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

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

[0001] Component for an electrochemical cell, as well as redox flow cell, fuel cell and electrolyzer

[0002] 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 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. The invention further relates to electrochemical cells in the form of redox flow cells, electrolyzers and fuel cells.

[0003] 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 hydrogen production costs through electrolyzers comprising a polymer electrolyte membrane (PEM-EL) and reducing the manufacturing costs of the components of a fuel cell comprising a polymer electrolyte membrane (PEM-FC) are fundamental prerequisites 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 manufacturing process of the bipolar plates contribute a significant portion to the manufacturing costs of the respective stacks. The key 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 interfacial resistances. Titanium and stainless steel plates represent the state of the art in electrolysis. While the 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 across a broad pH range from 1 to 7. On the cathode side, titanium proves to be disadvantageous due to its tendency towards hydrogen embrittlement. Furthermore, an increase in ohmic losses due to surface passivation is observed during operation of electrolyzer stacks with titanium plates.In this context, the use of niobium, platinum, or gold coatings on titanium plates is well known. The extensive use of stainless steel to form a bipolar plate requires the use of an electrochemically stable, conductive, and, above all, dense, impermeable coating. In particular, impermeability to aqueous electrolytes must be achieved.

[0004] With PEM fuel cells, the available potential windows are more moderate, and the pH range is largely limited to 3. However, local operating conditions can occur within the cell that can lead to potentials >1.4 V NHE (normal hydrogen electrode). This requires the use of precious metal-containing layers 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 (a generally accepted target of the US Department of Energy for 2025).

[0005] WO 2023 274 441 A1 , which probably represents the closest prior art, describes in part components and electrochemical cells of the type mentioned above.

[0006] 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. One exemplary embodiment is a stainless steel substrate with an island-shaped intermediate layer of NiP and an electrochemically applied film of TiN-dispersed NiSn2 thereon. 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 of tin or a tin alloy. The first layer can contain a conductive filler, particularly in the form of carbon.

[0007] US 2019 / 0 148 741 A1 describes an electrochemical device such as a fuel cell, a battery, an electrolyzer, or a 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 has a coating of tin or a tin alloy, such as a tin-nickel alloy, a tin-antimony alloy, or a tin-nickel-antimony alloy, as well as 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. 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 significant challenges for the individual components of a battery stack. A new approach here is a metallic electrode with a structured geometry, which ensures a homogeneous distribution of an electrolyte in the active area while simultaneously allowing close separation from the membrane. On the other hand, metallic electrodes require appropriate surface properties that meet the high requirements for electrochemical stability, low interfacial resistance, and catalytic activity.

[0008] 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 to both sides, which is applied either dry-pressed or wet-chemically, are often used as electrodes. This results in a total electrode thickness of ~0.7–1.2 mm. With metallic plates, thicknesses of <0.5 mm can be achieved in large-area dimensions. It is also assumed that the processability of large-area metallic plates is more favorable than injection-molded plastic frames with graphite-based electrodes.

[0009] 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 approximately 0.5–0.6 mm) are typically used as planar plates made of pure graphite or a graphite-polymer compound. Bipolar plates made of polypropylene filled with graphite or carbon nanotubes, for example, are characterized by high corrosion resistance and high overpotentials for the hydrogen evolution reaction (HER).

[0010] 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.

[0011] In the PEM-EL, PEM-FC, and redox flow cell applications, electrically conductive, dense coatings are required. These serve as a barrier layer and can be enhanced in terms of performance, particularly catalytic effectiveness, by additional layers applied to them. The requirements can be summarized as follows: Electrochemical stability: pH range: 1-14

[0012] Potential range: -1 V NHE to +3 V NHE (short-term: -2 V NHE to +3 V NHE)

[0013] Running time: > 10000 h

[0014] Interfacial resistance:

[0015] < 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 that 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.

[0016] 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) formed from at least one self-organizing organic monolayer or at least one polymer.

[0017] 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 up to 10 mQcm 2 on.

[0018] Such components exhibit excellent electrochemical stability, as required in electrochemical cells. Due to their 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 fluid diffusion layers in electrolyzers. The presence of non-metallic particles embedded in the alloy in the second layer improves the mechanical stability of the layer system and, depending on the material of the particles used, also enables a further reduction in interfacial resistance and thus an increase in the efficiency of the electrochemical cell.

[0019] Preferably, the surface of the second layer is oxidized. In particular, only the surface atoms of the second layer are oxidized, thus activating the second layer for a strong bond to the top layer. The surface of the second layer is preferably oxidized by exposing it to an oxygen plasma. The oxygen plasma creates a dense and compact oxide layer on the surface of the second layer. However, oxidation of the surface of the second layer through anodization is also possible.

[0020] 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.

[0021] 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.

[0022] 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, O, where 0 < X ​​< 20 at.%. In particular, the amorphous carbon layer is formed in the form of a tetrahedral amorphous carbon layer of the ta-C:X type 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, O, where 0 < X ​​< 20 at.%. According to case a), the cover layer is preferably formed using a PVD or CVD process.

[0023] According to case b), in a further preferred embodiment, the cover layer is formed from at least one self-assembling organic monolayer, which is formed in particular from a fatty acid derivative or alkylphosphonic acid derivative with a chain length of 5 to 30 carbon atoms. Both the fatty acid derivative and the alkylphosphonic acid derivative can preferably be present with perfluorinated alkyl chains or partially fluorinated alkyl chains, or with completely unsubstituted alkyl chains.

[0024] 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).

[0025] According to case b), the cover layer is preferably formed using a spraying or doctor blade application process. Alternatively, the cover layer in case b) can also be formed using a spin-casting or dipping process.

[0026] The materials tin and nickel have proven to be thermodynamically stable over a broad pH range due to the formation of oxides. Therefore, a tin-nickel alloy with a nickel content in the range of 20 to 35 wt.% is particularly preferred. Such a low nickel content is highly advantageous in terms of reduced nickel diffusion into the membrane of an electrochemical cell, as it minimizes or prevents nickel poisoning of the membrane and thus effectively prevents a decrease in cell performance. As a result, second layers made of such a tin-nickel alloy with dispersed electrically conductive particles, in particular of carbon and / or graphite and / or carbon nanotubes and / or carbon fibers and / or carbon black and / or graphene and / or graphene oxide, have proven to be more stable over the long term than comparable gold layers.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. Particularly preferred among these are the tin-tantalum alloy, a tin-niobium alloy, a tin-nickel-niobium alloy, a tin-nickel-tantalum alloy, or a tin-tantalum-niobium alloy.

[0027] In particular, SnCu has proven to be a high-performance material composition in the redox flow cell when using alkaline electrolytes.

[0028] The first layer is made of copper or nickel. This ensures good adhesion of the coating system to the metal substrate.

[0029] 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 formed in particular from at least one material from the group comprising carbon, graphite, carbon nanotubes, carbon fibers, soot, graphene, graphene oxide, metal nitride, metal carbide.

[0030] 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 electrical contact between the membrane of the electrochemical cell and the electrical contacts outside the electrochemical cell, even under highly corrosive conditions.

[0031] Particularly preferred is a combination of a tin-nickel alloy with a nickel content in the range of 20 to 35 wt.% with dispersed non-metallic particles of at least one material from the group comprising carbon, graphite, carbon nanotubes, carbon fibers, carbon black, graphene, and graphene oxide. This alloy forms an oxide layer on its surface as a passivation, which has a particularly corrosion-inhibiting effect and increases the long-term stability of the electrochemical cell.

[0032] 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.

[0033] Preferred metal oxides are Al2O3, BeO2, CdO, MgO, SiO2, TiO2, ZrO2, Fe oxides, and the like. Preferred metal carbides are SiC, WC, VC, TiC, Cr2Cs, CrsO2, and the like. Preferred metal nitrides are BN or SiN and the like. Carbon in the form of graphite, carbon nanotubes, carbon fibers, carbon black, graphene, or graphene oxide is particularly preferred. Preferred metal sulfides are MoS2, MoS, NiFeS2, and the like.

[0034] 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, which are particularly stable and dispersible in an electrolyte for the electrodeposition 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, thus ensuring contact with a membrane.

[0035] 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.

[0036] The metal substrate is preferably made of a material from the group comprising stainless steel, such as grades 1.4404 or DC04, as well as titanium, a titanium alloy, aluminum, an aluminum alloy, and an alloy containing predominantly tin. In this case, the first layer is preferably present to improve the adhesion of the layer system.

[0037] Alternatively, the metal substrate is made of a material from the group consisting of copper, a copper alloy, nickel, a nickel alloy, and 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 suitable low-alloy carbon steel.

[0038] 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 readily possible. This allows for the creation of electroplated, conductive, and resistant layers on metallic substrates, such as stainless steel, across a wide pH and potential range. 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.

[0039] A single second layer or several second layers can be applied on top of each other.

[0040] In particular, the electroplating process 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 brief current pulses generated during switching on increase the formation of nuclei for metal deposition, thus creating a basis for fine-grained deposits and luster. The chemical application of the coating system comprising the optional first layer and at least one second layer is understood to be autocatalytic deposition, with the deposited alloy itself catalyzing further deposition, so that the depositable layer thickness is not limited from a process perspective.

[0041] The metal substrate is preferably in the form of a metal sheet or metal foil with a thickness in the range of 0.05 to 1 mm. Furthermore, the metal sheet or metal foil can have embossed three-dimensional structures to enlarge the surface area and thus increase the contact area with a fluid in an electrochemical cell.

[0042] 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.

[0043] The cover layer preferably has a layer thickness in the range of 1 nm to 1 pm. 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 pm and is in particular in the range of 4 to 8 pm.

[0044] 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.

[0045] 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 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, wherein each reaction chamber is in contact with one of the electrodes and wherein the reaction chambers are separated from one another by an ion exchange membrane. A graphite felt can be arranged in each reaction chamber, which is arranged adjacent to the respective electrode.

[0046] To form a redox flow battery, preferably more than 10, in particular more than 50 redox flow cells are used that are electrically interconnected.

[0047] The following is an example of anolyte suitable for a redox flow cell or a redox flow battery:

[0048] 1.4 M 7,8-dihydroxyphenazine-2-sulfonic acid (DHPS) dissolved in 1 molar sodium hydroxide solution

[0049] The following is an example of a catholyte suitable for a redox flow cell or a redox flow battery:

[0050] 0.31 M potassium hexacyanoferrate(II) and 0.31 M potassium hexacyanoferrate(III) dissolved in 2 molar sodium hydroxide solution.

[0051] 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.

[0052] Another electrolyte (anolyte or catholyte) suitable for the redox flow cell is mentioned here as an example:

[0053] 1.6M VOSO4 or V2(SO4)3 dissolved in aqueous dilute sulfuric acid (pH < 1).

[0054] 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 configured for the electrolysis of water.

[0055] The following examples are intended to illustrate a component according to the invention:

[0056] Example 1 :

[0057] Metal substrate: stainless steel electroplated first layer: copper or nickel electroplated second layer (DC, pulse plating):

[0058] Alloy: SnNi non-metallic particles: graphite

[0059] Oxidation of the free surface of the second layer, e.g. in oxygen plasma: Yes Top layer:

[0060] (12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 18-pentadecafluoro-octadecyl)-phosphonic acid

[0061] Example 2:

[0062] Metal substrate: Titanium electroplated first layer: Copper or nickel electroplated second layer (DC, Pulse Plating):

[0063] Alloy: SnAg non-metallic particles: titanium nitride and SiC

[0064] 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

[0065] Example 3:

[0066] Metal substrate: copper electroplated first layer: not applicable electroplated second layer (DC, Pulse Plating):

[0067] Alloy: SnCu non-metallic particles: Graphite and SiC Oxidation of the free surface of the second layer: No

[0068] Top layer: tungsten carbide

[0069] Metal substrate: Aluminium electroplated first layer: Copper or nickel electroplated second layer (DC, Pulse Plating):

[0070] Alloy: SnZn non-metallic particles: graphene oxide and SiO2

[0071] Oxidation of the free surface of the second layer, e.g. in oxygen plasma: Yes

[0072] Top layer: (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10- heptadecafluorodecyl)-carboxylic acid

[0073] Metal substrate: stainless steel Electroplated first layer: copper or nickel Electroplated second layer (DC, pulse plating): alloy: SnBi Non-metallic particles: graphene and WC

[0074] Oxidation of the free surface of the second layer: No

[0075] Top layer: PVDF

[0076] Metal substrate: Titanium electroplated first layer: Copper or nickel electroplated second layer (DC, Pulse Plating):

[0077] Alloy: SnSb or SnMn non-metallic particles: soot and mica

[0078] Oxidation of the free surface of the second layer: No

[0079] Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

[0080] Metal substrate: stainless steel electroplated first layer: copper or nickel electroplated second layer (DC, pulse plating):

[0081] Alloy: SnCo non-metallic particles: carbon nanotubes and MgO

[0082] Oxidation of the free surface of the second layer: No

[0083] Top layer: silicon nitride

[0084] Example 8:

[0085] Metal substrate: stainless steel electroplated first layer: copper or nickel electroplated second layer (DC, pulse plating):

[0086] Alloy: NiW non-metallic particles: graphite and M0S2

[0087] Oxidation of the free surface of the second layer: No

[0088] Cover layer: PTFE

[0089] Example 9:

[0090] Metal substrate: stainless steel electroplated first layer: copper or nickel electroplated second layer (DC, pulse plating):

[0091] Alloy: SnNi non-metallic particles: graphite and SiC

[0092] Oxidation of the free surface of the second layer: No

[0093] Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

[0094] Example 10:

[0095] Metal substrate: stainless steel galvanically or chemically produced first layer: copper or nickel autocatalytically (chemically) produced second layer:

[0096] Alloy: SnTa or SnNb non-metallic particles: graphite

[0097] Oxidation of the free surface of the second layer: Yes

[0098] Cover layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen) Example 11 :

[0099] 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

[0100] Oxidation of the free surface of the second layer: Yes

[0101] Top layer: ta-C:H (= tetrahedral amorphous carbon doped with hydrogen)

[0102] Figures 1 to 8 show examples of components and their use in electrochemical cells.

[0103] Figure 1 shows a component comprising a metal substrate and a layer system;

[0104] Figure 2 shows the component according to Figure 1 in cross-section;

[0105] Figure 3 shows another component with three-dimensional structuring in side view;

[0106] Figure 4 shows a component with an integral metal substrate and first layer;

[0107] Figure 5 shows a component in the form of an electrode with a three-dimensionally structured flow field;

[0108] Figure 6 shows a redox flow cell or a redox flow battery with a redox flow cell,

[0109] Figure 7 shows an electrolyzer in cross-section and

[0110] Figure 8 shows a fuel cell stack in a three-dimensional view.

[0111] 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.

[0112] Figure 2 shows the component 1 according to Figure 1 in sectional view II-II. The same reference numerals as in Figure 1 denote 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 galvanically coated on both sides with a first layer 3a of nickel with a layer thickness of 1 pm. On each of the first layer 3 there is a galvanically applied second layer 3b made of a tin-nickel alloy containing non-metallic graphite particles 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 comprising the first layer 3a and the second layer 3b there is a cover layer 33 made of PTFE with a layer thickness of 5 nm.

[0113] Figure 3 shows a side view of another component 1' with 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.

[0114] 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 formed thereon by electroplating 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 is a cover layer 33 made of silicon nitride in a layer thickness of 0.1 pm.

[0115] 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, a three-dimensional structuring 5 is present for forming a flow field 7 in each case, so that an enlargement of the surface of the electrode results, which is to be flowed against by an electrolyte in a redox flow cell 8 (see Figure 6).

[0116] 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 of the electrodes, not visible here (see Figure 5), are oriented towards an ion exchange membrane 9a and, if present, the respective graphite felt. The reaction chambers 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, wherein the graphite felt can be flowed through by electrolyte liquid.In the area of ​​a structured surface of the electrode, the electrolyte can partially flow past the graphite felt and continue through it. A liquid anolyte 11a is pumped from a tank 13a via a pump 12a into the first reaction chamber 10a 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, with electrical energy being released at the electrodes due to the redox reaction.

[0117] 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. 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, at least on their sides facing the fluid diffusion layers 22a, 22b, a galvanically applied layer system 3 and a cover layer 33 (see Figure 2).The plates each further comprise a three-dimensional structure 5, which forms flow channels 23a, 23b on the sides of the plates facing the fluid diffusion layers 22a, 22b, in order to improve the supply of reaction medium (water) and the removal of reaction products (water, hydrogen, oxygen). Figure 8 schematically shows 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 comprises 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 further has a gas distribution structure 6 on each side, which is designed to engage the polymer electrolyte membrane 9.

[0118] Figures 1 to 8 are intended to illustrate the invention merely by way of example. However, the inventive concept encompasses further electrochemical cells with at least one component designed according to the invention.

[0119] List of reference symbols

[0120] 1 , r, 1", 1a, 1 b, 1c, 1d, 1e, 1f component

[0121] 2 Metal substrate

[0122] 3 shift system

[0123] 3a first layer

[0124] 3b second layer

[0125] 33 Top layer

[0126] 4a, 4b surface

[0127] 5 three-dimensional structuring

[0128] 6 Gas distribution structure

[0129] 7 River field

[0130] 8 Redox flow cell

[0131] 9 polymer electrolyte membranes

[0132] 9a ion exchange membrane

[0133] 10a first reaction chamber

[0134] 10b second reaction chamber

[0135] 11a Anolyte

[0136] 11 b Catholyte

[0137] 12a, 12b pump

[0138] 13a, 13b Tank

[0139] 20 electrolysis cell

[0140] 21a, 21b Catalyst layer

[0141] 22a, 22b Fluid diffusion layer

[0142] 23a, 23b flow channels

[0143] 80a, 80b openings

[0144] 90 fuel cell

[0145] 100 fuel cell stacks

[0146] A anode side

[0147] K Cathode side

Claims

Patent claims 1. A component (1) of an electrochemical cell (10), comprising a metal substrate (2) and a layer system (3) applied at least partially galvanically and / or chemically 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), 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 of the at least one second layer (3b) of the layer system (3) facing away from the metal substrate (2),which is optionally 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 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 according to 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 from 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 area 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).

Images