JPH05190193A - Solid high polymeric electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To improve reliability by preventing the condensation of the moisture in a cathode by increasing the cooling efficiency on the surface in contact with a fuel gas feeding means higher than the cooling efficiency of an oxidizing agent gas feeding means. CONSTITUTION:A single cell 1 is constituted by arranging a cathode 2 and an anode 4 on both the sides of a membrane 3. Fuel gas is supplied into the anode 4 through a fuel gas passage 5 and oxidizing agent gas is supplied into the cathode 2 through an oxidizing agent gas flow passage 10. A cooling plate 8 consists of a gas impermeable sintered carbon plate, and when the distance from the edge surface opposed to the anode in the thickness direction is set to L1 and the distance from the edge surface opposed to the cathode is set to L2, a cooling water passage 7 is formed at the position in L1<L2. Accordingly, the temperature of the cathode is raised higher than that of the anode, and the condensation of the moisture in the cathode is prevented, and the flow passage for the oxidizing agent gas is secured, and reliability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable proton conductive solid polymer electrolyte fuel cell having a cooling plate.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is formed by disposing an anode or a cathode and an electrode base material on each of two main surfaces of a solid polymer electrolyte membrane. Each anode or cathode electrode is sandwiched between the solid polymer electrolyte membrane and the electrode base material. The solid polymer electrolyte membrane uses a polystyrene cation exchange membrane with sulfonic acid groups as the cation conductive membrane, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or trifluoroethylene grafted to the fluorocarbon matrix. However, recently, a perfluorocarbon sulfonic acid membrane has been used to extend the life of a fuel cell.

The solid polymer electrolyte membrane has a proton (hydrogen ion) exchange group in the molecule, and when it is saturated to contain water, it exhibits a specific resistance of 20 Ω · cm or less at room temperature and functions as a proton conductive electrolyte. The saturated water content changes reversibly with temperature. The electrode base material is a porous body and functions as a reaction gas supply means or a reaction gas discharge means of the fuel cell and a current collector. At the anode or cathode electrode, a three-phase interface is formed and an electrochemical reaction occurs.

At the anode, the reaction of the formula (1) occurs. H ₂ = 2H ⁺ + 2e (1) At the cathode, the reaction of the formula (2) occurs. 1/20 ₂ + 2H ⁺ + 2e = H ₂ O (2) That is, at the anode, hydrogen supplied from the outside of the system produces protons and electrons. The generated protons move in the ion exchange membrane toward the cathode, and the electrons move to the cathode through an external circuit. On the other hand, in the cathode, oxygen supplied from the outside of the system reacts with protons moving from the anode in the ion exchange membrane and electrons moving from the external circuit to generate water.

In such a solid polymer electrolyte fuel cell, protons move in a hydrated state as they move from the anode to the cathode in the ion exchange membrane, so that the water content near the anode decreases and the ion exchange occurs. The film is getting dry. Therefore, it becomes difficult for protons to move near the anode unless water is supplied. When air is used as the oxidant, several times the theoretical consumption of air is sent, and the moisture in the ion-exchange membrane is carried out to the air, which causes the membrane to dry. For this reason, conventionally, a method has been adopted in which a fixed amount of water vapor, which is calculated as an appropriate amount, is mixed into the fuel gas and / or the oxidant gas and sent into the battery.

On the other hand, the solid polymer electrolyte fuel cell, like other fuel cells, radiates heat to the outside along with power generation, so that it is necessary to remove the generated heat in order to continue stable operation. is there. The fact that cooling is necessary is the same as that of other types of fuel cells, but in the case of solid polymer electrolyte fuel cells, the operating temperature itself is lower than that of other types of fuel cells, and protons are also used. The proton conductivity of the conductive solid polymer membrane itself is greatly affected by temperature.
A phosphoric acid fuel cell (PAFC) that operates near 0 ° C,
Molten carbonate fuel cell (MCF operating at about 650 ° C)
C), and more precise temperature control is required as compared with a solid oxide fuel cell (SOFC) operating at about 1000 ° C. When a solid polymer membrane having proton conductivity is used as an electrolyte, its operating temperature is generally 100 ° C. or lower except for special cases.

9 and 10 are sectional views showing a conventional solid polymer electrolyte fuel cell. In the figure, 1 indicates a single cell composed of a cathode-membrane-anode. Figure 9
Shows a case where gas supply ribs are provided on the gas separator, and FIG. 10 shows an example of using a so-called ribbed electrode base material in which ribs are provided on the electrode base material. Moreover, 8 shows a cooling plate. In the conventional technique, the position of the coolant passage provided on the cooling plate is generally provided at the center of the cooling plate in the thickness direction.

[0008]

However, in the conventional solid polymer electrolyte fuel cell, moisture condenses on the electrodes over time and the diffusivity of the reaction gas such as the fuel gas and the oxidant gas is hindered and the fuel is There is a problem that the characteristics of the battery gradually deteriorate. In the solid polymer electrolyte fuel cell, since it is necessary to always include water in the membrane as described above, humidified gas is supplied to the electrode, but it is generated by the supplied water or the electrode reaction. A part of the generated water is condensed inside the anode or the cathode. However, in the conventional cell as described above, the temperatures of the anode and the cathode are almost the same, and it is considered that water is condensed to both electrodes to the same degree. When water condenses inside the electrode, the flow path of the reaction gas supplied from the outside of the cell disappears, and the cell characteristics deteriorate. However, it is said that the cathode has a larger effect than the anode when the gas flow path is blocked with water to the same extent. That is, even if the gas flow path of the anode is blocked to some extent by water, the cell characteristics are not greatly affected, but the cathode is greatly affected.

The present invention has been made in view of the above points, and an object thereof is a solid polymer electrolyte fuel cell in which the cathode temperature of a single cell is set relatively higher than that of the anode and the cathode is not deteriorated in characteristics and is excellent in reliability. To provide.

[0010]

According to the present invention, a first unit cell, a fuel gas supply means, a cooling plate, which are sequentially laminated,
It has an oxidant gas supply means and a second single cell, and the single cell has an anode and a cathode on both main surfaces of a membrane made of a solid polymer electrolyte, and the fuel gas supply means has a fuel gas flow path. Then, the fuel gas is supplied to the anode of the first unit cell, and the oxidant gas supply means has an oxidant gas flow path and supplies the oxidant gas to the cathode of the second unit cell. The cooling plate has a cooling water flow path inside and cools the first and second unit cells via the fuel gas supply means and the oxidant gas supply means. The cooling efficiency is higher than the cooling efficiency of the surface in contact with the oxidant gas supply means, or the first unit cell, the fuel gas supply means, the cooling plate, the oxidant gas supply means, and the second cell that are sequentially stacked. Has a single cell, and the single cell consists of a solid polymer electrolyte An anode and a cathode are arranged on both main surfaces of the membrane, and the fuel gas supply means and the fuel gas flow path are provided to supply the fuel gas to the anode of the first unit cell. The oxidant gas supply means Has an oxidant gas flow path and supplies an oxidant gas to the cathode of the second unit cell, and the thickness of the oxidant gas supply means in the stacking direction is the same as that of the fuel gas supply means. It is larger than the thickness, and the cooling plate has a cooling water flow path inside and cools the first and second unit cells via the fuel gas supply means and the oxidant gas supply means. It is achieved by

[0011]

[Function] Generally, a membrane used in a solid polymer electrolyte fuel cell has a basic structure similar to that of Teflon, and the membrane itself has a considerably poor heat conduction. According to the above structure, the temperature of the cathode becomes higher than that of the anode, and the condensation of water in the cathode is suppressed as compared with the conventional method. That is, the gas flow passage is not clogged due to water condensation in the cathode, and stable cell characteristics can be obtained for a longer period of time.

[0012]

【Example】

(Example 1) FIG. 1 is a cross-sectional view showing a solid polymer electrolyte fuel cell according to an example of the invention defined in claim 1. Here, the unit cell 1 is configured by arranging the cathode 2 and the anode 4 on both sides of the membrane 3. On the other hand, the cooling plate 8 is made of a gas-impermeable sintered carbon plate, and has a distance L ₁ from the end surface facing the anode and a distance L ₂ (L from the end surface facing the cathode in the thickness direction thereof.
_The coolant passage 7 is provided at a position of ₁ + L ₂ = thickness of the cooling plate.

Here, the relationship of L ₁ <L ₂ is established.
In the present example, the material of the cooling plate was a gas-impermeable sintered carbon plate, but if the material is electron-conductive and gas-impermeable, and is chemically stable under the applied conditions. anything is fine. Further, in the present embodiment, the shape of the refrigerant channel is rectangular, but the shape of the channel is not particularly limited. The fuel cell is composed of [single cell (cathode-membrane-anode)] / [anode gas impermeable support plate 6] / [cooling plate] / [cathode gas impermeable support plate 9] / [single cell] However, when stacking a plurality of unit cells, the unit cells are placed through a ribbed gas separator with a flow path (rib) of fuel gas on one side and oxidant gas on the other side as necessary. It is possible to stack and provide a cooling plate for every several cells. (In this embodiment, a cooling plate is provided for every two cells).

FIG. 2 is a different sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 1. The anode gas impermeable support plate 6 was used in place of the anode porous ribbed substrate 12, and the cathode gas impermeable support plate 9 was used in place of the cathode porous ribbed substrate 13. FIG. 7 is a different sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 1. FIG. 8 is a diagram showing the characteristic deterioration rates of the cells of this example and the conventional cell in comparison. The cell numbers correspond in FIG. 7 and FIG. It can be seen that in the case of the conventional cell, the deterioration of the characteristics is large especially in the cell in which the cathode is in contact with the cooling plate, but in the case of the example, it is understood that it is considerably improved. This tendency is the same in the second to fifth embodiments described below.

(Embodiment 2) FIG. 3 is a sectional view showing a solid polymer electrolyte fuel cell according to a different embodiment of the invention defined in claim 1. This example can be applied to the case where the gas-impermeable support plate as in Example 1 is used and the case where the cell using the porous ribbed substrate is used. In this embodiment, the coolant channel 7 is provided at the center of the cooling plate in the thickness direction, but the cooling plate has two kinds of materials having electron conductivity and different thermal conductivity (on the anode side). First cooling member 15
And the second cooling member 16) on the cathode side are bonded together, and the material on the anode side is made of a material having a higher thermal conductivity than the member on the cathode side.

In this embodiment, the first cooling member 15
And copper as the second cooling member 16 were used. (Embodiment 3) FIG. 4 is a sectional view showing a solid polymer electrolyte fuel cell according to still another embodiment of the invention defined in claim 1. In this embodiment, the material is a sintered carbon plate. First and second cooling water flow paths are provided on the anode side and the cathode side of the cooling plate, respectively. The refrigerant is first supplied to the first channel and then turned back to be supplied to the second channel again. In such a supply method, since the average temperature of the refrigerant passing through the first flow path is lower than the average temperature of the refrigerant passing through the second flow path, the amount of heat exchange on the anode side increases, resulting in Moreover, cooling at the cathode is suppressed.

(Embodiment 4) FIG. 5 is a sectional view showing a solid polymer electrolyte fuel cell according to still another embodiment of the invention defined in claim 1. In this embodiment, as in the case of the third embodiment, the cooling plate 8 is provided with the third cooling water passage 7C facing the anode and the fourth cooling water passage 7D facing the cathode. The total cross-sectional area of the passage is larger in the third cooling water passage. Unlike the case of Example 3, the refrigerant is one-pass without folding back. In this embodiment, a large amount of refrigerant is supplied to the third flow passage having a larger cross-sectional area than the pressure loss of the flow passage, and a difference in cooling capacity occurs between the anode side and the cathode side of the cooling plate. The same effect as can be obtained.

(Embodiment 5) FIG. 6 is a sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 2. In this embodiment, the gas impermeable support plate 6 for the anode is the gas impermeable support plate 9 for the cathode.
It is made thinner. In this embodiment, the cooling water flow path is located at the center of the cooling plate, but it goes without saying that it may be provided in the vicinity of the anode gas impermeable support plate.

[0019]

According to the present invention, the first unit cell, the fuel gas supply unit, the cooling plate, the oxidant gas supply unit, and the second unit cell, which are sequentially stacked, are provided, and the unit cell has a solid height. An anode and a cathode are arranged on both main surfaces of a membrane made of a molecular electrolyte, and the fuel gas supply means has a fuel gas flow path and supplies the fuel gas to the anode of the first unit cell. The agent gas supply means has an oxidant gas flow path and supplies the oxidant gas to the cathode of the second unit cell, and the cooling plate has a cooling water flow path inside thereof and the fuel gas supply means and the oxidant gas supply means. The first and second units are cooled through the agent gas supply means, and the cooling efficiency of the surface in contact with the fuel gas supply means is higher than the cooling efficiency of the surface in contact with the oxidant gas supply means. Or the first single cell that is stacked in sequence, the fuel gas supply Means, a cooling plate, an oxidant gas supply means, and a second unit cell, and the unit cell comprises an anode and a cathode on both main surfaces of a membrane made of a solid polymer electrolyte, and the fuel gas supply means is a fuel. Has a gas flow path and supplies fuel gas to the anode of the first single cell,
The oxidant gas supply means has an oxidant gas flow path and supplies the oxidant gas to the cathode of the second single cell,
The thickness of the oxidant gas supply means in the stacking direction is larger than the thickness of the fuel gas supply means in the stacking direction, and the cooling plate has a cooling water flow path inside thereof and the fuel gas supply means and the oxidant gas supply means. The temperature of the cathode becomes higher than that of the anode as a result of cooling the first and second single cells via the, and as a result, condensation of water in the cathode is prevented and the flow path of the oxidant gas is It is possible to obtain a solid polymer electrolyte fuel cell that is secured and has excellent reliability without deterioration of cell characteristics even after long-term operation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 1.

2 is a different sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 1. FIG.

FIG. 3 is a cross-sectional view showing a solid polymer electrolyte fuel cell according to another embodiment of the invention defined in claim 1.

FIG. 4 is a sectional view showing a solid polymer electrolyte fuel cell according to still another embodiment of the invention defined in claim 1.

FIG. 5 is a sectional view showing a solid polymer electrolyte fuel cell according to still another embodiment of the invention defined in claim 1.

FIG. 6 is a sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 2.

FIG. 7 is a different cross-sectional view showing a solid polymer electrolyte fuel cell according to an embodiment of the invention defined in claim 1.

FIG. 8 is a graph showing the characteristic deterioration rates of the cells of this example and the conventional cell in comparison.

FIG. 9 is a sectional view showing a conventional solid polymer electrolyte fuel cell.

FIG. 10 is a sectional view showing a conventional solid polymer electrolyte fuel cell.

[Explanation of symbols]

 1 Single Cell 2 Cathode 3 Membrane 4 Anode 5 Fuel Gas Flow Path 6 Gas Impermeable Support Plate for Anode 7 Cooling Water Flow Path 7A First Cooling Water Flow Path 7B Second Cooling Water Flow Path 7C Third Cooling Water Flow Path 7D Second Four cooling water flow channels 8 Cooling plate 9 Gas impermeable support plate for cathode 10 Oxidant gas flow channel 11 Gas separator with ribs 12 Base material with porous ribs for anode 13 Base material with porous ribs for cathode 14 Gas without ribs Separator 15 First cooling member 16 Second cooling member

Claims (6)

[Claims] 1. A first unit cell, a fuel gas supply unit, a cooling plate, an oxidant gas supply unit, and a second unit cell, which are sequentially stacked, each unit cell comprising a solid polymer electrolyte membrane. An anode and a cathode are arranged on both main surfaces, and the fuel gas supply means has a fuel gas flow path and supplies the fuel gas to the anode of the first unit cell. An oxidant gas is supplied to the cathode of the second single cell by having an agent gas flow path, and the cooling plate has a cooling water flow path inside thereof and has a fuel gas supply means and an oxidant gas supply means. Solid for cooling the first and second single cells via the cooling means, wherein the cooling efficiency of the surface in contact with the fuel gas supply means is higher than the cooling efficiency of the surface in contact with the oxidant gas supply means. Polymer electrolyte fuel cell. 2. The solid polymer electrolyte according to claim 1, wherein the cooling plate is made of a single material, and the cooling water passage is provided close to the fuel gas supply means side. Type fuel cell. 3. The fuel cell according to claim 1, wherein the cooling plate is formed by joining a first cooling member and a second cooling member, and is laminated on the fuel gas supply means via the first cooling member, Here, the solid polymer electrolyte fuel cell is characterized in that the thermal conductivity of the first cooling member is higher than that of the second cooling member. 4. The fuel cell according to claim 1, wherein the cooling plate is made of a single material and is adjacent to the first cooling water flow path and the oxidant gas supply means provided near the fuel gas supply means. And a second cooling water channel provided therein, in which the cooling water flows from the first cooling water channel to the second cooling water channel in the first cooling water channel and the second cooling water channel. A solid polymer electrolyte fuel cell, which is characterized in that it flows as a fluid. 5. The fuel cell according to claim 1, wherein the cooling plate is made of a single material and is adjacent to the first cooling water flow path and the oxidizing gas supplying means which are provided near the fuel gas supplying means. And a second cooling water channel provided therein, in which the cooling water independently flows in the first cooling water channel and the second cooling water channel, and the total cross-sectional area of the first cooling water channel Is larger than the total cross-sectional area of the second cooling water channel. 6. A first unit cell, a fuel gas supply unit, a cooling plate, an oxidant gas supply unit, and a second unit cell, which are sequentially stacked, each unit cell comprising a membrane made of a solid polymer electrolyte. An anode and a cathode are arranged on both main surfaces, the fuel gas supply means has a fuel gas flow path and supplies the fuel gas to the anode of the first unit cell, and the oxidant gas supply means is an oxidizing gas. An oxidant gas is supplied to the cathode of the second unit cell having an agent gas flow path, and the thickness of the oxidant gas supply means in the stacking direction is equal to the thickness of the fuel gas supply means in the stacking direction. In comparison, the cooling plate has a cooling water flow path inside and cools the first and second unit cells via the fuel gas supply means and the oxidant gas supply means. Solid polymer electrolyte fuel cell.