WO2012133544A1

WO2012133544A1 - Paste coating device

Info

Publication number: WO2012133544A1
Application number: PCT/JP2012/058172
Authority: WO
Inventors: 高見　洋史
Original assignee: 株式会社Ｅｎｅｏｓセルテック
Priority date: 2011-03-31
Filing date: 2012-03-28
Publication date: 2012-10-04
Also published as: JP2012216359A; JP5612528B2

Abstract

Provided is a paste coating device which coats a gas diffusion base used in a fuel cell with a paste, which comprises a conveyor part conveying the gas diffusion base; a coating roll rotating in a predetermined direction of rotation and coating the gas diffusion base conveyed by the conveyor part with the paste applied to a surface thereof; and a doctor bar disposed at an upstream portion of the rotational direction higher than a position where the gas diffusion base is coated with the paste by the coating roll to control the amount of the paste applied to the surface. The doctor bar includes a removing part which forms a gap between the doctor bar and the surface of the coating roll and removes the excess paste applied to the surface. When viewed from the direction of a central rotation axis of the coating roll, a portion constituting the removing part is disposed only on a virtual line or at an upstream portion of the direction of rotation higher than the virtual line in the case where the point of the removing portion which is the closest to the surface of the coating roll and the central axis of rotation are connected by the virtual line.

Description

Paste applicator

The present invention relates to a paste application device for applying a paste to a gas diffusion base material of a fuel cell.

In recent years, fuel cells that have high energy conversion efficiency and do not generate harmful substances due to power generation reactions have attracted attention. As one of such fuel cells, a polymer electrolyte fuel cell that operates at a low temperature of 100 ° C. or lower is known.

A polymer electrolyte fuel cell has a basic structure in which a polymer electrolyte membrane, which is an electrolyte membrane, is disposed between a fuel electrode and an air electrode. The fuel electrode contains hydrogen and the air electrode contains oxygen. It is a device that supplies the agent gas and generates power by the following electrochemical reaction.

Fuel electrode: H ₂ → 2H ++ 2e ⁻ (1)
Air electrode: 1 / 2O ₂ + 2H ++ 2e ⁻ → H ₂ O (2)
Each of the anode and the cathode has a structure in which a catalyst layer and a gas diffusion layer (GDL) are stacked. The catalyst layers of the electrodes are arranged opposite to each other with the solid polymer film interposed therebetween, thereby constituting a fuel cell. The catalyst layer is a layer formed by binding carbon particles carrying a catalyst with an ion exchange resin. The gas diffusion layer becomes a passage for the oxidant gas and the fuel gas.

In the anode, hydrogen contained in the supplied fuel is decomposed into hydrogen ions and electrons as shown in the above formula (1). Among these, hydrogen ions move inside the solid polymer electrolyte membrane toward the air electrode, and electrons move to the air electrode through an external circuit. On the other hand, in the cathode, oxygen contained in the oxidant gas supplied to the cathode reacts with hydrogen ions and electrons that have moved from the fuel electrode, and water is generated as shown in the above formula (2). In this way, in the external circuit, electrons move from the fuel electrode toward the air electrode, so that electric power is taken out.

For example, Patent Document 1 describes that a gas diffusion layer is provided outside the catalyst layer, and the gas diffusion layer is composed of a gas diffusion base material and MPL (microporous layer).

JP 2010-282940 A

In such a gas diffusion layer, a roll coater, screen printing, a die coater, or the like is employed as a method for applying the MPL paste to the gas diffusion base material. Among such methods, in order to fill the paste into the gas diffusion base material, a roll coater for applying pressure is preferably used. Here, in general, the gas diffusion paste has a high viscosity because it contains an adhesive fluororesin. Therefore, in a conventional roll coater using a doctor bar, unevenness, streaks, lumps, etc. are likely to occur in the paste applied to the surface of the coating roll (see, for example, FIG. 7A). When applied to the gas diffusion substrate in such a state, the quality may be deteriorated due to instability of the application amount or application state, variation in battery performance, and the like.

The present invention has been made in view of these problems, and an object of the present invention is to provide a paste coating apparatus capable of improving the paste coating performance and improving the battery performance of the fuel cell.

In order to solve the above problems, a paste coating apparatus according to one aspect of the present invention is a paste coating apparatus that applies a paste to a gas diffusion base material used in a fuel cell, and includes a transport unit that transports the gas diffusion base material And an application roll that rotates in a predetermined rotation direction and applies the paste applied to the surface to the gas diffusion substrate conveyed by the conveyance unit, and a position where the application roll applies the paste to the gas diffusion substrate, A doctor bar that is arranged on the upstream side in the rotation direction and adjusts the amount of paste applied to the surface, and the doctor bar forms a gap with the surface of the coating roll and is applied to the surface It has a removal part that removes excess paste, and it is removed when the closest point of the removal part to the surface of the coating roll and the rotation center axis line are connected with a virtual line when viewed from the rotation center axis direction of the coating roll. Portion constituting the is provided only on the upstream side in the rotational direction of the virtual line or virtual line.

In the paste coating apparatus according to one aspect of the present invention, the portion constituting the removal unit for removing the paste includes the closest point of the removal unit with respect to the surface of the coating roll and the rotation center axis when viewed from the rotation center axis direction of the coating roll. Are connected only on the virtual line or on the upstream side in the rotation direction from the virtual line. That is, the removal unit has a structure that does not have a portion that protrudes downstream in the rotation direction from the virtual line. The part of the removal part that is the closest point to the surface of the coating roll forms the smallest gap between the surface of the coating roll and adjusts the film thickness after removing the excess paste on the surface of the coating roll. Function as. When there is a portion that protrudes downstream from the portion related to the nearest contact point, the paste whose thickness has been adjusted is pulled by the protruding portion, thereby causing unevenness, streaks, lumps, and the like. On the other hand, in the paste coating apparatus according to one aspect of the present invention, there is no portion protruding downstream from the imaginary line, and therefore the paste after the thickness adjustment generates unevenness, streaks, lumps, etc. In a stable state (smooth state), the gas diffusion base material can be headed. Thus, by stabilizing (smoothing) the state of the paste to be applied, it is possible to stabilize the amount of paste applied. Further, it is possible to stabilize the application state of the paste and the penetration depth into the gas diffusion base material. In addition, by applying the paste in a stable state, the paste penetrates well into the gas diffusion base material without being interrupted, so that a highly continuous microporous layer can be formed in the gas diffusion base material. It becomes possible. It is also possible to reduce the pre-stirring time of the paste. Furthermore, since it becomes possible to form a microporous layer by such good paste application, by using the fuel cell electrode produced by the paste application device, the cell performance of the fuel cell can be stabilized. Can be planned. By the above, the paste application performance can be improved and the battery performance of the fuel cell can be improved.

Further, in the paste coating apparatus according to one aspect of the present invention, the removing unit spreads so as to face the surface of the coating roll, and the folded surface that crosses the removal surface and spreads away from the surface of the coating roll. And an edge portion formed between the removal surface and the folded surface and constituting the closest contact point, and the folded surface rotates on the imaginary line or more than the imaginary line when viewed from the rotation center axis direction of the coating roll. Arranged upstream in the direction. The removal surface facing the surface of the coating roll can remove excess components from the paste applied to the surface of the coating roll. Further, the edge portion formed between the removal surface and the folded surface is a portion constituting the closest contact closest to the surface of the application roll, and adjusts the thickness of the paste at the downstream end of the removal surface, Has the function of smoothing the paste surface. Since the folded surface connected to the edge portion is arranged on the imaginary line or on the upstream side in the rotation direction from the imaginary line, without pulling the paste surface whose thickness is adjusted and finished at the edge portion, A smooth state can be maintained. Thereby, the paste can go to the gas diffusion base material in a stable state (smooth state).

In the paste coating apparatus according to one aspect of the present invention, a plurality of coating rolls and doctor bars are provided in the transport direction of the transport unit. When a plurality of sets of application rolls and doctor bars are used, a sufficient amount of paste can be applied to the gas diffusion substrate even if the thickness of the paste per application roll is reduced. When the film thickness per coating roll is kept small, the variation in paste can be reduced as compared with the case where the film thickness is large. Here, when a plurality of application rolls are used in a state where unevenness, streaks, lumps, etc. are generated in the paste as in the conventional case, the air enters between the first paste and the second paste so that the paste Will be divided and lack of continuity. However, in the paste application device according to one aspect of the present invention, the paste can be applied in a smooth state, so even if a plurality of application rolls are used, the first paste and the second layer are used. Air can be prevented from entering between the paste and high continuity can be maintained.

Further, in the paste coating apparatus according to one aspect of the present invention, the removal portion of the doctor bar disposed on the downstream side in the transport direction is closer to the surface of the coating roll than the removal portion of the doctor bar disposed on the upstream side. There is a large gap between them. As a result, a sufficient amount of paste on the coated surface side of the gas diffusion base material can be secured, and a gas diffusion layer with good performance can be manufactured.

According to the present invention, the paste application performance can be improved and the battery performance of the fuel cell can be improved.

According to the present invention, it is possible to achieve both water discharge and gas diffusibility as a fuel cell and improve voltage characteristics.

1 is a perspective view schematically showing the structure of a fuel cell according to an embodiment. It is sectional drawing on the AA line of FIG. It is a perspective view which shows the structure of the electrode for fuel cells typically, and the figure which shows the mode of the cross section in the predetermined cross-sectional position of the said electrode for fuel cells. It is a schematic block diagram which shows the paste coating device which concerns on embodiment. It is an enlarged view of the removal part of the paste of a doctor bar. It is an enlarged view of the removal part of the paste of the doctor bar which concerns on a modification. It is an enlarged view of the removal part of the paste of the doctor bar which concerns on a comparative example. It is an image which shows the catalyst layer and microporous layer which exist in a cathode. It is the graph which plotted the quantity of the microporous layer on a cross section with respect to the cross-sectional position in the thickness direction about an Example and a comparative example. It is the graph which plotted the presence frequency cumulative value of the microporous layer which exists in the area | region of the catalyst layer side from the said cross-sectional position with respect to a cross-sectional position about an Example and a comparative example. It is a figure which shows the result of having measured the cell voltage and the oxygen gain about the Example and the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(Fuel cell)
FIG. 1 is a perspective view schematically showing the structure of a fuel cell 10 according to an embodiment. FIG. 2 is a cross-sectional view taken along the line AA in FIG. The fuel cell 10 includes a flat membrane electrode assembly 50, and a separator 34 and a separator 36 are provided on both sides of the membrane electrode assembly 50. In this example, only one membrane electrode assembly 50 is shown, but a plurality of membrane electrode assemblies 50 may be stacked via the separator 34 or the separator 36 to constitute a fuel cell stack. The membrane electrode assembly 50 includes a solid polymer electrolyte membrane 20, an anode (fuel cell electrode) 22, and a cathode (fuel cell electrode) 24.

The anode 22 has a laminate composed of a catalyst layer 26 and a gas diffusion layer 28. On the other hand, the cathode 24 has a laminate composed of a catalyst layer 30 and a gas diffusion layer 32. The catalyst layer 26 of the anode 22 and the catalyst layer 30 of the cathode 24 are provided to face each other with the solid polymer electrolyte membrane 20 interposed therebetween.

A gas flow path 38 is provided in the separator 34 provided on the anode 22 side. Fuel gas is distributed to a gas flow path 38 from a fuel supply manifold (not shown), and the fuel gas is supplied to the membrane electrode assembly 50 through the gas flow path 38. Similarly, a gas flow path 40 is provided in the separator 36 provided on the cathode 24 side.

Oxidant gas is distributed to the gas flow path 40 from an oxidant supply manifold (not shown), and the oxidant gas is supplied to the membrane electrode assembly 50 through the gas flow path 40. Specifically, when the fuel cell 10 is operated, a reformed gas containing a fuel gas, for example, hydrogen gas, flows through the gas flow path 38 along the surface of the gas diffusion layer 28 from the upper side to the lower side. The fuel gas is supplied to 22.

On the other hand, during operation of the fuel cell 10, an oxidant gas, for example, air flows through the gas flow path 40 from the upper side to the lower side along the surface of the gas diffusion layer 32, whereby the oxidant gas is supplied to the cathode 24. The Thereby, a reaction occurs in the membrane electrode assembly 50. When hydrogen gas is supplied to the catalyst layer 26 via the gas diffusion layer 28, hydrogen in the gas becomes protons, and these protons move through the solid polymer electrolyte membrane 20 to the cathode 24 side. At this time, the emitted electrons move to the external circuit and flow into the cathode 24 from the external circuit. On the other hand, when air is supplied to the catalyst layer 30 through the gas diffusion layer 32, oxygen is combined with protons to become water. As a result, electrons flow from the anode 22 toward the cathode 24 in the external circuit, and power can be taken out.

The solid polymer electrolyte membrane 20 exhibits good ionic conductivity in a wet state, and functions as an ion exchange membrane that moves protons between the anode 22 and the cathode 24. The solid polymer electrolyte membrane 20 is formed of a solid polymer material such as a fluorine-containing polymer or a non-fluorine polymer, and is, for example, a sulfonic acid type perfluorocarbon polymer, polysulfone resin, a phosphonic acid group or a carboxylic acid group-containing perfluorocarbon polymer. A fluorocarbon polymer or the like can be used. Examples of the sulfonic acid type perfluorocarbon polymer include Nafion (manufactured by DuPont: registered trademark) 112. Examples of non-fluorine polymers include sulfonated aromatic polyetheretherketone and polysulfone. The film thickness of the solid polymer electrolyte membrane 20 is 20 to 50 μm.

The catalyst layer 26 constituting the anode 22 is composed of an ion conductor (ion exchange resin) and carbon particles carrying a metal catalyst, that is, catalyst-carrying carbon particles. The film thickness of the catalyst layer 26 is 10 to 30 μm. The ion conductor connects the carbon particles carrying the alloy catalyst and the solid polymer electrolyte membrane 20, and has a role of transmitting protons between the two. The ionic conductor may be formed from the same polymer material as the solid polymer electrolyte membrane 20.

Examples of the metal catalyst used for the catalyst layer 26 include an alloy catalyst made of noble metal and ruthenium. Examples of the noble metal used in the alloy catalyst include platinum and palladium. Examples of the carbon particles supporting the metal catalyst include acetylene black, ketjen black, carbon nanotube, and carbon nano-onion.

The gas diffusion layer 28 constituting the anode 22 has a gas diffusion base material 27 and a microporous layer 29 (microporous layer: MPL) applied to the gas diffusion base material. The gas diffusion base material 27 is preferably composed of a porous body having electronic conductivity, and for example, carbon paper, carbon woven fabric or nonwoven fabric can be used.

The microporous layer 29 applied to the gas diffusion base material 27 is a kneaded product (paste) obtained by kneading a conductive powder and a water repellent. For example, carbon black can be used as the conductive powder. In addition, as the water repellent, a fluorine resin such as tetrafluoroethylene resin (PTFE) or tetrafluoroethylene / hexafluoropropylene copolymer (FEP) can be used. The water repellent agent preferably has binding properties. Here, the binding property refers to a property that can be made sticky (state) by joining things that are less sticky or those that tend to break apart. Since the water repellent has binding properties, a paste can be obtained by kneading the conductive powder and the water repellent. The gas diffusion base material 27 has a first surface S1 formed on the electrolyte membrane 20 side and a second surface S2 formed on the opposite side of the electrolyte membrane (that is, the gas flow path 38 side). The first surface S1 and the second surface S2 face each other in the thickness direction D1 of the anode and the gas diffusion layer.

The microporous layer 29 is applied from the first surface S1 (front surface), and a predetermined amount of the microporous layer 29 penetrates into the thickness direction D1 up to the second surface S2 (back surface). It arrange | positions in the gas diffusion base material 27 between the base materials 27 (namely, on 1st surface S1). The microporous layer 29 has continuity at the boundary portion with the gas diffusion base material 27 and also has continuity in the gas diffusion base material 27 from the first surface S1 toward the second surface S2. That is, it is formed so as not to be interrupted in the middle. As a result, a carbon path, which is a discharge path of generated water generated by the electrochemical reaction, can be formed, and the discharge capacity of the generated water in the gas diffusion layer 28 can be enhanced. The detailed structure of the gas diffusion layer 28 will be described later.

The catalyst layer 30 constituting the cathode 24 is composed of an ion conductor (ion exchange resin) and carbon particles carrying a catalyst, that is, catalyst-carrying carbon particles. The ionic conductor connects the carbon particles carrying the catalyst and the solid polymer electrolyte membrane 20, and has a role of transmitting protons between the two. The ionic conductor may be formed from the same polymer material as the solid polymer electrolyte membrane 20. For example, platinum or a platinum alloy can be used as the supported catalyst. Examples of the metal used for the platinum alloy include cobalt, nickel, iron, manganese, iridium and the like. Examples of the carbon particles supporting the catalyst include acetylene black, ketjen black, carbon nanotube, and carbon nano-onion.

The gas diffusion layer 32 constituting the cathode 24 has a gas diffusion base material 31 and a microporous layer 33 applied to the gas diffusion base material 31. The gas diffusion base material 31 is preferably composed of a porous body having electronic conductivity, and for example, carbon paper, carbon woven fabric or nonwoven fabric can be used. In consideration of productivity, it is preferable to use a common carbon paper as a base material for the gas diffusion layer 32 and the gas diffusion layer 28. The gas diffusion base material 31 has a first surface S3 formed on the electrolyte membrane 20 side and a second surface S4 formed on the opposite side of the electrolyte membrane (that is, the gas flow path 40 side). The first surface S3 and the second surface S4 face each other in the thickness direction D1 of the cathode and the gas diffusion layer.

The microporous layer 33 is applied from the first surface S3 (front surface), and a predetermined amount of the microporous layer 33 enters the thickness direction D1 up to the second surface S4 (back surface). It arrange | positions in the gas diffusion base material 31 between the base materials 31 (namely, on 1st surface S3). The microporous layer 33 has continuity at the boundary portion with the gas diffusion base material 31 and also has continuity in the gas diffusion base material 31 from the first surface S3 toward the second surface S4. That is, it is formed so as not to be interrupted. As a result, a carbon path, which is a discharge path of generated water generated by the electrochemical reaction, can be formed, and the discharge capacity of the generated water in the gas diffusion layer 32 can be enhanced. The detailed structure of the gas diffusion layer 32 will be described later.

The configuration of the gas diffusion layers 28 and 32 will be described with reference to FIG. Figure 3 is a structural perspective view schematically showing a fuel cell electrode (anode 22 or cathode 24), and is a view showing a state of a cross section CS _x in a given cross-sectional position t = x of the fuel cell electrode . In the following description, L is the size of the gas

diffusion base materials

27 and 31 in the thickness direction D1. A predetermined cross-sectional position in the thickness direction D1 is t = x, and a cross-section at the predetermined cross-sectional position t (= x) is CS _x . The cross section CS _x is a plane perpendicular to the thickness direction D1 at the cross section position t (= x).

The amount of the microporous layers 29 and 33 in the gas diffusion layers 28 and 32 is acquired by analysis by three-dimensional measurement X-ray CT. A predetermined region (region from cross-sectional position t = 0 to cross-sectional position t = END) in the thickness direction D1 of the

fuel cell electrodes

22, 24 is scanned by the three-dimensional measurement X-ray CT, and the

fuel cell electrodes

22, 24 are scanned. Acquire 3D data of internal structure. By analyzing such three-dimensional data, the amount of the microporous layers 29 and 33 can be acquired. Note that the start point (cross-section position t = 0) and end point (cross-section position t = END) of the scan can be arbitrarily set. In order to analyze all the microporous layers 29, 33 included in the

fuel cell electrodes

22, 24, the starting point (cross-sectional position t = 0) is the catalyst layers 26, 30 from the ends of the gas diffusion layers 28, 32. The end point (cross-section position t = END) is preferably set on the

gas flow path

38, 40 side from the second surfaces S2, S4.

An image of the cross section CS _{x at} a predetermined cross section position t (= x) is acquired using the three-dimensional data. It shows an example of a cross section CS _x in image in FIG. In the example shown in FIG. 3, the white background portions are the gas

diffusion base materials

27 and 31, and the spots scattered in the spot shape are the

microporous layers

29 and 33, which are the portions constituting the discharge path of the generated water. . By analyzing the image of the cross section CS _x , the area ratios of the microporous layers 29 and 33 at the cross section position t (= x) are acquired. Area ratio, the total area of the

microporous layer

29, 33 on the cross section CS _x, refers to the ratio of the area of the cross section CS _x. By obtaining such an image of the cross-section CS _x at a predetermined pitch along the thickness direction D1 from the cross-section position t = 0 to the cross-section position t = END, the area ratio at each cross-section position t is obtained. . The pitch is preferably set to 0.1 to 2.0 μm. Further, a value obtained by summing all the area ratios at the respective cross-sectional positions at t = 0 to x is acquired as the area ratio cumulative value at the cross-sectional position t = x. Further, a value obtained by summing all the area ratios of the cross-sectional positions t = 0 to END, that is, a value corresponding to the total amount of all the microporous layers 29 and 33 included in the

fuel cell electrodes

22 and 24 is obtained as a standard value. .

After the above calculation, a value obtained by dividing the area ratio at the predetermined cross-sectional position t by the standard value (total of all area ratios) is acquired as the existence frequency (%) at the cross-sectional position t. Such presence frequency (%) can be treated as a value indicating how many

microporous layers

29 and 33 are present at a predetermined cross-sectional position t. Since the existence frequency (%) is a value normalized by the standard value, the

fuel cell electrodes

22 and 24 having different total amounts of the microporous layers 29 and 33 can be compared. By using the occurrence frequency (%) obtained for example, as shown in FIG. 9, with respect to cross-sectional position t in the thickness direction D1, a curve obtained by plotting the amount of

microporous layer

29, 33 on the section CS _x To do. At the cross-sectional position t = x _max (first cross-sectional position), the amount of the microporous layers 29 and 33 is maximized. Note that the method of calculating the existence frequency is not limited to the above-described one, and if it is possible to express how many

microporous layers

29 and 33 are present at a predetermined cross-sectional position t (= x), Such values may be used.

Further, a value obtained by dividing the area ratio cumulative value at the predetermined cross-sectional position t by the standard value (total of all area ratios) is obtained as the existence frequency cumulative value (%) at the cross-sectional position t. Such existence frequency cumulative value (%) is treated as a value indicating how many

microporous layers

29 and 33 exist in the region between the cross-sectional position t = 0 and the cross-sectional position t = x. Can do. Since the existence frequency cumulative value (%) is a value normalized by the standard value, the

fuel cell electrodes

22 and 24 having different total amounts of the microporous layers 29 and 33 can be compared. Using the cumulative existence frequency (%), for example, as shown in FIG. 10, the microporous layers 29 and 33 existing in the region on the

catalyst layer

26 and 30 side from the cross-sectional position t with respect to the cross-sectional position t. Acquire a curve plotting the cumulative frequency of existence. The cumulative existence frequency is 0% at the cross-sectional position t = 0, and is 100% at the cross-sectional position t = END. Note that the method for calculating the existence frequency cumulative value is not limited to the above. In addition, the amount of the microporous layers 29, 33 included in the region on the

catalyst layer

26, 30 side from the predetermined cross-sectional position t in the thickness direction D1 is relative to the total amount of the microporous layers 29, 33. Any value can be used as long as it is a value that can indicate whether or not there is a ratio, as well as the above-described cumulative existence frequency.

In the gas diffusion layers 28 and 32, the microporous layers 29 and 33 are continuous along the thickness direction D1. The microporous layers 29 and 33 continuously penetrate from the first surfaces S1 and S3 into the gas

diffusion base materials

27 and 31 in the thickness direction D1 and reach the second surfaces S2 and S4. Yes. That is, in the first surfaces S1, S3 and the gas

diffusion base materials

27, 31, the particles constituting the microporous layers 29, 33 are from the first surfaces S1, S3 to the second surfaces S2, S4. A portion where the microporous layers 29 and 33 are completely divided in the thickness direction D1 is not formed in the entire region (for example, a portion divided in a part of the region at a predetermined cross-sectional position is not formed). Even if it exists, it is continuous in other parts). Since the microporous layers 29 and 33 constitute a discharge path of generated water, the discharge path is configured to be continuous in the thickness direction D1 in the gas

diffusion base materials

27 and 31, and the first surfaces S1 and S3. And a path communicating with the second surfaces S2 and S4. Thus, the generated water is efficiently discharged by maintaining the continuous discharge path in the thickness direction D1 in the gas diffusion layers 28 and 32.

The amount of the microporous layers 29 and 33 on the cross section perpendicular to the thickness direction D1 is maximized at the cross sectional position t = x _max (first cross sectional position) in the thickness direction D1, and the cross sectional position t = x _max. Decreases toward the second surfaces S2 and S4. In the region from the sectional position _{t = x max} the second surface S2, S4 side, the amount of

microporous layer

29, 33 in the cross section CS _x is uniformly reduced toward the second surface S2, S4 . In other words, toward the second surface S2, S4, or the amount of the

microporous layer

29, 33 in the cross section CS _x decreases, or the same amount is maintained stays increases Kyokusho manner as to increase . For example, if there is a divided region in the gas diffusion layers 28 and 32 in which the microporous layers 29 and 33 are largely divided in the thickness direction D1 (even if the generated water discharge path is secured in other portions). ) Water retention occurs in the divided area, and drainage efficiency decreases. Such occurrence frequency of the

microporous layer

29, 33 of the cross-section CS _x in the dividing region (%) is partially reduced, increasing again at the second surface S2, S4-side portion than dividing region. On the other hand, toward the cross-sectional position _{t = x max} to the second surface S2, S4, structure occurrence frequency of the microporous layer 29, 33 (%) decreases uniformly, the occurrence frequency of the

microporous layer

29, 33 The area where (%) partially decreases, that is, the divided area that is large enough to cause water retention is not formed (or even if there is a small divided area, the drainage performance is not affected). Structure). Therefore, a structure in which water retention does not occur in the middle of the generated water discharge path can be achieved.

Specifically, a curve obtained by plotting the amount of the microporous layers 29 and 33 on the cross section CS _{x with} respect to the cross section position t is minimal between the cross section position t = x _max and the second surfaces S2 and S4. It is preferable not to have a point (for example, in the graph EL1 in the example of FIG. 9, in the region on the gas flow path side from the cross-sectional position t = x _max , the entire graph is reduced without forming a minimum point. is doing). Alternatively, even if there is a minimum point, the difference between the maximum value on the second surface S2, S4 side from the minimum point and the value at the minimum point is 5% of the value at the cross-sectional position t = _xmax . The following is preferable. If it is 5% or less, the drainage performance is not affected, and it can be handled as being within the range of manufacturing errors. For example, as shown in the graph EL2 in FIG. 9, even if the gas flow path side has a minimum point PK2 and a maximum point PK3 with respect to the maximum maximum point PK1, the value of the maximum point PK3 and the minimum point PK2 If the difference between the values is 5% or less of the value of the maximum point PK1, it can be handled as being within the range of manufacturing errors. Further, inflection points that occur locally within the range of 2 μm or less in the thickness direction D1 (for example, a data portion that protrudes by one or two points in the three-dimensional data analysis) are also within the error range. Can be treated as a thing.

In addition, when the amount of the microporous layers 29 and 33 is uniformly reduced as approaching the second surfaces S2 and S4, a graph of the existence frequency cumulative value is a cross-sectional position t = x as shown by a graph ML1 in FIG. A curve that curves asymptotically toward 100% in a region on the gas flow path side from _max (only a curve that curves so that the area graph on the gas flow path side from the cross-sectional position t = x _max is convex upward) Configured by). On the other hand, when the amount of the microporous layers 29 and 33 does not decrease uniformly as approaching the second surfaces S2 and S4, the existence frequency cumulative value graph is like a portion indicated by EP in the graph ML2 of FIG. , in the region of the gas flow path side than the cross-sectional position t = x _max, which may draw a curved portion curved to be convex downward.

The amount of the microporous layers 29 and 33 on the cross section perpendicular to the thickness direction D1 is not particularly limited in the form of increase in the region closer to the catalyst layers 26 and 30 than the cross sectional position t = x _max. It is preferable to increase from the side (first surface S1, S3 side) toward the cross-sectional position t = _xmax . In the region from the sectional position _{t = x max} the first surface S1, S3 side has increased uniformly according to the amount of

microporous layer

29, 33 in the cross section CS _x approaches the cross-sectional position _{t = x max.} That is, as the cross-sectional position t = x _max is approached, the amount of the microporous layers 29 and 33 in the cross-section CS _x increases, or even if the same amount is maintained or decreased, it only decreases locally. For example, in the

gas diffusion layer

28 and 32, the large shed dividing region to

microporous layer

29, 33 thickness direction D1 are present, as is ensured the discharge path of the generated water in the (other parts ) Water retention occurs in the divided area, and drainage efficiency decreases. Such occurrence frequency of the

microporous layer

29, 33 of the cross-section CS _x in the dividing region (%) is partially reduced, increases again in partial cross-sectional position t = x _max side of the dividing region. On the other hand, toward the

catalyst layer

26, 30 side (first surface S1, S3 side) to the cross-sectional position _{t = x max,} structure occurrence frequency of the microporous layer 29, 33 (%) increases uniformly, the A region where the existence frequency (%) of the microporous layers 29 and 33 is partially reduced, that is, a divided region that is large enough to cause water retention is not formed (or even if a small divided region exists) It is a structure that does not affect drainage performance). Therefore, a structure in which water retention does not occur in the middle of the generated water discharge path can be achieved.

For example, a curve obtained by plotting the amount of the microporous layers 29 and 33 on the cross section CS _{x with} respect to the cross section position t does not have a minimum point between the catalyst layers 26 and 30 and the cross section position t = x _max. it is preferred (e.g., the graph EL1 in the example of FIG. 9, in the region of the catalyst layer side of the cross-sectional position t = x _max, as a trend for the entire graph, without minimum point is formed, has increased). Thus, the cross-sectional position _{t = x max} catalyst layer than 26, 30 (the first surface S1, S3 side), an increased amount of

microporous layer

29, 33 toward the cross-sectional position _{t = x max,} generated It can be set as the structure which does not generate | occur | produce water retention in the middle of the discharge route of water.

Alternatively, even if it has a minimum point, the difference between the maximum value on the catalyst layer side from the minimum point and the value at the minimum point may be 5% or less of the value at the cross-sectional position t = _xmax . preferable. If it is 5% or less, the drainage performance is not affected, and it can be handled as being within the range of manufacturing errors. Further, inflection points that occur locally within the range of 2 μm or less in the thickness direction D1 (for example, a data portion that protrudes by one or two points in the three-dimensional data analysis) are also within the error range. Can be treated as a thing.

In addition, when the amount of the microporous layers 29 and 33 increases uniformly as approaching the cross-sectional position t = x _max , the graph of the accumulated existence frequency is the cross-sectional position t = x _max as shown in the graph ML1 of FIG. A curve that curves asymptotically toward 0% in the region closer to the catalyst layer is drawn (only by a curve that curves so that the region graph on the catalyst layer side becomes convex downward from the cross-sectional position t = _xmax) It is configured). On the other hand, when the amount of the microporous layers 29 and 33 does not increase uniformly as approaching the cross-sectional position t = x _max , the graph of the accumulated existence frequency shows the catalyst more than the cross-sectional position t = x _max in the graph ML2 of FIG. There is a case where a curved portion that curves upward and then curves downward is projected as in the layer side portion.

The amount of the microporous layers 29, 33 included in the region on the

catalyst layer

26, 30 side (first surface S1, S3 side) from the center position of the gas

diffusion base material

27, 31 in the thickness direction D1 is for the fuel cell. The total amount of the microporous layers 29 and 33 in the

electrodes

22 and 24 is preferably 80% or more, and more preferably 85% or more. In the present embodiment, the ratio of the amount of the microporous layers 29 and 33 in the gas diffusion layers 28 and 32 is indicated by the cumulative existence frequency (%) of the microporous layers 29 and 33 shown in FIG. Thus, by setting it as 80% or more, the quantity of the microporous layers 29 and 33 in the area | region of the interface side of the catalyst layers 26 and 30 and the microporous layers 29 and 33 can fully be ensured, and the said interface High production water drawing ability from can be demonstrated. In addition, the microporous layers 29 and 33 have continuity with respect to the region on the gas flow path side from the center position of the gas

diffusion base materials

27 and 31, and the amount is sufficient to reach the second surfaces S2 and S4. It is necessary to secure. Therefore, the amount of the fine pore layers 29, 33 included in the region on the

catalyst layer

26, 30 side from the center position of the gas

diffusion base materials

27, 31 in the thickness direction D1 is the fine pores in the

fuel cell electrodes

22, 24. The total amount of the

layers

29 and 33 is preferably 98% or less, more preferably 95% or less.

The microporous layers 29 and 33 extend to the second surfaces S2 and S4 of the gas

diffusion base materials

27 and 31, respectively. By allowing the microporous layers 29 and 33 to reach the second surfaces S2 and S4, the microporous layers 29 and 33 are formed in the gas

diffusion base materials

27 and 31 from the first surfaces S1 and S3 to the second surfaces S2 and S2, respectively. It is possible to secure a discharge path of the generated water that continues to S4 and reaches the

gas flow paths

38 and 40. Note that the confirmation that the microporous layers 29 and 33 reach the second surfaces S2 and S4 of the gas

diffusion base materials

27 and 31 corresponds to the second surfaces S2 and S4 in the three-dimensional data analysis. This can be done by confirming the presence of the microporous layers 29, 33 on the cross section or by observing the appearance of the second surfaces S2, S4 of the actual fuel cell electrode.

As described above, according to the

fuel cell electrodes

22, 24, the membrane electrode assembly 50, and the fuel cell 10 according to the present embodiment, a continuous discharge path in the thickness direction D <b> 1 is maintained in the gas diffusion layers 28, 32. Thus, the generated water is efficiently discharged. Moreover, it can be set as the structure which does not generate | occur | produce a water retention in the middle of the discharge path | route of generated water. In addition, by sufficiently securing the amount of the fine pore layers 29, 33 in the region on the interface side between the catalyst layers 26, 30 and the fine pore layers 29, 33, it is possible to exert a high ability to withdraw generated water from the interface. Can do. Further, by allowing the microporous layers 29 and 33 to reach the second surfaces S2 and S4, the microporous layers 29 and 33 are continued to the second surfaces S2 and S4, and reach the

gas flow paths

38 and 40. It is possible to secure a discharge path for generated water. While the gas diffusibility can be maintained as described above, the water generated by the electrochemical reaction can be drained efficiently. As a result, it is possible to achieve both water discharge and gas diffusibility as the fuel cell 10 and improve voltage characteristics.

In the fuel cell 10 described above, it is preferable to employ a gas diffusion layer structure that satisfies the above-described conditions in both the anode 22 and the cathode 24, but it is sufficient that only one of them is employed. By adopting the cathode, it is possible to improve the discharge of water generated in the cathode catalyst layer. Further, by adopting the anode, it is possible to improve the discharge performance of the water that is back-diffused from the cathode to the anode through the electrolyte membrane. Reverse diffusion is a phenomenon in which water moves from the cathode to the anode due to the concentration gradient of water in the anode and the cathode.

(Paste application device)
FIG. 4 is a schematic configuration diagram showing the paste coating apparatus 100 according to the present embodiment. The paste applying apparatus 100 is an apparatus that applies a paste for the microporous layers 29 and 33 to the gas

diffusion base materials

27 and 31 constituting the anode 22 and the cathode 24 of the fuel cell 10. By using the paste coating apparatus 100, the gas diffusion layers 28 and 32 having a high drainage property as described above can be produced. In addition, since the paste coating apparatus 100 can be used for both the gas diffusion layers 28 and 32 of the anode 22 and the cathode 24, in the description of the paste coating apparatus 100, the gas diffusion base material in the manufacturing process is CP. The paste will be described as PS. Paste coating apparatus 100 includes a conveyance unit 101 for conveying the gas diffusion substrate CP in the conveying direction D2, the first roll coater coating portion 102A and a second applying a paste PS to the gas diffusion substrate CP by a roll coater coating A roll coater coating unit 102B and a surface finishing unit 103 that performs surface finishing of the paste PS applied to the gas diffusion base material CP are provided. The paste coating apparatus 100 includes a first roll coater coating unit 102A, a second roll coater coating unit 102B, and a surface finishing unit 103 in this order from the upstream side to the downstream side in the transport direction D2 of the transport unit 101. It has.

The transport unit 101 has the gas diffusion base material CP placed on the upper surface 101a, and moves in the transport direction D2 by the rotation of a back roll (not shown) disposed on the lower surface side. The first roll coater application unit 102A and the second roll coater application unit 102B are disposed on the upper surface 101a side of the transport unit 101, and apply the paste PS to the gas diffusion base material CP. A doctor bar 120 for adjusting the amount of paste PS applied to the surface 110a. As the first roll coater coating unit 102A and the second roll coater coating unit 102B, for example, a roll coater coating device (manufactured by Furness Co., Ltd.) can be used. The first roll coater application unit 102A and the second roll coater application unit 102B are performed by single-sided application from the catalyst layer side of the gas diffusion base material CP. That is, it is applied from one surface on the catalyst layer side, and the paste PS is infiltrated into the gas diffusion base material CP to reach the surface on the gas flow path side. Further, the first roll coater application unit 102A and the second roll coater application unit 102B flatten the paste PS applied to the surface 110a of the application roll 110 without causing unevenness, streaks, lumps, or the like. In this state, it can be applied to the gas diffusion base material CP. Accordingly, air is not mixed between the paste PS applied by the first roll coater application unit 102A and the paste PS applied by the second roll coater application unit 102B, and a highly continuous microporous layer is obtained. be able to. The viscosity of the paste PS is preferably 10,000 to 100,000 mPa · s. When the pressure is less than 10,000 mPa · s, the paste PS is likely to penetrate into the gas flow path side of the gas diffusion base material CP, and the amount of the fine pore layer on the catalyst layer side cannot be maintained. On the other hand, when it is larger than 100000 mPa · s, the paste PS becomes difficult to penetrate into the flow path side of the gas diffusion base material CP, and the amount of the microporous layer on the gas flow path side cannot be maintained.

The coating roll 110 is arranged so that the rotation center axis CL is parallel to the upper surface 101a of the transport unit 101 and is orthogonal to the transport direction D2. The coating roll 110 rotates in the rotation direction D3 about the rotation center axis CL. The surface 110a of the coating roll 110 is disposed so as to be separated from the upper surface 101a of the transport unit 101 at the lower end. The gas diffusion base material CP passes between the surface 110a of the application roll 110 and the upper surface 101a of the transport unit 101, and the paste PS applied to the surface 110a of the application roll 110 is applied to the gas diffusion group at the application position 111. Transferred to material CP. The doctor bar 120 is disposed upstream of the application position 111 in the rotation direction D3. Thus, the paste PS applied to the surface 110a of the application roll 110 is applied at the application position 111 in a state where the film thickness (application amount) is adjusted and smoothed. The material of the coating roll 110 is preferably urethane, but stainless steel (SUS) can also be used.

The surface finishing unit 103 includes a squeegee 104 disposed on the upper surface 101 a side of the transport unit 101. The squeegee 104 is disposed so as to form a gap between the lower end portion and the upper surface 101a of the transport unit 101, and the paste PS that is applied to the gas diffusion substrate CP through which the gas diffusion substrate CP passes. Surface finishing is performed. The material of the squeegee 104 is preferably stainless steel (SUS), but polyethylene or urethane can also be used.

The configuration of the doctor bar 120 will be described in detail with reference to FIG. FIG. 5 is an enlarged view of the paste PS removing portion 125 of the doctor bar 120. FIG. 5 is a view as seen from the direction of the rotation center axis of the coating roll 110. As illustrated in FIG. 5, the doctor bar 120 includes a removing unit 125 that removes excess paste PS from the paste PS applied to the surface 110 a of the application roll 110. The removing unit 125 has a function of smoothing the paste PS applied to the surface 110a. The material of the doctor bar 120 is preferably stainless steel (SUS), but urethane can also be used.

The removal unit 125 includes a removal surface 121 that extends so as to face the surface 110a of the application roll 110, a folded surface 122 that intersects with the removal surface 121 and extends away from the surface 110a of the application roll 110, and a removal surface 121. And an edge portion 123 formed between the folded surface 122. A paste PS is supplied between the removal surface 121 and the coating roll 110.

The edge portion 123 constitutes the nearest point P1 closest to the surface 110a of the coating roll 110 in the removing portion 125. When the closest contact point P1 and the rotation center axis line CL are connected by a virtual line L1, a portion constituting the removal unit 125 is provided only on the virtual line L1 or on the upstream side in the rotation direction D3 from the virtual line L1. . In the removal portion 125 in the present embodiment, the removal surface 121 extends on the upstream side in the rotation direction D3 with respect to the edge portion 123 that forms the closest point P1. In addition, the edge portion 123 is formed at an acute angle, and the folded surface 122 is folded back in a direction away from the imaginary line L1 from the edge portion 123 toward the upstream side. Accordingly, the folded surface 122 is disposed on the upstream side in the rotation direction D3 from the virtual line L1. Therefore, there is no portion of the removal portion 125 that protrudes downstream in the rotation direction D3 from the virtual line L1, and any portion is provided only on the virtual line L1 and upstream in the rotation direction D3 from the virtual line L1. ing. Note that the folded surface 122 constituting the removal portion 125 is a portion directly connected to the edge portion 123. A portion that is away from the edge portion 123, such as the surface 127 and the support portion 126 that are separated from the edge portion 123, does not affect the removal performance of the paste PS, and affects the smoothness of the paste PS after removal. The portion that cannot exert the influence on the value is not included in the removal unit 125. Therefore, the surface 127 and the support part 126 may protrude downstream from the virtual line L1 in the rotation direction D3. The edge portion 123 may be formed with R and may be chamfered. As long as the R is chamfered or chamfered within the range formed in a normal machining process, the paste PS is not pulled even if the R 123 or chamfer is applied to the edge portion 123, and the coating performance is affected. It is because it does not reach. In addition, when R-bending or chamfering is performed, an intersection point (that is, the front end of the edge portion 123 before R-bending or chamfering is performed) when the removal surface 121 and the folded surface 122 are extended to the front end side is recently set. Set as contact P1.

The configuration of the removing unit 125 may be changed as long as the removing unit 125 does not come downstream in the rotation direction D3 from the virtual line L1. The angle A of the removal portion 125, that is, the angle A between the removal surface 121 and the folded surface 122 is preferably 30 ° to 90 °, and more preferably 60 ° or less. By setting the angle to 30 ° or more, it is possible to ensure the accuracy of creating the removal portion 125 and ensure the strength. By setting the acute angle to 60 ° or less, the folded surface 122 can be more reliably prevented from pulling the paste PS after film thickness adjustment. Further, the angle B between the removal surface 121 and the virtual line L1 is preferably 90 ° to 120 °. By setting it to 120 ° or less, damage to the coating roll 110 can be reduced. However, the angle adjustment is performed within a range where “angle A + angle B” is 180 ° or less so that the removing unit 125 does not come downstream in the rotation direction D3 from the virtual line L1. In addition, the doctor bar 120 is set to an angle that does not interfere with the gas diffusion base material CP being conveyed.

For example, the removal unit 125 may be configured as shown in FIG. In the example shown in FIG. 6A, the removal surface 121 and the folded surface 122 are perpendicular to each other, and the folded surface 122 is arranged on the virtual line L1. In the example shown in FIG. 6B, an arc surface 124 that is curved so as to be parallel to the surface 110 a of the coating roll 110 is formed at the tip of the removal surface 121. When the circular arc surface 124 is formed concentrically around the rotation center axis CL, the entire circular arc surface 124 has a closest point. In such a case, the imaginary line L1 is set to the most downstream closest point P1 (that is, the edge portion 123) in the rotation direction D3 among the plurality of closest points.

Returning to FIG. 5, a gap is formed between the edge portion 123 constituting the closest point P <b> 1 and the surface 110 a of the coating roll 110. Of the paste PS applied to the coating roll 110, the paste passing through the gap travels toward the coating position 111 in a state where the excess is removed and smoothed by the removal surface 121 and the edge portion 123. The size of the gap d ₅ by adjusting the amount of paste PS to be transferred to the gas diffusion substrate CP is adjusted. The size d ₅ of the gap than the first roll coater coating portion 102A on the upstream side in the transport direction D2, preferably towards the second roll coater coating portion 102B of the downstream side is set larger. When the thickness d ₁ of the gas diffusion base material CP is 150 to 230 μm, the size d ₅ of the gap in the first roll coater coating unit 102A is preferably set to 80 to 100 μm, and the second roll coater coating The gap size d ₅ in the portion 102B is preferably set to 100 to 120 μm. By increasing the gap between the second roll coater coating portion 102B relative to the first roll coater coating portion 102A, the amount of the fine pore layer in the region of the catalyst layer side from the substrate center to 80% Can contribute.

Here, a paste coating apparatus according to a comparative example will be described with reference to FIG. In the removal part 225 of the doctor bar 220 which concerns on the comparative example shown to Fig.7 (a), the nearest point P1 is set in the middle of the removal surface 221, and the removal surface 221 is downstream from the virtual line L1 in the rotation direction D3. It has an extending surface 221a. Moreover, the edge part 223 and the folding | turning surface 222 are formed downstream from the virtual line L1. In such a configuration, the paste PS applied to the surface 110a of the coating roll 110 is applied to the surface 221a on the downstream side of the imaginary line L1 even after the film thickness is adjusted by passing through the closest contact P1. Pulling will cause unevenness, streaks, lumps, etc. In the removal part 325 of the doctor bar 320 which concerns on the comparative example shown in FIG.7 (b), although the edge part 323 between the removal surface 321 and the folding surface 322 comprises the nearest point P1, the folding surface 322 is The edge portion 323 extends toward the downstream side in the rotation direction D3. As a result, the removal unit 325 has a portion that protrudes further downstream than the virtual line L1. The said part turns into a part which is easy to pull the surface of paste PS after the edge part 323 passage. In such a configuration, the paste PS applied to the surface 110a of the coating roll 110 is downstream of the imaginary line L1 even after the film thickness is adjusted by passing through the edge portion 323 that is the closest contact P1. It is pulled by the folded surface 322 existing on the side, and unevenness, streaks, lumps and the like are generated.

On the other hand, in the paste coating apparatus 100 according to the present embodiment, the portion constituting the removing unit 125 is on the virtual line L1 or upstream in the rotational direction D3 from the virtual line L1 when viewed from the rotation center axis direction of the coating roll 110. It is provided only on the side. That is, the removal unit 125 has a structure that does not have a portion that protrudes downstream in the rotation direction D3 from the virtual line L1. The removal surface 121 facing the surface 110a of the coating roll 110 can remove excess from the paste PS applied to the surface 110a of the coating roll 110. Further, the edge portion 123 formed between the removal surface 121 and the folded surface 122 is a portion constituting the closest point P1 closest to the surface 110a of the coating roll 110, and is a paste at the downstream end portion of the removal surface 121. While adjusting the thickness of PS, it has the function of smoothing the paste surface. Since the folded surface 122 connected to the edge portion 123 is disposed on the imaginary line L1 or on the upstream side in the rotation direction D3 from the imaginary line L1, the film thickness is adjusted and surface-finished at the edge portion 123. A smooth state can be maintained without pulling the paste surface. Thereby, the paste PS can go to the gas diffusion base material CP in a stable state (smooth state).

As described above, the doctor bar 120 has no portion protruding downstream from the imaginary line L1, and thus the paste PS after the film thickness adjustment is in a stable state without causing unevenness, streaks, lumps, or the like. In the (smooth state), it can go to the gas diffusion base material CP. Thus, by stabilizing (smoothing) the state of the paste to be applied, it is possible to stabilize the application amount of the paste PS. Further, it is possible to stabilize the application state of the paste PS and the penetration depth into the gas diffusion base material CP. In addition, by applying the paste PS in a stable state, the paste PS can penetrate well into the gas diffusion base CP without being interrupted, so that a highly continuous microporous layer can be formed in the gas diffusion base CP. It becomes possible to form. It is also possible to reduce the pre-stirring time of the paste PS (stirring time for suppressing the occurrence of lumps and the like after the paste is put into the roll coater coating apparatus and before coating is started). Furthermore, since it becomes possible to form a microporous layer by such good paste application, the use of the fuel cell electrode produced by the paste application device 100 stabilizes the cell performance of the fuel cell. Can be achieved. By the above, the paste application performance can be improved and the battery performance of the fuel cell can be improved.

In the paste coating apparatus 100 according to the present embodiment, a plurality of coating rolls 110 and doctor bars 120 are provided in the transport direction D2 of the transport unit 101, and the first roll coater coating unit 120A and the second roll. A coater application unit 120B is provided. When using a plurality of roll coater application sections 120A and 120B, a sufficient amount of paste PS can be applied to the gas diffusion base material CP even if the film thickness of the paste PS per application roll 110 is reduced. Become. When the film thickness per coating roll 110 is kept small, the variation in the paste PS can be reduced as compared with the case where the film thickness is large. Here, when a plurality of rolls are used in a state where unevenness, streaks, lumps, etc. are generated in the paste as in the conventional case, air enters between the first-layer paste PS and the second-layer paste PS. Paste PS is divided and continuity is lost. However, in the present embodiment, since the paste PS can be applied in a smooth state, even when a plurality of application rolls 110 are used, the paste PS is between the first-layer paste PS and the second-layer paste PS. It is possible to prevent air from getting into the air and maintain high continuity.

The gas diffusion layers, fuel cell electrodes, and membrane electrode assemblies according to Examples and Comparative Examples were manufactured by the manufacturing method described below, and analyzed and verified.

(Example: Manufacturing method)
<Preparation of cathode gas diffusion layer>
Carbon paper (TGP-H-060 manufactured by Toray Industries, Inc.) serving as a base material for the cathode gas diffusion layer was prepared, and carbon paper: FEP (tetrafluoroethylene-hexafluoropropylene copolymer) = 95: 5 (by weight ratio) The carbon paper is immersed in the FEP dispersion so as to be 60:40 (for the anode), dried at 60 ° C. for 1 hour, and then heat treated at 380 ° C. for 15 minutes (FEP water repellent) Process). Thereby, the carbon paper is subjected to water repellent treatment almost uniformly.

Vulcan XC-72R (manufactured by CABOT: Vulcan XC72R) and terpineol (manufactured by Kishida Chemical Co., Ltd.) as a solvent and Triton (manufactured by Kishida Chemical Co., Ltd.) as a solvent, and the weight ratio of Vulcan XC-72R: Terpineol: A carbon paste is prepared by mixing uniformly at room temperature for 60 minutes using a universal mixer (manufactured by DALTON) so that Triton = 20: 150: 3.

The weight ratio of the low molecular fluororesin (Daikin: Lubron LDW410) and the high molecular fluororesin (DuPont: PTFE-31JR) contained in the dispersion is low. = 20: 3 is mixed to prepare a mixed fluororesin for cathode. The carbon paste is put into a hybrid mixer container and cooled until the carbon paste reaches 10 to 12 ° C. The above-mentioned mixed fluororesin for cathode is put into the cooled carbon paste so that the weight ratio is carbon paste: mixed fluororesin for cathode (fluorine resin component contained in the dispersion) = 31: 1, and a hybrid mixer (KEYENCE) Mix for 12 to 18 minutes in EC500) mixing mode. The timing of stopping the mixing is until the paste temperature reaches 50 to 55 ° C., and the mixing time is appropriately adjusted. After the paste temperature reaches 50 to 55 ° C., the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 1 to 3 minutes. The paste after defoaming is naturally cooled to produce a cathode gas diffusion layer paste.

The cathode gas diffusion layer paste that has been cooled to room temperature is applied to the surface of the carbon paper that has been subjected to FEP water repellent treatment so that the coating state in the carbon paper surface is uniform. For the application of the cathode gas diffusion layer paste, the paste application apparatus 100 shown in FIG. 4 was used. In this embodiment, a roll coater coating device (manufactured by Furness Co., Ltd.) was used as the roll

coater coating sections

102A and 102B. The viscosity of the paste PS was 50000 mPa · s, and the thickness d ₁ of the gas diffusion base material CP was 190 μm. In the first roll coater application unit 102A, the size of the gap d ₅ = 80 μm, the angle A = 30 °, and the angle B = 90 ° between the application roll 110 and the removal unit 125 were set. In the second roll coater coating unit 102B, the size of the gap d ₅ between the coating roll 110 and the removing unit 125 was set to 100 μm, the angle A was 30 °, and the angle B was 90 °. In the surface finishing unit 103, the angle θ between the squeegee 104 and the transport unit 101 is set to 155 °. Dry at 60 ° C. for 60 minutes with a hot air dryer (manufactured by Thermal). Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the cathode gas diffusion layer.

<Cathode catalyst slurry preparation>
Platinum-supported carbon (TEC36F52, Tanaka Kikinzoku Kogyo Co., Ltd.) is used as the cathode catalyst, and SS700C solution (20%, Ew = 780, moisture content = 36 wt% (25 ° C.), ionomer solution Aciplex manufactured by Asahi Kasei Chemicals Co., Ltd.) as the ion conductor. (Registered trademark) SS700C, hereinafter abbreviated as SS700). 10 mL of ultrapure water was added to 5 g of platinum-supporting carbon and stirred, and then 15 mL of ethanol was added. The catalyst dispersion solution was subjected to ultrasonic stirring and dispersion for 1 hour using an ultrasonic stirrer. A predetermined SS700 solution was diluted with an equal amount of ultrapure water and stirred with a glass rod for 3 minutes. Thereafter, ultrasonic dispersion was performed using an ultrasonic cleaner for 1 hour to obtain an SS700 aqueous solution. Thereafter, the SS700 aqueous solution was slowly dropped into the catalyst dispersion. During the dropping, stirring was continuously performed using an ultrasonic stirrer. After completion of the dropwise addition of the SS700 aqueous solution, 10 g (1: 1 by weight) of a mixed solution of 1-propanol and 1-butanol was dropped, and the resulting solution was used as a catalyst slurry. During mixing, the water temperature was all adjusted to about 60 ° C., and ethanol was evaporated and removed.

<Production of cathode>
The cathode catalyst slurry prepared by the above method was applied to the cathode gas diffusion layer by screen printing (150 mesh), dried at 80 ° C. for 3 hours, and heat treated at 180 ° C. for 45 minutes.

<Preparation of anode gas diffusion layer>
Carbon paper (manufactured by Toray Industries, Inc .: TGP-H-060) serving as a base material for the anode gas diffusion layer is prepared, and water repellent treatment is performed in the same manner as the anode gas diffusion layer.

The carbon paste and the low molecular fluororesin are mixed in a hybrid mixer container with a weight ratio of carbon paste: low molecular fluororesin (hereinafter referred to as anode fluororesin) (fluororesin component contained in the dispersion) = 26. : Add to 3 and mix for 15 minutes in the mixing mode of the hybrid mixer. After mixing, the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 4 minutes. When the supernatant liquid accumulates on the upper part of the paste after defoaming, the supernatant liquid is discarded, and the paste is naturally cooled to complete the anode gas diffusion layer paste.

The anode gas diffusion layer paste cooled to room temperature was applied to the surface of the carbon paper subjected to FEP water repellent treatment so that the coating state in the carbon paper surface was uniform. For applying the anode gas diffusion layer paste, the paste coating apparatus 100 shown in FIG. 4 was used. In this embodiment, a roll coater coating device (manufactured by Furness Co., Ltd.) was used as the roll

coater coating sections

102A and 102B. The viscosity of the paste PS was 30000 mPa · s, and the thickness d ₁ of the gas diffusion base material CP was 190 μm. In the first roll coater coating unit 102A, the size of the gap d ₅ = 100 μm, the angle A = 30 °, and the angle B = 90 ° between the coating roll 110 and the removal unit 125 were set. In the second roll coater coating unit 102B, the size of the gap d ₅ between the coating roll 110 and the removing unit 125 was set to 120 μm, the angle A = 30 °, and the angle B = 90 °. In the surface finishing unit 103, the angle θ between the squeegee 104 and the transport unit 101 is set to 155 °. Dry at 60 ° C. for 60 minutes with a hot air dryer (manufactured by Thermal). Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the anode gas diffusion layer.

<Preparation of catalyst slurry for anode>
The anode catalyst slurry preparation method is the same as the cathode catalyst slurry preparation method except that platinum ruthenium (PtRu) -supported carbon (TEC61E54, Tanaka Kikinzoku Kogyo Co., Ltd.) is used as the catalyst.

<Production of anode>
The cathode catalyst slurry prepared by the above method was applied to the anode gas diffusion layer by screen printing (150 mesh), dried at 80 ° C. for 3 hours, and heat-treated at 180 ° C. for 45 minutes.

<Preparation of membrane electrode assembly>
Hot pressing is performed in a state where a solid polymer electrolyte membrane having a thickness of 50 μm is sandwiched between the anode and the cathode produced by the above method. Aciplex (registered trademark) (SF7202, manufactured by Asahi Kasei E-Materials) was used as the solid polymer electrolyte membrane. A membrane electrode assembly according to the example was manufactured by hot pressing the anode, the solid polymer electrolyte membrane, and the cathode under the bonding conditions of 170 ° C. and 200 seconds.

(Comparative example: Manufacturing method)
In the production of the cathode gas diffusion layer and the anode gas diffusion layer, the doctor bar shown in FIG. 7A was used as the doctor bar used in the first roll coater coating unit 102A and the second roll coater coating unit 102B. Except for the point, it is the same as the manufacturing method according to the example. The size of the portion extending from the imaginary line L1 was d ₆ = 10 mm.

(Analysis of microporous layer)
The produced cathodes according to Examples and Comparative Examples were analyzed. For acquisition and analysis of three-dimensional data, SMX-160CTS (manufactured by Shimadzu Corporation), which is a three-dimensional measurement X-ray CT, was used. The cross-sectional position t = 0 is set at a position closer to the solid polymer electrolyte membrane than the catalyst layer 30, the cross-sectional position t = END is set at a position closer to the gas flow path than the gas diffusion layer 32, and the internal structure over a range of 300 μm 3D data was acquired. FIG. 8 is an image showing the catalyst layer 30 and the microporous layer 33 present in the cathode 24. FIG. 8A is an image according to the example, and FIG. 8B is an image according to the comparative example. The image is produced based on the three-dimensional data, and is an internal image of the cathode 24 viewed from the direction orthogonal to the thickness direction D1 (viewed from the viewpoint VP in FIG. 3). The image in FIG. 8 does not show only the catalyst layer 30 and the microporous layer 33 present on one cross section obtained by cutting a predetermined part when viewed from the viewpoint VP, but is tertiary in the depth direction viewed from the viewpoint VP. All of the catalyst layer 30 and the microporous layer 33 that originally exist are collectively shown on the two-dimensional image.

As can be understood from FIG. 8B, in the cathode 24 according to the comparative example, a divided portion DE in which the microporous layer 33 is largely divided in the thickness direction D1 is formed. The divided portion DE is formed in substantially the entire left half region of the cathode 24 in the width direction. For example, when acquiring an image as shown in cross-section CS _x in FIG. 3 in cross-section position corresponding to the dividing portion DE, substantially left half area of the cross section CS _x is not at all present microporous layer 33 Not observed. As described above, in the divided portion DE where the portion where the microporous layer 33 does not have continuity covers a wide range, the discharge path of the generated water is not sufficiently secured, and water retention occurs. In the comparative example, the first-layer paste PS applied by the first roll coater application unit 102A is not kept smooth, and the second-layer paste PS that is not kept smooth is applied thereon. Thus, it is understood that such a divided portion DE is formed by air mixing between the first layer and the second layer. On the other hand, as understood from FIG. 8 (a), in the cathode 24 according to the example, a large divided portion as in the comparative example is not formed, and what is observed is a part of the gas flow path side. Only a small part is formed in the area. Thus, it is understood that a good microporous layer 33 with high continuity can be obtained by using the paste coating apparatus 100 according to the present embodiment.

Next, from the obtained three-dimensional data, a cross-sectional image at each cross-sectional position is acquired at a pitch of 0.8 μm from the cross-sectional position t = 0 to the cross-sectional position t = END. By analyzing each cross-sectional image, the existence frequency (%) of the microporous layer 33 at each cross-sectional position is acquired. The results are shown in FIG. The result of the example is shown by a graph EL1, and the result of the comparative example is shown by a graph EL2. Further, the cumulative existence frequency (%) is acquired from the cross-sectional position t = 0 to the cross-sectional position t = END. The results are shown in FIG. The result of the example is shown by a graph ML1, and the result of the comparative example is shown by a graph ML2.

As can be understood from the graph EL1 in FIG. 9, in the example, the existence frequency (the amount of the microporous layer on the cross section) becomes maximum at the cross section position t = x _max (first cross section position). Further, the occurrence frequency decreases toward the cross-sectional position t = x _max to a second surface S4 of the gas flow path side. That is, in the region on the second surface S4 side from the cross-sectional position t = _xmax , the amount of the microporous layer 33 in the cross-section is uniformly reduced as it approaches the second surface S4. Although a portion that slightly increases or decreases in a local area can be seen, it is only a very small change, and is reduced uniformly when viewed as the entire graph EL1. Due to the thus uniformly reduced, the graph ML1 in Fig. 10, the gas flow path side than the cross-sectional position t = x _max, only smoothly increasing curve such that convex upward is drawn . On the other hand, as understood from the graph EL2 of FIG. 9, in the comparative example, even after the existence frequency reaches the maximum at the maximum point PK1, the existence frequency greatly fluctuates because the divided portion DE is formed. A minimum point PK2 and a maximum point PK3 are formed. It is understood that the difference between the values of the minimum point PK2 and the maximum point PK3 is large, and the existence frequency is not uniformly reduced. In the graph ML2 of FIG. 10 that is not uniformly reduced in this way, a curve portion EP is formed such that the existence frequency cumulative value does not increase smoothly but protrudes downward.

The central position of the gas diffusion base material 31 in the thickness direction D1 is a position indicated by a cross-sectional position = 150 μm. As is apparent from the value of the graph ML1 in FIG. 10, in the embodiment, the existence frequency cumulative value at the center position is 80% or more. That is, in the embodiment, the amount of the microporous layer 33 included in the region on the catalyst layer 30 side from the center position of the gas diffusion base material 31 is 80% or more of the total amount of the microporous layer 33 in the cathode 24. It is understood that On the other hand, as is clear from the value of the graph ML2 in FIG. 10, in the comparative example, the existence frequency cumulative value at the center position is less than 80%. That is, in the comparative example, the amount of the microporous layer 33 included in the region on the catalyst layer 30 side from the central position of the gas diffusion base material 31 is less than 80% of the total amount of the microporous layer 33 in the cathode 24. It is understood that

Further, in the example, it was confirmed by three-dimensional data analysis and appearance observation that the microporous layer 33 extends to the second surface S4 of the gas diffusion base material 31. That is, it is understood that a highly continuous discharge path is secured from the first surface S2 to the second surface S4 of the gas diffusion base material 31. In the comparative example, it extends to the second surface S4. However, as described above, the large divided portion DE is formed inside the gas diffusion base material 31, and the second surface S2 extends from the first surface S2. High continuity between the surfaces S4 is not ensured.

(Single cell performance test)
Moreover, the cell voltage was measured using the membrane electrode assembly of an Example and a comparative example. The measurement conditions are as follows. The measurement result of the cell voltage is shown in “SRG / Air” of FIG. In addition, oxygen gain was measured to verify the drainage performance of the cathode. The oxygen gain is the difference between the cell voltage when the cathode gas is air and the cell voltage when the cathode gas is oxygen. The higher the cathode drainage, the smaller the oxygen gain. The measurement result of the oxygen gain is shown as “O ₂ gain” in FIG.
Anode gas: Reformed hydrogen gas (CO concentration 10ppm)
Cathode gas: Air cell temperature: 70 ° C
Cathode gas humidification temperature: 70 ° C
Anode gas humidification temperature: 70 ° C
Current density: 0.3 A / cm ²

As shown in FIG. 11, the example shows a lower oxygen gain than the comparative example, and it is understood that the example is superior in the discharge characteristic of the generated water. Also, the cell voltage is higher in the example than in the comparative example. From this, it can be understood that the battery performance of the example can be high. From the above, it can be understood that the membrane electrode assembly according to the example can improve the voltage characteristics while satisfying both the water discharging property and the gas diffusing property as the fuel cell. In addition, it is understood that by using the paste coating apparatus 100, the paste coating performance can be improved and the battery performance of the fuel cell can be improved.

The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The form can also be included in the scope of the present invention.

In the above-described manufacturing method, a single-wafer product is used as a base material, but a continuous base material (a long base material that is cut into a desired size after applying a paste) may be used. Moreover, when using a continuous base material, you may change the structure of a conveyance part. That is, as shown in FIG. 4, instead of a type of conveyance unit that moves a substrate placed on a conveyor, a continuous substrate is placed between the rolls, and the substrate is conveyed in the conveyance direction by rotation of the roll. You may employ | adopt the conveyance part of the type sent to. Furthermore, in the above manufacturing method, the catalyst layer is formed on the gas diffusion layer and the electrolyte membrane is joined to the electrode (CCS method). However, after the catalyst layer is formed on the electrolyte membrane, the gas diffusion layer is joined. (CCM method).

The present invention can be used for a paste coating apparatus.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 20 ... Solid polymer electrolyte membrane, 22 ... Anode (electrode for fuel cells), 24 ... Cathode (electrode for fuel cells), 26, 30 ... Catalyst layer, 27, 31 ... Gas diffusion base material, 28 , 32 ... Gas diffusion layer, 29, 33 ... Microporous layer, 50 ... Membrane electrode assembly, 100 ... Paste coating device, 101 ... Conveying section, 102A ... First roll coater coating section, 102B ... Second roll coater Application part, 110 ... application roll, 110a ... surface, 120 ... doctor bar, 121 ... removal surface, 122 ... folding surface, 123 ... edge part, 125 ... removal part, P1 ... closest contact, L1 ... virtual line.

Claims

A paste application device for applying a paste to a gas diffusion base material used in a fuel cell,
A transport unit for transporting the gas diffusion base;
An application roll that rotates in a predetermined rotation direction and applies the paste applied to the surface to the gas diffusion base material transported by the transport unit;
A doctor bar arranged on the upstream side in the rotational direction from the position where the application roll applies the paste to the gas diffusion base material, and adjusting the amount of the paste applied to the surface;
The doctor bar has a removal portion that forms a gap with the surface of the coating roll and removes excess paste applied to the surface.
When the closest point of the removal unit with respect to the surface of the coating roll and the rotation center axis line are connected by a virtual line when viewed from the rotation center axis direction of the coating roll, the portion constituting the removal unit is the virtual A paste application device provided only on the line or upstream of the virtual line in the rotation direction.
The removing unit is
A removal surface extending so as to face the surface of the coating roll;
A folded surface that intersects with the removal surface and spreads in a direction away from the surface of the coating roll;
An edge portion formed between the removal surface and the folded surface and constituting the closest point;
The paste coating apparatus according to claim 1, wherein the folded surface is disposed on the imaginary line or on the upstream side in the rotation direction with respect to the imaginary line when viewed from the rotation center axis direction of the coating roll.
The paste coating apparatus according to claim 1 or 2, wherein a plurality of the coating rolls and the doctor bars are provided with respect to a transport direction of the transport unit.
The said removal part of the said doctor bar arrange | positioned downstream in the said conveyance direction has a larger clearance between the said surface of the said application | coating roll than the said removal part of the said doctor bar arrange | positioned upstream. 3. The paste coating apparatus according to 3.