WO2015101924A1

WO2015101924A1 - Electric and fluid interconnector for an hte electrolyser or sofc fuel cell

Info

Publication number: WO2015101924A1
Application number: PCT/IB2014/067402
Authority: WO
Inventors: Christian Perret
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2014-01-02
Filing date: 2014-12-30
Publication date: 2015-07-09
Also published as: FR3016084A1

Abstract

The invention concerns a novel design of an interconnector for an HTE reactor or an SOFC fuel cell, according to which the height of a chamber for distributing, i.e. for supplying or recovering the gases, is determined by the thickness of an intermediate metal sheet and the actual distribution is carried out by means of ports extending along an axis Y that communicate with the ports of an end metal sheet, which extend along another axis X. Those ports delimit channels that allow the gases to circulate in contact with an adjacent electrochemical cell.

Description

ELECTRICAL AND FLUIDIC INTERCONNECTOR FOR

EHT ELECTROLYSET OR SOFC FUEL CELL

Technical area

The present invention relates to the field of solid oxide fuel cells (SOFC) and that of the electrolysis of high temperature water (EHT, or EVHT for electrolysis of water vapor at high temperature, or HTE acronym for High Temperature Electrolysis, or HTSE for High Temperature Steam Electrolysis) also with solid oxides (SOEC, acronym

The present invention relates to interconnection devices that are subjected to high temperatures and on one side to a reducing atmosphere that is rich in H20 / H2 water vapor (wet hydrogen or water-rich hydrogen) in EHT electrolysis is rich in H2 in SOFC cells, and on the other side to an oxidizing atmosphere that is rich in 02 in EHT reactors, or rich in air in SOFC cells, one of the functions of which is to ensure the passage of the electrical current in EHT electrolysis reactors.

The interconnection devices, electrical and fluidic, also called interconnectors or interconnect plates, are the devices that ensure the series connection of each electrochemical cell (battery or electrolysis cell) in the stack of fuel cells and EHT reactors, thus combining the production of each one. The interconnectors thus provide power supply and collection functions and define circulation compartments (supply and / or collection) of the gases.

The present invention aims more particularly at reducing the volume required for the interconnectors while preserving the level of operation of the electrochemical cells.

It also relates to a method of making interconnectors that is inexpensive.

Prior art

A SOFC fuel cell or an electrolyser EHT consists of a stack of elementary patterns (also called SRUs for "Single Repeat Unit") each comprising a solid oxide electrochemical cell, consisting of three layers superimposed on each other anode / electrolyte / cathode, and interconnect plates of metal alloys also called bipolar plates, or interconnectors. The function of the interconnectors is to ensure both the passage of electric current and the circulation of gases in the vicinity of each cell (injected water vapor, hydrogen and oxygen extracted in an EHT electrolyser, injected air and hydrogen and water extracted in a SOFC stack) and to separate the anode and cathode compartments which are the gas circulation compartments on the anode side and the cathode side of the cells respectively.

To carry out the electrolysis of water vapor at high temperature EHT, typically between 600 and 950 ° C., water vapor H20 is injected into the cathode compartment. Under the effect of the current applied to the cell, the dissociation of water molecules in vapor form is carried out at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces hydrogen gas H2 and oxygen ions. The hydrogen is collected and discharged at the outlet of the hydrogen compartment. Oxygen ions 02 ^"migrate through I'électrolyte and recombine oxygen at the interface between I'électrolyte and the oxygen electrode (anode).

To ensure the operation of a SOFC fuel cell, air (oxygen) is injected into the cathode compartment and hydrogen into the anode compartment. Hydrogen H2 will turn into H + ions and release electrons that are captured by the anode. H + ions arrive on the cathode where they combine with 02 ^" ions made from oxygen in the air, to form water.The transfer of H + ions and electrons to the cathode will produce an electric current continuously from hydrogen.

Since the operating conditions of an electrolyser EHT are very close to those of a SOFC fuel cell, the same technological constraints are found, namely mainly the mechanical resistance to thermal cycling of a stack of different materials (ceramics and metal alloys). ), the maintenance of the seal between the anode and cathode compartments, the resistance to aging of the metal interconnectors and the minimization of the ohmic losses at various interfaces of the stack.

As regards the geometry of the interconnectors, FIGS. 1, 1A and 1B show a channel plate 1 commonly used both in the EHT electrolysers and in SOFC fuel cells. The supply or collection of current to the electrode is performed by the teeth or ribs 10 which are in direct mechanical contact with the electrode concerned. The supply of steam to the cathode or draining gas to the anode in an EHT electrolyser, the supply of air (02) to the cathode or hydrogen to the anode in a SOFC stack is symbolized by the arrows in Figure 1. The collection of hydrogen produced at the cathode or oxygen produced at the anode in an EHT electrolyser, the collection of water produced at the cathode or hydrogen surplus at the anode in an SOFC stack is made by the channels 11 which open into a fluid connection, commonly called clarinet, common to the stack of cells. The structure of these interconnectors is made to achieve a compromise between the two functions of supply and collection (gas / current).

Another interconnecting plate 1 has already been proposed: [1]. It is represented in FIG. 2 with the circulation of the fluid represented by the arrows: its structure is of the interdigitated type.

One of the major drawbacks of this channel plate or interdigitated structure are related to their production technique. Thus, these plate structures require a large material thickness, typically 5 to 10 mm, for the collection zone of the gases produced and shaping by mass machining of the gas distribution channels. A photographic representation of such a machined plate is given in FIG. 3. Material and machining costs are important and directly related to the fineness of the steps to be machined, more particularly the distances between channels less than 1 mm.

Another major disadvantage is that, as already mentioned, it is necessary to have channel depths in the plates which are relatively large, typically 5 to 10 mm, to ensure a homogeneous distribution of the gases on all the channels since their transversal supply. We can refer in particular to the publication [2]. This relatively large depth of the channels involves a relatively large interconnecting plate thickness and therefore a unitary thickness of a relatively high elementary SRU pattern. In the end, the architectures with these interconnected channel or interdigitated plates imply a relatively large height of an EHT reactor or a SOFC fuel cell, which is therefore much greater than the heights of the electrochemical cells. The use of thin sheets, typically from 0.5 to 2 mm, stamped and then assembled together by laser welding has already been tested. A photographic representation of such a plate obtained by assembling stamped sheets is given in FIG. 4. This technique has the advantage of limiting the cost of raw material but does not make it possible to achieve a channel fineness as high as by machining. In fact, the possibilities of realization for the depth of the channels, the unit width of tooth and the pitch between teeth are limited. In addition, the cost of stamping equipment requires mass production.

In addition, with these thin-sheet interconnectors according to the state of the art, it is known to have basic patterns architectures SRU, in which the distribution chambers (supply or recovery) of the gases are offset laterally with respect to the Main plan of SRUs: [3], [4]. In these architectures, the flow of gases is called "cross-flow" because the anodic circulation / distribution channels have directions perpendicular to those cathodic in a horizontal plane. In such architectures, the anodic and cathodic distribution chambers are distributed on the four sides of the stack, that is to say, offset laterally with respect to the main plane of the SRUs.

In such architectures, the lateral offset of the gas distribution chambers certainly makes it possible to have a thickness gain of the SRUs. On the other hand, this implies a larger SRU width. In other words, the architectures with these thin sheet metal plates and laterally offset distribution chambers imply a relatively large width of an EHT reactor or a SOFC fuel cell, which is therefore much greater than the widths of the electrochemical cells.

Thus, irrespective of the construction and the architecture of the interconnector plates and the gas distribution chambers, at least one of the dimensions of a basic unit SRU is much greater than that of an electrochemical cell. in an EHT reactor or a SOFC fuel cell.

There is therefore a need to improve the interconnectors for SOFC cells or EHT reactors, especially in order to reduce at least one of the dimensions of a basic unit SRU compared to that of an electrochemical cell. There is a particular need to reduce at least one of the dimensions of a basic unit SRU compared to that of an electrochemical cell, while maintaining the electrochemical performance of the latter.

An object of the invention is to respond at least in part to this (these) need (s). Another object of the invention is to provide an interconnector to achieve the previous goal and is inexpensive to achieve.

Presentation of the invention

To this end, the invention concerns, in one of its aspects, a device forming an electrical and fluidic interconnector for a high-temperature steam electrolysis reactor (EHT) or for a SOFC fuel cell. , the device consisting of five elongate flat sheets along two axes of symmetry (X, Y) orthogonal to each other with the two end plates identical to each other and with the two intermediate plates, each arranged between an end plate and the sheet metal central, identical to one another, one of the end plates being intended to come into mechanical contact with the plane of a cathode of an elementary electrochemical cell and the other of the end plates being intended to come into mechanical contact with the plane of an anode of an adjacent elementary electrochemical cell, each of the two adjacent elemental electrochemical cells, solid oxide type (SOEC), being formed of a a thode, an anode, and an electrolyte interposed between the cathode and the anode, wherein:

each of the five flat sheets is pierced, at the four corners of its central part, with four lights, said first to fourth lights of the sheets; the first and second lights being arranged on either side of the X axis and on the same side with respect to the Y axis, while the third and fourth lights are arranged on either side of the X axis and on the same side with respect to the Y axis, opposite to that in which the first and fourth lights are arranged and that the first and fourth lights are arranged on either side of the Y axis and on the same side relative to to the X axis;

the central plate has a central portion not pierced;

the two end plates each comprise a central portion pierced with a plurality of lights, said fifth end sheet lights, elongated along a length substantially corresponding to the length of the central portion along one X of the axes; the two intermediate plates each comprise two parts each pierced by an elongate light along a length corresponding substantially to the length of the central portion along the other Y axes, the two lights of each of the intermediate plates, said fifth and sixth lights of intermediate sheet, comprising plate tongues spaced apart from one another forming a comb,

the fifth light of one of the intermediate plates is in fluid communication with the first lumen of said one of the intermediate plates and the sixth lumen of said one of the intermediate plates is in fluid communication with the third lumen of said one intermediate plate, while the fifth light of the other of the intermediate plates is in fluid communication with the second light of the other of the intermediate plates and the sixth light of the other of the intermediate plates is in fluid communication with the fourth light of the other of the intermediate plates,

and wherein the five sheets are laminated and assembled together such that:

Each of the first to fourth lumens of one of the five plates is in fluid communication individually respectively with one of the corresponding first to fourth lumens of the other four laminations,

The fifth and sixth lights of each intermediate plate are in fluid communication with the fifth lights of one of the end plates

The tongues of each intermediate plate bear against both the walls separating the fifth lumens of one of the end plates and against the unperforated central portion of the central plate,

By "light" is meant here and in the context of the invention, a hole opening on either side of a metal sheet.

It is specified that the two axes of symmetry X, Y are orthogonal to each other and intersect in the center of the flat sheets.

In an interconnector according to the invention, the height of a distribution chamber, ie supply or recovery of the gases, is determined by the thickness of an intermediate sheet since the actual distribution is ensured by their elongate slots along the axis. Y and which communicate with the lights of an elongated end plate according to the other X. The latter delimit the channels which ensure the flow of gas in contact with an adjacent electrochemical cell. The central sheet delimits in a sealed manner the circulation of gases within an interconnector according to the invention between firstly that at an electrochemical cell and secondly at the level of the adjacent cell.

The tabs forming a comb of an intermediate plate transmit the electric current to the walls separating the gas circulation channels of an end plate.

Thanks to the invention, one preserves the advantages of a thin sheet interconnector architecture known without its disadvantage of relatively large width related to the lateral offset of distribution chambers, and while maintaining the performance of electrochemical cells of the same dimensions.

In other words, gas distribution chambers of low height are defined, and consequently an interconnector and therefore a basic unit SRU compact both in width and in height within an EHT reactor or a battery SOFC fuel while maintaining small electrochemical cell dimensions.

Thanks to the invention, it is possible to define a height of a gas distribution chamber defined by the thickness of an intermediate sheet, of the order of 0.5 mm, whereas in a known channel plate interconnector it is necessary to have at least 5mm of height, and with the same constituent metal.

In addition, the cost of producing an interconnector according to the invention can be low because of the small thickness of flat sheets, the use of thin metal sheet already tested the identical embodiment between intermediate sheets of a part and end plates on the other hand.

In summary, the invention which has just been described has the following advantages: - increase of the compactness of electrical and fluidic interconnector compared to that of the interconnectors according to the prior art, and for the same active electrochemical cell surface ,

- Obtaining a low material cost for the realization of an interconnector, because of the small thickness of the necessary plates, the need for only three types of flat sheets which furthermore do not have to be shaped, and finally the possibility of cutting sheets by laser or water jet, processes much more economical than the machining necessary for the realization of interconnectors according to the state of the art, obtaining a higher and more homogeneous current density than that obtained for at least some plate interconnectors according to the state of the art.

Preferably, the fifth lights of the end plates are of straight shape delimiting straight channels.

More preferably, the five sheets are joined together by welding or brazing.

Advantageously, the five sheets are ferritic steel with about 20% chromium, preferably CROFER® 22APU or FT18TNb, nickel-based Inconel® 600 or Haynes®.

According to an advantageous variant, each of the five sheets has a thickness of between 0.1 and 1 mm.

According to this variant, the central sheet may have a thickness of between 0.1 and 0.5 mm, each end sheet may have a thickness of between 0.1 and 0.5 mm, and each intermediate sheet may have a thickness of between 0.5. and 1 mm.

Preferably, the unit width of a channel defined by a fifth light of an end plate is between 0.15 and 5 mm.

More preferably, the unit width of a channel defined between two consecutive tongues of an intermediate sheet is between 5 and 10 mm.

The subject of the invention is also an electrolysis reactor comprising a stack of elementary electrolysis cells of the SOEC type each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, and a plurality of electrical and fluidic interconnectors as described above, each arranged between two adjacent elementary cells with one of the end plates in electrical contact with the cathode of one of the two elementary cells and the other of the end in electrical contact with the anode of the other of the two elementary cells.

The invention further relates to a method of operating an electrolysis reactor described above, according to which:

the first lights are supplied with water vapor and the fourth lights simultaneously with a draining gas, such as air, the hydrogen produced by the electrolysis of the steam is recovered in the third lumens and simultaneously the oxygen produced by the electrolysis of the water vapor in the second lumens.

The subject of the invention is also an SOFC fuel cell comprising a stack of elementary electrochemical cells of the SOEC type each formed of a cathode, an anode and an electrolyte interposed between the cathode and the anode, and a plurality of electrical and fluidic interconnectors as described above, each arranged between two adjacent elementary cells with one of the end plates in electrical contact with the cathode of one of the two elementary cells and the other of the end plates in electrical contact with the anode of the other of the two elementary cells.

Finally, the subject of the invention is a method of operating a SOFC fuel cell as above, according to which:

the first lights are supplied with air and simultaneously the fourth lights with hydrogen H2,

the hydrogen produced is recovered, in the third and simultaneously the hydrogen that is not used in the second lumens.

detailed description

Other advantages and characteristics of the invention will emerge more clearly from a reading of the detailed description of exemplary embodiments of the invention, given for illustrative and nonlimiting purposes, with reference to the following figures among which:

FIG. 1 is a diagrammatic front view of an interconnecting plate of an electrolyser EHT according to the state of the art,

FIG. 1A is a detailed sectional view of an interconnecting plate according to FIG. 1,

FIG. 1B is a view similar to FIG. 1A showing the current lines running through the plate,

FIG. 2 is a diagrammatic front view of another interconnecting plate of an electrolyser according to the state of the art,

FIG. 3 is a photographic reproduction of a plate according to FIG. 1, obtained by mechanical machining, FIG. 4 is a photographic reproduction of a plate according to FIG. 1, obtained by stamping,

FIG. 5 is a schematic exploded view of part of a high temperature electrolyser comprising interconnectors according to the state of the art,

FIG. 6 is a schematic exploded view of part of a SOFC fuel cell comprising interconnectors according to the state of the art,

FIG. 7 is an exploded view of an interconnector according to the invention showing the five plane plates that constitute it, as well as two electrolysis cells on either side,

FIGS. 8A to 8E are respective front views of each of the five laminated and assembled flat sheets constituting an interconnector according to the invention, FIGS. 9A and 9B show the level of transfer current and the distribution thereof. in an electrolyte of an electrolytic cell of an EHT reactor respectively in an interconnecting stack architecture according to the invention and in a state-of-the-art channel plate stack architecture.

Figures 1 to 4 relating to the state of the art have already been commented on in the preamble. They are therefore not detailed below.

For the sake of clarity, the same elements of an EHT electrolysis reactor according to the state of the art and of an EHT electrolysis reactor according to the invention are designated by the same reference numerals.

It is specified here throughout the present application, the terms "lower", "upper", "inner", "outside", "" internal "" external "are to be understood by reference to an interconnector according to the invention in cross-sectional view along one of the X or Y axes of symmetry.

It is also specified that here and throughout the present application, the terms "height" and "thickness" are to be understood as being synonymous.

It is specified that the conditions in which the simulations with a channel plate interconnector and an interconnector according to the invention were made and for which the results are shown respectively in FIGS. 9A and 9B, were as follows:

- cathode electrolysis cell support at a temperature of 800 ° C;

- H ₂ 0 / H ₂ ratio at the cell cathode input: 90/10; flow rate of H ₂ 0 / H ₂ at the cell cathode inlet: 1200 mL.min ^-1 ;

air flow at the cell anode inlet: 1200 mL.min ^-1 ;

- steady state of fluids at the anode and cathode;

- Interconnector walls under adiabatic conditions;

operation of the electrolysis cell at the so-called thermoneutral voltage of 1.298 V.

It is also specified that, in all of FIGS. 1 to 7, the symbols and the arrows supplying water vapor H20 and air as draining gas, distribution and recovery of hydrogen dihydrogen and oxygen. 02, and current are shown for the sake of clarity and precision, to illustrate the operation of a state of the art EUT water vapor electrolysis reactor and an EUT electrolysis reactor according to the invention.

It is also specified that all the electrolysers described are of the solid oxide type (SOEC), which is a high-temperature solid oxide electrolyte cell. Thus, all the constituents (anode / electrolyte / cathode) of an electrolysis cell are ceramics. The high operating temperature of an electrolyser (electrolysis reactor) is typically between 600 ° C and 1000 ° C.

It should be noted that in the illustrated embodiment of an electrolyser interconnector EHT according to FIGS. 7 to 8E, the dimensions indicated are given as an indication with reference to an electrolysis cell whose electrochemically active surface is a square of 100 mm. X 100mm. It goes without saying that other dimensions of flat sheets and lights of an interconnector according to the invention may be suitable for the realization according to the dimensions of electrolysis cells.

Typically, the characteristics of a SOEC elemental electrolysis cell suitable for the invention, of the cathode support (CSC) type, may be those indicated as follows in the table below. BOARD

Electrolysis cell Unit Value

Cathode 2

Constituent material Cermet Nickel Zirconia

Thickness μηι 500

Thermal conductivity W m ^"1 K ^{" 1} 13, 1

Electrical conductivity Ω ^"1 m ^{" 1} 10 ³

Porosity 0.3

Permeability m ² 6.10 ^"12

Tortuosity 4

Current density A. m ^"2 5300

Anode 4

Constitutive material LSCF

Thickness μηι 35

Thermal conductivity W m ^"1 K ^{" 1} 9.6

Electrical conductivity Ω ^"1 m ^{" 1} 1 10 ⁴

Porosity 0.2

Permeability m ² 9.10 ^"12

Tortuosity 4

Current density A. m ^"2 2000

Electrolvte 3

YSZ constituent material

Thickness μπι 10

Resistivity Ω m 0.42

A water electrolyzer is an electrochemical device for producing hydrogen (and oxygen) under the effect of an electric current.

In electrolysers with high temperature EHT, the electrolysis of water at high temperature is carried out from steam. The function of a high temperature electrolyser EHT is to transform the water vapor into hydrogen and oxygen according to the following reaction:

2H20 → 2H2 + 02.

This reaction is carried out electrochemically in the electrolyser cells. As shown diagrammatically in FIG. 5, each elementary electrolysis cell C1, C2 is formed of a cathode 2.1, 2.2 and an anode 4.1, 4.2 placed on either side of a solid electrolyte 6.1, 6.2 generally under membrane shape. The two electrodes (cathode and anode) 2.1, 2.2 and 4.1, 4.2 are electronic conductors, of porous material, and the electrolyte 6.1, 6.2 is gastight, electronic insulator and ionic conductor. The electrolyte may in particular be an anionic conductor, more specifically an anionic conductor of O ^{2 -} ions and electrolyser is then called anionic electrolyzer.

The electrochemical reactions are at the interface between each of the electronic conductors and the ionic conductor.

At the cathode 2.1, 2.2, the half-reaction is the following one:

2 H20 + 4 e ^" → 2 H2 + 2 0 ^2" .

At the anode 4.1, 4.2, the half-reaction is as follows:

20 ^{2 "} → 02+ 4 th ^" .

The electrolyte 6.1, 6.2 interposed between the two electrodes 2.1, 2.2; 4.1, 4.2 is the place of migration of ions O ^{2 "} 'under the effect of the electric field created by the potential difference imposed between the anode and the cathode.

As illustrated in parentheses in FIG. 5, the water vapor at the cathode inlet may be accompanied by hydrogen H 2 and the hydrogen produced and recovered at the outlet may be accompanied by steam. Similarly, as shown in dashed lines, a draining gas, such as air can also be injected at the inlet to evacuate the oxygen produced. The injection of a draining gas has the additional function of acting as a thermal regulator.

An elementary electrolysis reactor consists of an elementary cell C1 as described above, with a cathode 2.1, an electrolyte 3.1, and an anode 4.1 and two mono-polar connectors which provide the functions of electrical distribution, hydraulic and thermal.

To increase the flow rates of hydrogen and oxygen produced, it is known to stack several elementary electrolysis cells on each other by separating them by interconnection devices, usually called interconnectors or bipolar interconnection plates. The assembly is positioned between two end interconnection plates that support the power supplies and electrolyser gas supplies (electrolysis reactor).

A high temperature water electrolyser (EHT) thus comprises at least one, generally a plurality of electrolysis cells stacked on top of one another, each elementary cell being formed of an electrolyte, a cathode and a cathode. an anode, the electrolyte being interposed between the anode and the cathode.

The fluidic and electrical interconnection devices which are in electrical contact with one or more electrodes generally provide the feed and collecting electric current and delimiting one or more gas circulation compartments.

Thus, a so-called cathodic compartment has the function of distributing electric current and water vapor as well as recovering hydrogen from the cathode in contact.

A so-called anode compartment has the function of distributing the electric current as well as recovering the oxygen produced at the anode in contact, possibly using a draining gas.

Satisfactory operation of an EHT electrolyser requires:

good electrical insulation between two adjacent interconnectors in the stack, otherwise the elementary electrolysis cell interposed between the two interconnectors will be short-circuited,

a good electrical contact and a sufficient contact area between each cell and interconnector, in order to obtain the lowest ohmic resistance between cell and interconnector,

a good seal between the two separate compartments, i.e. and cathode, under penalty of recombination of the gases produced causing a drop in yield and especially the appearance of hot spots damaging electrolyser,

a good distribution of gases both in input and recovery of the gases produced, on pain of loss of efficiency, inhomogeneity of pressure and temperature within the various elementary cells or even crippling cell degradations.

FIG. 5 represents an exploded view of elementary patterns of a high temperature steam electrolyser according to the state of the art. This electrolyser EHT comprises a plurality of elementary electrolysis cells C1, C2. of solid oxide type (SOEC) stacked alternately with interconnectors 8. Each cell C l, C2 ... consists of a cathode 2.1, 2.2, ... and an anode 4.1, 4.2, between which is disposed an electrolyte 3.1, 3.2. . . .

In an EHT electrolyser, an interconnector 8 is a metal alloy component which separates the anode compartments 7 and cathode 9, defined by the volumes between the interconnector 8 and the adjacent anode 4.2 and between the interconnector 8 and the cathode adjacent 2.1 respectively. It also ensures distribution of gases to the cells. The injection of water vapor into each elementary pattern is done in the cathode compartment 9. The collection of the hydrogen produced and the residual water vapor at the cathode 2.1, 2.2 .. is carried out in the cathode compartment 9 downstream of the cell C1, C2 .. after dissociation of the water vapor therefrom. The collection of the oxygen produced at the anode 4.2 is carried out in the anode compartment 7 downstream of the cell C 1, C 2 after dissociation of the water vapor therefrom.

The intercormector 8 ensures the flow of current between the cells C1 and C2 by direct contact with the adjacent electrodes, that is to say between the anode 4.2 and the cathode 2.1 (Figure 5).

FIG. 6 represents the same elementary patterns as those of FIG. 5, but for a SOFC fuel cell with elementary cell cells C1, C2 and the interconnectors 8. The symbols and the arrows of the air, dihydrogen and oxygen, current are shown in this figure 6 for the sake of clarity.

The injection of the oxygen-containing air into each elementary pattern is done in the cathode compartment 9. The collection of the water produced at the cathode 2.1, 2.2 .. is carried out in the cathode compartment 9 downstream of the cell C1, C2 .. after recombination of the water therewith with H2 hydrogen injected at the anode 4.2 is carried out in the anode compartment 7 upstream of the cell C1, C2. The current produced during the recombination of the water is collected by the interconnectors 8.

According to the state of the art, these interconnectors 8 are usually made by mechanical machining of thick plates or by the use of thin sheets, typically from 0.5 to 2 mm, stamped and then assembled together by laser welding. Material and machining costs are important. The production technique has the advantage of limiting the cost of raw material but does not achieve a channel fineness as high as by machining. In fact, the possibilities of realization for the depth of the channels, the unit width of tooth and the pitch between teeth are limited. In addition, the cost of stamping equipment requires mass production. In addition, the electrical contact between the electrodes and the interconnector is not completely satisfactory, in particular because of the lack of flatness of the electrodes. Finally, the dimensions of an interconnector 8 according to the state of the art, and therefore of an elementary pattern SRU remain relatively important, particularly with regard to those of the electrochemical cells C1, C2 ....

Also, to reduce the dimensions of a basic unit SRU in a SOFC fuel cell or electrolyzer EHT while preserving the performance of electrochemical cells, the inventors proposes a new type of interconnector 8, an example of which is shown in FIG.

FIG. 7 thus explodes an interconnector 8 according to the invention making it possible to ensure the supply of water vapor H 2 O and of air as draining gas, as well as the recovery respectively of oxygen O 2 with the draining gas. and H2 hydrogen with water vapor, produced within the stack of an electrolysis reactor. As detailed below, the interconnector 8 makes it possible to ensure a circulation of the H 2 O / H 2 gas to the cathodes of the cells in countercurrent with the circulation of the recovered gas O 2 with its draining gas to the anodes of the cells.

The interconnector 8 consists of five flat plates 80, 81, 82, 83, 84 elongate along two axes of symmetry (X, Y) orthogonal to each other, the five sheets being laminated and assembled together by welding.

All five flat sheets 80, 81, 82, 83, 84 may be made of the same metal, for example a commercial ferritic alloy of the CROFER 22 APU type.

The two end plates 81 and 82 are identical to each other. By way of example, each end plate 81, 82 has a thickness of 0.15 mm.

The two intermediate plates 83 and 84, each arranged between an end plate 81 or 82 and the central plate 80, are identical to each other. By way of example, each end plate 83, 84 has a thickness of 0.5 mm.

One of the end plates is intended to come into mechanical contact with the plane of a cathode 2.1 of an elementary electrolysis cell (C1) and the other of the plates

82 end is intended to come into mechanical contact with the plane of an anode 4.2 of an adjacent elementary electrolysis cell (C2). Each of the two adjacent elementary electrolysis cells (C1, C2) of the SOEC type is formed of a cathode 2.1, 2.2, an anode 4.1, 4.2 and an electrolyte 3.1, 3.2 interposed between the cathode and the anode. . Each of the five 80, 81, 82, 83, 84 flat plates is pierced, at the four corners of its central part, four lights 801 to 804; 811 to 814; 821 to 824; 831-834; 841 to 844 say first to fourth plate lights. Preferably, as illustrated in the embodiment of Figures 7 to 8 E, the flat sheets 80, 81, 82, 83, 84 have an identical surface, with a square or rectangular section.

The first lights 801, 811, 821, 831, 841 are dedicated to feeding the cathodes of cells with water vapor.

The second lights 802, 812, 822, 832, 842 are dedicated to the recovery and evacuation of air as draining gas and oxygen produced at the anodes of the cells.

The third lights 803, 813, 823, 833, 843 are dedicated to the recovery and evacuation of the hydrogen produced at the cathodes of the cells.

The fourth lights 804, 814, 824, 834, 844 are dedicated to feeding the anodes of the cells in air as a draining gas.

The first 801, 811, 821, 831, 841 and second 802, 812, 822, 832, 842 lights are arranged on either side of the X axis and on the same side with respect to the Y axis.

The third 803, 813, 823, 833, 843 and fourth 804, 814, 824, 834, 844 lights are arranged on either side of the X axis and on the same side with respect to the Y axis, opposite to the the one in which the first and fourth lights are arranged.

Finally the first 801, 811, 821, 831, 841 and fourth 804, 814, 824, 834, 844 lights are arranged on either side of the Y axis and on the same side with respect to the X axis. Preferably, as shown in FIGS. 7 to 8E, the first to fourth lights of the same flat sheet form a square. Also preferably, as shown in FIGS. 7 to 8E, the first to fourth lights are of circular section.

The central plate 80 has a central portion 800 not pierced.

The two end plates 81, 82 each comprise a central portion pierced with a plurality of lights 815, 825, called fifth end sheet lights, elongated along a length corresponding substantially to the length of the central portion according to the invention. an X of the axes.

Advantageously, as illustrated in FIGS. 8A and 8E, the fifth 815, 825 lights of the end plates 81, 82 are of straight form delimiting channels rectilinear parallel to each other. These channels form the steam supply channels to cathodes 2.1, 2.2 of the cells. The channel area delimited by the fifth lumens 815 or 825 substantially corresponds to the entire electrochemically active surface of a cathode 2.1, 2.2 in order to supply it completely with water vapor. The walls of rectangular section each separating two fifth consecutive lights 815, 825 provide electrical contact with the electrolysis cell Cl, C2. To ensure satisfactory operation with a CSC cell, as described in the table above, a width of the order of 1 mm at a time for the channels delimited by the fifth lights 815, 825 and for the walls separating is adapted.

The two intermediate plates 83, 84 each comprise two parts each pierced with a light 835, 836; 845, 846 elongated along a length corresponding substantially to the length of the central portion along the other Y axes.

Lights 835, 836; 845, 846 each cover the entire width, i.e. dimension along the Y axis, of the channels delimited by the fifth lights 815, 825 of the end plates 81, 82.

The two lights 835, 836; 845, 846 of each of the intermediate plates 83, 84, said fifth and sixth intermediate sheet lights, comprise tabs 83L, 84L of sheets spaced apart from each other forming a comb (8B and 8D). In place of a comb such as that shown in Figures 8B and 8D, there may be provided a horizontal grid interwoven mesh. Such a grid has the same thickness as it replaces and thus allows the passage of current in the vertical and horizontal direction. It is also permeable in the horizontal and vertical directions for the passage of fluid.

These tongues 83L, 84L have the function of transmitting the electrical current to the walls separating the channels end plates 81, 82, against which they are supported. To ensure satisfactory operation, a width of fifth lights 835, 845 and sixth lights 836, 846, of the order of 23 mm is adapted, that is to say a number of three tongues of 1 mm between channels 5 mm wide.

The fifth light 835 of one of the intermediate plates 83 is in fluid communication with the first light 831 of the same intermediate sheet 83 (FIG. 8D). In other words, this fifth light 835 which constitutes the chamber supplying water vapor H20 from the cathode 2.1 of the cell C1, includes the light 831 through which water vapor arrives.

The sixth light 836 of the intermediate plate 83 is in fluid communication with the third light 833 of the same intermediate plate 83 (FIG. 8D). In other words, this sixth light 836 which constitutes the H2 hydrogen recovery chamber produced at the cathode 2.1 of the cell C1, includes the light 833 through which the hydrogen produced is collected and extracted from the EHT stack.

The fifth 845 light of the other 84 of the intermediate plates is in fluid communication with the second 842 light of the same intermediate sheet 84 (Figure 8B). In other words, this fifth light 845 which constitutes the oxygen recovery chamber 02 produced at the anode 4.2 of the cell C2, includes the light 842 through which the oxygen produced is collected with the air as a draining gas. and extracted from the EHT stack.

The sixth light 846 of the intermediate plate 84 is in fluid communication with the fourth light 844 of the same intermediate plate 84 (FIG. 8B). In other words, this sixth light 846 which constitutes the air supply chamber as a draining gas at the anode 4.2 of the cell C2, includes the light 844 through which the air arrives.

The lamination and the assembly by welding of the five sheets 80, 81, 82, 83, 84 between them are such that:

Each of the first to fourth lumens 801 to 804, 811 to 814, 821 to 824, 831 to 834 of one of the five laminations is in fluid communication individually with one of the first to fourth lumens 801 to 804, 811 respectively. Corresponding 814, 821 to 824, 831 to 834 of the other four sheets,

The fifth 835, 845 and sixth 836, 846 lights of each intermediate plate 83, 84 are in fluid communication with the fifth 815 or 825 lights of one of the end plates 81 or 82,

The tongues 83L, 84L of each intermediate plate 83, 84 bear against both the walls separating the fifth lumens 815, 825 from one of the end plates 81, 82 and against the central portion 800 which is not pierced by the central plate 80.

In a stack electrolysis reactor of elementary electrolysis cells SOEC type according to the invention, a stack of a plurality interconnectors 8 each arranged between two adjacent elementary cells C1, C2 is made with the first end plate 81 in electrical contact with the cathode 2.1 of one Cl of the two elementary cells and the second end plate 82 in contact with electric with the anode 4.2 of the other C2 of the two elementary cells. The set of electrolysis cells is fed in series by the electric current and in parallel by the gases.

With reference to FIG. 7, the method of operating an electrolysis reactor according to the invention as just described will now be described:

the first 811, 831, 801, 841, 821, water vapor lights and at the same time the fourth 814, 834, 804, 844, 824 lights are fed into a draining gas, such as air,

the hydrogen produced by the electrolysis of the steam is recovered in the third 813, 833, 803, 843, 823 lumens and simultaneously the oxygen produced by the electrolysis of the water vapor in the second 812 , 832, 802, 842, 822 lights.

The paths respectively of the injected water vapor and of the hydrogen produced and of the air as the injected draining gas and the oxygen produced at the inlet and the outlet of an interconnector 8 are diagrammatically dashed in the figure. 7.

An interconnector according to the invention 8 is more compact than an interconnector according to the state of the art. Typically, with the dimensions given by way of example, the total thickness of interconnector 8 is 1.4 mm. For the same dimensions and cell performance, an interconnector 8 according to the invention, as described with reference to FIGS. 7 to 8 E, requires a height of a water vapor distribution chamber defined by the thickness of the sheet. end of 81, of the order of 0.5 mm while for an interconnector 8 to channel plates according to the state of the art, as described with reference to Figure 5, the required height is from order of 5mm.

In addition, the advantages in terms of manufacturing and related cost provided by the invention are numerous:

a small thickness of each of the five flat sheets makes it possible to envisage a low material cost,

only three types of flat sheets are to be manufactured: central plate 80, intermediate plates 83, 84 and end plates 81, 82, - The sheets are flat and therefore do not have to be shaped by stamping, machining ...,

- the sheets can be cut by laser or water jet, processes much more economical than machining,

- The assembly of the five sheets of an interconnector between them can be achieved by laser welding. Several of these sheets, see all can be welded together by transparency given the low thicknesses.

In order to demonstrate the operating advantages of an interconnector 8 according to the invention compared to a state-of-the-art channel plate interconnector, the commercial software FLUENT used a simulation to measure the level of transfer current and its homogeneity in the electrolyte of an electrolysis cell.

The simulation conditions are recalled above. It is furthermore specified that the dimensions of the water vapor distribution channels, namely their height and the width of the walls separating them, are the same for the interconnector according to the invention and for a channel plate interconnector according to the state. art.

An electrical contact resistance equal to 5 * 10 ^-6 Qm ² is applied between an interconnector and the electrolysis cell.

The results are shown in FIG. 9A for a channel plate interconnector according to the state of the art and, in FIG. 9B for an interconnector 8 according to the invention.

It emerges from this simulation that under a thermally neutral voltage (1.298V), a current equal to 88.6A is obtained with an interconnector 8 according to the invention while it is equal to 82.3 A with an interconnector 8 according to the invention. 'state of the art. The gain on the value of the transfer current with interconnector according to the invention 8 is therefore equal to more than 7%.

In addition, as is apparent from Figures 9A and 9B, the current is much more homogeneous with an interconnector 8 according to the invention. Indeed, it varies between a value of 0.577 A / cm ² and a value of 1.1 A / cm ² with an interconnector 8 according to the invention while it varies between 0.087 A / cm ² and 1.17 A / cm ² with an interconnector 8 according to the state of the art. The interconnector 8 according to the invention which has just been described can be used in a SOFC fuel cell. The operating method of such a SOFC fuel cell is carried out as follows:

the first 811, 831, 801, 841, 821 lights are supplied with air and at the same time the fourth 814, 834, 804, 844, 824 H2 hydrogen lights,

the hydrogen produced is recovered in the third 813, 833, 803, 843, 823 lumens and simultaneously the hydrogen not used in the second 812, 832, 802, 842, 822 lumens.

The invention is not limited to the examples which have just been described; it is possible in particular to combine with one another characteristics of the illustrated examples within non-illustrated variants.

References cited

[1] Liang Li, International Journal of Hydrogen Energy (2005) pp 359-371.

[2] .M. Petitjean, M. Reytier, A. Chatroux, L. Bruguiere, Mansuy A., Sassoulas S, Di Morio S., Morel B, Mougin J., "Performance and Durability of High Temperature Steam Electrolysis: From Single Cell to Short -Stack Scale ", ECS Transactions, 35 (1) (2011) pp 2905-2913.

[3]. Sune Dalgaard Ebbesen, Jens Etogh, Karsten Agersted Nielsen, Jens Ulrik Nielsen, Mogens Mogensen, "Sustainable SOC stacks for hydrogen production and synthesis gas by high temperature electrolysis", International newspaper of hydrogen energy 36 (2011) pp 7363-7373.

[4] .K. Foger, J. G. Love, "Review Fifteen Years of SOFC Development in Australia", Solid State Ionics 174 (2004) pp 119-126.

Claims

Apparatus (8) forming an electrical and fluidic interconnector for a high temperature steam electrolysis (EHT) reactor or for a SOFC fuel cell, the device consisting of five planar plates (80, 81, 82, 83, 84, 85) elongated along two axes of symmetry (X, Y) orthogonal to each other, with the two end plates (81, 82) identical to each other and to the two intermediate plates (83, 84), each arranged between an end plate and the central plate, identical to one another, one (81) of the end plates being intended to come into mechanical contact with the plane of a cathode (2.1) of a cell ( C1) electrochemical element and the other (82) of the end plates being intended to come into mechanical contact with the plane of an anode (4.2) of an adjacent elementary electrochemical cell (C2), each of the two elementary electrochemical cells adjacent, of the solid oxide type (SOEC), being formed of a cathode (2), an anode (4), and an electrolyte (3) interposed between the cathode and the anode, wherein:

- Each of the five flat sheets (80, 81, 82, 83, 84, 85) is pierced at the four corners of its central portion, four lights, said first to fourth lights sheets (801 to 804, 811 to 814; 821-824; 831-834; 841-844); the first (801, 811, 821, 831, 841) and second (802, 812, 822, 832, 842) lights being disposed on either side of the X axis and on the same side with respect to the axis Y, while the third (803, 813, 823, 833, 843) and fourth (804, 814, 824, 834, 844) lights are arranged on either side of the X axis and on the same side relative to to the Y axis, opposite to that in which are arranged the first and fourth lights and the first and fourth lights are arranged on either side of the Y axis and the same side relative to the X axis;

- The central plate (80) has a central portion (800) not pierced;

the two end plates (81, 82) each comprise a central portion pierced with a plurality of lights, said fifth lights (815, 825) of end plate, elongated over a length substantially corresponding to the length of the portion central according to the X axis;

the two intermediate plates (83, 84) each comprise two parts each pierced by an elongated light along a length substantially corresponding to the length of the central portion along the other axis Y, the two lights of each of intermediate plates, said fifth (835, 845) and sixth (836, 846) intermediate sheet lights, comprising plate tongues (83L, 84L) spaced apart from each other forming a comb,

the fifth lumen (835) of one of the intermediate plates (83) is in fluid communication with the first (831) lumen of said one (81) of the intermediate plates and the sixth lumen (836) of said one (83) of the intermediate plates is in fluid communication with the third (833) lumen of said one (83) intermediate plates, while the fifth (845) lumen of the other (84) of the intermediate plates is in fluid communication with the second (842) light from said other (84) of the intermediate plates and the sixth light (846) of said other of the intermediate plates is in fluid communication with the fourth (844) light of said other of the intermediate plates,

and wherein the five sheets (80, 81, 82, 83, 84) are laminated and joined together such that:

Each of the first to fourth lumens (801 to 804, 811 to 814, 821 to 824, 831 to 834) of one of the five laminations is individually in fluid communication with one of the first to fourth lumens (801 to 804, respectively). , 811 to 814, 821 to 824, 831 to 834) of the other four sheets,

The fifth (835, 845) and sixth (836, 846) lumens of each intermediate plate (83, 84) are in fluid communication with the fifth (815 or 825) lumens of one of the end plates (81 or 82) )

The tongues (83L, 84L) of each intermediate plate (83, 84) rest against the walls separating the fifth lumens (815, 825) from one of the end plates (81, 82) and against the central portion (800) not pierced by the central plate (80).

2. Electrical and fluidic interconnector according to claim 1, wherein the fifth lights (815, 825) of the end plates (81, 82) are of straight form delimiting straight channels.

3. electrical and fluidic interconnector according to one of claims 1 or 2, wherein the five sheets are assembled together by welding or brazing.

4. electrical and fluidic interconnector according to one of claims 4 to 7, wherein the five sheets are ferritic steel with about 20% chromium, preferably CROFER® 22APU or FT18TNb, nickel-based Inconel® 600 type or Haynes®.

5. electrical and fluidic interconnector according to one of the preceding claims, wherein each of the five sheets (80, 81, 82, 83, 84) has a thickness between 0.1 and 1mm.

6. Electrical and fluidic interconnector according to one of the preceding claims, wherein the central plate (80) has a thickness between 0.1 and 0.5 mm.

7. electrical and fluidic interconnector according to one of the preceding claims, wherein each end plate (81, 82) has a thickness between

0.1 and 0.5 mm.

8. Electrical and fluidic interconnector according to one of the preceding claims, wherein each intermediate sheet (83, 84) has a thickness between 0.5 and 1 mm.

9. Electrical and fluidic interconnector according to one of the preceding claims, wherein the unit width of a channel defined by a fifth light of an end plate is between 0.15 and 5 mm.

10. Electrical and fluidic interconnector according to one of the preceding claims, wherein the unit width of a channel defined between two consecutive tongues of an intermediate sheet is between 5 and 10 mm.

11. Electrolysis reactor comprising a stack of elementary electrolysis cells (C1, C2) SOEC type each formed of a cathode (2.1, 2.2 ..), an anode (4.1, 4.2) and a electrolyte (3.1, 3.2) interposed between the cathode and the anode, and a plurality of electrical and fluidic interconnectors (8) according to one of claims 1 to 10, each arranged between two adjacent elementary cells with one (81). ) end plates in electrical contact with the cathode (2.1) of one of the two elementary cells (C1) and the other (82) of the end plates in electrical contact with the anode (4.2) of the other (C2) of the two elementary cells.

12. The method of operating an electrolysis reactor according to claim 11, wherein: the first (811, 831, 801, 841, 821) lights are supplied with water vapor and simultaneously the fourth (814, 834, 804, 844, 824) lights with a draining gas, such as air,

the hydrogen produced by the electrolysis of the water vapor is recovered in the third (813, 833, 803, 843, 823) lumens and simultaneously the oxygen produced by the electrolysis of the water vapor in the second (812, 832, 802, 842, 822) lights.

13. SOFC fuel cell comprising a stack of elementary electrochemical cells (C1, C2) SOEC type each formed of a cathode

(2.1, 2.2 ..), an anode (4.1, 4.2) and an electrolyte (3.1, 3.2) interposed between the cathode and the anode, and a plurality of electrical and fluidic interconnectors (8) according to the one of claims 1 to 10, each arranged between two adjacent elementary cells with one (81) of the end plates in electrical contact with the cathode (2.1) of one of the two elementary cells (C1) and the another (82) end plates in electrical contact with the anode (4.2) of the other (C2) of the two elementary cells.

The method of operating an SOFC fuel cell according to claim 13, wherein:

the first (81 1, 831, 801, 841, 821) lights are supplied with air and at the same time the fourth (814, 834, 804, 844, 824) H2 hydrogen lights,

the hydrogen produced is recovered in the third (813, 833, 803, 843, 823) lumens and simultaneously the hydrogen not used in the second (812, 832,

802, 842, 822) lights.