Method for bonding and sealing of electrode frame to ion exchange membrane or bipolar plate and use thereof

Abstract

This invention relates to the field of battery stacks, and discloses a method for bonding and sealing electrode frames to ion exchange membranes or bipolar plates, and its application. The method involves sulfonating the surfaces of the electrode frames and bipolar plate sealing areas (which contain no reactive substances) to introduce sulfonic acid groups. These sulfonic acid groups react with 1,1'-carbonyldiimidazole, and further react with aromatic diamines to couple and chemically crosslink the sulfonic acid groups on the electrode frame sealing bonding area surface with those in the ion exchange membrane or bipolar plate sealing bonding area, achieving the purpose of bonding and sealing. This method can effectively and reliably bond electrode frames with significantly different polarities and materials to ion exchange membranes or bipolar plates, without introducing the risk of aging of the sealing material itself, significantly reducing or avoiding the risk of battery stack leakage, and without increasing the inherent weight and thickness of the battery stack, making it suitable for industrial promotion and application.

Description

Technical Field

[0001] This invention relates to the field of battery stacks, and in particular to a method for bonding and sealing an electrode frame to an ion exchange membrane or bipolar plate, and its application. Background Technology

[0002] In the battery stack assembly process, bipolar plates, electrode frames, ion exchange membranes, and other materials are stacked sequentially. A key aspect is sealing the gaps between these materials (bipolar plates and electrode frames, ion exchange membranes and electrode frames) to prevent electrolyte leakage during battery stack operation. Currently, battery stack sealing methods mainly include line sealing, surface sealing, line-surface combination sealing, and laser welding sealing. For line sealing, the resilience of the sealing material is critical. During stack assembly and operation, continuous pressure can cause stress relaxation, leading to reduced sealing effectiveness or seal failure, increasing the risk of leakage. Surface sealing typically uses gaskets or hot melt adhesive films of a certain thickness (usually greater than 1 mm). The main problem is that the use of gaskets or hot melt adhesive films increases the weight and thickness of the battery stack. Furthermore, the use of gaskets (commonly silicone rubber gaskets, EVA rubber gaskets, etc.) or hot melt adhesive films (PP hot melt film, P...) can lead to problems. Hot melt adhesive films (such as E-type hot melt films) are non-fluorinated materials. During operation of the sealed battery stack, their cross-sections come into direct contact with the electrolyte. After prolonged operation, the sealing layer gradually corrodes under the electrolyte, leading to leakage. Even using fluororubber gaskets (fluorinated hot melt films are not industrially produced or used) resistant to electrolyte corrosion introduces issues of increased stack weight and thickness, and higher costs. Laser welding is only suitable for sealing materials with similar resin compositions and polarities, such as carbon-plastic composite bipolar plates containing PP, PP electrode frames, and sealing between non-fluorinated ion exchange membranes. However, currently, the most commonly used materials in battery stacks are perfluorosulfonic acid ion exchange membranes and fluorinated bipolar plates, which have excellent corrosion resistance and strong polarity. These are difficult to weld to non-fluorinated resin electrode frames using laser welding, thus limiting the application of laser welding methods. Addressing the aforementioned problems in the bonding and sealing of battery stacks, developing an effective and reliable method for bonding and sealing non-fluorinated resin electrode frames to ion exchange membranes or bipolar plates is one of the important research directions in this field. Summary of the Invention

[0003] The technical solution of this invention is as follows:

[0004] A method for bonding and sealing an electrode frame to an ion exchange membrane, comprising the following steps:

[0005] (A1) After fully sulfonating the surface of the electrode frame bonding sealing area, rinse it clean with deionized water and dry it.

[0006] (A2) Spray an excess of 1,1'-carbonyldiimidazole solution / dispersion onto the sulfonated surface of the electrode frame bonding and sealing area and the surface of the ion exchange membrane bonding and sealing area, respectively. After the reaction is complete, rinse off the residual 1,1'-carbonyldiimidazole with deionized water and dry.

[0007] (A3) Estimate the molar amount X of perfluorosulfonic acid ion groups on one side of the ion exchange membrane's adhesive sealing area based on the ion exchange capacity, areal density, and area of ​​the adhesive sealing area. (Note: Molar amount X of perfluorosulfonic acid ion groups on one side (unit: mol) = ion exchange capacity (unit: mol / g) × areal density (unit: g / m²)) 2 × Area of ​​the bonding and sealing area (unit: m²) 2 () / 2, the estimation process does not consider the thickness and the ion exchange groups inside the membrane), and then the surface of the electrode frame bonding and sealing area described in step (A2) is coated with a solution or dispersion containing an aromatic diamine substance with a molar amount of (0.8-1.2)X. Subsequently, the sealing and bonding area of ​​the ion exchange membrane is bonded to the corresponding sealing and bonding area of ​​the electrode frame, and the bonding is fully reacted under a certain pressure.

[0008] A method for bonding and sealing an electrode frame to a bipolar plate includes the following steps:

[0009] (B1) After the bonding and sealing area of ​​the bipolar plate and the electrode frame is fully sulfonated, it is rinsed clean with deionized water and dried.

[0010] (B2) After sampling the sulfonated bipolar plate's bonding and sealing area, the surface ion exchange capacity of the single-sided sealing area of ​​the bipolar plate is calculated by acid-base titration. The molar amount Y of the sulfonic acid ion groups on one side of the bipolar plate is then calculated based on the area of ​​the bonding and sealing area. (Note: Molar amount Y of the sulfonic acid ion groups on one side (unit: mol) = Area of ​​the bonding and sealing area (unit: m²)) 2 × Surface ion exchange capacity of a single-sided sealed area of ​​a bipolar plate (unit: mol / m³) 2 ))

[0011] (B3) Spray an excess of 1,1'-carbonyldiimidazole solution / dispersion onto the sulfonated bonding and sealing areas of the electrode frame and bipolar plate. After the reaction is complete, rinse off the residual 1,1'-carbonyldiimidazole with deionized water and dry.

[0012] (B4) Coat the surface of the electrode frame bonding and sealing area after step (B3) with a solution or dispersion containing an aromatic diamine substance of molar amount Y. Then, bond the bipolar plate bonding and sealing area after step (B3) to the electrode frame bonding and sealing area and react and bond fully under a certain pressure.

[0013] Furthermore, the electrode frame is made of common resin materials such as PP, PE, PMMA, PPS, and PVC, which are easily sulfonated; the method of full sulfonation treatment is to use concentrated sulfuric acid, chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, etc. for sulfonation. The sulfonation method is a mature industrial method and is not limited or required here.

[0014] Furthermore, the ion exchange membrane is a cation-type sulfonic acid ion exchange membrane (including homogeneous membranes and composite reinforced membranes), including but not limited to perfluorosulfonic acid ion exchange membranes, sulfonated polyether ether ketone ion exchange membranes, etc., and the specific composition is not required or limited.

[0015] Furthermore, the bipolar plate is a carbon-plastic composite bipolar plate.

[0016] Furthermore, the aromatic diamines are substances containing conjugated aromatic diamine structures, such as p-phenylenediamine, benzidine, diaminenaphthalene, diamine anthracene, and diamine phenanthrene. The purpose of using aromatic diamines is to ensure the reactivity of the amino group, making it easier for them to participate in the reaction. Additionally, the aromatic structure has significant steric hindrance, making it suitable for the cross-linking process of the two materials in this invention, reducing or avoiding cross-linking reactions within the material itself.

[0017] Furthermore, the solvents / dispersants used in the solutions / dispersions described in steps (A2), (A3), (B3), and (B4) are low-boiling organic solvents that can dissolve or uniformly disperse the solute, such as acetone, methanol, ethanol, ethyl acetate, etc., so that the solvent can be volatilized and removed in time after the bonding reaction. The specific selection will not affect the final result, and no specific requirements or limitations are made here.

[0018] Furthermore, the estimation of the molar number X of perfluorosulfonic acid ion groups on one side of the ion exchange membrane bonding sealing area in step (A3) cannot be accurately calculated because the ion exchange membrane itself has a certain thickness, and some sulfonate groups are inside the membrane and are not exposed on the membrane surface, thus unable to participate in the actual surface bonding chemical reaction. Therefore, the molar amount of aromatic diamine substances used on one side is limited to the range of (0.8-1.2)X, which is actually controlled based on the membrane thickness and experience.

[0019] Furthermore, the amount of aromatic diamine used needs to be determined based on the number of ion exchange groups on the surface of the ion exchange membrane in the bonding and sealing area or the number of ion exchange groups on the surface of the bipolar plate. This is because the electrode frame is made of a material with a high plastic content, and the degree of sulfonation or the number of sulfonic acid groups in the electrode frame body will be much higher than the number of ion exchange groups in the corresponding ion exchange membrane or bipolar plate. Therefore, the amount is determined based on the side with fewer sulfonic acid groups to avoid excessive use of aromatic diamine, which would result in loss and waste, as well as residue remaining in the bonding and sealing area, leading to bonding and sealing failure.

[0020] Furthermore, the pressure in steps (A3) and (B4) is to promote the bonding process. The pressure is recommended to be above 0.1 MPa, but it must not exceed the pressure resistance limit of the electrode frame material or bipolar plate material to prevent the material from being damaged by pressure.

[0021] Another objective of this invention is to protect the application of the above-described method in the bonding and sealing process of battery stacks, including but not limited to flow battery stacks, fuel cell stacks, etc.

[0022] The inventive point of this invention is: by sulfonating the surfaces of the non-reactive electrode frame and bipolar plate sealing areas, sulfonic acid groups are introduced. These sulfonic acid groups react with 1,1'-carbonyldiimidazole, and further react with aromatic diamines, coupling and chemically cross-linking the sulfonic acid groups on the surface of the electrode frame sealing bonding area with those in the ion exchange membrane or bipolar plate sealing bonding area, thus achieving the purpose of bonding and sealing. Because the sealing bonding areas of the ion exchange membrane and bipolar plate are non-electrode reaction areas, the sulfonic acid ion exchange groups participating in the reaction will not affect the final performance of the battery stack.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a method for chemically crosslinking and sealing an electrode frame with an ion exchange membrane or bipolar plate. This method can effectively bond electrode frames with large differences in polarity and material to the ion exchange membrane or bipolar plate tightly and reliably, without causing the risk of aging of the sealing material itself, greatly reducing or avoiding the risk of leakage of the electrode stack, and without increasing the inherent weight and thickness of the electrode stack, making it suitable for industrial promotion and application. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the bonding and sealing area between the electrode frame and the ion exchange membrane or bipolar plate in a single cell of a fuel cell stack. Detailed Implementation

[0026] To better understand the present invention, the following embodiments further illustrate its content, but the content of the present invention is not limited to the following embodiments. The following embodiments describe in more detail a method for bonding and sealing an electrode frame to an ion exchange membrane or bipolar plate and its application, and these embodiments are given by way of illustration, but these embodiments do not limit the scope of the present invention. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the experimental equipment, materials, reagents, etc. used can be purchased from chemical companies.

[0027] Example 1

[0028] The electrode frame is bonded and sealed to the ion exchange membrane:

[0029] The electrode frame is made of fully sulfonated PP material with a fully bonded sealing area, and the Nafion 212 perfluorosulfonic acid ion exchange membrane is used (thickness 50 μm, ion exchange capacity 0.91 mmol / g, areal density 1.04 g / dm³). 2 The area of ​​the bonding and sealing zone is 8.9 dm². 2 The estimated sulfonate content on one side of the ion exchange membrane in the sealing bonding area is (8.9 × 1.04 × 0.91 / 2 = 4.21 mmol). Therefore, the molar amount of 4,4'-biphenyldiamine used is 1.0 × 4.21 mmol = 4.21 mmol. After being dissolved in acetone, it is evenly sprayed onto the surface of the sealing bonding area of ​​the electrode frame and then pressed at 0.1 MPa for 10 min.

[0030] The electrode frame and bipolar plate are bonded and sealed:

[0031] The electrode frame is made of fully sulfonated PP material with an adhesive sealing area, and the extruded PP bipolar plate is 0.9 mm thick. The surface ion exchange capacity of the single-sided sealing area after sulfonation is 1.81 mmol / dm². 2 The area of ​​the bonding and sealing zone is 8.9 dm². 2 The sulfonate content on one side of the bipolar plate in the bonding and sealing area is (8.9 × 1.81 = 16.11 mmol). Therefore, the molar amount of 4,4'-biphenyldiamine used is 16.11 mmol. After being dissolved in acetone, it is evenly sprayed onto the surface of the electrode frame bonding and sealing area and then pressed at 0.1 MPa for 10 min.

[0032] Ten vanadium redox flow battery stacks were assembled using the above-described method of bonding and sealing the electrode frame to the ion exchange membrane or bipolar plate.

[0033] Example 2

[0034] The electrode frame is bonded and sealed to the proton exchange membrane:

[0035] The electrode frame is made of fully sulfonated PMMA material with a fully bonded sealing area, and a Gore M788.12 proton exchange membrane (12 μm thick ePTFE reinforced membrane, ion exchange capacity 0.86 mmol / g, areal density 0.21 g / dm³) is used. 2 The bonding and sealing area is 1.8dm. 2 The estimated sulfonate content on one side of the ion exchange membrane in the sealing bonding area is (1.8 × 0.21 × 0.86 / 2 = 0.16 mmol). Therefore, the molar amount of 1,6-diaminenaphthalene used is 1.2 × 0.16 mmol = 0.192 mmol. After being dispersed in anhydrous ethanol, it is evenly sprayed onto the surface of the sealing bonding area of ​​the electrode frame and then pressed at 0.2 MPa for 10 min.

[0036] The electrode frame and bipolar plate are bonded and sealed:

[0037] The electrode frame is made of PMMA material with fully sulfonated adhesive sealing area, and the flexible graphite bipolar plate is molded and impregnated (polyacrylic resin, thickness 0.6 mm). The surface ion exchange capacity of the single-sided sealing area after sulfonation is 2.51 mmol / dm². 2 The area of ​​the bonding and sealing zone is 1.8 dm². 2 The sulfonate content on one side of the bipolar plate in the sealing bonding area is (1.8 × 2.51 = 4.52 mmol). Therefore, the molar amount of 1,6-diaminenaphthalene used is 4.52 mmol. After being dispersed in anhydrous ethanol, it is evenly sprayed onto the surface of the sealing bonding area of ​​the electrode frame and then pressed at 0.1 MPa for 10 min.

[0038] Ten hydrogen fuel cell stacks were assembled using the above-described method of bonding and sealing the electrode frame to the ion exchange membrane or bipolar plate.

[0039] Example 3

[0040] The electrode frame is bonded and sealed to the proton exchange membrane:

[0041] The electrode frame is made of fully sulfonated PVC material with a fully sulfonated adhesive sealing area, and the sulfonated polyether ether ketone perfluorosulfonic acid ion exchange membrane is 84 μm thick, has an ion exchange capacity of 1.23 mmol / g, and an areal density of 1.51 g / dm³. 2 The area of ​​the bonding and sealing zone is 8.9 dm². 2 The estimated sulfonate content on one side of the ion exchange membrane in the sealing bonding area is (8.9 × 1.51 × 1.23 / 2 = 8.26 mmol). Therefore, the molar amount of p-phenylenediamine used is 0.8 × 8.26 mmol = 6.6 mmol. After being dissolved in acetone, it is evenly sprayed onto the surface of the sealing bonding area of ​​the electrode frame and then pressed at 0.1 MPa for 15 min before assembling the flow battery stack.

[0042] The electrode frame and bipolar plate are bonded and sealed:

[0043] The electrode frame is made of PVC material with fully sulfonated adhesive sealing area, and the molded flexible graphite bipolar plate (PVDF resin, thickness 0.8 mm, with a surface ion exchange capacity of 0.56 mmol / dm² on one side of the sulfonated sealing area). 2 The area of ​​the bonding and sealing zone is 8.9 dm². 2 The sulfonate content on one side of the bipolar plate in the sealing bonding area is (8.9 × 0.56 = 4.98 mmol). Therefore, the molar amount of p-aminobenzene used is 4.98 mmol. After being dispersed in anhydrous ethanol, it is evenly sprayed onto the surface of the sealing bonding area of ​​the electrode frame and then pressed at 0.1 MPa for 10 min.

[0044] Ten vanadium redox flow battery stacks were assembled using the above-described method of bonding and sealing the electrode frame to the ion exchange membrane or bipolar plate.

[0045] The above-mentioned fuel cell stacks have been operated for a long time (more than 1 year) or 15,000 cycles in actual projects without any leakage, demonstrating the reliability, excellent sealing performance and practicality of the method described in this invention.

[0046] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for bonding and sealing an electrode frame to an adjacent structure, characterized in that, The adjacent structure is an ion exchange membrane, and the process includes the following steps: (A1) After fully sulfonating the surface of the electrode frame bonding sealing area, rinse it clean with deionized water and dry it; (A2) Spray an excess of 1,1'-carbonyldiimidazole solution or dispersion onto the sulfonated surface of the electrode frame bonding and sealing area and the surface of the ion exchange membrane bonding and sealing area, respectively. After the reaction is complete, rinse off the residual 1,1'-carbonyldiimidazole with deionized water and dry. (A3) Calculate the molar amount X of perfluorosulfonic acid ion groups on one side of the ion exchange membrane adhesive sealing area based on the ion exchange capacity and areal density of the ion exchange membrane and the area of ​​the adhesive sealing area. Then, coat the surface of the electrode frame adhesive sealing area described in step (A2) with a solution or dispersion of aromatic diamine substances containing a molar amount of (0.8-1.2)X. Subsequently, combine the sealing adhesive area of ​​the ion exchange membrane with the sealing adhesive area of ​​the electrode frame and allow them to fully react and bond under a certain pressure. Xmol= (ion exchange capacity mol / g x surface density g / m 2 × bonding seal area m 2 ) / 2, regardless of thickness and ion exchange groups inside the film; The electrode frame is made of PP, PE, PMMA, PPS, or PVC. The ion exchange membrane is a cation-type sulfonic acid ion exchange membrane.

2. A method for bonding and sealing an electrode frame to an adjacent structure, characterized in that, The adjacent structure is a bipolar plate, and includes the following steps: (B1) After fully sulfonating the bonding and sealing area of ​​the bipolar plate and electrode frame, rinse it with deionized water and dry it. (B2) After sampling the bonding and sealing area of ​​the sulfonated bipolar plate, the surface ion exchange capacity of the single-sided sealing area of ​​the bipolar plate is calculated by acid-base titration. The molar amount Y of sulfonic acid ion groups on the single side of the bipolar plate is calculated based on the area of ​​the bonding and sealing area. (B3) Spray an excess of 1,1'-carbonyldiimidazole solution or dispersion onto the sulfonated bonding and sealing areas of the electrode frame and bipolar plate. After the reaction is complete, rinse off the residual 1,1'-carbonyldiimidazole with deionized water and dry. (B4) Coat the surface of the electrode frame bonding and sealing area after step (B3) with a solution or dispersion containing an aromatic diamine substance of molar amount Y, and then combine the bonding and sealing area of ​​the bipolar plate after step (B3) with the bonding and sealing area of ​​the electrode frame, and fully react and bond under a certain pressure. The molar amount of sulfonic acid ion groups on one side, Ymol, is equal to the area of ​​the adhesive sealing zone, m. 2 × Surface ion exchange capacity of the single-sided sealed area of ​​the bipolar plate (mol / m²) 2 ; The electrode frame is made of PP, PE, PMMA, PPS, or PVC. The bipolar plate is a carbon-plastic composite bipolar plate.

3. The bonding and sealing method between the electrode frame and the adjacent structure according to claim 1 or 2, characterized in that, The method for fully sulfonating is to use concentrated sulfuric acid, chlorosulfonic acid, fuming sulfuric acid, and sulfur trioxide for sulfonation.

4. The bonding and sealing method between the electrode frame and adjacent structures according to claim 1, characterized in that, The sulfonic acid ion exchange membranes include perfluorosulfonic acid ion exchange membranes and sulfonated polyether ether ketone ion exchange membranes.

5. The bonding and sealing method between the electrode frame and adjacent structures according to claim 1 or 2, characterized in that, The aromatic diamines are p-phenylenediamine, benzidine, diaminenaphthalene, diamine anthracene, and diaminephenanthrene.

6. The bonding and sealing method between the electrode frame and the adjacent structure according to claim 1 or 2, characterized in that, The pressure in steps (A3) and (B4) is above 0.1 MPa to promote the bonding process.

7. The bonding and sealing method between the electrode frame and the adjacent structure according to claim 1 or 2, characterized in that, The method is applied to the bonding and sealing process in the assembly of battery stacks, which include flow battery stacks and fuel cell stacks.

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