JP2005158610A - Fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery capable of equalizing moisture distribution in an air path with a simple structure while keeping design flexibility of a cooling water path, the air path or the like. <P>SOLUTION: A cell 10 structuring a fuel battery is equipped with an MEA and a separator 12 arranged to be contacted to the MEA. The separator 12 is provided with an oxidant gas path 20 for having oxidant gas pass to a side contacting to the MEA and a cooling medium path 22 for having a cooling medium pass to a side farther from the MEA than the oxidant gas path 20, as well as a thermal resistance means 12a between the oxidant gas path 20 and the cooling medium path 22, at a part corresponding to a downstream part 20c of the oxidant gas path 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell that generates electric energy by an electrochemical reaction between hydrogen and oxygen, and is effective when applied to a generator for a moving body such as a vehicle, a ship, and a portable generator, or a generator for home use. is there.

  In a fuel cell system that generates electricity using an electrochemical reaction between hydrogen and oxygen, water produced by the electrochemical reaction is generated on the air electrode side inside the fuel cell. Such generated water tends to have excessive moisture on the air passage outlet side. When the moisture becomes excessive in this way, the electrode is covered with water, the gas permeation is inhibited, and the output of the fuel cell is lowered. On the other hand, moisture tends to be insufficient on the air passage inlet side, and when the moisture is insufficient, the electrolyte membrane dries and the output of the battery decreases. Therefore, it is necessary to keep the water content in the fuel cell appropriate.

In order to solve such problems, the temperature distribution in the cell surface is increased from the air passage inlet side to the air passage outlet side to increase the saturated vapor pressure on the air passage outlet side, and moisture on the air passage outlet side is increased. A method of operating a fuel cell that facilitates discharge has been proposed (see, for example, Patent Document 1). Further, a fuel cell has been proposed in which the air passage inlet side and the hydrogen passage outlet side are made to correspond, the air passage outlet side and the hydrogen passage inlet side are made to correspond, and the moisture distribution in each of the air passage and the hydrogen passage is made uniform. (For example, refer to Patent Document 2).
Japanese Patent Application Laid-Open No. 8-111230 JP 2002-184428 A

  However, in the method described in Patent Document 1, it is necessary to control the temperature and flow rate of the cooling medium in order to form the cell surface temperature distribution, and the configuration becomes complicated. Further, when the temperature distribution in the cell surface is formed by controlling the temperature and flow rate of the cooling medium, it is difficult to form the temperature distribution as intended, and the degree of freedom in designing the cooling water passage is reduced. Also in the fuel cell described in Patent Document 2, the degree of freedom in designing the air passage and the hydrogen passage is limited.

  An object of the present invention is to provide a fuel cell capable of making the water distribution uniform in the air passage with a simple configuration while ensuring the degree of freedom in designing the cooling water passage and the air passage. To do.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a cell (10) for generating an electric energy by electrochemically reacting an oxidizing gas mainly composed of oxygen and a fuel gas mainly composed of hydrogen. A plurality of stacked fuel cells, the cell (10) includes an MEA (11) and a separator (12) disposed so as to be in contact with the MEA (11). An oxidizing gas passage (20) through which oxidizing gas passes is provided on the side in contact with the MEA (11), and a cooling medium passage (through which the cooling medium passes through the side farther from the MEA (11) than the oxidizing gas passage (20) ( 22) is provided, and the separator (12) is provided between the oxidizing gas passage (20) and the cooling medium passage (22) at a portion corresponding to the downstream portion (20c) of the oxidizing gas passage (20). Heat resistance Is characterized in that (12a, 13) are provided.

  In the MEA (11), heat is generated due to the electrochemical reaction, but at a portion corresponding to the downstream portion (20c) of the oxidizing gas passage (20), between the oxidizing gas passage (20) and the cooling medium passage (22). By providing the thermal resistance means (12a), the temperature at this portion is higher than the upstream portion of the air passage (20), and a temperature distribution can be reliably formed in the cell plane. For this reason, since the saturated vapor pressure of air rises in the air passage downstream portion (20c), the amount of moisture contained in the air and discharged becomes large. On the other hand, since the temperature is relatively low in the upstream portion of the air passage (20), the saturated vapor pressure of air is low. For this reason, the amount of moisture contained and discharged in the air is reduced. Thereby, it is possible to make the moisture distribution in the air passage (20) uniform while ensuring a degree of freedom in designing the cooling water passage, the air passage and the like with a simple configuration in which only the heat resistance means is provided.

  Specifically, the thermal resistance means may include an air layer (1) as in the invention described in claim 2, and the cooling medium passage (22) as in the invention described in claim 3. Or the oxidant gas passage (20) side of the cooling medium passage (22) as in the invention described in claim 4. The material (13) having a lower thermal conductivity than the separator (12) provided on the surface of the substrate may be included.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, a fuel cell according to an embodiment to which the present invention is applied will be described with reference to FIGS. FIG. 1 is a conceptual diagram illustrating a configuration of a fuel cell 100 according to the present embodiment. FIG. 1A is a perspective view of the fuel cell 100 and FIG. 1B is an exploded perspective view of a single cell 10.

In the first embodiment, a solid polymer electrolyte membrane type fuel cell is used as the fuel cell 100. As shown in FIG. 1A, the fuel cell 100 is formed by stacking a plurality of single cells 10 as basic units and electrically connecting them in series. In the fuel cell 100, when hydrogen and oxygen are supplied, the following electrochemical reaction occurs and electric energy is generated.
(Hydrogen electrode) H ₂ → 2H ⁺ + 2e ⁻
(Oxygen electrode) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
Inside the fuel cell 100, there are an air passage for supplying air to each cell 10, a hydrogen passage for supplying hydrogen to each cell 10, and a cooling water passage for supplying cooling water to each cell 10, respectively. Formed (not shown). As shown in FIG. 1A, on one side of the fuel cell 100, an air passage inlet 101a and an air passage outlet 101b, a hydrogen passage inlet 102a and a hydrogen passage outlet 102b, and a cooling water passage inlet 103a are provided. The cooling water passage outlet 103b is formed. Air corresponds to the oxidizing gas of the present invention, and hydrogen corresponds to the fuel gas of the present invention.

  Air is supplied into the fuel cell 100 from an air supply device (not shown), and hydrogen is supplied into the fuel cell 100 from a hydrogen supply device (not shown). Further, cooling water as a cooling medium is supplied to the fuel cell 100 from a cooling system (not shown). In this example, general antifreeze cooling water (LLC) is used as the cooling water.

  Air flows into the fuel cell 100 from the air passage inlet 101a, passes through the cells 10 in the stacking direction, passes through the inside of each cell 10, and then flows out of the air passage inlet 101a. Similarly, hydrogen flows into the fuel cell 100 from the hydrogen passage inlet portion 102a, passes through each cell 10 in the stacking direction, passes through the inside of each cell 10, and then flows out from the hydrogen passage inlet portion 102a. Further, similarly, the cooling water flows into the fuel cell 100 from the cooling water passage inlet 103a, penetrates each cell 10 in the stacking direction, and passes through the inside of each cell 10, and then flows out from the cooling water passage inlet 103a. To do.

  As shown in FIG. 1B, the single cell 10 is composed of an MEA (Membrane Electrode Assembly) 11 and a separator 12 sandwiching the MEA from both sides. The MEA 11 is composed of an electrolyte membrane made of a proton conductive ion exchange membrane and electrodes arranged on both side surfaces thereof. The electrode is composed of a catalyst layer and a gas diffusion layer. One electrode is configured as an oxygen electrode (positive electrode) to which oxygen is supplied, and the other electrode is configured as a hydrogen electrode (negative electrode) to which hydrogen is supplied. A load (not shown) is connected to these electrodes, and the electric power generated in the fuel cell 100 is supplied to the load.

  The separator 12 is formed of a conductive member (for example, a carbon material) that does not transmit gas. The separator 12 is formed with an air passage inlet 20a and an air passage outlet 20b, a hydrogen passage inlet 21a and a hydrogen passage outlet 21b, a cooling water passage inlet 22a and a cooling water passage outlet 22b, respectively.

  FIG. 2 is a conceptual diagram showing the internal configuration of the cell 10, FIG. 2 (a) shows the configuration of the air passage 20, and FIG. 2 (b) shows the configuration of the cooling water passage 22.

  Inside the cell 10, a groove (not shown) is formed on the surface of the separator 12 in contact with the MEA 11 to form a gas passage. An air passage 20 through which air passes is formed on the side in contact with the oxygen electrode of the separator 12 (FIG. 2A), and a hydrogen passage through which hydrogen passes is formed on the side in contact with the hydrogen electrode (not shown). ). A cooling water passage 22 through which cooling water passes is formed inside the separator 12 (FIG. 2B). The air passage 20 corresponds to the oxidizing gas passage of the present invention, and the cooling water passage 22 corresponds to the cooling medium passage of the present invention.

  In the fuel cell 100, when the hydrogen and oxygen are supplied, the above-described electrochemical reaction occurs, generating water is generated on the oxygen electrode side, and excess water remains in the air passage 20. This residual water is generated because the vapor pressure of the air becomes saturated and condensed water is generated downstream from the upstream side of the air passage. Here, the air passage downstream portion 20 indicates a region from the vicinity of the center of the air passage 20 to the air passage outlet portion 20b.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 and shows a cross-sectional configuration of the cell 10 in the downstream portion 20 c of the air passage 20. FIG. 3 shows only the air electrode side of the MEA 11. As shown in FIG. 3, an air layer 12 a as a thermal resistance means is formed on the downstream portion 20 a of the air passage 20 in the separator 12 on the side close to the cooling water passage 22. The air layer 12 a is formed by providing a groove or a cavity inside the separator 12. The thermal resistance means may be provided between the air passage 20 and the cooling water passage 22 and is preferably provided as close as possible from the air passage 20.

  Here, the temperature of the separator 12 (= gas) is determined by the difference between the amount of heat transferred from the MEA 11 to the separator 12 and the amount of heat transferred from the separator 12 to the cooling water through the air layer 12a. The amount of heat is proportional to the temperature difference between the two (for example, determined by the temperature difference between the separator 12 and the air layer 12a).

  FIG. 4 is a characteristic diagram showing the temperature distribution inside the cell 10 in the air passage downstream portion 20c. As shown in FIG. 4, the temperature between the electrolyte 11 and the separator 12 is substantially the same. On the other hand, between the separator 12 and the cooling water, the air layer 12a becomes a thermal resistance and a large temperature difference is formed. That is, due to the presence of the air layer 12a, the temperature difference between the separator 12 and the air layer 12a, and the air layer 12a and the adjacent portions of the cooling water are reduced, and the amount of heat transfer is reduced. Thereby, as compared with the case where there is no thermal resistance, a large amount of heat generated in the MEA 11 is used to raise the temperature of the separator 12 (= gas), and the temperature of the separator 12 (= gas) can be kept high. Thereby, the temperature of the air passage downstream portion 20 c in the separator 12 can be made higher than the upstream side of the air passage 20.

  Next, the operation of the fuel cell 100 of this embodiment will be described.

  First, in the fuel cell 100, when the hydrogen and oxygen are supplied, the electrochemical reaction occurs to generate power. At this time, generated water is generated on the oxygen electrode side of the MEA 11, and excess water accumulates as residual water in the downstream portion 20 c of the air passage 20. Further, the MEA 11 generates heat along with the power generation, and this heat is transmitted to the MEA 11 → the separator 12 → the cooling water, and the MEA 11 and the separator 12 are cooled.

  As described above, in the air passage downstream portion 20c in the separator 12, the temperature is higher than that in the air passage upstream portion due to the presence of the air layer 12a, and a temperature distribution can be reliably formed in the cell plane. For this reason, since the saturated vapor pressure of air rises in the air passage downstream portion 20c, the amount of moisture contained and discharged is increased. On the other hand, since the temperature is relatively low in the upstream portion of the air passage 20, the saturated vapor pressure of the air is low. For this reason, the amount of moisture contained and discharged in the air is reduced. Thereby, in the downstream part 20c in which moisture tends to accumulate in the air passage 20, the discharge of moisture can be promoted, and in the upstream part where drying is easy, the discharge of moisture can be suppressed, and the moisture distribution in the air passage 20 can be made uniform. . As a result, it is possible to suppress the output of the fuel cell 100 from being reduced due to excessive moisture at the air passage downstream portion 20c, and to prevent the output from the fuel cell 100 from being reduced due to insufficient moisture at the upstream portion of the air passage.

(Other embodiments)
In the above embodiment, the heat resistance means is configured by the air layer 12a formed on the cooling water passage 22 side of the separator 12. However, the heat resistance means is not limited to this, and other means shown in FIG. 5 or FIG. It can also be configured. 5 and 6 show a cross-sectional configuration of the cell 10 in the air passage downstream portion 20c, and correspond to FIG. 3 of the above embodiment.

  For example, as shown in FIG. 5, the heat resistance means can be configured by subjecting the surface of the cooling water passage 22 in the separator 12 to a water repellent treatment. Thereby, the contact area of the separator 12 and cooling water can be reduced, and the amount of heat transfer can be reduced. Moreover, as shown in FIG. 6, a thermal resistance means can be comprised by apply | coating the material 13 with low heat conductivity to the surface of the cooling water channel | path 22 in the separator 12. As shown in FIG. The low heat conductive material 13 should just be a material whose heat conductivity is lower than the separator 12, for example, can use resin materials, such as an epoxy. These thermal resistance means may be used alone or in any combination.

  The air passage downstream portion 20 provided with the heat resistance means does not have to be the entire region from the vicinity of the center of the air passage 20 to the air passage outlet portion 20b, and may be a part thereof.

It is a conceptual diagram which shows the structure of the fuel cell of the said embodiment. It is a conceptual diagram which shows the structure inside a cell. It is AA sectional drawing of FIG. 2, and is sectional drawing of the cell in an air path downstream part. It is a characteristic view which shows the temperature distribution inside the cell in an air passage downstream part. It is sectional drawing of the cell in the air passage downstream part which concerns on the modification of this invention. It is sectional drawing of the cell in the air passage downstream part which concerns on the modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Fuel cell, 10 ... Cell, 11 ... MEA (membrane electrode complex), 12 ... Separator, 13 ... Low heat conductive material, 20 ... Air passage, 20c ... Air passage downstream part, 22 ... Cooling water passage.

Claims (4)

A fuel cell in which a plurality of cells (10) for generating an electric energy by electrochemically reacting an oxidizing gas containing oxygen as a main component and a fuel gas containing hydrogen as a main component,
The cell (10) includes an MEA (11) having a pair of electrodes disposed on both sides of an electrolyte membrane, and a separator (12) disposed to contact the MEA (11).
The separator (12) is provided with an oxidizing gas passage (20) through which the oxidizing gas passes on the side in contact with the MEA (11) and from the MEA (11) through the oxidizing gas passage (20). A cooling medium passage (22) through which the cooling medium passes is provided on the far side;
The separator (12) has a thermal resistance means (between the oxidizing gas passage (20) and the cooling medium passage (22) at a portion corresponding to the downstream portion (20c) of the oxidizing gas passage (20). 12a, 13) is provided. The fuel cell according to claim 1, wherein the thermal resistance means includes an air layer (1). The said thermal resistance means is comprised including the water-repellent process given to the surface by the side of the said oxidation gas channel | path (20) in the said cooling medium channel | path (22). Fuel cell. The thermal resistance means includes a material (13) having a lower thermal conductivity than the separator (12) provided on the surface of the cooling medium passage (22) on the oxidizing gas passage (20) side. The fuel cell according to any one of claims 1 to 3, wherein:

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