Cell for a cell stack for electrochemical energy conversion and production

Abstract

The invention relates to a cell (100) for a cell stack for electrochemical energy conversion. The cell (100) comprises at least one at least partially metallic plate (101, 109) and an at least partially metallic, gas-permeable pore structure (107), wherein the plate (101, 109) and / or the pore structure (107) are coated, at least in regions, with a coating material comprising tungsten oxide.

Description

[0001] The presented invention relates to a cell for a cell stack for electrochemical energy conversion, a bipolar plate, a gas diffusion layer and a manufacturing method according to the appended claims. State of the art

[0002] Electrochemical energy converters, such as PEM electrolyzers, often consist of a polymer membrane that is used for H + ions or in the case of AEM electrolyzers for OH - Ions are permeable, and two electrodes on the opposite side of the membrane.

[0003] In the case of an electrolyzer, an aqueous electrolyte is introduced into a chamber, e.g., on the oxygen-producing side, or anode side. The side opposite the membrane is optionally also perfused with an aqueous electrolyte, producing hydrogen.

[0004] The chamber is filled with a porous structure that provides electrical contact to the respective electrode and is permeable to aqueous electrolytes and gases. The chamber is sealed with a bipolar plate, so that a cell is confined as a repeating element in a cell stack of bipolar plates.

[0005] The bipolar plates are used in electrolyzers to couple in electrical current, which is required for the electrolysis of water into oxygen and hydrogen.

[0006] For reasons of electrochemical stability, porous structures and bipolar plates on the oxygen-forming side of electrolyzers must be metallic, especially in PEM electrolyzers made of titanium.

[0007] Since metals oxidize in an oxygen-rich environment, the required electrical contact resistance of the metallic elements in a given cell becomes too high, so that electrically highly conductive precious metal coatings such as gold and especially platinum must be used. Disclosure of the invention

[0008] Within the scope of the invention presented, a cell for a cell stack, a bipolar plate, a gas diffusion layer, and a manufacturing method for producing the cell are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the manufacturing method according to the invention naturally also apply in connection with the cell according to the invention, the bipolar plate according to the invention, or the gas diffusion layer according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0009] The invention presented serves in particular to provide a cost-effective and robust electrochemical energy converter.

[0010] Thus, according to a first aspect of the invention presented, a cell for a cell stack for electrochemically converting energy is presented.

[0011] The presented cell comprises at least one at least partially metallic plate and an at least partially metallic gas-permeable pore structure, wherein the plate and / or the pore structure is coated at least in regions with a coating material comprising tungsten oxide.

[0012] The invention is based on the principle that metallic components of the cell are coated with a coating material comprising tungsten oxide. Since tungsten oxide is particularly corrosion-resistant and oxidation-stable, it is particularly suitable for protecting metallic components in an electrochemical energy converter, such as an electrolyzer.

[0013] Accordingly, using the presented invention, coating cell components of an electrochemical energy converter with precious metals can be dispensed with or minimized. This means that the presented cell can be designed without precious metals or without a precious metal coating.

[0014] It can be provided that an adhesive layer is formed between the plate and the coating material, which adhesive layer comprises at least one metal or an alloy of the following metals: chromium, titanium, tungsten.

[0015] The adhesive layer can be applied during the coating process itself, for example. Suitable coating methods include (PA)PVD (plasma-assisted) physical vapor deposition, (PA)(MO)CVD (plasma-assisted)(metalorganic) chemical vapor deposition, ALD (atomic layer deposition), laser ablation coating, and wet chemical coating methods.

[0016] Metallic tungsten can be used as an adhesive layer because it adheres particularly well to smooth surfaces. The adhesive layer can be welded or sprayed onto the surface, for example.

[0017] It may be provided that the tungsten oxide comprises WO2, W2O5, WO3 or any other tungsten oxide and mixtures thereof.

[0018] It may further be provided that the plate is made of a material comprising steel and / or titanium.

[0019] In particular, plates made of a hard material, such as steel or titanium, can be coated particularly easily with the coating material provided according to the invention.

[0020] It can further be provided that the pore structure is part of a gas diffusion layer.

[0021] Since high electrical potentials are present particularly in the area of ​​a gas diffusion layer, coating the gas diffusion layer with a material comprising tungsten oxide has proven to be particularly advantageous for extending the service life of a cell stack.

[0022] According to a second aspect, the presented invention relates to a bipolar plate for a cell, in particular for a cell according to the first aspect of the invention, for a cell stack for electrochemically converting energy, wherein the bipolar plate is coated at least in regions with a coating material comprising tungsten oxide.

[0023] The bipolar plate presented is particularly intended for use in a cell, such as the cell presented.

[0024] By coating only parts of the bipolar plate that are particularly exposed to electrical and chemical stress, such as a flux field, material and costs can be saved.

[0025] It can be provided that an adhesive layer made of metallic tungsten is formed between a basic structure of the bipolar plate and the coating material.

[0026] An adhesive layer formed on the base structure of the bipolar plate, such as a steel block, enables the coating material to adhere securely to the bipolar plate.

[0027] According to a third aspect, the presented invention relates to a gas diffusion layer for a cell, in particular for a cell according to the first aspect of the invention, for a cell stack for electrochemically converting energy, wherein the gas diffusion layer is coated at least in regions with a coating material comprising tungsten oxide.

[0028] The presented gas diffusion layer is particularly intended for use in a cell, such as the cell presented.

[0029] According to a fourth aspect, the presented invention relates to a manufacturing method for a possible embodiment of the presented cell.

[0030] The presented manufacturing method comprises at least partially coating a metallic structure of the cell with a coating material comprising tungsten oxide, wherein the metallic structure comprises an at least partially metallic plate and / or an at least partially metallic gas-permeable pore structure.

[0031] In the context of the present invention, a coating process is understood to mean the application of a layer to a substrate. The layer can be bonded to the substrate thermally and / or chemically and / or physically, i.e., for example, mechanically interlocked at the microstructural level.

[0032] It may be provided that the manufacturing method further comprises pretreating the metallic structure by means of a cleaning solution and smoothing the coating material.

[0033] A pretreatment step in which a substrate, i.e. the metallic structure, is cleaned with a cleaning solution ensures optimal adhesion of the coating material to the metallic structure.

[0034] A smoothing step, in which a layer of coating material applied to the metallic structure is adjusted to a predetermined thickness, ensures a constant corrosion behavior of the metallic structure, so that local damage is minimized.

[0035] A welding process has proven to be a simple and robust method for coating metallic structures of the presented cell.

[0036] It may further be provided that the coating material is applied directly to the surface of the metallic structure by thermal spraying, in particular by high-speed flame jet spraying.

[0037] Advantages that are described in detail for the cell for a cell stack for electrochemically converting energy according to the first aspect of the invention and for the bipolar plate for a cell for a cell stack for electrochemically converting energy according to the second aspect of the invention apply equally to the gas diffusion layer for a cell for a cell stack for electrochemically converting energy according to the third aspect of the invention and to the manufacturing method for a possible embodiment of the presented cell according to the fourth aspect of the invention.

[0038] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0039] They show schematically: Fig. 1 a representation of a possible design of the presented cell, Fig. 2 a possible design of the presented manufacturing process, and Fig. 3 another possible design of the presented cell.

[0040] In Fig. 1 shows a cell 100. The cell 100 comprises a bipolar plate 101 and an at least partially metallic and gas-permeable pore structure 107.

[0041] The bipolar plate 101 borders on or encompasses a flow field 105.

[0042] The at least partially metallic and gas-permeable pore structure 107 is part of a gas diffusion layer, which additionally comprises an electrode 109 and borders a membrane 111. Alternatively, the electrode 109 can be configured as part of a CCM 103, which, in addition to the electrode 109, also comprises the membrane 111.

[0043] The structure of the cell 100 outlined above results in a first interface between the electrode 109 and the at least partially metallic and gas-permeable pore structure 107, a second interface between the at least partially metallic and gas-permeable pore structure 107 and the flow field 105, and a third interface between the flow field 105 and the bipolar plate 101.

[0044] An examination of the potential levels at the three interfaces, when cell 100 is an electrolytic cell operated at 1.9V, results in the following picture: first interface: E=1.9 V(vs. NHE) second interface: E=0.8−0.9 V third interface: E<0.8 V

[0045] Based on the electrical conditions specified above, it is possible to use alternative coating materials to platinum at least at the second interface and the third interface.

[0046] Tungsten oxides have proven to be alternative materials that are sufficiently stable against oxidation and conductive.

[0047] In Fig. 2 is a manufacturing method 200 for a cell, such as the cell 100 according to Fig. 1, shown.

[0048] The manufacturing method 200 comprises a coating step 201 in which an at least partially metallic and gas-permeable pore structure of the cell is coated with tungsten oxide.

[0049] Optionally, the manufacturing method 200 comprises a pretreatment step 201 in which the at least partially metallic and gas-permeable pore structure is pretreated by means of a cleaning solution before the coating step 203, and a smoothing step 205 in which a coating material made of tungsten oxide is smoothed after the coating step 203, for example by polishing the coating material.

[0050] In Fig. Figure 3 shows a cross-section of the cell 100. Here, it can be seen that it comprises a plate 101 made of steel or titanium, an optional adhesive layer 303 made of metallic tungsten, chromium, and / or titanium, and a surface layer 305 made of a material that includes, for example, tungsten oxide.

Claims

[1] Cell (100) for a cell stack for electrochemically converting energy, the cell (100) comprising - at least one at least partially metallic plate (101, 109) - an at least partially metallic gas-permeable pore structure (107), wherein the plate (101, 109) and / or the pore structure (107) is coated at least in regions with a coating material comprising tungsten oxide. [2] Cell (100) according to claim 1, characterized by that an adhesive layer (303) is formed between the plate (101, 109) and the coating material, which adhesive layer comprises at least one metal or an alloy of the following metals: tungsten, chromium, titanium. [3] Cell (100) according to claim 1 or 2, characterized by that the plate (101, 109) consists of a material comprising steel and / or titanium. [4] Cell (100) according to one of the preceding claims, characterized bythat the plate (101, 109) is a bipolar plate (101) or a part of a bipolar plate (101) and / or an electrode (109). [5] Cell (100) according to one of the preceding claims, characterized by that the pore structure (107) is part of a gas diffusion layer. [6] Bipolar plate (101) for a cell (100), in particular for a cell (100) according to one of claims 1 to 5, for a cell stack for electrochemically converting energy, wherein the bipolar plate (101) is coated at least in regions with a coating material made of tungsten oxide. [7] Bipolar plate (101) according to claim 6, characterized by that an adhesive layer is formed between a basic structure of the bipolar plate (101) and the coating material, which adhesive layer comprises at least one metal or an alloy of the following metals: tungsten, chromium, titanium. [8] Gas diffusion layer for a cell (100), in particular for a cell (100) according to one of claims 1 to 5, for a cell stack for electrochemically converting energy, wherein the gas diffusion layer is coated with at least one coating material made of tungsten oxide. [9] Gas diffusion layer according to claim 8, characterized by that an adhesive layer is formed between a basic structure of the gas diffusion layer and the coating material, which adhesive layer comprises at least one metal or an alloy of the following metals: tungsten, chromium, titanium. [10] Manufacturing method (200) for a cell (100) according to one of claims 1 to 5, wherein the manufacturing method (200) comprises: - coating (203) a metallic structure of the cell (100) with tungsten oxide, wherein the metallic structure comprises an at least partially metallic plate (101, 109) and / or an at least partially metallic gas-permeable pore structure (107). [11] Manufacturing method (200) according to claim 10, characterized by that the tungsten oxide is applied directly to the surface of the metallic structure by thermal spraying or is arranged on the metallic structure via an adhesive layer comprising at least one metal or an alloy of the following metals: tungsten, chromium, titanium.

Images