Fuel cell, membrane electrode assembly and preparation method thereof

Abstract

The invention provides a fuel cell, a membrane electrode assembly and a preparation method thereof. The electrode assembly comprises an outer frame and an inner frame, the outer frame is arranged on the outer side of the gas diffusion layer, the outer frame and the gas diffusion layer are arranged at an interval, and the outer frame comprises a first outer frame and a second outer frame which clamp the edge of the catalyst layer coating film; the inner frame is arranged between the outer frame and the gas diffusion layer and comprises a first inner frame and a second inner frame which are positioned on two sides of the proton exchange membrane; the side faces, facing the gas diffusion layer, of the first outer frame and the second outer frame are each provided with a first recess, the side faces, facing the outer frame, of the two sub-layers are each provided with a second recess, one parts of the first inner frame and the second inner frame are located in the first recesses, and the other parts are located in the second recesses. The contact surface of the catalyst layer coating film and the outer frame and the contact surface of the gas diffusion layer and the inner frame are both glued, the catalyst layer coating film abuts against the contact surface of the inner frame, the membrane electrode assembly can effectively overcome the transverse stress, and the durability of the membrane electrode sealing frame is remarkably enhanced.

Description

Technical Field

[0001] The present application relates to the technical field of fuel cells, and in particular to a fuel cell membrane electrode assembly with a sealed frame structure, a fuel cell with such a membrane electrode assembly, and a method for preparing the membrane electrode assembly. Background Art

[0002] A fuel cell is a power generation device that converts chemical energy into electrical energy. The specific principle is that during the electrochemical reaction between oxygen and hydrogen, hydrogen releases electrons at the anode, and these electrons are conducted to the cathode through an external circuit. The hydrogen ions that have lost their electrons pass through the proton exchange membrane to the cathode and combine with oxygen atoms and electrons to generate water. The electrons generate current during their migration in the external circuit.

[0003] Fuel cells are usually composed of a certain number of bipolar plate assemblies, membrane electrode assemblies, and sealing materials stacked in series to form multiple single cells, and then added with insulating plates, collector plates, end plates, fasteners and other components to finally assemble into a fuel cell stack. As the core component of the fuel cell, the design and manufacturing process of the membrane electrode assembly have an important impact on the battery performance and life. The process of the membrane electrode assembly can be mainly divided into two types: catalyst coated membrane (CCM) and gas diffusion electrode (CCS). The former is the current mainstream form. Specifically, the catalyst layer is directly coated on the proton exchange membrane, and then the catalyst coated membrane and the gas diffusion layer are hot-pressed or cold-pressed with the sealing frame to form a membrane electrode assembly. During the assembly and use of the membrane electrode assembly, it needs to be fully sealed to avoid leakage of the reaction gas or cooling medium. The direct sealing structure is a widely used sealing form, but this sealing has obvious defects. On the one hand, it is very easy to cause defects such as burrs on the edge of the gas diffusion layer to damage the catalyst coated membrane. On the other hand, the membrane electrode is affected by the longitudinal alternating shear stress during operation, resulting in mechanical damage such as fracture at the edge, resulting in electrode penetration problems in the early stage of use. In order to solve the problem of mechanical damage caused by stress concentration at the junction of the catalyst layer coating membrane and the frame, symmetrical and asymmetrical structural sealing structures of the inner frame are proposed.

[0004] However, these two sealing structures can only partially solve the problem of poor sealing caused by edge burrs and longitudinal shear stress during membrane electrode operation, and the performance or durability of the membrane electrode assembly has not yet reached the expected level. Summary of the invention

[0005] In order to solve at least one of the problems mentioned in the background technology section of this application, the present application provides a fuel cell membrane electrode assembly with a sealed frame structure, a fuel cell with such a membrane electrode assembly, and a method for preparing such a membrane electrode assembly. The membrane electrode assembly provided by the embodiment of the present application solves the problem of poor sealing caused by edge burrs and longitudinal shear stress during operation, and also reduces the technical impact of poor sealing caused by factors such as uneven friction of the rough surface of the proton exchange membrane or the carbon paper on the catalyst layer coating membrane. More importantly, it solves the problem of creep in the overlapping area of ​​the proton exchange membrane frame, which causes non-uniform sliding and deformation, causing damage to the proton exchange membrane, and reducing the performance or durability of the membrane electrode assembly. The fuel cell with such a membrane electrode assembly and the membrane electrode assembly prepared by the method of this patent also have the same technical effects.

[0006] In a first aspect of an embodiment of the present application, a fuel cell membrane electrode assembly with a sealed frame structure is provided, comprising: a catalyst layer coated membrane, comprising a proton exchange membrane having a middle portion and an outer edge portion, wherein the surface of the middle portion is coated with a catalyst layer; a gas diffusion layer, comprising two sublayers respectively applied to the surfaces of both sides of the catalyst layer coated membrane, wherein the sublayers completely cover the middle portion and at least partially cover the outer edge portion; an outer frame, arranged on the outside of the gas diffusion layer and spaced apart from the gas diffusion layer, comprising a first outer frame and a second outer frame that clamp the edge of the proton exchange membrane; an inner frame, arranged Between the outer frame and the gas diffusion layer, it includes a first inner frame and a second inner frame located on both sides of the proton exchange membrane; wherein, the first outer frame and the second outer frame are respectively provided with first depressions on the sides facing the gas diffusion layer, and the two sublayers are respectively provided with second depressions on the sides facing the outer frame, a part of the first inner frame and the second inner frame is located in the first depression, and the other part is located in the second depression; the contact surface between the catalyst layer coating membrane and the outer frame and the contact surface between the gas diffusion layer and the inner frame are both glued, and the catalyst layer coating membrane is in contact with the contact surface of the inner frame.

[0007] In a possible implementation, the width of the first inner frame is smaller than the width of the second inner frame, and the width of the second inner frame is equal to the sum of the widths of the first recess and the second recess.

[0008] In a possible implementation, the material of the inner frame is a combination of one or more of PTFE, PEN, PI or PPS film, and the thickness of the inner frame is 10-25 um.

[0009] In a possible implementation, the material of the outer frame is a combination of one or more of PEN, PI, PET or PPS film, and the thickness of the outer frame is 30-150 um.

[0010] In a possible implementation, the width of an overlapping region between the inner frame and the gas diffusion layer is greater than 2 mm, and the width of an overlapping region between the inner frame and the outer frame is greater than 2 mm.

[0011] In a possible implementation, a gap between the gas diffusion layer and the outer frame is greater than 0.5 mm.

[0012] In a possible implementation,

[0013] The contact surfaces of the catalyst layer coating membrane and the outer frame and the contact surfaces of the gas diffusion layer and the inner frame are bonded by one or more combinations of pressure-sensitive adhesive, hot-melt adhesive or UV adhesive.

[0014] In a possible implementation, the outer edge portion exceeds the inner frame by at least 3 mm.

[0015] During the operation of the fuel cell, the volume of the membrane electrode assembly material will repeatedly increase or decrease due to changes in reaction temperature and humidity or changes in the phase of the medium, and the catalyst layer coated membrane will creep and deform relative to the sealing frame. Such creep will cause non-uniform sliding and deformation, damage the membrane body, and thus affect the performance or durability of the membrane electrode. In this application, the contact surface between the outer frame and the catalyst layer coated membrane is glued, and relative sliding does not easily occur between them; while the inner frame and the catalyst layer coated membrane are simply overlapped, and no colloid is set. When the volume of the liquid material inside the membrane electrode assembly changes, the creep force can be offset by relative movement between them, avoiding non-uniform sliding and deformation of the membrane body. In this way, not only the good sealing ability of the membrane electrode assembly in static state is ensured, but also the sealing failure problem caused by membrane sliding and deformation during operation is solved, and the performance or durability of the membrane electrode is improved as a whole.

[0016] According to a second aspect of the embodiments of the present application, a fuel cell is provided, wherein the fuel cell adopts any of the aforementioned membrane electrode assemblies.

[0017] According to a third aspect of an embodiment of the present application, a method for preparing a membrane electrode assembly is provided, which is used to prepare any of the membrane electrode assemblies described above, comprising the steps of: providing an outer frame and an inner frame, wherein the outer frame comprises a first outer frame and a second outer frame which are symmetrical in the thickness direction and are frame-shaped, wherein the edges of the first outer frame and the second outer frame both comprise a first recess and a third recess which are step-shaped, and the inner frame comprises a first inner frame and a second inner frame which are frame-shaped; applying glue on the surface of one end of the first inner frame and the second inner frame or the step surface of the first recess, placing the one end of the first inner frame and the second inner frame in the first recess of the first inner frame and the second inner frame respectively, extending the other end of the first inner frame and the second inner frame out of the first recess, and respectively pressing the first outer frame with the first inner frame, and the second outer frame with the second inner frame to obtain two double-layer frame structures; providing a catalyst layer coated membrane, comprising a proton exchange membrane having a middle portion and an outer edge portion; Replace the membrane, wherein the surface of the middle part is coated with a catalytic layer, the sublayer completely covers the middle part and at least partially covers the outer edge part, and the two double-layer frame structures are symmetrically arranged on the outside of the catalyst layer coated membrane to clamp the outer edge part, wherein the outer edge part covers the inner frame and extends into the third recess of the outer frame, and the contact surface between the first outer frame and the second outer frame and the contact surface between the first outer frame, the second outer frame and the catalyst layer coated membrane are glued and bonded; provide a gas diffusion layer, the gas diffusion layer includes two sublayers, and the edges of the sublayers are formed with a second recess in a step shape, and the two sublayers are respectively arranged on both sides of the catalyst layer coated membrane and the other ends of the first inner frame and the second inner frame are respectively located in the second recesses of the two sublayers, and the end faces of the two sublayers are kept spaced apart from the outer frame; the gas diffusion layer, the double-layer frame structure and the catalyst layer coated membrane are pressed together to obtain the membrane electrode assembly.

[0018] The fuel cell provided in the second aspect of the present application and the membrane electrode assembly prepared according to the method of the third aspect of the present application have the same or similar technical effects as the membrane electrode assembly provided in the first aspect of the present application, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation to the present application.

[0020] Figure 1 An exploded diagram of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application;

[0021] Figure 2 A cross-sectional view along AA' of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application;

[0022] Figure 3 A partially enlarged cross-sectional view of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application;

[0023] Figure 4 A partially enlarged cross-sectional view of another schematic structure of a membrane electrode assembly provided in an embodiment of the present application;

[0024] Figure 5 A flowchart of a method for preparing a membrane electrode assembly provided in an embodiment of the present application.

[0025] Among them, 100-membrane electrode assembly; 10-catalytic layer coated membrane; 11-proton exchange membrane; 20-gas diffusion layer; 21-sublayer; 211-second recess; 30-outer frame; 301-first recess; 303-third recess; 31-first outer frame; 32-second outer frame; 40-inner frame; 41-first inner frame; 42-second inner frame. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of this application, unless otherwise specified, "plurality" means two or more.

[0028] Figure 1 An exploded diagram of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application, Figure 2 A cross-sectional view of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application. As shown in the figure, the membrane electrode assembly may include a catalyst layer coated membrane 10, a gas diffusion layer 20, and a double-layer frame structure, wherein the double-layer frame structure further includes an inner frame and an outer frame.

[0029] It should be noted that the specific material components, preparation process, size parameters, etc. of the catalyst layer coating membrane 10 and the gas diffusion layer 20 are not the invention of this application, so they are not described in detail here. However, it can be determined that those skilled in the art can realize it based on the disclosure of this application and in combination with the existing technology and common knowledge in this field.

[0030] Figure 3 A partial enlarged cross-sectional view of a schematic structure of a membrane electrode assembly provided in an embodiment of the present application, specifically Figure 2 Enlarged view of point B in the middle.

[0031] The catalyst layer coated membrane 10 includes a proton exchange membrane 11 having a middle portion and an outer edge portion, and the surface of the middle portion is coated with a catalyst layer 12; the gas diffusion layer 20 includes two sublayers 21 respectively attached to the surfaces of both sides of the catalyst layer coated membrane 10, and the sublayers 21 completely cover the middle portion and at least partially cover the outer edge portion; the outer frame 30 is arranged on the outside of the gas diffusion layer 20 and is spaced from the gas diffusion layer 20, and includes a first outer frame 31 and a second outer frame 32 that clamp the edge of the proton exchange membrane 11; the inner frame 40 is arranged between the outer frame 30 and the gas diffusion layer 20, and includes a A first inner frame 41 and a second inner frame 42 are provided on both sides of the proton exchange membrane 11; wherein, the first outer frame 31 and the second outer frame 32 are respectively provided with first recesses 301 on the sides facing the gas diffusion layer 20, and the two sublayers 21 are respectively provided with second recesses 211 on the sides facing the outer frame 30, a part of the first inner frame 41 and the second inner frame 42 are located in the first recess 301, and the other part is located in the second recess 211; the contact surface between the catalyst layer coated membrane 10 and the outer frame 30 and the contact surface between the gas diffusion layer 20 and the inner frame 40 are both glued, and the contact surface between the catalyst layer coated membrane 10 and the inner frame 40 is abutted.

[0032] During the operation of the fuel cell, the volume of the liquid material inside the membrane electrode assembly 100 will increase or decrease repeatedly due to temperature changes or phase changes, and the proton exchange membrane will creep and deform relative to the sealing frame. Such creep will cause non-uniform sliding and deformation, damage the membrane body, and thus affect the performance or durability of the membrane electrode. In this application, the contact surface between the inner frame 40, the outer frame 30 and the proton exchange membrane is glued, and relative sliding does not easily occur between each other; while the inner frame 40 and the gas diffusion layer 20 and the proton exchange membrane are simply overlapped, and no colloid is set. When the volume of the liquid material inside the membrane electrode assembly 100 changes, the creep force can be offset by relative movement between each other, avoiding non-uniform sliding and deformation of the membrane body. In this way, not only the good sealing ability of the membrane electrode assembly 100 in a static state is guaranteed, but also the sealing failure problem caused by membrane sliding and deformation during operation is solved, and the performance or durability of the membrane electrode is improved as a whole.

[0033] Figure 3 A partial enlarged cross-sectional view of another membrane electrode assembly 100 schematically shown in an embodiment of the present application, specifically Figure 2 Enlarged view of point B in the middle.

[0034] Figure 4 and Figure 3Compared with the embodiment shown, the difference lies in the inner frame 40. Based on this premise, the description of the same parts of the two is omitted, but those skilled in the art can refer to the above Figure 3 The description implements this embodiment or other embodiments of the present application.

[0035] The width of the first inner frame 41 is smaller than the width of the second inner frame 42, and the width of the second inner frame 42 is equal to the sum of the widths of the first recess 301 and the second recess 211. In this embodiment, when the components and materials in the membrane electrode assembly 100 are deformed, in addition to the "overlap" method that can offset creep to a certain extent, the redundant gap between the space formed by the first inner frame 41 and the first recess 301 and the second recess 211 can also play a similar role and avoid damage caused by excessive extrusion between materials.

[0036] The following description of the specific implementation methods of this application, unless otherwise specified, can be understood as applicable to Figure 3 and Figure 4 In the embodiment shown.

[0037] In a possible embodiment, the material of the inner frame is a combination of one or more of PTFE, PEN, PI or PPS films, and the thickness of the inner frame 40 is 10-25um. Among them, PTFE is polytetrafluoroethylene material, PEN is polyarylethernitrile or polyethylene naphthalate, PI is polyimide, and PPS is polyphenylene sulfide. Compared with the outer frame 30, the inner frame 40 needs to have a relatively flexible ability so that it can be well contacted with the gas diffusion layer 20 and the proton exchange membrane under a certain pressure, and can also play a good sealing ability without gluing. PTFE, PEN, PI or PPS material films with a thickness value in the range of 10-25um can meet this demand.

[0038] In a possible implementation, the material of the outer frame 30 is a combination of one or more of PEN, PI, PET or PPS film, and the thickness of the outer frame 30 is 30-150um. Among them, PET is polyethylene terephthalate, PEN is polyarylethernitrile or polyethylene naphthalate, PI is polyimide, and PPS is polyphenylene sulfide. The outer frame 30 needs a certain hardness and strength, and it will not be easily deformed to cause sealing failure, nor will it damage other parts due to its own properties. Therefore, a PEN, PI, PET or PPS film with a thickness in the range of 30-150um can achieve this effect.

[0039] In a possible implementation, the width of the overlapping area between the inner frame 40 and the gas diffusion layer 20 is greater than 2 mm, and the width of the overlapping area between the inner frame 40 and the outer frame 30 is greater than 2 mm. In this implementation, the width of the overlapping area between the inner frame 40 and the gas diffusion layer 20 is greater than 2 mm, which, on the one hand, increases the length of the gas escape path and reduces the probability of leakage, and on the other hand, avoids the positioning accuracy error in the process causing the inner frame 40 and the gas diffusion layer 20 to be misaligned, affecting the product yield.

[0040] In a possible implementation, the gap between the gas diffusion layer 20 and the outer frame 30 is greater than 0.5 mm. The outer frame 30 is usually thicker and has a relatively greater hardness. By keeping the gap between the gas diffusion layer 20 and the outer frame 30 greater than 0.5 mm, it is possible to avoid the outer frame 30 directly pressing on the gas diffusion layer 20 due to positioning accuracy errors, causing structural damage to the gas diffusion layer 20 and affecting the performance of the membrane electrode assembly 100.

[0041] In a possible implementation manner, the contact surfaces between the catalyst layer coating membrane 10 and the outer frame 30 and between the gas diffusion layer 20 and the inner frame 40 are bonded by a combination of one or more of pressure-sensitive adhesive, hot-melt adhesive or UV adhesive.

[0042] In a possible implementation, the outer edge portion exceeds the inner frame 40 by at least 3 mm. In this implementation, it can be ensured that the proton exchange membrane extends beyond the inner frame 40 and overlaps with the outer frame 30 by at least 1 mm, further ensuring the bonding effect between the proton exchange membrane and the outer frame 30, and improving the reliability of the membrane electrode assembly 100.

[0043] Not shown in the drawings, the embodiments of the present application further provide a fuel cell, which includes any one of the membrane electrode assemblies 100 described in the embodiments of the present application.

[0044] Figure 5 The present invention provides a flowchart of a method for preparing a membrane electrode assembly 100 provided in an embodiment of the present application. The membrane electrode assembly 100 is any membrane electrode assembly 100 described in the embodiment section of the present application.

[0045] like Figure 5 As shown, the method comprises the steps of:

[0046] S501: Provide an outer frame 30 and an inner frame 40.

[0047] Specifically, the outer frame 30 includes a first outer frame 31 and a second outer frame 32 which are symmetrical in the thickness direction and are frame-shaped. The edges of the first outer frame 31 and the second outer frame 32 both include a first stepped recess 301 and a third recess 303. The inner frame 40 includes a first inner frame 41 and a second inner frame 42 which are frame-shaped.

[0048] S502: Bond the outer frame 30 and the inner frame 40 to obtain two double-layer frame structures.

[0049] Specifically, glue is applied on the surface of one end of the first inner frame 41 and the second inner frame 42 or the step surface of the first recess 301, and one end of the first inner frame 41 and the second inner frame 42 are placed in the first recess 301 of the first inner frame 41 and the second inner frame 42 respectively, and the other ends of the first inner frame 41 and the second inner frame 42 are extended out of the first recess 301, and the first outer frame 31 and the first inner frame 41, and the second outer frame 32 and the second inner frame 42 are pressed together respectively to obtain two double-layer frame structures.

[0050] S503: Provide a catalytic layer coated membrane 10, clamp the catalytic layer coated membrane 10 between two double-layer frame structures, and then press them together.

[0051] Specifically, the provided catalyst layer coated membrane 10 includes a proton exchange membrane having a middle portion and an outer edge portion, wherein the surface of the middle portion is coated with a catalyst layer, the sublayer 21 completely covers the middle portion and at least partially covers the outer edge portion, and two double-layer frame structures are symmetrically arranged on the outside of the catalyst layer coated membrane 10 to clamp the outer edge portion, wherein the outer edge portion covers the inner frame 40 and extends into the third recess 303 of the outer frame 30, and the contact surface between the first outer frame 31 and the second outer frame 32 and the contact surface between the first outer frame 31, the second outer frame 32 and the catalyst layer coated membrane 10 are glued and bonded;

[0052] S504: providing a gas diffusion layer 20, arranging the sublayer 21 of the gas diffusion layer 20, the pressed catalyst layer coating membrane 10, and the double-layer frame structure as required, and then pressing them.

[0053] Specifically, the provided gas diffusion layer 20 includes two sublayers 21, and a second step-shaped recess 211 is formed at the edge of the sublayer 21. The two sublayers 21 are respectively arranged on both sides of the catalyst layer coated membrane 10, and the other ends of the first inner frame 41 and the second inner frame 42 are respectively located in the second recesses 211 of the two sublayers 21, so that the end faces of the two sublayers 21 are kept separated from the outer frame 30; the gas diffusion layer 20, the double-layer frame structure and the catalyst layer coated membrane 10 are pressed together to obtain the membrane electrode assembly 100.

[0054] In order to further verify the technical effects produced by the embodiments of the present application, the applicant prepared the membrane electrode assembly provided in the embodiments of the present application through the membrane electrode assembly preparation method provided in the embodiments of the present application, assembled the membrane electrode assembly into a fuel cell, conducted tests, and compared the results with the solutions of the present application that were known to the inventor but not implemented.

[0055] Embodiment 1 of the present application:

[0056] A PTFE film with a thickness of 10 μm is used as the inner frame, and a PEN hot melt adhesive film with a thickness of 90 μm is used as the outer frame. The inner frame and the outer frame are hot-pressed to form a double-layer frame structure, with the inner frame facing the outer frame adhesive surface, and the width of the overlapping area between the inner frame and the outer frame is set to 2 mm. The five-in-one membrane electrode is assembled and hot-pressed in the order of double-layer frame-proton exchange membrane-double-layer frame. The outer frame adhesive surface of the double-layer frame faces the proton exchange membrane, and the length of the proton exchange membrane beyond the outer edge of the inner frame is set to 3 mm. The gas diffusion layer is bonded to both sides of the five-in-one membrane electrode using a pressure-sensitive adhesive to form a seven-in-one membrane electrode assembly. The gas diffusion layer is located above the inner frame, and the gap between the gas diffusion layer and the outer frame is controlled to be 0.5 mm.

[0057] Embodiment 2 of the present application:

[0058] Example 2 is basically the same as Example 1, the main difference being that the inner frames on both sides of the proton exchange membrane in Example 1 are symmetrically designed, while the inner edges of the inner frames in Example 2 are asymmetrically staggered, with a staggered width of 2 mm.

[0059] Comparative Example 1:

[0060] A 90μm thick PEN hot melt adhesive film is used as the frame, and the five-in-one membrane electrode is formed by assembling and hot pressing in the order of frame-proton exchange membrane-frame. The adhesive surface of the frame faces the proton exchange membrane, and the width of the overlapping area between the proton exchange membrane and the frame is 3mm. The gas diffusion layer is attached to both sides of the five-in-one membrane electrode using a pressure-sensitive adhesive to form a seven-in-one membrane electrode assembly. The gas diffusion layer is located above the proton exchange membrane, and the gap between the gas diffusion layer and the frame is controlled to be 0.5mm.

[0061] Comparative Example 2:

[0062] A PEN hot melt adhesive film with a thickness of 45 μm is used as the inner frame, and a PEN hot melt adhesive film with a thickness of 45 μm is used as the outer frame. The inner frame and the outer frame are hot-pressed to form a double-layer frame structure. The inner edge of the inner frame is 2 mm larger than the inner edge of the outer frame, and the inner frame is tangent to the outer edge of the outer frame. The five-in-one membrane electrode is assembled and hot-pressed in the order of double-layer frame-proton exchange membrane-double-layer frame. The adhesive surface of the frame in the double-layer frame faces the proton exchange membrane, and the length of the proton exchange membrane beyond the outer edge of the inner frame is set to 3 mm. The gas diffusion layer is bonded to both sides of the five-in-one membrane electrode using a pressure-sensitive adhesive to form a seven-in-one membrane electrode assembly. The gas diffusion layer is located above the inner frame, and the gap between the gas diffusion layer and the outer frame is controlled to be 0.5 mm.

[0063] Comparative Example 3:

[0064] Comparative Example 3 is basically the same as Comparative Example 2, the main difference being that the inner frames on both sides of the proton exchange membrane in Comparative Example 2 are symmetrically designed, while the inner edges of the inner frames in Comparative Example 3 are asymmetrically staggered, with a staggered width of 2 mm.

[0065] The test method is:

[0066] The membrane electrode is assembled into a single cell, and after passing the airtightness inspection and being fully activated, a durability cycle test is carried out. The durability cycle test includes two accelerated tests: OCV maintenance and dry-wet cycle. A complete cycle condition includes 10 hours of OCV maintenance and 15 dry-wet cycles.

[0067] The OCV test refers to the process of introducing humidified compressed air and hydrogen with a relative humidity of 30% into the cathode and anode of the battery respectively, with a flow rate ratio of 10 (current density of 0.2A / cm 2 ), the stack pressure was 50 kPa, the battery temperature was 90 °C, and the battery was kept in an open circuit state.

[0068] Among them, the dry-wet cycle test refers to the introduction of compressed air and hydrogen into the cathode and anode of the battery respectively, with a flow rate of 2SLPM, the inlet pressure is normal pressure or no back pressure, the battery temperature is 90°C, and the relative humidity of air and hydrogen is set to cycle between 0% (2min) and the dew point temperature of 90°C (2min).

[0069] The hydrogen permeation current of the membrane electrode assembly was tested every 10 cycles, and the results are as follows:

[0070] Table 1 Comparison of hydrogen permeation current before and after cycling

[0071]

[0072] Table 1 is a comparison of hydrogen permeation currents before and after OCV and dry-wet combination cycles of the embodiments and comparative examples. It can be seen from the table that before the cycle, the hydrogen permeation currents of the membrane electrodes with different sealing frame structures corresponding to the embodiments and comparative examples are similar, and both meet the membrane electrode sealing requirements. Comparing the membrane electrode with built-in sealing frame structure (embodiments 1, 2 and comparative examples 2 and 3) and the membrane electrode with PEM direct sealing structure (comparative example 1), the membrane electrode with PEM direct sealing structure has a hydrogen permeation current of more than 15mA / cm after 20 cycles. 2 The hydrogen permeation current of the membrane electrode with built-in sealed frame structure is higher than 15mA / cm after at least 40 cycles. 2 , indicating that the use of a built-in sealing frame structure can alleviate the failure of membrane electrode sealing, mainly because the use of a built-in sealing frame structure can effectively alleviate the damage to the edge of the sealing frame caused by burrs on the edge of the gas diffusion layer piercing the CCM and longitudinal shear damage.

[0073] Further comparison of different built-in sealed frame structures shows that the hydrogen permeation current of the membrane electrode after 50 cycles of the inner frame structure of the present invention (Examples 1 and 2) is much lower than the hydrogen permeation current of the membrane electrode corresponding to the 10 cycles of the comparative examples 2 and 3, and the hydrogen permeation current of the membrane electrode with the built-in sealed frame structure in the comparative example is higher than 15 mA / cm after 40 or 50 cycles. 2 This indicates that the inner frame structure of the present invention has a better sealing effect. This is mainly due to the fact that during the actual operation of the fuel cell, on the one hand, due to the uneven distribution of water in the membrane electrode, the active area has more water, and the inactive area (sealing frame edge) has less water in the sealing frame; on the other hand, the active area of ​​the membrane electrode CCM membrane is subject to the friction of the gas diffusion layer, while the inactive area (sealing frame edge) is subject to weaker friction constraints of the gas diffusion layer, which leads to a stronger lateral creep of the proton membrane at the edge of the sealing frame. The edge of the membrane electrode sealing frame corresponding to the embodiment adopts a buffer transition layer design instead of an adhesive bonding method, which can effectively overcome the above-mentioned lateral stress and significantly enhance the durability of the membrane electrode sealing frame.

[0074] The above embodiments are only used to illustrate the technical solution of the present application, but not to limit it. The present application is not limited to the exact structure described above and illustrated in the accompanying drawings, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, various changes and modifications made without departing from the concept of the present application should be deemed to belong to the protection scope of the present application.

Claims

1. A fuel cell membrane electrode assembly with a sealed frame structure, characterized in that: include: A catalytic layer coated membrane (10) comprises a proton exchange membrane (11) having a middle portion and an outer portion, wherein the surface of the middle portion is coated with a catalytic layer (12); A gas diffusion layer (20), comprising two sublayers (21) respectively applied to the surfaces of both sides of the catalyst layer coating membrane (10), wherein the sublayers (21) completely cover the middle portion and at least partially cover the outer edge portion; An outer frame (30) is arranged outside the gas diffusion layer (20) and spaced apart from the gas diffusion layer (20), and comprises a first outer frame (31) and a second outer frame (32) that clamp the edge of the proton exchange membrane (11); an inner frame (40) disposed between the outer frame (30) and the gas diffusion layer (20), comprising a first inner frame (41) and a second inner frame (42) located on both sides of the proton exchange membrane (11); The first outer frame (31) and the second outer frame (32) are respectively provided with first recesses (301) on the side facing the gas diffusion layer (20), and the two sub-layers (21) are respectively provided with second recesses (211) on the side facing the outer frame (30); a portion of the first inner frame (41) and the second inner frame (42) are located in the first recess (301), and the other portion is located in the second recess (211); the contact surface between the catalyst layer coating membrane (10) and the outer frame (30) and the contact surface between the gas diffusion layer (20) and the inner frame (40) are both glued, and the contact surface between the catalyst layer coating membrane (10) and the inner frame (40) is in abutment.

2. The membrane electrode assembly according to claim 1, characterized in that: The width of the first inner frame (41) is smaller than the width of the second inner frame (42), and the width of the second inner frame (42) is equal to the sum of the widths of the first recess (301) and the second recess (211).

3. The membrane electrode assembly according to claim 1 or 2, characterized in that: The material of the inner frame (40) is a combination of one or more of PTFE, PEN, PI or PPS film, and the thickness of the inner frame (40) is 10-25 um.

4. The membrane electrode assembly according to claim 3, characterized in that: The material of the outer frame is a combination of one or more of PEN, PI, PET or PPS film, and the thickness of the outer frame is 30-150um.

5. The membrane electrode assembly according to claim 1, characterized in that: The width of the overlapping area between the inner frame (40) and the gas diffusion layer (20) is greater than 2 mm, and the width of the overlapping area between the inner frame (40) and the outer frame (30) is greater than 2 mm.

6. The membrane electrode assembly according to claim 1, characterized in that: The gap between the gas diffusion layer (20) and the outer frame (30) is greater than 0.5 mm.

7. The membrane electrode assembly according to claim 1, characterized in that: The contact surfaces of the catalyst layer coating membrane (10) and the outer frame (30) and the gas diffusion layer (20) and the inner frame (40) are bonded by a combination of one or more of pressure-sensitive adhesive, hot-melt adhesive or UV adhesive.

8. The membrane electrode assembly according to claim 5, characterized in that: The outer edge portion exceeds the inner frame (40) by at least 3 mm.

9. A fuel cell, characterized in that: The fuel cell adopts the membrane electrode assembly described in any one of claims 1-8.

10. A method for preparing a membrane electrode assembly, used for preparing the membrane electrode assembly according to any one of claims 1 to 8, characterized in that: Includes steps: An outer frame (30) and an inner frame (40) are provided, wherein the outer frame (30) comprises a first outer frame (31) and a second outer frame (32) which are symmetrical in the thickness direction and are in a frame shape, wherein the edges of the first outer frame (31) and the second outer frame (32) both comprise a first recess (301) and a third recess (303) in a stepped shape, and the inner frame (40) comprises a first inner frame (41) and a second inner frame (42) in a frame shape; Glue is applied on the surface of one end of the first inner frame (41) and the second inner frame (42) or the step surface of the first recess (301), and the one end of the first inner frame (41) and the second inner frame (42) are respectively placed in the first recess (301) of the first inner frame (41) and the second inner frame (42), and the other end of the first inner frame (41) and the second inner frame (42) are extended out of the first recess (301), and the first outer frame (31) and the first inner frame (41) are respectively pressed together, and the second outer frame (32) and the second inner frame (42) are pressed together, so as to obtain two double-layer frame structures; A catalyst layer coated membrane (10) is provided, comprising a proton exchange membrane (11) having a middle portion and an outer edge portion, wherein the surface of the middle portion is coated with a catalyst layer (12), the sublayer (21) completely covers the middle portion and at least partially covers the outer edge portion, two double-layer frame structures are symmetrically arranged on the outside of the catalyst layer coated membrane (10) to clamp the outer edge portion, wherein the outer edge portion covers the inner frame (40) and extends into the third recess (303) of the outer frame (30), and the contact surface between the first outer frame (31) and the second outer frame (32) and the contact surface between the first outer frame (31), the second outer frame (32) and the catalyst layer coated membrane (10) are glued and bonded; A gas diffusion layer (20) is provided, wherein the gas diffusion layer (20) comprises two sublayers (21), and a second recess (211) in the form of a step is formed at the edge of the sublayer (21); the two sublayers (21) are respectively arranged on both sides of the catalyst layer coated membrane (10), and the other ends of the first inner frame (41) and the second inner frame (42) are respectively located in the second recesses (211) of the two sublayers (21), and the end surfaces of the two sublayers (21) are kept spaced apart from the outer frame (30); The gas diffusion layer (20), the double-layer frame structure and the catalyst layer coated membrane (10) are pressed together to obtain the membrane electrode assembly.

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