JP2005251740A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact fuel cell using liquid fuel as direct fuel, having high output voltage and high performance, easy to manufacture. <P>SOLUTION: The fuel cell is provided with sheets 105 composed of first conductive films 101 constituting a fuel electrode supplied with liquid fuel, a second conductive film 103 constituting an air electrode supplied with air, and electrolyte films 102 laid between the first conductive films 101 and the second film 103. The sheets 105 are so structured to be folded up according to a first fold so that both of either the first conductive films 101 or the second conductive films 103 are opposed to each other, and further, folded according to a plurality of second folds crossing the first fold alternately backward and frontward. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell using liquid fuel as a fuel, and more particularly to a small fuel cell that can be mounted on a mobile device or the like.

  In recent years, power consumption of mobile devices and the like has increased year by year as functions are increased, and a power source having a high energy density is required. For this reason, the development of fuel cells that use liquid fuels such as methanol directly as fuel has attracted considerable attention. A fuel cell using liquid fuel as a direct fuel can be expected to have an energy density of one digit or more as compared with a secondary battery such as a current lithium ion battery (for example, see Non-Patent Documents 1 and 2).

As a liquid fuel used as a direct fuel, a methanol aqueous solution (CH ₃ OH / H ₂ O solution) is often used. In a fuel cell using methanol as a direct fuel, when a methanol aqueous solution as a fuel is supplied to the fuel electrode, a reaction of CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ occurs at the fuel electrode, and the air electrode In the electrode, a reaction of 3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O occurs.
In this series of reactions, an endotherm of 130.97 kJ is generated at the fuel electrode and a heat of 857.52 kJ is generated at the air electrode per mole of methanol. Further, the reaction of this fuel cell becomes active when the temperature of the cell portion is high, and a high output can be obtained (for example, see Non-Patent Document 3).

  On the other hand, in a conventional fuel cell, a flat type cell is often used. However, the flat cell has a problem that the voltage that can be output by a single cell is as low as about 0.3V to 0.7V. For example, if the output voltage is low, the fuel cell alone cannot supply a voltage suitable for the power supply voltage of an electronic circuit having a load of about 1 to 5 V, and a boost DC-DC converter or the like is required. Become. In addition, when a constant current is supplied at a low voltage, the supplied current becomes larger in a fuel cell using a flat plate cell, and the resistance parasitic in series with the output of the fuel cell results in a loss of resistance × current squared As a result, there is a problem that energy efficiency is lowered.

Furthermore, when trying to connect flat cells in series to increase the output voltage, it is necessary to connect the cells one by one, so that the size of the fuel cell becomes too large, or the alignment of a plurality of cells, etc. There is also a problem that the manufacturing process increases and the manufacturing efficiency decreases.
C. Hebling et al., `` Technology and Markets of Portable Fuel Cells, '' Proceedings of 7th Grove Fuel Cell Symposium, London, O7.1, 2001.9 “Nikkei Electronics”, Nikkei BP, October 22, 2001, p. 117 M. Baldauf, "Status of the development of a direct methanol fuel cell," Journal of Power Sources, vol.84.p.161-166, 1999

  An object of the present invention is to provide a fuel cell that uses liquid fuel as a direct fuel, is compact, has high output voltage, has high performance, and is easy to manufacture.

  In order to solve the above object, a fuel cell of the present invention includes a first conductive film constituting a fuel electrode to which liquid fuel is supplied and a second conductive film constituting an air electrode to which air is supplied. A fuel cell comprising a sheet comprising a conductive film, and an electrolyte film sandwiched between the first conductive film and the second conductive film, wherein the sheet comprises the first film A plurality of second folds are folded according to the first fold so that one of the conductive film and the second conductive film is opposed to each other, and is further orthogonal to the first fold. According to the above, the front and back are folded alternately.

  The fuel cell of the present invention uses a sheet having a three-layer structure in which a first conductive film, an electrolyte film, and a second conductive film are laminated in this order as a cell, and the cell is made compact by folding the sheet. Can be configured. As described above, since the fuel cell of the present invention has a compact cell structure, the first conductive film and the second conductive film are divided as described later, or a plurality of sheet-like cells are connected in series. By connecting, the output voltage can be easily increased. Since the fuel cell of the present invention can be formed with a smaller surface area compared with the volume of the battery cell, the temperature is maintained at a high temperature without releasing the heat generated by the reaction in the second conductive film. can do. In the present invention, when the sheet is folded according to the first fold, the first electrode is folded so that the first conductive film is in close contact, and the fuel electrode is formed inside the sheet. It is preferable. Note that the second fold line does not have to be completely orthogonal to the first fold line, and may be substantially orthogonal.

  The fuel cell of the present invention can be configured such that the first conductive film and the second conductive film are divided according to at least one of the first fold and the second fold. According to the fuel cell of the present invention, the first and second conductive films are divided according to at least one of the first and second folds, preferably the second fold, that is, a portion that can become the second fold. By configuring the fuel cell of the present invention using the sheet having the first and second conductive films arranged so as to be divided in FIG. 1, a fuel cell having a plurality of cells can be obtained. Thereby, since each cell part can be connected in series with small internal resistance, the output voltage of a fuel cell can be raised. Moreover, since the fuel cell of this invention can form a some cell with one sheet | seat, each conductive film of these cells can be connected with metal foil, and each cell is connected. Productivity is high without the need for wiring or the like. In the fuel cell of the present invention, when the first and second conductive films are divided and configured on the sheet, the conductive film can be formed in the same size, and it is necessary to use different sheets. Therefore, it is not necessary to bond each cell, and it is not necessary to align the positions, so that productivity can be further improved.

  In addition, the fuel cell of the present invention is preferably configured by sandwiching an insulator for each second fold of the sheet. Thereby, especially when the first and second conductive films are divided, a plurality of cells can be formed independently. Further, by using a porous insulator, or providing a gap in the insulator, air can be supplied smoothly to the conductive film, and the output can be improved.

  Furthermore, in the fuel cell of the present invention, the first conductive film and the second conductive film facing each other through the insulator can be connected by a conductor. Thereby, a some cell can be connected in series and the output voltage of a fuel cell can be raised. In addition, metal foil etc. can be used suitably as said conductor. Thus, by connecting a plurality of cells configured on one sheet with a metal foil, a fuel cell having a multi-cell structure in a compact manner without the need for wiring or the like for connecting each cell portion Can be manufactured.

  The fuel cell of the present invention can supply air to the second conductive film via the insulator. The fuel cell according to the present invention can smoothly supply air to the second conductive film by supplying air to the second conductive film via the insulator, thereby improving the output. Can be made. In order to supply air to the second conductive film via an insulator, as described above, a porous material or a material provided with a gap can be used as the insulator.

The fuel cell of the present invention can be configured such that the sheet has a through hole. According to the fuel cell of the present invention, by having a through-hole penetrating the sheet from one side (for example, the first conductive film side) to the other side (second conductive film side), for example, When the sheet is folded according to the first fold so that the first conductive film is in close contact (so that the first conductive film is on the inside), the fuel electrode passes through the through hole. Carbon dioxide (CO ₂ ) and the like generated at the electrode can be easily discharged from the folded inner side of the sheet toward the outer side. If the carbon dioxide can be discharged in this way, the generated carbon dioxide does not stay on the catalyst, so that the reaction is not inhibited and the output can be prevented from being reduced.

  In the fuel cell of the present invention, an aqueous methanol solution can be used as the liquid fuel. According to the fuel cell of the present invention, electric power can be efficiently generated by using a methanol aqueous solution as a direct fuel. Further, from the viewpoint of preventing crossover of methanol passing through the electrolyte membrane and reaching the air electrode, the concentration of the methanol solution is preferably about 3% by mass. However, the liquid fuel used in the fuel cell of the present invention is not limited to a methanol aqueous solution.

  According to the present invention, a fuel cell using liquid fuel as a direct fuel can be provided with a compact, high output voltage, high performance and easy to manufacture.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a main configuration of a fuel cell according to an embodiment of the present invention, and FIG. 2 is a bottom view of FIG. 1 and 2, the fuel cell 100 includes a first conductive film 101 that is supplied with hydrogen gas to form a fuel electrode, an electrolyte film 102 that has proton conductivity, and an air electrode that is supplied with air. A sheet 105 having a laminated structure in which the electrolyte film 102 is sandwiched between the first conductive film 101 and the second conductive film 102 as a cell. ing.

Further, as shown in FIG. 2, an insulating film 104 is interposed between adjacent second conductive films 103, and each cell portion is divided. Further, as shown in FIGS. 1 and 2, the fuel cell 100 of the present invention is provided with a plurality of through holes 106 penetrating from the inside of the folded sheet 105 to the outside, and the first conductive film. CO ₂ generated at 101 (fuel electrode) is configured to be discharged from the inside of the sheet 105 to the outside through the through hole 106.

  As shown in FIG. 2, the fuel cell 100 is arranged such that the first conductive film 101 faces each other, that is, the first conductive film 101A and the first conductive film 101B, or the first conductive film. The folded sheet 105 is alternately folded so that 101C and the first conductive film 101D face each other to form a cell portion. The first conductive film 101B and the second conductive film 103C, and the first conductive film 101D and the second conductive film 103E are opposed to each other with the insulating film 104 therebetween, such as the first conductive film 101B and the second conductive film 103C. The film and the second conductive film are connected by a metal foil 107A or B. At this time, for example, the end of the metal foil 107A has one end between the first conductive film 101A and the first conductive film 101B, and the other end between the insulating film 104 and the second conductive film 103C. It is sandwiched between them.

  The sheet 105 will be described with reference to FIG. FIG. 3 is a schematic view of a main part for explaining a sheet in the present invention. In FIG. 3, the sheet 105 has a plurality of second conductive films 103 formed on one surface of the electrolyte film 102, and further the first conductive film 101 on the other surface (back surface). Is formed. In the present invention, the sheet 105 is folded in the direction of the arrow a with the dotted line A in FIG. 3 as the fold line (first fold line). At this time, the side on which the first conductive film is provided is the inside of the folded sheet 105. Further, the sheet 105 according to the present invention is configured such that the dotted lines B and C orthogonal to the dotted line A are folded (second folds) and folded back and forth in the directions of arrows b and c.

Next, a method for producing the fuel cell of the present invention will be described.
As shown in FIG. 3, a strip-shaped second conductive film 103 is affixed on the electrolyte membrane 102 at a predetermined interval by a thermocompression bonding method or the like. Further, a strip-like insulating film 104 is attached on the surface of the second conductive film 103 and the surface of the electrolyte film 102 in a direction perpendicular to the length direction of the second conductive film 103, Through-holes 106 are provided with an interval of. Further, a metal foil 107 is attached to the surface of the first conductive film 101 so as to cover a part of the first conductive film 101 and to be exposed to the outside of the first conductive film 101.

  As shown in FIG. 4, which is a cross-sectional view taken along line 1a-1b of FIG. The first conductive film 101 is pasted by a thermocompression bonding method or the like at a predetermined interval in a portion excluding (). Further, as described above, the metal foil 107 is provided so as to cover a part of the first conductive film 101 and to be exposed to the outside of the first conductive film 101.

  Next, the sheet 105 having the four-layer structure shown in FIG. 4 is folded in the direction indicated by the arrow a along the line indicated by the broken line (same as the dotted line A in FIG. 3; the first fold) in FIG. The sheet 105 is folded as shown. At this time, the metal foil 107 is folded back so as to sandwich the insulating film 104 in the direction indicated by the arrow d in FIG. Next, from the state shown in FIG. 5, the sheet 105 is penetrated by alternately folding the front and back sides as shown in FIG. 6 with the dotted lines B and C perpendicular to the dotted line A in FIG. 3 as folds (second folds). A sheet 105 used in the fuel cell 100 of the present invention provided with the holes 106 can be formed. At this time, a plurality of rectangular cells formed by bending the sheet 105 (for example, the cells 201A and 201B in FIG. 2) are formed of one first conductive film and the other second conductive by the metal foil 107. The membrane is connected. Further, as shown in FIG. 7, when the fuel cell of the present invention is manufactured by folding the sheet 105 as described above, the insulating film 104 is sandwiched between the second folds in the dotted lines B and C. The

  Therefore, the second conductive film 103 (202A portion) and the metal foil 107 (202B portion) shown in FIG. 3 are joined to each other when the sheet is folded in two and the sheet is wound. 1 to 3 show only the main part of the sheet surface, the electrolyte membrane 102 forms a continuous sheet on the right side of the drawing, and the length direction of the sheet-like electrolyte membrane 102 is shown in FIG. In addition, the first conductive film 101 and the second conductive film 103 are sequentially attached to the respective surfaces at predetermined intervals. The width of the first conductive film 101 and the width of the second conductive film 103 correspond to the lengths of the long side and the short side of the rectangular shape constituting each cell shown in FIG. Set to do.

Next, the material forming the fuel cell of the present invention will be described.
In the present invention, the first conductive film 101 plays a role of releasing hydrogen ions and electrons from methanol supplied by capillary action. The first conductive film 101 carries a catalyst to be a fuel electrode and has a spongy structure. As said catalyst, the well-known catalyst used for reaction which discharge | releases a hydrogen ion and an electron from methanol and water can be selected suitably, and can be used. As the catalyst, for example, Pt, Pt—Ru alloy or the like can be used. The first conductive film 101 can be formed, for example, by mixing a catalyst supported on a sponge material, a polymer film solution used for the electrolyte film 102, and a binder. Accordingly, since the conductive film 101 and the electrolyte film 102 are integrated in advance, manufacturing steps such as alignment and bonding can be omitted.

  The electrolyte membrane 102 is a membrane that allows only hydrogen ions among the electrons and hydrogen ions generated in the first conductive film 101 to pass therethrough, and may be composed of, for example, a polymer membrane such as a perfluorosulfonic acid membrane. it can. Commercially available products such as Nafion membrane (trade name of DuPont), Flemion membrane (trade name of Asahi Glass Co., Ltd.), and Aciplex membrane (trade name of Asahi Glass Co., Ltd.) can be suitably used as the solid polymer membrane. .

  Air containing oxygen is supplied to the second conductive film 103, and the second conductive film 103 carries a catalyst to be an air electrode, and is similar to the first conductive film 101 in the sponge. It can be formed of a member having a shape structure. As said catalyst, the well-known catalyst used for the reaction which produces | generates water from oxygen, a water ion, and an electron can be selected suitably, and can be used. Specifically, for example, Pt or the like can be used as the catalyst. In addition, the above-described sponge-like material can be used for the second conductive film 103, and a catalyst supported on the material, a polymer film solution used for the electrolyte film 102, a binder, and the like are mixed. Can be formed. Thereby, since the conductive film 103 and the electrolyte film 102 are integrated in advance, it is possible to eliminate manufacturing steps such as alignment and bonding.

  The sponge-like material used for the conductive film 101 and the conductive film 103 is formed using a porous carbon sheet, a porous plastic sheet, glass wool, or the like. From the viewpoint of conductivity, a porous carbon sheet is used. It is desirable to use it. In the conductive film 101, by keeping methanol in the porous structure of the spongy material for a certain period of time, heat generated from the battery cell can be sufficiently transmitted to the methanol, and the catalyst is activated by increasing the heating efficiency of methanol. Thus, the cell output can be improved.

  As the insulating film 104, an insulating material such as plastic, glass, rubber, or the like can be selected as appropriate. In particular, a material that can be easily made porous to allow air to pass therethrough, such as plastic, or that can leave a gap is preferable.

In the present invention, the number and size of the through holes 106 are not particularly limited as long as they do not impair the CO ₂ emission effect. Similarly, the position at which the through hole 106 is provided is not particularly limited. From the viewpoint of efficiently discharging CO ₂ generated inside the sheet 105 (on the fuel electrode side) to the outside of the sheet 105, FIG. As shown in FIG. 7 and the like, the through hole 106 is preferably provided in the vicinity of a point where the first fold line and the second fold line are orthogonal.

  As the metal foil 107, nickel alloy, stainless steel, aluminum or the like can be suitably used, and stainless steel is particularly preferable from the viewpoint of corrosion resistance. Further, the contact resistance can be reduced by applying gold plating to the stainless steel surface.

Next, the power generation mechanism of the fuel cell of the present invention will be described.
A power generation mechanism using the fuel cell of the present invention will be described with reference to FIG. 8 is a cross-sectional view taken along line 3a-3a ′ in FIG. When methanol supplied from a fuel tank (not shown) is supplied to the entire first conductive film 101 by capillary action, the methanol comes into contact with the catalyst in the conductive film 101, and hydrogen ions, electrons, CO ₂ , Release. At this time, since CO ₂ passes through the through-hole 106 and is discharged to the outside of the fuel cell, the reaction on the catalyst is not hindered, and a decrease in output can be prevented. . Further, the fuel cell 100 is heated by heat generated from the second conductive film 103. For this reason, the temperature of the battery cell can be maintained at a relatively high temperature without lowering the temperature of the battery cell by supplying methanol. Therefore, the catalyst is activated and the output becomes high.

  Hydrogen ions released from the first conductive film 101 pass through the electrolyte film 102 and reach the second conductive film 103, and react with oxygen to generate water. At this time, air (oxygen) in the second conductive film 103 can be supplied through the insulating film 104 by providing the insulating film 104 with a porous structure and supplying air to the insulating film 104. On the other hand, electrons emitted from the first conductive film 101 move to the second conductive film 103 of the adjacent cell through the insulating film 104 through the metal foil 107. At this time, since all the conductive films and the electrolyte film are one sheet, it is not necessary to bond and align with adjacent cells, and the number of manufacturing steps can be reduced. By this movement of electrons, the fuel cell of the present invention can supply power to an external device (not shown).

Note that the CO ₂ produced by the first conductive film 101 and the water produced by the second conductive film 103 are discharged to the outside of the fuel cell.

According to the fuel cell of the present embodiment, the fuel electrode and the air electrode are divided, the electrolyte membrane is provided with a through hole, and the sheet in which the electrode portion is divided is folded with the fuel station electrode inside. , By bending the other end of the metal foil sandwiched between the fuel electrode and the other end alternately between the air electrode and the insulating film, the size of each cell is uniform, connected in series, and CO ₂ generated at the fuel electrode can be easily discharged to the outside of the fuel cell. Thereby, a fuel cell with high output voltage and high productivity can be obtained.

It is a perspective view which shows roughly the principal part structure of the fuel cell of this invention. It is a principal part bottom view of the fuel cell of this invention. It is a principal part schematic diagram for demonstrating the sheet | seat in this invention. It is sectional drawing which follows the 1a-1b line | wire of FIG. It is the schematic for demonstrating the form of the sheet | seat in this invention. It is another schematic diagram for demonstrating the form of the sheet | seat in this invention. It is a perspective view for demonstrating the form of the fuel cell of this invention. FIG. 3 is a cross-sectional view taken along line 3a-3a ′ of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Fuel cell 101 1st electroconductive film 102 Electrolyte film 103 2nd electroconductive film 104 Insulating film 105 Sheet 106 Through-hole 107 Metal foil

Claims (7)

A first conductive film constituting a fuel electrode supplied with liquid fuel; a second conductive film constituting an air electrode supplied with air; the first conductive film; and the second conductive film. An electrolyte membrane sandwiched between the conductive membrane, and a fuel cell comprising a sheet composed of:
The sheet is folded according to a first fold so that any one of the first conductive film and the second conductive film is opposed to each other, and the first fold and A fuel cell that is alternately folded according to a plurality of orthogonal second folds.   2. The fuel cell according to claim 1, wherein the first conductive film and the second conductive film are divided according to at least one of the first fold and the second fold.   The fuel cell according to claim 1 or 2, wherein an insulator is sandwiched for each second fold of the sheet.   The fuel cell according to claim 3, wherein the first conductive film and the second conductive film facing each other through the insulator are connected by a conductor.   The fuel cell according to claim 3 or 4, wherein air is supplied to the second conductive film via the insulator.   The fuel cell according to claim 1, wherein the sheet has a through hole. The fuel cell according to any one of claims 1 to 6, wherein the liquid fuel is an aqueous methanol solution.

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