WO2017178252A1

WO2017178252A1 - System and method for storing and releasing electrochemical energy with a flow of redox polymer particles

Info

Publication number: WO2017178252A1
Application number: PCT/EP2017/057719
Authority: WO
Inventors: Julien Bernard; David Pasquier; Valerie Sauvant-Moynot
Original assignee: IFP Energies Nouvelles
Priority date: 2016-04-14
Filing date: 2017-03-31
Publication date: 2017-10-19
Also published as: FR3050327A1; FR3050327B1

Abstract

The invention relates to a novel type of redox flow battery, termed a "redox particle flow" battery, in which the active positive and negative materials, e.g. the redox pairs employed at the positive electrode and the negative electrode, are solid-phase redox polymers. The redox polymers are formed as electrically conductive particles which are transported, gradually as needed, into the electrolyte-bathed reaction zone, where they form a sediment and percolate electrically to the current collectors, enabling the redox reactions to take place and the operation of the battery.

Description

SYSTEM AND METHOD FOR STORAGE AND RESTITUTION OF ELECTROCHEMICAL FLOW ENERGY OF REDOX POLYMER PARTICLES

Field of the invention

The present invention relates to the field of energy storage and electrochemical storage systems, in particular redox flow or redox flow batteries in which the active ingredients are circulated and stored in external tanks.

In particular, the present invention relates to the use of redox polymers as active ingredients in a particular type of redox flow battery, called "pellet" or "redox particle flow", in which the active ingredients positive and negative are put in the form of electrical conducting grains circulating and sedimenting respectively in the cathode and anode compartments of the battery. General context

The use of redox polymers as active ingredients is known in the field of batteries. Among the interests displayed in their use are the search for lower toxicity than that of certain metal-based materials, the search for better capacitive performance or the manufacture of batteries at lower costs.

For example, conventional electrochemical accumulators are known for reversibly storing electrical energy in chemical form, comprising redox polymers as electro-chemically active material. A conventional accumulator is a closed and compartmentalized system comprising at least two compartments each comprising a current collector, for the positive and negative electrodes. These compartments are separated by a porous separator and ion conductor that electronically isolates the positive electrode from the negative electrode. In a closed and sealed container, the liquid electrolyte that impregnates the active materials of the positive and negative electrodes as well as the separator, allows solvent molecules and ionic charges to migrate within the system and to equilibrate. When the accumulator is placed in a closed electrical circuit, the active material of each electrode in contact with the electrolyte is the seat of reversible electrochemical reactions of oxidation (which leads to a loss of electrons) and reduction (which leads to to a gain of electrons). In this configuration, redox polymers have been implemented as active material of electrodes, formulated with conductive fillers as needed to ensure good electronic conduction and form a deposit on the current collectors. The assembly then constitutes an electrode. These conventional accumulators employing redox polymers have advantages in terms of electrochemical capacity, implementation and non-toxicity. However, a major disadvantage encountered in these conventional accumulators employing redox polymers consists of stability problems over time. In particular, redox polymers tend to dissolve in the solvent of the electrolyte, which limits their use in cycling in batteries in the long term.

Flow batteries are also known using redox polymers as electro-chemically active material. A flow battery is characterized by the circulation of reagents (an oxidant on one side and a reductant on the other) from storage tanks to the double compartment electrochemical cell where they are separated by a separator and react in the presence of the positive and negative electrodes. The redox polymers are typically used in liquid form, dissolved in a solvent, as for example described in the patent application WO14026728A. In the application WO14026728A, the electroactive compounds are indeed high molecular weight materials such as redox polymers or redox oligomers, and the membrane is a steric exclusion membrane for separating the high molecular weight compounds from the solvent. However, the energy density of such redox flux batteries is related to the solubility of the polymer in the electrolyte, and thereby is limited by the solubilization of the active ingredients. If the redox polymer is concentrated, then there is an increase in the viscosity of the medium which causes pumping problems and leads to a lower energy efficiency.

The implementations of the redox polymers in known electrochemical energy storage systems are unsatisfactory. Some degrade the capacitive properties of these materials and do not make it possible to sustainably fulfill the intended reversible storage function, while others have problems of power density and / or energy density and / or pumping.

Thus, there is a need to provide an electrochemical energy storage and retrieval system employing redox polymers, which overcomes at least in part the problems of the prior art described. Furthermore, the Applicant has described in the French patent application filed under number 15 / 56.883 redox batteries with redox flow of a new type, called "redox particle stream" or "redox flow pellet" batteries, wherein the positive and negative active materials, eg the redox couples employed at the positive electrode and the negative electrode, are in the solid phase. The active materials are put into the form of electrically conductive grains which are transported as and when required into the reaction zone bathed with an electrolyte, where they sediment and percolate electrically up to the current collectors, which makes it possible to carry out the redox reactions and battery operation. These batteries typically use redox torques of conventional accumulators, for example the Pb / PbSO ₄ and PbO ₂ / PbSO ₄ pairs used in lead-acid type batteries, or redox couples conventionally used in NiMH or alkaline type batteries. NiCd or lithium ion batteries (Li-ion).

The present invention relates to the use of redox polymers as active ingredients in this new type of flux redox battery.

Objectives and summary of the invention

The present invention aims in particular to provide an electrochemical storage and electrochemical energy recovery system which has improved performance in terms of power and energy density, in comparison with known systems using redox polymers, and which can be cycled sustainably without encountering the limitations of the state of the art.

In general, the present invention aims at providing a system for storing and restoring electrochemical energy with a redox flow making it possible to use redox polymers as electroactive material:

- while improving safety and limiting the environmental risks associated with the storage of toxic and / or flammable liquids;

allowing, as conventional redox flow batteries, the decoupling between the power and the energy capacity of the system, and which can have a high energy capacity according to the size of the active substance tanks used;

- To reduce the energy cost of pumping the electrolyte if such a pumping is envisaged. Thus, to achieve at least one of the above objectives, among others, the present invention proposes, according to a first aspect, a system for storing and restoring electrochemical energy with a redox particle stream comprising:

at least one electrochemical cell comprising an enclosure formed by an anode compartment and a cathode compartment containing an electrolyte and separated by an electrically insulating and ion-permeable separator contained in the electrolyte, said separator being disposed along a substantially vertical axis;

said anode compartment comprising a negative electrode in the form of a bed of a first type of sedimented redox particles immersed in the electrolyte, said anode compartment being defined between said separator and a first electrical current collector in contact with said negative electrode; and said anode compartment comprising an inlet at its top and an outlet at its base for respectively receiving and discharging an incoming stream and a stream exiting the first type of redox particles;

said cathode compartment comprising a positive electrode in the form of a bed of a second type of sedimented redox particles immersed in the electrolyte, said cathode compartment being defined between said separator and a second electrical current collector in contact with said positive electrode; and said cathode compartment including an inlet at its top and an outlet at its base for respectively receiving and discharging an incoming stream and a stream exiting the second type of redox particles;

o said beds of the first and second type of particles being movable in a gravity flow from the inlet to the outlet of each of the anode and cathode compartments, and said first type and second type particles being electrically conductive;

means for regulating the incoming flows and outflows of the first type and second type redox particles;

a first storage tank for the first type of redox particles, said first tank being in communication with the anode compartment;

a second storage tank for the second type of redox particles, said second tank being in communication with the cathode compartment;

said first type redox particles and / or said second type redox particles comprising a redox polymer. According to one embodiment, the redox polymer is insoluble in the electrolyte or shaped so as not to be soluble in the electrolyte.

According to one embodiment, the first type and / or second type redox particles are solid and porous, preferably substantially spherical, grains formed by foaming said redox polymer, and comprising an electronic percolator, such as carbon black.

According to this embodiment, the grains are preferably covered with a solid layer of electrically conductive material, porous and permeable to the electrolyte and its ions.

According to another embodiment, the first type and / or second type redox particles are solid and porous, preferably substantially spherical, grains formed by a conductive porous support comprising a redox polymer.

According to this embodiment, the first type and / or second type redox particles are obtained by grafting a redox polymer onto said porous support, or by crosslinking said redox polymer in the porous support, or by precipitation of said redox polymer in said porous support, or by coating or impregnation of the porous support with an ink comprising said redox polymer and an electronic percolator.

The porous support may be a sphere made of an electronically conductive material and enclosing said redox polymer, preferably a sphere of metal foam or carbon foam, said carbon foam being preferably graphitic.

According to one embodiment, the redox polymer has a vinyl backbone chosen from the group consisting of polyacrylates, polymethacrylates, polyacrylamide and polystyrene, and comprises redox groups chosen from the group consisting of nitroxide, quinone and quinoxaline radicals. bipyridines, eg viologenes, verdazyl and ferrocenes.

According to one embodiment, the polymer is electronically conductive, preferably selected from the group consisting of polyaniline, polypyrrole, polythiophene.

According to one embodiment, the first type redox particles have a size at least 10 times smaller than a first width defined between the separator and the first current collector, and the second type of redox particles have a size at least 10 smaller than a second width defined between the separator and the second current collector, the redox particles of the first type and the redox particles of the second type preferably having a mean diameter of between 100 μηι and 5 mm, and more preferably between 500 μηι and 2 mm.

According to one embodiment, the first type of redox particles and the second type of redox particles each comprise a redox polymer.

According to one embodiment, the system further comprises means for circulating the electrolyte to circulate the electrolyte out of said enclosure.

According to one embodiment, the system further comprises:

a tank containing the electrolyte and comprising a first zone communicating with the outlet of the anode compartment to collect the outgoing flow of the first type of redox particles and a second zone communicating with the outlet of the cathode compartment to collect the outgoing flow of the second type of redox particles, said first and second zones being separated by a wall;

a first pipe provided with a first pump for transporting a first mixture comprising the electrolyte and the first type redox particles from the first zone of the tank to the first tank; and

a second pipe provided with a second pump for transporting a second mixture comprising the electrolyte and the second type redox particles from the second zone of the tank to the second tank;

separating means, such as a sieve, in each of the reservoirs for separating the particles of the electrolyte contained in each of the first and second mixtures,

feed means respectively connecting the first reservoir to the anode compartment and the second reservoir to the cathode compartment for supplying said anode compartment with first type redox particles and said second type redox particles cathode compartment, said supply means comprising the means for regulating the influx of redox particles;

means for introducing the electrolyte from the reservoirs into said tank;

and wherein the electrolyte circulation means comprises the first and second conduits and the means for introducing the electrolyte.

According to another embodiment, the system further comprises:

a device for recovering the electrolyte and redox particles, said recovery device being positioned downstream of the outlets of the anode and cathode compartments, said recovery device comprising a container provided with a bottom surmounted by a sieve for retaining the redox particles of first type and second type in two zones separated from the container each receiving a type of redox particles, and to let the electrolyte pass into the bottom of the container; and

a pipe system provided with a pump for transporting the electrolyte from the bottom of the container to the head of the compartments of the enclosure;

the electrolyte circulation means comprising said pipe system.

According to one embodiment, the system further comprises:

first means of transporting the first type of redox particles from said tank to the first tank;

second means of transporting the second type of redox particles from said tank to the second tank;

supply means respectively connecting the first reservoir to the anode compartment and the second reservoir to the cathode compartment for supplying said anode compartment with particles of the first type and said cathode compartment with particles of the second type, said supply means comprising the means for regulating the incoming flow of particles.

The first and / or second means of transport may be mechanical, and preferably comprise a worm system.

According to one embodiment, the first storage tank and / or the second storage tank comprises means for mixing the particles.

According to a second aspect, the present invention proposes a method for storing and restoring electrochemical energy implementing a system according to the invention, in which:

the first type of electrically conductive redox particles is circulated between the first storage tank and the anode compartment of the electrochemical cell, and the second type of electrically conductive redox particles is circulated between the second storage tank and the cathode compartment of the electrochemical cell; said cell, said first type of particles and / or said second type of particles comprising a redox polymer; redox reactions are carried out in the anode and cathode compartments of said cell and the current generated by the redox reactions is collected by means of the current collectors in order to store or restore electrochemical energy;

the incoming and outgoing flows are determined for each of the first and second types of particles so as to create a gravity flow of said particles in each of said anode and cathode compartments to form the moving bed of sedimented particles such as the redox reactions and the Electrical conduction is ensured by percolation of electrons and electrolyte into the sedimented particles of the moving bed.

According to a third aspect, the present invention proposes the use of a system for storing and restoring electrochemical energy according to the invention, preferably comprising a plurality of electrochemical cells, for the stationary storage of electrical energy, preferably the stationary storage of electrical energy from renewable energy sources, preferably from photovoltaic or wind systems.

Other objects and advantages of the invention will appear on reading the following description of examples of particular embodiments of the invention, given by way of non-limiting examples, the description being made with reference to the appended figures described herein. -after. Brief description of the figures

Figure 1 is a schematic sectional view of the system for storing and restoring the electrochemical energy according to the invention.

FIG. 2 is a diagram showing a detail of the system illustrated in FIG. 1, more specifically a detail of the cathode compartment of an electrochemical cell of the system according to the invention.

FIG. 3 is a diagram of the storage and electrochemical energy recovery system according to a first embodiment of the invention, without circulation of the electrolyte.

FIG. 4 is a diagram of the storage and electrochemical energy recovery system according to a second embodiment of the invention, with circulation of the electrolyte.

FIG. 5 is a diagram of the storage and electrochemical energy recovery system according to a third embodiment of the invention, with circulation of the electrolyte. FIG. 6 is a schematic 3D view of an example of redox particles according to the invention.

Figure 7 is a schematic 3D view of another example of redox particles according to the invention.

In the figures, the same references designate identical or similar elements.

Description of the invention

The object of the invention is to propose a system for storing and restoring electrochemical energy "with a stream of redox particles", and a method implementing such a system, in which the electroactive material in the form of particles. solids comprises redox polymers.

The system for storing and restoring electrochemical energy, referred to as "redox particle flux", and the process implementing such a system, are the subject of the French patent application filed under No. 15 / 56,883, of which a large part of the description is repeated below.

In such a system, the flow of electro-active material circulating between the electrochemical cell and the reservoirs is primarily a stream of solid particles, said circulating stream possibly comprising the electrolyte. The electro-active matter in the form of solid particles, does not dissolve or little in the electrolyte, and the oxidation-reduction reactions occur within the particles bathed with the electrolyte in the reactive zones of the cell electrochemical.

According to the present invention, the electroactive material, in the form of solid particles, comprises at least one redox polymer.

In particular, reference will be made to a "redox polymer particle flux" battery for designating this new type of redox particle flux battery using redox polymers as an electroactive material. Terminology

Some elements of terminology are given below for a better understanding of the invention.

By anode compartment is meant the reaction zone where an electrochemical oxidation reaction (electron emission) takes place, as opposed to the compartment cathode which is the reaction zone where an electrochemical reduction reaction takes place (absorption of electrons).

Throughout the description, contraction "redox" is used to denote the chemical reactions of reduction and oxidation. A redox polymer is thus a polymer capable of experiencing reduction and oxidation reactions.

The anode compartment contains the negative or anode electrode, and the cathode compartment contains the positive electrode or cathode.

In the system according to the invention, which is an accumulator, these roles are reversed depending on whether the system discharges or charges because the redox reactions are reversible. Thus, the anode compartment where an oxidation reaction occurs which allows the emission of electrons when the system is discharging (discharges) becomes the locus of a reduction reaction if a current is applied to the system in order to recharge it.

Therefore, the terms anode and cathode compartments are defined in the present description with reference to the discharge state of the system.

By redox particles is meant solid particles comprising redox compounds. According to the invention, the redox particles of at least one compartment of the cell comprise a redox polymer. A more detailed description of these particles is given below, in particular in relation with FIGS. 6 and 7. In the present description, reference will also be made to the active substance, or electroactive material, to designate the redox polymers involved in the reactions. of oxidation-reduction at the origin of the transformation of chemical energy into electrical energy.

The present invention does not exclude the use of redox couples other than redox polymers, for example as described in the French patent application filed under No. 15 / 56,883, to form redox particles of a compartment while the other compartment comprises particles of redox polymers. Examples of such redox couples are described below.

According to the invention, the particles remain in a solid form, that the active substances they contain are in reduced or oxidized form.

According to the invention, the particles may contain an electrical percolant, also known as electronic percolator. By electrical percolant is meant a compound that allows the passage of electrons, such as carbon black.

In the battery according to the invention, the electrolyte is an ionic conductive liquid which impregnates the particles. It is not intended to solubilise the active ingredients contained in the particles. In this sense, the electrolyte contains little or no, in dissolved form, the redox polymers in their reduced or oxidized form used at the electrodes. The electrolyte however contains dissolved ions allowing the ionic conduction between the electrodes and / or secondary ions participating in the redox reactions at each of the electrodes. For example, it may be an aqueous solution comprising, for example, sulfuric acid H ₂ SO ₄ (H ₃ O ⁺ ions, SO ₄ ^2- ). The term "solvent ^" is also used in the present description for This definition of the electrolyte thus corresponds to that usually given for conventional batteries ("secondary batteries").

In the present invention, the term "electrode" means the active material in the form of a bed of solid particles bathed in the electrolyte where the redox reactions occur and in which the electrons move to the current collector. The present invention thus distinguishes the electrode and the current collector, the latter being formed of non-electro-active material (does not undergo redox reactions) and serving to collect the electrons coming from the cell or from an electrical circuit. outside and transport them to or from this outdoor circuit. Said current collector is thus defined in the same way as in conventional batteries ("primary batteries" and "secondary batteries").

Cycling of a battery means the cyclic process of charging and discharging the battery. The terms "cycler" and "cycled" are also used, referring to the cyclic charge / discharge action.

System and method according to the invention

The redox particle flow system and its method of operation are described below generally with reference to FIG.

The storage and electrochemical energy storage system 1000 comprises at least one electrochemical cell 100 comprising an enclosure 101 formed by anode compartment A and a cathode compartment C. In FIG. 1, the cell 100 is represented in a vertical section.

The two compartments, which are the zones comprising the active ingredient and where the redox reactions occur, contain an electrolyte 103, and are separated by a separator 102, an electrical insulator and permeable to the ions contained in the electrolyte.

The separator 102 is a surface disposed along a substantially vertical axis as shown in FIG. For example, the separator 102 comprises or consists of a porous polymer. The electrolyte is a liquid solution comprising ions that will participate in the redox reactions on either side of the separator in each of the compartments. By way of nonlimiting example, it may be an aqueous solution, comprising, for example, sulfuric acid H ₂ SO ₄ , potassium hydroxide KOH, or potassium sulphate, or an organic solution for example based on alkyl carbonates and a tetraethylammonium perchlorate (C ₂ H ₅ ) ₄ N ⁺ ClO ₄ ^- or lithium hexafluorophosphate LiPF ₆ salt.

The dissolved ions (cations and anions) are preferably chosen from the following ions, without being limiting:

cations: protons (H ⁺ , or in solvated form, for example H ₃ 0 ⁺ in water); alkali (Li ⁺ , Na ⁺ , K ⁺ ), tri-alkylammonium or tetraalkylammonium, substituted or unsubstituted imidazolium, tetraalkylphosphonium, alkylpyridinium, dialkylpyrolidinium;

anions: sulfate (SO ₄ ^2- ); perchlorate (CI0 ₄ ^~ ), hydroxide OH ^" chloride (CI), bromide (Br ^~ ), bis (trifluoromethane) sulfonimide (TFSI), tetrafluoroborate (BF ₄ ^~ ), hexafluorophosphate PF ₆ \

The choice of the electrolyte is made according to the type of electroactive material, e.g. the redox polymers, chosen for the 1000 system.

Preferably the electrolyte is not a solvent of the polymer. The electrolyte may alternatively be a solvent for the polymer if the redox polymer is shaped so as to be insoluble or poorly soluble in the electrolyte, as may be the case with particles in the form of grains formed by a porous support comprising a redox polymer grafted or trapped in the porosity of the support by crosslinking. These formatting is described later.

The anode compartment A comprises a negative electrode 104 in the form of a bed of a first type of sedimented redox particles 1, immersed in the electrolyte 103. The cathode compartment C comprises a positive electrode 108 in the form of a bed of a second type of sedimented redox particles 2, immersed in the electrolyte 103. The anode compartments A and cathode C are each defined by a volume between the separator 102 and a current collector dedicated to each compartment (105, 109). The current collectors 105 and 109 are, for example, metal plates or plates formed of vitreous or graphitic carbon or else of an electronically conductive composite material, for example a polymer loaded with non-electroactive conductive particles, such as graphite or nanotubes. carbon, graphene, vitreous carbon. The current collectors do not themselves undergo redox activity. Collectors can plates having a surface provided with elements in relief, for example provided with pins, in order to increase the exchange surface with the redox particles and to limit the electronic paths between the particles. Each anode compartment A and cathode C has at its top an inlet (106, 1, 10) for receiving an incoming flow of particles (10, 12), and at its base an outlet (107, 1, 1 1) for evacuating an outgoing flow. of particles (1 1, 13). Each bed of particles (104, 108) is movable in a gravity flow which is made from the inlet (106, 1 10) of the compartment to its outlet (107, 1 1 1).

In the anode compartment A, the electrode 104 is in contact with the current collector 105: the bed of particles is in contact with the collector over the entire height of the collector. It is the same in the cathode compartment C, where the positive electrode 108 is in contact with the current collector 109 in the same way.

The assembly formed by the compartments and the separator, delimited on either side of the separator by the current collectors, may also be referred to as an air gap in the field of electrochemical processes. This set, or gap, bathes entirely in the electrolyte. The redox particles 1 and 2 in the form of beds sedimented in the compartments have a porous structure, which allows that they are also impregnated with electrolyte, and are electrically conductive, so as to allow the passage of electrons between the particles in contact in the bed to the electrical collector.

The system 1000 also comprises means (not shown) for regulating the incoming flows (10, 12) and the outgoing flows (11, 13) of the redox particles, in order to produce the gravity flow giving rise to the sedimentation of the particles in each compartment.

The first type 1 and second type 2 redox particles are respectively stored outside the cell 100 in the storage tanks 1 12 and 1 13.

According to the invention, the storage and the restitution of electrochemical energy are carried out by circulating the redox particles 1 between the storage tank 1 12 and the anode compartment A, and by circulating the redox particles 2 between the tank 1 13 and the cathode compartment C of the cell 100.

The redox reactions are carried out in the anode compartments A and cathode C of the cell 100 in order to store or restore electrochemical energy. An incoming flow (10,12) and an outgoing flow (1 1, 13) are determined for each of the first and second types of particles (1, 2) so as to create a gravitational flow of the particles in each of the anode compartments A and C. This flow makes it possible to form a mobile bed of sedimented particles (104, 108) in each compartment, such that the redox reactions and the electrical conduction are ensured by percolation of the electrons and of the electrolyte 103 in the sedimented particles of the moving bed ( 104.108). In particular, the particles 1 and 2 are transported from the tanks 1 12 and 1 13 to the compartments A and C where they sediment, in the sense that they are deposited on each other and accumulate in the compartment, of in order to ensure electrical percolation up to the current collectors 105 and 109.

As illustrated in FIG. 2, which is schematically shown in section a detail of the cathode compartment C, the redox reactions causing the operation of the battery take place within the particles of the electrode in the form of a bed 108, the particles being in contact with each other, this contact being such that electrical percolation is ensured in the bed. The dotted white arrows illustrate the electrical percolation with the passage of electrons "e ^" "from one particle to another, while the black arrows in solid lines illustrate the passage of ions" / ^' "of the electrolyte within of porous particles to participate in redox reactions in the particles.

During the discharge process of the system 1000, the active material of the negative electrode 104 oxidizes by releasing electrons collected by the collector 105 and sent into the external electrical circuit (not shown in FIG. 1), as in FIG. of what happens in a conventional electrochemical accumulator. Conversely, during the discharge, the active material of the positive electrode 108 is reduced by collecting electrons from the collector 109. To allow the redox reactions within the particles of the electrodes, the particles must be electrically connected to the collector of the electrodes. current, which is ensured by the electrical conductivity of the particles and by their contact within the bed (sedimented particles). The particles must also be accessible to the ions of the electrolyte that participate in the reaction, which is ensured by the porosity of the particles. The particles are then impregnated with electrolyte. These ions thus diffuse into the electrolyte between the grains and then into the porosity of the grains, up to the place of the oxidation or reduction reaction.

The "discharged" active material formed by particles 1 and 2 which have undergone oxidation or reduction is removed from compartments A and C continuously during the discharge process, via the outlets 107 and 11 January at the base of the compartments, and the active material "charged" in the form of particles 1 and 2 in their oxidation state or initial reduction is introduced at the top of the compartments via the inputs 106 and 1 10.

During the charging process of the system 1000, a current source (not shown in FIG. 1) is applied to the system 1000 to allow the reversible redox reactions to occur in the opposite direction. The particles 1 and 2 are circulated again to allow the discharged particles to charge and the charged particles to be discharged and stored in the tanks 1 12 and 1 13.

Note that according to the invention, and unlike fuel cell operation, the amount of solid material in the form of redox particles, used in each of the tanks and its associated reaction compartment (anode or cathode), is almost constant over time . Particles do not burn; the active ingredient does not disappear over time.

Among the advantages presented by the invention is the possibility of having a battery with an improved energy density compared to known redox flux batteries employing redox couples or redox polymers in dissolved or possibly dispersed form, while by limiting the use of metals as an electroactive material that can be toxic, have a negative impact on the environment, and be expensive.

Another advantage is to overcome the use of ion exchange membranes between the anode and cathode compartments, as is the case of conventional VRB flow-type batteries because the active materials remain in solid form . Thus a simple electrical insulating separator, allowing a physical separation of the solid active material and permeable to the ions of the electrolyte, but without differentiation in the type of transferred ions, such as the separators used in conventional electrochemical accumulators, can to be used at a lower cost.

It is also noted that the present invention advantageously makes it possible, compared to slurry redox flow batteries, to use an electrolyte which is not made viscous by the presence of particles in suspension. As a result, there is little additional energy cost associated with pumping, in the case where it must be implemented. In addition the ionic conduction of the electrolyte is not affected as may be the case when the electrolyte is viscous, slowing the transport of ions. It is recalled that the so-called "slurry" systems are redox flow batteries implementing redox pairs of conventional batteries suspended in the electrolyte in circulation, such as the couples used in Li-ion batteries. The patent application US2010 / 0047671 for example describes a redox flow battery in which at least one electrode comprises a circulating electrolyte containing redox particles in suspension. This particular electrolyte is referred to as a semi-solid reagent, and may also be a colloidal suspension, an emulsion, a gel, or a micelle. A major difficulty of these slurry systems consists in producing a suspension that is electrically conductive, which is done for example by adding conductive particles such as carbon particles, without increasing the viscosity to allow the suspension to circulate. The high viscosity of this type of solution also slows down the transport of ions, which hampers the smooth running of the redox reactions and reduces the performance of the battery. These slurry systems also have other disadvantages, such as the need for large tanks to store the active ingredient in the form of a liquid-solid mixture which constitutes a large volume, a necessary homogenization of the suspension, risks of heterogeneous flows.

Another important advantage of the invention lies in the fact that the liquid phase constituted by the electrolyte is confined to the vicinity of the reaction zone, eg the anode compartments A and cathode C, and possibly to a larger zone formed by a tank in which the cell plunges, and is therefore not stored in large quantities as is the case of conventional redox flow batteries or slurry type. The limited storage of the electrolyte makes it possible to improve the safety of the batteries and to reduce the environmental risks associated with the possible leaks of potentially toxic and / or flammable liquids.

Among other advantages, it is noted that the transport of the particles can be carried out, according to certain embodiments presented below, mechanically without the use of pumps, for example using worm gear systems. which simplifies the maintenance of the system and reduces operating costs.

The system according to the invention may comprise a plurality of electrochemical cells, as in the case of storage batteries, or in the case of conventional flow batteries, connected in series to obtain high voltages and thus obtain a power adapted to the intended application. In this case, the cells can be side by side, and the anode and cathode compartments of each cell be powered by a particle distribution network. Serialization can be done directly to the bipolarity of the current collectors: the collector of the negative electrode of a compartment may be on its other face the collector of the positive electrode of the neighboring compartment. The reservoirs are preferably common to the different cells.

The dimensions of a system according to the invention can range, in the context of industrial applications, from a few dm ³ to several hundred m ³ .

The present invention is particularly well suited to stationary energy storage applications, such as the stationary storage of electrical energy from renewable energy sources, preferably photovoltaic or wind systems. The present invention can also be implemented in other applications of stationary storage of electrical energy such as the storage of excess electrical energy in thermal and nuclear power plants.

Thus, the present invention also relates to the use of the electrochemical energy storage and delivery system described, preferably comprising a plurality of electrochemical cells, for the stationary storage of electrical energy, advantageously the stationary storage of the electrical energy from renewable energy sources, preferably from photovoltaic or wind systems.

Redox polymer particles

Redox polymers

According to the invention, the redox particles of the negative and / or positive electrodes comprise a redox polymer.

It is recalled that a polymer is an organic material composed of long molecular chains called macromolecules. They are constituted by the repetition of a monomeric unit (or pattern) in a covalent sequence.

Redox polymers are polymers containing electroactive groups that can reversibly be reduced or oxidized. These redox reactions, accompanied by an electronic exchange, may take place on an organic electroactive group or on an inorganic or organometallic electroactive group. The redox reactions can be carried out on the main polymer chain, as is the case for the quinone / hydroquinone polymers, or on the side chains, as for example in the case of a polymer comprising organic side groups of the quinone or viologen type or still organometallic groups of ferrocene type or other chelated metals Redox polymers can be classified according to the organic or inorganic / organometallic nature of the electroactive group, as illustrated for example in Figures 2 and 3 of the article by R. Garcia and D. Mecerreyes entitled "Polymers with redox properties: materials for batteries, biosensors and more "(Polymer Chemistry, 2013, 4, 2206-2214).

It is known that the redox polymers may have highly variable electronic conductivity properties depending on the structure of the polymer chain, whether or not they have conjugated double bonds, the presence or absence of electroactive groups on the side chains and their state. (oxidized or reduced).

The redox polymers used in the system and method according to the invention can be electronically conductive. They may be good intrinsic electronic conductors, for example due to the presence of conjugated double bonds. They may advantageously be chosen from the following non-exhaustive list of electron-conducting redox polymers: polyaniline, polypyrrole and polythiophene. The redox polymers of the particles may have an electronic conductivity adapted to their use in a battery as described, without however being good intrinsic conductors (structure for example with little or no conjugated double bonds, and / or structure with electro-active sites spatially localized), due to a known electron transport mechanism of electro-active site in electro-active site ("hopping mode" in English), along the macromolecular chain (within the molecule of the polymer) , or between two macromolecules (between two molecules of the polymer).

Preferably, the redox polymers are associated with an electronic percolator and / or are associated with an intrinsically electronically conductive support, to form redox particles that are electrically conductive, as described below.

According to the invention, the redox polymers may have a backbone (main polymer chain) of different nature. Preferably, the compounds forming the backbone of the redox polymer are chosen from:

vinyl compounds, such as:

Polyolefins, among which polyethylene (PE), polypropylene (PP), polynorbornenes;

Aromatic polymers such as polystyrene and its derivatives;

Polyacrylates, polymethacrylates, for example polymethyl methacrylate (PMMA), polyacrylamide;

• polyvinyl acetate (PVAc) or polyvinyl alcohol (PVA)

polymers obtained by condensation or addition such as polyimides polysiloxanes;

polyurethanes, polyvinyl ethers, polyacetylene, polyalkylene glycols;

polyaniline, polypyrrole, polythiophenes. More preferably, the redox polymers used according to the invention have a backbone formed by vinyl compounds, in particular polyacrylates, polymethacrylates, polyacrylamides, and polystyrene.

Examples of compounds mentioned that can form the backbone of the redox polymer are not limiting.

The redox polymers having a backbone as described above may comprise redox groups of different nature. Thus, the redox polymers may comprise, without being limiting, the following groups:

nitroxide radicals, such as (2,2,6,6-tetramethylpiperidin-1-yl) oxy (TEMPO) and its derivatives, di-tert-butyl nitroxide and its derivatives, for example poly (2, 2 Methyl 6,6-tetramethylpiperidinyloxy-methacrylate) (PTMA) or poly (N-2, 2,6,6-tetramethylpiperidinyloxyacrylamide or poly (para N-tetrabutyl, oxyamine styrene), poly (4-vinylpyridine) ;

quinone radicals, such as antharquinones, naphthoquinones, poly (5-amino-1,4-naphthoquinone);

quinoxaline radicals;

bipyridine radicals, such as 4-4 'bipyridine and its derivatives, i.e. viologenes, for example poly (xylyviologen);

poly (2-phenyl-1,3-dithiolane);

metallomeric radicals, preferably ferrocenes such as poly (vinylferrocene), poly (ethynylferrocene) and polyferrocene;

radicals of the pyrazine, phenazine and verdazyl type and their derivatives.

The redox polymers used according to the invention preferably comprise redox groups chosen from nitroxide, quinone, quinoxaline and bipyridine radicals, eg viologenes, verdazyls and ferrocenes. Formatting redox polymers in the form of particles

The redox particles comprising the redox polymers may be manufactured according to various processes, in particular to provide solid particles, preferably substantially spherical, of a size adapted to the operation of the cell, and which are electrically conductive, of suitable porosity, and insoluble in the electrolyte.

In particular, the redox particles of the negative and / or positive electrodes have the following properties:

the particles comprise a redox polymer in solid form, which is a redox polymer not soluble in the electrolyte or shaped so as not to be soluble in the electrolyte, under the operating conditions of the electrochemical cell, that this either in its oxidized or reduced form. The active ingredient remains intact during the charging / discharging cycles, modulo a possible change in density;

the particles are in a solid form. They are thus mechanically resistant so as to reduce their erosion associated with their circulation and their storage method as and when cycles;

- The particles are porous to allow their impregnation with the electrolyte for a good course of redox reactions. The particles preferably have a macroporosity to promote the flow of electrolyte, and preferably also have a mesoporosity to maximize the exchange surface between the active ingredient and the electrolyte. The macroporosity is conventionally defined as formed by pores larger than about 50 nm, and the mesoporosity as formed by pores ranging in size from about 2 nm to 50 nm. Methods for determining the pore size distribution are described in ISO 15901-1, ISO 15901-2 and ISO 15901 -3;

the particles are electrically conductive, preferably at their outer surface and preferably also within them, to allow on the one hand the electrical contact between the grains and on the other hand to bring the electrons to the active material;

the particles have a size adapted to the operation of the cell as described. In particular, they must have large enough dimensions to allow sedimentation in the liquid phase and to allow separation from the electrolyte during their transport out of the cell, but also sufficiently small dimensions and to allow the ion transfer without affecting too much. the power of the system so that ion transport is done over distances that do not limit the power of the system. Of preferably, the particles have a size at least 10 times smaller than the width defined between the separator 102 and the current collector 105 or 109, in particular to ensure good flow of the particles. For example, the particles have a mean diameter of between 100 μηι and 5 mm, and preferably between 500 μηι and 2 mm.

- The particles are preferably substantially spherical to facilitate their circulation and percolation in compartments A and C.

At least one redox polymer is used according to the invention: at least one of the positive electrodes 108 or negative 104 comprises a redox polymer. Preferably, each of the positive and negative electrodes 108 comprises a redox polymer: the first type of redox particles 1 and the second type of redox particles 2 each comprise a redox polymer. The redox polymer of the first type of particles 1 preferably has a redox potential remote from the redox polymer of the second type of particles 2, and both preferably have a relatively high specific energy density in order to provide a high density battery. energy and power.

According to the invention, the particles can be put in two main forms detailed below, each of which can comprise several variants: (1) in the form of porous grains formed by the redox polymers, without porous support, or (2) in the form porous grains formed by a porous support containing the redox polymers.

Redox particles: porous grains formed by redox polymers, without porous support

A first main shaping consists in forming a grain with a redox polymer without porous support.

The grain formed is solid, porous, preferably substantially spherical, and has the other various properties described above.

The redox polymers are formed into porous and solid pseudospheres.

The redox polymer grains can be formed by foaming. Foaming consists of formulating a polymer with a foaming agent, also commonly called porogen, which by thermal degradation at a moderate temperature (below the degradation temperature of the redox polymer) generates gaseous compounds capable of causing foaming. Since redox polymers generally have insufficient electronic conductivity, the porosity of the grain formed by the redox polymer is at least partially filled with an adequate amount of an electronically conductive material, such as carbon black. If the polymer can be extruded, for example, the grain can be obtained by hot mixing the polymer and the electronic percolator, ie the carbon black, with a blowing agent.

In order to reinforce the electronic conductivity at the surface of the grain, it is also possible to cover the grain with a solid conductive electrical layer, porous and permeable to the ions contained in the electrolyte, thus forming a core-shell structure ("core-shell"). in English), by grain metallization or the formation of a carbon deposit on the surface of the grains, in order to substantially increase the intergrain electronic transport properties and to provide an improved response in power and energy efficiency of the storage method . The redox particles thus have a core-shell type structure as shown in FIG. 7, in which the shell 700 corresponds to the solid layer made of electrically conductive material, porous and permeable to the electrolyte and its ions, and the active substance 701 , eg the redox polymer (s) is (are) inside this shell 700.

Redox particles: porous grains formed by a porous support containing redox polymers

A second main shaping consists in forming a grain by associating a redox polymer with a porous electronically conductive support, said formed grain being then solid, porous, preferably substantially spherical, and having the other various properties described above.

Different techniques can be used for the manufacture of such redox polymer grains with porous support.

The support is preferably a sphere made of a conductive electronic material, such as a sphere of metal foam or carbon foam, said carbon foam being preferably graphitic. The use of such a conductive support has the advantage of allowing the use of many polymers, whether they are electronic conductors or not.

Any other material of electronic conductivity adapted to its use in the electrochemical system according to the invention and which can be put into the form of a porous particle may be suitable. Preferably, grafting of redox polymers onto the porous electronically conductive support is carried out.

The grafting consists in immobilizing by a strong energy bond (covalent, electrostatic, etc.) a chemical species on a support. In the present case, it is a question of grafting the polymer on the surface of a porous conductive support. The redox polymer is grafted onto the porous support so as to be present in the grain (in the pores of the grain).

Several grafting methods are possible, provided that the redox polymer has suitable functional groups. For example, and without being limiting, the following techniques, well known in chemistry, can be used:

- Diazonium salts, physisorption by ττ-π stacking with pyrene-type functional groups, "click" chemistry which consists of the cyclization between a 1,3-dipolar compound (azide, diazoalkane, nitrile oxide) and a dipolarophil (alkyne) alkene), the cycloaddition between an azide and an alkyne leading to the formation of a 1,2,3-triazole unit;

Successive deposition layer by layer of a polycation, then of a polyanion;

The redox polymers can also be associated with the porous support according to other techniques:

by crosslinking the polymer in the porosity of the support. In this case, the support can be impregnated with a solution of the polymer or monomer and with a crosslinking agent. In general, the crosslinking consists of a covalent coupling of polymers with a degree of functionality greater than 2 in order to form a covalent three-dimensional structure of infinite theoretical molecular weight. For example, it is possible to carry out the crosslinking of a vinyl polymer by copolymerization of a functionalized redox monomer with a multifunctional monomer such as divinylbenzene or else crosslinking by chemical modification of a polymer.

The crosslinking of the polymer in the porosity of the support leads to the formation in situ of a three-dimensional (3D) network of the polymer. The grain thus formed with its 3D network of the polymer in the porosity is particularly useful for physically limiting the solubilization of redox polymers in the electrolyte when said polymers are soluble in the electrolyte.

by precipitation of the polymer in the porosity of the support. In this case, the support can be impregnated with a solution of redox polymer (suitable solvent) and then dried. The polymer is then deposited in the porosity of the porous support. In the case where the grains are obtained by this precipitation technique, care should be taken to choose an electrolyte for the battery which is not a solvent for the redox polymer.

obtaining a grain from the production of an ink formed by the redox polymer in the solvent phase, and further comprising an electrical percolating agent and optionally an additional binder, and forming spherical particles from this ink by coating or by impregnating spherical particles with this ink and then drying the particles. The use of inks (redox material in the solvent phase with an electrical percolator) is a conventional method for the deposition of redox material in batteries.

Figure 6 illustrates porous grain type redox particles formed by a porous support containing redox polymers. The redox particle 2 has a spherical shaped structure 600 obtained from the conductive foam shaping 605, for example a metal or carbon foam, shown in black. The sphere 600 is filled with the active material 601, e.g. the redox polymers, shown in gray. The whole grain is porous. The porosity of the particle 2 is related to that of the conductive foam itself as well as the structure formed by the redox polymers within the initial porosity of the conductive foam. The invention does not exclude the use of solid redox couples other than redox polymers to form redox particles of one compartment of the electrochemical cell while the other compartment comprises redox polymer particles. Examples of such pairs are given in the French patent application filed under No. 15 / 56,883, and briefly recalled below.

The set of redox couples of conventional accumulators can be used provided that it can be put in the form of electrical and insoluble conductive grains having the properties mentioned above.

A list of examples of non-exhaustive redox couples is given below:

redox pairs conventionally used in lead-acid type batteries, such as the Pb / PbSO ₄ or PbO ₂ / PbSO ₄ redox pairs, preferably in combination with an aqueous electrolyte and comprising sulfuric acid H ₂ S0 ₄ ;

redox couples conventionally used in NiMH or NiCd alkaline type batteries, for example the Cd / Cd (OH) ₂ redox couple, a M / MH redox couple, M being a metal hydride, the redox pair NiOOH / Ni (OH) ₂ , preferably in combination with an aqueous electrolyte and comprising potassium hydroxide KOH;

redox pairs of lithium-ion (Li-ion) type batteries comprising lithium ion intercalation materials, such as redox couples comprising carbon, for example LiC ₆ / C ₆ , redox couples comprising titanate, lithium, for example the redox couple

redox couples comprising intermetallic alloys, for example alloys combining lithium with silicon (Si), tin (Sn), antimony (Sb) or aluminum (Al), composite redox couples consisting of a mixture of previous pairs with carbon such as Si / C, metal oxides of the family of 2D lamellar oxides of LiM0 ₂ type with M a metal such as LiCo0 ₂ (LCO), LiNiO.8Coo.15Alo.05O2 (NCA) and LiNi _x Mn _y Co _z 0 ₂ (NMC), compounds of spinel structure of the type UM ₂ O ₄ , for example LiMn ₂ 0 ₄ (LMO), materials of HV-spinel type (High Voltage Spinel) of structure LiMn ₂ - _x M _x 0 ₄ as LiMrH.5Nio _.5 C, compounds of the family of olivine type LiMP0 ₄ as LiFeP0 ₄ (LFP), alloys or mixtures of several of these named materials as LMO blend blend NMC. The electrolyte is in this case a mixture of organic solvents based on alkyl carbonates and a dissolved salt of LiPF ₆ type.

Different methods of manufacturing these particles comprising this type of non-polymeric redox couples are conceivable: a first method of manufacture consists in shaping a redox couple both good electronic conductor in the oxidized state and in the reduced state, to produce porous and solid spheres. For example, a conventional electrochemical accumulator electrode formulation comprising a high electron percolant concentration and comprising a binder for obtaining a mechanically strong particle can be used as a material to form the redox particles. A second method of manufacture is to impregnate spheres of metal foam or carbon foam by a redox couple. Electrical conductive additives may be added to the redox couples, for example carbon black type. Other binder type additives, for example a polymer, can be added to the redox couples. These types of additives are found without conventional electrochemical accumulator electrode compositions. A third method of manufacture consists in producing a sphere formed of a redox couple, well electrically percolated therein by the addition of an adequate amount of electrical percolant, for example carbon black type, and covering this sphere by an electrically conductive solid layer, porous and permeable to the ions contained in the electrolyte, such as a layer composed of carbon. The particles thus have a core-shell structure.

Other organic molecule redox couples can also be used to form redox particles of one compartment of the electrochemical cell while the other compartment comprises redox polymer particles. In this case, a grafting technique of the organic redox molecules is required to form the particles, for example an electrografting technique by oxidizing or reducing route, chemical grafting by click chemistry or from diazonium salts. These organic molecules may be quinones, quinoxalines, nitroxides, metallocenes.

In these embodiments where the electrochemical cell is in some way hybrid, with a first type of particles comprising a redox polymer in a compartment and a second type of non-polymeric redox particles (non-polymeric organic redox molecule or redox metal pair), the The electrolyte is chosen to be compatible with both types of particles for the operation of the battery (nature of the solvent, dissolved salts, pH).

Various embodiments of the system and method according to the invention

Different configurations of the system according to the invention are possible. Thus, the electrolyte can be static in the compartments of the electrochemical cell, or be mobile if the system comprises means for circulating the electrolyte. Some configurations may include mechanical transport means of redox particles, and others pneumatic conveying means thereof. Some configurations may also include two particle storage tanks, and other four tanks allowing separation of the reduced and oxidized particles exiting the compartments of the cell.

Figures 3 to 5 show examples of non-limiting embodiments.

According to a first embodiment, shown schematically in FIG. 3, the transport of the redox particles 1 and 2 to the storage tanks 312 and 313 is done by mechanical transport means, such as a worm system.

The system 3000 comprises an electrochemical cell 300 comprising an enclosure 301 formed of the anode compartments A and cathode C separated by the electrically insulating separator 302 and permeable to ions of the electrolyte 303. The system is shown to operate in the discharge direction, as it appears through the direction of flow of the electrons in the external circuit 317 connected to the current collectors 305 and 309 in contact with the negative electrodes 304 and positive 308. The circuit 317 allows the circulation of the electrons produced at the anode, thus generating a current. The circuit 317 also makes it possible to transmit a current discharged by an external generator in order to recharge the battery. In this case, the anode compartment is the place of reactions of reduction of the active material of the particles 1 of the negative electrode, and the cathode compartment the place of oxidation reactions of redox particles of second type 2.

The system comprises a tank 314 containing the electrolyte 303. The chamber 301 is immersed in this tank, so that the electrolyte 303 bathes the entire bed of particles (304, 308) in each of the anode compartments A and cathode C of the enclosure 301. The tank 314 comprises two zones 315 and 316 separated by an electrically insulating wall 319 which is chemically resistant to the electrolyte and is respectively in communication with the anode compartment A and the cathode compartment C.

The first type of particles 1 of the negative electrode 304 are injected through the top of the air gap, at the inlet 306 of the anode compartment A, via conduit-type supply means 320, preferably positioned at the bottom storage tank 312, which comprise means 321 for regulating the incoming flow of particles, for example mechanical valves. The bed of sedimented particles 304 progressively descends at the same time as the particles 1 undergo oxidation releasing electrons into the system. The oxidized particles 1 are discharged through the outlet 307, comprising regulating means 318 of the outflow, of the mechanical valve type, and are collected in the zone 315 of the tank 314, where they accumulate at the bottom of the tank. The oxidized particles 1 are transported from the bottom of the tank to the tank 312 by a device comprising a worm, allowing the particles to drip when they rise in the screw. The electrolyte thus remains in the tank 314.

In the reservoir 312, the redox particles in their reduced form are generally at the bottom of the tank, and the oxidized redox particles at the top of the tank following prolonged operation in discharge. Means for mixing the particles, such as propellers, may optionally be mounted in the tank, to ensure mixing of the particles if the sequence of charging and discharging phases requires the addition of particles available for charging. The same configuration and the same principle applies to the second type 2 particles of the positive electrode 308, which are injected into the cathode compartment C at the inlet 31, in their oxidized form, which undergo a reduction during their progress towards the bottom of the compartment. The particles 2 are collected in their reduced form in the zone 316 at the bottom of the tank 314, via the outlet 31 1 of the cathode compartment C. The reduced particles 2 are then transported to the tank 313 in the same manner as the particles of first type 1.

According to a variant of the system shown with the two reservoirs 312 and 313, the system comprises four storage tanks, two for each type of redox particles, thus making it possible to separate the oxidized and reduced redox particle circuits for each type of particles. In this case, for a given type of particle 1 or 2, each tank independently feeds by means of self-supply the associated compartment of the cell.

During the recharging of the system, the particles 1 of the negative electrode in oxidized form, or partially oxidized, are injected from the top of the gap. The particles 1 are reduced by a power supply placed on the external circuit 317 which injects electrons via the collector 305. The second type redox particles 2 of the positive electrode, sent in a reduced or partially reduced form in the compartment cathode C, undergo at the same time an oxidation and electrons are emitted and collected at the collector 309.

The system according to the invention may further comprise means for circulating the electrolyte to circulate the electrolyte out of the chamber 101, in particular to homogenize the ion concentration at the interfaces and improve the operation and the power of the system. In this case, the electrolytic solution is in motion in each of the anode compartments A and cathode C, and circulates between each of the compartments and a storage area of the electrolyte. This electrolyte storage zone may be a part of the particle storage tank, as is the case of the second embodiment, described below in connection with FIG. 4, or may be a downstream recovery zone. of the chamber, distinct from the storage tanks of the particles, as is the case of the third embodiment, described below in connection with Figure 5. According to a second embodiment, illustrated in FIG. 4, the system 4000 is substantially identical to that of the first embodiment with regard to the cell 400 and the chamber 401 immersed in a tank 414. The descriptive part in FIG. relation with references 300 to 321 is identical for the objects identified under references 400 to 421 and is not repeated here.

According to this second embodiment, the means for circulating the electrolyte comprise a system of conduits 422 and 423 provided with pumps 425 and 424. The line 422 provided with the pump 425 makes it possible to transport a mixture comprising the electrolyte 403 and the first type particles 1 from the zone 415 of the tank 414 to the tank 412. Similarly, the pipe 423 provided with the pump 424 transports a mixture comprising the electrolyte 403 and the particles first type 2 from zone 416 of tank 414 to tank 413.

In the tanks 412 and 413, separating means 427, for example a sieve adapted to the size of the redox particles used, make it possible to separate the particles of the electrolyte 403 contained in each of the liquid / solid mixtures extracted from the tank. . Preferably, the screens are positioned in the lower part of the tanks, the storage of the electrolyte occupying a minor volume compared to the storage volume of the particles. The portion of the tanks used for storing electrolyte 403 is fluidly connected to tank 414: conduit introduction means (425,426) of electrolyte 403 connect the lower part of the tanks to tank 414. L introduction of the electrolyte can be done directly in the anode compartments A and cathode C of the cell 400, or be in the areas 415 and 416 of the tank 414.

According to a third embodiment, illustrated in FIG. 5, the system 5000 is substantially identical to that of the first embodiment with regard to the cell 500. The descriptive part in relation with the references 300 to 313, 317 and 3181 is identical for the objects identified under references 500 to 513, 517 and 518 and is not repeated here.

According to this third embodiment, the electrolyte circulation means comprise a pipe system 526 which carries the electrolyte 503 discharged from the anode compartments A and cathode C together with the particles 1 and 2, and recovered in a device downstream recovery of the outlets (507.51 1). The recovery device also makes it possible to recover the redox particles and to separate them from the electrolyte in order to collect them in two separate zones 515 and 516. recovery thus comprises a container 514 provided with a bottom 524 surmounted by a sieve 525 for retaining the first type 1 and second type 2 particles respectively in the zone 515 and the zone 516, and for passing the electrolyte 503 in the bottom 524 of the container.

The pipe system 526 comprises at least one pump 527 for transporting the electrolyte 503 from the bottom 524 of the container 514 to the head of the anode compartments A and cathode C of the enclosure 501.

The transport of the first type 1 and second type 2 particles is done in the same way as for the first embodiment, using mechanical transport means such as a worm system, bringing the particles from areas 515 and 516 of the recovery device to tanks 512 and 513

Claims

1. Redox particle flow electrochemical energy storage and return system (1000,3000,4000,5000) comprising:

at least one electrochemical cell (100,300,400,500) comprising an enclosure (101, 301, 401, 501) formed by an anode compartment (A) and a cathode compartment (C) containing an electrolyte and separated by an electrical insulating separator (102, 302, 402, 502) and permeable to the ions contained in the electrolyte, said separator being disposed along a substantially vertical axis;

o said anode compartment (A) comprising a negative electrode (104,304,404,504) in the form of a bed of a first type of sedimented redox particles (1) immersed in the electrolyte (103,303,403,503), said anode compartment (A) being defined between said separator (102,302,402,502) and a first electrical current collector (105,305,405,505) in contact with said negative electrode (104,304,404,504), and said anode compartment including an inlet (103,306,406,506) at its top and an outlet (107,307,407,507) at its base for respectively receiving and discharging an incoming stream (10) and an outflow (1 1) of the first type of redox particles (1);

said cathode compartment (C) comprising a positive electrode (108, 308, 408, 508) in the form of a bed of a second type of sedated redox particles (2) immersed in the electrolyte (103, 303, 403, 503), said cathode compartment (C) being defined between said separator (102,302,402,502) and a second electrical current collector (109,309,409,509) in contact with said positive electrode (108,308,408,508), and said cathode compartment including an input (1,10,310,410,510) at its apex and an output (1,1 1, 31 1, 41 1, 51 1) at its base for respectively receiving and discharging an inflow (12) and an outflow (13) of the second type of redox particles (2);

o said beds of the first and second type of particles being movable in a gravity flow from the inlet (106,1 10,306,310,406,410,506,510) to the outlet (107,1 1 1, 307,31 1, 407,41 1, 507,51 1 ) of each of the anode (A) and cathode (C) compartments, and said first type (1) and second type (2) particles being electrically conductive;

means for regulating (318,321, 418,421, 518,521) incoming flows (10,12) and outgoing flows (1 1, 13) of the first type (1) and second type (2) redox particles; a first storage tank (1 12,312,412,512) for the first type of redox particles (1), said first tank being in communication with the anode compartment (A)

a second storage tank (1 13,313,413,513) for the second type of redox particles (2), said second tank being in communication with the cathode compartment

(VS) ;

said first type redox particles (1) and / or said second type redox particles (2) comprising a redox polymer.

The system of claim 1, wherein said redox polymer is insoluble in the electrolyte or shaped so as not to be soluble in the electrolyte.

3. System according to claim 1 or 2, wherein the redox particles of the first type (1) and / or of the second type (2) are solid and porous, preferably substantially spherical, formed by foaming said redox polymer, and having an electronic percolator, such as carbon black.

4. System according to claim 3, wherein the grains are covered with a solid layer of electrically conductive material, porous and permeable to the electrolyte and its ions.

5. System according to claim 1 or 2, wherein the first type (1) and / or second type (2) redox particles are solid and porous, preferably substantially spherical, grains formed by a porous conductive support comprising a redox polymer.

6. System according to claim 5, wherein the first type (1) and / or second type (2) redox particles are obtained by grafting a redox polymer on said porous support, or by crosslinking said redox polymer in the porous support, or by precipitation of said redox polymer in said porous support, or by coating or impregnation of the porous support with an ink comprising said redox polymer and an electronic percolator.

7. System according to any one of claims 5 and 6, wherein the porous support is a sphere made of an electronically conductive material and containing said redox polymer, preferably a sphere of metal foam or carbon foam, said foam carbon being preferably graphitic.

The system of any of the preceding claims, wherein said redox polymer has a vinyl backbone selected from the group consisting of polyacrylates, polymethacrylates, polyacrylamide and polystyrene, and includes redox moieties selected from the group consisting of nitroxide radicals, quinones, quinoxalines, bipyridines, eg viologenes, verdazyls and ferrocenes.

9. System according to any one of claims 1 to 7, wherein said polymer is electronically conductive, preferably selected from the group consisting of polyaniline, polypyrrole, polythiophene.

10. System according to any one of the preceding claims, wherein the redox particles of the first type (1) have a size at least 10 times smaller than a first width defined between the separator (102,302,402,502) and the first current collector. (105,305,405,505), and the redox particles of the second type (2) have a size at least 10 times smaller than a second width defined between the separator (102,302,402,502) and the second current collector (109,309,409,509), the redox particles of the first type (1) and the second type of redox particles (2) preferably having a mean diameter of between 100 μηι and 5 mm, and more preferably between 500 μηι and 2 mm.

1 1. A system as claimed in any one of the preceding claims wherein the first type of redox particles (1) and the second type of redox particles (2) each comprise a redox polymer.

12. System according to any one of the preceding claims, further comprising means for circulating the electrolyte for circulating the electrolyte (403,503) out of said enclosure (401, 501).

The system of claim 12, further comprising:

a tank (414) containing the electrolyte (403) and comprising a first zone (415) communicating with the outlet (407) of the anode compartment (A) to collect the outgoing flow of the first type of redox particles (1) and a second zone (416) communicating with the outlet (41 1) of the cathode compartment (C) to collect the outgoing flow of the second type of redox particles (2), said first and second zones (415, 416) being separated by a wall (419) ;

a first pipe (422) provided with a first pump (425) for transporting a first mixture comprising the electrolyte (403) and the first type redox particles (1) from the first zone (415) of the tank (414) to the first tank (412); and

a second pipe (423) provided with a second pump (424) for transporting a second mixture comprising the electrolyte (403) and the second type redox particles (2) from the second zone (416) of the tank (414) to the second tank (413);

separation means (427), such as a sieve, in each of the reservoirs (412, 413) for separating the particles of the electrolyte (403) contained in each of the first and second mixtures,

supply means (420) respectively connecting the first reservoir (412) to the anode compartment (A) and the second reservoir (413) to the cathode compartment (C) for supplying said anode compartment (A) with redox particles of the first type (1) and said cathode compartment (C) in second type redox particles (2), said supply means (420) comprising the regulating means (421) of the incoming stream of redox particles;

means for introducing (425, 426) the electrolyte (403) from the reservoirs (412, 413) into said tank (414); and wherein the electrolyte circulation means comprises the first and second lines (422,423) and the electrolyte introduction means (420).

The system of claim 12, further comprising:

a device for recovering the electrolyte (503) and redox particles, said recovery device being positioned downstream of the outlets (507, 51 1) of the anode (A) and cathode compartments (C), said recovery device comprising a container (514) having a bottom (524) surmounted by a screen (525) for retaining the redox particles of the first type (1) and of the second type (2) in two separate areas (515, 516) of the container (514) ) each receiving a type of redox particles, and to pass the electrolyte (503) into the bottom (524) of the container (514); and - a pipe system (526) provided with a pump (527) for transporting the electrolyte (503) from the bottom (524) of the container (514) to the head of the compartments (A, C) of the enclosure (501);

the electrolyte circulation means (503) comprising said conduit system (526).

The system of any of claims 1 to 1, further comprising:

a vessel (314, 414) containing the electrolyte (303, 403) and comprising a first zone (315, 415) communicating with the outlet (307, 407) of the anode compartment (A) to collect the outgoing flow of the first type of redox particles (1) and a second zone (316,416) communicating with the outlet (31 1, 41 1) of the cathode compartment (C) to collect the outgoing flow of the second type of redox particles (2), said first and second zones (315,415,316,416) being separated by a wall (319.419);

first means of transport (322, 422, 425) of the first type of redox particles (1) from said vessel (314, 414) to the first reservoir (312, 412);

second means of transport (323, 423, 424) of the second type of redox particles (2) from said vessel (314, 414) to the second reservoir (313, 413);

- supply means (320,420) respectively connecting the first reservoir (312,412) to the anode compartment (A) and the second reservoir (313,413) to the cathode compartment (C) for supplying said anode compartment (A) with particles of the first type ( 1) and said cathode compartment (C) in particles of the second type (2), said supply means (320,420) comprising the regulating means (32,421 1) of the incoming particle flow.

16. System according to any one of the preceding claims, wherein said first and / or second transport means are mechanical (322,323), and preferably comprise a screw system.

17. System according to any one of the preceding claims, wherein the first storage tank (1 12,312,412,512) and / or the second storage tank (1 13,313,413,513) comprises means for stirring the particles.

18. A method for storing and restoring electrochemical energy using a system (1000,3000,4000,5000) according to any one of the preceding claims, wherein:

the first type of electrically conductive redox particles (1) is circulated between the first storage tank (1 12,312,412,512) and the anode compartment (A) of the electrochemical cell (100,300,400,500), and the second type of redox particles is circulated; electrically conductive (2) between the second storage tank (1 13,313,413,513) and the cathode compartment (C) of said cell (100,300,400,500), said first type of particles (1) and / or said second type of particles (2) comprising a redox polymer;

redox reactions are carried out in the anode (A) and cathode (C) compartments of said cell (100,300,400,500) and the current generated by the redox reactions is collected by means of the current collectors (105,109,305,309,405,409,505,509) in order to store or restore electrochemical energy;

the incoming flow (10,12) and the outflow (1 1, 13) are determined for each of the first and second types of particles (1, 2) so as to create a gravitational flow of said particles in each of said anode compartments ( A) and cathode (C) to form the moving bed of sedimented particles (104,108,304,308,404,408,504,508) such that redox reactions and electrical conduction are provided by percolation of electrons and electrolyte (103,303,403,503) in the sedimented particles of the moving bed (104,108,304,308,404,408,504,508 ).

19. Use of an electrochemical energy storage and delivery system according to one of the preceding claims 1 to 17, preferably comprising a plurality of electrochemical cells, for the stationary storage of electrical energy, preferably storage. stationary electrical energy from renewable energy sources, preferably from photovoltaic or wind systems.