at least one group capable of giving off electrons, said organic redox compound comprising, at the same time, as group (s) capable of capturing electrons, at least one group chosen from the groups conjugated carbonyls, carboxylate groups and disulfide groups and, as a group (s) capable of yielding electrons, at least one group selected from enol groups or enolates and nitroxide groups.

2. redox battery cell according to claim 1, wherein the group capable of capturing electrons belongs to a redox couple having a redox potential greater than the redox potential of the redox couple, which belongs to the group capable of giving up electrons.

Redox battery cell according to claim 1 or 2, in which the group capable of capturing electrons belongs to a redox couple having a redox potential greater than 1 V relative to the redox potential of the redox couple, to which belongs the group capable of capturing electrons. give up electrons.

The redox battery cell according to any one of the preceding claims, wherein the redox compound is a quinone compound, which is a quinone compound substituted with at least one substituent comprising at least one group capable of giving off electrons.

A redox battery cell according to any one of the preceding claims, wherein the redox compound is a quinone compound selected from benzoquinone compounds, naphthoquinone compounds and anthraquinone compounds, these compounds comprising at least one substituent comprising at least one group able to give up electrons.

The redox battery cell according to any of the preceding claims, wherein the redox compound is an anthraquinone compound comprising at least one substituent comprising at least one group capable of giving off electrons.

The redox battery cell according to any of the preceding claims, wherein the specific redox compound has the following formula (I):

(I)

wherein X is an organic spacer group or a single bond.

The redox battery cell according to any one of the preceding claims, wherein the redox compound has the following formula (II):

with X being as defined in claim 7.

The redox battery cell of claim 7 or 8, wherein X is an imidazolium group.

10. A redox battery cell according to any of claims 1 to 3, wherein the redox compound is a quinone compound in enolate form, substituted by at least one group capable of capturing electrons.

The redox battery cell of any one of claims 1 to 3 and 10, wherein the redox compound is a benzoquinone compound in enolate form substituted with at least one carboxylate group.

12. Redox battery cell according to any one of claims 1 to 3 and 10 or 11, wherein the redox compound is a compound of formula (III) below:

in which X ¹ to X ⁴ represents a lithium cation and X ⁵ and X ⁶ represent, independently of one another, a hydrogen atom or a group

13. Lithium battery comprising at least one electrochemical cell according to any one of claims 1 to 12.