KR20190061806A - Stress balancing module and fuel cell comprising thereof - Google Patents

Abstract

A stress balancing module and a fuel cell comprising the same are provided. The stress balancing module is a stress balancing module provided between a fuel cell stack and an upper end plate which presses the fuel cell stack in a stacking direction of the fuel cell stack. The stress balancing module is a hollow metal container having a metal plate of a soft material in contact with the uppermost unit fuel cell of the fuel cell stack on one side, and a liquid metal can be filled in the metal container.

Description

[0001] STRESS BALANCING MODULE AND FUEL CELL COMPRISING THEREOF [0002]

The present application relates to a stress balancing module and a fuel cell including the same.

Generally, a solid oxide fuel cell (SOFC) is a power generation system that uses hydrogen as fuel and generates electricity and water by electrochemical reaction using oxygen in the air as an oxidizer. , It has little or no pollution and noises and has high efficiency in generating electricity.

Such a solid oxide fuel cell is divided into a repeating component (RC) and a non-repeating component. The repeating component (RC) is a unit fuel cell that is repeatedly laminated. The non- Such as a manifold header, which is responsible for the gas flow.

A unit fuel cell includes a fuel electrode (anode, cathode), an air electrode (anode, anode), a separator plate for forming a flow path of a fuel gas and an oxidizer gas, a current collecting plate for collecting charge, . When the fuel gas is supplied to the fuel electrode and the oxidant gas is supplied to the air electrode, an electrochemical reaction occurs at each electrode to obtain a DC power source.

Since the voltage of unit fuel cell maintains 0.7 V ~ 0.9 V at rated output, in actual power generation, this unit cell is stacked in several layers to increase the voltage and to increase the output by increasing the area of the cell. This stack of unit cells is called the 'SOFC stack'.

Research on solid oxide fuel cells (especially flat plate type SOFCs) has already been started in the 60s and has been studied for over 50 years. However, despite longstanding research, Bloom Energy is the only company that has commercialized SOFC in the US, and even without provincial subsidies there is a problem of poor product quality.

One of the biggest obstacles to the commercialization of solid oxide fuel cells is that the reliability of the SOFC stack is deteriorating. The reason why the reliability of the SOFC stack is poor is that the performance of the product is not repeatedly reproduced, and the performance of the whole stack is deteriorated by causing one or two RCs to fail. If a problem occurs in one or two RCs, the reduced performance will not be maintained and the stack failure will accelerate because localized heat builds up in the RC area, and when the cell is broken, irreversible damage due to this localized heat It tends to spread to the next cell without stopping.

In a stack consisting of multiple RCs, these failed RCs can occur randomly, while the cells with the highest frequency are called end cells (called the top-end unit fuel cells in the stacked RCs as 'end cells' )to be. In SOFC stacks, this repetitive end-cell failure problem is very serious and is widespread in organizations that manufacture flatbed-based stacks.

The cause of the end cell problem has not yet been clarified, and therefore, the problem solving method has not been studied clearly. Two of the most likely causes for suspected misuse are the irregularity between the RCs and the unstressed stresses in the end cells.

One of the most likely causes is the stress unevenness of the 2D cell plane of the end cell because it is very difficult to find the result that a small amount of flow only flows through the end cell in many flow analysis and computational simulation results to be. Therefore, many researchers are trying to find the cause of this SOFC end cell problem from the stress unevenness, because there is a reason why such stress unevenness can be directly related to the SOFC end cell performance.

In particular, the anode of the end cell is made of ceramic, and typical anode materials of commercially available SOFC include LaSrMnO ₃ and LaSrCoFeO ₃ . These ceramics have catalytic activity for anodic reaction (oxygen reduction reaction) at a certain level or more at the operating temperature, and most of them are MIECs (Mixed Ion Electronic Conductors) having a perovskite structure.

MIEC ceramics have high electronic conductivity, but they generally have 10 to 20 times lower electrical conductivity than metals. Nevertheless, the reason why such ceramic MIECs are used as SOFC anode materials is that the anodes are oxidizing atmospheres, which are very difficult to use because common metal materials are oxidized. The use of noble metals can constitute the anode without being oxidized at the operating temperature of the SOFC. In this case, the cost of the stack becomes very high.

A negative electrode having a conductivity comparable to that of a metal is not a serious problem even if a contact area loss due to a slight stress occurs in contact with a negative electrode separator of a metal material. However, if the conductivity of the ceramic anode material itself is so low that the other is an anode and the contact is not maintained at uniform and even pressure in all two-dimensional planes (2D planes) with the separator plate, the resistance due to the contact surface loss is greatly increased. Unlike the negative electrode, the contact loss is not recovered by the high conductivity. This leads to rapid resistance increase and voltage decrease, heat generation due to voltage reduction, and concentration of local stress, and the unexpected breakdown of the cell occurs.

The reason why the anode contact loss occurs frequently in the flow end cell is that it differs from other RC repeat structures. This is because other RCs make contact with other relatively mechanically soft RCs, while end cells typically come in contact with end plates that are 5 to 10 times thicker than RCs.

There are three ways to solve this end cell problem.

First, there is a method of constructing the uppermost RC as a dummy cell instead of an actual cell. Such a dummy cell can use a metal plate that does not cause a reaction but has electricity but does not produce a reaction. If a reaction occurs due to the flow of actual fuel and air to produce electricity, the fuel utilization rate decreases and the electricity generation efficiency of the stack itself is lowered There is a problem. The end cell problem can not be solved even if the irreversible cell damage caused by the end cell and the failure of the entire stack can be prevented through a slight reduction of the electric power generation efficiency or through a plurality of dummy structure experiments. The reason for this is that even in the dummy structure, the stress unevenness exists in the same manner, and there is still a portion where the current loss between the end plate and the micelle, between the micelles and the end cell occurs, and the current loss is not caused again .

Secondly, there is a way to make only the uppermost end cell an expensive RC. This method is similar to the method of solving the end cell problem of a polymer fuel cell (PEMFC). The end cell problem of the PEMFC stack is mainly due to the fluidity of the water due to the temperature drop. do. An example of application of the SOFC stack in this scheme is to use noble metals such as platinum, which exhibit high electron conductivity even in a high temperature oxidizing atmosphere, such as a method of printing platinum on the outermost part of the anode of the cell, A method of using a platinum mesh, and the like. However, we have also confirmed that these methods can not be a solution to the end-cell problem through a number of experiments, because the end-cell problem in the SOFC stack does not eliminate the underlying stress imbalance caused by the RC-NRC contact structure And the introduction of platinum should be introduced into the thick film considerably enough to compensate for the current collecting loss of the anode, because the cost loss is too great.

Thirdly, a thick material is put between the end plate and the end cell, for example, a very thick ceramic block such as Al ₂ O ₃ or the like. This method recognizes that the stress unevenness between the end plate and the end cell can not be fundamentally solved, and further reinforces the surface pressure by injecting a more rigid material, which may also improve the performance of the end cell to some extent. There is no inherent stress unevenness resolution and it is not a fundamental alternative.

WO 2006/019295 ('SOFC stack concept', International Publication Date: February 23, 2006)

The present application reduces the chronic anode contact loss of the end cell, thereby preventing performance degradation of the end cell and localized heat and irreversible cell damage caused thereby, thereby achieving performance stabilization of the entire stack and inter-stack performance A stress balancing module capable of improving repetitive reproducibility and a fuel cell including the same.

According to a first aspect of the present invention, there is provided a stress balancing module provided between a fuel cell stack and an upper end plate for pressing the fuel cell stack, wherein the stress balancing module comprises: The present invention provides a stress balancing module in which a metal container is filled with a liquid metal in a hollow metal container having a metal plate of a soft material in contact with the uppermost unit fuel cell.

According to the second embodiment of the present invention, the lower end plate; A fuel cell stack in which at least two unit fuel cells are stacked, one end of which is seated on the lower end plate; An upper end plate provided at the other end of the fuel cell stack to press the fuel cell stack; And a fuel cell stack disposed between the upper end plate and the fuel cell stack, wherein the stress configured to press the uppermost unit cell of the fuel cell stack at a uniform pressure according to a stress distribution of the uppermost unit fuel cell of the fuel cell stack A fuel cell including a balancing module is provided.

According to one embodiment of the present invention, a stress balancing module configured to pressurize a top-end unit fuel cell of a fuel cell stack at a uniform pressure according to a stress distribution of a top-end unit fuel cell of the fuel cell stack, By placing it between the stacked bodies, it is possible to reduce the contact loss of the anode of the end cell, thereby preventing performance degradation of the end cell and local heat generation, thereby preventing irreversible cell damage. It is possible to improve the performance repeatability between stacks.

1 is a configuration diagram of a fuel cell according to an embodiment of the present invention.
Figure 2 illustrates a stress balancing module according to an embodiment of the present invention.
Figure 3 illustrates a stress balancing module according to another embodiment of the present invention.
4 is a phase diagram of copper-tin of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and size of the elements in the drawings may be exaggerated for clarity of description, and the elements denoted by the same reference numerals in the drawings are the same elements.

1 is a configuration diagram of a fuel cell according to an embodiment of the present invention.

1, a fuel cell 100 according to an embodiment of the present invention includes a lower end plate 110, a fuel cell stack 120, an upper end plate 130, a stress balancing module 140, And fastening members 111a and 111b for fastening them.

Specifically, the fuel cell stack 120 in which at least two or more unit fuel cells are stacked in the D direction is mounted on the lower end plate 110, and the upper end plate 130 is mounted on the other end of the fuel cell stack 120 So that the fuel cell stack 120 can be pressurized.

Four-shaft fastening members 111a and 111b may be provided to pressurize the fuel cell stack 120. Four bolts 111a of the four-shaft fastening members 111a and 111b are attached to the four corners of the lower end plate 110 and four bolts 111a are attached to the four corners of the corresponding upper end plate 130. [ Through holes 112 may be formed. Four bolts 111a passing through the four through grooves 112 can be fastened to the four nuts 111b.

In FIG. 1, the four-shaft fastening is shown. However, the present invention is not limited to the two-shaft or three-shaft fastening. 1, the upper end plate 130 may be pressed in the laminating direction by using a pneumatic or hydraulic pressure in addition to the bolt-nut fastening method.

1, a stress balancing module 140 according to an embodiment of the present invention is provided between an upper end plate 130 and a fuel cell stack 120, Unit fuel cell of the fuel cell stack 120 according to the stress distribution of the top-end unit fuel cell of the fuel cell stack 120 according to the present invention.

Figure 2 shows the above-described stress balancing module according to an embodiment of the present invention.

As shown in FIG. 2, the stress balancing module 140 according to an embodiment of the present invention includes a metal plate 141 having a soft material in contact with the uppermost unit fuel cell of the fuel cell stack 120 on one side A hollow metal container, and the metal container may be filled with liquid metal.

On the other hand, the uppermost unit fuel cell of the fuel cell stack 120 contacting the metal plate 141 of a flexible material may be a cathode.

The above-described liquid metal may include a metal present in a liquid state at an operating temperature (for example, 650 to 750 degrees) of the fuel cell stack 120. The liquid metal may be a metal such as tin (Sn), lead (Pb), mercury (Hg) or the like, but should be determined in consideration of the material of the metal plate 141.

The reason is that the metal plate 141 made of a soft material reacts with the liquid metal therein or melts because it constitutes an eutectic phase balance at an operating temperature. Therefore, if the selection of the material of the metal plate 141 made of a soft material is inappropriate, the inner liquid metal may flow out and lose the surface pressure, and it is difficult to eliminate stress unevenness in this state.

In one embodiment, the metal may include tin (Sn), and the metal plate 141 of the flexible material described above may include copper. That is, the 100 percent tin exists in a liquid phase as shown in FIG. 4 at the above-mentioned operating temperature, and does not cause an eutectic reaction with copper which is a material of the metal plate 141.

The portion of the metal container 140 excluding the metal plate 141 described above may be made of a high strength metal including stainless steel (STS). This is for maintaining the shape of the metal container 140 or the like.

The stress balancing module 140 according to an embodiment of the present invention can reduce the stress applied to the surface of the fuel cell stack 120 that is in contact with the uppermost unit fuel cell Even if the flexible metal plate 141 is deformed by the pressure of the liquid metal inside by filling the liquid metal inside the hollow metal container of the fuel cell stack 141, When the stress of the fuel cell stack 140 becomes weak, the fuel cell stack 140 may be swollen again so that the expansion of the unit fuel cell at the uppermost stage of the fuel cell stack 140 may be eliminated and the current collection loss may be recovered. Therefore, the stress balancing module 140 according to an embodiment of the present invention flexibly changes to the stress change of the uppermost unit fuel cell of the fuel cell stack 140, The expansion of the unit fuel cell at the uppermost stage of the fuel cell stack body 140 can be eliminated and the current collection loss can be recovered.

The shape of the stress balancing module 140 may be as shown in Fig.

Specifically, a lower module 141 and 141a including a lower metal plate 141 made of a flexible material and a lower side member 141a extending from the lower metal plate 141, A middle metal container having an upper module 142 and an upper module 142a including an upper side member 142a extending from the upper side member 142a.

That is, as shown in FIG. 2, the upper modules 142 and 142a and the lower modules 141 and 141a may have a symmetrical shape around the rim 143 located at the joint portion.

Although the lower side member 141a and the upper side member 142a are shown extending from the lower metal plate 141 and the upper plate 142 at a certain angle in FIG. 2, The lower side member 141a and the upper side member 142a may be formed vertically in the stacking direction (see D1 in FIG. 1).

Meanwhile, FIG. 3 illustrates a stress balancing module 140 according to another embodiment of the present invention.

The stress balancing module 140 shown in Figure 3 includes a lower module 141 and a lower module 141a including a lower metal plate 141 of a soft material and a lower side member 141a extending from the lower metal plate 141, (Metal) container including the liquid container 142, and the liquid metal described above may be filled in the inside of the metal container.

That is, the stress balancing module 140 shown in FIG. 3 is formed by simply assembling the lower modules 141 and 141a of the stress balancing module 140 shown in FIG. 2 into a plate shape.

As described above, according to one embodiment of the present invention, the stress balancing module configured to pressurize the uppermost unit fuel cell of the fuel cell stack at a uniform pressure according to the stress distribution of the uppermost unit fuel cell of the fuel cell stack, By placing the end plate between the end plate and the fuel cell stack, it is possible to reduce the chronic anode contact loss of the end cell, thereby preventing performance degradation and local heat generation of the end cell and thereby irreversible cell damage, It is possible to improve the overall performance stabilization and the repeatability of the performance between the stacks.

The present application is not limited to the above-described embodiments and the accompanying drawings. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be self-evident.

100: Fuel cell
110: Lower end plate
111a: Bolt
111b: nut
112: Through hole
120: fuel cell laminate
130: upper end plate
140: Stress balancing module
141: Lower metal plate
141a: Lower side member
142: upper plate
142a: upper side member
143: Rim

Claims (17)

A stress balancing module provided between a fuel cell stack and an upper end plate for pressing the fuel cell stack,
The stress balancing module comprises:
A hollow metal container having a metal plate of a soft material in contact with the uppermost unit fuel cell of the fuel cell stack on one surface thereof,
Wherein the metal container is filled with a liquid metal.
The method according to claim 1,
The liquid metal,
And a metal present in a liquid phase at an operating temperature of the fuel cell stack.
The method according to claim 1,
Wherein the metal plate comprises copper,
Wherein the liquid metal comprises tin.
3. The method of claim 2,
The operating temperature of the fuel cell stack
Stress balancing module between 650 and 750 degrees.
The method according to claim 1,
Wherein a portion of the metal container, excluding the metal plate,
Stress balancing module made of high strength metal including stainless steel (STS).
The method according to claim 1,
The stress balancing module comprises:
A lower module comprising a lower metal plate of flexible material and a lower side member extending from the lower metal plate; And
An upper module including an upper plate and an upper side member extending from the upper plate,
Wherein the metal container is filled with a liquid metal.
The method according to claim 6,
Wherein the upper module and the lower module comprise:
Wherein the stress balancing module has a symmetrical shape about a rim located at a junction of the upper module and the lower module.
The method according to claim 1,
The stress balancing module comprises:
A lower module comprising a lower metal plate of flexible material and a lower side member extending from the lower metal plate; And
A hollow metal container including an upper plate,
Wherein the metal container is filled with a liquid metal.
A lower end plate;
A fuel cell stack in which at least two unit fuel cells are stacked, one end of which is seated on the lower end plate;
An upper end plate provided at the other end of the fuel cell stack to press the fuel cell stack; And
A plurality of fuel cell stacks disposed in the upper end plate and the fuel cell stack, and configured to pressurize the uppermost unit fuel cells of the fuel cell stack with a uniform pressure according to a stress distribution of the uppermost unit fuel cell of the fuel cell stack, A fuel cell comprising a module.
10. The method of claim 9,
The stress balancing module comprises:
A hollow metal container having a metal plate of a soft material in contact with the uppermost unit fuel cell of the fuel cell stack on one surface thereof,
Wherein the metal container is filled with a liquid metal.
11. The method of claim 10,
The liquid metal,
And a metal present in a liquid state at an operating temperature of the fuel cell stack.
11. The method of claim 10,
Wherein the metal plate comprises copper,
Wherein the liquid metal comprises tin.
12. The method of claim 11,
The operating temperature of the fuel cell stack
A fuel cell having a temperature between 650 and 750 degrees.
11. The method of claim 10,
Wherein a portion of the metal container, excluding the metal plate,
A fuel cell made of a high strength metal including stainless steel (STS).
10. The method of claim 9,
The stress balancing module comprises:
A lower module comprising a lower metal plate of flexible material and a lower side member extending from the lower metal plate; And
An upper module including an upper plate and an upper side member extending from the upper plate,
Wherein the metal container is filled with a liquid metal.
16. The method of claim 15,
Wherein the upper module and the lower module comprise:
Wherein the fuel cell has a symmetrical shape centered on a rim located at a junction of the upper module and the lower module.
10. The method of claim 9,
The stress balancing module comprises:
A lower module comprising a lower metal plate of flexible material and a lower side member extending from the lower metal plate; And
A hollow metal container including an upper plate,
Wherein the metal container is filled with a liquid metal.

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