WO2017146359A1 - Fuel cell separator plate and fuel cell stack having same - Google Patents

Abstract

Disclosed are a fuel cell separator plate which can maximize power generation efficiency and reduce hydrogen consumption in a fuel cell stack, and a fuel cell stack having the same. The fuel cell separator plate according to the present invention comprises: a separator plate body having a channel part and a manifold part; and a reaction gas flow path disposed in the channel part of the separator plate body and protruding from a first surface to a second surface.

Description

Fuel cell separator and fuel cell stack having same

The present invention relates to a fuel cell separator and a fuel cell stack having the same, and more particularly, to a fuel cell separator capable of maximizing power generation efficiency of a fuel cell stack and reducing hydrogen consumption, and a fuel cell stack having the same. It is about.

A fuel cell stack is a device that produces electricity electrochemically by using hydrogen gas and oxygen gas, and converts fuel (hydrogen) and air (oxygen) continuously supplied from the outside into electrical energy and thermal energy directly by an electrochemical reaction. Device.

The fuel cell stack generates electric power by using an oxidation reaction at the anode and a reduction reaction at the cathode. At this time, a membrane-electrode assembly (MEA) consisting of a catalyst layer containing platinum or platinum-ruthenium metal and a polymer electrolyte membrane is used to promote oxidation and reduction reactions, and a separator is fastened to both ends of the membrane-electrode assembly. Thus, a cell structure is formed.

In the case of the conventional fuel cell stack, the overall characteristics of the fuel cell stack have been improved by improving the material characteristics of the fuel cell separator or by optimizing the driving conditions. There have been attempts to improve performance through an approach that changes the structure of a fuel cell separator, but in the related art, it has been mainly proposed to increase the number of passages of a fuel cell separator or to add an additional meandering passage or an auxiliary passage.

However, the biggest problem among these conventional methods is that the increase in the number of flow paths of the fuel cell separator and the addition of the auxiliary flow paths inevitably increase the size of the separator to increase the size of the entire fuel cell stack. In particular, in recent years, it is applied to a lot of cars, etc. Above all, considering that the miniaturization of the size is the biggest issue, the increase in size or change in shape is the biggest constraint in terms of utilization of the fuel cell stack.

In addition, in the conventional method, even if the area is large in terms of fairness, the size of the mold for manufacturing the fuel cell separator increases, and the initial investment cost of the mold also increases in proportion to the size, thereby increasing the process cost. There is a problem that results.

In particular, the most important in the reaction of the fuel cell stack is the discharge of liquid water generated by the chemical reaction. When water generated by the reaction of oxygen in the cathode of the fuel cell stack accumulates over a certain amount without being immediately discharged from the reaction gas flow path, the supplied fuel is not efficiently delivered to the catalyst layer in contact with the separator plate, thereby causing a reaction zone. Call up the concentration loss at.

Therefore, when it is difficult to discharge moisture, the overall performance of the fuel cell separator and even the fuel cell stack may be degraded to cause instability.

Related prior art documents include Korean Patent Laid-Open Publication No. 10-2007-0093734 (published on September 19, 2007), which discloses a separator for a fuel cell and a fuel cell including the same.

An object of the present invention is to maximize the power generation efficiency of a fuel cell stack and to reduce the hydrogen consumption to prevent the reaction activation area of the fuel cell stack, thereby improving the discharge efficiency of the generated water that interferes with the chemical reaction. It is to provide a fuel cell separator and a fuel cell stack having the same capable of improving performance.

A fuel cell separator according to an embodiment of the present invention for achieving the above object comprises a separator plate body having a channel portion and a manifold portion; And a reaction gas flow passage disposed in the channel portion of the separation plate body and protruding from the first surface to the second surface, wherein the reaction gas flow passage has a lower side corresponding to the channel width longer than an upper side corresponding to the rib width. It has a trapezoidal cross-sectional structure, the length of the rib width is characterized in that 40 to 80% of the length of the channel width.

At least two or more fuel cell stacks according to an embodiment of the present invention for achieving the above object are stacked, the separator plate body having a channel portion and a manifold portion, respectively, disposed in the channel portion of the separator plate body, A plurality of fuel cell separators having a reaction gas flow passage protruding from the surface to the second surface; And a membrane-electrode assembly interposed between the plurality of fuel cell separators, wherein the reaction gas flow path has a trapezoidal cross-sectional structure in which a lower side corresponding to a channel width is longer than an upper side corresponding to a rib width. The length of the rib width is characterized in that 30 to 80% of the length of the channel width.

In the fuel cell separation plate and the fuel cell stack having the same according to the present invention, the mass transfer loss can be suppressed by design change of the reaction gas flow path into a geometrical structure. Loss is suppressed, and as a result, the amount of hydrogen used for power generation is reduced by reducing the amount of hydrogen injected, and thus the conversion efficiency can be improved, resulting in an increase in power generation and an increase in total power density.

In addition, the fuel cell separator and the fuel cell stack having the same according to the present invention can ensure a uniform fuel distribution throughout the fuel cell stack through the change in the geometry of the reaction gas flow path, and the gas diffusion layer, the anode and the cathode It effectively removes water, which is a reaction byproduct, and reduces the pressure drop at the inlet and outlet when hydrogen, the fuel fluid, passes through the reaction gas flow path, so that the gas is evenly distributed in the entire flow path of the separator plate. As a result, the reaction efficiency and lifespan improvement of the fuel cell stack can be secured because it is not concentrated on a specific part.

1 is a perspective view showing a fuel cell stack according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a portion of the fuel cell separator and the membrane-electrode assembly of FIG. 1; FIG.

3 is an enlarged cross-sectional view of a reaction gas flow path of FIG. 2;

Figure 4 is a graph showing the I-V characteristics of the fuel cell stack applying the fuel cell separator prepared according to Examples 1 to 4 and 1 in comparison.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a fuel cell separator and a fuel cell stack having the same according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a fuel cell stack according to an embodiment of the present invention.

Referring to FIG. 1, a fuel cell stack 100 according to an exemplary embodiment of the present invention includes a plurality of fuel cell separators 110 and a membrane-electrode assembly 120. In addition, the fuel cell stack 100 according to the embodiment of the present invention may further include a gas diffusion layer (not shown) and the end plate 130.

At least two fuel cell separator plates 110 are stacked on the separator plate body 112, each having a channel portion and a manifold portion, and disposed on a channel portion of the separator plate body 112. And a reaction gas flow passage 114 protruding from the second surface to the second surface. The fuel cell separator 110 has a low structural permeability to maintain a constant shape and low gas permeability.

The membrane-electrode assembly 120 is interposed between the plurality of fuel cell separators 110, respectively. The membrane-electrode assembly 120 includes an electrolyte membrane capable of moving hydrogen cations and an anode and a cathode, which are catalyst layers coated on both surfaces of the electrolyte membrane so that hydrogen and oxygen can react.

Although not shown in detail in the drawings, a gas diffusion layer (Gas Diffusion) is a porous medium for uniformly dispersing the reaction gas to the surface of the membrane-electrode assembly 120 between the fuel cell separator 110 and the membrane-electrode assembly 120. Layer: GDL) may be inserted.

The end plate 130 is disposed at the outermost portion of the plurality of fuel cell separators 110 and the membrane-electrode assembly 120 to support the plurality of fuel cell separators 110 and the membrane-electrode assembly 120. Play a role. The end plate 130 supports the plurality of fuel cell separators 110, the membrane-electrode assembly 120, and the gas diffusion layer, and supplies hydrogen, which is a reaction gas, to the channel portion of the fuel cell separator 110. It serves as an inlet for In this case, the end plate 130 may be formed of anodized aluminum for the purpose of securing insulation with the membrane-electrode assembly 120 while ensuring proper strength, but is not limited thereto.

A brief description of the principle of generating electrical energy for the fuel cell stack 100 having the above-described configuration is as follows.

First, an oxidation reaction of hydrogen proceeds at the anode to generate hydrogen ions (protons) and electrons (electrons), and the hydrogen ions and electrons move to the cathode through the electrolyte membrane and the fuel cell separator 110, respectively. Thereafter, the cathode generates an electrochemical reaction in which hydrogen ions, electrons, and oxygen in the air participate to generate water, and electrical energy is generated by the flow of electrons between the anode and the cathode.

That is, the hydrogen supplied to the anode is decomposed into hydrogen ions (H ⁺ ) and electrons (electron, e ⁻ ), and the decomposed hydrogen ions pass through the electrolyte to the cathode, where the hydrogen ions migrated from the anode and it generates electrical energy through a reaction of the oxygen supplied to the cathode, and generates heat and at the same time meet the electrode to produce water ^- (H ⁺⁾ and a mobile electronic through the external conductors (electron, e).

Hereinafter, a fuel cell separator according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is an enlarged perspective view of a portion of the fuel cell separator and the membrane-electrode assembly of FIG. 1, and FIG. 3 is an enlarged cross-sectional view of the reaction gas flow path of FIG. 2.

2 and 3, the fuel cell separator 110 according to the exemplary embodiment of the present invention includes a separator body 112 and a reaction gas flow passage 114. In addition, the fuel cell separator 110 according to the embodiment of the present invention may further include a cooling passage 116 and a gasket (not shown).

The separator plate body 112 has a channel portion disposed at the center portion and a manifold portion disposed at the edge. The separator body 112 may have a low permeability of gas and a metal material having sufficient structural strength to maintain a constant shape, but is not limited thereto.

The reaction gas flow passage 114 is disposed in the channel portion of the separator plate body 112 and protrudes from the first surface to the second surface. Accordingly, the reaction gas flow passage 114 is disposed to face the membrane-electrode assembly 120. The reaction gas flow passage 114 has a trapezoidal cross-sectional structure in which the bottom side corresponding to the channel width w1 is longer than the top side corresponding to the rib width w2.

The cooling flow path 116 is disposed between the spaced portions of the reaction gas flow paths 114 protruding from the first surface to the second surface. The cooling passage 116 may be an air passage through which air passes or a cooling water passage through which cooling water passes.

Although not shown in detail in the drawings, the gasket is attached along the boundary of the channel portion and the manifold portion of the separator plate body 112 to prevent leakage of the working fluid. These gaskets are formed for the purpose of securing airtightness and facilitating fastening between the fuel cell separators 110 when the fuel cell separators 110 are stacked. The material may be a rubber material. Only one example, a plastic material may be used.

In particular, as shown in FIG. 3, the reaction gas flow passage 114 has a geometric structure because the length of the rib width w2 is designed to be 30 to 80% of the length of the channel width w1.

At this time, when the length of the rib width w2 is less than 30% of the length of the channel width w1, the flow formability is deteriorated, and the difference between the length of the bottom side and the top side of the reaction gas flow passage 114 is increased. There is a problem that the pressure distribution in the upper portion and the lower portion of the flow passage 114 is uneven, so that the switching efficiency of the fuel cell stack (100 in FIG. 1) is lowered. On the contrary, when the length of the rib width w2 exceeds 80% of the length of the channel width w1, the inner angle θ of the reaction gas flow passage 114 having the trapezoidal cross-sectional structure becomes large. In the case of less than%, the moldability is lowered, and in severe cases, molding of the reaction gas flow path 114 itself may be impossible. In addition, it is difficult to secure the cooling water flow path, which leads to a decrease in the cooling performance of the fuel cell stack, thereby causing an overall decrease in performance.

In addition, when the length of the rib width w2 exceeds 80% of the length of the channel width w1, the supply of fuel gas and the discharge of unreacted substances / reaction products (mainly H ₂ O, etc.) are not smooth. This results in a decrease in operating performance of the battery stack and a shortened lifespan. For example, when the reaction product water is not discharged smoothly from the cathode, water flooding occurs, which interferes with the mass transfer of the entire fuel cell stack, thereby operating the fuel cell stack. Resulting in reduced performance and reduced lifespan.

For this purpose, it is preferable that the channel width w1 has a length of 0.9 to 1.2 mm, and the rib width w2 has a length of 0.4 to 0.7 mm. In this case, the sum total length of the channel width w1 and the rib width w2 is preferably fixed at 1.4 to 1.8 mm.

Because, when the combined length of the channel width w1 and the rib width w2 increases or decreases out of the above range, the change in the overall length of the single flow path is performed by the repetition of the single flow path of the fuel cell separation plate 110. Since it acts as a factor for changing the overall size, there is a problem in that the overall design of the fuel cell stack needs to be changed. This, in turn, acts as a factor that increases or decreases the size of the mold for manufacturing the fuel cell separator 110, which inevitably leads to an increase in process cost.

In contrast, in the present invention, by fixing the summation length of the channel width w1 and the rib width w2 in a strictly limited range of 1.4 to 1.8 mm, the increase in the overall length and volume of the reaction gas flow passage 114 is minimized. In addition, by changing the length of the channel width (w1) and the rib width (w2) of the reaction gas flow path 114 in the same or similar volume, by designing a geometric structure, the mold replacement for manufacturing the fuel cell separator 110 Is unnecessary, so the process cost does not increase.

As such, when the reaction gas flow path 114 is designed in a geometric structure having the length of the rib width w2 having 30 to 80% of the length of the channel width w1, the consumption of hydrogen, which is the reaction gas, is reduced. The hydrogen used for the overall reduction is reduced, and the power generation output, that is, the conversion efficiency is increased compared to the used hydrogen. Accordingly, water can be effectively removed as well as conversion efficiency because water, which is a product that interferes with power generation of the fuel cell stack, can be effectively removed.

At this time, it is preferable that the reaction gas flow passage 114 has a height of 0.5 to 0.7 mm, which should be designed in the above range so that the pressure drop decreases when hydrogen, which is a fuel fluid, passes through the reaction gas flow passage 114. This can be distributed to increase mass transfer and reaction efficiency of the fuel cell stack.

More preferably, the reaction gas flow passage 114 has an equilateral trapezoidal cross-sectional structure in which the inner angles θ formed by the connecting lines between the bottom and bottom vertices B and C and the top and bottom vertices A and D are the same. .

As such, when the reaction gas flow passage 114 is designed to have a conformal trapezoidal cross-sectional structure, a pressure drop is reduced when hydrogen, which is a fuel fluid, passes through the reaction gas flow passage 114, and thus it is distributed at an even pressure, so that mass transfer and reaction efficiency of the fuel cell stack can be achieved. Because it can increase.

At this time, the inner angle θ of the reaction gas flow path 114 having an equilateral trapezoidal cross-sectional structure preferably has a 55 to 85 °. When the inner angle θ of the reaction gas flow passage 114 is less than 55 °, the difference in length between the bottom side and the upper side portion of the reaction gas flow passage 114 is increased, and the pressure distribution at the upper portion and the lower portion of the reaction gas flow passage 114 is increased. The nonuniformity causes a problem that the conversion efficiency of the fuel cell stack is lowered. On the contrary, when the internal angle θ of the reaction gas flow passage 114 exceeds 85 °, there is a high possibility that the formability of the fuel cell separator 110 may be very poor due to the excessive angle design close to the right angle, and the reaction gas. Molding of the flow path 114 itself may become impossible.

In the fuel cell separator according to the embodiment of the present invention described above, the mass transfer loss can be suppressed by design change of the reaction gas flow path into a geometric structure. When the mass transfer loss is suppressed, the concentration of the reactant at the electrode surface is lost. This is suppressed, and as a result, the amount of hydrogen used for power generation is reduced by reducing the loss amount compared to the injected hydrogen, so that the conversion efficiency can be improved, and as a result, the power generation amount increases and thus the total power density increases.

In this case, the mass transfer loss is closely related to the product water discharge as well as the change of the concentration of the reactant at the electrode surface. The product water discharge is a developmental part, and the fuel is effectively delivered to the entire separator due to the smooth discharge of the product water generated as a by-product of the reaction, blocking the gas diffusion layer and the anode and the cathode. It can prevent the output drop.

Therefore, the fuel cell separator according to the embodiment of the present invention can secure a uniform fuel distribution throughout the fuel cell stack by changing the geometry of the reaction gas flow path, and the reaction by-products filled in the gas diffusion layer, the anode and the cathode. It effectively removes phosphorus and reduces the pressure drop at the inlet and outlet when the hydrogen, the fuel fluid, passes through the reaction gas flow path so that the gas is evenly distributed over the entire flow path of the separator plate. As it is not concentrated on the part, it is possible to secure reaction efficiency and lifespan improvement of the fuel cell stack.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

1. Specimen Manufacturing

Fuel cell separators according to Examples 1 to 4 and Comparative Example 1 were prepared under the conditions of Table 1. At this time, the fuel cell separator according to Examples 1 to 4 and Comparative Example 1 has 50 mm (width) × 50 mm (length), and the flow path has a height of 0.6 mm.

TABLE 1

2. Property evaluation

Table 2 shows the results of measuring the moisture content after the final reaction to the fuel cell stack to which the fuel cell separator prepared according to Examples 1 to 4 and Comparative Example 1 is applied.

TABLE 2

As shown in Table 1 and Table 2, the discharged water content after the final reaction based on the rib width of the reaction gas flow path was compared with each other, this discharged water content refers to the amount of discharged water produced.

It can be seen that this discharge generated water shows the maximum value in Examples 2 and 3.

Table 3 shows the result of measuring the amount of reactive hydrogen after the final reaction to the fuel cell stack to which the fuel cell separator prepared according to Examples 1 to 4 and Comparative Example 1 is applied. At this time, in order to calculate the amount of hydrogen used for the reaction, the amount of hydrogen after the reaction from the discharged water was calculated, and the initial input water content was 74.30%.

TABLE 3

As shown in Table 3, the amount of exhaust hydrogen gradually decreased due to the use of hydrogen in the reaction for the cell output of the fuel cell stack.

At this time, the hydrogen reduction order was Example 4> Comparative Example 1> Example 3> Example 1> Example 2. That is, in Example 4, the amount of reactive hydrogen was the smallest, and in Example 2, the amount of reactive hydrogen was the highest.

Table 4 shows the results of measuring the total power density after the final reaction for the fuel cell stack to which the fuel cell separator prepared according to Examples 1 to 4 and Comparative Example 1 is applied, and FIG. 4 shows Examples 1 to 4 and 4 is a graph showing IV characteristics of a fuel cell stack to which a fuel cell separator prepared according to 1 is applied.

TABLE 4

As shown in Table 4 and FIG. 4, it can be seen that the I-V characteristics and the total power density of the fuel cell stack increase when the rib width and the channel width are increased.

In particular, a fuel cell stack employing a fuel cell separator manufactured according to Example 3, which has a rib width and a channel width of 0.6 mm / 1.0 mm, is the most preferable flow path in view of discharged water, hydrogen reduction rate, and total power density. It was confirmed that it has a design structure.

Although the above has been described with reference to the embodiments of the present invention, various changes and modifications can be made at the level of those skilled in the art. Such changes and modifications can be said to belong to the present invention without departing from the scope of the technical idea provided by the present invention. Therefore, the scope of the present invention will be determined by the claims described below.

Claims (10)

1. A separator body having a channel portion and a manifold portion; And

   It is disposed in the channel portion of the separation plate body, the reaction gas flow path protruding from the first surface to the second surface;

   The reaction gas flow path has a trapezoidal cross-sectional structure in which the lower side corresponding to the channel width is longer than the upper side corresponding to the rib width.

   The length of the rib width is 30 ~ 80% of the length of the channel width of the fuel cell separation plate.
2. The method of claim 1,

   The fuel cell separator is

   And a cooling flow passage disposed between the reaction gas flow passages protruding from the first surface to the second surface.
3. The method of claim 1,

   The channel width is

   A fuel cell separation plate having a length of 0.9 ~ 1.2mm, the rib width has a length of 0.4 ~ 0.7mm.
4. The method of claim 1,

   The sum length of the channel width and the rib width is

   Fuel cell separator plate 1.4 ~ 1.8mm.
5. The method of claim 1,

   The reaction gas flow path is

   A fuel cell separator having a height of 0.5 to 0.7 mm.
6. The method of claim 1,

   The reaction gas flow path is

   A fuel cell splitter plate having an equilateral trapezoidal cross-sectional structure with equal internal angles formed by a connecting line between a bottom side and both vertices of the bottom and upper vertices.
7. The method of claim 6,

   The cabinet

   Fuel cell separator with 55 to 85 °.
8. The method of claim 1,

   The fuel cell separator is

   And a gasket attached along a boundary of a channel portion and a manifold portion of the separator plate body.
9. At least two or more sheets are stacked, the plurality of fuel cells each having a separator plate body having a channel portion and a manifold portion, and a reaction gas flow passage disposed in the channel portion of the separator plate and protruding from the first surface to the second surface. Separators; And

   And a membrane-electrode assembly interposed between the plurality of fuel cell separators, respectively.

   The reaction gas flow path has a trapezoidal cross-sectional structure in which the lower side corresponding to the channel width is longer than the upper side corresponding to the rib width.

   The length of the rib width is 30 ~ 80% of the length of the channel width fuel cell stack.
10. The method of claim 9,

    The fuel cell stack

    A gas diffusion layer disposed between the fuel cell separator and the membrane-electrode assembly;

    The fuel cell stack further comprises an end plate disposed at an outermost portion of the plurality of fuel cell separators and the membrane-electrode assembly to support the plurality of fuel cell separators and the membrane-electrode assembly.

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