WO2024037530A1

WO2024037530A1 - Fuel cell

Info

Publication number: WO2024037530A1
Application number: PCT/CN2023/113076
Authority: WO
Inventors: 阿提比斯.罗伯特·亨利; 罗伯茨.乔伊·安妮
Original assignee: 上海韵量新能源科技有限公司
Priority date: 2022-08-15
Filing date: 2023-08-15
Publication date: 2024-02-22
Also published as: CN115275253A

Abstract

A fuel cell, comprising a pair of flow field plates, each flow field plate comprising a plurality of reactant flow channels separated by platforms, wherein at least one platform in at least one flow field plate has a curved top cross-section. In particular, a cathode plate may be provided with a platform having a partially or continuously curved cross-section. In some embodiments, the cross-section of the top of the platform is a circular arc. The fuel cell further comprises a membrane electrode assembly having a cathode gas diffusion layer (GDL), wherein the cathode GDL has a compressible surface. When the fuel cell is assembled, the compressible surface is compressed when same comes into contact with the platform of the cathode plate, such that a compressed region on a surface of the cathode GDL is closely attached to the curved top of the platform.

Description

The fuel cell

Technical field

The present invention relates to a fuel cell, and in particular to a flow field plate for a hydrogen fuel cell.

Background technique

Fuel cells electrochemically convert hydrogen fuel and an oxidant (such as oxygen in the air) into electrical energy and reaction products. A type of fuel cell called a polymer electrolyte membrane ("PEM") fuel cell typically employs a membrane electrode assembly ("MEA") containing a solid polymer ion exchange membrane with a catalyst layer applied over The two sides of the ion exchange membrane form a catalyst coating membrane ("CCM"), which is disposed between two gas diffusion layers ("GDL"). The catalyst layer contains a catalyst, such as finely divided platinum, to initiate the desired electrochemical reaction. GDL effectively acts as a facilitator to aid the diffusion of reactants on the CCM, and typically contains a porous conductive sheet such as carbon fiber paper or carbon cloth. In operation, the electrodes are electrically coupled to provide an electrical circuit for conducting electrons between the electrodes through an external circuit.

In a typical fuel cell, the MEA is positioned between two conductive fluid flow field plates or separators. The fluid flow field plate has at least one fluid flow channel formed in at least one of its major planar surfaces. The fluid flow field plate acts as a current collector, provides support for the electrodes, provides access for fuel and oxidant to the respective anode and cathode surfaces, and provides channels for the removal of reaction products, such as water, that are produced during fuel cell operation. formed in. One fluid plate, called the anode plate, has open fuel flow channels that direct hydrogen fuel to the anode side of the MEA, while the other fluid plate, called the cathode plate, has open channels that direct oxidizers (such as air) to the cathode side of the MEA. Oxidant flow channel.

Both anode and cathode plates typically have multiple parallel flow channels separated by elongated platforms. These flow channels typically include a flat top surface in contact with an adjacent GDL surface. The portion of the flow field plate containing the flow channels and platforms is often referred to as The flow field region and the part of the CCM adjacent to the GDL that is fluidly connected to the flow field region are usually called the active region of the CCM, that is, the part of the CCM where electrochemical reactions occur. Optimal fuel cell performance depends on the reactants reaching the active area of the CCM where electrochemical reactions occur. Taking the cathode as an example, the oxidant supply must migrate from the oxidant channel of the cathode plate through the adjacent GDL to the active area of the CCM. However, conventional platform designs tend to impede the flow of reactants from the flow channels to those portions of the CCM adjacent to the platform, thereby reducing fuel cell performance. Fuel cell performance is particularly sensitive to oxygen concentration in the cathode catalyst region, especially when air is used as oxidant because the oxygen concentration in the air is only about 21%.

It is therefore an object of the present invention to provide an improved fuel cell flow field plate which solves some of the shortcomings of prior art flow field plate designs.

Contents of the invention

According to one aspect, a fuel cell includes an anode plate, a cathode plate, and a membrane electrode assembly sandwiched between the anode plate and the cathode plate. The anode plate includes a separator having an active side with a fuel flow field having at least one platform open face fuel flow channel. The cathode plate includes a separator having an active side with an oxidant flow field having open oxidant flow channels and at least one platform. A membrane electrode assembly consists of a catalyst-coated ion exchange membrane sandwiched by anode and cathode gas diffusion layers. At least one platform of the anode and cathode plates has a top with a curved cross-section. In some aspects, both the anode and cathode plates have a platform with a top that is curved in cross-section.

At least one of the anode and cathode gas diffusion layers is compressible and compresses around at least a portion of the platform having a curved cross-section on top.

The oxidant flow field may include a plurality of parallel platforms that are straight along the length and have tops with curved cross-sections. The curved cross-section may be continuously curved and may, for example, have a fixed radius (full circle) to define a circular portion, or may have a variable radius to define a portion with varying curvature.

Description of drawings

Figure 1 is a perspective view of the active side of a cathode plate of a PEM fuel cell according to one embodiment of the present invention.

FIG. 2 is a perspective view of the inactive side of the cathode plate shown in FIG. 1 .

FIG. 3 is a top view of the end portion of the cathode plate shown in FIG. 1 .

Figure 4 is a cross-sectional view along section line B-B showing a portion of the flow field of the cathode plate.

Figure 5 is a detailed view of area C of one channel and two adjacent platforms of the cathode plate flow field.

6 is a cross-sectional view of a portion of a fuel cell including a cathode plate according to an embodiment of the present invention and a portion of two adjacent fuel cells.

Figure 7 is a detailed view of the image of area D showing a portion of the MFA in contact with the platform of the cathode plate.

Figure 8 is a comparison chart of fuel cell stack polarization curves between the product of the present invention and the product in the prior art.

Detailed ways

Embodiments disclosed herein generally relate to a fuel cell including a pair of flow field plates, each flow field plate having a fluid flow field including a plurality of reactant flow channels separated by a platform, wherein the flow field plate At least one of the at least one platforms has a top with a continuously curved cross-section. In some embodiments, the cathode flow field includes a plurality of parallel linear flow channels whose corresponding platforms have continuously curved cross-sections. The cross-section of the platform top may have a fixed radius, thereby defining a circular portion, or a variable radius, thereby defining a portion with varying curvature. The fuel cell further includes an MEA having a cathode GDL having a compressible surface that compresses upon contact with the cathode plate platform when the fuel cell is assembled such that the compressed area of the cathode GDL surface conforms to the curved top of the platform.

Referring to Figures 1-7, according to one embodiment, fuel cell 10 includes MEA 12 sandwiched between cathode plate 14 and anode plate 16 (see Figure 6). Multiple fuel cells 10 may be stacked together to form a fuel cell stack (anode plate 16A of one adjacent fuel cell and cathode plate 14A of another adjacent fuel cell are shown in Figure 6).

The cathode plate 14 has a generally planar separator with an oxidant flow field 18 on one surface called the "active side" (see Figure 1). The opposite surface is referred to as the "inactive side" (see Figure 2) and faces the coolant channel 20 on the coolant side of the adjacent fuel cell anode plate 16A. The oxidant flow field 18 includes a plurality of open-face oxidant channels 22 separated by platforms 24 (see Figure 4). In this embodiment, the oxidant flow field 18 includes a plurality of lengthwise parallel and straight oxidant channels and corresponding platforms; however, other embodiments may feature flow fields with different channel geometries, such as serpentines.

At one end of cathode plate 14, fluid inlets 26, 28, and 30 introduce fuel (hydrogen), oxidant (air), and coolant flow, respectively, into fuel cell 10. At the other end of the cathode plate 14, fluid outlets 32, 34, 36 respectively discharge fuel, oxidant and coolant flows from the fuel cell 10. Fluid outlet ports 32, 34, 36 are fluidly coupled to corresponding fluid inlet ports 26, 28, 30 through flow channels within fuel cell 10. In particular, fuel flows from fuel inlet 26 via spaced fuel return channels 40 on the inactive side of cathode plate 14 into anode flow field channels 38 in adjacent anode plate 16A. Return channel 40 extends from fuel inlet 26 to a fuel return channel (not shown) in anode plate 16A; the fuel return channel extends through the thickness of anode plate 16A and is fluidly coupled to anode flow field channel 38 . The oxidant flows from the oxidant inlet 28 to the oxidant flow field channel 22 via spaced oxidant return channels 42 on the inactive side of the cathode plate 14 . Return channel 42 extends from oxidant inlet 28 to return channel 44 in cathode plate 14 ; oxidant return channel 44 extends through the thickness of cathode plate 14 and connects to oxidant flow field channel 22 through transition area 45 . Coolant flows from the coolant inlet 30 via the coolant backfield channel 46 on the inactive side of the cathode plate 14 to the coolant channel 20 of the adjacent anode plate 16A. Likewise, fuel, oxidant and coolant outlets 32, 34, 36 are fluidly coupled to their respective anode flow field channels 38, oxidant flow field channels 22 and coolant channels 20 through return channels. Perimeter seals (not shown) surround the ports and feedback channels to prevent leakage.

Referring specifically to Figures 4-5, the oxidant flow field 18 is characterized by a platform 24 having a curved cross-section platform top 52. Without being bound by theory, in theory the ideal cathode flow field should have as narrow a flow field platform as possible to maximize the amount of oxygen diffusion below the platform while providing sufficient electrical connections to ensure adequate current distribution and low resistive losses. It is desirable to provide a platform with a top with a curved cross-section and to minimize the width of the platform 24 and conversely maximize the width of the oxidant channel 22 . In this embodiment, the platform top 52 is completely circular, that is, continuously curved with a fixed radius R, thereby defining a circular portion. A suitable range for the platform radius is between 0.05 and 0.5 mm. Utilizing a full-circle design minimizes platform width and is also expected to simplify manufacturability because channels and platforms can be specified in full-circle dimensions. Alternatively, other embodiments (not shown) may be provided in which the top of the platform has other continuously curved geometries, such as an oval or elliptical shape. In yet other embodiments, platform top 52 may have a continuously curved cross-section of variable radius to define a portion with varying curvature.

In this embodiment, the radius of the platform is selected from 0.05 to 0.5 mm, and the spacing of the entire formed channels is relatively narrow. In the prior art, some designs use a radius of 2 mm, which results in a large space. In this embodiment, the narrower channels are formed. Channels and spacing can ensure precise control of the flow of gas. At the same time, the electrochemical reaction in a small space is more complete, and ultimately a high electrical density area is formed, and the obtained voltage is getting better and better.

Referring to Figure 8, the curve a represents the fuel cell stack polarization curve of the prior art product, while the curve b and the curve c respectively represent the fuel cells of the two fully circular design products using the solution of the present invention. As for the stack polarization curve, it can be seen from the comparison of the three curves that compared with the curve a in the prior art that does not adopt a full-circle design, the curves b and c corresponding to the product obtained by using the solution of the present invention are equally effective. Under current density, the higher the average output voltage, the better the power generation capacity of the stack. In this embodiment, by adjusting the design of the cathode plate and the anode plate, the higher the current At higher density, the power generation efficiency of the stack increases more significantly.

The platforms 24 also each have a platform bottom 54 that extends downwardly to the oxidant channel bottom 56 of the adjacent oxidant channel 22 . In this embodiment, platform bottom 54 provides sloped walls for adjacent oxidant channels 22 . The inclination angle of the inclined wall is defined as the ratio of the top radius R to the platform bottom width W, which can be between 0.1 and 0.5.

The flow channel walls are connected to the oxidant channel bottom 56 by fillets 58 for ease of fabrication; however, in other embodiments, the oxidant channel 22 may have other cross-sectional geometries, for example, the oxidant channel 22 may have a defined circular segment (not shown). out) circular cross section.

The cathode plate 14 may be constructed of expanded graphite and manufactured by stamping a blank plate to form the desired structure, followed by appropriate post-processing. Alternatively, cathode plate 14 may be constructed from other suitable materials known in the art and manufactured by other suitable techniques known in the art (e.g., molded graphite particle/resin composite, processed to form, for example, molded graphite particle/resin composite of formed conductive material, stamped into metal plates).

As mentioned previously, the platform should be designed to provide sufficient conductive connections to ensure adequate current distribution and low resistive losses. Platforms with a continuously curved top may reduce the available surface area for electrical contact with the MEA. To ensure adequate electrical contact, the MEA12 is equipped with a compressible GDL. Referring to Figure 7, the portion of the GDL (not shown) in contact with the platform 24 is compressed to conform to the curved platform top 52 and maintain good electrical contact. An example of a suitably compressible MEA includes a catalyst-coated perfluorosulfonic acid (PFSA) membrane sandwiched between a pair of carbon fiber paper GDLs.

According to yet another embodiment, the anode plate 16 includes a fuel flow field with a platform having a top with a curved cross-section. The cross-section of the platform top may be partially or continuously curved, and may, for example, be completely circular to define a circular portion.

In this embodiment, several flow channels are designed on the surface of the cathode plate, such as several open surface oxidant channels 22 in Figure 4. At this time, several open surface oxidant channels 22 are parallel to each other, and several are parallel to each other. In the flow channel design or the open surface oxidant channel 22, the side portion of the channel is a curved structure. At this time, the bending direction and bending size selected for each channel are completely consistent. Compared with the two designs with different bending structures, this embodiment The manufacturing cost is lower and the processing is more convenient. If there are differences in the bending of the anode plate and the cathode plate, the cost will be high. In this case, two sets of bending molds and manufacturing processes need to be designed.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Accordingly, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that, when used in this specification, the terms "comprising" and "includes" specify the presence of one or more of the stated features, integers, steps, operations, elements and components but do not exclude the presence or presence of one or more of the stated features, integers, steps, operations, elements and components. Addition of other characteristics, integers, steps, operations, elements, components and groups. Directional terms such as "top," "bottom," "upward," "downward," "vertical" and "lateral" are used in the following descriptions for the purpose of providing relative reference only and are not intended to imply any limitation on any item How it is positioned during use, or how it is installed in a component or in relation to the environment. Furthermore, unless otherwise stated, the term "coupled" and variations thereof as used in this specification are intended to include both indirect and direct connections. For example, if a first device is coupled to a second device, that coupling may be through a direct connection or through an indirect connection via other devices and connections. Similarly, if a first device is communicatively coupled to a second device, communications may be through a direct connection or through an indirect connection via other devices and connections.

As used herein, references to "about" or "approximately" a number or "substantially" equal to a number means within plus or minus 10% of that number.

It is contemplated that any part of any aspect or embodiment discussed in this specification may be implemented or combined with any part of any other aspect or embodiment discussed in this specification.

The scope of the claims should not be limited by the preferred embodiments set forth in the Examples, but should be given the broadest interpretation consistent with the entire description.

Claims

Fuel cells include:

An anode plate including a separator having an active side with a fuel flow field including an open-face fuel flow channel having at least one platform;

a cathode plate including a separator having an active side with an oxidant flow field including an open oxidant flow channel and at least one platform; and

a membrane electrode assembly sandwiched between an anode plate and a cathode plate, said membrane electrode assembly comprising a catalyst-coated ion exchange membrane sandwiched by anode and cathode gas diffusion layers;

It is characterized in that at least one of the platforms of the anode plate and the cathode plate has a top with a curved cross section.
2. The fuel cell of claim 1, wherein at least one of the anode gas diffusion layer and the cathode gas diffusion layer is compressible and compresses around at least a portion of the platform having a curved cross-section top.
The fuel cell according to claim 2, wherein the oxidant flow field includes a plurality of straight platforms parallel to the length direction, and the platforms have tops with curved cross-sections.
The fuel cell of claim 1, wherein the top of the at least one platform has a continuously curved cross-section.
The fuel cell according to claim 4, wherein the continuously curved cross section is a circular arc segment with a given radius.
The fuel cell of claim 5, wherein the radius is between 0.05 and 0.5 mm.
The fuel cell according to claim 4, wherein the continuously curved cross section is composed of multiple curve segments, and the curvature of each curve segment corresponds to a different radius.
The fuel cell according to claim 7, wherein the top cross-section of the at least one platform is an elliptical or elliptical-like curve segment.
The fuel cell of claim 1, wherein both the cathode plate platform and the anode plate platform have tops with curved cross-sections.