Patent Publication Number: US-2012040257-A1

Title: Fuel Container For Fuel Cell, Fuel Cell Using The Same, And Operation Method Of Fuel Cell

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel container for fuel cell, a fuel cell using the same, and an operation method of fuel cell. 
     BACKGROUND ART 
     A solid electrolyte fuel cell is constituted by a fuel electrode, an oxidant electrode, and a solid electrolyte membrane provided between the fuel electrode and the oxidant electrode, and performs power generation according to the electrochemical reaction caused by supplying fuel to the fuel electrode and by supplying an oxidizing agent to the oxidant electrode. The fuel electrode and the oxidant electrode include a base material and a catalyst layer which is formed on the surface of the base material. In the fuel cell, hydrogen is generally used as a fuel, but a methanol reforming type fuel cell in which inexpensive and easily-handling methanol is used as a raw material so as to generate hydrogen by reforming the methanol, and a direct type fuel cell in which methanol is used directly as a fuel, has been energetically developed. 
     When methanol is used as a fuel, the reaction in the fuel electrode is expressed by the following formula (1). 
       CH 3 OH+H 2 O→6H + +CO 2 +6 e   −   (1)
 
     Further, the reaction in the oxidant electrode is expressed by the following formula (2). 
       3/2O 2 +6H + +6 e   − →3H 2 O  (2)
 
     In this way, in the direct type fuel cell, it is possible to obtain hydrogen ions from a methanol aqueous solution, to make it possible to eliminate a reforming device and the like, and to thereby attain size reduction and weight reduction of the fuel cell. Further, since a liquid methanol aqueous solution is used as fuel, it has a characteristic that the energy density is very high. 
     In Patent Document 1, there is disclosed a technique in which a liquid fuel is supplied to an external fuel cell from a liquid fuel container storing the liquid fuel. In the fuel cell disclosed in Patent Document 1, the liquid fuel stored in the liquid fuel container is supplied to the main body from an introduction pipe, and is vaporized in a vaporizing section of the main body, to be introduced into a fuel electrode. 
     However, this fuel cell is constituted such that the liquid fuel in the liquid fuel container is vaporized in the vaporizing section provided before the fuel electrode in the main body, to be introduced into the fuel electrode. For this reason, there is a problem to be improved in adjusting the fuel supplied to the fuel electrode to a predetermined concentration. 
     On the other hand, in Patent Document 2, there is disclosed a fuel cell which has a high concentration methanol tank in addition to a fuel tank storing a liquid fuel to be supplied to a unit cell. However, in this case, it is necessary to supply a high concentration methanol stored in the high concentration methanol tank to the fuel tank by a pump, to adjust the liquid fuel supplied to the unit cell to a predetermined concentration. This causes the apparatus constitution to become large-sized and complicated.
     Patent Document 1: Japanese Patent Application Laid-Open No. 2001-93551.   Patent Document 2: Japanese Patent Application Laid-Open No. 2003-132924.   

     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     The present invention has been made in view of the above described circumstances, and an object of the present invention is to provide a technique which makes it possible to downsize a fuel cell and to stably supply a fuel to a fuel electrode. 
     Means for Solving Problem 
     According to the present invention, there is provided a fuel container for fuel cell in which a solid or liquid fuel is placed, comprising a fuel gas supply port for supplying vapor of the fuel stored in the container to a liquid fuel supply system of the fuel cell. 
     The fuel container for fuel cell according to the present invention comprises the fuel gas supply port. The fuel supply to the fuel electrode of the fuel cell is performed by the liquid fuel supply system. For this reason, the vapor of the fuel stored in the container can be dissolved in the liquid fuel supply system of the fuel cell, and surely supplied to the fuel electrode. When the fuel component concentration of the liquid fuel stored in the liquid fuel supply system is lowered due to the use of the fuel cell, it is possible to supply the fuel, and to thereby stabilize the fuel concentration in the liquid fuel supply system. Further, the supply is performed after dissolving the vapor of fuel into the liquid fuel, so that the fuel can be stably supplied without using an auxiliary apparatus such as a pump for supplying the fuel component to the liquid fuel supply system. For this reason, by the use of the fuel container for fuel cell according to the present invention, it is possible to stably operate the liquid fuel supply type fuel cell with simple constitution. 
     According to the present invention, there is provided a fuel container for fuel cell, comprising: a fuel placing section in which a solid or liquid fuel is placed; a vaporizing section communicated with the fuel placing section in which the fuel is vaporized; and a fuel gas supply port supplying a vaporized fuel vaporized in the vaporizing section to a liquid fuel supply system of the fuel cell. 
     The fuel container for fuel cell according to the present invention has the fuel placing section and the vaporizing section. This makes it possible to place a high concentration liquid or solid fuel in the fuel placing section, and it is vaporized in the vaporizing section so as to be supplied to the liquid fuel supply system. As a result, it is possible to preferably suppress the lowering of the fuel concentration in the liquid fuel supply system of the fuel cell with simple constitution. 
     The fuel container for fuel cell according to the present invention can be constituted such that a gas liquid separating section is provided on the fuel gas supply port. This enables the fuel vaporized in the container to be selectively supplied to the liquid fuel supply system of the fuel cell. In the present invention, the gas liquid separating section can be constituted to have, for example, a gas liquid separating film. 
     The fuel container for fuel cell according to the present invention can be constituted to comprise: a fuel storage chamber in which a solid or fluid fuel is placed; and a vaporizing chamber storing vapor of the fuel vaporized in the fuel storage chamber. By providing the fuel storage chamber and the vaporizing chamber, the solid or liquid fuel can be more surely held in the fuel container, and vaporized so as to be stably supplied to the liquid fuel supply system of the fuel cell. 
     In the fuel container for fuel cell according to the present invention, the fuel storage chamber and the vaporizing chamber may be partitioned by a gas liquid separating film. This makes it possible to selectively place the vaporized fuel in the vaporizing chamber. As a result, it is possible to make the vaporized fuel more surely supplied to the liquid fuel supply system. 
     In the fuel container for fuel cell according to the present invention, the fuel may be a solidified material of organic liquid fuel. This makes it possible to suppress the leakage of the fuel component to the outside of the container, even in the case where the fuel component is contained at a high concentration. As a result, it is possible to improve the safety when the fuel container for fuel cell is used. Further, it is possible to make the fuel container downsized as compared with the case where a dilute liquid fuel is stored in the fuel container. 
     The fuel container for fuel cell according to the present invention may be a fuel cartridge for fuel cell which is detachably provided to the fuel cell. The fuel container for fuel cell according to the present invention is small in size and capable of supplying the fuel with excellent controllability. Thus, by using this fuel container as a portable fuel cartridge for fuel cell, it can be preferably used for a fuel cell and the like which is applied to a portable electric appliance. 
     According to the present invention, there is provided a fuel cell, comprising: a fuel electrode; a liquid fuel supply system supplying a liquid fuel to the fuel electrode; and a vaporized fuel supply section supplying a vaporized fuel to the liquid fuel supply system; wherein a gas liquid separating section selectively transferring the vaporized fuel is provided between the liquid fuel supply system and the vaporized fuel supply section. 
     Further, according to the present invention, there is provided a fuel cell, comprising: a fuel electrode; a liquid fuel supply system supplying a liquid fuel to the fuel electrode; and the above described fuel container for fuel cell; wherein a gas liquid separating section selectively transferring vapor of the fuel to the liquid fuel supply system is provided between the fuel container for fuel cell and the liquid fuel supply system. 
     The fuel cell according to the present invention has the vaporized fuel supply section which supplies vaporized fuel to the liquid fuel supply system which supplies a liquid fuel to the fuel electrode. Further, the fuel cell according to the present invention comprises the fuel cell container for fuel cell, and is constituted so as to make vapor of the fuel in the container supplied to the liquid fuel supply system via the gas liquid separating section. This makes it possible to suppress the lowering of the fuel concentration in the liquid fuel supply system. Further, in the fuel cell according to the present invention, the vaporized fuel is made to pass through the gas liquid separating section so as to be once dissolved in the liquid fuel, and then supplied to the fuel electrode, without being directly supplied to the fuel electrode. Thus, the concentration of the fuel component supplied to the fuel electrode can be stabilized. This eliminates the need for providing auxiliary apparatuses such as a pump for supplying the fuel or an auxiliary power supply for stabilizing the output of the fuel cell. As a result, it is possible to make the fuel cell as a whole downsized and simplified. 
     The fuel container for fuel cell according to the present invention can be constituted such that an openable and closable shutter member is provided to the fuel gas supply port. Further, the fuel cell according to the present invention can be constituted to comprise a shutter member by which the supply of the vaporized fuel to the liquid fuel supply system starts and stops. This make it possible adjust the supply of the vaporized fuel to the liquid fuel supply system by opening and closing the shutter member according to the use state of the fuel cell. As a result, it is possible to perform the supply of the vaporized fuel to the liquid fuel supply system with more excellent controllability. 
     In the fuel cell according to the present invention, the liquid fuel supply system may be constituted to comprise a fuel cartridge in which liquid fuel supplied to the fuel electrode is stored, and a fuel collecting section collecting a liquid discharged from the fuel electrode or the oxidant electrode; and wherein the fuel container for fuel cell may be constituted to supply vapor of the fuel to a liquid fuel mixing tank communicated with the fuel cartridge and with the fuel collecting section. With the constitution in which the fuel vapor of the fuel is supplied to the liquid fuel mixing tank, it is possible to suppress the lowering of the concentration of the liquid fuel stored in the mixing tank. Thus, it is possible to stabilize the concentration of the liquid fuel supplied to the fuel electrode, even in the fuel cell having a fuel circulation path, through which the liquid that has passed through the fuel electrode or the oxidant electrode is collected to the mixing tank so as to be supplied to the fuel electrode once more. 
     According to the present invention, there is provided an operation method of fuel cell having a fuel electrode, a liquid fuel supply system supplying a liquid fuel to the fuel electrode: wherein the fuel cell is operated while supplying a vaporized fuel having a higher concentration than the concentration of the liquid fuel supplied to the fuel electrode. 
     In the present invention, the fuel cell is operated while the vaporized fuel having a higher concentration than the concentration of the liquid fuel supplied to the fuel electrode is supplied, so that the fuel used during the operation can be dissolved into the liquid fuel as the vaporized fuel and supplied. This makes it possible to stably supply the fuel to the fuel electrode by a simple method. As a result, it is possible to stably operate the fuel cell for a long period of time. 
     In the operation method of fuel cell, according to the present invention, the fuel cell can be operated by circulating the liquid fuel, while collecting a residual fuel having passed through the fuel electrode or water generated on an oxidant electrode. Even when the fuel cell is operated by circulating the liquid fuel while collecting the residual fuel or water, it is possible to stabilize the fuel supply to the fuel electrode by operating the fuel cell while supplying the vaporized fuel. 
     Note that any arbitrary combination of each of these kinds of constitution, and any modification between the method and the apparatus stated in the present invention, is also effective as an embodiment of the present invention. 
     Effect of the Invention 
     As described above, according to the present invention, by supplying a vaporized fuel to a liquid fuel supply system of a fuel cell, it is possible to realize a technique which enables the fuel cell to be downsized and the fuel to be stably supplied to a fuel electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 2  is a top view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 3  is a view showing  FIG. 2  from the line A-A′ direction; 
         FIG. 4  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 5  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 6  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 7  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 8  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 9  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 10  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 11  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 12  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 13  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 14  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 15  is a figure to explain a measuring method of a diffusion rate of methanol gas according to Examples; 
         FIG. 16  is a graph showing a relationship between elapsed time of a fuel container and fuel concentration according to examples; 
         FIG. 17  is a graph showing a relationship between fuel concentration in the fuel container and diffusion rate according to examples; 
         FIG. 18  is a cross-sectional view schematically showing a constitution of a fuel cell according to the present embodiment; 
         FIG. 19  is a graph showing a relationship between power generation time and voltage of the fuel cell according to the example; 
         FIG. 20  is a view showing a constitution of a shutter of the fuel cell according to the present embodiment; 
         FIG. 21  is a view showing a constitution of a shutter of the fuel cell according to the present embodiment; 
         FIG. 22  is a view showing a constitution of a shutter of the fuel cell according to the present embodiment; and 
         FIG. 23  is a cross-sectional view schematically showing a constitution of a fuel cell according to a present embodiment. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
           100  Fuel cell body 
           101  Unit cell structure 
           102  Fuel electrode 
           104  Base body 
           106  Fuel electrode side catalyst layer 
           108  Oxidant electrode 
           110  Base body 
           112  Oxidant electrode side catalyst layer 
           114  Solid electrolyte membrane 
           124  Fuel 
           126  Oxidizing agent 
           743  Rotary section 
           811  Fuel container 
           853  Partition plate 
           1117  Pump 
           1234  Pin section 
           1235  Cover 
           1516  Fuel cell 
           1517  Liquid fuel container 
           1518  Vaporized fuel container 
           1519  Gas liquid separating film 
           1520  Vaporized fuel introducing section 
           1521  Vaporized fuel 
           1522  High concentration fuel container 
           1523  High concentration fuel 
           1524  Shutter 
           1525  Collecting pipe 
           1526  Dripping section 
           1527  Fuel absorbing section 
           1528  Vaporized fuel introduction pipe 
           1529  High concentration fuel supply section 
           1530  Cover section 
           1531  Sliding plate 
           1532  High concentration fuel cartridge 
           1533  Spring section 
           1534  Sliding plate 
           1535  Stopper 
           1536  Main body connecting section 
           1537  Spring section 
           1538  Pressing plate 
           1539  Cartridge connecting section 
           1540  Stopper 
           1541  Sealing material 
           1542  Hook 
           1543  Measurement container 
           1544  First container 
           1545  Second container 
           1546  Porous PTFE film 
           1547  Movable plate 
           1548  Supporting section 
           1549  Partition wall 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     In the following, embodiments according to the present invention will be described with reference to the accompanying drawings. Note that in all the figures, common components are designated with the same symbols, and their explanation is appropriately omitted. 
     First Embodiment 
       FIG. 1  is a cross-sectional view schematically showing a constitution of a fuel cell according to this embodiment. Fuel cell  1516  in  FIG. 1  comprises a unit cell structure  101 , a liquid fuel container  1517 , a vaporized fuel container  1518 , a gas liquid separating film  1519 , and a vaporized fuel introducing section  1520 . In  FIG. 1 , there is shown an example of a constitution provided with one unit cell structure  101 , but as described below in the second and succeeding embodiments, it may also be constituted to comprise plural unit cell structures  101 . 
     The unit cell structure  101  includes a fuel electrode  102 , an oxidant electrode  108 , and a solid electrolyte membrane  114 . In the fuel cell shown in  FIG. 1 , a fuel  124  in the liquid fuel container  1517  is directly supplied to the fuel electrode  102 . 
     The solid electrolyte membrane  114  has a role to separate the fuel electrode  102  from the oxidant electrode  108  and to transfer a hydrogen ion between the fuel electrode  102  and the oxidant electrode  108 . For this reason, it is preferred that the solid electrolyte membrane  114  is made of a film having a high hydrogen ion conductivity. Further, it is preferred that the solid electrolyte membrane  114  is chemically stable and has a high mechanical strength. As a material constituting the solid electrolyte membrane  114 , an organic polymer, which has a polar group such as a strong acid group including sulfone group, phosphate group, or the like and a weak acid group including carboxyl group or the like, is preferably used. Examples of such organic polymer include: aromatic condensation polymers such as sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzimidazole; sulfone group-containing perfluorocarbon (Nafion® made by Du Pont Co., Ltd., Aciplex made by Asahi Chemical Industry Co., Ltd.); carboxyl group-containing perfluorocarbon (Flemion S film (registered trademark) made by Asahi Glass Co., Ltd.); sulfonate polyether ether ketone; sulfonated polyether sulfone, and the like. 
     The fuel electrode  102  and the oxidant electrode  108  can be constituted such that a fuel electrode side catalyst layer  106  and an oxidant electrode side catalyst layer  112 , each of which includes a carbon particle carrying a catalyst and a fine particle of a solid electrolyte, are respectively formed on a base body  104  and a base body  110 . Examples of the catalyst include platinum, an alloy of platinum and ruthenium, and the like. As the catalysts of the fuel electrode  102  and the oxidant electrode  108 , a same catalyst may be used, or different catalysts may also be used. 
     Examples of the catalyst of fuel electrode side catalyst layer  106  include platinum, gold, silver, ruthenium, rhodium, palladium, osmium, iridium, cobalt, nickel, rhenium, lithium, lanthanum, strontium, yttrium, or an alloy of them, and the like. As the catalyst of the oxidant electrode side catalyst layer  112  used for the oxidant electrode  108 , it is possible to use the same materials as those of the fuel electrode side catalyst layer, and to use the above exemplified materials. Note that as the catalysts of the fuel electrode side catalyst layer  106  and the oxidant electrode side catalyst layer  112 , a same catalyst may be used, or different catalysts may also be used. 
     As the base body for both of the fuel electrode  102  and the oxidant electrode  108 , it is possible to use a porous base body such as a carbon paper, a body formed of carbon, a body sintered of carbon, a sintered metal, and a foamed metal. 
     The vaporized fuel container  1518  is connected to the liquid fuel container  1517  via the gas liquid separating film  1519 . Further, the vaporized fuel container  1518  is communicated with the vaporized fuel introducing section  1520 . The vaporized fuel  1521  is supplied from the vaporized fuel introducing section  1520  to the vaporized fuel container  1518 , and further supplied to the liquid fuel container  1517  via the gas liquid separating film  1519 . 
     As a material of the wall of the liquid fuel container  1517  and the vaporized fuel container  1518 , it is possible to use a resin such as polyolefins including polypropylene, polyethylene and the like, polycarbonate, polyvinyl chloride, polyether ether ketone, polysulfone, silicone, or a copolymer or a mixture of these materials. 
     The gas liquid separating film  1519  can be formed of a material which is capable of making its surface tension to a liquid fuel  124  different from its surface tension to a gas such as air. Alternatively, a member which is obtained by making the surface of a porous body covered with such a material can also be used as the gas liquid separating film  1519 . As the material of the gas liquid separating film  1519 , for example, a liquid repellent material can be used. For example, when the fuel  124  is methanol or an aqueous solution of methanol, a film suppressing permeation of methanol is used. 
     Specifically, examples of the material used for the gas liquid separating film  1519  include perfluoropolymers such as polytetrafluoroethylene (hereinafter referred to as PTFE) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP); polyfluoroalkyl acrylates such as poly(1H,1H-perfluorooctyl methacrylate), poly(1H,1H,2H,2H-perfluorodecyl acrylate); fluoroolefins such as polyvinylidene fluoride and polyfluorinated ethylene propylene. Further, it is also possible to use polyvinylidene chloride, polyacetal, a copolymer resin of butadiene and acrylonitrile, or the like. 
     Among these, the perfluoropolymer such as PTFE is preferably used because of the excellent balance between a permeableness and selectivity of the gas and a property of film formation. The gas liquid separating film  1519  desirably has a thin film thickness because it needs to allow a gas such as air to be efficiently permeated. Although depending upon physical properties of the film, the gas liquid separating film  1519  is preferably formed to be a thin film having a thickness of 5 μm or less. The use of perfluoropolymer such as PTFE makes it possible to stably form such nonporous thin film. Further, a fluoroalkyl acrylate polymer such as poly(1H,1H-perfluorooctyl methacrylate) or poly(1H,1H,2H,2H-perfluorodecyl acrylate) is preferably used, because it has an excellent property of film formation and can be easily formed into a thin film, and also has a permeableness and selectivity for carbon dioxide. The fluoroalkyl acrylate polymer can be obtained by esterifying a part of or whole of polycarboxylic acid with fluoroalcohol. 
     A molecular weight of the polymer constituting the gas liquid separating film  1519  is preferably set to 1000 to 1,000,000, and more preferably to 3000 to 100,000. When the molecular weight is too large, it may be difficult to prepare a solution, and to make a restricted permeation layer formed to be thin. When the molecular weight is too small, a sufficient restricted permeability may not be obtained. Note that the molecular weight here is the number average molecular weight which can be evaluated by GPC (Gel Permeation Chromatography). 
     Further, a gas permeable nonporous film may also be laminated on a porous film, so as to be used as the gas liquid separating film  1519 . At this time, the above described films can be used as the nonporous film. Further, the porous film is a film made of, for example, polyethersulfone, an acrylic copolymer, or the like. Specifically, the film thickness of the porous film, examples of which include Goretex® made by Japan Gore Tex Co. Ltd., Versapor® made by a Nippon Paul Co. Ltd., Supor® made by a Nippon Paul Co. Ltd. and the like may be set to, for example, 50 μm or more to 500 μm or less. This makes it possible to improve a mechanical strength of the gas liquid separating film  1519 . Thus, the fuel cell  1516  with an excellent mechanical strength can be stably obtained. 
     The above described laminated film can be formed, for example, by applying a solution of the above described resin which serves as a material of the nonporous film on the surface of the porous film by a spin-coating method, and by drying the applied solution. 
     Further, a gas permeable porous film may also be used as the gas liquid separating film  1519 . At this time, a material used for the nonporous gas liquid separating film  1519  may also be used as a material of the porous film, so as to be made porous. For example, a porous film made of a perfluoropolymer such as a porous PTFE film can be used. In this case, the film thickness of the gas liquid separating film  1519  can be set to, for example, 10 μm or more to 500 μm or less. 
     In the fuel cell  1516 , the fuel  124  is supplied to the fuel electrode  102  of the unit cell structure  101  from the liquid fuel container  1517 . The fuel  124  means a liquid fuel supplied to the unit cell structure  101 , and includes an organic solvent which is a fuel component as an essential component. Further, the fuel  124  can be formed into an aqueous solution of the organic solvent serving as the fuel component. Further, methanol, ethanol, dimethyl ether, or other alcohols can be used as the fuel  124  stored in the liquid fuel container  1517 . Further, it is possible to use a liquid hydrocarbon such as cycloparaffin, and a liquid fuel such as formalin, formic acid, hydrazine or the like. Further, alkali can be also added to the liquid fuel. This makes it possible to increase an ion conductivity of a hydrogen ion. 
     Further, the vaporized fuel  1521  is supplied to the vaporized fuel container  1518  from the vaporized fuel introducing section  1520 . The vaporized fuel introducing section  1520  can be, for example, a pipe for guiding a vaporized fuel  1521  stored in a predetermined position to the vaporized fuel container  1518 . The vaporized fuel introducing section  1520  may also be, for example, a chamber which stores the vaporized fuel  1521 . The supply of the vaporized fuel  1521  can be performed by a method in which the liquid fuel or the solid fuel containing the fuel component at a higher concentration than the concentration of the fuel  124  is used, so as to be vaporized. At this time, the vaporizing chamber in which the fuel component in the high concentration liquid or solid fuel is vaporized can be constituted to be communicated with the vaporized fuel introducing section  1520 . The specific method for supplying the vaporized fuel  1521  will be described in detail in the second and succeeding embodiments. 
     The vaporized fuel in the vaporized fuel container  1518  is transferred to the liquid fuel container  1517  via the gas liquid separating film  1519  in accordance with a decrease of the fuel  124  stored in the liquid fuel container  1517 . For example, when the fuel component is a volatile alcohol such as methanol, a vaporized alcohol is dissolved and diffused into the fuel  124  stored in the liquid fuel container  1517 . This construction makes it possible to supply only the necessary amount of the fuel component which is reduced with the operation of the fuel cell  1516  from the vaporized fuel container  1518 . Thus, it is not necessary to provide an auxiliary apparatus such as a pump for supplying the fuel or an auxiliary power supply for stabilizing the output of the fuel cell  1516 . As a result, it is possible to simplify the constitution of the fuel cell  1516  as a whole. 
     Further, since a fuel component is once vaporized and then supplied to the liquid fuel container  1517 , it is possible to use a high concentration liquid or solidified fuel as a raw material of the vaporized fuel  1521 . This makes it possible to downsize the fuel cell  1516  as a whole. 
     Further, since a suitably diluted liquid fuel  124  is supplied to the fuel electrode  102 , it is possible to preferably suppress an occurrence of crossover even in the case where the fuel  124  is a methanol aqueous solution or the like. 
     In this way, the fuel cell  1516  is constituted to have the vaporized fuel  1521  in contact with the liquid fuel  124  via the gas liquid separating film  1519 , thereby allowing the vaporized fuel  1521  to be supplied to the fuel  124 . Therefore, the fuel cell  1516  is capable of stably exhibiting an excellent output capacity in spite of its small-size and simplified constitution. 
     Note that an oxidizing agent  126  is supplied to the oxidant electrode  108  of the unit cell structure  101 . As the oxidizing agent  126 , air can be generally used but oxygen gas may also be supplied. 
     Although the whole surface of the partition wall between the unit cell structure  101  and the vaporized fuel container  1518  is formed as the gas liquid separating film  1519  in the fuel cell  1516 , a part of the partition wall between the unit cell structure  101  and the vaporized fuel container  1518  may also be formed as the gas liquid separating film  1519 . 
     Although the fuel cell  1516  is constituted such that the vaporized fuel  1521  is supplied to the vaporized fuel container  1518  from the vaporized fuel introducing section  1520 , the vaporized fuel introducing section  1520  need not be provided. In this case, as described in the second and succeeding embodiments, for example, the vaporized fuel  1521 , or the solid or liquid fuel from which the vaporized fuel  1521  is generated can be placed in the vaporized fuel container  1518 . 
     Second Embodiment 
     In the present embodiment, there is described a constitution of a fuel cell which has plural unit cell structures  101  as described in the first embodiment. Here, a constitution in which plural unit cell structures  101  are stacked in a plane is described as an example. The fuel cell according to the present embodiment is applicable to small electric appliances including a portable telephone, portable personal computers such as a note type, a PDA (Personal Digital Assistant), various kinds of cameras, a navigation system, and a portable music reproducing player. 
       FIG. 2  is a view schematically showing a constitution of a fuel cell according to the present embodiment. The fuel cell shown in  FIG. 2  includes plural unit cell structures  101 , a fuel container  811 , a partition plate  853 , and a collecting pipe  1525 . The collecting pipe  1525  collects a liquid that has passed through a fuel electrode  102  of the unit cell structure  101 , and water generated by a cell reaction in an oxidant electrode, and serves as a path through which the collected liquid and water are returned to the fuel container  811 . 
       FIG. 3  is a cross-sectional view along the line A-A′ in  FIG. 2 . The fuel cell shown in  FIG. 3  is constituted such that plural fuel electrodes  102  are provided on one surface of a single sheet of solid electrolyte membrane  114 , that plural oxidant electrodes  108  are provided on the other surface, and that plural unit cell structures  101  shares the solid electrolyte membrane  114  so as to be arranged in a same plane. Further, a fuel container  811  is provided so as to cover and surround the outer side of the fuel electrode  102 , and a fuel  124  stored in the fuel container  811  is directly supplied to the fuel electrode  102 . 
     The fuel container  811  shown in  FIG. 2  and  FIG. 3  corresponds to the liquid fuel container  1517  in  FIG. 1 , and a fuel  124  supplied to the fuel electrode  102  is stored in the fuel container  811 . Further, in  FIG. 3 , a vaporized fuel container  1518  is provided on the bottom part of the fuel container  811 , and a gas liquid separating film  1519  is provided at a part between the vaporized fuel container  1518  and the fuel container  811 . Further, a high concentration fuel container  1522  communicated with the vaporized fuel container  1518  via a shutter  1524  is provided on the side of the fuel container  811 . 
     The fuel  124  stored in the fuel container  811  is made to flow along plural partition plates  853  provided in fuel container  811 , and is successively supplied to the plural unit cell structures  101 . The fuel  124  which is supplied to the unit cell structures  101  but not used for the cell reaction is returned to the fuel container  811  from a collecting pipe  1525 . A ratio of water in the fuel  124  is increased in accordance with the use of the fuel cell, as shown by the above described formula (1) and formula (2), so that a concentration of the fuel component in the fuel  124  is decreased. 
     Then, a vaporized fuel  1521  is supplied to the fuel container  811  via the gas liquid separating film  1519  provided between the high concentration fuel container  1522  and the fuel container  811 . Here, a high concentration fuel  1523  stored in the high concentration fuel container  1522  is vaporized to pass through the shutter  1524 , and is then dissolved in the fuel  124  stored in the fuel container  811  via the gas liquid separating film  1519 . This makes it possible to stably supply the fuel  124  having a predetermined concentration to the fuel electrode  102  of the unit cell structure  101 . 
     The shutter  1524  is constituted so as to separate the vaporized fuel container  1518  from the high concentration fuel container  1522 , and to be openable and closable. By opening and closing the shutter  1524 , a concentration of a fuel vapor in the vaporized fuel container  1518  can be adjusted. When the shutter  1524  is opened, the vaporized fuel  1521  can be transferred from the high concentration fuel container  1522  to the vaporized fuel container  1518 . The shutter  1524  can be constituted as follows. 
       FIG. 20(   a ) and  FIG. 20(   b ) are views showing a neighborhood part of a shutter  1524  of the fuel cell shown in  FIG. 3 .  FIG. 20(   a ) shows a state where the shutter  1524  is closed, and  FIG. 20(   b ) shows a state where the shutter  1524  is opened. The shutter  1524  consists of a movable plate  1547  and a rotary section  743 . The movable plate  1547  slides by the rotation of the rotary section  743  engaged with the movable plate  1547 , to open and close the shutter  1524 . 
       FIG. 21(   a ) and  FIG. 21(   b ) are views showing another constitution of a shutter  1524 .  FIG. 21(   a ) and  FIG. 21(   b ) also show a neighborhood part of the shutter  1524  of the fuel cell in  FIG. 3 .  FIG. 21(   a ) shows a state where the shutter  1524  is closed, and  FIG. 21(   b ) shows a state where the shutter  1524  is opened. 
     In  FIG. 21(   a ) and  FIG. 21(   b ), the opening and closing between the high concentration fuel container  1522  and the vaporized fuel container  1518  are performed by the rotation of a movable plate  1547  constituting a shutter  1524  along a rotary section  743  as an axis. 
       FIG. 22(   a ) and  FIG. 22(   b ) are views showing another constitution of a shutter  1524 .  FIG. 22(   a ) and  FIG. 22(   b ) also show a neighborhood part of the shutter  1524  of the fuel cell in  FIG. 3 .  FIG. 22(   a ) shows a state where the shutter  1524  is closed, and  FIG. 22(   b ) shows a state where the shutter  1524  is opened. 
     In  FIG. 22(   a ) and  FIG. 22(   b ), a supporting section  1548  which supports a movable plate  1547  constituting a shutter  1524  is engaged with a rotary section  743 . Thus, the supporting section  1548  slides by the rotation of the rotary section  743 , thereby enabling the movable plate  1547  fixed to the supporting section  1548  to open and close one end of the vaporized fuel container  1518 . 
     By the provision of shutter  1524 , it is possible to stop the supply of the vaporized fuel  1521 , when the fuel cell is not used. Note that the shutter  1524  may be constituted so as to be switched in two states of open and close, or to make a coverage ratio of the end surface of the vaporized fuel container  1518  adjusted in the predetermined stage. With the constitution in which a coverage ratio of the interface between the vaporized fuel container  1518  and the high concentration fuel container  1522  is adjustable, it is possible to further precisely adjust the supply of the vaporized fuel  1521  by using the shutter  1524 . Further, although not shown in  FIG. 2  and  FIG. 3 , a control section which controls the opening and closing of the shutter  1524  can also be provided in the fuel cell. This makes it possible to further surely adjust the opening and closing of the shutter  1524 . 
     In the fuel cell according to the present embodiment, the high concentration fuel  1523  is vaporized and supplied to the fuel container  811 . Thus, when the fuel in the fuel container  811  is consumed, a necessary amount of the fuel component is supplied as the vaporized fuel  1521 . For example, when the fuel component is a material having an excellent volatility such as methanol, the high concentration fuel  1523  is naturally vaporized even at room temperature and is easily dissolved and diffused in the liquid fuel  124  in the fuel container  811 . This makes it possible to stably supply the fuel with a simple constitution, without using an auxiliary apparatus for fuel supply such as a pump. At this time, the provision of the gas liquid separating film  1519  and the shutter  1524  makes it possible to selectively transfer the vaporized fuel  1521  to the side of the fuel container  811  in predetermined timing. Further, the liquid fuel  124  is supplied to the fuel electrode  102  from the fuel container  811 , so that it is possible to stably adjust the fuel  124  supplied to the fuel electrode  102  to a predetermined concentration. Further, the high concentration fuel  1523  is stored in the high concentration fuel container  1522 , so that it is possible to downsize the high concentration fuel container  1522 . 
     Note that in the present embodiment, the arrangement of the gas liquid separating film  1519  and the shutter  1524  is not limited to the above, and various kinds of constitution can be adopted. In the following, fuel cells with different arrangements are exemplified. 
     For example,  FIG. 4  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. In  FIG. 4 , the fuel container  811  is provided so as to cover the upper part of the unit cell structure  101 . Further, the shutter  1524  is provided on the upper part of the high concentration fuel container  1522 . With this constitution, it is possible to shorten the moving path of the vaporized fuel  1521  naturally vaporized in the high concentration fuel container  1522  to the vaporized fuel container  1518  in comparison with the constitution shown in  FIG. 3 . This makes it possible to further downsize and simplify the constitution of the fuel cell. 
       FIG. 5  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. The basic constitution of the fuel cell in  FIG. 5  is the same as that of the fuel cell in  FIG. 4 , but is different in that the gas liquid separating film  1519  is provided on the side face of fuel container  811 . In this constitution, the vaporized fuel  1521  can also be stably supplied to the fuel container  811 . 
     Further,  FIG. 6  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. The basic constitution of the fuel cell in  FIG. 6  is also the same as that of the fuel cell in  FIG. 4 , but is different in that the gas liquid separating film  1519  and the shutter  1524  are provided so as to be adjacent to each other. The gas liquid separating film  1519  is provided on the side of the fuel container  811 , and the shutter  1524  is provided on the side of the high concentration fuel container  1522 . In this constitution, when the shutter  1524  is closed, the gas liquid separating film  1519  is covered by the shutter  1524 , to makes it possible to adjust the supply of the vaporized fuel  1521  to the fuel  124  stored in the fuel container  811  more precisely. 
     Further, in the above examples, the gas liquid separating film  1519  may be formed of, for example, a material whose aperture ratio is changed in accordance with a concentration of the fuel  124  in the fuel container  811 . This makes it possible to impart a function for adjusting the supply of the vaporized fuel  1521  to the gas liquid separating film  1519  itself. 
     In the fuel cell constituted as described above, it is possible to use a liquid fuel or a solid fuel containing a fuel component at high concentration as the high concentration fuel  1523 . By using a solidified fuel as the high concentration fuel  1523 , it is possible to suppress the leakage of the high concentration fuel  1523 . Thereby, the fuel cell can be used more safely. Also, even when a liquid fuel is used as the high concentration fuel  1523 , the liquid fuel is supplied to the fuel container  811  as the vaporized fuel  1521 , so that it is possible to suppress the leakage of the liquid of the high concentration fuel  1523 . 
     When a high concentration liquid fuel is used as the high concentration fuel  1523 , it is possible to use, for example, an aqueous solution or a raw liquid which have a fuel component concentration in the range of about 60 to 100% by volume. By using an organic liquid fuel or an aqueous solution thereof which have a fuel component concentration of 60% by volume or more, it is possible to store, in a container, the liquid fuel having a higher concentration than that of the fuel  124  supplied to the liquid fuel supply system of the fuel cell. This makes it possible to stably obtain a fuel container which is small and capable of supplying the fuel for a long period of time. 
     Further, when a liquid fuel is used as the high concentration fuel  1523 , the fuel cell may be constituted as follows.  FIG. 23  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. 
     The basic constitution of the fuel cell shown in  FIG. 23  is the same as that of the fuel cell shown in  FIG. 4 , but is different in that the shutter  1524  is provided on the side face which separates the vaporized fuel container  1518  from the high concentration fuel container  1522 , and in that the gas liquid separating film  1519  is provided in the high concentration fuel container  1522 , and the high concentration fuel container  1522  is partitioned into two chambers by the gas liquid separating film  1519 . 
     By providing the gas liquid separating film  1519  in the high concentration fuel container  1522 , so as to make the high concentration fuel container  1522  partitioned into two chambers, it is possible to suppress the leakage of the high concentration fuel  1523  to the outside of the high concentration fuel container  1522  when the one chamber of the high concentration fuel container  1522  is be used as a high concentration fuel storage chamber to make the high concentration fuel  1523  as a liquid fuel surely present in the high concentration fuel storage chamber. Further, the other chamber can be used as a vaporizing chamber of high concentration fuel  1523 . Here, the vaporizing chamber is a chamber brought into contact with the vaporized fuel container  1518 , and the shutter  1524  is provided between the vaporizing chamber and the vaporized fuel container  1518 . With this constitution, it is possible to make a vaporized fuel  1521  vaporized from the liquid fuel stored in the high concentration fuel storage chamber selectively present in the vaporizing chamber from the gas liquid separating film  1519 . It is also possible to adjust the opening and closing of the shutter  1524 , and to thereby adjust the amount of the vaporized fuel  1521  supplied to the vaporized fuel container  1518 . Further, it is possible to more selectively supply the vaporized fuel  1521  to a fuel cell body  100 . As such gas liquid separating film  1519 , it is possible to use a gas permeable nonporous film exemplified in the first embodiment, and the like. 
     Note that it is possible to make the high concentration liquid fuel impregnated in a wicking material which is a porous material capable of absorbing liquid fuel. The wicking material can be formed of, for example, a porous material such as a foam. Specifically, a resin which is, for example, polyurethane, melamine, polyamides such as nylon, polyethylene, polypropylene, polyesters such as polyethylene terephthalate, cellulose, or polyacrylonitrile, is used as the wicking material. 
     Further, when a solid fuel is used as the high concentration fuel  1523 , it is possible to gelatinize a liquid of the fuel component, and to use the gelatinized fuel component. The gelling agent used for the gelatinized fuel can be suitably selected and used in accordance with the kind of the fuel component, from various materials which are stable in the use temperature of the fuel cell. For example, when the fuel component is alcohol such as methanol, it is possible to use, as the gelling material, a cross-linked product of polymer material such as polyacrylamide, polyethylene oxide, polyacrylate and polyvinyl alcohol. These materials may be used independently, or may be used by combining plural kinds of these materials. Further, for example, a cellulose derivative such as a hydroxyethyl cellulose, a hydroxypropyl cellulose, and a carboxymethyl cellulose, and a cross-linked product of so-called semisynthetic polymer material such as a carboxyvinyl polymer (carbomer) may also be used. 
     Further, a solid fuel can also be obtained without using the polymer gelling agent. For example, when the fuel component is alcohol, a solid fuel can be prepared by obtaining a gel-like sodium stearate by saponification reaction in a mixture formed by mixing a fatty acid such as sodium stearate with a hydroxide such as sodium hydroxide. Further, instead of sodium hydroxide, a compound which exhibits alkalinity in an aqueous solution, such as borax Na 2 [B 4 O 5 (OH) 4 ]8H 2 O, may also be used. 
     In the fuel cells shown in  FIG. 2  to  FIG. 6 , the high concentration fuel  1523  may be liquid or solid. Further, when the high concentration liquid fuel is used as the high concentration fuel  1523 , the fuel cell can also be constituted as follows.  FIG. 7  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. The basic constitution of the fuel cell shown in  FIG. 7  is the same as that of the fuel cell shown in  FIG. 3 , but is different in that the supply of the vaporized fuel  1521  is controlled by adjusting a dripping rate or a dripping amount of the high concentration fuel  1523  in the high concentration fuel container  1522 . 
     In  FIG. 7 , the high concentration fuel container  1522  has a dripping section  1526 , and a fuel absorbing section  1527  is provided in a position to which the high concentration fuel  1523  is dripped from the dripping section  1526 . For example, a porous body absorbing high concentration fuel  1523  can be used as the fuel absorbing section  1527 . As a material of the porous body, those having a resistance against the fuel component may be used, which is, for example, a metal such as SUS, Ti, Ni, and Al; a metal oxide such as silica, alumina, and zirconia; a ceramic such as silicon carbide, titanium carbide, and zeolite; or a polymer material such as cellulose and polyurethane. Note that as another polymer material, the material used as the above described wicking material can also be used. 
     The fuel cell shown in  FIG. 7  is constituted such that the high concentration fuel  1523  dripped from the dripping section  1526  is absorbed in the fuel absorbing section  1527 , and thereafter, the fuel absorbed in the fuel absorbing section  1527  is vaporized so as to be supplied to the vaporized fuel container  1518 . Thereby, it is possible to adjust the supply of the vaporized fuel  1521  by adjusting the dripping amount or the dripping rate from the dripping section  1526 , without an opening and closing shutter  1524 . 
     Further, when a solid fuel is used as the high concentration fuel  1523 , the fuel cell may be constituted as follows.  FIG. 8  is a cross-sectional view showing another constitution of a fuel cell according to the present embodiment. The basic constitution of the fuel cell shown in  FIG. 8  is the same as that of the fuel cell shown in  FIG. 4 ; but is different in that the shutter  1524  is provided on the side face which separates the vaporized fuel container  1518  from the high concentration fuel container  1522 , and in that a partition wall  1549  is provided in the high concentration fuel container  1522 . 
     The partition wall  1549  is a member which separates the high concentration fuel container  1522  into a fuel storage chamber and a vaporizing chamber, which is made of a gas permeable material. Specifically, as a material of the partition wall  1549 , a material which can be used for the fuel absorbing section  1527  in the fuel cell shown in  FIG. 7  can be used. By providing the partition wall  1549  in the high concentration fuel container  1522 , it is possible that the high concentration fuel  1523  as a solid fuel is held in a predetermined region of the high concentration fuel container  1522  to suppress the leakage of the high concentration fuel to the outside of the container, and that the high concentration fuel  1523  is vaporized so as to be surely supplied to the side of the fuel container  811 . Further, by using a solid fuel as the high concentration fuel  1523 , it is possible to vaporize the high concentration fuel  1523  and to stably supply the vaporized fuel to fuel container  811 , independently of the arrangement direction of the high concentration fuel container  1522 . Further, the leakage of the high concentration fuel  1523  can be suppressed. As a result, the fuel cell can be more preferably used for a portable electric appliance. 
     Note that in the above constitution, a small pump may also be used instead of the shutter  1524 .  FIG. 9  is a cross-sectional view showing a constitution of a fuel cell having a pump. The basic constitution of the fuel cell in  FIG. 9  is the same as that of the fuel cell shown in  FIG. 3 , but is different in that the high concentration fuel in high concentration fuel container  1522  is vaporized, and the vaporized fuel  1521  is supplied to the vaporized fuel container  1518  from the vaporized fuel introduction pipe  1528  by using a pomp  1117 . 
     As the pump  1117 , for example, a piezoelectric element such as a small-sized piezoelectric motor whose power consumption is very small can be used. Further, although not shown in  FIG. 9 , it is possible to provide a control section which controls the operation of the pump  1117 , for the fuel cell. With this constitution, it is possible to adjust the supply amount of the vaporized fuel  1521  by adjusting the exhausting rate of the pump  1117 , and to thereby surely control the supply of the vaporized fuel  1521 . 
     Further, in the above described constitution, when the high concentration fuel  1523  is a high concentration liquid fuel or a gelatinized fuel which has fluidity in a certain extent, the high concentration fuel container  1522  may be constituted so as to enable the supply of the high concentration fuel  1523  to be performed. Here, a case of the fuel cell shown in  FIG. 4  is explained as an example. 
       FIG. 10  is a cross-sectional view showing a constitution of a fuel cell according to the present embodiment. The basic constitution of the fuel cell in  FIG. 10  is the same as that of the fuel cell shown in  FIG. 4 , but is different in that an openable and closable high concentration fuel supply section  1529  which is communicated with the storage chamber of the high concentration fuel  1523  is provided for the high concentration fuel container  1522 . Note that the high concentration fuel supply section  1529  is provided for the wall of the upper section of the high concentration fuel container  1522  in  FIG. 10 , but the high concentration fuel supply section  1529  can also be provided for the side wall of the high concentration fuel container  1522 . 
     By providing the high concentration fuel supply section  1529 , even when the high concentration fuel  1523  is consumed due to the use of the fuel cell, it is possible to inject and supply the high concentration fuel  1523  from the high concentration fuel supply section  1529 . This makes it possible to stably operate the fuel cell for a longer period of time. 
     As the constitution of high concentration fuel supply section  1529 , it is possible to adopt various kinds of constitution, by which the high concentration fuel supply section  1529  can be opened when the high concentration fuel  1523  is supplied and can be surely closed during the use of the fuel cell except it. For example, the high concentration fuel supply section  1529  may be constituted by an opening passing through the wall of the high concentration fuel container  1522  and a closing member closing the opening. At this time, the closing member may be constituted so as to be fit to the wall with screws or the like, and to thereby suppress the leakage of the high concentration fuel  1523 . Further, for example, the high concentration fuel supply section  1529  may also be constituted by an opening passing through the wall of the high concentration fuel container  1522  and a cap covering the opening. Further, for example, the high concentration fuel supply section  1529  may also be constituted by an opening passing through the wall of the high concentration fuel container  1522  and a sliding plate which can be made to slide along the wall to thereby open and close the opening. 
     Further, when the high concentration fuel  1523  is a solid fuel, it is possible to supply the solid fuel by providing an openable and closable cover section for the high concentration fuel container  1522 .  FIG. 11(   a ) and  FIG. 11(   b ) are views showing a constitution of a fuel cell having a high concentration fuel container  1522  providing a cover section. The basic constitution of the fuel cell shown in  FIG. 11(   a ) and  FIG. 11(   b ) is the same as that of the fuel cell in  FIG. 4 , but is different in that an openable and closable cover section  1530  is provided on the side wail of the high concentration fuel container  1522 . A casing constituting the upper wall surface of the vaporized fuel container  1518  and the cover section  1530  constituting the side wall surface of the high concentration fuel container  1522  are connected with each other by a hinge having a pin section  1234 . Further, although not shown in  FIG. 11(   a ) and  FIG. 11(   b ), the high concentration fuel container  1522  has a fixing member for fixing the cover section  1530  in the closed state. 
     In the fuel cell shown in  FIG. 11(   a ) and  FIG. 11(   b ), the side face of the high concentration fuel container  1522  is opened by making the cover section  1530  rotated along the pin section  1234  as a rotation center. When the high concentration fuel  1523  is supplied to the high concentration fuel container  1522 , the cover section  1530  is opened, and a sliding plate  1531  provided on the bottom section of the high concentration fuel container  1522  slides toward the outside of the high concentration fuel container  1522 , so as to be drawn out.  FIG. 11(   a ) shows a state where the cover section  1530  is opened, and the sliding plate  1531  is drawn out. Then, a new solid fuel is set on the sliding plate  1531 , and the sliding plate  1531  slides toward the inside of the high concentration fuel container  1522 , to store the high concentration fuel  1523  in the inside of the high concentration fuel container  1522 . Then, the cover section  1530  is closed ( FIG. 11  ( b )). 
     Note that in  FIG. 11 , although the high concentration fuel container  1522  is constituted so as to be opened and closed by making the cover section  1535  rotated along the pin section  1234  as the rotation center, the method for opening and closing the cover section is not limited to this constitution and the cover section can be mounted by such as a method for fitting the cover section by hooking it by a claw or the like, and a slide lock method. 
     Further, in the above described fuel cell, the constitution in which the gas liquid separating film  1519  is provided in the vaporized fuel container  1518  is shown, but the gas liquid separating film  1519  may also be provided in the high concentration fuel container  1522  in the fuel cell according to the present embodiment. For example, in the fuel cell shown in  FIG. 6 , the gas liquid separating film  1519  and the shutter  1524  may also be provided in the high concentration fuel container  1522 . In this case, the vaporized fuel  1521  in the high concentration fuel container  1522  can be transferred to the vaporized fuel container  1518  via the gas liquid separating film  1519 , by opening the shutter  1524 . 
     Further, in the fuel cell shown in  FIG. 3 , plural unit cell structures  101  are arranged to share a single sheet of solid electrolyte membrane  114 , but plural unit cell structures  101 , each of which is independently provided with a solid electrolyte membrane  114 , may also be arranged to be integrated in a plane. This makes it possible to suppress the transfer of protons in the plane direction of solid electrolyte  114 , when potentials of adjacent unit cell structures  101  are different from each other. 
     Third Embodiment 
     In the fuel cell of the above described embodiment, the high concentration fuel container  1522  storing the high concentration fuel  1523  may be a fuel cartridge. The fuel cartridge can be attached to and detached from the fuel cell body, and can be exchanged and carried. 
       FIG. 12(   a ) and  FIG. 12(   b ) are cross-sectional views schematically showing a constitution of a fuel cartridge and a high concentration fuel container  1522  in which the fuel cartridge is stored. This fuel cell consists of a fuel cell body  100  and a high concentration fuel cartridge  1532 . Similarly to the fuel cell shown in  FIG. 11 , an openable and closable cover section  1530  is constituted so as to be attached on the side wall of the fuel cell body  100 , and to enable the high concentration fuel cartridge  1532  to be inserted. 
     As shown in  FIG. 12  ( a ), the high concentration fuel cartridge  1532  has a storage chamber for storing a high concentration fuel  1523 , a spring section  1533 , and a sliding plate  1534 . When a force is applied to the sliding plate  1534  from a side thereof, the spring section  1533  is contracted. Further, the high concentration fuel container  1522  has a stopper  1535  which fixes the sliding plate  1534  of the high concentration fuel cartridge  1532 . 
     The exchange of the high concentration fuel cartridge  1532  is performed in such a manner that the cover section  1530  is opened and then the high concentration fuel cartridge  1532  is inserted from the side of the high concentration fuel container  1522 . At this time, when the high concentration fuel cartridge  1532  is stored in the high concentration fuel container  1522 , the spring section  1533  is expanded and contracted from the position where the sliding plate  1534  is brought into contact with the stopper  1535 . Thus, by making the high concentration fuel cartridge  1532  completely stored and making the cover section  1530  closed and fixed by a fixing member (not shown), the high concentration fuel cartridge  1532  can be fixed in the high concentration fuel container  1522  ( FIG. 12  ( b )). 
     In the fuel cell shown in  FIG. 12(   a ) and  FIG. 12(   b ), it is possible to make the high concentration fuel cartridge  1532  surely fixed and stably held in the inside of the fuel cell body  100  by providing the spring section  1533 . Therefore, the fuel cell can be preferably used for a portable electric appliance or the like. Further, the exchange of the high concentration fuel cartridge  1532  can be easily performed with a simple constitution. This makes it possible to facilitate the supply of the high concentration fuel  1523  and to stably operate the fuel cell for a long period of time. 
     Note that in the fuel cell shown in  FIG. 12(   a ) and  FIG. 12(   b ), a gas liquid separating film  1519  may be provided for the high concentration fuel cartridge  1532 . For example, in the case where the high concentration fuel cartridge  1532  is inserted in the fuel cell body  100 , the gas liquid separating film  1519  can be provided so as to face the shutter  1524 . This enables the vaporized fuel  1521  to be more surely transferred to the vaporized fuel container  1518  from the high concentration fuel cartridge  1532 . 
     Further, the constitution of the high concentration fuel cartridge  1532  and the method for mounting the high concentration fuel cartridge  1532  to the high concentration fuel container  1522  are not limited to the above described constitution, but various kinds of constitution can be adopted. For example,  FIG. 13(   a ) and  FIG. 13(   b ) are cross-sectional views showing another constitution of a high concentration fuel cartridge  1532  and a high concentration fuel container  1522 . 
     In  FIG. 13  ( a ), the high concentration fuel cartridge  1532  has a storage chamber in which a solid high concentration fuel  1523  is stored and a fuel absorbing section  1527  which partitions the storage chamber from the outside in the high concentration fuel cartridge  1532 . A main body connecting section  1536  is also provided for the high concentration fuel cartridge  1532 . A part of the wall of the main body connecting section  1536  is formed in a recessed shape, so as to fit into a cartridge connecting section  1539  which is formed in a projected shape and which is provided for the high concentration fuel container  1522 . Further, the high concentration fuel container  1522  is provided with a pressing plate  1538  which fixes the high concentration fuel cartridge  1532 , and a spring section  1537  which can be expanded and contracted so as to enable the position of the pressing plate  1538  to be movable. 
     In mounting the high concentration fuel cartridge  1532  to the high concentration fuel container  1522 , a space sufficient for making the spring section  1537  contracted and for making the high concentration fuel cartridge  1532  inserted into the high concentration fuel container  1522  is formed, and thereby the high concentration fuel cartridge  1532  is mounted. At this time, by making the main body connecting section  1536  and the cartridge connecting section  1539  fit with each other, and by bringing the pressing plate  1538  into contact with the wall surface of the high concentration fuel cartridge  1532 , the high concentration fuel cartridge  1532  can be fixed in the high concentration fuel container  1522  ( FIG. 13  ( b )). 
     Because the recessed section of the main body connecting section  1536  and the projected section of the cartridge connecting section  1539  are opening, the high concentration fuel  1523  vaporized in the high concentration fuel container can be transferred to the fuel cell body  100  by connecting the high concentration fuel cartridge  1532 . Note that the high concentration fuel cartridge  1532  can be used in such a manner that the opening of the main body connecting section  1536  is sealed by, for example, a sealing member before the use of the high concentration fuel cartridge  1532 , and that the sealing member is peeled off when the high concentration fuel cartridge  1532  is used. 
     Further,  FIG. 14(   a ) and  FIG. 14(   b ) are views showing another constitution of a high concentration fuel cartridge  1532  and a high concentration fuel container  1522  which is constituted so as to enable the high concentration fuel cartridge  1532  to be mounted thereto.  FIG. 14(   a ) is a cross-sectional view of the high concentration fuel cartridge  1532  and the high concentration fuel container  1522 .  FIG. 14(   b ) is also a top view of them. The basic constitution of the fuel cell shown in  FIG. 14(   a ) and  FIG. 14(   b ) is the same as that of the fuel cell shown in  FIG. 13(   a ) and  FIG. 13(   b ), but is different in that the high concentration fuel cartridge  1532  is constituted so as to be fixed by a hook  1542  and a stopper  1540 , instead of the method for fixing the high concentration fuel cartridge  1532  by the pressing plate  1538  and the spring section  1537 . 
     As shown in  FIG. 14(   a ), the stopper  1540  which fixes the hook  1542  is provided for the high concentration fuel cartridge  1532 , and the hook  1542  is provided for the cartridge connecting section  1539  of the high concentration fuel container  1522 . Thus, by making the cartridge connecting section  1539  fit into the main body connecting section  1536  and making the hook  1542  engage the stopper  1540 , the high concentration fuel cartridge  1532  can be fixed in the high concentration fuel container  1522  ( FIG. 14  ( b )). 
     Note that in  FIG. 14(   a ) and  FIG. 14(   b ), a sealing material  1541  is stuck on the circumference of a main body connecting section  1536  in the high concentration fuel  1523 . As the sealing material  1541  which is an elastic member, it is possible to use, for example, a polymer material having a low gas permeability and flexibility. As such a material, it is possible to use, for example, an elastomer such as ethylene propylene rubber and silicone rubber. When ethylene propylene rubber is used as the sealing material  1541 , it is possible to use a copolymer of ethylene and propylene (EPM), or a copolymer of ethylene, propylene and a third component (EPDM). 
     In the fuel cells shown in  FIG. 13  and  FIG. 14 , by using a material having an excellent gas liquid separating property for the fuel absorbing section  1527  provided in the high concentration fuel cartridge  1532 , it is possible to preferably use this as the gas liquid separating film  1519 . This enables the vaporized fuel more surely transferred to the vaporized fuel container  1518 . 
     Further, in the high concentration fuel cartridge  1532  of the fuel cells shown in  FIG. 13  and  FIG. 14 , a gas liquid separating film  1519  may be provided instead of the fuel absorbing section  1527 . Thereby, even when the high concentration fuel container  1522  is a cartridge type, it is possible to make the fuel container surely held in a predetermined region of the high concentration fuel cartridge  1532 . Further, there may be a constitution in which the vaporized fuel  1521  vaporized from the high concentration fuel  1523  is selectively passed through the gas liquid separating film  1519 , and is transferred to the fuel cell body  100 . Thereby, similarly to the fuel cell shown in  FIG. 23 , even when the high concentration fuel  1523  is a liquid, it is possible to suppress the leakage of the high concentration fuel  1523 . As such gas liquid separating film  1519 , it is possible to use, for example, a gas permeable nonporous film as exemplified in the first embodiment. 
     In this way, in the constitution according to the present embodiment, it is possible to use a portable cartridge type container as the high concentration fuel container  1522  which contains the fuel component at a high concentration. This enables a fuel cell as a whole to be downsized, and to stably exhibit an outstanding output performance for a long period of time. Further, with the use of a solid fuel as a high concentration fuel  1523 , even in the case where a cartridge type is adopted, it is possible to suppress the leakage of fuel when the cartridge is carried, and to further improve the safety in use. 
     In the above, the present invention is explained on the basis of the embodiments. These embodiments are merely exemplary, and it will be understood by persons skilled in the art that various modifications may be made by a combination of each of the components and treatment processes of these embodiments, and that these modifications are also included within the scope of the present invention. 
     For example, the above described embodiments are explained by taking, as an example, a constitution in which the vaporized fuel  1521  is transferred into the fuel  124  via the gas liquid separating film  1519  constituting a part of the wall of the liquid fuel container  1517  and the fuel container  811 , but the supply section of the vaporized fuel  1521  can also be provided for any part of the liquid fuel supply system. For example, when a liquid fuel supply pipe is provided for a liquid fuel supply system, a gas liquid separating film  1519  may be provided for a part of the wall of the liquid fuel supply pipe, so as to make the liquid fuel supply pipe communicated with the vaporized fuel introducing section  1520  or the vaporized fuel container  1518  via the gas liquid separating film 
     Further, the above described embodiments is mainly explained to be an embodiment, in which the high concentration fuel  1523  stored in the high concentration fuel container  1522  is naturally vaporized, but an adjustment member which adjusts a vaporization amount of the high concentration fuel  1523  may also be provided. The adjustment of the vaporization amount can be performed, for example, by adjusting the temperature of the high concentration fuel container  1522 , or by giving a vibration to the high concentration fuel container  1522 . 
     In the above embodiments, a small pump  1117  may also be used to supply the liquid fuel  124  to the fuel electrode  102 . For example, a pump which can be used in the fuel cell shown in  FIG. 9  can be used as the pump  1117 . 
     Example 
     (Measurement of Diffusion Rate of Methanol Gas into Methanol Aqueous Solution) 
     In the present embodiment, a rate at the time when methanol gas is diffused into a methanol aqueous solution was measured at first.  FIG. 15  is a cross-sectional view showing a container used for the measurement. In  FIG. 15 , a first container  1544 , a porous PTFE film  1546 , and a second container  1545  were successively stacked in this order from the bottom in a measurement container  1543 . The first container  1544  and the second container  1545  are communicated with each other via the porous PTFE film  1546 , so as to enable gas in the first container  1544  to be selectively transferred to the side of the second container  1545 . 
     Pure methanol was stored in the first container  1544 , and 12 ml of pure water was stored in the second container  1545 . Methanol in the first container  1544  is vaporized to become methanol gas, which is then transferred to the side of the second container  1545  via the porous PTFE film  1546 . Then, the methanol gas is dissolved in the pure water stored in the second container  1545 , thereby causing the methanol concentration to be increased. 
     The temporal change of the concentration of liquid methanol in the second container  1545  was measured by using a measurement container  1543 . Note that the concentration of liquid methanol in the second container  1545  at the time of starting the measurement is 0% by volume. Further, the concentration of liquid methanol in the second container  1545  was measured by gas chromatography. The area in which the porous PTFE film  1546  is in contact with methanol gas was set to 10 cm 2 . 
       FIG. 16  is a graph showing a relationship between the elapsed time and the methanol concentration in the second container  1545 . Further,  FIG. 17  is a graph showing a relationship between the concentration of liquid methanol in the second container  1545  and the diffusion rate, based on the result shown in  FIG. 16 . Here, from a calculation about the unit cell structure  101  of the fuel cell explained in the above described embodiment, for example, pure methanol of 0.016 ml/h/cm 2  is needed in order to supply a current with a current density of 60 mA/cm 2 . From  FIG. 17 , it can be seen that the methanol supply amount sufficient for the above described operating condition is obtained, when the method according to the present embodiment is used. For this reason, it is possible to stably operate the fuel cell for a long period of time by using the method in which the high concentration methanol is gasified and supplied to fuel  124 . 
     Further, as shown in  FIG. 16  and  FIG. 17 , the diffusion rate was decreased as the methanol concentration in the second container  1545  is increased. Then, when the methanol concentration in the second container  1545  is increased, the diffusion of the high concentration methanol is stopped, and the concentration of liquid methanol in the second container  1545  is made constant. For this reason, it is possible to make the concentration of liquid methanol in the second container  1545  kept constant by using the porous PTFE film  1546 . As a result, by applying this method to a liquid fuel supply system of fuel cell, it is possible to stably supply liquid fuel of a predetermined concentration to the fuel electrode  102  without using an auxiliary apparatus, such as a pump. 
     (Application to Fuel Cell) 
     Then, the above described constitution was applied to a fuel cell in order to evaluate the power generation property of the fuel cell.  FIG. 18  is a cross-sectional view schematically showing a constitution of the fuel cell used in the present embodiment. The fuel cell shown in  FIG. 18  basically has the same constitution as that of fuel cell  1516  shown in  FIG. 1 . A high concentration fuel container  1522  communicating with a vaporized fuel container  1518  in  FIG. 18  corresponds to the vaporized fuel introducing section  1520  in  FIG. 1 . In this constitution, a high concentration fuel  1523  placed in the high concentration fuel container  1522  is vaporized, so as to be transferred, as a vaporized fuel, from the high concentration fuel container  1522  to the vaporized fuel container  1518  and a gas liquid separating film  1519  in this order, and then, is dissolved in a fuel  124  stored in a liquid fuel container  1517 . Note that although not shown in  FIG. 18 , a circulation path through which the fuel  124  is circulated was provided. 
     In the fuel cell shown in  FIG. 18 , the temporal change of voltage at the time when the fuel cell was discharged at a constant current of 1 A at room temperature was measured. A porous film of PTFE was used as the gas liquid separating film  1519 . Further, the fuel cell was operated by circulating the fuel  124 . 
     A methanol aqueous solution of 5% by volume was used as the fuel  124 . Further, pure methanol or solidified (gelatinized) methanol fuel gelatinized by using a gelling agent was used as the high concentration fuel  1523 . Table 1 shows the fuel used in examples and a comparative example. In Table 1, “fuel” corresponds to the fuel  124  in  FIG. 18 , and “high concentration fuel” corresponds to the high concentration fuel  1523  in  FIG. 18 . 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 area in 
               
               
                   
                   
                   
                 contact with 
               
               
                   
                   
                   
                 vaporized 
               
               
                   
                 fuel 
                 high concentration fuel 
                 fuel (cm 2 ) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Ex. 1 
                 5 vol % MeOHaq. 
                 MeOH 
                 5 
               
               
                   
                 23 ml 
                 5 ml 
               
               
                 Ex. 2 
                 5 vol % MeOHaq. 
                 solid fuel 5 g 
                 10 
               
               
                   
                 23 ml 
                 (equivalent to MeOH 6 ml) 
               
               
                 Comp. 
                 5 vol % MeOHaq. 
                 — 
                 5 
               
               
                 Ex. 
                 28 ml 
               
               
                   
               
            
           
         
       
     
       FIG. 19  is a graph showing a relationship between the power generation time and the voltage. From  FIG. 19 , it was confirmed that a stable output property was exhibited for longer than 10 hours in any cases where pure methanol or solid methanol fuel were used as the high concentration fuel  1523 . On the other hand, in the comparative example, although the used amount of methanol itself was equivalent to that of the examples, the supply of methanol from the high concentration fuel  1523  was not performed, as a result of which the voltage drop after the start of power generation was significant. 
     From the above results, it was confirmed that the fuel cell could be stably operated for a long period of time, by supplying fuel in such a manner that high concentration fuel  1523  was used so as to be once vaporized and then dissolved in fuel  124 .