ELECTROCHEMICAL DEVICE FOR THE STORAGE OF ELECTRICAL ENERGY

Abstract

Electrochemical device for storing electrical power comprising: a reactor (1) equipped with a sidewall (2), a top wall (3), a bottom wall (5), an electrolyte inlet (7), an electrolyte outlet (8), and a plurality of electrodes Ex, where x is an integer ranging from 1 to n, said electrodes being placed in the reactor (1), the electrodes taking the form of cones and conic frustums placed in alternation and arranged so that the wider portion of each electrode is directed toward the top wall (3) or bottom wall (5) of the reactor (1), the conic frustums making contact with the sidewall (2) and the apexes of the cones defining an axis passing through the open zones of the conic frustums.

Description

Electrochemical device for storing electrical energy Technical field of the invention The invention relates to an electrochemical device for storing electrical energy and to a method for storing electrical energy. State of the art The massive storage of electrical energy presents considerable challenges. It is, in fact, essential to have storage units that can operate in a very wide range of power and capacity while favoring reduced volume aspects. A promising way to store such energies is the electrochemical way. Today, the most efficient and safest electrochemical technology is that of the electrolysis of non-ferrous metals in an aqueous medium and, more particularly, the electrolysis of metals which have a high energy content such as zinc or manganese. . In addition, the technology is simple and inexpensive: it would therefore be interesting to be able to operate such an electrolysis in a reversible manner. Application WO 201 1 / 015723 describes a process for the simultaneous cogeneration of electrical energy and hydrogen by totally electrochemical means. The method comprises a phase of electricity storage by electrolysis of a solution of an electrolyzable metal and formation of an electrolyzable metal-hydrogen battery and a phase of electricity recovery and generation of hydrogen by operation of said battery. . However, in such devices, the volumes of the reactors are very large in order to be able to supply a large quantity of electrical energy. In addition, for high power applications, the metal deposits are often inhomogeneous, which reduces the electrochemical performance of the devices, or even causes the electrodes to be short-circuited by the formation of metal dendrites. Object of the invention The object of the invention is to remedy the drawbacks of the prior art and, in particular, to propose a device making it possible to store a large quantity of electrical energy. We tend towards this object by an electrochemical device for the storage of electrical energy comprising a reactor, provided with a side wall, an upper wall, a lower wall, an electrolyte inlet, an electrolyte outlet, and a plurality of electrodes Ex with x an integer ranging from 1 to n, arranged in the reactor, the electrodes being in the form of cones and truncated cones, arranged alternately, and arranged so that the flared part of each electrode is directed towards the upper wall or the lower wall of the reactor, the truncated cones coming into contact with the side wall, the tops of the cones defining an axis passing through the open zones of the truncated cones. We are also moving towards this object by a process for storing electrical energy, comprising the following successive steps: - providing the aforementioned electrochemical device for the storage of electrical energy, - introducing an electrolyte into the electrochemical device, the electrolyte containing metal ions, - electrically connecting the first electrode to the negative terminal of a power supply and the second electrode to the positive terminal of a power supply, - providing electrical energy to reduce the metal ions on the electrodes of the electrochemical device, so as to form an electrolysable metal cell. Brief description of the drawings Other advantages and characteristics will emerge more clearly from the following description of particular embodiments of the invention given by way of non-limiting examples and shown in the appended drawings, in which: - Figure 1 shows a schematic view, and in section, a reactor of an electrochemical device, according to one embodiment of the invention, - Figure 2 schematically shows, in section, an additional electrode of an electrochemical device according to the invention. Description of a preferred embodiment of the invention The invention relates to an electrochemical device for storing electrical energy in a direct and reversible manner. As shown in Figure 1, the electrochemical device for storing electrical energy comprising: - a reactor 1, provided with: o a side wall 2, o an upper wall 3, o a lower wall 5, o an electrolyte inlet 7, o an electrolyte outlet 8, - a plurality of electrodes Ex with x an integer ranging from 1 to n, arranged in the reactor, the electrodes being in the form of cones and truncated cones, arranged alternately, and arranged so that the flared part of each electrode is directed towards the upper wall 3 or the lower wall 5 of the reactor 1, the truncated cones coming into contact with the side wall 2, the tops of the cones defining an axis passing through the open zones of the truncated cones. Reactor 1 is preferably a closed reactor in which the electrolyte circulates. The reactor 1 is, for example, a tank. The side wall 2 is preferably circular. The reactor 1 is closed, in its upper part, by an upper wall 3 also called a lid. The reactor is closed, in its lower part, by a lower wall 5 also called bottom. The lower wall 5 and the upper wall 3 are preferably of conical shape. The apex of the cone of the upper wall 3 and the apex of the cone of the lower wall 5 define an axis AA'. By conical shape, it is meant that these walls have a conical surface: their surface is defined by a straight line, or a substantially straight curve, passing through a fixed point, or vertex, and a variable point describing a closed plane curve. Preferably, the closed section has a cylindrical or ovoid shape. The cone is advantageously a cone of revolution and the side wall 2 is a cylinder, the closed section of the lower 5 and upper 3 walls forming a circle of the same size as the side wall 2. Advantageously, the upper wall 3 is configured to form a first main electrode 4. According to a first embodiment, the upper wall 3 forms the first electrode 4. According to another embodiment, the upper wall 3 serves as a mechanical support for the first electrode 4. The first electrode 4 is advantageously supported by the cover of the reactor. The device is robust and simple to implement. The first electrode 4 can be the main anode or the main cathode of the electrochemical device. In a preferred mode of operation, the first electrode 4 forms the main cathode of the electrochemical device. The first electrode 4 is then connected to a negative terminal of a DC power supply. The cover is advantageously electrically conductive. It is electrically connected with the negative terminal of the DC power supply to polarize the first electrode which is immersed in the electrolyte. The first electrode 4, intended to be in contact with the electrolyte, can be covered with a coating to promote the electrochemical reactions and its resistance to chemical and gas attacks. The first electrode 4 is advantageously made of a material which is unattackable by oxygen in an acid medium. It is, for example, covered with titanium nitride on its surface, or even in steel coated with electrically conductive ceramics. This conductive ceramic is non-oxide. Preferably, the first electrode 4 is made of stainless steel. The bottom wall 5 is configured to form a second main electrode 6. According to a particular embodiment, the lower wall 5 forms the second electrode 6. According to another embodiment, the lower wall 5 serves as a mechanical support for the second electrode 6. The second electrode is, for example, made of stainless steel covered with lead. Preferably, the second electrode is an anode. This is the main anode of the electrochemical device. The bottom of reactor 1 is electrically conductive and is brought to the potential of the positive terminal of the external power supply. The electrodes Ex are arranged between the lower wall 5 and the upper wall 3. The electrodes Ex are also called additional electrodes. Electrode E^ is the additional electrode closest to first electrode 4. It is the proximal electrode with respect to first electrode 4. The electrode En is the additional electrode farthest from the first electrode 4. It is the distal electrode with respect to the first electrode 4. FIG. 1 represents, for example, a reactor comprising four additional electrodes E ; E2, E3, and E4. The distal electrode is electrode E4. The number of Ex electrodes depends on the desired electrical power. As shown in Figure 1, the additional electrodes Ex are advantageously in the form of an entire cone or a truncated cone. The tops of the conical electrodes and the openings of the truncated cone electrodes are aligned on the axis AA'. The apices and the openings of the cones are advantageously all oriented in the same direction. Preferably, the vertices and the openings are oriented towards the upper wall 3, the flared shape of the cones or truncated cones being arranged towards the lower wall 5. In a particular embodiment, the electrodes Ex with x an odd integer are in the form of an entire cone and the electrodes Ex with x an even integer are in the form of a truncated cone. The electrodes Ex with x an odd integer are separated from the side wall 2 of the reactor 1 by a space. The electrodes Ex with x an even integer are in contact with the side wall 2 of the reactor 1 . The truncated shape of these electrodes allows the flow of fluid at the top of the cone. This embodiment is particularly effective and compact. However, an inverted configuration is also possible. According to a preferred embodiment, the electrolyte inlet 4 of the reactor is arranged, in the upper wall 3, at the level of the top of the cone forming the first electrode E-i. The electrolyte is, for example, propelled, through the lid, into the reactor, by a volumetric pump, which makes it possible to adjust the flow rate and the pressure. The electrolyte outlet 8 is arranged in the lower part of the reactor 1, between the electrode En and the lower wall 5 of the reactor. The electrolyte outlet 8 can be formed from one or more orifices, arranged at the level of the bottom of the reactor 1 . Alternatively, electrolyte inlet 7 and electrolyte outlet 8 can be reversed. A flow path of the electrolyte is thus formed (represented diagrammatically by the arrows in FIG. 1), the path going from the electrolyte inlet 7 to the electrolyte outlet 8, passing alternately between the electrodes Ex with x an odd integer and the wall of the reactor and in the openings arranged at the top of the truncated cones of the electrodes Ex with x an even integer. In this embodiment, the circulation of the electrolyte is natural and by gravity. This architecture makes it possible to obtain an excellent circulation of the electrolyte flows, its permanent renewal in line with each electrode. Such a geometry, entirely symmetrical, makes it possible to deliver a relevant circulation of electric currents from one electrode to the other and to eliminate leakage currents. However, as a variant, non-symmetrical architectures may be possible, but they are less efficient. The control of the circulation of the electric currents, associated with a reduction of turbulences, leads to a better homogeneity of the metallic deposits. Advantageously, heat losses are reduced and well distributed. The electrochemical potential of the electrodes Ex is said to be floating, that is to say that the total potential difference provided by the electric generator between the electrode 6 and the electrode 3 supported by the reactor is naturally distributed between each of the electrodes Ex. The "floating potential" is naturally balanced in the electrolyte bath circulating between the electrodes. This potential depends on the potential difference applied between the tank and the lid of the reactor, as well as on the number of Ex electrodes. Preferably, as represented in FIGS. 1 and 2, the additional electrodes Ex are bipolar. By bipolar, it is meant that the electrodes Ex can act both as anode and as cathode. A bipolar electrode has two faces: an anode face 9 and a cathode face 10. During the electroplating step, metal deposits on the cathode face and native oxygen forms on the anodic face. These particular electrodes are advantageously designed in materials adapted to these electrochemical conditions, and in particular to bipolarity. The electrodes are, for example, made of lead, tin, nickel, titanium with, advantageously, for each of said materials, electrically conductive coatings such as non-oxide ceramics. The ceramics are advantageously non-oxide. It can be silicon carbide (SiC), titanium carbide (TiC), silicon nitride (Si3N4), titanium nitride (TiN), etc. The electrodes can also be mixed bipolar electrodes made of lead oxide, combined tin and lead oxide, or else of lead alloy. Advantageously, the anode face 9 and the cathode face are made of different materials. The cathode face is, for example, made of lead, a lead alloy or coated or uncoated stainless steel. Preferably, the electrical energy is stored on mixed bipolar electrodes made of lead oxide and tin and lead oxide. The anode face preferably comprises at least one metal wire wound in a conical spiral. Preferably, the metal wire is made of lead. According to another embodiment, the anode face is covered with a second metal wire wound in a conical spiral, the second metal wire being made of tin. Even more preferentially, the anode face comprises a set of metal wires, for example a cable composed of a number k of ropes wound in one or more conical spirals. This is, for example, a conical spiral of "Pappus". This configuration leads to a strong increase in the specific exchange surface by a coefficient equivalent to pi (3.14) x k leading to the retention of native oxygen. Advantageously, there is no main gas evolution during the electrochemical reactions. The twist of metal son may have a cylindrical section, as shown in Figure 2, or a star or cruciform section. Advantageously, the section is a cylindrical section. Preferably, the wound metal twist is composed of a mixture of pure lead wires or with tin wires enclosing an oxide paste of said metals. This set of oxides and twisted wires making up the spiral can also be covered by a screen. The screen is, for example, a porous electrolyte membrane cut according to the conical shape of the electrode. A polyethylene membrane can be used. Alternatively, the cable can be replaced by a braid. The braid will be developed in such a way as to allow percolation of the electrolyte between each wire. The tightness of the braid threads can be adjusted with support wedges leaving a slight clearance between each thread. Preferably, the angle b represented in FIG. 2, defined by the axis AA' and the apothem L of the cone, is greater than 45°. Even more preferentially, the angle b is greater than 50° C. to prevent the oxides from detaching from the electrode by the effect of gravity. Advantageously, the turns of the spiral(s) are contiguous so as to cover the anode face 9 and so as to increase the quantity of active material on each electrode. If necessary, several layers of spiral wound cables from Pappus can be stacked on top of each other to further increase the heat exchange surface. Advantageously, the strands of the cables are assembled at their ends by welding with each other and with the underlayer making up their support on the anode. Preferably, the anode face 9 of the additional electrodes Ex is covered with a lead or lead alloy coating and the lead coating is covered with said spiral. The lead coating may be a sheet of lead. Tin foil can be used in place of lead foil. The surface S of each additional electrode Ex of conical shape is defined by: S = n.L.(R+r) With : L the apothem of the cone, R external radius of the cone, r internal radius of the cone, L being able to be defined by L = r / sin b, with b the angle at the top of the cone, we obtain: S = n.(r / sin b).(R+r) For R= 0.85m, r=0.05m and sinb=0.766, the electrode area is 2.97m2. This specific configuration of stacking additional electrodes of conical or frustoconical shapes, in a cylindrical volume forms, in a very small volume, a very large exchange surface. This exchange surface is further increased with the particular configuration of the anode faces of the electrodes, i.e. with the metal wires wound in a conical spiral. The bipolar electrodes allow total reversal of polarity and operation as counter-electrodes in the etching phase when the polarities are reversed and the reactor is used as an electricity generator. In the electricity production phase, a chemical attack phase is carried out on the metal deposited on the cathode faces and an electric current (battery effect) is generated. For example, for 51 bipolar additional electrodes of conical shape (truncated cone electrodes for the odd Ex additional electrodes and cone electrodes for the even Ex additional electrodes), with a surface area of ​​approximately 3m2 in a tank with a height H of 1.5m, the power P supplied is P = E.I. With E = 53 pairs x 2.85V « 150V and I = 400A / m2 x 3m2 = 1200A, the power is approximately 180kW. Advantageously, the set of additional bipolar Ex electrodes therefore forms a compact stack of electrochemical surfaces facing each other, one face of which acts as an anode and the other face as a cathode. During the operation of the electrochemical device, the electrolyte initially flows between the first electrode 4 and the anode face of the electrode E; up to the side wall 2. Then it rises along the additional electrode E2, between the cathode face of the electrode E^ and the anode face of the electrode E2. At the top of electrode E2, it passes through the opening positioned at the top of said electrode and flows between the cathode face of electrode E2 and the anode face of electrode E3 until it reaches the side wall 2, and so on to the bottom of the reactor. The association of bipolar electrodes with a stack of the conical type ensures an ideal distribution of the electric currents passing from a bipolar electrode to another electrode while ensuring a precise and controlled gravity flow of the electrolyte flows of the chemical solution containing the metal to deposit. The additional electrodes Ex advantageously have the same surface. The active reaction surface remains homogeneous from one pair to another, from the top of the reactor, towards the outside bottom, and a current iso-density is obtained. The stack of additional electrodes Ex, of identical active surface, makes it possible to obtain perfect control of the surface of the pairs of electrodes which is thus constant. This assembly of electrodes makes it possible to obtain large reaction surfaces in an extremely reduced space. The volume of reactor 1 can be considerably reduced. Such devices make it possible to store larger quantities of energy than a device with flat electrodes, for the same volume of reactor. According to a preferred embodiment, the side wall 2 of the reactor is electrically insulating, so as to prevent electrical contact between the first electrode 4 and the second electrode 6. The electrically insulating side wall 2 makes it possible to ensure the electrical insulation not only of the electrodes Ex between themselves, but also with the first 4 and second 6 electrodes. Advantageously, the side wall 2 of the reactor also acts as a mechanical support for the electrodes. The position of the electrodes can be equalized by means of wedges arranged in the side wall 2 of the reactor. The wedges are advantageously made of electrically insulating material. The electrical insulation of the electrodes Ex inside the reactor is done for example by the support of an electrically insulating ring, in relief in the external body of the reactor. This configuration is particularly used when reactor 1 comprises lead electrodes, in the case of direct storage of electricity, and without gas evolution (reactor working at atmospheric pressure). Preferably, the wedges are configured so that the cones forming the electrodes Ex, the upper wall 3 and the lower wall 5 are substantially parallel to each other. Preferably, the distance between two consecutive electrodes Ex is substantially the same at any point along any axis parallel to axis AA'. Potentials and chemical reactions are thus better distributed. Preferably, the distance between the electrodes is between 0.5 cm and 1.5 cm, which makes it possible to considerably reduce the ohmic losses. The reversible electrical energy storage process comprises the following successive steps: - provide an electrochemical device as described above, - introducing an electrolyte into the electrochemical device, the electrolyte containing metal ions, - electrically connecting the first electrode to the negative terminal of a power supply and the second electrode to the positive terminal of a power supply, - provide electrical energy to reduce the metal ions on the electrodes, so as to form a metal battery. The electrolyte contains metal ions. It may be, for example, zinc, manganese or nickel, or even cadmium. Preferably, the electrolyte is an aqueous solution based on sulphate. The sulphates are metal sulphates, advantageously chosen from lead, zinc, manganese or cadmium. The first electrochemical step, i.e. energy storage, is carried out by electrodeposition of the metal in solution on the electrodes of the electrochemical device. First, the metal ions in solution are reduced, and the metal is deposited on the cathodes of the bipolar electrodes. During the metal electrodeposition phase on the cathodes, i.e. on the wall of the reactor and on the cathodic faces of the bipolar electrodes nested one inside the other, oxygen is released at the anodes. The oxygen transforms the metallic phase of the anode face of the bipolar electrodes into oxide. Electrodeposition is performed using electrical energy. The electrical energy is stored in the form of a metal deposit. As the metal is electroplated, the metal content of the electrolyte changes, gradually decreasing. The electrolyte, also called liquor, can be permanently added if necessary with water, containing sulphates of a metal. The method comprises, after the formation of the electrolyzable metal cell, an operating phase of said cell, the operating phase comprising the dissolution of the metal, previously deposited, so as to produce electrical energy. As the metal is chemically attacked, the metal is put back into solution in the electrolyte. The dissolution of the metal produces a recombination of hydrogen into water by the simultaneous reduction of the oxides on the anode side. The reactor has become an electric generator by battery effect. Due to the large exchange surface its internal resistance is reduced. The electrical energy is recovered by connecting the first electrode 4 and the second electrode 6 to an energy recovery system. Preferably, the device comprises an electrolyte reservoir connected to the electrolyte inlet 4 and to the electrolyte outlet 8 of the reactor 1, so as to form a closed circuit. The electrolyte, used to form the electrolyzable metal cell, is reused for the operating phase of said cell. During the electrodeposition phase, the electrolyte is gradually stored in the storage tank. The reservoir then serves as a power reserve for the electrical energy production phase. After the electrodeposition phase, i.e. after the formation of the battery, the electrolyte is advantageously emptied from the reactor 1. By this emptying of the electrolyte, there is no longer any possible passage of current and the circuit is open. This operation makes it possible to obviate any electrical self-discharge of said battery during periods of non-use of the stored energy. The metal deposit produced is stable when the electrolyte is emptied from the tank and is no longer in contact with said deposited metal. The deposit is kept for a very long time without oxidizing, intrinsically conserving the electrical energy that it consumed during its electrodeposition. Advantageously, the electrolyte is always emptied when the equipment is off. This operation made very easy by the configuration of the reactor avoids the well-known problems of self-discharge of electric accumulators. The side wall comprises a drain device, advantageously arranged in the lower part of the reactor. It is also possible to use a double lateral wall, the innermost wall being fitted with valves at the base of each electrode Ex to allow more effective emptying. The electrolyte, used to form the electrolyzable metal cell, is reused for the operating phase of said cell. The electrolyte formed, in the previous operation, during battery operation will again circulate in a closed loop. The initial acid content, during this dissolution step, is high and that of metal is low. During dissolution, the metal is put back into solution. For example, in the case of lead, during the production of electrical energy, the lead sulphate solution is regenerated for a new future use. The controlled circulation of the electrolyte allows, depending on the chosen configuration, either the direct storage of electrical energy, or the direct production of electrical energy into electricity. Several reactors can be electrically coupled, in series or in parallel. Preferably, the device comprises at least a second reactor, the two reactors being mounted in series, the reactors being electrically connected. The two reactors are in fluid communication: the second reactor is arranged between the first reactor and the electrolyte reservoir, the electrolyte outlet of the first reactor being connected to the electrolyte inlet of the second reactor, and the outlet of second reactor electrolyte being connected to the electrolyte tank. The second also comprises a plurality of electrodes. The second reactor is advantageously identical to the first reactor. Advantageously, the electrical connections for the operation of the electrochemical device are very simple to put in place. The reactor is powered by a direct current generator, during the energy storage phase, and the reactor itself behaves as a controlled generator during the metal dissolution phase. The first electrode is connected to the negative terminal, while the second electrode, forming the anode, is connected to the positive terminal of the generator during the electrodeposition of the metal. During the chemical attack, the reactor acts as an electrical generator. It is then electrically connected to one or more energy recovery systems. An external direct current power supply provides the external energy necessary for the electroplating and the couplings allow the reversal of the directions of the electric currents. The very compact device has a high density of active surface in a reduced volume. The device operates, advantageously, at chosen temperatures, close to ambient temperature, has very improved heat exchange coefficients and allows the partial and direct recovery of the electrical energies induced in the chemical dissolution reactions. The method makes it possible to store electrical energy available, for example, during off-peak hours and to restore the stored electrical energy with high efficiency, for example during peak hours.

Claims

Demands 1. Electrochemical device for the storage of electrical energy comprising: - a reactor (1), equipped with: o a side wall (2), o an upper wall (3), o a lower wall (5), o an electrolyte inlet (7), o an electrolyte outlet (8), - a plurality of electrodes Ex with x an integer from 1 to n, arranged in the reactor (1 ), the electrodes being in the form of cones and truncated cones, arranged alternately, and arranged so that the flared part of each electrode is directed towards the upper wall (3) or the lower wall (5) of the reactor, the truncated cones coming into contact with the lateral wall (2) of the reactor (1 ), the apexes of the cones defining an axis passing through the open areas of the truncated cones.

2. Electrochemical device (1) according to claim 1, characterized in that the electrodes Ex are provided with an anodic face (9) and a cathodic face (10), the anodic face (9) and the cathodic face (10) being made of different materials.

3. Electrochemical device according to claim 2, characterized in that the anodic face (9) is covered with at least one metal wire wound in a conical spiral.

4. Device according to claim 3, characterized in that the turns of the spiral are joined, so as to cover the anodic face (9).

5. Device according to any one of claims 3 and 4, characterized in that the metal wire is made of lead.

6. Device according to claim 5, characterized in that the anodic face is covered with a second metal wire wound in a conical spiral, the second metal wire being made of tin.

7. Device according to any one of the preceding claims, characterized in that the electrodes Ex have the same surface area.

8. A device according to any one of the preceding claims, characterized in that the upper wall (3) and the lower wall (5) are conical in shape.

9. A device according to the preceding claim, characterized in that the cones forming the electrodes Ex, the upper wall (3) and the lower wall (5) are substantially parallel to each other.

10. Electrochemical device according to any one of claims 1 to 9, characterized in that: - the electrolyte inlet (7) is located at the upper wall (3), - the electrolyte outlet (8) is located in the lower part of the reactor, between the lower wall (5) of the reactor and the electrode En (2), - the electrodes Ex with x an odd integer are separated from the side wall (2) of the reactor (1) by a space, - the additional electrodes Ex with x an even integer are in contact with the lateral wall (2) of the reactor (1) and are provided with an opening at the apex of the cone, so as to form an electrolyte flow path, the path going from the electrolyte inlet (7) to the electrolyte outlet (8), passing alternately between the electrodes Ex with x an odd integer and the side wall (2) of the reactor (1) and through the openings arranged at the top of the cones of the electrodes Ex with x an even integer.

11. Electrochemical device (1) according to any one of the preceding claims, characterized in that the electrodes Ex are electrically insulated from each other.

12. Device according to any one of the preceding claims, characterized in that the upper wall (3) forms an electrode, preferably a cathode.

13. Device according to any one of the preceding claims, characterized in that the lower wall (5) forms an electrode, preferably an anode.

14. Electrochemical device (1) according to any one of claims 1 to 13, characterized in that the device comprises an electrolyte reservoir connected to the electrolyte inlet (7) and the electrolyte outlet (8) of the reactor (1), so as to form a closed circuit.

15. Electrochemical device (1) according to the preceding claim, characterized in that the device comprises at least one second reactor having a plurality of electrodes, the two reactors being mounted in series, the reactors being electrically connected, and in that the second reactor is disposed between the first reactor and the electrolyte reservoir, the electrolyte outlet of the first reactor being connected to the electrolyte inlet of the second reactor, and the electrolyte outlet of the second reactor being connected to the electrolyte reservoir.

16. Electrochemical device (1) according to any one of the preceding claims, characterized in that the first electrode (4) is electrically connected to the negative terminal of an electrical supply and in that the second electrode (6) is connected to the positive terminal of the electrical supply.

17. Electrochemical device (1) according to any one of the preceding claims, characterized in that the first electrode (4) and the second electrode (6) are connected to an energy recovery system.

18. A method for storing electrical energy, comprising the following successive steps: - to provide an electrochemical device according to any one of claims 1 to 17, - introduce an electrolyte into the electrochemical device, the electrolyte containing metal ions, - electrically connect the first electrode (4) to the negative terminal of a power supply and the second electrode (6) to the positive terminal of a power supply, - to provide electrical energy to reduce metal ions on the electrodes of the electrochemical device, so as to form a metal electrolyzable cell.

19. A process according to claim 18, characterized in that the process comprises, after the formation of the electrolyzable metal cell, an operating phase of said cell, the operating phase comprising the dissolution of the deposited metal so as to produce electrical energy.

20. Method according to claim 19, characterized in that, during the dissolution of the metal, the first electrode (4) and the second electrode (6) are connected to an energy recovery system.

21. A method according to any one of claims 19 and 20, characterized in that the electrolyte, used to form the metal electrolyzable cell, is reused for the operating phase of said cell.

22. A method according to any one of claims 18 to 21, characterized in that, after the formation of the metal electrolyzable cell, the electrolyte is emptied from the reactor (1).