Composite proton membrane and method for producing the same

Abstract

The application belongs to the technical field of proton exchange membranes, and particularly discloses a composite proton membrane and a preparation method thereof. The composite proton membrane with a single reinforcing layer and multiple reinforcing layers is obtained by adopting Al2O3 / PTFE reinforcing material as a reinforcing layer and adopting perfluorosulfonic acid resin as a resin layer, and the composite proton membrane has excellent dimensional stability and durability on the premise of maintaining high proton conductivity.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membranes, specifically relating to a composite proton membrane and its preparation method. Background Technology

[0002] With the advancement of technology and the development of the times, hydrogen fuel cells have the advantages of high power density, energy saving, and zero pollution; and are expected to replace traditional energy sources such as oil and coal, achieving sustainable energy development. Among them, the proton exchange membrane (PEM), as one of the core materials of hydrogen fuel cells, acts as a channel for proton transfer, primarily playing a role in blocking hydrogen / air during the operation of the fuel cell. Its performance plays a decisive role in the lifespan and performance of the fuel cell. Currently, there are various types of PEMs, with the most widely used being the DuPont Nafion perfluorosulfonic acid (PFSA) PEM. It possesses excellent proton conductivity, high gas barrier efficiency, and high chemical stability. However, the homogeneous membrane has low mechanical properties under ultra-thin conditions, making it unsuitable for practical production; simultaneously, its dimensional change rate is unstable, and stress concentration points easily form on the PEM, causing battery failure and other problems, seriously affecting the performance and lifespan of the PFSA PEM. To address these issues, ePTFE microporous membranes are used as reinforcing substrates, and ion exchange resins are coated onto the surface of the reinforcing material and impregnated within it, forming a composite membrane with a "sandwich" structure of functional resin-reinforcing material + functional resin-functional resin. The ion exchange resins impregnate the microporous membrane to form proton conduction channels, ensuring proton conduction performance while significantly improving the mechanical properties and dimensional stability of the proton exchange membrane.

[0003] In recent years, the fuel cell market has increasingly shifted towards high-output power operation. To meet market demands and enhance product competitiveness, new requirements have been placed on proton exchange membranes (PEMs): 1. The use of perfluorosulfonic acid resins with high exchange capacity (IEC); 2. Further reduction in thickness. The higher the IEC of the resin, the greater the water absorption and swelling of the proton exchange membrane, and the less stable its dimensions. Although existing reinforcing materials play a role in the dimensional stability of the resin, their binding effect on high-IEC resins remains limited, resulting in poor dimensional stability of high-IEC proton exchange membranes. This, in turn, affects the lifespan of the proton exchange membrane, which seriously hinders the development of the fuel cell industry. Therefore, solving the problem of poor dimensional stability of high-IEC proton exchange membranes is one of the key focuses of current research on composite perfluorosulfonic acid proton exchange membranes. Summary of the Invention

[0004] The purpose of this invention is to provide a composite proton exchange membrane and its preparation method. The composite proton exchange membrane is obtained by using Al2O3 / PTFE reinforcing material as the reinforcing layer and perfluorosulfonic acid resin as the resin layer. The composite proton exchange membrane has excellent dimensional stability and durability while maintaining high proton conductivity.

[0005] A composite proton exchange membrane includes a reinforcing layer and a resin layer;

[0006] The reinforcing layer is an Al2O3 / PTFE reinforcing material, and the resin layer is a perfluorosulfonic acid resin.

[0007] The Al2O3 / PTFE reinforced material is composed of Al2O3 nanoparticles and PTFE resin powder; wherein the Al2O3 nanoparticles account for 1wt%-10wt% of the mass of the PTFE resin powder.

[0008] The reinforcing layer consists of 1-5 layers, preferably 1-3 layers;

[0009] The IEC of the perfluorosulfonic acid resin is 0.8-1.8 mmol / g.

[0010] Preferably, when the reinforcing layer is a single layer, the IEC of the perfluorosulfonic acid resin is 1.0-1.4 mmol / g;

[0011] When there is more than one reinforcing layer, the IEC of the perfluorosulfonic acid resin is 1.4-1.6 mmol / g;

[0012] The composite proton exchange membrane has a dimensional change rate of ≤5% in the TD direction and a dimensional change rate of ≤5% in the MD direction; the lifetime of the composite proton exchange membrane is ≥500h.

[0013] The Al2O3 / PTFE reinforced material has a thickness of 2~20μm and a porosity of 65-90%, and the Al2O3 nanoparticles have a particle size range of 10-100nm.

[0014] The perfluorosulfonic acid resin has a number-average molecular weight of 100,000 to 900,000.

[0015] The thickness of the composite proton membrane is 5-100 μm, preferably 5-50 μm;

[0016] The thickness of the reinforcing layer accounts for 5%-80%, preferably 15%-70%.

[0017] Preferably, when there are two reinforcing layers, in one reinforcing layer, Al2O3 nanoparticles account for 1wt%-3wt% of the mass of PTFE resin powder; in the other reinforcing layer, Al2O3 nanoparticles account for 3wt%-8wt% of the mass of PTFE resin powder.

[0018] This invention presents a composite proton exchange membrane obtained by using Al2O3 / PTFE reinforcing material as the reinforcing layer and perfluorosulfonic acid resin as the resin layer. This composite proton exchange membrane maintains high proton conductivity while also exhibiting excellent dimensional stability and durability. This is because the Al2O3 / PTFE reinforcing material not only provides mechanical support but also forms hydrogen bonds with the sulfonic acid groups of PFSA (perfluorosulfonic acid resin) through its surface hydroxyl groups, thereby enhancing the microscopic bonding force between the perfluorosulfonic acid resin and the Al2O3 / PTFE reinforcing material and inhibiting PFSA swelling.

[0019] This invention also provides a method for preparing the above-mentioned composite proton exchange membrane, comprising:

[0020] S1. The perfluorosulfonic acid resin solution is coated onto the surface of the loaded film by casting and scraping.

[0021] S2. Lay a layer of Al2O3 / PTFE reinforcing material on the perfluorosulfonic acid resin solution;

[0022] S3. Cast and coat another layer of perfluorosulfonic acid resin solution onto the Al2O3 / PTFE reinforced material;

[0023] S4. Repeat steps S2 and S3 until the preset number of layers is reached;

[0024] S5. Curing and detachment of the loaded membrane yields a composite proton exchange membrane.

[0025] The curing temperature is 25-220℃, and the curing time is 1-4h.

[0026] This invention obtains a multi-reinforced composite proton exchange membrane with multiple reinforcing layers by repeatedly casting Al2O3 / PTFE reinforced material, thereby further improving the dimensional stability of the composite proton exchange membrane.

[0027] Compared with the prior art, the present invention has the following effects:

[0028] 1. This invention overcomes the trade-off between proton conductivity and dimensional stability in composite proton membranes by using Al2O3 / PTFE reinforcing material as the reinforcing layer and perfluorosulfonic acid resin as the resin layer. While maintaining high proton conductivity, it also has excellent dimensional stability and durability.

[0029] 2. This invention obtains a multi-reinforced composite proton exchange membrane with multiple reinforcing layers by repeatedly casting Al2O3 / PTFE reinforcing material. This overcomes the problems of poor bonding between the resin layer and the reinforcing layer and easy delamination in the multi-layer composite process, reduces the stress concentration points that occur during the operation of the composite proton exchange membrane, and thus improves the durability of the composite proton exchange membrane. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope cross-sectional image of a traditional dual-enhanced composite proton exchange membrane.

[0031] Figure 2 This is a scanning electron microscope cross-sectional image of the dual-enhanced composite proton membrane prepared in Example 8. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments, but these embodiments do not limit the implementation of the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available products.

[0033] In the following examples and comparative examples, the preparation method of the Al2O3 / PTFE reinforced material includes the following steps:

[0034] The preparation method of the 16μm thick Al2O3 / PTFE reinforced material refers to Example 1 of patent CN119529453A, the difference being: during the calendering process, the extruded sheet is pressed into a calendered film with a thickness of 550μm under the action of two pressure rollers; Al2O3 nanoparticles account for 5% of the mass of PTFE resin powder, and an Al2O3 / PTFE reinforced material with a thickness of 16μm and a porosity of 88% is prepared.

[0035] The preparation method of the 2μm thick Al2O3 / PTFE reinforced material differs from the above in the calendering process, longitudinal stretching, and transverse widening process, resulting in an Al2O3 / PTFE reinforced material with a thickness of 2μm and a porosity of 88%. Specifically, the calendering process involves pressing the extruded sheet into a 100μm thick calendered film strip under the action of two pressure rollers; the longitudinal stretching ratio is 25 times; and the transverse widening ratio is 15 times.

[0036] The solid content of perfluorosulfonic acid resin in the following perfluorosulfonic acid resin solution is 13%, and the solvent is an ethanol / water solution with a volume ratio of 1:1.

[0037] In the following examples and comparative examples, the dimensional change rate test method refers to GB / T20042.3-2022, the normal conductivity test method adopts the four-probe method, and the durability test method refers to the fuel cell and component testing standard (DOE-2017) published by the U.S. Department of Energy (DOE) Automotive Fuel Cell Technology Team.

[0038] Example 1:

[0039] (1) Select a perfluorosulfonic acid resin with an IEC of 0.9 mmol / g (number average molecular weight of 400,000) and apply the prepared perfluorosulfonic acid resin solution to the surface of the loaded membrane by casting and scraping.

[0040] (2) A layer of Al2O3 / PTFE reinforcing material with a thickness of 16μm is laid on the perfluorosulfonic acid resin solution;

[0041] (3) On the basis of step (2), another layer of perfluorosulfonic acid resin solution is cast and coated;

[0042] (4) Place it in an oven for curing (curing time is 2 hours and curing temperature is 190℃). After the load film is removed, a uniform composite proton membrane with a thickness of 15μm is obtained.

[0043] After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity and durability were tested, and the results are shown in Table 1.

[0044] Example 2:

[0045] A perfluorosulfonic acid resin with an IEC of 1.1 mmol / g (number-average molecular weight of 410,000) was selected, and the rest of the preparation process was the same as in Example 1. After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity, and durability were tested, and the results are shown in Table 1.

[0046] Example 3:

[0047] A perfluorosulfonic acid resin with an IEC of 1.2 mmol / g (number-average molecular weight of 410,000) was selected, and the rest of the preparation process was the same as in Example 1. After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity, and durability were tested, and the results are shown in Table 1.

[0048] Example 4:

[0049] A perfluorosulfonic acid resin with an IEC of 1.3 mmol / g (number-average molecular weight of 400,000) was selected, and the rest of the preparation process was the same as in Example 1. After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity, and durability were tested.

[0050] Example 5:

[0051] A perfluorosulfonic acid resin with an IEC of 1.4 mmol / g (number-average molecular weight of 410,000) was selected, and the rest of the preparation process was the same as in Example 1. After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity, and durability were tested, and the results are shown in Table 1.

[0052] Example 6:

[0053] A perfluorosulfonic acid resin with an IEC of 1.5 mmol / g (number-average molecular weight of 410,000) was selected, and the rest of the preparation process was the same as in Example 1. After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity, and durability were tested, and the results are shown in Table 1.

[0054] Example 7:

[0055] (1) Select a perfluorosulfonic acid resin with an IEC of 1.5 mmol / g (number average molecular weight of 400,000) and apply the prepared perfluorosulfonic acid resin solution to the surface of the loaded membrane by casting and scraping.

[0056] (2) A layer of Al2O3 / PTFE reinforcing material with a thickness of 2μm is laid on the perfluorosulfonic acid resin solution;

[0057] (3) Based on step (2), another layer of perfluorosulfonic acid resin solution is cast and coated;

[0058] (4) Repeat steps (2) and (3) once to complete the double-enhanced proton membrane coating;

[0059] (5) Place it in an oven for curing (curing time is 2h, curing temperature is 190℃). After the load film is removed, a uniform double-reinforced composite proton membrane with a thickness of 5μm is obtained.

[0060] After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity and durability were tested, and the results are shown in Table 1.

[0061] Example 8:

[0062] (1) Select a perfluorosulfonic acid resin with an IEC of 1.5 mmol / g (number average molecular weight of 400,000) and apply the prepared perfluorosulfonic acid resin solution to the surface of the loaded membrane by casting and scraping.

[0063] (2) A layer of Al2O3 / PTFE reinforcing material with a thickness of 16 μm is laid on the perfluorosulfonic acid resin solution;

[0064] (3) Based on step (2), another layer of perfluorosulfonic acid resin solution is cast and coated;

[0065] (4) Repeat steps (2) and (3) once to complete the double-enhanced proton membrane coating;

[0066] (5) Place it in an oven for curing (curing time is 2h, curing temperature is 190℃). After the load film is removed, a uniform double-reinforced composite proton membrane with a thickness of 15μm is obtained.

[0067] After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity and durability were tested, and the results are shown in Table 1.

[0068] Example 9:

[0069] (1) Select a perfluorosulfonic acid resin with an IEC of 1.5 mmol / g (number average molecular weight of 400,000) and apply the prepared perfluorosulfonic acid resin solution to the surface of the loaded membrane by casting and scraping.

[0070] (2) An Al2O3 / PTFE reinforcing material is laid flat on a perfluorosulfonic acid resin solution as the first reinforcing layer, wherein the Al2O3 / PTFE reinforcing material has a thickness of 2 μm and the Al2O3 nanoparticles account for 2.5% of the mass of the PTFE resin powder;

[0071] (3) Based on step (2), another layer of perfluorosulfonic acid resin solution is cast and coated;

[0072] (4) An Al2O3 / PTFE reinforcing material is laid flat on a perfluorosulfonic acid resin solution as a second reinforcing layer, and a layer of perfluorosulfonic acid resin solution is cast and coated to complete the double-reinforced proton exchange membrane coating; the thickness of the Al2O3 / PTFE reinforcing material is 2μm, and the Al2O3 nanoparticles account for 5% of the mass of the PTFE resin powder;

[0073] (5) Place it in an oven for curing (curing time is 2h, curing temperature is 190℃). After the load film is removed, a uniform double-reinforced composite proton membrane with a thickness of 5μm is obtained.

[0074] After the composite proton exchange membrane was prepared, its performance, including dimensional change rate, normal conductivity, and durability, was tested. The results are shown in Table 1.

[0075] Comparative Example 1:

[0076] (1) Select a perfluorosulfonic acid resin with an IEC of 1.4 mmol / g (number average molecular weight of 410,000) and apply the prepared perfluorosulfonic acid resin solution to the surface of the loaded membrane by casting and scraping.

[0077] (2) A layer of conventional ePTFE reinforcing material without nano-Al2O3 is laid flat on the perfluorosulfonic acid resin solution;

[0078] (3) Based on step (2), another layer of perfluorosulfonic acid resin solution is cast and coated;

[0079] (4) The ePTFE reinforcing material impregnated with the above perfluorosulfonic acid resin solution was placed in an oven for curing (curing time was 2 hours and curing temperature was 190°C). After the load membrane was removed, a uniform composite proton membrane with a thickness of 15 μm was obtained.

[0080] After the composite proton exchange membrane was prepared, its dimensional change rate, normal conductivity and durability were tested, and the results are shown in Table 1.

[0081] Comparative Example 2:

[0082] This comparative example uses sulfonated polyether ether ketone resin with an IEC value of 1.4 mmol / g (number average molecular weight of 15,000), and the rest of the preparation process is the same as in Example 5.

[0083] Comparative Example 3:

[0084] The Al2O3 content in the Al2O3 / PTFE reinforced material of this comparative example is 15%, and the rest of the preparation process is the same as in Example 5.

[0085] Table 1 Performance Data

[0086]

[0087] Examples 1-6 and Comparative Example 1 are all composite proton exchange membrane samples of the same thickness. Examples 1-6 use a different perfluorosulfonic acid resin (IEC), Examples 1-7 use Al2O3 / PTFE reinforcement material, while Comparative Example 1 uses conventional ePTFE without Al2O3 nanoparticles. Furthermore, Example 7 uses a 2-micrometer-thick reinforcement material and a dual-reinforcement method to prepare a 5-micrometer-thick proton exchange membrane.

[0088] Comparing the data from Examples 1-6, it can be seen that as the resin IEC increases, the dimensional change rate deteriorates while the normal proton conductivity increases. When the IEC ≤ 1.4 mmol / g, the dimensional change rate can be controlled at a relatively low level, and the lifespan is above the U.S. Department of Energy (DOE) standard. When the IEC reaches 1.5 mmol / g, the dimensional change rate exceeds 7.5%, resulting in a significant decrease in the durability of the composite proton exchange membrane.

[0089] Compared with Example 5 and Comparative Example 1, the composite proton exchange membrane prepared with the same IEC resin, the composite proton exchange membrane using Al2O3 / PTFE reinforcement material has better dimensional stability and a lifespan more than three times that of the composite proton exchange membrane prepared in Comparative Example 1. This indicates that Al2O3 / PTFE reinforcement material effectively improves the dimensional stability of the composite proton exchange membrane, solves the problem of large dimensional change rate of high IEC (≤1.4mmol / g) composite proton exchange membranes, and improves the proton conductivity and durability of the composite proton exchange membrane, meeting the market demand for high-power output conditions.

[0090] Comparing Examples 6 and 8, composite proton exchange membranes were prepared using the same IEC (1.5 mmol / g) resin. Example 6 used a single-reinforcement layer with a thickness of 15 micrometers, while Example 8 used a double-reinforcement layer with the same thickness of 15 micrometers. Data comparison shows that preparing a 15-micrometer composite proton exchange membrane using a double-reinforcement method improves the dimensional stability of the high-exchange-capacity composite proton exchange membrane, thereby enhancing its durability. For traditional multi-reinforcement composite proton exchange membranes (i.e., using ePTFE as the reinforcement layer, with the rest of the preparation process the same as in Example 8), the multilayer composite preparation technique leads to obvious pores in the resin layer and reinforcement layer (e.g., ...). Figure 1 As shown), under repeated cyclic stress, delamination is prone to occur, thereby reducing the durability of the composite proton exchange membrane; while Example 8 (as shown) Figure 2 As shown in the figure, compared with Example 6, its durability not only did not decrease, but was significantly improved.

[0091] Example 7 uses a double-reinforced composite proton exchange membrane with a single-layer reinforcement layer thickness of 2 micrometers and a total thickness of 5 micrometers. The data shows that the ultrathin composite proton exchange membrane with a total thickness of 5 micrometers prepared by double reinforcement can significantly increase the electrochemical performance of the composite proton exchange membrane by reducing the thickness and using high exchange capacity resin, which can further meet the market demand for high-output operating conditions.

[0092] Compared to Example 7, in Example 9, the Al2O3 content in one reinforcing layer is 2.5%, and the Al2O3 content in the other reinforcing layer is 5%. As shown in Table 1, Example 9 not only improves the swelling resistance of the composite proton membrane, but also improves its normal proton conductivity.

[0093] Comparing Example 5 and Comparative Example 2, composite proton exchange membranes were prepared using the same IEC resin, with Example 5 using perfluorosulfonic acid resin and Comparative Example 2 using sulfonated polyetheretherketone resin. Data comparison shows that although the dimensional change rates of the same IEC resin but different resins are similar, the durability of the composite proton exchange membrane prepared with sulfonated polyetheretherketone resin is far inferior to that with perfluorosulfonic acid resin. This is mainly because the sulfonic acid groups in perfluorosulfonic acid resin are polymerized under specific temperature and pressure conditions, while the sulfonic acid groups in sulfonated polyetheretherketone resin are grafted on later through sulfonation, resulting in a much less stable structure compared to perfluorosulfonic acid resin.

[0094] The data from Comparative Example 3 show that when the amount of Al2O3 added is too high, the normal conductivity and durability of the prepared composite proton exchange membrane are significantly reduced. The main reason is that when the amount of Al2O3 added is too high, too many hydrogen bonds are formed between Al2O3 and the sulfonic acid groups of the perfluorosulfonic acid resin, occupying more proton transport active sites and hindering proton conduction. In addition, due to its high surface energy, nano-sized Al2O3 is also prone to agglomeration and obvious phase separation with PTFE and PFSA. This can easily cause stress concentration points during the durability test, resulting in a significant reduction in the durability of the composite proton exchange membrane.

Claims

1. A composite proton exchange membrane, characterized in that, Includes a reinforcing layer and a resin layer; The reinforcing layer is an Al2O3 / PTFE reinforcing material, and the resin layer is a perfluorosulfonic acid resin. The Al2O3 / PTFE reinforced material is composed of Al2O3 nanoparticles and PTFE resin powder; wherein the Al2O3 nanoparticles account for 1wt%-10wt% of the mass of the PTFE resin powder. The reinforcing layer consists of 2-5 layers, and the IEC of the perfluorosulfonic acid resin is 1.4-1.6 mmol / g; When there are two reinforcing layers, in one reinforcing layer, Al2O3 nanoparticles account for 1wt%-3wt% of the PTFE resin powder mass; in the other reinforcing layer, Al2O3 nanoparticles account for 3wt%-8wt% of the PTFE resin powder mass. The composite proton exchange membrane has a dimensional change rate of ≤5% in the TD direction and a dimensional change rate of ≤5% in the MD direction; the lifetime of the composite proton exchange membrane is ≥500h.

2. The composite proton exchange membrane according to claim 1, characterized in that, The reinforcement layer consists of 2-3 layers.

3. The composite proton exchange membrane according to claim 1, characterized in that, The Al2O3 / PTFE reinforced material has a thickness of 2~20μm and a porosity of 65-90%, and the Al2O3 nanoparticles have a particle size range of 10-100nm.

4. The composite proton exchange membrane according to claim 1, characterized in that, The thickness of the composite proton membrane is 5-100 μm; The thickness of the reinforcing layer accounts for 5%-80%.

5. A method for preparing a composite proton exchange membrane as described in any one of claims 1-4, characterized in that, include, S1. The perfluorosulfonic acid resin solution is coated onto the surface of the loaded film by casting and scraping. S2. Lay a layer of Al2O3 / PTFE reinforcing material on the perfluorosulfonic acid resin solution; S3. Cast and coat another layer of perfluorosulfonic acid resin solution onto the Al2O3 / PTFE reinforced material; S4. Repeat steps S2 and S3 until the preset number of layers is reached; S5. Curing and detachment of the loaded membrane yields a composite proton exchange membrane.

6. The method for preparing the composite proton exchange membrane according to claim 5, characterized in that, The curing temperature is 25-220℃, and the curing time is 1-4h.

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