Component for electrochemical cell, and redox flow cell, fuel cell and electrolytic cell

Abstract

The invention relates to a component (1) of an electrochemical cell (10), comprising a metal substrate (2) and a layer system (3) which is galvanically and / or chemically applied at least partially to the metal substrate (2), 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), and 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 present in the alloy in a bonded manner. On the free side of at least one second layer (3b) of the layer system (3) facing away from the metal substrate (2), which free side is optionally oxidized, a cover layer (33) is formed either a) from a metal carbide or metal nitride or amorphous carbon or b) from at least one self-organizing organic monolayer or at least one polymer.

Description

Technical Field

[0001] The present invention relates to a component of an electrochemical cell, comprising a metal substrate and a layer system at least partially applied to the metal substrate by electroplating 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 elements from the group consisting of tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum, and niobium, wherein non-metallic particles, including electrically conductive particles, are present in the alloy in a bonded manner. The present invention also relates to an electrochemical cell, an electrolysis cell, and a fuel cell in the form of a redox flow cell. Background Art

[0002] Hydrogen is an important raw material for key future technologies in energy storage and energy conversion. Water electrolysis is based on the decomposition of water into its component gases, hydrogen (H2) and oxygen (O2). Hydrogen-operated fuel cells generate electricity from hydrogen. Reducing the costs of producing hydrogen through electrolyzers containing polymer electrolyte membranes (PEM-EL) and reducing the costs of manufacturing the components of polymer electrolyte membrane fuel cells (PEM-BZ) are essential prerequisites for the efficient future use of these systems. The main components of a PEM electrolyzer stack / PEM fuel cell stack are bipolar plates (BiP), current collectors or fluid diffusion layers, and membrane electrode units (MEAs). The material and production of the bipolar plates contribute a significant portion to the manufacturing costs of the corresponding stack. In both application areas, the main requirements for components such as the bipolar plates and fluid diffusion layers are high corrosion resistance combined with low substrate and interface resistances.

[0003] In electrolysis, titanium plates and stainless steel plates form the prior art. The field of use of stainless steel plates is limited to a pH range of around 7 on the anode side due to the high applied oxidation potential, while titanium plates can be used over a wide pH range of 1 to 7. On the cathode side, titanium has proven to be disadvantageous because it tends to hydrogen embrittlement. In addition, during the operation of electrolyzer stacks with titanium plates, an increase in ohmic losses due to surface passivation is observed. Against this background, the use of niobium, platinum or gold coatings of titanium plates is known. The comprehensive use of stainless steel to form bipolar plates requires the use of an electrochemically stable, electrically conductive and, in particular, tight, impenetrable coating. In particular, sealing relative to aqueous electrolytes should be achieved.

[0004] In PEM-BZ, the potential window is relatively modest, and the pH range is largely limited to 3. However, local operating conditions may occur in the cell that may lead to potentials >1.4 V NHE (standard hydrogen electrode). This requires the use of noble metal-containing layers, such as Ir, Ru, or Au, which, despite layer thicknesses in the nm range, have material costs above the target cost range of $3 / kW for bipolar plates (the generally accepted target set by the U.S. Department of Energy for 2025).

[0005] WO 2023 274 441 A1, which probably constitutes the closest prior art, partially describes components and electrochemical cells of the type mentioned at the outset.

[0006] EP 3 336 942 A1 describes a metal plate for forming a separator for a polymer electrolyte fuel cell. The metal substrate has a membrane coating the surface of the substrate, with an island-shaped intermediate layer present between the substrate and the membrane. The intermediate layer contains at least one element from the group consisting of nickel, copper, silver, and gold, or is formed from a NiP alloy. As an example, a substrate composed of stainless steel is described: the stainless steel has an island-shaped intermediate layer composed of NiP and a membrane composed of TiN-dispersed Ni3Sn2 applied thereto electrochemically.

[0007] JP 2010-272 429 A discloses a separator for a fuel cell having a substrate made of copper or a copper alloy, which is coated with at least one first layer formed wet-chemically and made of tin or a tin alloy. The first layer may contain an electrically conductive filler material, in particular a filler material in the form of carbon.

[0008] US2019 / 0 148 741A1 describes an electrochemical device, such as a fuel cell, battery, electrolyzer, or redox flow battery, comprising a coated component having a substrate preferably made of a metal such as copper, iron, titanium, aluminum, nickel, or stainless steel. The substrate comprises a coating composed of tin or a tin alloy, such as a tin-nickel alloy, a tin-antimony alloy, or a tin-nickel-antimony alloy, and a conductive coating comprising a carbon-based material and a corrosion inhibitor containing pyrrole. Furthermore, flow battery systems as storage systems can utilize renewable energy sources to achieve a sustainable energy supply for stationary and mobile applications. To achieve high efficiency and power density, the goal is to create a battery stack that is as compact as possible. However, high power density poses significant challenges to the individual components of the battery stack. Metal electrodes with structured geometries are a novel approach to ensure uniform electrolyte distribution in the active area while simultaneously enabling a small distance from the membrane. Furthermore, the metal electrodes must meet the high demands for electrochemical stability, low interfacial resistance, and catalytic activity, requiring corresponding surface properties.

[0009] In redox flow cells, composite plates consisting of plastic and graphite (thickness -0.5-0.6 mm) with a carbon black active coating applied on both sides (thickness -0.1-0.3 mm) are usually used as electrodes. The carbon black active coating is applied by dry pressing or wet chemically. This results in a total plate thickness of -0.7-1.2 mm for the electrode. In large-area sizes, thicknesses of <0.5 mm can be achieved with metal plates. It can also be assumed that the processability of large-area metal plates leads to more favorable results compared to injection-molded plastic frames with graphite-based electrodes.

[0010] Another cell configuration, such as in an all-vanadium redox flow cell, consists of two bipolar plates in the form of two electrodes, typically with graphite felt to increase the active surface area, and a membrane. The electrolyte consists of vanadium dissolved in sulfuric acid (pH <1). The bipolar plates (thickness of approximately 0.5 mm to 0.6 mm) are typically used as flat plates made of pure graphite or graphite polymer compounds. Thus, bipolar plates made of polypropylene filled with graphite or carbon nanotubes are characterized by high corrosion resistance and a high overvoltage for the hydrogen evolution reaction (HER).

[0011] Compared to bipolar plates composed of graphite composite materials, 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 lower ohmic losses.

[0012] In the applications of PEM-EL, PEM-BZ, and redox flow cells, electrically conductive, dense coatings are required. These coatings function as barrier layers and can be enhanced in terms of their properties, especially their catalytic effect, by additional layers applied thereto. The requirements can be summarized as follows:

[0013] Electrochemical stability:

[0014] pH range: 1-14

[0015] Potential range: -1V NHE to +3V NHE (short time: -2V NHE to +3V NHE)

[0016] Running time: >10000h

[0017] Interface resistance:

[0018] <10mOhm cm 2 (at 100N / cm 2 contact pressure). Summary of the Invention

[0019] The object of the present invention is to provide a component for an electrochemical cell which meets the aforementioned requirements for electrochemical stability and low interfacial resistance in an improved form. Furthermore, the object of the present invention is to provide an electrochemical cell in the form of a redox flow cell, an electrolyzer, or a fuel cell having such a component.

[0020] A component for an electrochemical cell, comprising a metal substrate and a layer system applied at least partially to the metal substrate by electroplating 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 including electrically conductive particles are present in the alloy in a bonded manner, the object being achieved in that a covering layer is formed on the free side of the at least one second layer of the layer system facing away from the metal substrate, the free side being optionally treated and oxidized with oxygen plasma, the covering layer either

[0021] a) is formed from a metal carbide or metal nitride or amorphous carbon, or

[0022] b) is formed from at least one self-organized organic monolayer or at least one polymer.

[0023] Here, the conductive particles have a thermal conductivity of 0.25 mΩcm in a temperature range of 20°C to 25°C.2 To 10 mΩcm 2 Conductivity within the range of

[0024] Such a component has excellent electrochemical stability as required in an electrochemical cell. Due to the additionally low interfacial resistance, such a component is particularly suitable for forming electrodes of redox flow cells, forming bipolar plates for fuel cells and electrolyzers, and forming fluid diffusion layers of electrolyzers. The presence of non-metallic particles present in the second layer in a manner incorporated into the alloy improves the mechanical stability of the layer system and can also further reduce the interfacial resistance depending on the material of the particles used, thereby achieving an improvement in the efficiency of the electrochemical cell.

[0025] Preferably, the surface of the second layer is oxidized. In particular, only the surface atoms of the second layer are oxidized here, so that the second layer is activated for the firm attachment of the covering layer. Preferably, the surface of the second layer is oxidized in such a way that the surface is subjected to an oxygen plasma. The oxygen plasma ensures a dense and compact oxide layer on the surface of the second layer. However, it is also possible to oxidize the surface of the second layer by anodization.

[0026] According to case a), in a preferred embodiment, the covering layer is formed from a metal carbide of at least one metal from the group comprising tungsten, cobalt, chromium, nickel.

[0027] According to case a), in another preferred embodiment, the covering layer is formed from a metal nitride in the form of silicon nitride or silicon nitride doped with boron and carbon.

[0028] According to case a), in another preferred embodiment, the covering layer is formed from amorphous carbon (according to VDI guideline No. 2840, table 1 in 2012), which should include hydrogen-free and hydrogen-containing amorphous carbon layers provided with metallic and / or non-metallic doping elements. As doping element X, 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, O are considered, where 0 < X ≤ 20 atomic %. In particular, the amorphous carbon layer is composed of a tetrahedral amorphous carbon layer of the ta-C:X type having 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, O, where 0 < X ≤ 20 atomic %.

[0029] According to case a), the covering layer is preferably formed by a PVD or CVD method.

[0030] According to case b), in another preferred embodiment, the covering layer is formed by at least one self-organizing organic monolayer, which is formed in particular by fatty acid derivatives or alkylphosphonic acid derivatives having a chain length of 5 to 30 carbon atoms. Both the fatty acid derivatives and the alkylphosphonic acid derivatives can preferably be present as perfluoroalkyl chains, partially fluorinated alkyl chains, or completely unsubstituted alkyl chains.

[0031] According to case b), in a further preferred embodiment, the cover layer is formed from at least one polymer, in particular from a polymer having perfluorinated chains such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

[0032] According to case b), the cover layer is preferably formed by a spraying or doctor blade coating method. Alternatively, in case b), the cover layer can also be formed by a centrifugal casting method or an impregnation method.

[0033] The materials tin and nickel have been shown to be thermodynamically stable over a wide pH range due to the formation of oxides. Therefore, an alloy consisting of a tin-nickel alloy with a nickel content in the range of 20% to 35% by weight is particularly preferred. Such a low nickel content is very advantageous in terms of the reduced nickel diffusion into the membrane of the electrochemical cell, since this leads to minimizing or preventing nickel poisoning of the membrane, thereby effectively preventing a drop in the power of the cell. Thus, compared to a control layer consisting of gold, a second layer consisting of such a tin-nickel alloy with conductive particles dispersed therein has been shown to be more stable in the long term, the conductive particles being in particular composed of carbon and / or graphite and / or carbon nanotubes and / or carbon fibers and / or carbon black and / or graphene and / or graphene oxide.

[0034] The alloy is alternatively formed from a copper-tin alloy, a tin-silver alloy, a tin-zinc alloy, a tin-bismuth alloy, a tin-antimony alloy, a tin-cobalt alloy, a nickel-tungsten alloy, a tin-manganese alloy, a tin-tantalum alloy, a tin-niobium alloy, a tin-nickel-niobium alloy, a tin-nickel-tantalum alloy, or a tin-tantalum-niobium alloy.

[0035] Among them, tin-tantalum alloy, tin-niobium alloy, tin-nickel-niobium alloy, tin-nickel-tantalum alloy, or tin-tantalum-niobium alloy is particularly preferred.

[0036] In particular, SnCu has been shown to be a high-performance material component in redox flow cells when using alkaline electrolytes.

[0037] The first layer is formed from copper or nickel. This ensures good adhesion of the layer system to the metal substrate.

[0038] The non-metallic particles preferably include a portion of conductive particles, which cause a significant reduction in interface resistance at the component and are particularly formed of at least one material from the group consisting of carbon, graphite, carbon nanotubes, carbon fibers, carbon black, graphene, graphene oxide, metal nitrides, and metal carbides.

[0039] The proportion of the electrically conductive particles is in particular greater than 50% of the non-metallic particles. It has been shown that the electrically conductive particles protruding from the second layer reliably maintain electrical contact between the membrane of the electrochemical cell and an electrical contact outside the electrochemical cell, even under highly corrosive conditions.

[0040] Particularly preferred is a combination of a tin-nickel alloy having a nickel content in the range of 20% to 35% by weight and non-metallic particles dispersed therein, consisting of at least one material from the group consisting of carbon, graphite, carbon nanotubes, carbon fibers, carbon black, graphene, and graphene oxide. The alloy forms an oxide layer on its surface as a passivation, which provides a particularly corrosion-resistant effect and increases the long-term stability of the electrochemical cell.

[0041] The non-metallic particles may also include a proportion of particles formed from a non-conductive material, such as at least one material from the group consisting of metal sulfides, metal oxides, diamond, mica, and PTFE.

[0042] Preferred metal oxides include Al2O3, BeO2, CdO, MgO, SiO2, TiO2, ZrO2, Fe oxide, and the like. Preferred metal carbides include SiC, WC, VC, TiC, Cr2C3, Cr3C2, and the like. Preferred metal nitrides include BN or SiN, and the like. Particularly preferred are carbon in the form of graphite, carbon nanotubes, carbon fibers, carbon black, graphene, or even graphene oxide. Preferred metal sulfides include MoS2, MoS, NiFeS2, and the like.

[0043] The preferred particle size of the non-metallic particles is in the range of 100 nm to 8 μm, in particular in the range of 500 nm to 6 μm. Particles in the nanometer range are particularly preferably used, as they can be dispersed particularly stably in the electrolyte for the electrolytic deposition of the second layer. In particular, the particle size is selected such that it protrudes from the surface of the at least one second layer, thereby ensuring contact with the membrane.

[0044] The preferred volume fraction of the non-metallic particles in the second layer is in the range of 2% to 50% by volume. This ensures a reliable bonding of the particles in the metal matrix.

[0045] The metal substrate is preferably formed from a material from the group comprising stainless steel such as type 1.4404 or DC04, titanium, titanium alloys, aluminum, aluminum alloys, alloys primarily containing tin. In said case, in order to improve the adhesion of the layer system, a first layer is preferably present.

[0046] Alternatively, the metal substrate is formed from a material selected from the group consisting of copper, copper alloys, nickel, nickel alloys, and low-alloy carbon steel. In particular, the metal substrate is formed from copper or nickel. In this case, the first layer can also be omitted. 100Cr6 has proven to be suitable as a low-alloy carbon steel.

[0047] The optional first layer and at least one second layer are formed by electroplating and / or chemical deposition. Electroplating methods make it easy to deposit electrolyte-dense layers with layer thicknesses >10 microns for use in PEM-EL and redox flow cells. This allows for electroplated conductive and resistant layers on metal substrates, such as stainless steel, over a wide range of pH and potential windows. Non-metallic particles are dispersed in the electrolyte to form the second layer and, when the at least one second layer is formed, are incorporated into the alloy deposited on the first layer.

[0048] A single second layer can be applied or a plurality of second layers can be applied one above the other.

[0049] Electroplating is typically performed using the so-called pulse plating method, in which the voltage applied to the electrolyte is periodically switched off or reversed in polarity. The temporary current pulses generated during the on-state phase create more nuclei for metal deposition, thus creating the basis for fine-grained deposition and gloss.

[0050] Chemically applying a layer system comprising an optional first layer and at least one second layer is understood to be an autocatalytic deposition, in which the deposited alloy itself catalyzes further deposition, so that from a process perspective, the depositable layer thickness is unlimited.

[0051] The metal substrate is preferably in the form of a metal plate or metal film having a thickness in the range of 0.05 mm to 1 mm. Furthermore, the metal plate or metal film may have an embossed three-dimensional structure in order to increase the surface area and thus the contact area with the fluid in the electrochemical cell.

[0052] The first layer preferably has a layer thickness of up to 5 μm, in particular in the range of up to 3 μm. The at least one second layer preferably has a layer thickness of up to 30 μm, in particular in the range of 5 μm to 20 μm.

[0053] The cover layer preferably has a layer thickness in the range of 1 nm to 1 μm. In case b), the layer thickness of the cover layer is preferably in the range of 1 nm to 100 nm. The preferred total layer thickness of the layer system is <10 μm and in particular in the range of 4 μm to 8 μm.

[0054] The component according to the invention is preferably designed as an electrode for a redox flow cell, wherein the layer system covers the metal substrate at least in the contact region with the electrolyte of the redox flow cell and optionally also in the contact region with the graphite felt through which the electrolyte flows.

[0055] The object is also achieved for a redox flow cell, in particular a redox flow battery, comprising at least one electrode for a redox flow cell and at least one electrolyte, in particular having a pH value in the range of −1 to 14.

[0056] The redox flow cell preferably includes at least two electrodes, a first reaction chamber, and a second reaction chamber, wherein each reaction chamber contacts one of the electrodes and the reaction chambers are separated from each other by an ion exchange membrane. A graphite felt may be disposed in each reaction chamber, adjacent to the corresponding electrode.

[0057] Therefore, to construct a redox flow battery, preferably more than 10, in particular more than 50, redox flow cells are used in an electrically connected manner.

[0058] As anolytes suitable for redox flow cells or redox flow batteries, the following are mentioned as examples:

[0059] 1.4M 7,8-dihydroxyphenazine-2-sulfonic acid (DHPS),

[0060] Dissolve in 1 molar sodium hydroxide solution.

[0061] As catholytes suitable for redox flow cells or redox flow batteries, the following are mentioned as examples:

[0062] 0.31M potassium ferrocyanide and 0.31M potassium ferrocyanide,

[0063] Dissolve in 2 molar sodium hydroxide solution.

[0064] An electrolyte combination having an aqueous electrolyte on the anolyte side with redox-active organic and / or metallic species is preferably used to form a redox flow cell or redox flow battery.

[0065] As further electrolytes (anolyte or catholyte) suitable for redox flow cells, the following are mentioned by way of example:

[0066] 1.6M VOSO4 or V2(SO4)3, dissolved in aqueous dilute sulfuric acid (pH <1).

[0067] The object is also achieved by 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.

[0068] Finally, the object is achieved by an electrolysis cell 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 electrolysis cell is preferably configured for the electrolysis of water.

[0069] The following examples are intended to illustrate the components according to the present invention:

[0070] Example 1:

[0071] Metal substrate: stainless steel

[0072] First layer produced by electroplating: copper or nickel

[0073] Second layer produced by electroplating (DC, pulse plating):

[0074] Alloy: SnNi

[0075] Non-metallic particles: graphite

[0076] Is the free surface of the second layer oxidized, for example in oxygen plasma: Yes

[0077] Covering:

[0078] (12,12,13,13,14,14,15,15,16,16,17,17,18,18,18-pentadecafluorooctadecyl)phosphonic acid Example 2：

[0079] Metal substrate: titanium

[0080] First layer produced by electroplating: copper or nickel

[0081] Second layer produced by electroplating (DC, pulse plating):

[0082] Alloy: SnAg

[0083] Non-metallic particles: titanium nitride and SiC

[0084] Is the free surface of the second layer oxidized, for example in oxygen plasma: Yes

[0085] Covering layer: (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro)decylphosphonic acid

[0086] Example 3:

[0087] Metal substrate: copper

[0088] First layer produced by electroplating: Cancel

[0089] Second layer produced by electroplating (DC, pulse plating):

[0090] Alloy: SnCu

[0091] Non-metallic particles: graphite and SiC

[0092] Is the free surface of the second layer oxidized: No

[0093] Covering: Tungsten Carbide

[0094] Example 4:

[0095] Metal substrate: aluminum

[0096] First layer produced by electroplating: copper or nickel

[0097] Second layer produced by electroplating (DC, pulse plating):

[0098] Alloy: SnZn

[0099] Non-metallic particles: graphite oxide and SiO2

[0100] Is the free surface of the second layer oxidized, for example in oxygen plasma: Yes

[0101] Covering layer: (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)carboxylic acid

[0102] Example 5:

[0103] Metal substrate: stainless steel

[0104] First layer produced by electroplating: copper or nickel

[0105] Second layer produced by electroplating (DC, pulse plating):

[0106] Alloy: SnBi

[0107] Non-metallic particles: graphene and WC

[0108] Is the free surface of the second layer oxidized: No

[0109] Covering layer: PVDF

[0110] Example 6:

[0111] Metal substrate: titanium

[0112] First layer produced by electroplating: copper or nickel

[0113] Second layer produced by electroplating (DC, pulse plating):

[0114] Alloy: SnSb or SnMn

[0115] Non-metallic particles: carbon black and mica

[0116] Is the free surface of the second layer oxidized: No

[0117] Capping layer: ta-C:H (=tetrahedral amorphous carbon doped with hydrogen)

[0118] Example 7:

[0119] Metal substrate: stainless steel

[0120] First layer produced by electroplating: copper or nickel

[0121] Second layer produced by electroplating (DC, pulse plating):

[0122] Alloy: SnCo

[0123] Non-metallic particles: carbon nanotubes and MgO

[0124] Is the free surface of the second layer oxidized: No

[0125] Covering layer: Silicon nitride

[0126] Example 8:

[0127] Metal substrate: stainless steel

[0128] First layer produced by electroplating: copper or nickel

[0129] Second layer produced by electroplating (DC, pulse plating):

[0130] Alloy: NiW

[0131] Non-metallic particles: graphite and MoS2

[0132] Is the free surface of the second layer oxidized: No

[0133] Cover: PTFE

[0134] Example 9:

[0135] Metal substrate: stainless steel

[0136] First layer produced by electroplating: copper or nickel

[0137] Second layer produced by electroplating (DC, pulse plating):

[0138] Alloy: SnNi

[0139] Non-metallic particles: graphite and SiC

[0140] Is the free surface of the second layer oxidized: No

[0141] Capping layer: ta-C:H (=tetrahedral amorphous carbon doped with hydrogen)

[0142] Example 10:

[0143] Metal substrate: stainless steel

[0144] Electroplated or chemically produced first layer: copper or nickel

[0145] The second layer is generated by autocatalysis (chemically):

[0146] Alloy: SnTa or nNb

[0147] Non-metallic particles: graphite

[0148] Is the free surface of the second layer oxidized: Yes

[0149] Capping layer: ta-C:H (=tetrahedral amorphous carbon doped with hydrogen)

[0150] Example 11:

[0151] Metal substrate: stainless steel

[0152] Electroplated or chemically produced first layer: copper or nickel

[0153] The second layer is generated by autocatalysis (chemically):

[0154] Alloy: SnNiNb or SnNbTa or SnNiTa

[0155] Non-metallic particles: graphite

[0156] Is the free surface of the second layer oxidized: Yes

[0157] Capping layer: ta-C:H (=tetrahedral amorphous carbon doped with hydrogen) BRIEF DESCRIPTION OF THE DRAWINGS

[0158] Figures 1 to 8 The components and their use in an electrochemical cell are shown by way of example. Thus, the following are shown:

[0159] Figure 1 A component comprising a metal substrate and a layer system is shown;

[0160] Figure 2 In the cross-sectional view, the Figure 1 components;

[0161] Figure 3 Another component with a three-dimensional structuring is shown in a side view;

[0162] Figure 4 A component is shown having an integral metal substrate and a first layer;

[0163] Figure 5 A component in the form of an electrode with a three-dimensionally structured flow field is shown;

[0164] Figure 6 A redox flow cell or a redox flow battery having a redox flow cell is shown;

[0165] Figure 7 The electrolytic cell is shown in cross section,

[0166] Figure 8 The fuel cell stack is shown in a three-dimensional illustration. DETAILED DESCRIPTION

[0167] Figure 1 A component 1 is shown in a plan view onto a surface 4a, comprising a metallic substrate 2 and a layer system 3 (see Figure 2 ) and a covering layer 33.

[0168] Figure 2 The cross-sectional view II-II shows the Figure 1 Component 1. Figure 1 Identical reference numerals denote identical elements. A metal substrate 2 can now be seen, in the form of a metal plate, here composed, for example, of stainless steel. The metal plate is electroplated on both sides with a first layer 3a of nickel having a layer thickness of 1 μm. A second layer 3b of a tin-nickel alloy, applied electroplatically and having a layer thickness in the range of 5 μm, is located on the first layer 3. The second layer contains non-metallic particles of graphite. The surface 4b of the second layer 3a is treated and oxidized in an oxygen plasma. A covering layer 33 of PTFE having a layer thickness of 5 nm is located on the layer system 3 consisting of the first layer 3a and the second layer 3b.

[0169] Figure 3A further component 1 ′ is shown in a side view with a three-dimensional structuring 5 . 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 .

[0170] Figure 4 Component 1″ is shown in cross section and comprises a metallic substrate 2 composed of nickel. Metallic substrate 2 simultaneously forms first layer 3a. A second layer 3b, formed thereon electroplated, consists of a tin-nickel alloy containing non-metallic particles of graphite and SiC with a layer thickness of 10 μm. A covering layer 33 composed of silicon nitride with a layer thickness of 0.1 μm is located thereon.

[0171] Figure 5 The three-dimensional view shows a component 1a in the form of an electrode, which comprises a metal substrate 2 in the form of a metal plate made of titanium, which is coated with a layer system 3 and a cover layer 33. In the metal substrate 2, there are three-dimensional structurings 5 for forming flow fields 7, respectively, resulting in an increase in the surface area of the electrode, which is to be used in a redox flow cell 8 (see Figure 6 ) is countered by the electrolyte.

[0172] Figure 6 A redox flow cell 8 or a redox flow battery having a redox flow cell 8 is shown. 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, wherein each reaction chamber 10a, 10b is in contact with one of the electrodes. A graphite felt may be arranged in the reaction chambers 10a, 10b, which is not shown separately here. The flow field 7 of the electrode (not visible here) Figure 5 ) is oriented toward the ion exchange membrane 9a and, if present, toward the corresponding graphite felt. The reaction chambers 10a, 10b are separated from each other by the ion exchange membrane 9a. If graphite felt is present, it is introduced at least slightly compressed between the corresponding electrode and the ion exchange membrane 9a, wherein the graphite felt can be flowed through by the electrolyte. In this case, the electrolyte can partially flow through the graphite felt in the area of the structured surface of the electrode and further flow through the graphite felt. The liquid anolyte 11a is pumped from the tank 13a via a pump 12a into the first reaction chamber 10a and guided between the component 1a and the ion exchange membrane 9a. The liquid catholyte 11b is pumped from the tank 13b via a pump 12b into the second reaction chamber 10b and guided between the component 1b and the ion exchange membrane 9a. The ion exchange takes place via the ion exchange membrane 9a, wherein electrical energy is released due to the redox reaction at the electrode.

[0173] Figure 7An electrolysis cell 20 of an electrolysis cell is shown, comprising a polymer electrolyte membrane 9 which separates the anode side A and the cathode side K from one another. Catalyst layers 21a, 21b are arranged on both sides of the polymer electrolyte membrane 9, each comprising a catalyst material and a fluid diffusion layer 22a, 22b consisting of titanium (on the anode side) and graphite felt (on the cathode side), which is adjacent to the catalyst layers 21a, 21b. The fluid diffusion layers 22a, 22b are arranged adjacent to components 1e, 1f in the form of electrically conductive plates. The plates are made of stainless steel and have, at least on their sides facing the fluid diffusion layers 22a, 22b, a layer system 3 applied by electroplating and a cover layer 33 (see FIG. Figure 2 The plates also each have a three-dimensional structure 5, which forms flow channels 23a, 23b on the sides of the plates facing the fluid diffusion layers 22a, 22b, respectively, in order to improve the input of the reaction medium (water) and the output of the reaction products (water, hydrogen, oxygen).

[0174] Figure 8 A fuel cell stack 100 is schematically shown, comprising a plurality of fuel cells 90. Each fuel cell 90 comprises a polymer electrolyte membrane 9, which is adjoined on both sides by components 1c, 1d in the form of bipolar plates. Each bipolar plate comprises a metal substrate 2 with a layer system 3 applied electroplatically and a cover layer 33 (see Figure 2 The bipolar plate has an inlet region with openings 80 a and an outlet region with further openings 80 b for supplying process gas and coolant to the fuel cells 90 and for removing reaction products and coolant from the fuel cells 90. The bipolar plate also has a gas distribution structure 6 on each side, which is designed to be in contact with the polymer electrolyte membrane 9.

[0175] Figures 1 to 8 The invention is to be explained merely by way of example. However, the inventive concept also encompasses further electrochemical cells having at least one component designed in the manner according to the invention.

[0176] Reference Signs List

[0177] 1, 1', 1", 1a, 1b, 1c, 1d, 1e, 1f components

[0178] 2 Metal substrate

[0179] 3-tier system

[0180] 3a First floor

[0181] 3b Second floor

[0182] 33 Covering

[0183] 4a, 4b surfaces

[0184] 5 Three-dimensional structured part

[0185] 6 Gas distribution structure

[0186] 7 Flow Field

[0187] 8 Redox flow battery cells

[0188] 9 Polymer electrolyte membrane

[0189] 9a Ion exchange membrane

[0190] 10a First reaction chamber

[0191] 10b Second reaction chamber

[0192] 11a Anolyte

[0193] 11b Catholyte

[0194] 12a, 12b pumps

[0195] 13a, 13b cans

[0196] 20 electrolytic cells

[0197] 21a, 21b catalyst layer

[0198] 22a, 22b fluid diffusion layer

[0199] 23a, 23b flow channel

[0200] 80a, 80b opening

[0201] 90 fuel cells

[0202] 100 fuel cell stack

[0203] A Anode side

[0204] K cathode side

Claims

1. A 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) by electroplating and / or chemical means, 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 elements from the group consisting of tin, copper, nickel, silver, zinc, bismuth, antimony, cobalt, manganese, tungsten, tantalum, niobium, wherein non-metallic particles, including electrically conductive particles, are present in the alloy in a bonded manner, It is characterized in that A covering layer (33) is formed on the free side of at least one second layer (3b) of the layer system (3) facing away from the metal substrate (2), the free side being optionally oxidized, the covering layer or a) is formed from a metal carbide or metal nitride or amorphous carbon, or b) is formed from at least one self-organized organic monolayer or at least one polymer.

2. The 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% by weight.

3. The component (1) according to claim 1, wherein the alloy is formed by a copper-tin alloy, a tin-silver alloy, a tin-zinc alloy, a tin-bismuth alloy, a tin-antimony alloy, a tin-cobalt alloy, a nickel-tungsten alloy, a tin-manganese alloy, a tin-tantalum alloy, a tin-niobium alloy, a tin-nickel-niobium alloy, a tin-nickel-tantalum alloy, or a tin-tantalum-niobium alloy.

4. The component (1) according to any one of claims 1 to 3, wherein the non-metallic particles include a proportion of the following electrically conductive particles: the electrically conductive particles are formed from at least one material from the group consisting of carbon, graphite, carbon nanotubes, carbon fibers, carbon black, graphene, graphene oxide, metal nitrides, and metal carbides. 5 . The component ( 1 ) according to claim 4 , wherein the non-metallic particles also include a proportion of particles formed from at least one material from the group consisting of metal sulfides, diamonds, metal oxides, mica, and PTFE.

6. The component (1) according to any one of claims 1 to 5, wherein the metal substrate (2) is composed of a material from the group consisting of stainless steel, titanium, titanium alloys, aluminum, aluminum alloys, alloys mainly containing tin, and the first layer (3a) is present.

7. The component (1) according to any one of claims 1 to 5, wherein the metal substrate (2) is formed of a material from the group consisting of copper, copper alloys, nickel, nickel alloys, low alloy carbon steel, and the first layer (3a) is absent.

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

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

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

11. A component (1) according to any 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 the contact area with the electrolyte of the redox flow cell (8).

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

13. The 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 each other by an ion exchange membrane (9a).

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

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

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