JP2005276531A - Separator, manufacturing method of separator, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator capable of improving the power generating efficiency of a fuel cell, and to provide a manufacturing method of such a separator, and a fuel cell having such a separator. <P>SOLUTION: A fuel cell comprises an electrolyte membrane, an electrode 16b, and a separator 18b formed on a close contacting surface 20b that comes into close contact with one side of the electrode 16b and having a groove through which an active material flows. In a section perpendicular to the direction in which the active material flows in the groove 22b, a boundary side 34 equivalent to close contacting surface 20b is shorter than a base 36 equivalent to the bottom of the groove 22b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a separator disposed so as to be in close contact with one side surface of an electrode on a membrane electrode structure in which an electrode is disposed on one side surface of an electrolyte membrane, a method for producing such a separator, and a fuel having such a separator. It relates to batteries.

  Conventionally, a fuel cell that generates power using a chemical reaction has been used. As an example of such a fuel cell, there is a fuel cell of Patent Document 1. In this fuel cell, as shown in FIG. 7, a membrane electrode structure 117 is used in which a fuel side electrode 116a is disposed on one side surface of an electrolyte membrane 114 and an oxidant side electrode 116b is disposed on the other side surface. The cell body 112 is formed by sandwiching the membrane electrode structure 117 between the fuel side separator 118a and the oxidant side separator 118b. The separators 118a and 118b have contact surfaces 120a and 120b that are in close contact with the electrodes 116a and 116b. Groove portions 122a and 122b are formed in the contact surfaces 120a and 120b. The electrodes 116a and 116b and the grooves 122a and 122b form flow paths 124a and 124b for supplying an active material for power generation to the electrodes 116a and 116b.

  A fuel such as hydrogen gas is supplied to the fuel side electrode 116a via the fuel side flow path 124a, and an oxidant such as oxygen gas is supplied to the oxidant side electrode 116b via the oxidant side flow path 124b. As a result, a chemical reaction proceeds through the electrolyte membrane 114 to generate power, and a liquid such as water is generated at the oxidant side electrode 116b. In addition, when using fuel gas as a fuel, in order to humidify the electrolyte membrane 114 and to perform electric power generation appropriately, humidifying fuel gas is performed. The oxidizing agent is also humidified for the same reason.

A plurality of minute drain grooves 123 are formed on the inner surfaces of the separators 118a and 118b defining the flow paths 124a and 124b of the fuel cell along the longitudinal direction of the flow paths 124a and 124b. These drain grooves 123 are for removing the liquid generated at the oxidant side electrode 116b, the liquid condensed from the fuel gas, and the like by utilizing the capillary phenomenon.
JP 2000-123848 A

  However, it is difficult in some cases to efficiently discharge the liquid by capillary action, particularly when high-viscosity liquid (for example, caustic aqueous solution) is generated in the oxidant side electrode 116b. For this reason, the liquid generated in the oxidant side electrode 116b or the condensed liquid stays in the vicinity of the oxidant side electrode 116b and accumulates in the flow path 124b. Further, liquid condensed from the fuel gas is accumulated in the flow path 124a. As a result, a part of the electrodes 116a and 116b is shielded by the liquid, the effective reaction area of the electrodes 116a and 116b is reduced, and the power generation efficiency is lowered.

  Here, it is possible to increase the effective reaction area of the electrodes 116a and 116b by increasing the flow area of the flow paths 124a and 124b. However, in this case, the areas of the contact surfaces 120a and 120b between the electrodes 116a and 116b and the separators 118a and 118b are reduced to reduce the adhesion, and fuel and oxidant leak from the flow paths 124a and 124b. , 116b and the separators 118a, 118b are reduced in electrical conductivity and current collection efficiency is reduced. Eventually, power generation efficiency will not be improved sufficiently.

  The present invention has been made paying attention to the above-mentioned problems, and the object thereof is a separator for a fuel cell capable of improving the power generation efficiency of the fuel cell, a method for producing such a separator for a fuel cell, And it is providing the fuel cell which has such a separator.

  A preferred embodiment of the present invention is a fuel cell comprising an electrolyte membrane, an electrode, and a separator having a groove portion formed on a close contact surface that is in close contact with one side surface of the electrode and through which an active material flows. In the cross section perpendicular to the direction in which the active material flows, the fuel cell is characterized in that, in the cross section, the boundary side corresponding to the contact surface is shorter than the bottom side corresponding to the bottom of the groove.

  Preferably, the side connecting the lower end in the gravitational direction of the boundary side to the lower end in the gravitational direction of the bottom side has an inclined portion that falls in the gravitational direction from the boundary side toward the base side. To do.

  Preferably, the inclined portion extends from one end of the boundary side.

  Preferably, the inclined portion is provided over the entire length of the side.

  Preferably, the lower end of the boundary side in the gravitational direction is higher than the lower end of the bottom side in the gravitational direction as viewed in the gravitational direction.

  Preferably, the side edge connecting the upper end in the gravity direction of the boundary edge and the upper edge in the gravity direction of the bottom edge, and the side edge connecting the lower edge in the gravity direction of the boundary edge and the lower edge in the gravity direction of the boundary edge and the boundary edge The angle between the two is an obtuse angle.

  Preferably, the cross section is symmetric with respect to a straight line connecting a midpoint of the boundary side and a midpoint of the bottom side.

  Preferably, it is configured using a member processed by crystal anisotropic etching.

  Preferably, it comprises using the member processed by isotropic etching.

  Another preferable aspect of the present invention is that a membrane electrode structure comprising an electrolyte membrane and an electrode is laminated so as to be in contact with the electrode, while an active material for generating power by the fuel cell is in contact with the membrane electrode structure. A method of manufacturing a separator having a flowing active material flow groove, wherein the first member constituting a part of the separator is connected to a plurality of openings provided on the first member. A step of opening a through-hole that passes through one member and whose cross-sectional area perpendicular to the direction passing through the member monotonously changes from one of the plurality of openings toward the other opening; Joining a second member constituting a part of the separator to the first member so as to close a larger one of the plurality of openings. It is.

  Preferably, the plurality of openings are provided on different surfaces of the first member.

  Preferably, the plurality of openings have different sizes from each other.

  Preferably, an angle formed by a surface corresponding to the opening that contacts the membrane electrode structure and an inner wall of the through hole is an obtuse angle.

  Preferably, the groove width of the active material flow groove is always increased or decreased from one of the plurality of openings toward the other opening.

  Preferably, the through hole is formed from a larger one of the plurality of openings.

  Preferably, a cross section of the active material flow groove in a direction perpendicular to the flow direction of the active material flowing in the active material flow groove is symmetric with respect to the width direction of the active material flow groove.

  Preferably, the step of opening the through hole includes a step of performing crystal anisotropic etching.

  Preferably, the step of opening the through hole includes a step of performing isotropic etching.

  Still another preferred embodiment of the present invention is such that a membrane electrode structure comprising an electrolyte membrane and an electrode is laminated so as to be in contact with the electrode, while an active material for generating power by the fuel cell is in contact with the membrane electrode structure. A separator having a flowing active material flow groove, wherein the separator includes a first member and a second member, and the first member includes a plurality of members provided on the first member. The cross-sectional area of the cross section perpendicular to the direction penetrating the first member so as to connect the openings is perpendicular to the direction penetrating the first member, from one of the plurality of openings toward the other opening. A separator having a monotonously changing through-hole, wherein the second member is joined to the first member so as to close a larger one of the plurality of openings. is there.

  Still another preferred embodiment of the present invention is a fuel cell incorporating the separator according to claim 19.

  According to the present invention, the power generation efficiency of the fuel cell is improved.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1A, the cell body 12 of the fuel cell of the present embodiment has an electrolyte membrane 14. As this electrolyte membrane 14, it is possible to use what is marketed by the brand name Nafion from Dupon, for example.

  A fuel side electrode 16a is laminated on one side surface of the electrolyte membrane 14, and an oxidant side electrode 16b is laminated on the other side surface. A membrane electrode structure 17 is formed by the electrolyte membrane 14, the fuel side electrode 16a, and the oxidant side electrode 16b. As the fuel side electrode 16a and the oxidant side electrode 16b, it is possible to use, for example, carbon paper or a carbon cloth web carrying a catalyst. As the catalyst for the fuel side electrode 16a, for example, platinum or platinum / ruthenium can be used. For the catalyst for the oxidant side electrode 16b, for example, platinum can be used. Further, when the fuel is an alkaline aqueous solution such as a sodium borohydride aqueous solution, it is preferable that the fuel side electrode 16a is formed of a hydrogen storage alloy.

  A fuel-side separator 18a is closely stacked on one side of the fuel-side electrode 16a, and an oxidant-side separator 18b is closely stacked on one side of the oxidant-side electrode 16b. The fuel side separator 18a and the oxidant side separator 18b are made of, for example, a conductor such as stainless steel, preferably titanium or carbon.

  As shown in FIG. 1B, a fuel side groove portion 22a as an active material flow groove is formed on the contact surface 20a in close contact with the fuel side electrode 16a of the fuel side separator 18a. The fuel side groove portion 22a and the fuel side electrode 16a form a fuel side flow path 24a for supplying fuel as an active material to the fuel side electrode 16a. The fuel side groove 22a extends in a zigzag manner on the contact surface 20a of the fuel side separator 18a. A fuel supply hole 26a and a fuel discharge hole 28a are formed at both ends of the fuel side groove 22a so as to penetrate the fuel side separator 18a. As shown in FIG. 1A, the fuel supply hole 26a and the fuel discharge hole 28a are connected to the fuel supply pipe 30a and the fuel discharge pipe 32a connected to the side opposite to the fuel side electrode 16a of the fuel side separator 18a. Each communicates.

  Similarly, in the oxidant side separator 18b, as shown in FIGS. 1A and 1B, an oxidant side groove portion 22b as an active material flow groove through which an oxidant as an active material flows, An oxidant supply hole 26b and an oxidant discharge hole 28b are formed, and an oxidant supply pipe 30b and an oxidant discharge pipe 32b are connected. The oxidant side groove portion 22b and the oxidant side electrode 16b form an oxidant side flow path 24b for supplying an oxidant to the oxidant side electrode 16b.

  FIG. 2 shows a cross section perpendicular to the longitudinal direction of the oxidant side flow path 24b (cross section taken along the line II-II in FIG. 1). This cross section has a boundary side 34 corresponding to the contact surface 20b defined by the oxidant side electrode 16b, and a bottom side 36 facing the boundary side 34 and corresponding to the bottom of the oxidant side groove portion 22b. The boundary side 34 is shorter than the bottom side 36. In the present embodiment, the lower end portion 34 a in the gravitational direction of the boundary side 34 is above the lower end portion 36 a in the gravitational direction of the bottom side 36 as viewed in the gravitational direction.

  A first side 38 extends between a lower end 34a of the boundary 34 in the direction of gravity and a lower end 36a of the bottom 36 in the direction of gravity. An upper end 34b of the boundary 34 and an upper end 36b of the bottom 36 are provided. The second side 40 extends between the two sides. Here, the first side 38 is a straight line, but the side in the present invention may be a straight line or a curved line.

  The first side 38 has an inclined portion 42 that extends with a component in the direction of gravity. In the present embodiment, the first side 38 has a linear inclined portion 42 extending from the lower end 34 a of the boundary side 34 and extending over the entire length of the first side 38. The direction of the inclined portion 42 extending from the lower end portion 34a of the boundary side 34 to the lower end portion 36a of the bottom side 36 (see FIG. 2, arrow A) and the direction extending from the lower end portion 34a of the boundary side 34 to the upper end portion 34b ( The angle .theta. With which reference is made to the arrow B in FIG. 2 is an obtuse angle. The angle θ is defined as the smaller one of the two angles formed by the two directions. The second side 40 extends substantially perpendicular to the boundary side 34.

  Next, the operation of the fuel cell of the present embodiment having the above configuration will be described. When power generation is performed by the fuel cell, fuel is supplied from the fuel supply pipe 30a to the fuel side flow path 24a, and oxidant is supplied from the oxidant supply pipe 30b to the oxidant side flow path 24b. For example, hydrogen gas, an alcohol aqueous solution, or an alkaline aqueous solution (for example, sodium borohydride aqueous solution) is used as the fuel, and for example, air or oxygen gas is used as the oxidizing agent. The fuel flows through the fuel side channel 24a and contacts the fuel side electrode 16a, and the oxidant flows through the oxidant side channel 24b and contacts the oxidant side electrode 16b. As a result, a chemical reaction proceeds through the electrolyte membrane 14 to generate power.

  As a result of the chemical reaction, a liquid such as water or an alkaline aqueous solution is generated at the oxidant side electrode 16b. The liquid generated at the oxidant side electrode 16b moves to the lower end 34a along the boundary side 34 by the action of gravity. Further, since the inclined portion 42 is formed on the first side 38 from the lower end 34 a of the boundary side 34 to the lower end 36 a of the bottom side 36, the boundary side 34 of the first side 38 is formed. The liquid that has moved to the side end starts to move away from the oxidant side electrode 16b due to the action of gravity. Further, the liquid moves on the inclined portion 42 from the boundary side 34 side to the bottom side 36 side, and accumulates at the bottom side 36 end of the first side side 38. The accumulated liquid flows through the oxidant side flow path 24b to the oxidant discharge hole 28b due to the pressure of the oxidant flow.

  Similar to such a liquid, the substance generated in the fuel side electrode 16a as a result of the chemical reaction, the fuel and the oxidant which have not reacted move through the fuel side channel 24a and the oxidant side channel 24b, and the fuel discharge pipe 32a and the oxidant discharge pipe 32b.

  Accordingly, the configuration described above has the following effects. First, the boundary side 34 is shorter than the bottom side 36. For this reason, the liquid can be efficiently moved on the bottom 36 side of the oxidant side flow path 24b, and unnecessary liquid in the oxidant side flow path 24b can be efficiently discharged. Therefore, the oxidant side electrode 16b is less likely to be shielded by the liquid, and a sufficient effective area for chemical reaction is ensured. In addition, since the boundary side 34 is set smaller than the bottom side 36, the contact surface 20a has a sufficient area, and sufficient adhesion is ensured between the oxidant side electrode 16b and the oxidant side separator 18b. Has been. Accordingly, it is possible to prevent the fuel and the oxidant from leaking from the oxidant side flow path 24b, or the electrical conductivity between the oxidant side electrode 16b and the oxidant side separator 18b to be reduced, thereby reducing the current collection efficiency. Has been. From the above two points, the power generation efficiency of the fuel cell is improved.

  Second, the first side 38 has an inclined portion 42 that descends in the direction of gravity from the boundary side 34 toward the bottom 36. For this reason, it becomes possible to move the liquid on the inclined portion 42 from the boundary side 34 side to the bottom side 36 side by the action of gravity. That is, the liquid hardly stays or approaches in the vicinity of the oxidant side electrode 16b, and the liquid that accumulates on the base 36 side is less likely to reach the oxidant side electrode 16b. Therefore, the oxidant side electrode 16b is further prevented from being shielded by the liquid, and a sufficient effective area for chemical reaction is ensured. Therefore, the power generation efficiency of the fuel cell is further improved.

  Thirdly, the lower end 34a of the boundary 34 in the direction of gravity is above the lower end 36a of the bottom 36 in the direction of gravity when viewed in the direction of gravity. For this reason, it becomes possible to move the liquid from the lower end 34 a of the boundary side 34 to the lower end 34 a of the bottom side 36 by the action of gravity. Therefore, the second effect is increased.

  Fourth, the inclined portion 42 extends from the lower end portion 34 a of the boundary side 34. For this reason, the liquid generated at the oxidant side electrode 16b and moved to the end of the first side 38 on the boundary side 34 side does not stay at that position, but is inclined from the vicinity of the oxidant side electrode 16b by the inclined portion 42. It moves efficiently in the direction of separation.

  Fifth, the inclined portion 42 extends over the entire length of the first side 38. For this reason, when the liquid moves the inclined portion 42 from the boundary side 34 side to the bottom side 36 side, it moves efficiently to the bottom side 36 side without staying in the middle.

  3A and 3B show first and second modifications of the present embodiment. In these modifications, the cross-sectional shape of the oxidant side flow path 24b is different from that of the first embodiment. As shown in FIG. 3A, the first side 38 of the oxidant side flow path 24b of the first modification is recessed in the direction from the upper end 34b to the lower end 34a of the boundary side 34, and the tip A flat part is formed in the part. Further, as shown in FIG. 3B, the first side 38 of the second modified example is recessed like the first side 38 of the first modified example, and the tip is sharp. It has become. In these first and second modified examples, the inclined portion 42 extends from the lower end portion 34 a of the boundary side 34 to the central portion of the first side side 38. And the liquid accumulates in this center part. At this time, by making the boundary side 34 shorter than the bottom side 36, the inclination of the inclined part 42 from the central part toward the boundary side 34 becomes larger than the inclination from the central part toward the bottom side 36. There is an effect that it is difficult to approach.

  FIG. 4 shows a second embodiment of the present invention. Components having the same functions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the oxidant side flow path 24b of the present embodiment, as shown in FIG. 4, the shape of the first side 38 is different from that of the first embodiment. The first side edge 38 has a chamfered portion 46 that is substantially perpendicular to the boundary edge 34 at the end on the boundary edge 34 side. The chamfered portion 46 has such a small dimension that it does not prevent the liquid generated in the oxidant side electrode 16b from being separated from the oxidant side electrode 16b. That is, the angle θ between the boundary side 34 and the first side 38 is substantially an obtuse angle.

  The fuel cell of this embodiment has the same operational effects as those of the first embodiment. In addition, since the chamfered portion 46 is formed at the end of the first side 38 on the boundary side 34 side, the strength of this portion is increased and deformation is less likely to occur.

  FIG. 5A shows a third embodiment of the present invention. Components having the same functions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the oxidizing agent side channel 24b of the present embodiment, as shown in FIG. 5A, the shape of the second side 40 is different from that of the first embodiment. Here, the inclined portion 42 of the first side 38 is referred to as a first inclined portion 42. The second side 40 has a second inclined portion 44 similar to the first inclined portion 42 of the first side 38. That is, the second inclined portion 44 extends from the upper end 34 b of the boundary side 34 and extends linearly over the entire length of the second side 40. The direction of the second inclined portion 44 extending from the upper end portion 34b of the boundary side 34 to the upper end portion 36b of the bottom side 36 (see FIG. 5A, arrow A ′), and the upper end portion 34b of the boundary side 34 Is an obtuse angle θ ′ with the direction (see FIG. 5A, arrow B ′) extending from to the lower end 34a.

  In the present embodiment, the boundary side 34 and the bottom side 36 are arranged substantially in parallel, and the cross section is symmetric with respect to a straight line connecting the midpoint of the boundary side 34 and the midpoint of the bottom side 36. That is, θ ′ and θ are equal, and the groove width increases from the boundary side 34 toward the bottom side 36.

  Next, the operation of the fuel cell of the present embodiment having the above configuration will be described. When the fuel cell is arranged so that the direction from the upper end 34b to the lower end 34a of the boundary side 34 substantially coincides with the direction of gravity, the liquid moves on the first inclined portion 42 of the first side 38. When the fuel cell is arranged so that the direction from the lower end 34a to the upper end 34b of the boundary side 34 substantially coincides with the direction of gravity, the liquid on the second inclined portion 44 of the second side 40 is liquid. Move.

  Therefore, the configuration described above has the following effects. When using a device on which a fuel cell is mounted, for example, a portable device such as a digital camera or a mobile phone, it is assumed that the device is used upside down. In such a device, the fuel cell of this embodiment is mounted so that the direction of the boundary side 34 coincides with the vertical direction of the device. It is possible to obtain the same effect as that of the first embodiment. Further, when assembling the fuel cell itself, it may be attached upside down, so that the fuel cell can be easily assembled. Furthermore, it is not necessary to worry about the top and bottom when assembling to various devices, not limited to portable devices, and assembling to the devices becomes easy.

  FIG. 5B shows a modification of the third embodiment of the present invention. This modification is obtained by changing the side edges 38 and 40 of the first embodiment type to the side edges 38 and 40 of the second embodiment type in the third embodiment. In addition, in the third embodiment, at least one of the side edges 38 and 40 of the first embodiment type is used as the side edge 38 of the first embodiment or the first or second modification type of the first embodiment. Modifications such as changing to 40 are possible.

  Hereinafter, with reference to FIG. 6, the manufacturing method of the fuel cell of 4th Embodiment of this invention is demonstrated. The manufacturing method of the present embodiment uses a micromachine technique using a semiconductor manufacturing technique. First, a manufacturing method of the oxidant side separator 18b (see FIG. 6G) will be described.

  (Step 1) As shown in FIG. 6A, a single crystal silicon substrate 48 having a plane orientation (100) is prepared as a first member. Here, for convenience, the lower surface in the drawing is referred to as a first surface 50a, and the upper surface is referred to as a second surface 50b.

  (Step 2) As shown in FIG. 6B, a silicon nitride film 52 or the like is formed on both surfaces 50a and 50b of the silicon substrate 48 by a CVD (Chemical Vapor Deposition) method or the like (hereinafter, the silicon nitride film 52 is formed). It will be described as having been formed).

  (Step 3) As shown in FIG. 6C, in the silicon nitride film 52 formed on the second surface 50b of the silicon substrate 48, the oxidant side flow path 24b (see FIG. 6G). The silicon nitride film 52 at the position where the film is to be formed is removed by photolithography or the like.

(Step 4) As shown in FIG. 6D, the silicon substrate 48 is subjected to crystal anisotropic etching with a potassium hydroxide aqueous solution or the like.

  (Step 5) As shown in FIG. 6E, all of the silicon nitride film 52 is removed with phosphoric acid or the like. As a result, a through hole is formed in the silicon substrate 48. Since the through hole is formed by crystal anisotropic etching as described in Step 4, the opening of the second surface 50b is larger than the opening of the first surface 50a. The cross-sectional area of the cross section perpendicular to the penetrating direction monotonously changes from the opening of the second surface 50b to the opening of the first surface 50a, and here monotonously decreases.

  In the present embodiment, the through groove portion 54 is formed as a through hole. The shape of the cross section perpendicular to the longitudinal direction of the through groove 54 is the same as the shape of the cross section perpendicular to the longitudinal direction of the oxidant side flow path 24b (see FIG. 5A) of the third embodiment.

That is, the cross-section of the through groove portion 54 is defined by the first boundary side 34 defined by the first opening 56a formed in the first surface 50a and the second opening 56b formed in the second surface 50b. And a second boundary side 36 defined. Further, the cross-section of the through groove portion 54 includes a first side 38 extending from one end of the first boundary side 34 to one end of the second boundary side 36, and a second boundary from the other end of the first boundary side 34. A second side 40 extending to the other end of the side 36. The first boundary side 34, the second boundary side 36, the first side side 38, and the second side side 40 of the through groove portion 54 are the oxidant side flow of the third embodiment (see FIG. 5A). This corresponds to the boundary side 34, the bottom side 36, the first side 38 and the second side 40 of the path 24b.
(Step 6) As shown in FIG. 6F, the second glass substrate 58 or the like as the second member is anodically bonded to the second substrate 56 of the silicon substrate 48 so as to close the second opening 56b of the through groove 54. Bonded to the surface 50b (hereinafter described as the glass substrate 58 being bonded). In place of the glass substrate 58, a silicon substrate, a glass / epoxy substrate, a plastic substrate, or the like can be used. In this case, joining is performed by an adhesive or the like.

  (Step 7) As shown in FIG. 6G, a conductive film 60 is formed on the entire silicon substrate 48 and glass substrate 58 bonded to each other. For example, a metal film such as gold (Au) or nickel (Ni) is formed by plating, vapor deposition, or the like. Instead, a carbon film other than the metal film may be formed.

  Thus, the oxidant side separator 18b is manufactured. Using this oxidant side separator 18b, a fuel cell is manufactured as follows. That is, the electrolyte membrane 14 is laminated on one side surface of the oxidant side electrode 16b. And the oxidant side separator 18b is laminated | stacked on the other side of the oxidant side electrode 16b. At this time, the first surface 50a of the oxidant side separator 18b is in close contact with the other side surface of the oxidant side electrode 16b, and the first opening 56a is oxidized by the other side surface of the oxidant side electrode 16b. The agent side separator 18b is laminated. In this way, the fuel cell is manufactured.

  Therefore, the above method has the following effects. The oxidant-side separator 18b is manufactured by micromachine technology using semiconductor manufacturing technology. For this reason, it is possible to provide the oxidant side separator 18b with good shape accuracy at low cost. Furthermore, according to such a manufacturing method, a fine separator having a good shape accuracy can be manufactured at low cost, and it is possible to cope with the downsizing of the fuel cell. Moreover, since a through-hole is opened from an opening with a large cross-sectional area toward an opening with a small cross-sectional area, there is no need for a centering process, and an effect that the process is easy can be expected. This effect is particularly important in small fuel cells.

  Hereinafter, a method for manufacturing a fuel cell according to a fifth embodiment of the present invention will be described. In the present embodiment, the through groove portion 54 having the rounded first and second side edges 40 is formed. In the present embodiment, a glass substrate, a glass / epoxy substrate, or the like can be used instead of the silicon substrate 48. In the etching step, isotropic etching is performed using a mixed solution of a hydrogen fluoride aqueous solution and nitric acid, a plasma etching apparatus, or the like instead of anisotropic etching using a potassium hydroxide aqueous solution or the like. Thus, in this embodiment, the range of substrate material selection is widened.

  Hereinafter, a method for manufacturing a fuel cell according to a sixth embodiment of the present invention will be described. In the present embodiment, a metal substrate such as nickel (Ni) or titanium (Ti) is used in place of the glass substrate, glass / epoxy substrate, or the like of the fifth embodiment. In the etching process, isotropic etching is performed using an acid-based etching solution, a plasma etching apparatus, or the like. In the present embodiment, since the conductivity of the oxidant side separator 18b is improved by using the metal substrate, the power generation efficiency is improved. When the current is taken out from the metal substrate, the step 7 can be omitted, and in this case, the manufacturing process becomes easier.

  The cross-sectional shape of the oxidant side flow path 24b as described above can be applied to the cross-sectional shape of the fuel side flow path 24a. For example, when a fuel gas such as hydrogen gas is used as the fuel and Nafion is used as the electrolyte membrane 14, the fuel gas may be supplied after being humidified. In this case, some of the moisture in the fuel gas may be condensed in the fuel side flow path 24a without being used for humidifying the electrolyte membrane 14, and liquid may be generated. In such a case, by applying the cross-sectional shape of the oxidant-side flow path 24b to the cross-sectional shape of the fuel-side flow path 24a, it is possible to prevent the fuel-side electrode 16a from being shielded by the generated liquid. .

  In all the embodiments and modifications described above, the case where there is one cell body 12 has been described. However, the present invention provides a desired electromotive force by stacking a plurality of cell bodies 12 and electrically connecting them in series. It is possible to apply to the obtained stack type fuel cell. In this case, for the separator disposed between the fuel side electrode 16a and the oxidant side electrode 16b, the fuel side groove portion 22a is formed on one side surface that is in close contact with the fuel side electrode 16a, and the oxidant side It is preferable to form an oxidant side groove 22b on the other side that is in close contact with the electrode 16b.

  The present invention relates to a separator that can improve power generation efficiency of a fuel cell, and is disposed so as to be in close contact with one side surface of an electrode on a membrane electrode structure in which the electrode is disposed on one side surface of an electrolyte membrane. And a fuel cell having such a separator.

(A) is a side view which shows the cell body periphery of the fuel cell of 1st Embodiment of this invention, (B) is an exploded view which shows the cell body of the embodiment. Sectional drawing which cuts and shows the oxidizing agent side flow path of the fuel cell of 1st Embodiment of this invention along the II-II line of FIG. 1 (B). (A) is a figure which shows the cross section of the oxidizing agent side flow path of the fuel cell of the 1st modification of 1st Embodiment of this invention, (B) is the oxidation of the fuel cell of the 2nd modification of the embodiment. The figure which shows the cross section of an agent side flow path. The figure which shows the cross section of the oxidizing agent side flow path of the fuel cell of 2nd Embodiment of this invention. (A) is a figure which shows the cross section of the oxidizing agent side flow path of the fuel cell of 3rd Embodiment of this invention, (B) is the cross section of the oxidizing agent side flow path of the fuel cell of the modification of the embodiment. FIG. (A) is sectional drawing which shows the process of preparing the 1st member of the manufacturing method of the oxidizing agent side separator in the manufacturing method of the fuel cell of 4th Embodiment of this invention, (B) is the 1st member. (C) is a cross-sectional view showing a step of removing a part of the film, (D) is a cross-sectional view showing a step of etching, and (E) is a cross-sectional view showing a step of forming a film on both sides of the film. Sectional drawing which shows the process of removing all, (F) is sectional drawing which shows the process of joining a 2nd member, (G) is sectional drawing which shows the process of forming into a film the 1st and 2nd member. Sectional drawing which shows the cell body of the fuel cell of a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 14 ... Electrolyte membrane, 16a, 16b ... Electrode, 17 ... Membrane electrode structure, 18a, 18b ... Separator, 20a, 20b ... Close contact surface, 22a, 22b ... Groove part, 34 ... Boundary side, 36 ... Bottom side, 38, 40 ... Sides, 42, 44 ... inclined portions.

Claims (20)

A fuel cell comprising an electrolyte membrane, an electrode, and a separator having a groove formed on a close contact surface that is in close contact with one side surface of the electrode, and through which an active material flows.
In the cross section perpendicular to the flow direction of the active material in the groove portion, the boundary side corresponding to the contact surface is shorter in the cross section than the bottom side corresponding to the bottom of the groove portion.   The side that connects the lower end in the gravitational direction of the boundary side to the lower end in the gravitational direction of the bottom side includes an inclined portion that falls in the gravitational direction from the boundary side toward the base side. 2. The fuel cell according to 1.   The fuel cell according to claim 2, wherein the inclined portion extends from one end of the boundary side.   The fuel cell according to claim 2, wherein the inclined portion is provided over the entire length of the side.   2. The fuel cell according to claim 1, wherein a lower end of the boundary side in the gravitational direction is above the lower end of the bottom side in the gravitational direction as viewed in the gravitational direction.   The side edge connecting the upper edge of the boundary edge in the gravity direction and the upper edge of the bottom edge in the gravity direction, and the side edge connecting the lower edge of the boundary edge in the gravity direction and the lower edge of the bottom edge in the gravity direction and the boundary edge are stretched. The fuel cell according to claim 1, wherein each of the corners is an obtuse angle.   The fuel cell according to claim 6, wherein the cross section is symmetric with respect to a straight line connecting a midpoint of the boundary side and a midpoint of the bottom side.   The fuel cell according to claim 1, wherein the fuel cell is configured using a member processed by crystal anisotropic etching.   The fuel cell according to claim 1, wherein the fuel cell is configured using a member processed by isotropic etching. A separator provided with a membrane electrode structure comprising an electrolyte membrane and an electrode so as to be in contact with the electrode, and an active material flow groove in which an active material for power generation by a fuel cell flows while in contact with the membrane electrode structure A manufacturing method of
The first member constituting a part of the separator penetrates the first member so as to connect a plurality of openings provided on the first member, and is perpendicular to the direction penetrating the member. A step of opening a through-hole in which a cross-sectional area of a simple cross section monotonously changes from one of the plurality of openings toward the other opening;
Joining a second member constituting a part of the separator to the first member so as to close a larger one of the plurality of openings;
A method for producing a separator, comprising:   The method for manufacturing a separator according to claim 10, wherein the plurality of openings are provided on different surfaces of the first member.   The method for manufacturing a separator according to claim 10, wherein the plurality of openings have different sizes.   The method for manufacturing a separator according to claim 10, wherein an angle formed by a surface corresponding to the opening that contacts the membrane electrode structure and an inner wall of the through hole is an obtuse angle.   11. The method for manufacturing a separator according to claim 10, wherein the groove width of the active material flow groove is always increased or decreased from one of the plurality of openings toward the other opening.   The method for manufacturing a separator according to claim 10, wherein the through hole is formed from a larger one of the plurality of openings.   The cross section of the active material flow groove in a direction perpendicular to the flow direction of the active material flowing in the active material flow groove is symmetric in the width direction of the active material flow groove. Separator manufacturing method.   The method for manufacturing a separator according to claim 10, wherein the step of opening the through hole includes a step of performing crystal anisotropic etching.   The method for manufacturing a separator according to claim 10, wherein the step of opening the through hole includes a step of performing isotropic etching. A separator having an active material flow groove laminated on a membrane electrode structure composed of an electrolyte membrane and an electrode so that the active material for generating power by the fuel cell flows while in contact with the membrane electrode structure. There,
The separator is composed of a first member and a second member,
The first member penetrates the first member so as to connect a plurality of openings provided on the first member, and has a cross section perpendicular to the direction penetrating the first member. The area has a through hole that monotonously changes from one of the plurality of openings toward the other opening,
The separator, wherein the second member is joined to the first member so as to close a larger one of the plurality of openings.   A fuel cell incorporating the separator according to claim 19.

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