Method for producing a seal on a layer or layer of an electrochemical cell, electrochemical cell comprising a seal
By using sealants and adhesives with specific rheological properties, combined with UV or thermosetting technology, the problems of bubbles and defects in the printing of electrochemical battery seals have been solved, enabling the manufacture of high-precision and thick seal layers, thus improving the production efficiency and quality of electrochemical batteries.
Patent Information
- Application Number
- CN202480025337.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-04-13
- Filing Date
- 2024-04-11
- Publication Date
- 2025-11-14
AI Technical Summary
In the manufacturing of electrochemical battery seals, the use of thick screen printing methods in existing technologies easily leads to bubbles and defects, resulting in unstable printed patterns and making it difficult to achieve high-precision and thick sealing structures.
By using sealants and adhesives with specific rheological properties, including materials with a steady-state viscosity of 5 to 20 Pas at a shear rate of 100 s⁻¹, a thixotropic index of 50 to 250 Pas/s, and a surface tension of 15 to 35 mN/m, combined with UV or thermosetting technology, a high-precision and defect-free sealing layer is achieved through screen printing.
It achieves high-precision manufacturing of sealing layer thickness from 300 to 1500 μm, reduces the risk of bubble formation and defects during the printing process, increases design freedom and cycle time, and reduces costs.
Smart Images
Figure CN120958610A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for manufacturing a seal on a layer or layer of an electrochemical cell, particularly a fuel cell, an electrolytic cell, or a cell. The layer or layer may be, for example, a monopolar or bipolar plate, a separator, and / or a membrane electrode assembly.
[0002] Furthermore, the present invention relates to an electrochemical battery, particularly a fuel cell, an electrolytic battery, or a battery cell, having a seal, said seal being manufactured according to the method of the present invention. Background Technology
[0003] Electrochemical cells, such as fuel cells, electrolytic cells, or cell bodies, have a multilayered or multi-layered structure. This structure requires intermediate seals to isolate the media that will be introduced during battery operation. To construct these seals, sealants and / or adhesives are applied to the layers or layers of the battery. Dispensing or printing methods are particularly used in this case.
[0004] Mass production of electrochemical cells requires high processing speeds, which translates to short cycle times and high process stability. Screen printing, in particular, meets these requirements. The screen printing process is essentially divided into the following three sub-steps: 1. Apply a sealant and / or adhesive to the screen, which has been pre-placed on the layer or layer to be printed. 2. During the coating process, fill the screen mesh gaps or multiple screen mesh gaps with sealant and / or adhesive. 3. By separating the mesh from the layers or strata, the sealant and / or adhesive is peeled off from the mesh openings or these mesh openings.
[0005] Here, the mesh thickness determines the layer thickness of the applied structure, typically ranging from 300 μm to 500 μm. However, for sealing electrochemical cells, layer thicknesses up to 1500 μm are required to allow for tolerance compensation and as much freedom as possible in designing the structure to be applied. This is because, depending on the corresponding sealing scheme, the structure to be applied can be large and / or complex.
[0006] To achieve the required layer thickness for the seals in electrochemical cells during screen printing, thicker screens must be used. This, however, increases the risk that air bubbles may become trapped during the coating process as the applied sealant and / or adhesive fills the gaps in the screen, ultimately leading to defects. This is because as the screen thickness increases, the volume of these gaps that need to be filled with sealant and / or adhesive also increases.
[0007] The following is based on the appendix Figure 1a) and 1b) explain the problem. The accompanying drawing shows a screen 3 with gaps 5 placed on a layer or layer 1, which is filled with sealant and / or adhesive by means of a squeegee 6. The squeegee 6 scrapes the surface 4 of the screen 3 facing away from the layer or layer 1 for this purpose. In the scraping direction (see arrow) toward the end of the gap 5, not all air can be expelled from the gap 5, causing air bubbles 8 to form in the gap 5, which prevent the gap 5 from being completely sealed and / or filled with adhesive 2. In this case, the printed pattern is gapped or has defective parts. The risk of surrounded air bubbles 8 increases with the thickness d of the screen 3.
[0008] The following is based on the appendix Figure 2 a) and 2e) illustrate another problem that can also lead to bubble formation. This problem occurs when peeling the sealant and / or adhesive 2 from the screen 3, or when removing the screen 3 from layer 1 or layer 2 (attached). Figure 2 b)) This occurs during separation. Because the partial seal and / or adhesive 2 adheres to the underside of the wire mesh 3 and forms lines 10 (attached). Figure 2 c)). This is particularly applicable when the wire mesh 3 has tabs 9 for securing and / or connecting multiple wire mesh components. Lines 10, also known as threads, are pulled or extended in the length direction when the wire mesh 3 is lifted until they break or detach from the wire mesh 3 (see appendix). Figure 2 d)). When line 10 subsequently collapses, bubble 8 may form (see attached image). Figure 2 e).
[0009] However, depending on the rheology of the seal and / or adhesive, other unintended effects may occur upon peeling. This is exemplified in... Figure 3 As shown in the diagram. In this case, instead of adhesion retention on the screen 3, the seal and / or adhesive 2 spreads and slumps when it is peeled off. This results in a printed structure that is not dimensionally stable and lacks a clear outline. Summary of the Invention
[0010] The present invention aims to minimize the problems described above that occur when manufacturing seals using screen printing, thereby achieving higher dimensional accuracy and as few defects as possible in the printed pattern.
[0011] To address this task, a method having the features of claim 1 is proposed. Advantageous extensions of the invention can be derived from the dependent claims. Furthermore, an electrochemical cell with a sealed element is provided.
[0012] A method is proposed for manufacturing seals on layers or scales of an electrochemical cell using screen printing, wherein a sealant / or adhesive having structural viscous behavior and / or thixotropic behavior is used as the printing material. According to the invention, a sealant and / or adhesive having the following parameters is used: a) At a shear rate of 100 s -1 The steady-state viscosity is 5 to 20 Pa. s, preferably 10 to 15 Pa s, preferably 12.5 Pa s, b) Thixotropic index (TI) of 50 to 250 Pa s / s, preferably 120 to 180 Pa s / s, preferably 150 Pa s / s, and c) The surface tension is 15 to 35 mN / m, preferably 20 to 30 mN / m, and even more preferably 25 mN / m.
[0013] When printing materials exhibit structurally viscous behavior, shear stress increases disproportionately with increasing shear rate. This means that viscosity decreases with increasing shear rate. The shear rate introduced into the printing material by the scraper motion is typically greater than 100 s⁻¹. -1 This results in a decrease in viscosity, which proves to be an advantage when filling the mesh gaps or these mesh gaps with sealants and / or adhesives.
[0014] A very low sludge level, less than 0.1s, was observed after the sealant and / or adhesive were peeled off. -1 The shear rate is crucial. Simultaneously, a higher viscosity is required so that the sealant and / or adhesive does not flow. Therefore, viscosity should be rebuilt as quickly as possible after the coating process. Here, the viscosity recovery rate, or the thixotropic behavior of the sealant and / or adhesive, plays a significant role.
[0015] The surface tension of the sealant and / or adhesive also affects the formation of filaments and possible air bubbles during the separation of the wire mesh.
[0016] The combination of these three rheological properties is therefore crucial for the screen printing process and achieving the required layer thickness. By using sealants and / or adhesives with values within a given range for these three rheological properties as printing materials, the printability of the printing material can be improved, and the dimensional accuracy of seals manufactured from the printing material can be enhanced.
[0017] Furthermore, another positive effect is achieved: the printing material exhibits minimal sensitivity to increases in squeegee speed. Tests show that, for example, the squeegee speed can be increased from 40 mm / s to 160 mm / s without compromising other advantages such as printability of the printing material and dimensional accuracy of the printed structure. This means that a reduction in cycle time is possible, which in turn leads to a decrease in cost.
[0018] To determine at a shear rate of 100 s -1 For the steady-state viscosity at a shear rate of 100 s, refer to DIN EN ISO 3219-1 (published 2021-08) and DIN EN ISO 3219-2 (published 2021-08). According to these standards, the so-called rotational rheometer method can be used. Here, at a shear rate of 100 s... -1 The steady-state viscosity is measured under uniform shear flow conditions. Here, plate-to-plate or cone-to-plate measurement geometries can be used.
[0019] Thixotropy is defined in DIN 1342-3:2003-11. Furthermore, reference can be made to technical report DIN / TR 91143-2 “Rheologische Prüfverfahren” – Teil 2: “Thixotropie – Bestimmung der zeitabhängigen Strukturänderung – Grundlagen und Ringversuch” (“Rheological Testing Methods” – Part 2: “Thixotropy – Determination of Time-Related Structural Changes – Principles and Cyclic Tests”); written in German and English, published 2022-07. To determine the thixotropic index (TI), which describes the thixotropic behavior of a substance, standards DIN EN ISO 3219-1 (published 2021-08) and DIN EN ISO 3219-2 (published 2021-08) can also be cited, particularly regarding the working steps and measuring instruments. This means that the rotational rheometer method can also be used here. The thixotropic index (TI) can then be calculated from the obtained measurements using the following formula: .
[0020] The specific test design and test procedures for determining IT are described below according to the appendix. Figure 4 Further details.
[0021] The following standards can be used to determine surface tension: -DIN EN 14370:2004, published 2004-11, -Interfacial active substances -Determination of surface tension (Grenzflächenaktive Stoffe – Bestimmung der Oberflächenspannung) and / or -DIN EN ISO 19403-3:2020, published in 2020-04, - Coating materials - Wetness - Part 3: Determination of surface tension of liquids by means of suspended droplets (Beschichtungsstoffe – Benetzbarkeit – Teil3: Bestimmung der Oberflächenspannung von Flüssigkeiten mit der Methode des hängenden Tropfens) (ISO19403-3:2017).
[0022] Preferably, UV-curable and / or heat-curable sealants and / or adhesives are used. This type of sealant and / or adhesive has the advantage that it cures very quickly by exposure to UV light and / or by heat, which is advantageous in terms of reducing cycle time.
[0023] Furthermore, it is preferable to use sealants and / or adhesives based on epoxides, silicones, and / or acrylics, especially epoxide-acrylic acids. This type of sealant and / or adhesive inherently possesses advantageous rheological properties, particularly regarding the required surface tension. The use of such sealants and / or adhesives thus helps to achieve the required surface tension.
[0024] A further extension of the invention proposes the use of sealants and / or adhesives containing silicic acid, particularly highly dispersible silicic acid. Alternatively or additionally, silicic acid, particularly highly dispersible silicic acid, can be added to the sealants and / or adhesives used. The silicic acid, particularly highly dispersible silicic acid, influences the structural viscous behavior and / or thixotropic behavior of the sealant and / or adhesive, thereby allowing for targeted control at a shear rate of 100 s. -1 The steady-state viscosity and thixotropic index at that time. Silica has no significant effect on surface tension. For surface tension, the substrate of the sealant and / or adhesive plays a primary role, wherein the substrate is preferably an epoxide, silicone, and / or acrylic substrate. Specialized additives, such as silica-containing surface additives, can be added to specifically control surface tension.
[0025] The proposed method enables the manufacture of seals with a thickness exceeding 300 μm, preferably exceeding 500 μm. Increasing the seal thickness enhances design freedom and the possibility of tolerance compensation. Therefore, in the proposed method, the seal and / or adhesive are preferably applied to the layer or layer with a thickness of 300 to 1500 μm, preferably 500 to 1500 μm, using screen printing.
[0026] Furthermore, preferably, the following steps are performed to apply the sealant and / or adhesive to the layer or layer: - Place the screen mesh on layers or tiers. - Apply sealant and / or adhesive to the surface of the backing layer or layer of the screen mesh. - At least one void in the wire mesh is filled with a sealant and / or adhesive using a scraper, which scrapes the surface of the wire mesh for this purpose, wherein air present in the void is expelled by the sealant and / or adhesive.
[0027] The rheological properties of the sealant and / or adhesive used ensure that at least one void in the wire mesh is completely filled with the sealant and / or adhesive. This means that no air bubbles remain after the sealant and / or adhesive is peeled off, preventing defects. Furthermore, the flow of the sealant and / or adhesive is prevented. Due to the optimized rheological properties of the sealant and / or adhesive, the scraper speed can also be increased, resulting in a reduced cycle time.
[0028] Preferably, sealants and / or adhesives are applied to the monopolar or bipolar plates, separators, and / or membrane electrode assemblies of the electrochemical cell. Seals made of sealants and / or adhesives are used to separate and / or seal the medium within the electrochemical cell from the outside.
[0029] Furthermore, an electrochemical cell is proposed having at least one layer or layer with a seal, said seal being manufactured according to the method of the invention and having a thickness of 300 to 1500 μm, preferably 500 to 1500 μm. Because said seal is manufactured according to the method of the invention, it still has high dimensional accuracy despite its considerable thickness.
[0030] A layer or sublayer coated thereon with sealing and / or adhesive for the purpose of manufacturing a seal, particularly a monopole or bipole plate, separator, and / or membrane electrode assembly of an electrochemical cell. In this case, the seal can be used to separate the medium within the electrochemical cell or to seal the electrochemical cell externally. Attached Figure Description
[0031] The invention and its advantages are further explained below with reference to the accompanying drawings. The drawings show: Figure 1a) and b) respectively show longitudinal sections through layers or tiers of an electrochemical cell, with a wire mesh placed during the scraping process; Figure 2 a) through e) show longitudinal sections of the layers or layers passing through the electrochemical cell during the printing process using screen printing. Figure 3 Showing a longitudinal section of a layer or layer passing through an electrochemical cell during pressurization using a screen printing process; Figure 4 A graph is shown to describe the measurement curve used to calculate the thixotropic index (TI); Detailed Implementation
[0032] The problems that frequently occur when manufacturing seals using screen printing have already been discussed at the beginning, according to the appendix. Figure 1 a) and b) Appendix Figure 2 a) to e) and according to Figure 3 This section of the instruction manual provides an explanation, so please refer to it.
[0033] Therefore, the following is based solely on Figure 4 The invention and its advantages will be further explained.
[0034] Figure 4 The chart exemplifies the measurement curves used to determine the thixotropic index (TI) of sealant and / or adhesive specimens exhibiting structural viscous or thixotropic behavior. To determine the thixotropic behavior, a rotational rheometer method is applied using a plate-to-plate measurement geometry. The plate diameter is 25 mm, and the plate spacing is 0.4 mm.
[0035] To investigate the time-dependent build-up of the sample structure, two measurement segments, A1 and A2, were combined in series. The first measurement segment, A1, was used to simulate shearing during the coating process, with a pre-defined time of 200 seconds for a period of at least 10 to 20 seconds. -1 The high shear rate aims to disrupt the internal structure of the specimen as much as possible. The second measurement section A2 should simulate the recovery phase and therefore the structural recovery after the scraping process. For this purpose, a time of 0.1s is pre-defined for a minimum of 180 seconds. -1 The low shear rate. The viscosity of the sample was measured during this period. Specifically, the viscosity is measured at the first time point t1, which coincides with the end of the first measurement segment A1, such that the viscosity measured at time point t1 is... This indicates the viscosity of the sample after high shear stress. Another measurement was performed at time point t2, specifically 10 seconds after the first time point t1, meaning during the recovery phase. The viscosity measured at time point t2... Or during the 10-second recovery phase (this time period is within) Figure 4 The chart uses tT1 The increase in viscosity after labeling is characterizing the thixotropic behavior of the sample. This is based on measured values. and Formulas can be used Calculate the thixotropic index (TI).
Claims
1. A method for manufacturing a seal on a layer or layer (1) of an electrochemical cell by means of screen printing, wherein, Use sealants and / or adhesives with structural adhesive behavior and / or thixotropic behavior as printing materials. Its characteristic is that it uses a sealing and / or adhesive having the following parameters (2): a) At a shear rate of 100 s -1 The steady-state viscosity is 5 to 20 Pa. s, preferably 10 to 15 Pa s, preferably 12.5 Pa s, b) Thixotropic index (TI) of 50 to 250 Pa s / s, preferably 120 to 180 Pa s / s, preferably 150 Pa s / s, and c) The surface tension is 15 to 35 mN / m, preferably 20 to 30 mN / m, and even more preferably 25 mN / m.
2. The method according to claim 1, Its features are, Use UV-cured and / or heat-cured sealants and / or adhesives (2).
3. The method according to claim 1 or 2, Its features are, Use sealants and / or adhesives based on epoxides, silicones and / or acrylics, especially epoxide-acrylics (2).
4. The method according to any one of the preceding claims, Its features are, Add silicic acid, especially highly dispersible silicic acid, to the sealant and / or adhesive (2).
5. The method according to any one of the preceding claims, Its features are, The sealant and / or adhesive (2) is applied to the layer or layer (1) by means of screen printing with a layer thickness of 300 to 1500 μm, preferably 500 to 1500 μm.
6. The method according to any one of the preceding claims, Its features are, Perform the following steps to apply the sealant and / or adhesive (2) to the layer or layer (1): - Place the screen (3) on the layer or layer (1), - Apply the sealant and / or adhesive (2) to the surface (4) of the wire mesh (3) opposite to the layer or layer (1), - Using a scraper (6), at least one gap (5) of the wire mesh (3) is filled with the sealant and / or adhesive (2), the scraper scraping the surface (4) of the wire mesh (3) for this purpose, wherein air (7) present in the gap (5) is expelled by the sealant and / or adhesive (2).
7. The method according to any one of the preceding claims, Its features are, The sealant and / or adhesive (2) is applied to the monopole or bipole, separator and / or membrane electrode assembly of the electrochemical cell by means of screen printing.
8. An electrochemical cell having at least one layer or layer (1) with a seal, said seal being manufactured by the method according to any one of the preceding claims and having a thickness of 300 to 1500 μm, preferably 500 to 1500 μm.
9. The method according to claim 8, Its features are, The layer or layer (1) is the single or double plate, separator and / or membrane electrode assembly of the electrochemical cell.