Gas diffusion layer, preparation method thereof and battery

Abstract

The invention discloses a gas diffusion layer, a preparation method thereof and a battery. The gas diffusion layer comprises a substrate layer and at least two microporous layers, wherein the at least two microporous layers are sequentially attached to the substrate layer; wherein the at least two microporous layers respectively and independently comprise TiN nano particles and carbon spheres; and the absolute content of TiN in the microporous layer close to the substrate layer is lower than the absolute content of TiN in the microporous layer far away from the substrate layer. According to the gas diffusion layer provided by the invention, the radial consistency of the conductivity is remarkably improved, and the contact resistance between the microporous layer and the catalyst layer is effectively reduced, so that the gas diffusion layer has good conductivity; and meanwhile, one side adjacent to the catalyst layer has enhanced oxidation corrosion resistance, so that the long-term stability and reliability of the battery are improved.

Description

Technical Field

[0001] The invention relates to a gas diffusion layer, a preparation method thereof and a battery. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) is a highly efficient energy conversion device that directly converts the chemical energy between hydrogen and air or pure oxygen into electricity. The membrane electrode assembly (MEA) is the core of the PEMFC and consists of a proton exchange membrane, two catalytic layers, and a gas diffusion layer. The gas diffusion layer (GDL) not only conducts electrons but also plays a key role in uniformly distributing the fuel gas and managing moisture within the cell.

[0003] The GDL is designed to provide an efficient transport path for the reactant gases, ensuring their uniform dispersion on the surface of the catalyst layer and ensuring efficient electron conduction. Highly conductive GDLs help reduce interfacial resistance, thereby improving battery efficiency and operational stability. Typically, a GDL consists of a substrate layer, typically composed of hydrophobic carbon fiber, and a microporous layer, made of a mixture of carbon powder and a hydrophobic agent, adjacent to the catalyst layer.

[0004] However, in practical applications, the incorporation of non-conductive polytetrafluoroethylene (PTFE) into the microporous layer results in lower conductivity on the GDL side near the catalyst layer than on the substrate side, increasing the interfacial contact resistance. This not only compromises the GDL's conductivity, but also the high voltage conditions and potential reverse polarity generated during vehicle starting and stopping processes accelerate oxidative corrosion of the carbon material, particularly the carbon black particles in the microporous layer, thereby weakening its long-term stability and conductivity.

[0005] Therefore, how to construct a gas diffusion layer with high radial uniform conductivity and high resistance to oxidation and corrosion is a key technical issue to further improve the performance and stability of the membrane electrode. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art gas diffusion layer, which suffers from poor electrical conductivity and oxidative corrosion resistance. The invention provides a gas diffusion layer, a preparation method thereof, and a battery. The gas diffusion layer provided by the present invention achieves significantly improved radial uniformity of electrical conductivity, effectively reducing the contact resistance between the microporous layer and the catalytic layer, resulting in excellent electrical conductivity. Furthermore, the side adjacent to the catalytic layer exhibits enhanced oxidative corrosion resistance, improving the long-term stability and reliability of the battery.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The present invention provides a gas diffusion layer, comprising a base layer and at least two microporous layers, wherein the at least two microporous layers are sequentially attached to the base layer;

[0009] Wherein, at least two of the microporous layers independently contain TiN nanoparticles and carbon spheres; and the absolute content of TiN in the microporous layer close to the base layer is lower than the absolute content of TiN in the microporous layer far from the base layer.

[0010] In the present invention, preferably, the gas diffusion layer includes two microporous layers, a microporous layer A close to the base layer and a microporous layer B far from the base layer.

[0011] Wherein, in the microporous layer A, the mass ratio of the TiN nanoparticles to the carbon spheres may be 1:(1.5-4), for example, 1:2.

[0012] Wherein, in the microporous layer B, the mass ratio of the TiN nanoparticles to the carbon spheres may be 1:(0.25-1), for example, 1:0.5.

[0013] The mass ratio of the TiN nanoparticles in the microporous layer A to the TiN nanoparticles in the microporous layer B can be 1:(1.5-4), for example, 1:2. In the present invention, "the absolute content of TiN in the microporous layer close to the substrate layer is lower than the absolute content of TiN in the microporous layer distant from the substrate layer" means that in the gas diffusion layer system, the absolute content of TiN nanoparticles in the microporous layer close to the substrate layer is lower than the absolute content of TiN in the microporous layer distant from the substrate layer.

[0014] The mass ratio of the loading amount of the microporous layer A on the base layer to the loading amount of the microporous layer B on the base layer may be 1:(0.5-1.5), for example, 1:1.

[0015] In the present invention, the total loading of the at least two microporous layers on the base layer can be 0.5-2 mg·cm -2 , for example 1 mg cm -2 .

[0016] In the present invention, the particle size of the TiN nanoparticles may be 40-70 nm, for example, 45 nm.

[0017] In the present invention, the particle size of the carbon spheres may be 20-40 nm, for example, 30 nm.

[0018] In the present invention, preferably, the base layer is carbon paper that has been hydrophobically treated.

[0019] The present invention also provides a method for preparing a gas diffusion layer, which comprises the following steps: coating at least two layers of microporous layer slurry on a base layer, and preparing the gas diffusion layer after heat treatment;

[0020] Wherein, at least two layers of the microporous layer slurry independently contain TiN nanoparticles and carbon balls; and the absolute content of TiN in the microporous layer close to the base layer is lower than the absolute content of TiN in the microporous layer far from the base layer.

[0021] In the present invention, the TiN nanoparticles can be prepared by the following steps: nitriding TiO2 nanoparticles with NH3.

[0022] The particle size of the TiO2 nanoparticles may be 40-60 nm, for example, 50 nm.

[0023] The temperature of the nitriding treatment may be 500-800°C, for example 700°C.

[0024] The nitriding treatment time may be 3-6 hours, for example 5 hours.

[0025] In the present invention, the particle size of the TiN nanoparticles may be 40-70 nm, for example, 45 nm.

[0026] In the present invention, the total loading of the at least two microporous layer slurries on the base layer can be 0.5-2 mg·cm -2 , for example 1 mg cm -2 .

[0027] In the present invention, preferably, two layers of the microporous layer slurry are coated on the base layer, namely, microporous layer slurry A close to the base layer and microporous layer slurry B far from the base layer.

[0028] Wherein, in the microporous layer slurry A, the mass ratio of the TiN nanoparticles to the carbon spheres may be 1:(1.5-4), for example, 1:2.

[0029] Wherein, in the microporous layer slurry B, the mass ratio of the TiN nanoparticles to the carbon spheres may be 1:(0.25-1), for example, 1:0.5.

[0030] The mass ratio of the TiN nanoparticles in the microporous layer slurry A to the TiN nanoparticles in the microporous layer slurry B may be 1:(1.5-4), for example, 1:2.

[0031] The mass ratio of the microporous layer slurry A to the microporous layer slurry B may be 1:(0.5-1.5), for example, 1:1.

[0032] In the present invention, the particle size of the carbon spheres may be 20-40 nm, for example, 30 nm.

[0033] In the present invention, the microporous layer slurry may further include a solvent, preferably isopropyl alcohol and / or water.

[0034] In the present invention, preferably, the base layer is made by brushing polytetrafluoroethylene emulsion on both sides of carbon paper and then heating it.

[0035] The mass percentage concentration of the polytetrafluoroethylene emulsion may be 1-5%, for example, 2%.

[0036] The heating temperature may be 300-400°C, for example 350°C.

[0037] The heating time may be 10-50 min, for example 20 min.

[0038] In the present invention, the heat treatment may be performed in a two-stage heating manner.

[0039] The temperature of the first insulation stage of the two-stage heating process may be 100-150°C, for example, 120°C.

[0040] The first stage of the two-stage heating process may be kept warm for 40-90 minutes, for example, 60 minutes.

[0041] The temperature of the second stage of the two-stage heating process may be 300-400°C, for example, 350°C.

[0042] The second stage of the two-stage heating process may be kept warm for 20-40 minutes, for example, 30 minutes.

[0043] The present invention also provides a gas diffusion layer, which is prepared by the above-mentioned method for preparing the gas diffusion layer.

[0044] The present invention also provides a proton exchange membrane fuel cell, which comprises the above-mentioned gas diffusion layer.

[0045] In the present invention, preferably, the proton exchange membrane fuel cell further includes a catalyst layer, and the catalyst layer is bonded to the gas diffusion layer by being bonded to the microporous layer.

[0046] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0047] The reagents and raw materials used in the present invention are commercially available.

[0048] The positive progress effect of the present invention is:

[0049] The gas diffusion layer provided by the present invention has a radial gradient structure, which significantly improves the radial consistency of the electrical conductivity, effectively reduces the contact resistance between the microporous layer and the catalytic layer, and makes the gas diffusion layer have good electrical conductivity; at the same time, the side adjacent to the catalytic layer has enhanced anti-oxidation and corrosion properties, thereby improving the long-term stability and reliability of the battery.

[0050] The preparation method of the gas diffusion layer provided by the present invention is simple, convenient and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic structural diagram of the membrane electrode assembly composed of the gas diffusion layer prepared in Example 1.

[0052] Figure 2 The XRD patterns of the raw material TiO2 and the prepared TiN nanoparticles in Example 1 are shown.

[0053] Figure 3 The voltammograms of the fuel cells composed of the gas diffusion layers prepared in Example 1, Comparative Example 1 and Comparative Example 2 are shown.

[0054] Figure 4 : are the contact angles of the gas diffusion layers prepared in Example 1, Comparative Example 1 and Comparative Example 2 before and after the corrosion test.

[0055] Figure 5 The electrical conductivity of the gas diffusion layers prepared in Example 1, Comparative Example 1 and Comparative Example 2 before and after the corrosion test.

[0056] Description of reference numerals:

[0057] Basal layer 1

[0058] Microporous layer A2

[0059] Microporous layer B 3

[0060] Catalytic layer 4 DETAILED DESCRIPTION

[0061] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0062] In the embodiments of the present invention, TiO2 nanoparticles were purchased from the exploration platform of Shanghai Titan Technology Co., Ltd., with a particle size of 50 nm; carbon spheres were purchased from Cabot Corporation, model Vulcan XC-72R.

[0063] Example 1

[0064] In this embodiment, a gradient double-layer gas diffusion layer containing TiN nanoparticles is prepared as follows:

[0065] S1, 25cm 2 Carbon paper was treated with hydrophobic treatment: PTFE emulsion (content 2%) was brushed on both sides of the carbon paper, with a total coating amount of 0.4 mg cm -2 , heated at 350℃ for 20min to obtain the base layer.

[0066] S2. Take 500 mg of TiO2 nanoparticles as a precursor, place them in a high-temperature tube furnace, and introduce pure NH3 at a flow rate of 50 sccm to perform NH3 nitridation treatment; control the temperature at 700°C and the nitridation time at 5 hours; cool naturally to obtain TiN nanoparticles. Figure 2 The XRD patterns of the raw material TiO2 and the prepared TiN nanoparticles show that TiN nanoparticles were successfully synthesized in this embodiment. Using the half-width of the XRD characteristic peak and the Scherrer formula 2dsinθ=nλ, the TiN particle size can be calculated to be approximately 45nm.

[0067] S3. The obtained TiN nanoparticles and carbon spheres are prepared into two slurries in different proportions: the mass ratio of TiN nanoparticles to carbon spheres in slurry A is 1:2, and the mass ratio of TiN nanoparticles to carbon spheres in slurry B is 2:1.

[0068] S4: First, apply slurry A on the base layer, and then apply slurry B after drying. That is, slurry A is close to the base layer, and slurry B is close to the catalyst layer. The loading of slurry A and slurry B is 0.5 mg cm -2 , thereby achieving a radial gradient of TiN content in the formed microporous layer.

[0069] S5. The base layer containing the microporous layer slurry prepared in S4 is first heated at 120° C. for 60 min and then heated at 350° C. for 30 min to obtain a gradient double-layer gas diffusion layer.

[0070] The prepared gas diffusion layer is assembled into a membrane electrode assembly. The structural diagram of the gas diffusion layer is shown in FIG. Figure 1 shown.

[0071] Comparative Example 1

[0072] This comparative example prepares a double-layer gas diffusion layer containing PTFE emulsion, specifically as follows:

[0073] S1, 25cm 2 Carbon paper was treated with hydrophobic treatment: PTFE emulsion (content 2%) was brushed on both sides of the carbon paper, with a total coating amount of 0.4 mg cm -2 , and then heated at 350°C for 20 min to obtain the base layer.

[0074] S2. Take 400 mg of carbon powder, add 200 mg of PTFE emulsion, 10 g of isopropyl alcohol, and 10 g of ultrapure water, and stir mechanically for 6 minutes at a speed of 300 r / min to prepare slurry 1. Use the same method to prepare slurry 2.

[0075] S3. Apply slurry 1 on the carbon paper substrate, and then apply slurry 2 thereon after drying.

[0076] S4. The prepared base layer containing the microporous layer slurry is first heated at 120° C. for 60 min and then heated at 350° C. for 30 min to obtain a gas diffusion layer coated with a double microporous layer.

[0077] Comparative Example 2

[0078] The TiN in Example 1 was replaced with commercially available carbon nanotubes (CNTs), and the other steps were the same as in Example 1 to prepare a gradient gas diffusion layer containing (CNTs + carbon spheres).

[0079] Effect Example 1 Electrochemical Performance

[0080] The gas diffusion layers prepared in Example 1 and Comparative Examples 1 and 2 were assembled with CCM membrane electrodes to form a fuel cell.

[0081] The battery voltammetry curve was tested using an FC 5100 Fuel Cell Testing System (CHINO Co., Ltd, Japan). The test conditions were: the battery operating temperature was 60°C, the anode and cathode were supersaturated and humidified, and the temperature was 70°C. The test was performed in constant current mode, and the test was performed after stabilizing for 15 minutes at each current density. The results are shown in Figure 2. Figure 3 shown.

[0082] The EIS spectrum was measured using a KIKUSUI KFM2150 impedance meter. The EIS test frequency was 20 kHz to 200 MHz, and the operating current density of the battery was 200 mA cm -2 , 400mA cm -2 、600mA cm -2 , 800mA cm -2 、1000mA cm -2 The sine wave current amplitude is 250mA. The results are shown in Table 1.

[0083] Table 1 Comparison of ohm impedance values

[0084]

[0085] from Figure 3As can be seen from the volt-ampere curves, the battery performance of Example 1 is significantly improved compared to Comparative Examples 1 and 2. As can be seen from Table 1, Example 1, by providing a double-layer microporous layer and adding different amounts of TiN, can effectively reduce the interface resistance and further achieve efficient electron conduction, thereby improving the performance of the fuel cell.

[0086] Effect Example 2 Anti-oxidation Corrosion Performance

[0087] The gas diffusion layers prepared in Example 1 and Comparative Examples 1 and 2 were respectively subjected to contact angle tests (tested using a contact angle tester) and conductivity tests (tested using a multi-function contact resistance tester), followed by electrochemical CV tests with the potential set at 1.0-1.5 V. After 5000 cycles, the contact angle and conductivity tests were performed again.

[0088] Figure 4 Table 2 below shows the contact angles of three gas diffusion layers before and after corrosion testing. The upper left table shows the contact angle of the gas diffusion layer prepared in Example 1 before the CV test; the upper right table shows the contact angle of the gas diffusion layer prepared in Example 1 after the CV test; the middle left table shows the contact angle of the gas diffusion layer prepared in Comparative Example 1 before the CV test; the middle right table shows the contact angle of the gas diffusion layer prepared in Comparative Example 1 after the CV test; the lower left table shows the contact angle of the gas diffusion layer prepared in Comparative Example 2 before the CV test; and the lower right table shows the contact angle of the gas diffusion layer prepared in Comparative Example 2 after the CV test.

[0089] Table 2 Contact angle test results (tilt angle: 0.00)

[0090]

[0091] from Figure 4 It can be seen that compared with the gas diffusion layer with TiN added in Example 1, the CA values ​​of the gas diffusion layer without TiN added in Comparative Example 1 and the gas diffusion layer with CNT added in Comparative Example 2 after CV testing are significantly reduced, and the gas diffusion layer becomes more hydrophilic.

[0092] Figure 5 The conductivity of three types of gas diffusion layers before and after corrosion test. Figure 5 It can be seen that compared with the gas diffusion layer with TiN added in Example 1, the contact resistance values ​​of the gas diffusion layer without TiN added in Comparative Example 1 and the gas diffusion layer with CNT added in Comparative Example 2 increased more after CV testing.

[0093] This indicates that the gas diffusion layer produced by the present invention exhibits excellent resistance to oxidative corrosion and good stability. This is presumably because the carbon in the gas diffusion layer without TiN and the gas diffusion layer with CNTs is oxidized into oxygen-containing functional groups such as carboxyl groups, increasing hydrophilicity and decreasing electrical conductivity, which reduces oxidative corrosion resistance.

Claims

1. A gas diffusion layer, characterized in that: It comprises a base layer and at least two microporous layers, wherein the at least two microporous layers are sequentially attached to the base layer; Wherein, at least two of the microporous layers independently contain TiN nanoparticles and carbon spheres; and the absolute content of TiN in the microporous layer close to the base layer is lower than the absolute content of TiN in the microporous layer far from the base layer.

2. The gas diffusion layer according to claim 1, wherein The gas diffusion layer comprises two microporous layers, a microporous layer A close to the base layer and a microporous layer B far away from the base layer; and / or, the particle size of the TiN nanoparticles is 40-70 nm, for example 45 nm; and / or, the particle size of the carbon spheres is 20-40 nm, for example 30 nm; And / or, the total loading of the at least two microporous layers on the base layer is 0.5-2 mg·cm -2 , for example 1 mg cm -2 ; And / or, the base layer is carbon paper that has been hydrophobically treated.

3. The gas diffusion layer according to claim 2, wherein: In the microporous layer A, the mass ratio of the TiN nanoparticles to the carbon spheres is 1:(1.5-4), for example, 1:2; and / or, in the microporous layer B, the mass ratio of the TiN nanoparticles to the carbon spheres is 1:(0.25-1), for example, 1:0.5; And / or, the mass ratio of the TiN nanoparticles in the microporous layer A to the TiN nanoparticles in the microporous layer B is 1:(1.5-4), for example 1:2; And / or, the mass ratio of the loading amount of the microporous layer A on the base layer to the loading amount of the microporous layer B on the base layer is 1:(0.5-1.5), for example, 1:

1.

4. A method for preparing a gas diffusion layer, characterized in that: The method comprises the following steps: coating at least two layers of microporous layer slurry on a base layer, and preparing a gas diffusion layer after heat treatment; Wherein, at least two layers of the microporous layer slurry independently contain TiN nanoparticles and carbon balls; and the absolute content of TiN in the microporous layer close to the base layer is lower than the absolute content of TiN in the microporous layer far from the base layer.

5. The method for preparing a gas diffusion layer according to claim 4, wherein: Coating two layers of the microporous layer slurry on the base layer, microporous layer slurry A close to the base layer and microporous layer slurry B away from the base layer; And / or, the TiN nanoparticles are prepared by the following steps: nitriding TiO2 nanoparticles using NH3; and / or, the particle size of the TiN nanoparticles is 40-70 nm, for example 45 nm; and / or, the particle size of the carbon spheres is 20-40 nm, for example 30 nm; And / or, the microporous layer slurry further includes a solvent; the solvent is preferably isopropyl alcohol and / or water; And / or, the total loading of the at least two microporous layer slurries on the base layer is 0.5-2 mg·cm -2 , for example 1 mg cm -2 ; And / or, the base layer is made by brushing polytetrafluoroethylene emulsion on both sides of carbon paper and then heating it; And / or, the heat treatment adopts a two-stage heating method.

6. The method for preparing a gas diffusion layer according to claim 5, wherein: In the microporous layer slurry A, the mass ratio of the TiN nanoparticles to the carbon spheres is 1:(1.5-4), for example, 1:2; and / or, in the microporous layer slurry B, the mass ratio of the TiN nanoparticles to the carbon spheres is 1:(0.25-1), for example, 1:0.5; and / or, the mass ratio of the TiN nanoparticles in the microporous layer slurry A to the TiN nanoparticles in the microporous layer slurry B is 1:(1.5-4), for example 1:2; And / or, the mass ratio of the microporous layer slurry A to the microporous layer slurry B is 1:(0.5-1.5), for example 1:

1.

7. The method for preparing a gas diffusion layer according to claim 5, wherein: The particle size of the TiO2 nanoparticles is 40-60 nm, for example 50 nm; and / or, the temperature of the nitriding treatment is 500-800° C., for example, 700° C.; And / or, the nitriding treatment time is 3-6 hours, for example 5 hours.

8. The method for preparing a gas diffusion layer according to claim 5, wherein: The mass percentage concentration of the polytetrafluoroethylene emulsion is 1-5%, for example 2%; and / or, the heating temperature is 300-400° C., for example 350° C.; And / or, the heating time is 10-50 min, for example 20 min; And / or, the temperature of the first stage of the two-stage heating is 100-150° C., for example, 120° C.; And / or, the first stage of the two-stage heating is kept warm for 40-90 minutes, for example, 60 minutes; And / or, the temperature of the second stage of the two-stage heating is 300-400° C., for example, 350° C.; And / or, the second stage insulation time of the two-stage heating is 20-40 minutes, for example 30 minutes.

9. A gas diffusion layer, characterized in that: The gas diffusion layer is prepared by the method for preparing the gas diffusion layer according to any one of claims 4 to 8.

10. A proton exchange membrane fuel cell, characterized in that: It comprises the gas diffusion layer as described in claim 1-3 or 9; preferably, the proton exchange membrane fuel cell further comprises a catalyst layer, and the catalyst layer is adhered to the gas diffusion layer by being adhered to the microporous layer.

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