WO2011024224A1

WO2011024224A1 - Fuel cell

Info

Publication number: WO2011024224A1
Application number: PCT/JP2009/004160
Authority: WO
Inventors: 佐藤裕輔; 小野昭彦; 八木亮介; 坂上英一; 富松師浩
Original assignee: 株式会社東芝
Priority date: 2009-08-27
Filing date: 2009-08-27
Publication date: 2011-03-03

Abstract

Provided is a fuel cell characterized in that an anode, an electrolyte membrane, a cathode, a first constricting member with a first opening, a cathode flow field with a second opening, and a cathode flow field plate that covers the aforementioned cathode flow field are positioned in this order.

Description

Fuel cell

The present invention relates to a fuel cell.

In the case of a direct methanol supply fuel cell (DMFC) in which air supply is performed by diffusion, a moisturizing layer and a cover member are formed on the surface of the cathode on which the oxidant is supplied in order to develop a moisture content and humidity adjustment function. There has been proposed a method of expressing a moisture content and humidity adjusting function by providing layers having different moisture retention functions (Patent Document 1).

However, also in Patent Document 1, water generated at the cathode electrode is easily moved into the atmosphere by diffusion, and the electrolyte membrane and the cathode electrode are dried. For this reason, in addition to the water required for the anode reaction, there remains a problem that it is necessary to supply extra water that permeates the electrolyte membrane from the anode side to the cathode side.

JP 2007-80776 A

In a fuel cell in which air is supplied by diffusion, the present invention maintains the relative humidity of water in the cathode electrode, thereby maintaining the moisture of the electrolyte membrane and the water that permeates the electrolyte membrane from the anode side to the cathode side. An object of the present invention is to provide a fuel cell capable of reducing the above.

The fuel cell according to the present invention includes an anode electrode, an electrolyte membrane, a cathode electrode, a first throttle member having a first opening, a cathode flow path having a second opening, and the cathode A cathode channel plate covering the channel is arranged in this order.

According to the above aspect, in a fuel cell in which air is supplied by diffusion, by keeping the relative humidity of water in the cathode electrode high, moisture retention of the electrolyte membrane and permeation of the electrolyte membrane from the anode side to the cathode electrode side are achieved. It is possible to provide a fuel cell capable of reducing water.

Sectional drawing of the stack which laminated | stacked the cell which concerns on 1st Embodiment. The principal part schematic diagram on the cathode side which concerns on 1st Embodiment. The figure which showed the relationship between (alpha) value and RH of a cathode flow path. A sectional view of a simulation model. The figure which showed the result of simulation. The figure which showed the modification of the 1st aperture member. The figure which showed the simulation model and the result. The principal part schematic diagram on the cathode side which concerns on the modification of 1st Embodiment. The figure which showed the modification of the 1st aperture member. Sectional drawing of the cell which concerns on 2nd Embodiment. Sectional drawing of the cell which concerns on 3rd Embodiment. Sectional drawing of the cell which concerns on 4th Embodiment. Example results. Results of other examples.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The arrangement is not limited to the following. The technical idea of the present invention can be variously modified within the scope of the claims.

[First Embodiment]
A fuel cell employing DMFC will be described as the fuel cell according to the first embodiment of the present invention.

A fuel cell stack cell 100 in which cells according to the first embodiment of the present invention are stacked includes an anode electrode, an electrolyte membrane, a cathode electrode, a first throttle member having a first opening, A cathode channel having a second opening and a cathode channel plate covering the cathode channel are arranged in this order. That is, as shown in FIG. 1, the cell 100 includes an electrolyte membrane 11, a membrane electrode assembly (MEA) 1 having an anode electrode 18 and a cathode electrode 19 facing each other with the electrolyte membrane 11 interposed therebetween, and a reaction at the anode electrode 18. The gas-liquid separation layer 2 that separates the generated fluid into gas and liquid, the anode flow path plate 4 disposed facing the anode electrode 18, and the cathode flow path plate 41 facing the cathode electrode 19.

The anode flow path plate 4 has a fuel flow path 5 for supplying fuel to the anode electrode 18 and a gas flow path 6 for discharging gas (CO ₂ or the like) generated at the anode pole.

Duct portions

42a and 42b are formed at the edge of the cathode flow path plate 41 of the cell 100 in the extending direction. In addition, the cell 100 includes a cathode channel 44 formed so as to communicate with the

duct portions

42 a and 42 b through the second opening 48 in a direction different from the extending direction of the cathode channel plate 41. The first throttle member 51 is interposed between the cathode flow path plate 41 and the cathode electrode 19. The first aperture member 51 has a first opening 53. In the case of a so-called passive fuel cell that does not have the air supply part 71, the

duct parts

42a and 42b can be omitted.

The anode 18 of the membrane electrode assembly 1 in the first embodiment has an anode catalyst layer 12, a carbon dense layer 14, and an anode gas diffusion layer 16. The cathode electrode 19 includes a cathode catalyst layer 13, a carbon dense layer 15, and a cathode gas diffusion layer 17. Thus, the anode electrode preferably has a catalyst layer and at least one gas diffusion layer. Further, the cathode electrode preferably has a catalyst layer and at least one gas diffusion layer.

As the solid electrolyte membrane 11, for example, a Nafion membrane manufactured by Dupont can be used. The anode catalyst layer 12 is produced, for example, by mixing a Pt—Ru catalyst and an ionomer at a predetermined ratio. The cathode catalyst layer 13 is produced, for example, by mixing a Pt catalyst and an ionomer at a predetermined ratio. As the anode gas diffusion layer 16 and the cathode gas diffusion layer 17, carbon paper, carbon cloth, carbon non-woven fabric, or the like can be used. The gas diffusion layer may be provided with a carbon dense water repellent layer (microporous layer: MPL) mainly composed of carbon powder and PTFE. In addition, the gas diffusion layer is not limited to one layer, and a plurality of gas diffusion layers can be combined to play a role as necessary.

The cells 100 having the cathode flow channel 41 having a flow channel length of 2 L, a flow channel width w, and a flow channel depth h are stacked at regular intervals to form a stack. Adjacent cells have an anode and a cathode electrically connected in series. When the surface of the cathode flow path plate 41 is subjected to a water repellent treatment, electrical connection cannot be obtained simply by laminating. In such a case, it is allowed to connect in series via an electrical contact for establishing electrical connection between the adjacent anode channel plate 4 and cathode channel plate 41.

The anode gasket 9 and the cathode gasket 10 surround the membrane electrode assembly 1 and prevent fuel from leaking from the inside of the cell 100 to the outside.

(Anode configuration and reaction)
A fuel 32, for example, an aqueous methanol solution, is supplied from the fuel tank 31 to the fuel circulation channels L1 and L2 via the valve 33 and the fuel supply unit. A fuel circulation section 35 is inserted in the fuel circulation passage L1, and a pressure adjustment mechanism 36 and a methanol concentration sensor 37 are inserted in L2. The fuel supplied to the fuel circulation passage L1 is supplied by the fuel circulation portion 35 to the fuel supply port 65 of the anode passage plate 4. The fuel is supplied from the fuel supply port 65 to the anode 18 through the fuel supply path 5 and the gas-liquid separation layer 2.

The gas-liquid separation layer 2 is a porous body having lyophobic properties. For this reason, the liquid fuel hardly penetrates into the gas-liquid separation layer 2 which is a porous body. On the other hand, gaseous fuel, that is, methanol vapor and water vapor, permeate into the pores of the porous body and easily pass through the gas-liquid separation layer 2 to reach the anode 18. The fuel that has reached the anode 18 is subjected to an anode reaction by the catalyst of the catalyst layer 12.

Protons (H ⁺ ) generated by the anode reaction pass through the electrolyte membrane 11 having proton conductivity and move to the cathode electrode 19. Electrons (e ⁻ ) generated by the anode reaction move to the cathode electrode 19 via the anode channel plate 4 also serving as a current collector, an external circuit (not shown), and the cathode channel plate 41.

Most of unreacted methanol and water at the anode 18 are discharged from the fuel discharge port 66 of the anode flow path plate 4. A small amount of unreacted methanol and water passes through the electrolyte membrane 11 and moves to the cathode side. A part of the water generated by the cathode reaction is reversely diffused to the anode catalyst layer 12 side through the electrolyte membrane 11, and the rest is discharged to the outside from the

duct portions

42a and 42b via the cathode channel 41 and the second opening 48. Is done.

The fuel discharged from the fuel discharge port 66 reaches the fuel circulation part 35 again through the pressure adjusting mechanism 36 and the methanol concentration sensor 37 inserted in the circulation flow path L2. The methanol concentration sensor 37 monitors the concentration of methanol in the fuel in the fuel circulation passage L2, and feeds back the result to the control unit 80. The controller 80 supplies new high-concentration fuel from the fuel tank 31 to the fuel circulation passage L1 when the concentration is lower than a predetermined concentration, for example, 1M or lower, so that the fuel reaches the predetermined concentration. A command is issued to the supply unit 34.

The gas flow path 6 discharges the gas (CO ₂ gas) generated by the anode reaction from the gas discharge port 66 of the anode flow path plate 4. A fuel circulation section 35 such as a circulation pump and a pressure adjustment mechanism 36 such as a back pressure valve bring the pressure inside the fuel flow path 5 to a higher pressure than the pressure inside the gas flow path 6. Thereby, the gas (CO ₂ gas) generated by the anode reaction is easily discharged to the gas flow path 6 through the pores of the gas-liquid separation layer 2 subjected to the lyophobic treatment. In order to discharge the gas (CO ₂ gas) generated by the anodic reaction as bubbles to the fuel flow path 5, a pressure for generating bubbles is required, but the gas-liquid separation layer is a lyophobic porous body. 2, a path through which the gas flows is formed, and the pressure for allowing the gas to pass through the porous body is smaller than the pressure for generating bubbles in the fuel flow path 5. For this reason, the gas-liquid separation layer 2 can efficiently separate and discharge the gas (CO ₂ gas) generated by the anode reaction to the gas flow path 6. In addition, since the pressure adjustment mechanism 36 adjusts the gas flow path 6 to a predetermined pressure range, the gas-liquid separation of the cell 100 is less affected by the surrounding pressure fluctuation. For example, gas-liquid separation of the cell 100 functions effectively even at a high place such as a mountain peak.

(Cathode configuration and reaction)
This embodiment will be described in more detail with reference to FIG. FIG. 2 is a conceptual diagram of the cathode channel plate 41 when viewed in the y direction of the xyz coordinate shown in FIG. 1 in the cross section taken along the line AA of FIG.

Duct portions

42a and 42b formed in the extending direction of the cathode channel plate are formed at the edge of the cathode channel plate 41. Further, the cathode channel 44 is formed in a direction different from the extending direction of the cathode channel plate 41 (Z direction in FIG. 2). The cathode channel 44 has a second opening 48. The cathode flow path 44 communicates with at least one of the

duct portions

42a and 42b via the second opening 48.

A first throttle member 51 is interposed between the cathode channel plate 41 and the cathode gas diffusion layer 17. The first aperture member 51 is provided with a first opening 53. The first opening 53 penetrates between the surface facing the cathode flow path plate 41 and the surface facing the cathode gas diffusion layer 17. An oxidant and water are exchanged between the cathode channel 44 and the cathode electrode 19 through the first opening 53. The cathode channel plate 41 can be made of conductive carbon having a conductivity or a metal member such as SUS. In the case of conductivity, the cathode channel plate 41 can also be used as a cathode current collector.

The cell 100 is provided with an air supply unit 71 (71a, 71b) for cooling the cell 100 and supplying air to the cathode electrode 19. The air supply unit 71 (71a, 71b) supplies necessary air to the

duct units

42a, 42b. As the air supply unit 71, an air fan that is quiet, has low power consumption, and low discharge pressure can be used.

(Technical significance)
In the above-described configuration, the outside air containing oxygen as an oxidant is supplied to the cathode electrode 19 through the

duct portions

42a and 42b, the second opening 48, the cathode channel 44, and the first opening. Further, the water in the cathode electrode 19 is discharged to the outside in the reverse order. That is, the cathode electrode 19 is not in direct contact with the external environment, and is always mediated through the cathode channel 44. By adopting such a configuration, the inside of the cathode channel 44 is maintained in a high RH state. Although the cathode 19 is easy to dry and the evaporation of water increases, the provision of the first throttle member 51 reduces the area in which the cathode channel 44 and the cathode 19 circulate directly, thereby reducing the cathode 19 Drying can be reduced. The first throttle member 51 faces the cathode flow channel plate 41, but the cathode flow channel plate 41 is formed so as to cover the cathode flow channel 44. For this reason, when air or water moves with respect to the cathode flow path 44, the cathode flow path plate 41 becomes an obstacle (wall) and can exchange air with the outside only through the second opening 48. It has become. For this reason, the cathode channel 44 becomes a so-called stagnation space. That is, the opportunity for the outside air to directly contact the first throttle member 51 is lost. Further, since the duct portion 42 and the cathode flow channel 41 have different directions of air flow, the supply of air from the duct portion 42 to the cathode flow channel 41 is dominated by the contribution of diffusion. The degree of air stagnation in the channel 44 is further emphasized. For this reason, compared with the configuration in which outside air is in direct contact with the first throttle member as in Patent Document 1, the configuration of the present embodiment can significantly reduce the rate of water loss from the cathode electrode 19.

(simulation)
This will be further described below.

FIG. 3 shows an example of the relative humidity (RH) of the cathode channel and the amount of water that permeates the electrolyte membrane 11. The amount of water f _H2O that permeates the electrolyte membrane 11 is indicated by α normalized by the proton flux f _{H +} that permeates the electrolyte membrane 11.

When the RH of the cathode channel increases, the amount of water that permeates the electrolyte membrane 11 decreases, and when RH is sufficiently large, the water moves from the cathode to the anode. The value of α when water moves from the cathode to the anode is negative. The flow rate of water to be supplied from the fuel tank N _H2O is

It is shown. Here, I is the current value multiplied by the number of cells, and F is the Faraday constant. The smaller α is, the smaller the flow rate N _{H2O of} water to be supplied from the fuel tank, that is, the fuel cell system can be miniaturized.

As shown in FIG. 4, the surface of the cathode gas diffusion layer 17 is covered with a first throttle member 51 that prevents transmission of liquid water and water vapor, and a part of the surface of the cathode gas diffusion layer 17 (first opening portion) is covered. 53) By discharging liquid water and water vapor to the cathode channel 44 only from 53), the mass transfer resistance of the water discharged from the cathode electrode 19 increases. As a result, the amount of water moving from the cathode electrode 19 to the anode electrode 18 increases, and the α value decreases.

5A to 5D show an example of a simulation model and an analysis result when the surface of the cathode gas diffusion layer 17 is covered with the first throttle member 51. FIG.

In particular, as apparent from FIG. 5B, the RH inside the cathode gas diffusion layer 17 immediately below the location covered with the first throttle member 51 is large, and the electrolyte membrane 11 facing this location has a large RH. The α value becomes smaller. On the other hand, the α value at the electrolyte membrane 11 facing directly below the first opening 53 is large.

The cathode electrode 19 radiates heat through the first throttle member 51. Therefore, the temperature of the first throttle member 51 is lower in the cathode electrode 19 than in the cathode catalyst layer 13. As a result, the water present as the vapor in the cathode catalyst layer 13 becomes supersaturated (RH 100%) in the region of the cathode gas diffusion layer 17 in contact with the first throttle member 51. The supersaturated water increases the humidity of the cathode catalyst layer 13 region and fulfills the moisture retention function. On the other hand, the remaining steam can move the steam from the cathode gas diffusion layer 17 toward the cathode channel 44.

Such a first opening can set an opening size and an opening pattern capable of satisfying both a necessary air supply and a decrease in α value according to the output and size of the cell.

Specifically, by arranging the first throttle member 51 as shown in FIGS. 6A to 6C on the surface of the cathode gas diffusion layer 17, the α value is set to 0.5 to −1 //, for example. It became possible to reduce to 6. When the aperture ratio is 30% or less, the effect of reducing the α value becomes remarkable. If the aperture ratio is smaller than 5%, the supply of oxygen is insufficient, and the influence of a decrease in output is increased. An aperture ratio of 5 to 30% is suitable.

Here, the aperture ratio can be obtained by the following equation.

Opening ratio (%) = (S2 / S1) × 100
S1 = area of the region where the first diaphragm member is projected onto the membrane electrode assembly S2 = the sum of the areas of the openings in the region of S1 The projected area is substantially used among the first diaphragm members This is because the portion contributing to power generation is the projected area onto the membrane electrode assembly.

FIGS. 7A to 7C show the RH state of the cathode channel 44. FIG. FIG. 7A shows the RH when no cooling air flows through the

duct portions

42a and 42b. When air is supplied as cooling air to the

duct portions

42a and 42b, the RH of the cathode channel 44 tends to decrease and the α value tends to increase due to the influence of the cooling air as shown in FIG. 7B. Therefore, as shown in FIG. 7C, by arranging the first throttle member 51 between the cathode gas diffusion layer 17 and the cathode flow path 44, the influence of increasing the α value by the cooling air can be reduced. Is possible. Furthermore, by providing the first opening 53 of the first throttle member 51 in a region with high RH (in the vicinity of the center of the cathode channel 44 in FIG. 7C), the α value can be reduced.

Further, in the region where the RH of the cathode channel 44 is close to 100%, the α value is small without providing a cover. Therefore, the first opening is used to reduce flooding (excessive accumulation of water) in the cathode catalyst layer. It is preferable to make the portion 53 large.

When RH reaches 100%, condensation occurs on the surface of the cathode flow path plate 41. Therefore, it is desirable to make the surface of the cathode channel plate 41 hydrophilic so that liquid water can move from the cathode channel plate 41 to the outside of the cell 100 via the duct portion 42.

The first diaphragm member 51 is preferably a conductive material such as metal or carbon from the viewpoint of conductivity or current collection.

As described above, by arranging the throttle member 51 on the surface of the cathode gas diffusion layer 17, the α value can be reduced and the amount of water to be held in the fuel tank can be reduced.

(Second aperture member)
By further adding a second throttle member to the second opening 48, the effect of stagnation of the cathode channel 44 can be increased, and the RH in the cathode channel 44 can be kept higher. As such a second throttle member, as shown in FIG. 1 and FIG. 2, in order to reduce water evaporation and sufficiently supply oxygen, air flows in a part of the cathode channel 44. However, the

membranes

45a and 45b that allow the permeation of oxygen may be arranged. By arranging the diaphragm, it is possible to suppress the flow of air inside the cathode flow path 44 and to supply air by diffusion of oxygen, so that the humidity inside the cathode flow path 44 is appropriately maintained. The merit that it becomes easy arises. A porous resin film can be used as the diaphragm.

Further, instead of the

diaphragms

45a and 45b, the cross-sectional area of the second opening 48 may be reduced to, for example, 30% or less of the cross-sectional area of the cathode channel 44, so that a so-called second throttle member may be used.

When both ends of the cathode channel 44 communicate with both the

duct portions

42a and 42b, a second throttle member may be provided in at least one of the second openings.

(Breathing type (fishbone))
The cathode channel 44 is not limited to the form shown in FIG. For example, as shown in FIG. 8, the cathode flow path plate 41 has lands (41, 41a, 41b) formed in a fishbone shape, and a cathode flow between adjacent lands (41a-41a, 41b-41b). A path 44 is formed.

The cathode channel plate 41 has a structure in which the cathode channel 44 and the land are repeated. The air supplied from the air supply part 71 flows through the duct part 42 and flows from the vicinity of z = ± L toward z = 0 mainly by diffusion. Exhaust generated in the vicinity of z = 0 is carried to a region in the vicinity of z = ± L and is discharged to the outside of the single cell 100 by the air flowing through the duct portion 42. Such a cathode channel has an effect that the cathode electrode is difficult to dry because the supply of air to the cathode channel 44 is mainly controlled by diffusion.

The land of the cathode channel plate 41 also has a function of collecting electricity from the cathode gas diffusion layer 17.

(Change in aperture ratio)
A greater effect can be obtained as the aperture ratio of the first opening 53 increases as the distance from the second opening 48 increases, that is, as the depth of the cathode channel 44 increases. The reason is considered as follows.

That is, in the single cell 100 shown in FIG. 2 or FIG. 8, air flows from the duct portion 42 into the cathode channel 44 in the vicinity of z = ± L of the cathode channel plate 41. At this time, the air in the vicinity of z = ± L has a relatively low humidity. For this reason, since the concentration gradient of water in the cathode catalyst layer 13 and the cathode channel 44 becomes large, the α value increases. On the other hand, in the vicinity of z = 0, the supply amount of air is lower than in the vicinity of z = ± L, so the output is relatively low.

Therefore, as shown in FIG. 6C and FIG. 9, the minimum distance δmin of the adjacent first openings 53 is increased as it advances from the vicinity of z = ± L to the depth of the cathode flow path 44 in the z = 0 direction. The following effects can be obtained by increasing the aperture ratio per unit area of the first opening 53 by shortening. That is, in the vicinity of z = ± L, the aperture ratio is relatively small, and α can be reduced. Conversely, in the vicinity of z = 0, the aperture ratio is relatively large, and a decrease in output due to a decrease in the air supply amount can be suppressed. The minimum distance δmin means the minimum distance to the most adjacent opening.

Here, as shown in FIG. 2, when the cathode channel 44 communicates with the

duct portions

42 a and 42 b at both ends thereof, “as going away” means that “the central portion of the cathode channel 44 is separated from both ends. It means "the more you go near." On the other hand, as shown in FIG. 8, when the cathode flow path plate 41 has a backbone structure and the cathode flow path 44 communicates with only one of the duct portions 42, “as moving away” This means that it is closer to the spine 41c of the road plate 41.

“The opening ratio of the first opening 53 increases as the distance from the second opening 48 increases, that is, the depth of the cathode flow path 44 increases” means that the region S1 having a certain area (for example, 2 cm × 2 cm area) is moved so as to “go away from the second opening 48”, that is, “go to the back of the cathode flow path 44”, and the ratio to the area S 2 of the first opening 53 ( S2 / S1), that is, changing so as to increase the aperture ratio. The change here may change continuously, for example, it may change discontinuously stepwise.

Example I
FIG. 13 shows Example 1-1 in which the first diaphragm member 51 is inserted in which the minimum distance δmin between the openings decreases from the vicinity of z = ± L to the depth of z = 0. Here, in the first aperture member 51, δmin in the vicinity of z = ± L shown in FIG. 9 is set to 0.5 mm, and δmin in the vicinity of z = 0 is set to 0.37 mm.

On the other hand, the case where the first diaphragm member 51 is not used is referred to as Comparative Example 1. In Comparative Example 1, the cathode gas diffusion layer 17 and the cathode porous body 21 are in contact with each other.

Further, Example 1-2 was used in which the first diaphragm member in which δmin in the vicinity of z = ± L and δmin in the vicinity of z = 0 was set to the same 0.5 mm was used.

The temperature of the single cell 100 was controlled by a heater (not shown) so that the temperature of the anode channel plate 4 and the cathode channel plate 41 was 65 ° C. A methanol aqueous solution having a fuel concentration of 1.4 M was supplied to the anode channel 5 at 0.5 mL / min. The air supply unit 71 supplied 1000 mL / min of atmospheric air (air) to both the duct units 42 (z = ± L) by a branch pipe. The fuel cell was operated at a load of 1.2A.

As compared with Comparative Example 1, it was confirmed that Example 1-1 can obtain the same output while reducing α. In addition, compared with Example 1-2, it was confirmed that Example 1-1 obtains the same α while increasing the output. Therefore, by using the first throttle member 51 in which the minimum distance δmin between the first openings 53 is shorter from the vicinity of z = ± L toward z = 0, the α can be reduced and the fuel cell can be reduced. It was confirmed that the improvement of the output can be achieved at the same time.

[Second Embodiment]
A fuel cell employing DMFC will be described as a fuel cell according to a second embodiment of the present invention.

As shown in FIG. 10, the unit cell 100 of the fuel cell stack according to the second embodiment of the present invention has a porous body (cathode porous body) between the first throttle member 51 and the cathode channel 44. The point from which 21 is inserted differs from a 1st embodiment.

The cathode porous body 21 is in contact with the land of the cathode flow path plate 41 on the surface, and is in contact with the first throttle member 51 on the back surface. The cathode porous body 21 has electrical conductivity and air permeability. Here, having electric conductivity is defined under the condition that the electric resistivity is lower than that of air. Moreover, having air permeability is defined by having a communicating porosity. The presence or absence of porosity can be measured by mercury porosimetry.

As the cathode porous body, carbon paper, carbon cloth, carbon nonwoven fabric, porous metal, or the like can be used.

In the second embodiment, as in the first embodiment, the first diaphragm member 51 has a plurality of first openings 53 in a predetermined region. Air taken in from the

cathode channels

41 a and 41 b is supplied to the cathode gas diffusion layer 17 through the first opening 53 via the cathode porous body 21. It is preferable that the first aperture member 51 has a characteristic that the minimum distance δmin between the first openings 53 becomes shorter from z = L, near z = −L in the direction of z = 0. As described above.

(Technical significance)
In reducing the size of the single cell 100, it is preferable that the cathode flow path plate 41 and the first throttle member 51 are thinned while maintaining the strength to withstand the tightening of the single cell 100. Therefore, a thin metal plate such as stainless steel or titanium can be used as the cathode channel plate 41 and the first throttle member 51.

However, when the metal plates are simply brought into contact with each other without joining, there is a high possibility that a gap is formed at the contact interface due to strain. This is because it is difficult to provide a gasket function only by contact between metals.

When the first throttle member 51 having conductivity is in contact with the cathode flow channel plate 41, a gap is generated between the first throttle member 51 and the cathode flow channel plate 41. If there is a gap between the land and the first throttle member 51, when a differential pressure is generated between the adjacent cathode flow paths 44, air flows through this gap due to this differential pressure. As the differential pressure increases, the amount of air flowing through this gap increases.

In this case, the water retained by the first throttle member 51 is taken away from the cathode gas diffusion layer 17 by the air flowing through the gap, and α increases. In addition, α is not limited to a constant value depending on the differential pressure condition, and may vary.

In the second embodiment, the cathode porous body 21 is inserted between the first throttle member 51 and the cathode channel plate 41. When the single cell 100 is tightened, the cathode porous body 21 is deformed by the pressure from the first throttle member 51 and the land of the cathode flow path plate 41, and suppresses the above-described gap from being generated. This has the effect of suppressing the air flow due to the differential pressure between the cathode channels 44. Therefore, even when a differential pressure occurs, the increase or fluctuation of the α value can be suppressed.

When the land and the first aperture member 51 are in direct contact with each other, if the first opening 53 of the first aperture member 51 is provided at a position in contact with the land, there is a gap between the land and the first aperture 53. Is formed. This gap can cause an increase in electrical resistance and deflection during tightening. In order to avoid this, it is necessary to make contact between the land and the region excluding the first opening 53 (the wall portion of the first throttle member).

However, in the second embodiment, the cathode porous body 21 is inserted between the cathode channel plate 41 and the first throttle member 51. Accordingly, it is possible to separately provide a surface where the land contacts the cathode porous body 21 and a surface where the first throttle member 51 contacts the cathode porous body 21.

[Third Embodiment]
A fuel cell employing a DMFC will be described as a fuel cell according to a third embodiment of the present invention.

As shown in FIG. 11, in the cell 100 of the fuel cell stack according to the third embodiment of the present invention, the dense carbon layer 22 is formed on one surface of the cathode porous body 21 (the surface in contact with the cathode channel plate). This is different from the first and second embodiments.

When the dense carbon layer 22 is formed on one surface of the cathode porous body 21, and the dense carbon layer 22 and the land of the cathode flow channel plate 41 are brought into contact with each other, the surface with low air permeability comes into contact with the land. The effect of suppressing the air flow due to the differential pressure between the paths 44 is increased. Further, the strength (rigidity) of the entire cathode porous body 21 can be increased. When the cathode flow path plate 41 is produced by press working, there is a possibility that the land has a curvature at the tip of the convex portion and the area where the land contacts the cathode porous body 21 may be reduced. Therefore, when the single cell 100 is tightened with a predetermined pressure, the land may crush the cathode porous body 21 too much, which may cause plastic deformation. On the other hand, when the surface on which the carbon dense layer 22 is formed is brought into contact with the land, the above-described deformation can be suppressed. In addition, when a carbon dense layer is provided on the entire outer periphery of the cathode porous body 21, the air permeability of the cathode porous body 21 is too low. In this case, the amount of air supplied from the cathode flow path 44 to the cathode gas diffusion layer 17 decreases, and the output decreases, which is not preferable.

The carbon dense layer is a dense porous body mainly composed of carbon particles and PTFE and having a pore diameter smaller than the average pore diameter of the cathode porous body 21, and has a lower air permeability than the cathode porous body 21. Here, the air permeability can be determined by the Gurley test method (JIS P 8177).

Example II
FIG. 14 shows the result of the α value when a differential pressure is provided between the z = + L side channel 41 a and the z = −L side cathode channel 41 b in the single cell 100. Here, an example in which the cathode porous body 21 in which the carbon dense layer was provided only on the surface in contact with the land was used as Example 2. The cathode porous body 21 of Example 2-1 is obtained by providing a carbon dense layer on one side of a carbon cloth subjected to water repellent treatment, and the air permeability in the thickness direction is K = 5 × 10 ⁻¹³ (m ² / s).

Then, Example 2-2 was taken as an example in which the cathode porous body 21 was removed and the cathode channel 44 and the first throttle member 51 were brought into contact with each other.

In addition, an example in which the carbon porous layer 21 is not provided with the same cathode porous body 21 as in Example 2-1 was taken as Example 2-3. The air permeability in the thickness direction of the cathode porous body 21 of Example 2-3 was K = 2 × 10 ⁻¹² (m ² / s).

The temperature of the single cell 100 is controlled by a heater (not shown) so that the temperature of the anode flow path plate 4 and the cathode flow path plate 41 is 65 ° C., and the anode flow path plate 4 has a fuel concentration of 1.4 M. A methanol aqueous solution was supplied at 0.5 mL / min. The air supply unit 71 individually supplied air of 1000 mL / min so that 44a was 1000 mL / min and 44b was 500 mL / min, and a differential pressure was provided between the cathode channels. The load was operated at 1.2A.

Compared to Example 2-2 (no porous body), Example 2-3 can reduce the α value by about 0.03, and Example 2-1 can reduce α by about 0.35. It was. Further, the output can be increased in both Examples 2-1 and 2-3 as compared with Example 2-2 having no porous material.

Here, the result of FIG. 14 shows that α is relatively larger than the result of FIG. 13 under the condition that, in the case of FIG. 13, the differential pressure between the cathode channels is almost zero. In the case of FIG. 14, the air supply amount is intentionally changed between the

ducts

44a and 44b so that a differential pressure is generated between the cathode flow paths. Moreover, since the porous body 21 is not inserted in FIG. 13, it is also related that the structure is different.

[Fourth Embodiment]
A fuel cell employing DMFC will be described as a fuel cell according to a fourth embodiment of the present invention. The cell 100 of the fuel cell stack according to the fourth embodiment of the present invention is provided with the third opening 56 around the cathode gas diffusion layer 17 by reducing the height of the cathode flow path 9. It is a cell that can generate power even at high loads.

The amount of air (oxygen) that can be taken into the cathode catalyst layer 13 depends on the channel height of the cathode channel 44, the air diffusion performance of the cathode porous body 21, and the structure of the first throttle member 51. If the height of the cathode flow path 44 is lowered in order to reduce the size of the single cell 100, the amount of air (oxygen) that can be taken into the cathode catalyst layer 13 decreases, and power generation at a high load cannot be performed.

For this problem, in this embodiment, the cathode electrode gasket 10 is thinner than the total thickness of the cathode catalyst layer 13 and the cathode gas diffusion layer 17. The cathode electrode gasket 10 is in contact with the electrolyte membrane 11. Here, the total thickness of the cathode catalyst layer 13 and the cathode gas diffusion layer 17 is determined from the interface between the electrolyte membrane 11 and the cathode catalyst layer 13 when the membrane electrode assembly 1 is assembled. The thickness up to the interface of the opening member 51 is defined.

In the present embodiment, the side surface of the cathode gas diffusion layer 17 is not completely covered with the cathode electrode gasket 10. It is possible to take in air supplied from the air supply unit 71 from this uncovered region (third opening).

When the aperture ratio in the vicinity of z = 0 of the first throttle member 51 is larger than the aperture ratio in the vicinity of z = ± L, the air flowing through the duct portion 42 of the cathode flow path plate 41 is oxygen in the vicinity of z = ± L. As a result of suppressing the consumption amount, z is sent to near zero. The air is supplied to the cathode catalyst layer 13 through the cathode porous body 21, the first throttle member 51, and the cathode gas diffusion layer 17.

In the present embodiment, in addition to the air supply path, the cathode catalyst layer 13 can be supplied from the third opening 56 through the cathode gas diffusion layer 17.

Therefore, the amount of air supplied to the cathode catalyst layer 13 in the end region of z = ± L can be controlled by adjusting the height of the cathode electrode gasket 10 and the opening of the first throttle member 51 can be controlled. By arbitrarily designing parameters such as rate and opening distance, the amount of air supplied to the central region at z = 0 can be controlled, and each region near z = 0 and each region of z = ± L It is possible to control the air supply.

When the air necessary for the reaction in the cathode catalyst layer 13 is supplied using only the air from the cathode flow path 44 without taking in the air from the third opening 56, the cathode catalyst in the vicinity of z = ± L. Since there is oxygen consumption in the layer 13, when the height of the cathode channel 44 is lowered, the oxygen concentration in the vicinity of z = 0 tends to decrease. In contrast, according to the present embodiment, oxygen is supplied to the cathode catalyst layer 13 in the vicinity of z = ± L from the third opening 56 separately, and as a result, the oxygen concentration in the vicinity of z = 0. Can be suppressed. Therefore, even when the height of the cathode channel 44 is lowered, it is possible to achieve high output.

1 ... Membrane electrode assembly (MEA)
2 ... Gas-liquid separation layer (Lipophobic porous material)
4 ... Anode channel plate (anode current collector)
DESCRIPTION OF SYMBOLS 5 ... Fuel flow path 6 ... Gas flow path 9 ... Anode gasket 10 ... Cathode gasket 11 ... Electrolyte membrane 12 ... Anode catalyst layer 13 ... Cathode catalyst layer 14 ... Dense carbon layer 15 ... Dense carbon layer 16 ... Anode gas diffusion layer 17 ... Cathode gas diffusion layer 18 ... Anode electrode 19 ... Cathode electrode 21 ... Cathode porous body 22 ... Dense carbon layer 31 ... Fuel tank 32 ... Fuel 33 ... Valve 34 ... Fuel supply part (pump)
35 ... Fuel circulation part (pump)
36 ... Pressure adjustment mechanism (back pressure valve)
37 ... Fuel concentration sensor (Methanol concentration sensor)
41, 41a, 42b ...

Cathode channel plate

42, 42a, 42b ...

Duct portion

44, 44a, 44b ...

Cathode channel

45a, 45b ... Diaphragm 48 ... Second opening 51 ... First throttle member 53 ... First 56 ... 3rd opening 65 ... Fuel supply port 66 ... Fuel discharge port 67 ...

Gas discharge port

71, 71a, 71b ... Air supply unit 80 ...

Control unit

100, 100a, 100b ... Cell (stack)

Claims

An anode electrode, an electrolyte membrane, a cathode electrode, a first throttle member having a first opening, a cathode channel having a second opening, and a cathode channel plate covering the cathode channel Are arranged in this order.
Having a duct portion at least at a part of an edge of the cathode flow path plate;
2. The fuel cell according to claim 1, wherein the duct portion and the cathode channel communicate with each other through the second opening.
3. The fuel cell according to claim 2, wherein a porous body is interposed between the first throttle member and the cathode channel.
2. The fuel cell according to claim 1, wherein the opening ratio of the first opening is 5 to 30%.
2. The fuel cell according to claim 1, wherein an opening ratio of the first opening portion increases as the distance from the second opening portion increases.
The cathode electrode has a catalyst layer, and the first throttle member is configured to be thermally connected to the cathode catalyst layer, whereby the temperature of the first throttle member is the temperature of the catalyst layer of the cathode electrode. The fuel cell according to claim 1, wherein the fuel cell is lower.
2. The fuel cell according to claim 1, wherein the first throttle member has conductivity.
2. The fuel cell according to claim 1, wherein the second opening further includes a second throttle member.
4. The fuel cell according to claim 3, wherein the porous body has an air permeability of a surface facing the cathode channel plate smaller than an air permeability of a surface in contact with the throttle member.
10. The fuel cell according to claim 9, wherein the cathode porous body includes a dense carbon layer on a surface facing the cathode channel plate.