WO2024183856A1

WO2024183856A1 - Component for an electrochemical cell, redox flow cell, fuel cell, and electrolyser

Info

Publication number: WO2024183856A1
Application number: PCT/DE2024/100161
Authority: WO
Inventors: Sebastian Etschel; Bertram Haag; Jan-Peter Viktor SCHINZEL; Christopher Kalb; Mehmet OETE
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2023-03-03
Filing date: 2024-02-28
Publication date: 2024-09-12

Abstract

The invention relates to a component (1) of an electrochemical cell (10), said component (1) comprising a metal substrate (2) and a layer system (3) that is electroplated and/or chemically deposited onto at least part of the metal substrate (2); the layer system (3) optionally comprises a first layer (3a) disposed on the metal substrate (2), and comprises at least one second layer (3b) that is disposed on the metal substrate (2) or, if applicable, on the first layer (3a), the optional first layer (3a) being made of copper or nickel, and the at least one second layer (3b) being made of an alloy comprising at least two of the elements tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum and niobium, and nonmetal particles comprising electrically conductive particles being incorporated into the alloy. A cover layer (33) is formed on the free side of the at least one second layer (3b) of the layer system (3), which is optionally oxidized and faces away from the metal substrate (2), and the cover layer is either a) made of a metal carbide or a metal nitride or an amorphous carbon, or b) of at least one self-organized organic monolayer or at least one polymer.

Description

Component for an electrochemical cell, as well as redox flow cell, fuel cell and electrolyzer

The invention relates to a component of an electrochemical cell, comprising a metal substrate and a layer system applied at least partially to the metal substrate by galvanic and/or chemical means, wherein the layer system optionally comprises a first layer arranged on the metal substrate and at least one second layer arranged on the metal substrate or, if present, on the first layer, wherein the optional first layer is formed from copper or nickel and the at least one second layer is formed from an alloy comprising at least two of the elements tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum, niobium, wherein non-metallic particles comprising electrically conductive particles are incorporated in the alloy. The invention further relates to electrochemical cells in the form of redox flow cells, electrolyzers and fuel cells.

Hydrogen is an important raw material for key technologies with regard to future energy storage and energy conversion. Water electrolysis is based on the decomposition of water into its components hydrogen (H2) and oxygen (O2). A hydrogen-powered fuel cell generates electrical energy from the hydrogen. Reducing the hydrogen production costs through electrolyzers comprising a polymer electrolyte membrane (PEM-EL) and reducing the production costs of the components of a fuel cell comprising a polymer electrolyte membrane (PEM-FC) are a basic prerequisite for the future efficient use of these systems. The main components of a PEM electrolyzer stack/PEM fuel cell stack are the bipolar plates (BiP), the current collectors or fluid diffusion layers and the membrane electrode assembly (MEA). The materials and the production of the bipolar plates contribute a not insignificant proportion to the production costs of the respective stacks. The essential requirements for the components, such as the bipolar plates and fluid diffusion layers, in both application areas are high corrosion resistance combined with low substrate and interface resistances. Titanium and stainless steel plates are the state of the art in electrolysis. While the field of application of stainless steel plates on the anode side is limited to pH ranges around 7 due to the high oxidation potentials involved, titanium plates can be used over a wide pH range from 1 to 7. On the cathode side, titanium proves to be disadvantageous because it tends to become brittle due to hydrogen. Furthermore, the operation of electrolyzer stacks with titanium plates shows an increase in ohmic losses due to surface passivation. Against this background, the use of niobium, platinum or gold coatings on titanium plates is known. The extensive use of stainless steel to form a bipolar plate requires the use of an electrochemically stable, conductive and, in particular, dense, impermeable coating. In particular, impermeability to aqueous electrolytes should be achieved.

In the case of PEM fuel cells, the potential windows are more moderate and the pH range is largely limited to 3. However, local operating conditions can occur in the cell that can lead to potentials >1.4 V NHE (normal hydrogen electrode). This requires the use of layers containing precious metals such as Ir, Ru or Au, whose material costs, despite layer thicknesses in the nm range, are above the target cost range for bipolar plates of $3/kW (generally accepted target of the US Department of Energy for the year 2025).

WO 2023 274 441 A1, which probably represents the closest prior art, describes some components and electrochemical cells of the type mentioned above.

EP 3 336 942 A1 describes a metal sheet for forming a separator for a polymer electrolyte fuel cell. The metallic substrate has a film coating the surface of the substrate, with an island-shaped intermediate layer between the substrate and the film. The intermediate layer comprises at least one element from the group comprising nickel, copper, silver, gold, or is formed from a NiP alloy. As an exemplary embodiment, a substrate made of stainless steel with an island-shaped intermediate layer made of NiP and an electrochemically applied film made of TiN-dispersed NisSn2 is described. JP 2010-272 429 A discloses a separator for a fuel cell with a substrate made of copper or a copper alloy coated with at least one wet-chemically formed first layer made of tin or a tin alloy. The first layer can contain a conductive filler, in particular in the form of carbon.

US 2019 / 0 148 741 A1 describes an electrochemical device such as a fuel cell, a battery, an electrolyzer, a redox flow battery, comprising a coated component that has a substrate preferably made of a metal such as copper, iron, titanium, aluminum, nickel or stainless steel. The substrate has a coating of tin or a tin alloy, such as a tin-nickel alloy, a tin-antimony alloy, a tin-nickel-antimony alloy, and an electrically conductive coating comprising a carbon-based material and an azole-containing corrosion inhibitor. Flow battery systems as storage systems also enable a sustainable energy supply for stationary and mobile applications using renewable energies. In order to achieve high efficiencies and power densities, the aim is to create battery stacks that are as compact as possible. However, high power densities pose major challenges for the individual components of a battery stack. A new approach here is a metallic electrode with a structured geometry to ensure a homogeneous distribution of an electrolyte in the active area and at the same time enable small distances to the membrane. On the other hand, metallic electrodes require corresponding surface properties that meet the high requirements for electrochemical stability, low interfacial resistance and catalytic activity.

In a redox flow cell, composite plates comprising plastic and graphite (thickness ~0.5 - 0.6 mm) with a carbon black active coating (thickness ~0.1 - 0.3 mm) applied on both sides, which is dry-pressed or wet-chemically applied, are often used as electrodes. This results in a total plate thickness of the electrode of ~0.7 - 1.2 mm. With metallic plates, thicknesses of < 0.5 mm can be achieved in large-area dimensions. It can also be assumed that the processability The cost of large-area metallic plates is more favorable compared to injection-molded plastic frames with graphite-based electrodes.

Another cell configuration, such as the all-vanadium redox flow cell, consists of two bipolar plates in the form of two electrodes, usually with graphite felt to increase the active surface, and a membrane. The electrolyte consists of vanadium dissolved in sulfuric acid (pH < 1). The bipolar plates (thickness about 0.5 - 0.6 mm) are usually used as planar plates made of pure graphite or a graphite-polymer compound. Bipolar plates made of polypropylene filled with graphite or carbon nanotubes are characterized by high corrosion resistance and high overvoltages for the hydrogen formation reaction (HER).

Compared to bipolar plates made of graphite composites, metallic bipolar plates are characterized by their higher electrical conductivity and higher mechanical stability or strength, which in cell configurations with graphite felt lead to higher performance and efficiency due to low ohmic losses.

In the PEM-EL, PEM-BZ and redox flow cell applications, electrically conductive, dense coatings are required. These act as a barrier layer and can be increased in terms of their performance, particularly catalytic effectiveness, by applying additional layers. The requirements can be summarized as follows: Electrochemical stability: pH range: 1-14

Potential range: -1 V NHE to +3 V NHE (short term: -2 V NHE to +3 V NHE)

Running time: > 10000 h

Interface resistance:

< 10 mOhm cm ² (at 100 N/cm ² contact pressure) It is the object of the invention to provide a component for an electrochemical cell which meets these requirements for electrochemical stability and low interfacial resistance in an improved form. Furthermore, it is the object of the invention to provide an electrochemical cell in the form of a redox flow cell, an electrolyzer or a fuel cell with such a component.

The object is achieved for the component of an electrochemical cell, comprising a metal substrate and a layer system applied at least partially to the metal substrate galvanically and/or chemically, wherein the layer system optionally comprises a first layer arranged on the metal substrate and at least one second layer arranged on the metal substrate or, if present, on the first layer, wherein the optional first layer is formed from copper or nickel and the at least one second layer is formed from an alloy comprising at least two of the elements tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum, niobium, wherein non-metallic particles comprising electrically conductive particles are incorporated in the alloy, in that on the free side of the at least one second layer of the layer system facing away from the metal substrate, which is optionally treated with an oxygen plasma and oxidized, a cover layer is formed which is either a) formed from a metal carbide or a metal nitride or an amorphous carbon or b) from at least one self-organizing organic monolayer or at least one polymer.

The electrically conductive particles have an electrical conductivity in a temperature range of 20 to 25°C in a range of 0.25 mQcm ² to 10 mQcm ² .

Such components have excellent electrochemical stability, as required in electrochemical cells. Due to the low interfacial resistance, such components are particularly suitable for the formation of electrodes in redox flow cells, bipolar plates for fuel cells and electrolyzers and of fluid diffusion layers of electrolyzers. The presence of non-metallic particles, which are embedded in the alloy in the second layer, improves the mechanical stability of the layer system and also enables, depending on the material of the particles used, a further reduction in the interfacial resistance and thus an increase in the efficiency of the electrochemical cell.

Preferably, the surface of the second layer is oxidized. In particular, only the atoms of the second layer located on the surface are oxidized, thus activating the second layer for a strong bond to the cover layer. Preferably, the surface of the second layer is oxidized by exposing it to an oxygen plasma. The oxygen plasma ensures a dense and compact oxide layer on the surface of the second layer. However, oxidation of the surface of the second layer by anodization is also possible.

According to case a), in a preferred embodiment the cover layer is formed from a metal carbide containing at least one of the metals from the group comprising tungsten, cobalt, chromium, nickel.

According to case a), in a further preferred embodiment the cover layer is formed from a metal nitride in the form of silicon nitride or a silicon nitride doped with boron and carbon.

According to case a), in a further preferred embodiment, the cover layer is formed from an amorphous carbon (according to VDI Guideline No. 2840 from 2012, Table 1), wherein hydrogen-free and hydrogen-containing amorphous carbon layers provided with metallic and/or non-metallic doping elements are to be included. Possible doping elements X are one or more elements from the group comprising Ti, Nb, W, Zr, Ta, Hf, Mo, Cu, Si, Pt, Pd, Ru, Ir, Ag, B, N, P, F, H, 0, where 0 < X < 20 at.%. In particular, the amorphous carbon layer is in the form of a tetrahedral amorphous carbon layer of the type ta-C:X with at least one doping element X = Ti, Nb, W, Zr, Ta, Hf, Mo, Cu, Si, Pt, Pd, Ru, Ir, Ag, B, N, P, F, H, 0, where 0 < X < 20 at.%. According to case a), the cover layer is preferably formed using a PVD or CVD process.

According to case b), in a further preferred embodiment, the cover layer is formed from at least one self-organizing organic monolayer, which is formed in particular from a fatty acid derivative or alkyl-phosphonic acid derivative with a chain length of 5 to 30 carbon atoms. Both the fatty acid derivative and the alkyl-phosphonic acid derivative can preferably be present with perfluorinated alkyl chains or partially fluorinated alkyl chains or with completely unsubstituted alkyl chains.

According to case b), in a further preferred embodiment, the cover layer is formed from at least one polymer, in particular from a polymer with perfluorinated chains, such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

According to case b), the cover layer is preferably formed using a spraying or doctor blade process. Alternatively, the cover layer in case b) can also be formed using a spin-casting process or a dipping process.

The materials tin and nickel proved to be thermodynamically stable over a wide pH range due to the formation of oxides. An alloy made of a tin-nickel alloy with a nickel content in the range of 20 to 35 wt.% is therefore particularly preferred. Such a low nickel content is of great advantage in terms of reduced nickel diffusion into the membrane of an electrochemical cell, as this leads to a minimization or prevention of nickel poisoning of the membrane and thus effectively prevents a drop in cell performance. As a result, second layers made of such a tin-nickel alloy with electrically conductive particles dispersed therein, in particular made of carbon and/or graphite and/or carbon nanotubes and/or carbon fibers and/or soot and/or graphene and/or graphene oxide, proved to be more stable in the long term than comparable layers made of gold. The alloy is alternatively formed from a copper-tin alloy or a tin-silver alloy or a tin-zinc alloy or a tin-bismuth alloy or a tin-antimony alloy or a tin-cobalt alloy or a nickel-tungsten alloy or a tin-manganese alloy or a tin-tantalum alloy or a tin-niobium alloy or a tin-nickel-niobium alloy or a tin-nickel-tantalum alloy or a tin-tantalum-niobium alloy. Particularly preferred of these are the tin-tantalum alloy or tin-niobium alloy or tin-nickel-niobium alloy or tin-nickel-tantalum alloy or tin-tantalum-niobium alloy.

In particular, SnCu has proven to be an efficient material composition in the redox flow cell when using alkaline electrolytes.

The first layer is made of copper or nickel. This ensures good adhesion of the layer system to the metal substrate.

The non-metallic particles preferably comprise a proportion of electrically conductive particles which bring about a significant reduction in the interfacial resistance on the component and are in particular formed from at least one material from the group comprising carbon, graphite, carbon nanotubes, carbon fibers, soot, graphene, graphene oxide, metal nitride, metal carbide.

In particular, the proportion of electrically conductive particles is more than 50% of the non-metallic particles. It has been shown that the electrically conductive particles protruding from the second layer reliably maintain the electrical contact between the membrane of the electrochemical cell and the electrical contacts outside the electrochemical cell, even under highly corrosive conditions.

Particularly preferred is a combination of an alloy of a tin-nickel alloy with a nickel content in the range of 20 to 35 wt.% with non-metallic particles dispersed therein of at least one material from the group comprising carbon, graphite, carbon nanotubes, carbon fibers, carbon black, graphene, graphene oxide. This alloy forms an oxide layer on its surface as Passivation, which has a particularly corrosion-inhibiting effect and increases the long-term stability of the electrochemical cell.

The non-metallic particles may further comprise a proportion of particles formed from a non-electrically conductive material, such as at least one material from the group comprising metal sulfide, metal oxide, diamond, mica, PTFE.

Preferably, AI2O3, BeO2, CdO, MgO, SiC>2, TiC>2, ZrÜ2, Fe oxides and the like are used as metal oxides. Preferably, SiC, WC, VC, TiC, Cr2Cs, CrsC2 and the like are used as metal carbides. Preferably, BN or SiN and the like are used as metal nitrides. Particularly preferably, carbon is used in the form of graphite, carbon nanotubes, carbon fibers, soot, graphene or in the form of graphene oxide. Preferably, M0S2, MoS, NiFeS2 and the like are used as metal sulfides.

A preferred particle size of the non-metallic particles is in a range from 100 nm to 8 pm, in particular in the range from 500 nm to 6 pm. Particular preference is given to using particles in the nanometer range that can be dispersed particularly stably in an electrolyte for the galvanic deposition of the second layer. In particular, the particle size is selected such that they protrude from the surface of the at least one second layer and thus ensure contact with a membrane.

A preferred volume fraction of non-metallic particles in the second layer is in the range of 2 to 50 vol.%. This ensures reliable binding of the particles in the metallic matrix.

The metal substrate is preferably made of a material from the group comprising stainless steel, such as grades 1.4404 or DC04, furthermore titanium, a titanium alloy, Aluminium, an aluminium alloy, an alloy containing predominantly tin. In this case, the first layer is preferably present to improve the adhesion of the layer system.

Alternatively, the metal substrate is made of a material from the group comprising copper, a copper alloy, nickel, a nickel alloy, a low-alloy carbon steel. In particular, the metal substrate is made of copper or nickel. In such a case, the first layer can also be omitted. 100Cr6 has proven to be a good low-alloy carbon steel.

The optional first layer and the at least one second layer are formed by galvanic and/or chemical deposition. Using galvanic processes, the deposition of electrolyte-tight layers with a layer thickness of >10 micrometers for use in PEM-EL and redox flow cells is easily possible. This makes it possible to achieve galvanically deposited, conductive and resistant layers on metallic substrates, such as stainless steel, over a wide pH and potential window. The non-metallic particles are dispersed in an electrolyte to form the second layer and incorporated into the alloy deposited on the first layer to form the at least one second layer.

A single second layer or several second layers can be applied on top of each other.

In particular, the galvanic deposition is carried out using a so-called "pulse plating" process, in which the voltage applied to the electrolyte is periodically switched off or reversed. The short-term current pulses received when switching on increase the number of nuclei for metal deposition, thus creating a basis for fine-grained deposits and shine. A chemical application of the layer system comprising the optional first layer and the at least one second layer is understood to mean an autocatalytic deposition, wherein the deposited alloy itself catalyzes the further deposition, so that the depositable layer thickness is not limited from a process point of view.

The metal substrate is in particular in the form of a metal sheet or a metal foil with a thickness in the range of 0.05 to 1 mm. Furthermore, the metal sheet or the metal foil can have embossed three-dimensional structures in order to enlarge the surface and thus increase the contact area with a fluid in an electrochemical cell.

The first layer preferably has a layer thickness of up to 5 pm, in particular in the range of up to 3 pm. The at least one second layer preferably has a layer thickness of up to 30 pm, in particular in the range of 5 to 20 pm.

The cover layer preferably has a layer thickness in the range from 1 nm to 1 pm. In case b), the layer thickness of the cover layer is preferably in the range from 1 nm to 100 nm. The preferred total layer thickness of the layer system is < 10 pm and is in particular in the range from 4 to 8 pm.

The component according to the invention is preferably designed in the form of an electrode for a redox flow cell, wherein the layer system covers the metal substrate at least in a contact area with an electrolyte, optionally further in a contact area with a graphite felt through which electrolyte flows, of the redox flow cell.

The object is further achieved for a redox flow cell, in particular a redox flow battery, comprising at least one electrode for the redox flow cell and at least one electrolyte, in particular with a pH value in the range from -1 to 14. The redox flow cell preferably comprises at least two electrodes, a first reaction chamber and a second reaction chamber, each reaction chamber being in contact with one of the electrodes and the reaction chambers being separated from one another by an ion exchange membrane. A graphite felt can be arranged in each of the reaction chambers, which is arranged adjacent to the respective electrode.

To form a redox flow battery, preferably more than 10, in particular more than 50 redox flow cells are used, electrically interconnected.

The following is an example of anolyte suitable for a redox flow cell or a redox flow battery:

1.4 M 7,8-dihydroxyphenazine-2-sulfonic acid (DHPS) dissolved in 1 molar sodium hydroxide solution

The following is an example of a catholyte suitable for a redox flow cell or a redox flow battery:

0.31 M potassium hexacyanoferrate(II) and 0.31 M potassium hexacyanoferrate(III) dissolved in 2 molar sodium hydroxide solution.

Electrolyte combinations with aqueous electrolytes with a redox-active organic and/or metallic species on the anolyte side are preferably used to form a redox flow cell or a redox flow battery.

Another electrolyte (anolyte or catholyte) suitable for the redox flow cell is mentioned here as an example:

1.6M VOSO4 or V2(SO4)3 dissolved in aqueous dilute sulfuric acid (pH < 1).

The object is further achieved for a fuel cell comprising at least one component according to the invention in the form of a bipolar plate and at least one polymer electrolyte membrane. Finally, the object is achieved for an electrolyzer comprising at least one component according to the invention in the form of a bipolar plate or a fluid diffusion layer and at least one polymer electrolyte membrane. The electrolyzer is preferably designed for the electrolysis of water.

The following examples are intended to illustrate a component according to the invention:

Example 1 :

Metal substrate: Stainless steel Electroplated first layer: Copper or nickel Electroplated second layer (DC, Pulse Plating):

Alloy: SnNi non-metallic particles: graphite

Oxidation of the free surface of the second layer, e.g. in oxygen plasma: Yes Top layer:

(12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 18-pentadecafluoro-octadecyl)-phosphonic acid

Example 2:

Metal substrate: Titanium electroplated first layer: Copper or nickel electroplated second layer (DC, Pulse Plating):

Alloy: SnAg non-metallic particles: titanium nitride and SiC

Oxidation of the free surface of the second layer, e.g. in oxygen plasma: Yes Top layer: (3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10,10,10- heptadecafluoro)- decylphosphonic acid

Example 3:

Metal substrate: copper electroplated first layer: not applicable electroplated second layer (DC, Pulse Plating):

Alloy: SnCu non-metallic particles: graphite and SiC Oxidation of the free surface of the second layer: No

Top layer: tungsten carbide

Metal substrate: Aluminium electroplated first layer: Copper or nickel electroplated second layer (DC, Pulse Plating):

Alloy: SnZn non-metallic particles: graphene oxide and SiO2

Oxidation of the free surface of the second layer, e.g. in oxygen plasma: Yes

Top layer: (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10- heptadecafluorodecyl)-carboxylic acid

Metal substrate: stainless steel electroplated first layer: copper or nickel electroplated second layer (DC, pulse plating): alloy: SnBi non-metallic particles: graphene and WC

Oxidation of the free surface of the second layer: No

Top layer: PVDF

Alloy: SnSb or SnMn non-metallic particles: soot and mica

Oxidation of the free surface of the second layer: No

Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

Metal substrate: stainless steel electroplated first layer: copper or nickel galvanically produced second layer (DC, Pulse Plating):

Alloy: SnCo non-metallic particles: carbon nanotubes and MgO

Oxidation of the free surface of the second layer: No

Top layer: silicon nitride

Example 8:

Alloy: NiW non-metallic particles: graphite and M0S2

Oxidation of the free surface of the second layer: No

Cover layer: PTFE

Example 9:

Alloy: SnNi non-metallic particles: graphite and SiC

Oxidation of the free surface of the second layer: No

Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

Example 10:

Metal substrate: stainless steel galvanically or chemically produced first layer: copper or nickel autocatalytically (chemically) produced second layer:

Alloy: SnTa or SnNb non-metallic particles: graphite

Oxidation of the free surface of the second layer: Yes

Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen) Example 11 :

Metal substrate: stainless steel galvanically or chemically produced first layer: copper or nickel autocatalytically (chemically) produced second layer: alloy: SnNiNb or SnNbTa or SnNiTa non-metallic particles: graphite

Oxidation of the free surface of the second layer: Yes

Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

Figures 1 to 8 show examples of components and their use in electrochemical cells.

Figure 1 shows a component comprising a metal substrate and a layer system;

Figure 2 shows the component according to Figure 1 in a sectional view;

Figure 3 shows another component with three-dimensional structuring in side view;

Figure 4 shows a component with an integral metal substrate and first layer;

Figure 5 shows a component in the form of an electrode with a three-dimensionally structured flow field;

Figure 6 a redox flow cell or a redox flow battery with a redox flow cell,

Figure 7 shows an electrolyzer in cross-section and

Figure 8 shows a fuel cell stack in a three-dimensional view.

Figure 1 shows a component 1 comprising a metal substrate 2 and a layer system 3 (see Figure 2) as well as a cover layer 33 in a plan view of a surface 4a.

Figure 2 shows the component 1 according to Figure 1 in section ll-ll. The same reference symbols as in Figure 1 identify the same elements. The metal substrate 2 can now be seen, here made of stainless steel, for example, in the form of a metal sheet. The metal sheet is Electroplated on both sides with a first layer 3a made of nickel with a layer thickness of 1 pm. On the first layer 3 there is a second layer 3b made of a tin-nickel alloy containing non-metallic particles of graphite with a layer thickness in the range of 5 pm. The surface 4b of the second layer 3a is treated in an oxygen plasma and oxidized. On the layer system 3 made of first layer 3a and second layer 3b there is a cover layer 33 made of PTFE with a layer thickness of 5 nm.

Figure 3 shows a further component 1 ' with three-dimensional structuring 5 in side view. The component 1 ' comprises a metal substrate 2, not visible here, which is covered on all sides by a layer system 3 and a cover layer 33

Figure 4 shows a component 1" in cross section, which has a metal substrate 2 made of nickel. The metal substrate 2 simultaneously forms the first layer 3a. The second layer 3b galvanically formed thereon is made of a tin-nickel alloy containing non-metallic particles of graphite and SiC in a layer thickness of 10 pm. On top of this there is a cover layer 33 made of silicon nitride in a layer thickness of 0.1 pm.

Figure 5 shows a component 1a in the form of an electrode in a three-dimensional view comprising a metal substrate 2 in the form of a metal sheet made of titanium coated with a layer system 3 and a cover layer 33. In the metal substrate 2 there is a three-dimensional structuring 5 for forming a flow field 7, so that an enlargement of the surface of the electrode results, which is to be flowed by an electrolyte in a redox flow cell 8 (see Figure 6).

Figure 6 shows a redox flow cell 8 or a redox flow battery with a redox flow cell 8. The redox flow cell 8 comprises two components 1a, 1b in the form of electrodes (see Figure 5), a first reaction chamber 10a and a second reaction chamber 10b, each reaction chamber 10a, 10b being in contact with one of the electrodes. Graphite felt, which is not shown separately here, can be arranged in the reaction chambers 10a, 10b. The flow fields 7 (not visible here) The electrodes (same figure 5) are oriented towards an ion exchange membrane 9a and, if present, the respective graphite felt. The reaction spaces 10a, 10b are separated from one another by the ion exchange membrane 9a. The graphite felt, if present, is inserted at least slightly compressed between the respective electrode and the ion exchange membrane 9a, whereby electrolyte liquid can flow through the graphite felt. In the area of a structured surface of the electrode, the electrolyte can partially flow past the graphite felt and continue to flow through it. A liquid anolyte 11a is pumped from a tank 13a into the first reaction space 10a via a pump 12a and passed between the component 1a and the ion exchange membrane 9a. A liquid catholyte 11b is pumped from a tank 13b via a pump 12b into the second reaction chamber 10b and passed between the component 1b and the ion exchange membrane 9a. An ion exchange takes place across the ion exchange membrane 9a, whereby electrical energy is released due to the redox reaction at the electrodes.

Figure 7 shows an electrolysis cell 20 of an electrolyzer comprising a polymer electrolyte membrane 9, which separates an anode side A and a cathode side K from one another. On both sides of the polymer electrolyte membrane 9, a catalyst layer 21a, 21b, each comprising a catalyst material and a fluid diffusion layer 22a, 22b made of titanium (anode side) and a graphite felt (cathode side), is arranged adjacent to the catalyst layer 21a, 21b. The fluid diffusion layers 22a, 22b are each arranged adjacent to a component 1e, 1f in the form of an electrically conductive plate. The plates are made of stainless steel and have a galvanically applied layer system 3 and a cover layer 33 (see Figure 2) at least on their sides facing the fluid diffusion layers 22a, 22b. The plates further each have a three-dimensional structuring 5, which forms flow channels 23a, 23b on the sides of the plates facing the fluid diffusion layers 22a, 22b in order to improve a supply of reaction medium (water) and a removal of reaction products (water, hydrogen, oxygen). Figure 8 shows a schematic of a fuel cell stack 100 comprising a plurality of fuel cells 90. Each fuel cell 90 comprises a polymer electrolyte membrane 9, which is adjacent to both sides of components 1c, 1d in the form of bipolar plates. Each bipolar plate has a metal substrate 2 with a galvanically applied layer system 3 and a cover layer 33 (see Figure 2). The bipolar plate has an inflow area with openings 80a and an outlet area with further openings 80b, which serve to supply a fuel cell 90 with process gases and coolant and to remove reaction products from the fuel cell 90 and coolant. The bipolar plate also has a gas distribution structure 6 on each side, which is intended to be in contact with the polymer electrolyte membrane 9.

Figures 1 to 8 are intended to illustrate the invention merely by way of example. However, further electrochemical cells with at least one component designed according to the invention are intended to be included in the inventive concept.

List of reference symbols

1 , r, 1", 1a, 1 b, 1c, 1d, 1e, 1f Component

2 Metal substrate

3 layer system

3a first layer

3b second layer

33 Top layer

4a, 4b Surface

5 three-dimensional structuring

6 Gas distribution structure

7 River field

8 Redox flow cell

9 Polymer electrolyte membrane

9a ion exchange membrane

10a first reaction chamber

10b second reaction chamber

11a Anolyte

11 b Catholyte

12a, 12b Pump

13a, 13b Tank

20 Electrolysis cell

21a, 21 b Catalyst layer

22a, 22b Fluid diffusion layer

23a, 23b Flow channels

80a, 80b openings

90 Fuel cell

100 fuel cell stacks

A Anode side

K Cathode side

Claims

Patent claims

1. Component (1) of an electrochemical cell (10), comprising a metal substrate (2) and a layer system (3) applied at least partially to the metal substrate (2) galvanically and/or chemically, wherein the layer system (3) optionally comprises a first layer (3a) arranged on the metal substrate (2) and at least one second layer (3b) arranged on the metal substrate (2) or, if present, on the first layer (3a), wherein the optional first layer (3a) is formed from copper or nickel and the at least one second layer (3b) is formed from an alloy comprising at least two of the elements tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum, niobium, wherein non-metallic particles comprising electrically conductive particles are incorporated in the alloy, characterized in that on the free side facing away from the metal substrate (2) of the at least one second layer (3b) of the layer system (3), which optionally is oxidized, a cover layer (33) is formed which is either a) formed from a metal carbide or a metal nitride or an amorphous carbon or b) formed from at least one self-organizing organic monolayer or at least one polymer.

2. Component (1) according to claim 1, wherein the alloy is formed from a tin-nickel alloy having a nickel content in the range of 20 to 35 wt.%.

3. Component (1) according to claim 1, wherein the alloy consists of a copper-tin alloy or a tin-silver alloy or a tin-zinc alloy or a tin-bismuth alloy or a tin-antimony alloy or a tin-cobalt alloy or a nickel-tungsten alloy or a tin-manganese alloy or a tin-tantalum alloy or a tin-niobium alloy or a tin-nickel alloy. niobium alloy or a tin-nickel-tantalum alloy or a tin-tantalum-niobium alloy.

4. Component (1) according to one of claims 1 to 3, wherein the non-metallic particles comprise a proportion of electrically conductive particles which are formed from at least one material from the group comprising carbon, graphite, carbon nanotubes, carbon fibers, soot, graphene, graphene oxide, metal nitride, metal carbide.

5. The component of claim 4, wherein the non-metallic particles further comprise a proportion of particles formed from at least one material selected from the group consisting of metal sulfide, diamond, metal oxide, mica, PTFE.

6. Component (1) according to one of claims 1 to 5, wherein the metal substrate (2) is formed from a material from the group comprising stainless steel, titanium, a titanium alloy, aluminum, an aluminum alloy, an alloy containing predominantly tin, and the first layer (3a) is present.

7. Component (1) according to one of claims 1 to 5, wherein the metal substrate (2) is formed from a material from the group comprising copper, a copper alloy, nickel, a nickel alloy, low-alloy carbon steel, and no first layer (3a) is present.

8. Component (1) according to one of claims 1 to 7, wherein the first layer (3a) has a layer thickness of up to 5 pm and/or wherein the at least one second layer (3b) has a layer thickness of up to 30 pm and/or the cover layer (33) has a layer thickness in the range of 1 nm to 1 pm.

9. Component (1) according to one of claims 1 to 8, wherein the cover layer (33) in case a) is formed by a metal carbide containing at least one of the metals from the group comprising tungsten, cobalt, chromium, nickel, or by a doped amorphous carbon layer containing at least one doping element from the group comprising titanium, niobium, zirconium, hafnium, molybdenum, copper, silicon, tungsten, tantalum, platinum, palladium, ruthenium, silver, indium, boron, nitrogen, phosphorus, fluorine, hydrogen, oxygen, or by a metal nitride in the form of silicon nitride or a silicon nitride doped with boron and carbon.

10. Component (1) according to one of claims 1 to 8, wherein the cover layer (33) in case b) is formed from a perfluorinated organic compound.

11. Component (1) according to one of claims 1 to 10 in the form of an electrode for a redox flow cell (8), wherein the layer system (3) covers the metal substrate (2) at least in a contact region with an electrolyte of the redox flow cell (8).

12. Redox flow cell (8), in particular redox flow battery, comprising at least one electrode according to claim 11 and at least one electrolyte, in particular with a pH value in the range from -1 to 14.

13. Redox flow cell (8) according to claim 12, comprising at least two electrodes, a first reaction chamber (10a) and a second reaction chamber (10b), wherein each reaction chamber (10a, 10b) is in contact with one of the electrodes and wherein the reaction chambers (10a, 10b) are separated from one another by an ion exchange membrane (9a).

14. Fuel cell (90) comprising at least one component (1) according to one of claims 1 to 9 in the form of a bipolar plate and at least one polymer electrolyte membrane (9).

15. Electrolyzer, in particular for the electrolysis of water, comprising at least one component according to one of claims 1 to 10 in the form of a bipolar plate or a fluid diffusion layer (22a, 22b) and at least one polymer electrolyte membrane (9).