JP3355861B2 - Fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a stacked fuel cell using pure hydrogen or reformed hydrogen from methanol and fossil fuel as a reducing agent, and using air or oxygen as an oxidizing agent.
In particular, the present invention relates to a structure for uniformly supplying a reaction gas to each unit cell of a solid polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art A unit cell of a polymer electrolyte fuel cell is shown in FIG.
Shown in As shown in FIG. 3, the solid polymer electrolyte membrane 13
It is known that when a cation exchange membrane as a proton conductor is used and hydrogen is introduced as a fuel gas and oxygen is introduced as an oxidant, the following reaction occurs.

[0003]

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[0004]

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In the negative electrode 11, hydrogen dissociates into protons and electrons. The protons move in the cation exchange membrane 13 toward the positive electrode 12, and the electrons move in a cell stacked in series with the conductive separator plate 2 and further in an external circuit to form the positive electrode 12.
Leads to. At this time, power generation is performed. On the other hand, in the positive electrode 12, the protons moving in the cation exchange membrane 13, the electrons moving in the external circuit, and oxygen introduced from the outside react to generate water. Since this reaction is exothermic, it generates electricity, water and heat from hydrogen and oxygen as a whole.

The polymer electrolyte fuel cell differs greatly from the other fuel cells in that the electrolyte 13 is constituted by an ion exchange membrane which is a solid polymer. For this ion exchange membrane, a perfluorocarbon sulfonic acid membrane or the like is used.

As shown in FIG. 2, a plurality of unit cells 1 are solidly stacked via a bipolar separator plate 2 and a gasket 3 in which manifolds 7 and 8 and a frame of the unit cells are integrated. And a set of end plates 4 is sandwiched using bolts or the like (not shown) to form a stacked fuel cell.

Conventionally, a flow path structure of a reaction gas in a stacked fuel cell has been provided with a manifold outside the stack as disclosed in, for example, Japanese Patent Application Laid-Open No. 54-22537.
In this structure, since the cell stack and the manifold are separated, the shape of the manifold must be changed each time the number of layers is changed. In addition, there is a problem that the sealing property at the boundary between the stack and the manifold portion is lost due to the expansion and contraction of the stack due to aging, and the sealing structure becomes complicated.

Therefore, for example, JP-A-3-205763 and JP-A-4-267062 adopt a structure in which a reactive gas is supplied to each unit cell through a gas supply groove from a porous manifold. However, in the above structure in which gas is supplied through a complicated groove from a hole-shaped manifold, the contact area between the supply gas and the flow path is large, and the flow path is meandering in a complicated manner. It was necessary to pressurize and supply the reaction gas more than the pressure loss, actually several atmospheric pressures.

Therefore, as a structure capable of supplying a reaction gas at a normal pressure with a smaller pressure loss, for example, as shown in FIG. It is conceivable to reduce the flow path to a minimum so that the pressure loss is reduced. However, in this structure, for example, if the gas supply holes 9 to the manifold are provided as shown in the figure, the flow in the manifold becomes non-uniform, and as a result, the gas supply amount to each cell is different and the characteristics are different. It becomes uneven. As one method for reducing the non-uniformity in the gas flow in the manifold, Japanese Patent Laid-Open No. Hei 5-182684 discloses a structure in which a buffer space is provided in a gas introduction path to an end plate manifold. .

[0011]

However, in the above-mentioned conventional method, sufficient uniformity of the supply gas in the manifold cannot be obtained.

The present invention solves the above-mentioned conventional problems. By increasing the uniformity of gas flow in a manifold of a stacked battery, a reaction gas is uniformly supplied to each unit cell. It is an object of the present invention to provide a high-performance fuel cell with less variation in characteristics, particularly a solid polymer electrolyte fuel cell.

[0013]

According to the fuel cell of the present invention, a unit cell comprising a positive electrode, an electrolyte and a negative electrode is laminated with a separator plate interposed therebetween, and a cell stack is sandwiched between a pair of end plates and the separator is provided. In a fuel cell having an inlet-side manifold for supplying a reaction gas and an outlet-side manifold for discharging a reaction gas on a plate and an end plate, a box-shaped gas diffusion space is provided at a gas inlet of the inlet-side manifold. And a gas rectifying plate composed of a flat plate having a portion and a large number of openings .

[0014]

In this configuration, the reaction gas is introduced into the gas diffusion space, diffused and homogenized, and then supplied to the entrance side manifold through the gas flow plate. For this reason, the flow of the gas in the inlet-side manifold is maintained in a very uniform state, and the variation in the characteristics of each unit cell can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) As shown in FIG. 1, an opening of an inlet side manifold 7 is provided in an end plate 4, a punching metal plate is attached to the opening as a gas rectifying plate 6, and a box-shaped gas diffusion plate is provided. Space part 5 was installed.
No. for punching metal plate. 2, No. The experiment was performed on two types of No.4. Punched metal plate No. The diameter, pitch, thickness, and aperture ratio of the hole 2 are 2 mm and 4, respectively.
4 mm, 0.08 mm, and 57%. The diameter, pitch, thickness, and aperture ratio of the hole No. 4 were 1 mm, 1.5 mm, 0.05 mm, and 42%, respectively. The cross-sectional area in the plane direction of the box-shaped gas diffusion space is 5.
It was 5 cm ² and the height was 20 mm. Punched metal plate No. 4 and 5 show the case where punched metal plate No. 2 was used. FIGS. 6 and 7 show the case where No. 4 is used.

Here, a unit cell in which positive and negative electrodes comprising a catalyst layer and a diffusion layer were laminated via an ion exchange membrane as an electrolyte and a solid polymer electrolyte membrane Nafion 117 manufactured by DuPont was used.

In each figure, in order to evaluate the state of gas flow in the manifold, the outer wall surfaces of the inlet side manifold 7 and the outlet side manifold 8 are cut, a transparent plate is attached, and white smoke is mixed with the supplied gas. The flow of gas was visualized to observe and photograph the flow of gas in the inlet side manifold and the flow of gas in the outlet side manifold. Here, the direction of the gas flow is indicated by an arrow, and the portion where the flow is stagnant is indicated by a cross.

(Embodiment 2) In order to examine the influence of the shape in the gas diffusion space provided in the gas introduction portion of the inlet side manifold, a sloping wall 14 is formed in the gas diffusion space.
Was provided. There are two types of sizes of the inclined walls, and they are respectively gas diffusion spaces A 'and A ". These are shown in FIGS. 8, 9, 10 and 11, respectively.

(Embodiment 3) Punching metal plates No. 2 and No. 4 were arranged in the gas diffusion space A ", respectively, and shown in FIGS. 12, 13, 14 and 15.

Comparative Example A battery having a gas inlet and a gas outlet as shown in FIGS. 16 to 27 was prepared. Each figure shows the flow of gas in the manifold observed by the method shown in (Example 1) using each battery.

As shown in FIGS. 16 and 17, when gas supply holes were used at the entrance and the exit, a strong gas flow was observed from the top to the bottom in the center of the manifold at the entrance side manifold. In the outlet-side manifold, the flow velocity of the flow from the top to the bottom of the central portion was increased. The above results are obtained when a gas supply hole is attached to the inlet side and a gas diffusion space is attached to the outlet side manifold.
8 and FIG.

As shown in FIGS. 20 and 21, when a gas diffusion space is provided on the entrance side and a gas exhaust hole is provided on the exit side, both the flow of the entrance side manifold and the flow of the exit side manifold are reduced. 16 and 17, the flow became uniform, but it was still insufficient.

Further, in the case where the gas diffusion space portions were installed on the entrance side and the exit side, respectively, the flow became uniform as shown in FIGS. Also, a large vortex was observed in the inlet side manifold, and a uniform flow could not be realized.

On the other hand, as shown in FIGS. 4 to 7, by combining the gas diffusion space and the gas rectifying plate,
Both the flow of the inlet side manifold and the flow of the outlet side manifold could be made uniform. Rectifier plate No.
4, a more uniform flow could be realized. Also in the case of using No. 2, a better flow than the comparative example could be realized.

Although the gas rectifying plate was not used in the second embodiment, the shape of the gas diffusion space was changed as shown in FIGS.
As a result, a good gas flow could be realized.

However, when the gas flow regulating plate was disposed in the gas diffusion space, the effect of improving the gas flow was small as shown in FIGS.

[0028]

In this embodiment, the effect is shown by focusing on the flow of one of the oxidizing gas and the reducing gas. However, the present invention can be used as a configuration of the flow of both of the above gases. The configuration according to the present invention is more effective, and a high-performance fuel cell can be obtained.

In this embodiment, the structure of the polymer electrolyte fuel cell has been described as an example of the fuel cell.
The present invention is also effective for fuel cells using other electrolytes, for example, direct methanol fuel cells, phosphoric acid fuel cells, molten carbon dioxide fuel cells, and solid oxide fuel cells.

[0031]

As described above, the present invention relates to a fuel cell having an inlet manifold 7 for supplying a reaction gas to each unit cell and an outlet manifold 8 for discharging a reaction gas from each unit cell. By providing a gas diffusion space and a gas rectifying plate at the gas introduction portion of the inlet side manifold, the supplied reaction gas is equalized in the gas diffusion space 5 and rectified by the rectifying plate 6 to be manifold. The flow of gas in 7 can be made uniform.

As a result, uniform supply of the reaction gas to each unit cell can be realized, so that variations in the discharge performance of each unit cell can be reduced, the discharge performance of the entire stacked battery increases, and fuel and The utilization rate of air is improved, and as a result, the size and weight of the gas supply auxiliary device can be reduced, and a highly economical fuel cell can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a stacked fuel cell according to the present invention.

FIG. 2 is a perspective view of a stacked fuel cell of a comparative example.

FIG. 3 is a sectional view of a unit cell.

FIG. 4 is a view visualizing a gas flow in an inlet-side manifold according to the first embodiment of the present invention.

FIG. 5 is a view visualizing a gas flow in the outlet side manifold.

FIG. 6 is a view visualizing a gas flow in an inlet-side manifold according to another embodiment (first embodiment) of the present invention.

FIG. 7 is a view visualizing a gas flow in the outlet side manifold.

FIG. 8 is a view visualizing a gas flow in an inlet-side manifold according to the second embodiment of the present invention.

FIG. 9 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 10 is a view visualizing a gas flow in an inlet-side manifold according to another (second embodiment) of the present invention.

FIG. 11 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 12 is a view visualizing a gas flow in an inlet-side manifold according to the third embodiment of the present invention.

FIG. 13 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 14 is a view visualizing the flow of gas in an inlet-side manifold according to another (third embodiment) of the present invention.

FIG. 15 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 16 is a diagram visualizing the gas flow in the inlet side manifold of (Comparative Example).

FIG. 17 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 18 is a view visualizing a gas flow in an inlet-side manifold of (Comparative Example).

FIG. 19 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 20 is a view visualizing a gas flow in an inlet-side manifold of (Comparative Example).

FIG. 21 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 22 is a view visualizing a gas flow in an inlet side manifold of (Comparative Example).

FIG. 23 is a diagram visualizing a gas flow in the outlet side manifold.

FIG. 24 is a view visualizing a gas flow in an inlet-side manifold of (Comparative Example).

FIG. 25 is a view visualizing a gas flow in the outlet side manifold.

FIG. 26 is a view visualizing a gas flow in an inlet side manifold of (Comparative Example).

FIG. 27 is a diagram visualizing a gas flow in the outlet side manifold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unit cell 2 Separator plate 3 Gasket 4 End plate 5 Gas diffusion space 6 Rectifier plate 7 Inlet manifold 8 Outlet manifold 9 Gas supply hole 10 Cell stack 11 Negative electrode 12 Positive electrode 13 Ion exchange membrane 14 Slant wall

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-246569 (JP, A) JP-A-4-308665 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/24 H01M 8/10

Claims (4)

(57) [Claims] 1. A unit cell comprising a positive electrode, an electrolyte and a negative electrode,
A fuel having a cell stack formed by laminating through a separator plate sandwiched between a pair of end plates, and having an inlet-side manifold for supplying a reaction gas to the separator plate and the end plate and an outlet-side manifold for discharging the reaction gas. The battery has a box-shaped gas diffusion space and a large number of holes at the gas inlet of the inlet side manifold.
A fuel cell provided with a gas rectifying plate composed of a flat plate . 2. A unit cell comprising a positive electrode, an electrolyte and a negative electrode,
A cell stack formed by laminating via a separator plate was sandwiched by a set of end plates, and the separator plate and the end plate were provided with an inlet-side manifold for supplying a reaction gas and an outlet-side manifold for discharging the reaction gas. in the fuel cell, the gas inlet to diffuse the introduced gas on the inlet side gas inlet portion of the manifold to provide a gas diffusion space of the box-type the gas diffusion space portion
A fuel cell with a sloping wall that changes the direction of the gas introduced from the fuel cell. 3. The fuel cell according to claim 1, wherein the direction of gas introduction into the gas diffusion space and the direction of gas introduction into the inlet-side manifold are different from each other . 4. A fuel cell according to any of the electrolyte according to claim 1 or 2 in which the ion-exchange membrane made of solid polymer.