Method for assembling an interconnector for a sofc soec module and interconnector obtained by said method

Abstract

The invention relates in particular to a method for manufacturing a single repeating unit (SRU) for an electrochemical device, in particular for a high-temperature electrolyser or a high-temperature fuel cell, said assembly comprising an interconnector (1), comprising at least a first plate (10) and a second plate (11, 12, 18, 19) which are superposed with respect to one another, and at least one current collector (21, 22). The method comprises the following steps: a) applying a braze filler material to one of the two plates, b) superposing the plates to form a single repeating unit (SRU), c) positioning in a furnace (4) so that the filler material melts and said at least two plates of said unit become brazed together.

Description

METHOD FOR ASSEMBLING AN INTERCONNECTOR FOR A SOEC / SOFC MODULE AND THE INTERCONNECTOR OBTAINED BY SAID METHOD

[0001] The invention relates to the field of electrochemical devices of the electrolyzer type and finds applications in particular in the sectors of renewable energy production and cogeneration.

[0002] The invention is of particular, but not limiting, interest in devices implementing a high-temperature electrolysis process, typically at temperatures between 100°C and 850°C, including devices known under the Anglo-Saxon name "Solid Oxide Electrolysis Cell (SOEC)" or "Solid Oxide Fuel Cell (SOFC)".

[0003] The invention relates more specifically to a method for manufacturing an interconnector and to an interconnector obtained by the method according to the invention. State of the art

[0004] An electrochemical device can be implemented for high-temperature electrolysis and include a stack of solid oxide electrolyzer cells or SOECs (solid oxide electrolyzer cell in Anglo-Saxon terminology) or as a fuel cell and include a stack of solid oxide fuel cells or SOFCs (solid oxide fuel cell in Anglo-Saxon terminology).

[0005] Such a device comprises a module (or "stack" in Anglo-Saxon terminology) consisting of a stack of electrochemical cells clamped between two clamping plates. The cells are electrically connected in series by means of interconnecting elements, also called "interconnectors".

[0006] There are several types of interconnectors, depending on the architecture of the module in which it is to be implemented.

[0007] The invention is particularly concerned with the production of flat interconnectors.

[0008] Currently, these interconnectors are made from several plates joined together, notably by laser welding: sheet metal welding, sheet metal stamping, and powder metallurgy are well-known processes for the mass production of interconnectors. However, laser welding is quite time-consuming and may not be compatible with high-volume interconnector production, at least not for producing a predetermined number desired by the customer within a given timeframe.

[0009] There is a need to change the manufacturing process of these interconnectors to reduce the manufacturing time, which is considered too long, in order to increase production capacity.

[0010] To achieve this objective, the invention proposes a method for manufacturing a single repeating unit (SRU) for an electrochemical device, in particular for a high-temperature electrolyzer or high-temperature fuel cell, said assembly comprising: an interconnector intended to be disposed on one side of an electrolysis cell of the electrochemical device, the interconnector comprising at least a first plate and a second plate superimposed with respect to each other, and at least one current collector, said method comprising the following steps: a) application of a brazing filler material to at least one of said at least two plates, b) superimposing said at least two plates so that the brazing filler material is sandwiched between said at least two superimposed plates, said at least two superimposed plates forming a single repeating unit,(c) positioning said unit, formed by said at least two superimposed plates, in a furnace for a predetermined time and at a temperature such that the filler material melts and bonds said at least two plates of said unit together by brazing, in a single repetition.

[0011] Thanks to brazing the interconnector plates, it is possible to assemble up to 1,000 SRUs in a single step. An SRU stands for "single repeating unit," meaning the unit where the electrochemical reaction takes place (a battery is an assembly of SRUs). This is possible because brazing can be performed on several interconnectors simultaneously in the same furnace, which is difficult to do with soldering.

[0012] The method according to the invention may also include the following features, taken separately or in combination:

[0013] - following a step b1), before step c) of positioning in said furnace, a brazing filler material is applied to at least one of said at least two superimposed plates and said at least one current collector is positioned on said filler material, the single repeating unit then comprising said at least two superimposed plates and said at least one current collector, so as to braze said at least two superimposed plates to said at least one current collector,

[0014] - steps a) and b), on the one hand, or a) b) and b1), on the other hand, are repeated as many times as desired to form as many single-repeat units as desired, and following a step b2), the single-repeat units are stacked one on top of the other so as to form a tower of single-repeat units, and finally, following a step c1), said tower is positioned in said furnace for a predetermined time and at a temperature such that the feed material melts and forms, by brazing, a set of stacked single-repeat units,

[0015] - following a final step d), the tower of single-repeat units is dismantled to separate the single-repeat units from each other, and the separated single-repeat units are cleaned,

[0016] - the step of applying a brazing filler material, a protective coating is applied,

[0017] - the filler material includes Chromium - or Nickel, according for example to the ISO 17672 standard

[0018] - the predetermined temperature is between 800 and 1200°C,

[0019] - said current collector comprises a grid, and the grid may advantageously be coated,

[0020] – according to an alternative embodiment, said current collector comprises a metal plate etched by a chemical process, having channels.

[0021] The invention also relates to a single repeating unit (SRU) for an electrochemical device obtained by the process as defined above. Brief description of the figures

[0022] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0023] This is a perspective view illustrating various components of a single repeating unit obtained by the process according to the invention, comprising at least one current collector and various superimposed plates of an interconnector,

[0024] This is another perspective view of a variant embodiment of a single repeating unit obtained by the process according to the invention, comprising different superimposed plates of an interconnector,

[0025] : illustrates the furnace in which a single-repeat unit tower is positioned during the brazing step of the process according to the invention,

[0026] This illustrates an example of the implementation of a current collector used in the process according to the invention, and

[0027] : lamontre a variant embodiment of a current collector used in the process according to the invention.

[0028] It is understood that the embodiments described below are by no means exhaustive. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0029] In particular, all the variants and embodiments described can be combined with each other if there are no technical obstacles to this combination.

[0030] In the figures and in the rest of the description, elements common to several figures retain the same reference. Detailed description

[0031] The aim is to produce, by the method according to the invention, a unique repeating unit.

[0032] Lamontre gives an example of elements that a single repeating unit according to the invention may include.

[0033] An interconnector 1 is observed comprising three metal plates 10, 11 and 12, as well as two current collectors 21 and 22.

[0034] The three metal plates 10 to 12 are thin sheets of specific ferritic material (K41 for example), with a thickness between 0.2 and 1 mm, in the context of this example.

[0035] Each one of them was laser-cut to cut them to the desired dimensions and also to create through openings 13, 14, 15, 16 and 17 of different shapes, depending on the shape of the elements they are designed to accommodate, for example for the passage of gas pipes (13), to receive a current collector 21 or 22.

[0036] Metal plates 10 to 12 may also have been stamped to create raised and recessed shapes, particularly to create fluidic passageways (not shown).

[0037] It is also said that the plates are configured to create the entire interconnector architecture.

[0038] It should be noted that the metal plates 10 to 12 each have one face dedicated to the passage of a gaseous fluid, for example air, and another face dedicated to the passage of a liquid fluid, for example fuel: the shapes they present are made according to these applications.

[0039] Current collectors 21 and 22 are of different types, also depending on the application for which the unit is designed and whether the current collector is intended to be carried by a face dedicated to the passage of air or to the one dedicated to the passage of fuel.

[0040] The collector 21, on the, is positioned on a plate face which is dedicated to the circulation of fuel: lamontre an example of a current collector, which is made by means of a grid 210 allowing the fuel oil to pass through while collecting the current.

[0041] The grid can be coated with nickel, for example, to facilitate brazing if necessary.

[0042] We notice on lacquer the collector 21 is covered with a cell 200.

[0043] The current collector 22, shown and intended to be positioned on a plate face dedicated to air circulation, is made from a chemically machined plate: it is noted that the plate includes channels 220 in the shape of serpentines which extend side by side over the entire length of the plate.

[0044] Lamontre also features the presence of seals 23 or 24, which ensure a seal between the elements compressed on the seal 23 or 24.

[0045] The seals 23 ensure the seal between the through openings 23 which accommodate the gas or fuel oil distribution pipes.

[0046] The seals 24 are those dedicated to ensuring a seal between the plate and the current collector. One seal 24 extends over the edge of the opening 17 to ensure a seal around it.

[0047] According to the invention, to assemble all of these elements shown in, a brazing process is used, that is to say a process according to which two elements are joined together by adding a filler material between the elements, this material joining the elements together after having been melted by the addition of heat.

[0048] Specific brazed products (paste, coating etc…) are then applied to the surface to be sealed.

[0049] For example, brazing products (also called filler materials) can be Ni710 according to ISO 17672 (material also called BNI-7 according to ANSI / AWS A5.8 and corresponding to the following formula B-Ni76CrP).

[0050] Depending on one implementation variant, the products to be brazed can be Ni613 (according to the aforementioned ISO standard, corresponding to the following formula B-Ni60CrPSi).

[0051] Such products can currently be marketed under the name BrazeLet ®.

[0052] A protective product can also be applied to the surface of the element on which the brazing filler material is to be applied: before applying said material, a little protective product is spread, for example to avoid any oxidation reaction during brazing.

[0053] It should be understood that the invention is not limited to the production by brazing of a single repeating unit such as that shown in.

[0054] The, for example, shows a variant embodiment of repeating unit whose interconnector comprises five cut and possibly stamped metal plates, this variant also conforming to the invention.

[0055] Plates 10, 11 and 12 are associated with plates 18 and 19:

[0056] As with the previous example, the plates are sheets of specific ferritic material (K41 for example), with a thickness between 0.2 and 1 mm, which have been laser cut, and possibly stamped.

[0057] They also feature through openings 13 to 17, observable in.

[0058] Reference will now be made to the process according to the invention:

[0059] After preparing the interconnector plates, as explained above, a brazing filler material will be applied to at least one of the faces of plates 10, 11, 12, 18 and 19, or to both faces for some plates.

[0060] We will also apply a brazing filler material to the plate which must be attached to a current collector.

[0061] The current collector is then positioned on the applied brazing material.

[0062] The single repeating unit, shown in figures 1 or 2, is thus made by superimposing the plates and current collectors on each other, after applying a brazing filler material.

[0063] Next, either the unit thus obtained is placed in a brazing furnace, or the units are stacked to form a tower, so as to braze several units at the same time.

[0064] The diagram schematically illustrates a tower 5 of several stacked units, which is held in position by a load 3 (for example a weight), in a brazing furnace 4.

[0065] The brazing furnace (4) is brought to a temperature T between 850 and 1100 degrees °C, so as to melt the brazing filler material which joins the elements with which it is in contact (see).

[0066] The SRU unit tower is left in the oven at brazing temperature for a time between 5 and 20 minutes.

[0067] Then, the tower is removed from the furnace, and the SRU single-repeat units are separated from each other and then cleaned. No further steps are required: the plates and current collectors are joined efficiently, cleanly, and precisely.

[0068] The tower, made by stacking several SRUs, allows many SRUs to be made at the same time, whereas soldering involves individual processing of interconnectors.

[0069] It is understood from the above how the invention makes it possible to achieve the technical objectives of achieving reliable, efficient, and achievable connections in a shorter time than that required to produce current interconnectors.

[0070] Of course, the invention is not limited to the examples that have just been described.

[0071] The above description presents a "simple" interconnector design in which only the gas distribution and chamber separation functions are shown.

[0072] An additional metal component could be added during the brazing process to create the SRU's current collector interface. These components serve to distribute current to the cell and ensure gas flow on both the fuel and air sides. For example, a mesh or a stamped or machined part could be brazed simultaneously with the interconnector. Such a brazed assembly could constitute a single, cost-effective component for the SRU. A specific coating could then be applied to both sides to create the desired interface with the cell.

Claims

A method for manufacturing a single repeating unit (SRU) for an electrochemical device, in particular for a high-temperature electrolyzer or high-temperature fuel cell, said assembly comprising: an interconnector (1) for disposition on one side of an electrolysis cell of the electrochemical device, the interconnector (1) comprising at least one first plate (10) and a second plate (11, 12, 18, 19) superimposed on each other, and at least one current collector (21, 22), said method comprising the following steps: a) applying a brazing filler material to at least one of said at least two plates (10-12, 18, 19), b) superimposing said at least two plates (10-12, 18, 19), such that the brazing filler material is sandwiched between said at least two plates (10-12, 18, 19). 19) superimposed, the said at least two plates (10-12, 18,19) thus superimposed forming a single repeating unit (SRU), c) positioning in a furnace (4) of said single repeating unit (SRU) formed by said at least two superimposed plates (10-12, 18, 19), for a predetermined time and at a temperature T such that the filler material melts and brazes said at least two plates (10-12, 18, 19) of said single repeating unit (SRU), characterized in that: steps a) and b), on the one hand, or a), b), and b1), on the other hand, are repeated as many times as desired to form as many single repeating units (SRU) as desired, in that, according to a step b2), the single repeating units (SRU) are stacked one on top of the other so as to form a tower (5) of single repeating units (SRU), and in that, according to a step c1), said tower (5) is positioned in said furnace for a predetermined time and at a temperature (T) such that the filler material melts and forms, by brazing,a set of stacked single repeating units (SRUs). A method according to the preceding claim, characterized in that, following a final step d), the tower (5) of single repeating units (SRU) is disassembled to separate the single repeating units (SRU) from each other, and in that the separated single repeating units (SRU) are cleaned. A manufacturing method according to claim 1 or 2, characterized in that following a step b1), before the positioning step c) in said furnace (4), a brazing filler material is applied to at least one of said at least two superimposed plates (10-12, 18, 19) and in that said at least one current collector (21, 22) is positioned on said filler material, the single repeating unit (SRU) then comprising said at least two superimposed plates (10-12, 18, 19) and said at least one current collector (21, 22), so as to braze said at least two superimposed plates (10-12, 18, 19) to said at least one current collector (21, 22). A manufacturing process according to any one of the preceding claims, characterized in that before the step of applying a brazing filler material, a protective coating is applied. A manufacturing process according to any one of the preceding claims, characterized in that the feed material comprises Chromium or Nickel. A manufacturing process according to any one of the preceding claims, characterized in that the predetermined temperature (T) is between 800 and 1200°C. A manufacturing method according to any one of the preceding claims, characterized in that said current collector (21) comprises a grid. Manufacturing method according to claim 7, characterized in that said grid can be coated. A manufacturing method according to any one of claims 1 to 6, characterized in that said current collector (22) comprises a chemically etched metal plate having channels. Single repeating unit (SRU) for electrochemical device obtained by the process according to any one of the preceding claims.

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