JP3524807B2 - Fuel cell - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly, to a fuel cell including an electrolyte layer, a pair of electrodes sandwiching the electrolyte layer to form a unit cell, and the electrode sandwiching the unit cell and the electrode. The present invention relates to a fuel cell including a pair of flow path forming members that form a flow path.

[0002]

2. Description of the Related Art In a fuel cell, for example, a solid polymer type fuel cell, a pair of electrodes (cathode and anode) facing each other with an electrolyte layer made of a solid polymer membrane interposed therebetween contain a fuel containing hydrogen and oxygen. By supplying the oxidant and the oxidant, respectively, the reactions shown in the following formulas 1 and 2 are performed, and the chemical energy is directly converted into the electric energy.

[0003]

[Chemical 1]

[0004]

[Chemical 2]

In order to carry out this reaction continuously and smoothly, it is necessary to rapidly remove the water generated at the cathode and continuously supply the oxidant to the cathode. Usually, the supply channel of the oxidant to the cathode is formed between the rib formed on the collector electrode on the cathode side and the surface of the cathode,
This supply channel also serves as a discharge path for the generated water. Therefore, prompt discharge of generated water in the oxidant supply channel is required.

In order to carry out the above reaction continuously and smoothly, fuel is continuously supplied to the anode, and at the same time,
It is necessary to smoothly diffuse the hydrogen ions generated at the anode into the electrolyte layer. At this time, hydrogen ions combine with water in the electrolyte layer and move in a hydrated state in the electrolyte layer.Therefore, in order to smoothly diffuse hydrogen ions into the electrolyte layer, water is replenished from the outside to the electrolyte layer. There is a need to. Such replenishment of water to the electrolyte layer is performed by supplying a fuel whose vapor pressure is increased by humidifying it in advance. When such fuel is supplied to the fuel cell that has not reached the temperature during steady operation immediately after the start of operation, or when fuel with supersaturated water vapor is supplied to the fuel cell, the collector electrode on the anode side In some cases, the water vapor may agglomerate on the surface of the fuel supply passage formed by the ribs formed on the anode and the surface of the anode, thus hindering the smooth flow of the fuel. Therefore, it is required to promptly discharge the water condensed in the fuel supply channel.

As a method of replenishing the electrolyte layer with water, there is also a method of directly supplying water to the fuel supply passage simultaneously with the supply of fuel. In this case as well, it is required to promptly discharge the water supplied at the same time as the fuel.

Conventionally, as a fuel cell which meets such a demand, a fuel cell in which a water-repellent film such as a fluororesin is formed on a surface of a fuel or oxidant supply passage formed by a collecting electrode and an electrode has been proposed. (JP-A-59-18097)
No. 8).

Alternatively, a hydrophilic film such as polyacrylamide (PAAM) is formed on the surface where the fuel or oxidant supply channel is formed (JP-A-8-138692).
Alternatively, a method of providing a hydrophilic member such as a wick in the supply channel (Japanese Patent Laid-Open No. 5-41230) has been proposed.

[0010]

However, when the water-repellent film is formed on the surface where the fuel or oxidant supply channel is formed as described above, the width or depth of the supply channel is narrowed, rather There is a problem in that the supply flow path is clogged with water, which obstructs the flow of the fuel or the oxidant, and reduces the power generation efficiency of the fuel cell.

Further, in the method of forming a hydrophilic film on the surface on which the supply channel is formed or providing the hydrophilic member, the collecting electrode forming the supply channel is made of porous carbon, so that the adhesion is weak. , Therefore, when operating the fuel cell for a long time, peeling of the hydrophilic film or hydrophilic member occurs,
There is a problem of reducing the power generation efficiency of the fuel cell.

The present invention solves these problems, and provides a fuel cell which has good discharge efficiency of water in a fuel or oxidant supply channel for a long period of time and has high power generation efficiency and reliability.

[0013]

In order to solve such a problem, the fuel cell of the present invention includes an electrolyte layer, a pair of electrodes sandwiching the electrolyte layer to form a unit cell, and the unit cell sandwiched between the electrodes. And a pair of flow path forming members that form a flow path for supplying fuel and oxidant between the pair of electrodes, and at least one of fuel or oxidant supply paths. to, a plurality of through holes provided et al is,
A dense material having a parent aqueous surface, the flow path forming portion of the dense material
And a drainage material provided on the material side .

[0014]

In the present invention, it has the hydrophilic surface.
The dense material is polyester or rayo on the surface of the base material.
Polyester, rayon, or rayon / polyke
Hydrophilic woven, non-woven fabric or felt mainly composed of lar
It is characterized by being attached .

[0016] Then, a plurality of projections or holes wherein the substrate on the surface, the hydrophilic woven, nonwoven or felt,
It is characterized in that it is mechanically coupled to the protrusions or holes on the surface of the substrate.

Alternatively, the dense material having a hydrophilic surface is characterized in that a hydrophilic film is formed on the surface of the base material.

[0018]

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below.

FIG. 1 is an assembly view of a cell unit CU which constitutes a fuel cell 1 according to this embodiment.

In FIG. 1, reference numeral 11 denotes an electrolyte layer made of a solid polymer film, and the electrolyte layer 11 is sandwiched between a cathode 12 and an anode 13 (shown by a broken line on the back surface of the electrolyte layer in FIG. 1) to form a unit cell 10. The unit cell 10 is configured to be sandwiched between a cathode side channel substrate 40 and an anode side channel substrate 30 which are a pair of flow path forming members. On the surfaces of the cathode-side channel substrate 40 and the anode-side channel substrate 30 facing the cathode 12 and the anode 13, respectively, the cathode-side channels 420 ,
An anode-side channel 300 is formed, and the supply channels for the oxidant and the fuel are formed between the cathode 12 and the anode 13. Then, these laminated bodies are fitted into the frame body 20 to form the cell unit CU.

The fuel cell 1 is constructed by stacking a predetermined number of the cell units CU and sandwiching both ends of the cell units CU with a pair of end plates, and the fuel is supplied to the anode side channel 300 and the cathode side channel 42 0. Is supplied with an oxidizer to generate electricity. As the fuel, hydrogen gas or a reformed gas containing hydrogen as a main component can be used, and as the oxidant, air can be used.

In the present embodiment, the electrolyte layer 11 described above is used.
Is a thin film made of perfluorocarbon sulfonic acid, and an electrode layer having a predetermined thickness made of platinum-supporting carbon is adhered to both surfaces of the electrolyte layer 11 by hot pressing to form a cathode 12 and an anode 13.

When stacking the cell units CU as described above, the conductivity is ensured so that the oxidant flowing in the cathode side channel 420 and the fuel flowing in the anode side channel 300 are not mixed with each other. Therefore, a dense glassy carbon having airtightness is used as the partition plate 50 and is interposed between the cell units CU.

FIG. 2 is a detailed assembly drawing of the main part of FIG. 1, in which fuel flows from the upper right to the lower left.

The frame body 20 is made of a plastic material, and a concave portion 200 into which the unit cell 10 and the cathode side channel substrate 40 are fitted is formed in a substantially central portion of one surface (top surface in FIG. 2) of the plastic material, and the central portion thereof is further formed. The anode 13
A window 200w having substantially the same size as the above is opened. Further, although not shown, a concave portion into which the anode side channel substrate 30 and the partition plate 50 are fitted is formed on the other surface (rear surface in FIG. 2) side.

The anode side channel substrate 30 is a plate made of a porous carbon body in which a large number of anode side channels 300 are formed. Each channel 300 is formed in a gap between ribs 30 1 arranged at a predetermined pitch, and
Regions 300a for producing gas-liquid mixtures of fuel and water, respectively
And a region 300b which is arranged so as to face the anode 13 and through which the generated gas-liquid mixture flows, and a region 300c which guides the remaining gas-liquid mixture subjected to an electrochemical reaction or the like further downstream. Has been done.

Furthermore, the rib 30 1 in the area 300b of the central portion, said fitted into the window 200 w, so that the top is the anode 13 and electrically connectable with and fitted state, from the rib in the region 300a and 300c Is also high.

In the recess 200, the anode 13 has a window 2
The unit cell 10 is placed so as to face 00w with the gasket 62 interposed, and the cathode-side channel substrate 40 is fitted from above with the gasket 61 interposed.

On the upstream side of the frame body 20, two through holes 201 that form a passage for distributing fuel in the cell stacking direction.
Further, a through groove 202 serving as a passage for distributing the fuel to each channel 300a is formed between the two through holes 201. On the downstream side of the through-hole 202, two through-holes 203 serving as passages for distributing water in the cell stacking direction are formed.
One of between the through-hole 203 through groove 204 as a passage for arranging minute <br/> water to each channel 300 a is opened.

The water dispersion substrate 23 is fitted in the through groove 204. The water dispersion substrate 23 is made of metal (stainless steel, Ti steel) or ceramics (Al2O3).
Etc.) or a plastic (polyester, ABS, perphenyl oxide, etc.) thin plate in which the pores 23a are formed at a predetermined pitch.

Further, the through hole 205, the through groove 206, and the through hole 20 are similarly provided on the downstream side of the recess 200 of the frame body 20.
7. A through groove 208 is opened. Of these, through groove 2
Reference numeral 06 denotes a gas permeable substrate 2 which constitutes a gas selective discharge means.
4 is inserted with the buffer space 206a (see FIG. 4) left.

The gas permeable substrate 24 is a water repellent carbon paper, a porous film made of tetrafluoroethylene resin or polyester, polyolefin, polytetrafluoroethylene (Teflon, manufactured by DuPont, PTF).
E), tetrafluoroethylene-plufluoroalkylvinylether copolymer (PFA), glass, tetrafluoroethylene resin porous membrane with polypropylene as a support, or polyester fiber coated with polyurethane is used as a material.

Further, the water absorbing base material 25 is fitted into the through hole 208 except for the water buffer space 208a (see FIG. 4) to form a water absorbing means.

The water-absorbent substrate 25 can be made of woven fabric, non-woven fabric, or felt containing polyester, rayon, polyester / rayon, polyester / acrylic, rayon / polyclar and the like as main components.

The gas permeable substrate 24 and the water absorbing base material 25.
By using the above-mentioned materials, it is possible to realize a stable gas-liquid separation function and water absorption function at low cost.

Furthermore, each channel 30 0 of the anode-side channel substrate 30, dense member 50 0 having a hydrophilic surface
Is provided .

The dense material 500 is a stainless steel plate, N
The base material is a dense plate material such as an i-based steel plate, ceramics, amorphous carbon, or a stainless steel plate or a Ni-based steel plate having carbon adhered to the surface thereof, and the surface thereof is provided with hydrophilicity.

In order to impart hydrophilicity to the surface, hydrophilicity such as woven fabric, non-woven fabric, felt or the like containing polyester, rayon, polyester / rayon, rayon / polyclar as a main component is applied to the surface of the substrate having these denseness. The material may be attached using an acrylic adhesive or a double-sided tape. Alternatively, a hydrophilic film may be formed on the surface of the base material by a chemical treatment such as immersing these base materials in a polyacrylamide (PAAM) solution and then drying.

It is also possible to use the above-mentioned base material having a roughened surface and having minute irregularities having a diameter of about 1 to 10 μm formed on the surface. Such minute unevenness can be formed by roughening the surface of the substrate by electropolishing.

When the diameter is less than 1 μm, bubbles remain in the recesses and water is repelled, resulting in insufficient hydrophilicity. Further, if the diameter is larger than 1 μm, the characteristics of the material are reflected and the material becomes water repellent, so that hydrophilicity cannot be imparted.

Next, FIG. 3 is an assembly view of the cathode side channel substrate 40.

As shown in the figure, in the channel substrate 40 on the cathode side, a channel body 400 made of a carbon porous body in which a channel 401 for distributing and supplying an oxidant to the cathode is formed is fitted into a frame member 410. It has a different structure.

The frame member 410 includes a channel 411a for introducing an oxidizing agent into the channel 40 1 from the outside, is a test oxidant into the reaction channel 411 b for discharging the channel 41 1 or et external It is a member made of a plastic material formed on one side surface.

The channel body 4 is attached to the frame member 410.
00 is fitted, the channel 411a, 40 0及 beauty 41
1b communicates with each other to form an anode-side channel 420.

FIG. 4 is a sectional view showing the structure of the fuel cell stack.

[0047] As described above, the fuel is distributed through the through hole 201 in each cell unit CU, and is distributed to each anode-side channel 30 0 in the region 300a through the through groove 202 communicating with the through hole 201.

Further, water is distributed to each cell unit CU through the through hole 203 formed on the downstream side of the through hole 201, and the water dispersion substrate 23 fitted in the through groove 204 communicating with the through hole 203 is provided. It is distributed to each anode-side channel 30 0 through. The water distributed through the water dispersion substrate 23 and the fuel distributed from the through groove 202 and the region 300a.
In the region 300b as a gas-liquid mixed gas.
It is supplied to each channel 30 0 in.

The exhaust gas, which has been supplied to the electrochemical reaction in the region 300b, is exhausted to the outside from the through groove 206 and the through hole 205 communicating with the through groove 206 via the gas permeable substrate 24. Further, the discharged water is absorbed by the water absorbing base material 25, and is drained to the outside through the through groove 208 and the through hole 207 communicating with the through groove.

[0050] Here, the anode-side channel 30 0 become the feature of the present invention, the dense material 500 having a hydrophilic surface
Is provided. The dense material 500 is formed between the through grooves 202 and 204 and the through groove 206 as shown in FIG.
And 208 between the frame body 20 and the anode side channel substrate 30 by the protruding portions 550, 550 provided on the back surface of the frame body 20. This protruding portion 550
Wide, since the preventing flow of <br/> Ru fuel stream on the anode side channel 30 0 too large, it is preferable that about a half or less of the width of the channel width.

[0051] By a dense material 500 having a hydrophilic surface according to the present invention is provided, the anode-side channel 30 0
Moisture in the gas-liquid mixture flowing in becomes to flow along the hydrophilic surface of the dense material 500, not to inhibit the flow of fuel.

Further, the dense material 5 having such a hydrophilic surface
00 is a dense base material such as a stainless steel plate or a Ni-based steel plate as described above, and a hydrophilic material such as woven fabric, non-woven fabric, or felt whose main component is polyester, rayon or the like is acrylic adhesive or double-sided. It is manufactured by means of sticking with a tape or forming a hydrophilic film on the surface of the above-mentioned substrate by chemical treatment or the like. Since such a dense base material is used, the adhesive force between the base material and the hydrophilic material or the hydrophilic film is stronger than before, and the hydrophilic material can be used even when operating for a long time. Hardly peels off the film. Therefore, according to the present invention, good drainage of water in the fuel or oxidant supply channel,
A fuel cell having high power generation efficiency and high reliability can be provided.

Further, a plurality of protrusions or holes are provided on the surface of the base material, and the protrusions or holes are made of a hydrophilic material such as polyester, rayon or the like as a main component, a non-woven fabric or a felt. If they are mechanically fixed by binding, it becomes possible to further increase the adhesive force with the base material. (Example) Based on the first embodiment, a fuel cell having the following specifications was produced as an example.

Effective electrode area: 100 cm ² Solid polymer membrane: Perfluorocarbon sulfonic acid membrane Anode: Pt-Ru-supporting carbon cathode: Pt-supporting carbon cell Number of laminated layers: 52 Also, as a conventional example, a dense material having a hydrophilic surface 500
A fuel cell having the same structure as that of the example was manufactured except that the fuel cell was not provided.

The average cell voltage (V) when the above-described examples and the conventional fuel cell were operated under the following conditions was measured and their performances were compared. The result is shown in FIG.

Fuel: H ₂ / N ₂ = 36/64 Oxidant: Air Current density: 0.5 A / cm ² Cooling water amount: 30 cc / min Fuel utilization rate: 40 to 95% where the fuel utilization rate is The fuel supply rate is controlled by changing the fuel supply rate. As the fuel supply rate increases, the fuel utilization rate decreases, and as the fuel supply rate decreases, the fuel utilization rate increases.

It is apparent from FIG. 5 that the fuel cell of the embodiment can obtain a higher average cell voltage than the conventional fuel cell, and the average cell voltage does not decrease much even if the fuel utilization rate is increased. On the other hand, in the conventional fuel cell, the average cell voltage is low as a whole, and the fuel utilization rate is greatly reduced in a large region. This is because the conventional fuel cell does not include a dense material having a hydrophilic surface, so that water in the gas-liquid mixed gas causes water clogging, which impedes the fuel flow and increases the fuel utilization rate. It is thought that this is due to the fact that the influence of water clogging became significant due to the small amount of fuel supply. (Second Embodiment) Next, a second embodiment of the present invention will be described.

FIG. 6 is an enlarged cross-sectional view of the main part of the fuel cell according to this embodiment. As shown in the figure, in the present embodiment, the dense material 500 arranged in the anode side channel 300.
As a result , a dense material 500 having a plurality of through holes 510 is arranged, and a drainage material 520 is further provided on the back surface thereof. As the material of the drainage material 520, for example, nylon felt (nylon 6) can be used.

According to this structure, the water in the gas-liquid mixed gas containing the fuel supplied to the anode side channel 300 is
A plurality of through holes 51 travel through the hydrophilic surface of the dense material 500 0
Since it is guided to the back side through the drainage material and flows through the drainage material provided on the back side, more water can be flowed as compared with the fuel cell of the first embodiment described above. Therefore, the cooling effect of the fuel cell can be enhanced, and the output of the fuel cell can be enhanced more than ever before. (Example 2) Based on the second embodiment, a fuel cell having the following specifications was produced as an example.

Effective electrode area: 100 cm ² Solid polymer membrane: Perfluorocarbon sulfonic acid membrane Anode: Pt-Ru supported carbon cathode: Pt supported carbon cell Number of laminated layers: 52 Further, as a conventional example, a dense material having a hydrophilic surface 500
A fuel cell having the same structure as that of the example except that the drainage material 520 was not provided was prepared.

The average cell voltage (V) when the fuel cells according to Examples 1 and 2 and the conventional fuel cell were operated under the following conditions was measured and their performances were compared. The result is shown in FIG. 7.

Fuel: H ₂ / N ₂ = 36/64 Oxidizer: Air Fuel utilization rate: 80% Current density: 0.4 to 0.8 A / cm ^{2 The} amount of cooling water is increased as the current density is increased. In this way, the operating temperature of the fuel cell is adjusted to be in the optimum range.

As is apparent from FIG. 7, the fuel cell of Example 2 can obtain the highest average cell voltage. Moreover,
In the fuel cell of the second embodiment, a larger amount of water can be flowed as compared with the fuel cells of the related art and the first embodiment, so that when the current density is increased, the decrease in the average cell voltage caused by the temperature rise of the fuel cell is reduced. It can be made smaller, and it becomes possible to operate at a higher current density.

In the above embodiments, the fuel cell using the gas-liquid mixed gas in which water is mixed with the fuel has been described, but the present invention is not limited to this, and the present invention is also applied to a fuel cell using a humidified fuel. be able to. Further, the dense material having a hydrophilic surface is not limited to the above-mentioned anode side channel, but may be provided in the cathode side channel, and may be provided in at least one of the anode side channel and the cathode side channel. By providing in the channel on the cathode side, it becomes possible to quickly discharge the generated water generated on the cathode side, and it is possible to prevent the supply of the oxidant from being hindered by water clogging.

Further, it goes without saying that the present invention is applicable not only to a fuel cell using a solid polymer membrane as an electrolyte layer, but also to a fuel cell using another electrolyte layer.

[0066]

As described above, according to the present invention, since the dense material having the hydrophilic surface is provided in at least one of the fuel or oxidant supply paths, the fuel is supplied to the anode side channel. Moisture in the fuel or water produced in the cathode side channel flows along the hydrophilic surface of the dense material, and the flow of fuel and oxidant is not obstructed.

As the dense material having a hydrophilic surface, since a dense base material such as a stainless steel plate or a Ni-based steel plate is used as described above, the adhesion of the base material to the hydrophilic material or the hydrophilic film is preferable. The adhesion is stronger than before, and the hydrophilic material and film are less likely to peel off even after running for a long time.

Therefore, according to the present invention, it is possible to provide a fuel cell which maintains good drainage of water in the fuel and oxidant supply passages and has high power generation efficiency and reliability.

[Brief description of drawings]

FIG. 1 is an exploded view of a fuel cell according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the fuel cell according to the first embodiment.

FIG. 3 is an exploded view of the cathode-side channel substrate.

FIG. 4 is a cross-sectional view showing a structure of a fuel cell stack.

FIG. 5 is a characteristic diagram showing a relationship between a fuel utilization rate and an average cell voltage.

FIG. 6 is a cross-sectional view showing the configuration of a fuel cell stack according to a second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a relationship between current density and average cell voltage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 10 ... Unit cell, 30 ... Anode side channel substrate, 40 ... Cathode side channel substrate, 300 ... Anode side channel, 420 ... Cathode side channel, 50
0 ... Dense material

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Miyake 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5 Keihan-hondori, Moriguchi-shi, Osaka No. 5 within Sanyo Electric Co., Ltd. (56) Reference JP-A-8-138692 (JP, A) JP-A-6-267555 (JP, A) JP-A-6-79832 (JP, A) JP-A-10- 34760 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 8/02 H01M 8/10

Claims (4)

(57) [Claims] 1. An electrolyte layer, a pair of electrodes sandwiching the electrolyte layer to form a unit cell, and a fuel and oxidant supply channel between the pair of electrodes sandwiching the unit cell. a pair of flow path forming member for forming, a fuel cell including the fuel or to at least one of the supply path of the oxidizing agent, a plurality of through holes provided et al is a dense material having a parent aqueous surface
And a drainage material provided on the flow path forming member side of the dense material . 2. The dense material having a hydrophilic surface is the base material.
Polyester, rayon, polyester / ray on the surface of the material
Mainly made of rayon or rayon / polyclar
Made of hydrophilic woven fabric, non-woven fabric or felt
The fuel cell according to claim 1, wherein: 3. The substrate has a plurality of protrusions or holes on the surface.
However, the hydrophilic woven fabric, nonwoven fabric or felt is
The fuel cell according to claim 2 , wherein the fuel cell is mechanically coupled to a protrusion or a hole on the surface of the material . 4. The dense material having a hydrophilic surface is the base material.
The fuel cell according to claim 1, characterized in that the surface of the wood comprising hydrophilic film is formed.