DE102023210455A1 - Material bonding for multilayer components in electrochemical cells and manufacturing processes - Google Patents

Abstract

The invention relates to a cell (1, 11) for electrolysis, at least comprising: a layer sequence of a bipolar plate (BPP), at least one cathodic gas diffusion layer (PTLC), a proton exchange membrane (PEM) between catalyst layers (CLC, CLA) or catalyst-coated membrane (CCM) and at least one anodic gas diffusion layer (PTLA), which are arranged in a frame (4), wherein a material bond (Con) is present between the individual layers of at least the BPP, PTLA(s) and/or PTLB(s).

Description

The invention relates to a multilayer component in electrochemical cells such as in electrolysis and a method for producing the electrochemical cell.

An electrolyzer is a device that uses electrical current to transform a substance (electrolysis). Due to the variety of different electrolysis processes, there are also a variety of electrolyzers, such as an electrolyzer for water electrolysis.

Current considerations are to store excess energy from renewable energy sources during periods of abundant sun and wind, i.e., when solar or wind power generation is above average. Conversion is possible using electrochemical cells, particularly fuel cells or electrolysis cells. Energy can be stored, in particular, by producing energy carriers. One chemical energy carrier is hydrogen, which is produced using water electrolyzers. This hydrogen can be used, for example, to produce so-called renewable gas.

A water electrolyzer uses electrical energy, particularly from wind or solar energy, to first generate hydrogen, oxygen, and waste heat. The hydrogen can then be combined with carbon dioxide in a Sabatier process to produce methane. The methane can then be fed into an existing natural gas grid, for example, enabling energy storage and transport to consumers and thus relieving the strain on the electrical grid. Furthermore, the hydrogen can be added to the natural gas grid or to a hydrogen-only gas grid.

Alternatively, the hydrogen produced by the electrolyzer can also be used directly, for example in a fuel cell.

In an electrolyzer for water electrolysis, water is electrochemically split into hydrogen and oxygen. In a PEM electrolyzer, distilled water is typically fed into the anode as the reactant. The water is oxidized to oxygen, protons, and electrons at the anode by a catalyst for the oxygen evolution reaction. The protons pass through the proton exchange membrane (PEM), which acts as the electrolyte.

On the cathode side, the protons are reduced with electrons to hydrogen on a catalyst for the hydrogen formation reaction.

A typical PEM electrolyzer design comprises at least one porous transport layer or gas diffusion layer for each of the anode and cathode sides, as well as one catalyst layer each. The proton exchange membrane (PEM) is arranged between the catalyst layers. The individual cells are separated by bipolar plates (BPPs). All layers are arranged in a cell frame. Currently, the arrangement of the gas diffusion layers in the cell frames must be carried out with high precision to produce a reliably functioning electrolysis cell. This makes component manufacturing and assembly complex and expensive.

From the DE 25 33 728 A1 An electrolysis cell for electrolyzing a solution of alkali salts is disclosed. The electrolysis cell comprises bipolar electrodes arranged side by side and at least one outer frame enclosing at least one chamber of the electrolysis zone.

Further electrochemical cells with sealed cell frames are available in the US 6,117,287 and the US 2002/068208 A1 described.

In the CN 107 881 528 A A manufacturing process for PEM membrane electrode assemblies is described.

In such electrochemical stacks, several cells are arranged in series and operated as a stack.

A variety of components are installed in each cell: proton exchange membrane (PEM), metallic bipolar plates (BPP), metallic or carbon-based (the latter only cathode) porous transport layers (PTL; sometimes also known as gas diffusion layers (GDL)), as well as catalyst layers (CL) and membranes (PEM).

Typically, the anodic and cathodic CLs are further processed with the PEM to form a catalyst coated membrane (CCM).

In addition, other components such as seals and frames are used. Current solutions provide for the components BPP, PTLs, CCM (as well as frames and seals) to form a individually, must be brought together one after the other and stacked repeatedly.

The components of a PEM must, for example, withstand the sometimes harsh conditions encountered during electrolysis. These include the anodic and cathodic electrochemical potentials, the oxygen or hydrogen atmosphere, and demineralized water, the acidic membrane and its potential degradation products (including HF), and metallic cation contamination, e.g., from the plant's process technology. Therefore, titanium is typically used as the base material for the BPP and anode GDL(s), while stainless steel, carbon, or even titanium is used for the cathode GDL(s).

• - Elektrochemische Verluste und Korrosion im Betrieb
• - (Elektrische ohmsche) Kontaktwiderstände an den Grenzflächen, hier zwischen den metallischen Bauteilen BPP und PTL(s), welche die Effizienz verringern
• - Grenzflächen zwischen den Bauteilen, an denen Korrosion auftreten kann.

The following challenges and problems arose:

• - Electrochemical losses and corrosion during operation
• - (Electrical ohmic) contact resistances at the interfaces, here between the metallic components BPP and PTL(s), which reduce the efficiency
• - Interfaces between components where corrosion can occur.

Both contact resistance and corrosion phenomena can increase or intensify during operation, thus impairing efficiency and possibly service life.

• - Etliche, aneinandergereihte Arbeitsschritte beim Stapeln, z.B. für jede Zelle i) Einlegen BPP, ii) Einlegen Dichtungen, iii) Einlegen Rahmen, iv) Einlegen PTL (Anode), v) Einlegen CCM, vi) Einlegen PTL (Kathode) beanspruchen Ressourcen (Zeit, Personal, Maschinenzeit).
• - Toleranzen und Toleranzausgleich sowie Positionierung aufgrund des nötigen Zusammenspiels vieler einzelner Komponenten sorgen für einen Montage- und Qualitätsaufwand von der Waren- bzw. Komponentenprüfung bis zum Stapeln des Stacks.

Manufacturing and assembly

• - Several consecutive work steps during stacking, e.g. for each cell i) inserting BPP, ii) inserting seals, iii) inserting frame, iv) inserting PTL (anode), v) inserting CCM, vi) inserting PTL (cathode) require resources (time, personnel, machine time).
• - Tolerances and tolerance compensation as well as positioning due to the necessary interaction of many individual components ensure assembly and quality effort from the inspection of goods or components to the stacking of the stack.

It is therefore an object of the invention to solve the above-mentioned problem.

The object is achieved by a cell according to claim 1 and a method according to claim 7.

The subclaims list further advantageous measures which can be combined with each other as desired in order to achieve further advantages.

• 1 eine Anordnung aus dem Stand der Technik,
• 2, 3 erfindungsgemäße Anordnungen.

It shows

• 1 a state-of-the-art arrangement,
• 2 , 3 inventive arrangements.

The figures and the description represent only embodiments of the invention.

State of the art for an exemplary cell 1' according to 1 is a solution with the components BPP, PTLs (anode, PTLA; cathode PTLC), which are stacked one after the other. Shown in 1 is a cell design with one BPP, two cathode PTLs (PTLC 1,2), three anode PTLs (PTLA 1, 2, 3), one PEM with adjacent CLA, CLC, (or one CCM).

The components are layered.

The electrical contact resistances between the individual components, which can increase with electrolysis operation time, particularly on the anode side, as well as possible corrosion surfaces are partly reduced or protected by means of relatively complex and expensive precious metal coatings (Pt, Ir).

The invention according to 2 For a cell 1 according to the invention, a material bond Con is provided between the BPP and a PTLA as well as between the PTLAs and optionally also with the metallic PTLCs.

The invention according to 3 shows an example of a cell 11 with structured BPP, i.e. the use of flow fields, e.g. in the form of channels, and also material bonds Con between the webs of the BPP and the PTLAs and optionally also with one or the metallic PTLCs.

This has the advantage, among other things, of reducing the contact surfaces and thus the area in which the material bond is to occur, which simplifies the bonding process. It is advantageous to keep the proportion of the cross-sections of the channels 14 at 40% to 60%, relative to the total cross-sectional area of the PTLC or PTLA1.

In principle, the bond between BPP and PTLs can be achieved using a suitable joining process, such as sintering, soldering, or welding. The individual components can be bonded together either simultaneously or sequentially, and preferably each component can be checked for shape and position tolerances one after the other.

This solution can be applied not only for systems or cells 1, 11 of water electrolysis ( 2 and 3 ), but also in other electrochemical cells, e.g. fuel cells, galvanic cells, etc.

As an example for PEM water electrolysis, the various components (BPP, PTLs, CCMs, frames, seals, etc.) are currently manufactured individually and assembled and stacked one after the other.

Instead, the invention described above enables an upstream material bond or pre-assembly of the BPP and PTLs.

• - Der Stoffschluss zw. BPP und PTL(s) vermeidet Kontaktstellen, an denen elektrische Kontaktwiderstände entstehen.
• - Der Stoffschluss zw. BPP und PTL(s) vermeidet elektrisch schlecht leitende Metalloxidschichten, welche typischerweise während des Elektrolysebetriebs anwachsen, und damit verbundene ohmsche Widerstände.
• - Der Stoffschluss zw. BPP und PTL(s) vermeidet Grenzflächen, an denen Korrosion auftreten kann.
• - Eine Beschichtung der Kontaktstellen bzw. Grenzflächen ist nicht mehr nötig.

This invention therefore offers advantages both during stack manufacturing and assembly, as well as during operation. This could result in savings and improvements in costs such as CAPEX and OPEX, as described below. Electrochemical losses and corrosion during operation

• - The material bond between BPP and PTL(s) avoids contact points where electrical contact resistance occurs.
• - The material bond between BPP and PTL(s) avoids electrically poorly conducting metal oxide layers, which typically grow during electrolysis operation, and the associated ohmic resistances.
• - The material bond between BPP and PTL(s) avoids interfaces where corrosion can occur.
• - Coating of the contact points or interfaces is no longer necessary.

• - Montageerleichterung durch Verringerung der Arbeitsschritte, da nur noch ein bereits vorgefertigter Komponentenverbund eingelegt werden müsste.
• - Ein höherer Automatisierungsgrad der Montierung kann einfacher erfolgen, da z.B. der Komponentenverbund mittels Roboter geführt und eingesetzt werden könnte.
• - Die Positionierung bzw. die Formtoleranz von PTL(s) und BPP zueinander kann bereits während der Vormontage erfolgen und überprüft werden. Somit wird ein mögliches Verrutschen der einzelnen Komponenten zueinander während der nachgelagerten Montageprozesse vermieden.
• - Austausch in Reparatur und Serviceanwendungen kann durch Zusammenfügen des Komponentenverbundes vereinfacht werden.

Manufacturing and assembly

• - Easier assembly by reducing the number of work steps, as only a prefabricated component assembly would have to be inserted.
• - A higher degree of automation of the assembly can be achieved more easily, since, for example, the component assembly could be guided and inserted by robots.
• - The positioning and shape tolerance of PTL(s) and BPP relative to each other can be determined and checked during pre-assembly. This prevents any possible slippage of the individual components relative to each other during downstream assembly processes.
• - Replacement in repair and service applications can be simplified by assembling the component assembly.

The individual layers (PTLC, BPP, PTLA) are preferably joined one after the other, i.e. in particular first the one ( 3 ) or individual PTLCs, then the BPP is joined and at the end the individual PTLAs.

The individual layers (PTLC, BPP, PTLA) can also preferably be joined together all at once.

Preferably, it is possible to join several layers (PTLC, BPP, PTLA) together, but not all at once, i.e. PTLC1 + PTLC2, then BPP + PTLA1, then PTLA2 + PTLA3.

It is also preferable to join the individual layer types (PTLCs, PTLAs) separately and then optionally join them with the bipolar plate (BPP).

It can be joined over large areas, but also in spots, linearly, or meandering, reducing energy input and effort. This is particularly useful for welding.

Individual or multiple components can be joined together using sintering, welding or soldering.

The fabric closure Con is clearly visible.

If the joining was done by sintering, a diffusion area is present between the layers (PTLC, BPP, PTLA).

If the joining was done by welding, there is at least one molten area between the layers (PTLC, BPP, PTLA) and/or another microstructure or grain structure.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 25 33 728 A1 [0009]
• US 6,117,287 [0010]
• US 2002/068208 A1 [0010]
• CN 107 881 528 A [0011]

Claims (14)

Cell (1, 11) for electrolysis comprising at least: a layer sequence consisting of a bipolar plate (BPP), at least one cathodic gas diffusion layer (PTLC), a proton exchange membrane (PEM) between catalyst layers (CLC, CLA) or a catalyst-coated membrane (CCM) at least one anodic gas diffusion layer (PTLA), which are arranged in a frame (4), wherein at least one material bond (Con) is present between the individual layers of at least the bipolar plate (BPP), at least one anodic gas diffusion layer (PTLA), and/or at least one cathodic gas diffusion layer (PTLC). Cell after Claim 1 , the frame (4) of which has at least one seal (7) adjacent to the proton exchange membrane (PEM). Cell after Claim 1 or 2 , whose bipolar plate (BPP) is structured and has a flow field (14), in particular in which the channels make up 60% to 40% of the cross-sectional area of the bipolar plate (BPP). Cell according to one or more of the Claims 1 , 2 or 3 which has at least two cathodic gas diffusion layers (PTLC) and/or at least three anodic gas diffusion layers (PTLA). Cell according to one or more of the Claims 1 , 2 or 3 which has only one cathodic gas diffusion layer (PTLC) and/or at most two anodic gas diffusion layers (PTLA). Cell according to one or more of the Claims 1 , 2 , 3 , 4 or 5 in which each individual layer is joined together, in particular the bipolar plate (BPP), with a cathodic gas diffusion layer (PTLC) and in particular also the anodic and cathodic gas diffusion layers (PTLA, PTLC) each with each other- Method for producing a cell (1, 11) according to one or more of the preceding claims, in which individual layers (PTLC, BPP, PTLA) are joined together. Procedure according to Claim 7 , in which the individual layers (PTLC, BPP, PTLA) are joined together one after the other. Procedure according to Claim 7 in which the individual layers (PTLC, BPP, PTLA) are joined together at once. Procedure according to Claim 7 , in which several layers (PTLC, BPP, PTLA) are joined together, but not all layers at once. Procedure according to Claim 7 , in which the individual layer types (PTLC's, PTLA's) are joined separately and then optionally joined with the bipolar plate (BPP). Procedure according to Claim 7 , 8 , 9 , 10 or 11 , in which the shape and position of the layers (PTLC, BPP, PTLA) are checked after each joining. Method according to one of the preceding claims, in which the joining is carried out by sintering and/or welding Procedure according to Claim 13 , where the welding is carried out pointwise, linearly or meanderingly.

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