KR20230056881A - A separator for a fuel cell for improving sealing performance and a fuel cell stack comprising the same - Google Patents

Abstract

The present invention relates to a separation plate which can improve the sealing performance of a fuel cell stack. The separation plate comprises: a plate-shaped body unit; a manifold unit including an inflow manifold formed through a corner of the body unit to allow fluid to flow in, and a discharge manifold which is formed through another corner of the body unit in a direction opposite to the inflow manifold and discharges fluid; a channel unit formed between the inflow manifold and the discharge manifold and recessed from one side of the body unit to guide fluid flowing in through the inflow manifold to move toward the discharge manifold, wherein the channel unit is recessed and formed at a certain distance away from the manifold unit to form a flat unit between the channel unit and the manifold unit, and the manifold unit and the channel unit are connected to the inside of the flat unit by a communication unit.

Description

Separator for fuel cell to improve sealing and fuel cell stack including the same

The present invention relates to a separator capable of improving sealing properties of a fuel cell stack.

A solid oxide fuel cell (SOFC) is a device that directly converts chemical energy contained in fuel into electrical energy within a cell. Recently, it is a pollution-free power generation device that has been studied with interest as a power source for automobiles.

A solid oxide fuel cell includes a stack in which unit cells that generate electricity and peripheral parts thereof are stacked. Hydrogen as a fuel is supplied to the anode of the stack and oxygen as an oxidizing agent is supplied to the cathode to generate electricity.

In the solid oxide fuel cell, a sealing material is provided around the unit cell to prevent hydrogen and oxygen (air) from mixing or leaking. Mixing hydrogen and oxygen can have a fatal effect on the efficiency of a fuel cell.

In general, the sealant is made of a glass-based material. Since the solid oxide fuel cell operates at a temperature of 700 ° C. or higher, it must be airtightly bonded with the adhesive material even at high temperatures, and must have excellent thermal expansion coefficient and heat resistance. Therefore, a glass-based material is more suitable as a sealing material than a ceramic material.

However, in the prior art, local pressure was applied to the sealant by the separator of the solid oxide fuel cell, so that the sealant was severely pressed or destroyed, so that its function could not be performed.

1A is a photograph of one side of a separator disposed on the anode side of a unit cell included in a conventional solid oxide fuel cell, and FIG. 1B is a photograph of a sealing material placed on the separator disposed on the cathode side of the unit cell. am. A fuel cell stack is formed by stacking the separators according to FIGS. 1A and 1B, interposing unit cells therebetween and disposing the sealant around the unit cells.

The separator of FIG. 1A includes a pair of manifolds 91 and 92 and a channel 93 connecting them. Referring to FIG. 1B , it can be seen that the sealing material 94 is severely pressed by the channel 93 included in the separation plate of FIG. 1A. As a result, the sealing material 94 may block the channel 93 or lose sealing properties against hydrogen and oxygen. It may also cause partial overheating and severe oxidation.

An object of the present invention is to provide a separator having a new shape that can not apply local pressure to a sealing material interposed between a pair of separator plates.

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof set forth in the claims.

A separator for a fuel cell according to an embodiment of the present invention includes a plate-shaped body; Including an inlet manifold formed through one corner of the body portion to introduce fluid, and a discharge manifold formed through through the other corner portion of the body portion in a direction opposite to the inlet manifold to discharge fluid manifold unit; A channel portion formed by being recessed from one surface of the body between the inlet manifold and the outlet manifold and guiding the fluid flowing through the inlet manifold to move toward the outlet manifold; and It is characterized in that the flat part is formed between the channel part and the manifold part by being recessed at a position apart from the fold part, and the manifold part and the channel part are connected to the inside of the flat part part by a communication part.

The manifold part may be formed to have a predetermined length and width along an edge of the body part.

The channel unit may include a plurality of passages having a predetermined length and width and disposed at predetermined intervals.

The communication part may have one end connected to an end of the channel part and an obliquely extending form from the end of the channel part and the other end connected to the manifold part.

The manifold unit may include a fuel inlet manifold and a fuel discharge manifold formed at a pair of opposite corner portions of the body portion; and an oxygen inlet manifold and an oxygen discharge manifold formed at another pair of opposite corner portions of the body portion, wherein the channel portion is recessed from one surface of the body portion to form the fuel inlet manifold and the fuel discharge manifold. a fuel channel unit for flowing fuel between them; and an oxygen channel portion formed indented from the other surface of the body portion to allow oxygen to flow between the oxygen inlet manifold and the oxygen discharge manifold. A flat part may be formed.

A fuel cell stack according to an embodiment of the present invention includes a unit cell including a plurality of the separation plates and disposed on the channel portion between a pair of adjacent separation plates; and a sealant positioned at the periphery of the unit cell and interposed between the pair of separator plates, wherein the sealant is pressed by the flat portion of the pair of separator plates.

The sealing material may include a through hole formed at a position corresponding to the manifold portion of the separation plate.

According to the present invention, since the sealant can maintain its shape, a solid oxide fuel cell that does not lose sealability even when the number of stacks is increased or the area is enlarged can be obtained.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1a is one side of a conventional separator.
Figure 1b is the other surface of a conventional separator.
2 is an exploded perspective view of a fuel cell stack according to the present invention.
3 is a cross-sectional view of a unit cell according to the present invention.
Figure 4a is a perspective view showing the upper surface of the separator according to the present invention.
Figure 4b is a perspective view showing the lower surface of the separator according to the present invention.
FIG. 5A is a cross-sectional view along the line A-A' of FIG. 4A.
5B is a cross-sectional view taken along line BB′ of FIG. 4B.
6a is an upper surface of a separator prepared in an embodiment according to the present invention.
6B is a bottom view of a separator prepared in an embodiment according to the present invention.
7A to 7E are reference views for explaining a process of preparing a fuel cell stack in an embodiment according to the present invention.
8 illustrates a temperature raising and reduction protocol of a fuel cell stack used in Experimental Example 1 according to the present invention.
9 is a result of measuring an open circuit voltage of a fuel cell stack in Experimental Example 1 according to the present invention.
10 is a result of measuring the cell voltage of each layer (1F, 2F, 3F) and the stack voltage of the fuel cell stack in the fuel cell stack driving situation (constant current output) in Experimental Example 2 according to the present invention.
11 is a result of measuring an open circuit voltage of a fuel cell stack in Experimental Example 2 according to the present invention.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

Like reference numerals have been used for like elements throughout the description of each figure. In the accompanying drawings, the dimensions of the structures are shown enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where another part is present in the middle. Conversely, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is in the middle.

Unless otherwise specified, all numbers, values and/or expressions expressing quantities of components, reaction conditions, polymer compositions and formulations used herein refer to the number of factors that such numbers arise, among other things, to obtain such values. Since these are approximations that reflect the various uncertainties of the measurement, they should be understood to be qualified by the term "about" in all cases. Also, when numerical ranges are disclosed herein, such ranges are contiguous and include all values from the minimum value of such range to the maximum value inclusive, unless otherwise indicated. Furthermore, where such ranges refer to integers, all integers from the minimum value to the maximum value inclusive are included unless otherwise indicated.

2 is an exploded perspective view showing a portion of a fuel cell stack according to the present invention. Referring to this, the fuel cell stack is located in a plurality of separator plates 100 and 100', a unit cell 200 interposed between a pair of adjacent separator plates 100 and 100', and a peripheral portion of the unit cell. A sealing material 300 interposed between the pair of separation plates 100 and 100' is included.

3 is a cross-sectional view of the unit cell 200. For reference, FIG. 3 defines upper and lower sides based on the stacking direction of the fuel cell stack of FIG. 2 . Referring to FIG. 3 , the unit cell 200 includes an air electrode 210 , an electrolyte 220 and an anode 230 .

When an oxidizing agent such as air or oxygen is supplied to the cathode 210, a reaction shown in Chemical Formula 1 below occurs and oxygen ions are generated.

[Formula 1]

1/2O ₂ + 2e ^- → O ^2-

The oxygen ions move to the fuel electrode 230 through the electrolyte 220 .

When fuel such as hydrogen or hydrocarbon is supplied to the anode 230, the oxygen ions react with the fuel to generate water and emit electrons as shown in Chemical Formula 2 below.

[Formula 2]

O ^2- + H ₂ → H ₂ O + 2e ^-

Oxygen ions formed from the oxidizing agent in the air electrode 210 move toward the fuel electrode 230 according to the concentration gradient of oxygen ions, and electrons move toward the fuel electrode 230 along an external circuit electrically connecting the air electrode 210 and the fuel electrode 230. flows to the air electrode 210.

Here, the electrolyte 220 blocks permeation of an oxidizing agent and fuel, and has no electronic conductivity, but can transmit oxygen ions.

In this way, if oxygen ions move from the air electrode 210 to the fuel electrode 230 and maintain an overall charge balance, useful power can be produced through a fuel oxidation reaction. At this time, only pure water and heat are emitted as reaction by-products, which can also be usefully utilized.

Figure 4a is a perspective view showing the upper surface of the separation plate 100. 4B shows a lower surface of the separator 100. In FIGS. 4A and 4B , the upper and lower surfaces are defined based on the stacking direction of the fuel cell stack of FIG. 2 .

4A and 4B, the separator 100 includes a plate-shaped body 110, a fuel inlet manifold 121a formed at a pair of opposite corners of the body 110, and A fuel discharge manifold (121b), an oxygen inlet manifold (122a) and an oxygen discharge manifold (122b) formed at the opposite pair of corners of the body portion (11), both sides of the body portion (110) may include channel portions 131 and 132 for guiding the movement of fuel or oxygen between the inlet manifolds 121a and 122a and the outlet manifolds 121b and 122b.

The body part 110 is a plate-like structure providing a space in which the inlet manifolds 121a and 122a of the separator 100 can be formed, and the material thereof is not particularly limited, such as stainless steel, titanium, etc. metals such as alloys, aluminum alloys, and nickel alloys; Alternatively, it may be made of carbon-based materials such as graphite and carbon composites.

Referring to FIG. 4A, the fuel inlet manifold 121a is formed through one corner of the body 110 to have a certain length and width, and fuel flows through the fuel inlet manifold 121a. is introduced

The fuel discharge manifold 121b is formed through the fuel intake manifold 121a to have a predetermined length and width at the other corner, and fuel is discharged through the fuel discharge manifold 121b. .

The channel part is recessed from the upper surface of the body part 110 between the fuel inlet manifold 121a and the fuel discharge manifold 121b, and the fuel introduced through the fuel inlet manifold 121a discharges the fuel. It includes a fuel channel part 131 that guides the manifold 121b to move toward.

The fuel channel unit 131 may include a plurality of passages 131a having a predetermined length and width and disposed at predetermined intervals. The passage 131a may be formed long in a direction crossing the longitudinal directions of the fuel inlet manifold 121a and the fuel discharge manifold 121b to guide the fuel.

The present invention is characterized in that the fuel channel unit 131 is recessed at a position separated from the fuel inlet manifold 121a and the fuel discharge manifold 121b by a predetermined distance. 1A is a photograph of one side of a conventional separator. Referring to this, it can be seen that both ends of the channel 93 are in direct communication with the pair of manifolds 91 and 92. Accordingly, when a plurality of the separation plates are stacked, local pressure is applied to the sealing material 94 as shown in FIG. 1B, so that the sealing material 94 is pressed according to the shape of the channel 93.

FIG. 5A is a cross-sectional view along the line A-A' of FIG. 4A. Referring to this, the present invention is formed by indenting the fuel channel part 131 at a position separated from the fuel inlet manifold 121a and the fuel discharge manifold 121b by a predetermined distance, based on the upper surface of the body part 110 Thus, the flat portion 140 was provided therebetween. To this end, the fuel inlet manifold 121a, the flow path 131a of the fuel channel part 131, and the fuel discharge manifold 121b are connected to each other through the fuel communication part 150a to the inside of the flat part 140. can form

Specifically, the fuel communication part 150a has one end connected to the end of the flow path 131a of the fuel channel part 131, and is formed obliquely extending from the end of the flow path 131a so that the other end is connected to the fuel inlet. It may be connected to the manifold 121a or the fuel discharge manifold 121b.

When a fuel cell stack is formed by stacking a plurality of separator plates 100 having flat portions 140 as shown in FIG. 2 , the sealing material 300 interposed between the pair of separator plates 100 is a fuel channel part 131), but by the flat portion 140, unlike the prior art, no local pressure is applied.

Referring to FIG. 4B, the oxygen inlet manifold 122a is formed through one corner of the body 110 to have a certain length and width, and oxygen flows through the oxygen inlet manifold 122a. is introduced

The oxygen discharge manifold 122b is formed through the other corner portion opposite to the oxygen inlet manifold 122a to have a certain length and width, and oxygen is discharged through the oxygen discharge manifold 122b. .

The channel part is indented from the lower surface of the body part 110 between the oxygen inlet manifold 122a and the oxygen outlet manifold 122b, and oxygen introduced through the oxygen inlet manifold 122a It includes an oxygen channel portion 132 that guides it to move toward the discharge manifold 122b.

The oxygen channel unit 132 may include a plurality of passages 132a having a predetermined length and width and disposed at predetermined intervals. The passage 132a is formed long in a direction crossing the longitudinal directions of the oxygen inlet manifold 122a and the oxygen outlet manifold 122b to guide the oxygen.

FIG. 5B is a cross-sectional view taken along line BB′ of FIG. 4B. Referring to this, in the present invention, the oxygen channel unit 132 is recessed at a position separated from the oxygen inlet manifold 122a and the oxygen discharge manifold 122b by a predetermined distance, and the lower surface of the body unit 110 is referenced. Thus, the flat portion 140 was provided therebetween. To this end, an oxygen communication part 150b is provided to connect the oxygen inlet manifold 122a, the flow path 132a of the oxygen channel part 132, and the oxygen discharge manifold 122b to the inside of the flat part 140. can form

Specifically, the oxygen communication part 150b has one end connected to the end of the flow path 132a of the oxygen channel part 132, and is formed obliquely extending from the end of the flow path 132a so that the other end is connected to the oxygen inlet. It may be connected to the manifold 122a or the oxygen exhaust manifold 122b.

When a fuel cell stack is formed by stacking a plurality of separator plates 100 having the flat portion 140 as shown in FIG. 2, the sealing material 300 interposed between the pair of separator plates 100 is an oxygen channel part 132), but by the flat portion 140, unlike the prior art, no local pressure is applied.

The sealant 300 is a component for preventing mixing and leakage of fuel and oxygen in the fuel cell stack, and is interposed between the pair of separator plates 100 to be located in the periphery of the unit cell 200 .

The material of the sealant 300 is not particularly limited, but it may be preferable to use a glass-based material.

The sealant 300 may have an area equal to or smaller than that of the separator 100 . At this time, through holes (not shown) may be formed in the sealant 300 at positions corresponding to the manifolds 121a, 121b, 122a, and 122b of the separation plate. In addition, a space in which the unit cell 200 can be located may exist in the center of the sealant 300 .

Hereinafter, the present invention will be described in more detail through specific examples. However, these Examples and Experimental Examples are for exemplifying the present invention, and the scope of the present invention is not limited thereto.

Example

A separator having an upper surface as shown in FIG. 6A and a lower surface as shown in FIG. 6B was prepared. It can be seen that the flat part is formed between the channel part and the manifold part.

After placing nickel foam (Ni-foam) on one of the separators as shown in FIG. 7A, unit cells were stacked as shown in FIG. 7B. Thereafter, as shown in FIG. 7c, a sealing material was laminated on the periphery of the unit cell, and a gold mesh (Au mesh) was placed on the unit cell as shown in FIG. 7d. The stack element of the first layer was completed by stacking another separator plate. By repeating this a total of three times, a fuel cell stack with a total of three layers as shown in FIG. 7E was manufactured.

Experimental Example 1 - Verification of temperature rise and reduction protocol

The fuel cell stack according to the embodiment was operated under the operating conditions as shown in FIG. 8, and cell performance was evaluated accordingly. Specifically, after nitrogen purging, reduction was performed while gradually increasing the hydrogen fraction.

9 is a result of measuring the voltage of the fuel cell stack. Referring to this, as the hydrogen fraction increases, the OCV of the stack tends to rise stably, and it is confirmed that the sealing structure of the stack works effectively and the reduction of the cell proceeds well. As a result, under pure hydrogen fuel conditions Since the ideal open-circuit voltage that can be implemented in a stack composed of three-layer unit cells was 3.3 V or higher, it can be seen that the stack can operate reliably due to the improved sealing structure.

Experimental Example 2 - Verification of stack constant current stability (Galbanostatic)

The constant current stability of the fuel cell stack according to the embodiment was evaluated in terms of how stably a user desired output (voltage) could be obtained in a stack driving situation. In various output situations, there are concerns about whether the gas sealing is stable due to the heat generated by the fuel cell or the change in the fuel utilization rate of the gas, but if the output is stable through long-term operation, a stable stack without gas sealing issues through the design of the present invention can be said to be driven.

10 is a result showing how stably output is responding to various output requests for a long time. In particular, since the unit cells located on the three layers in the stack show uniform performance without large deviations and stable output for a long time under various load conditions, the sealing material and sealing structure employed in the fuel cell stack have good durability without problems. can know that

11 is a result of checking the OCV value of the stack between the above experiments. Referring to this, it can be seen that the sealing material or sealing structure employed in the fuel cell stack is very stable because the result shows a stable value even after long-term operation under various power requirements.

As above, the experimental examples and examples of the present invention have been described in detail, the scope of the present invention is not limited to the above-described experimental examples and examples, and the basic concept of the present invention defined in the following claims Various modifications and improvements made by those skilled in the art are also included in the scope of the present invention.

100: separator 200: unit cell 300: sealing material
110: body part 121a: fuel inlet manifold 121b: fuel discharge manifold
122a: Oxygen inlet manifold 122b: Oxygen outlet manifold
131: fuel channel unit 132: oxygen channel unit 131a, 132a: flow path
140: flat part 150a: fuel communication part 150b: oxygen communication part

Claims (7)

a plate-shaped body;
Including an inlet manifold formed through one corner of the body portion to introduce fluid, and a discharge manifold formed through through the other corner portion of the body portion in a direction opposite to the inlet manifold to discharge fluid manifold unit;
A channel portion formed indented from one surface of the body between the inlet manifold and the outlet manifold and guiding the fluid flowing through the inlet manifold to move toward the outlet manifold; includes,
The channel part is recessed at a position separated from the manifold part by a predetermined distance, and a flat part is formed between the channel part and the manifold part,
The separator for a fuel cell, characterized in that the manifold part and the channel part are connected to the inside of the flat part part by a communication part. According to claim 1,
The manifold part is formed to have a predetermined length and width along the edge of the body part. According to claim 1,
The channel portion has a predetermined length and width and includes a plurality of flow passages disposed at predetermined intervals. According to claim 1,
The communication part has one end connected to the end of the channel part, and is formed obliquely extending from the end of the channel part, and the other end is connected to the manifold part. According to claim 1,
The manifold unit may include a fuel inlet manifold and a fuel discharge manifold formed at a pair of opposite corner portions of the body portion; And an oxygen inlet manifold and an oxygen outlet manifold formed at another pair of opposite corner portions of the body portion,
The channel unit is recessed from one surface of the body unit, and the fuel channel unit flows fuel between the fuel inlet manifold and the fuel discharge manifold; and an oxygen channel portion that is recessed from the other surface of the body portion and allows oxygen to flow between the oxygen inlet manifold and the oxygen outlet manifold.
Separation plate for a fuel cell, characterized in that a flat part is formed between the manifold part and the channel part on one surface and the other surface of the body part, respectively. Including a plurality of separators according to any one of claims 1 to 5,
a unit cell located on the channel part between a pair of adjacent separator plates; And a sealing material located in the periphery of the unit cell and interposed between the pair of separator plates;
The fuel cell stack, characterized in that the sealing material is pressed by the flat portion of the pair of separator plates. According to claim 6,
The fuel cell stack wherein the sealing material includes a through hole formed at a position corresponding to the manifold portion of the separation plate.

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