A method, device and application for evaluating the interface contact state of a gas diffusion layer

Abstract

The application relates to a gas diffusion layer interface contact state evaluation method, device and application, and the evaluation method comprises the following steps: measuring and calculating the substrate layer resistance, the microporous layer resistance and the interface resistance in a gas diffusion layer sample to be evaluated, the interface resistance being the interface resistance between the substrate layer and the microporous layer; measuring and calculating the contact area between the carbon particles of the microporous layer and the carbon fibers of the substrate layer in the gas diffusion layer sample to be evaluated; calculating the equivalent contact resistance between the carbon particles of the microporous layer and the carbon fibers of the substrate layer based on the contact area and the interface resistance; and determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance. Compared with the prior art, the application proposes the equivalent contact resistance of the carbon fibers and carbon black particles in the gas diffusion layer, considers the interface contact area and the interface contact resistance, and therefore, the application can more accurately reflect the real interface contact state between the substrate layer and the microporous layer in the gas diffusion layer of a fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a gas diffusion layer interface contact state evaluation method, device and application. BACKGROUND

[0002] A fuel cell is mainly composed of bipolar plates (BPP), gas diffusion layers (GDL), catalyst layers, proton exchange membranes and the like, which are alternately stacked and assembled, so that there are many interfaces in the fuel cell. Interface resistance and interface attenuation are key factors affecting the performance and service life of the fuel cell.

[0003] In general design, a group of stacks is formed by a number of single cells connected in series, the component located at the center of the single cell is a proton exchange membrane, the two sides of the membrane are coated with a catalyst layer, the two sides of the catalyst layer are gas diffusion layers, and the outermost side of the single cell is two bipolar plates. The seven-layer structure constitutes a single cell. Because the gas diffusion layer is located in the middle of the single cell and serves to connect the bipolar plates and the catalyst layer, its performance has a great influence on the overall performance of the fuel cell.

[0004] The gas diffusion layer (GDL) is usually composed of a substrate layer and a microporous layer. After the substrate layer is subjected to hydrophobic treatment, a single or multiple microporous layers are coated thereon to form the gas diffusion layer. The substrate layer is usually composed of anisotropic carbon fiber stacks and directly contacts the bipolar plate. The microporous layer is composed of conductive carbon black and hydrophobic material and directly contacts the catalyst layer. In the prior art, the interface contact state of the gas diffusion layer is mainly judged by interface resistance or interface topography change. However, the interface between the substrate layer and the microporous layer of the gas diffusion layer is difficult to separate, and there are chemical corrosion, deformation and the like under service conditions, so the macroscopic interface resistance cannot effectively reflect the interface contact state. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a gas diffusion layer interface contact state evaluation method, device and application.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A gas diffusion layer interface contact state evaluation method, comprising the following steps:

[0008] The substrate layer resistance, microporous layer resistance and interface resistance in the gas diffusion layer sample to be evaluated are measured and calculated, and the interface resistance is the interface resistance between the substrate layer and the microporous layer;

[0009] The contact area between the microporous layer carbon particles and the substrate layer carbon fibers in the gas diffusion layer sample to be evaluated is measured and calculated;

[0010] calculating the equivalent contact resistance of the microporous layer carbon particles and the substrate layer carbon fibers based on the contact area and the interface resistance;

[0011] determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

[0012] Further, the calculation of the substrate layer resistance in the gas diffusion layer is specifically:

[0013] For the gas diffusion layer sample to be evaluated, the thickness t0 of the substrate layer and the thickness t1 of the microporous layer are determined;

[0014] A substrate layer sample with a thickness t0 is prepared, and the resistance of the sample is measured as the substrate layer resistance R G .

[0015] Further, the calculation of the microporous layer resistance in the gas diffusion layer is specifically:

[0016] The resistance R1 of the gas diffusion layer sample to be evaluated is measured;

[0017] A gas diffusion layer sample with a substrate layer thickness t0 and a microporous layer thickness t2 is prepared, and the resistance R2 of the sample is measured;

[0018] The microporous layer resistance in the gas diffusion layer sample to be evaluated is calculated by the following formula:

[0019]

[0020] wherein R M represents the microporous layer resistance in the gas diffusion layer sample to be evaluated.

[0021] Further, the calculation of the interface resistance in the gas diffusion layer is specifically:

[0022] The interface resistance in the gas diffusion layer sample to be evaluated is calculated by the following formula:

[0023] R G-M = R1-R G -R M

[0024] wherein R G-M represents the interface resistance in the gas diffusion layer sample to be evaluated.

[0025] Further, the contact area of the microporous layer carbon particles and the substrate layer carbon fibers in the gas diffusion layer sample to be evaluated is calculated by the micro-CT method.

[0026] Further, the calculation of the equivalent contact resistance of the microporous layer carbon particles and the substrate layer carbon fibers based on the contact area and the interface resistance is specifically:

[0027]

[0028] wherein S f-c represents the contact area, R G-M represents the interface resistance, represents the equivalent contact resistance.

[0029] A gas diffusion layer interface contact state evaluation device, comprising:

[0030] a first measurement unit for measuring the substrate layer resistance, the microporous layer resistance and the interface resistance in the gas diffusion layer sample to be evaluated, the interface resistance being the interface resistance between the substrate layer and the microporous layer;

[0031] a second measurement unit for measuring the contact area between the carbon particles in the microporous layer and the carbon fibers in the substrate layer in the gas diffusion layer sample to be evaluated;

[0032] an operation unit for calculating the equivalent contact resistance between the carbon particles in the microporous layer and the carbon fibers in the substrate layer based on the contact area and the interface resistance;

[0033] an output unit for determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

[0034] The application of a gas diffusion layer interface contact state evaluation method in the research, production and testing of gas diffusion layers.

[0035] Compared with the prior art, the application has the following beneficial effects:

[0036] The application proposes the equivalent contact resistance between the carbon fibers and the carbon black particles in the gas diffusion layer, characterizes the contact state between the microporous layer and the substrate in the gas diffusion layer, and considers the interface contact area and the interface contact resistance, so that it can more accurately reflect the real interface contact state between the substrate layer and the microporous layer in the gas diffusion layer of a fuel cell. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the gas diffusion layer micro-morphology and surface resistance;

[0038] Figure 2 is a schematic diagram of the contact morphology of the carbon fibers and the carbon black particles;

[0039] Reference signs: 1, substrate layer, 2, interface, 3, microporous layer, 4, carbon fiber layer, 5, carbon black particle cluster. DETAILED DESCRIPTION

[0040] The application will be described in greater detail with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments. The protection scope of the application is not limited to the following embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor should be within the protection scope of the application.

[0041] As used in this description, the terms "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the application. The appearances of the phrase "in one embodiment" or "in an embodiment" in various places in the description are not necessarily all referring to the same embodiment, nor are they necessarily referring to a single implementation. As such, the terms "including," "comprising," and "having" are intended to be broad and encompass the various embodiments of the application.

[0042] The specification provides method operation steps as an example or flowchart, but more or less operation steps can be included based on conventional or non-creative labor. The order of the steps listed in the embodiments is only one of the many execution orders of the steps, and does not represent the only execution order. In actual system or server product execution, the method order shown in the embodiments or the drawings can be executed in sequence or in parallel (such as parallel processor or multi-threaded environment) or the execution order of the steps without time limit is adjusted.

[0043] The gas diffusion layer is generally composed of a substrate layer and a microporous layer. After the substrate layer is subjected to hydrophobic treatment, a single or multiple microporous layers are coated thereon to form the gas diffusion layer. As shown in Figure 1 The interface 2 between the substrate layer 1 and the microporous layer 3 in the micro-morphology, and thus the surface resistance (R i ) of the gas diffusion layer includes the substrate layer resistance (R G ), the microporous layer resistance (R M ), and the interface resistance (R G-M ) between the substrate layer and the microporous layer, satisfying the following relationship:

[0044] R i =R G +R M +R G-M

[0045] Generally, the substrate layer is a carbon fiber material, and the microporous layer is formed by mixing conductive carbon black and hydrophobic material. The contact morphology of carbon fibers and carbon black particles is as shown in Figure 2As shown, the carbon black particles are agglomerated in clusters, and the carbon black particle clusters 5 are connected to the carbon fiber layer 4, Figure 2 The source document is: H. Sadeghifar, N. Djilali, M. Bahrami, Counter-intuitive reduction of thermal contact resistance with porosity: A case study of polymer electrolyte membrane fuel cells, International Journal of Hydrogen Energy 41 (2016) 6833-6841. The interface resistance (R G-M ) between the substrate and the microporous layer is derived from the contact between the carbon black particles and the carbon fibers, and thus can be regarded as the contact resistance (R f-c，i ) between the carbon black particles and the carbon fibers in parallel to obtain the interface resistance (R G-M ), which satisfies the following relationship:

[0046]

[0047] Where N f-c is the number of carbon particles in contact with the carbon fibers.

[0048] Considering that N f-c is proportional to the interface contact area S f-c , the above formula can be rewritten as:

[0049]

[0050] Where, is the equivalent contact resistance of the carbon fibers and the carbon black particles.

[0051] Compared with the macroscopic interface resistance, the equivalent contact resistance of the carbon fibers and the carbon black particles in the gas diffusion layer proposed in the present application characterizes the contact state between the microporous layer and the substrate in the gas diffusion layer, and takes into account the interface contact area and the interface contact resistance, so it can more accurately reflect the real contact state between the substrate layer and the microporous layer in the gas diffusion layer of the fuel cell.

[0052] Based on the above equivalent contact resistance, the present application provides a method for evaluating the interface contact state of a gas diffusion layer, comprising the following steps:

[0053] S1, calculating the resistance of the substrate layer, the resistance of the microporous layer and the interface resistance in the gas diffusion layer sample to be evaluated, and the interface resistance is the interface resistance between the substrate layer and the microporous layer;

[0054] (1) For the gas diffusion layer sample to be evaluated, denoted as sample 1, determine the substrate layer thickness t0 and the microporous layer thickness t1, wherein the substrate layer thickness and the microporous layer thickness can be determined by means such as a thickness gauge or micro-CT.

[0055] (2) Prepare a substrate layer sample with a thickness of t0, denoted as sample 2, and measure the resistance of the sample as the substrate layer resistance R G , i.e. the surface resistance of sample 2 is measured by the resistance experiment method.

[0056] (3) Measure the resistance R1 of the gas diffusion layer sample to be evaluated, i.e. the surface resistance of sample 1 is measured by the resistance experiment method; prepare a gas diffusion layer sample with a substrate layer thickness of t0 and a microporous layer thickness of t2, denoted as sample 3, and the value of t2 needs to be different, preferably the difference between the two is in the range of 20 μm to 50 μm, and measure the resistance R2 of the sample, i.e. the surface resistance of sample 3 is measured by the resistance experiment method; calculate the microporous layer resistance in the gas diffusion layer sample to be evaluated by the following formula:

[0057]

[0058] , wherein R M represents the microporous layer resistance in the gas diffusion layer sample to be evaluated.

[0059] (4) Calculate the interface resistance in the gas diffusion layer sample to be evaluated by the following formula:

[0060] R G-M = R1-R G -R M

[0061] , wherein R G-M represents the interface resistance in the gas diffusion layer sample to be evaluated.

[0062] S2, calculate the contact area of the microporous layer carbon particles and the substrate layer carbon fibers in the gas diffusion layer sample to be evaluated;

[0063] Specifically, the micro-CT method can be used to calculate the contact area S f-c of the microporous layer carbon particles and the substrate layer carbon fibers in the gas diffusion layer sample to be evaluated (sample 1).

[0064] S3, calculate the equivalent contact resistance of the microporous layer carbon particles and the substrate layer carbon fibers based on the contact area and the interface resistance;

[0065]

[0066] , wherein S f-c represents the contact area, and R G-M represents the interface resistance, The equivalent contact resistance of carbon fiber and carbon black particle.

[0067] S4, determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

[0068] The equivalent contact resistance of carbon fiber and carbon black particle reflects the real contact state between the substrate layer and the microporous layer of the fuel cell gas diffusion layer. The larger the equivalent contact resistance of carbon fiber and carbon black particle, the worse the contact state. The smaller the equivalent contact resistance of carbon fiber and carbon black particle, the better the contact state. With the help of the equivalent contact resistance of carbon fiber and carbon black particle, the interface contact state between the substrate layer and the microporous layer can be more accurately and objectively evaluated and judged.

[0069] Corresponding to the above method embodiment, the application also provides a gas diffusion layer interface contact state evaluation device, comprising:

[0070] A first measurement unit is configured to measure the substrate layer resistance, the microporous layer resistance and the interface resistance in the gas diffusion layer sample to be evaluated. The interface resistance is the interface resistance between the substrate layer and the microporous layer.

[0071] A second measurement unit is configured to measure the contact area between the carbon particles in the microporous layer and the carbon fibers in the substrate layer in the gas diffusion layer sample to be evaluated.

[0072] An operation unit is configured to calculate the equivalent contact resistance between the carbon particles in the microporous layer and the carbon fibers in the substrate layer based on the contact area and the interface resistance.

[0073] An output unit is configured to determine the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

[0074] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the described unit can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0075] A gas diffusion layer interface contact state evaluation method can be applied to the research, production and testing of gas diffusion layers.

[0076] For the research and development of the gas diffusion layer, the interface real contact state between the substrate layer and the microporous layer of the gas diffusion layer can be evaluated by the gas diffusion layer interface contact state evaluation method described in the above embodiments, so as to evaluate the performance of the gas diffusion layer, and to provide support for the improvement of the research and development scheme of the gas diffusion layer. Similarly, during the production process of the gas diffusion layer, the interface real contact state between the substrate layer and the microporous layer of the gas diffusion layer can be evaluated by the gas diffusion layer interface contact state evaluation method described in the above embodiments, so as to evaluate the performance of the gas diffusion layer, and to judge whether the gas diffusion layer manufactured in the production process is qualified. In the research and development and production activities, test, comparison experiment and other means are often used, such as evaluating the service life and durability of the product through the accelerated decay experiment, and then the equivalent contact resistance of the carbon particles in the microporous layer and the carbon fibers in the substrate layer can be calculated before and after the accelerated decay experiment (the samples 1-3 in step S1 are subjected to the accelerated decay experiment), so as to evaluate the change of the interface contact state before and after the experiment.

[0077] The preferred embodiments of the present application are described in detail above. It should be understood that those skilled in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A method for evaluating an interface contact state of a gas diffusion layer, characterized by, The method comprises the following steps: calculating the substrate layer resistance, the microporous layer resistance and the interface resistance between the substrate layer and the microporous layer in the gas diffusion layer sample to be evaluated; calculating the contact area between the carbon particles in the microporous layer and the carbon fibers in the substrate layer in the gas diffusion layer sample to be evaluated; calculating the equivalent contact resistance between the carbon particles in the microporous layer and the carbon fibers in the substrate layer based on the contact area and the interface resistance; determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

2. The method for evaluating the interface contact state of a gas diffusion layer according to claim 1, wherein The calculation of the substrate layer resistance in the gas diffusion layer specifically comprises: for the gas diffusion layer sample to be evaluated, determining the thickness t0 of the substrate layer and the thickness t1 of the microporous layer; A substrate layer sample having a thickness t0is prepared and the electrical resistance of this sample is measured as the substrate layer resistance R in the gas diffusion layer sample to be evaluated G .

3. The method for evaluating the interface contact state of a gas diffusion layer according to claim 2, characterized by The calculation of the microporous layer resistance in the gas diffusion layer specifically comprises: measuring the resistance R1 of the gas diffusion layer sample to be evaluated; preparing a gas diffusion layer sample with a substrate layer thickness t0 and a microporous layer thickness t2, and measuring the resistance R2 of the sample; calculating the microporous layer resistance in the gas diffusion layer sample to be evaluated by the following formula: wherein R M represents the microporous layer resistance in the gas diffusion layer sample to be evaluated.

4. The method for evaluating the interface contact state of a gas diffusion layer according to claim 3, characterized by The calculation of the interface resistance in the gas diffusion layer specifically comprises: calculating the interface resistance in the gas diffusion layer sample to be evaluated by the following formula: R G-M = R1- R G - R M wherein R G-M represents the interfacial resistance in the gas diffusion layer sample to be evaluated.

5. The method for evaluating the interface contact state of a gas diffusion layer according to claim 1, wherein The contact area between the carbon particles in the microporous layer and the carbon fibers in the substrate layer in the gas diffusion layer sample to be evaluated is calculated by the micro-CT method.

6. The method for evaluating the interface contact state of a gas diffusion layer according to claim 1, wherein The calculation of the equivalent contact resistance between the carbon particles in the microporous layer and the carbon fibers in the substrate layer based on the contact area and the interface resistance specifically comprises: where S f-c represents the contact area, R G-M represents the interface resistance, represents the equivalent contact resistance.

7. A gas diffusion layer interface contact state evaluation device characterized by comprising: comprises: a first measurement unit for calculating the substrate layer resistance, the microporous layer resistance and the interface resistance between the substrate layer and the microporous layer in the gas diffusion layer sample to be evaluated; a second measurement unit for calculating the contact area between the carbon particles in the microporous layer and the carbon fibers in the substrate layer in the gas diffusion layer sample to be evaluated; an operation unit for calculating the equivalent contact resistance between the carbon particles in the microporous layer and the carbon fibers in the substrate layer based on the contact area and the interface resistance; an output unit for determining the interface contact state of the gas diffusion layer sample to be evaluated based on the size of the equivalent contact resistance.

8. The application of the gas diffusion layer interface contact state evaluation method according to any one of claims 1-6 in the research, production and testing of gas diffusion layers.

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