JP2005228687A - Air-breathing type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell and a direct methanol fuel cell which can keep the wetness of a proton conductive membrane in an appropriate state, even when the outside air is dry, and to reduce the waste of fuel for the direct type methanol fuel cell. <P>SOLUTION: As shown in Figure 2, an air-breathing fuel cell comprises a fuel electrode 30, an air electrode 31, a proton conductive membrane 23 sandwiched in between the fuel electrode and the air electrode, and an openable and closable door mounted on an air intake to the air electrode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell as a power source for portable devices, and more specifically to an air breathing type fuel cell having no auxiliary equipment such as a pump for sending air.

  In recent years, portable electronic devices such as mobile phones and notebook personal computers (hereinafter abbreviated as notebook personal computers) are required to be light and small, and to be used for a long time. For this reason, there is a need for a power source that is lightweight and compact and has a high energy density. Lithium ion secondary batteries with high energy density are currently popular as such power sources, but in addition to these, fuel cells that generate electricity by electrochemical reactions are also attracting attention. Among them, a polymer membrane such as a perfluorocarbon sulfonic acid membrane is used as a proton conductive membrane, and a solid polymer fuel cell (hereinafter abbreviated as PEFC) using hydrogen gas as fuel, or a direct methanol fuel cell using methanol aqueous solution as fuel. (Hereinafter abbreviated as DMFC) is expected as a power source capable of realizing a higher energy density than a lithium ion secondary battery.

Up is a fuel cell that generates electricity by consuming oxygen in the air electrode, the PEFC or DMFC, even fuel cell air breathing type using no auxiliary such pump for sending air, about 48 mW / cm ² of Power generation can be performed at a power density (see Patent Document 1).
JP 2003-317745 A

  In the fuel cell as described above, during power generation at a high output, a large air intake is necessary so that a large amount of oxygen can reach the air electrode. The air intake port of the fuel cell described in Patent Document 1 is always open and has a structure suitable for high-power operation. However, when a fuel cell is used as a power source for an electronic device, not only high output operation but also operation states such as rest and low output operation occur. In the fuel cell described in Patent Document 1, since the opening degree of the air intake port cannot be adjusted, the following problems occur.

  Proton conductivity is highly dependent on the wet state of the proton conducting membrane. Since water is generated at the air electrode during high power operation, the proton conductive membrane can be maintained in a wet state. However, when the outside air is dry and the air intake port remains fully open in a resting state or a low-power operation state, the proton conductive membrane is dried and the proton conductivity is lowered. For this reason, internal resistance increases at the time of the next starting and driving | operation, and an output may fall.

In the case of DMFC, further, a cross leak, which is a phenomenon in which a methanol aqueous solution of fuel permeates through the proton conductive membrane from the fuel electrode to the air electrode, is generated. The cross-leaked methanol reacts if there is oxygen in the air electrode, and becomes water and carbon dioxide. One of the driving forces for the cross leak of the aqueous methanol solution is a methanol concentration gradient between the fuel electrode and the air electrode.
If the opening of the air intake port cannot be adjusted, oxygen will continue to be supplied to the air electrode. As a result, the aqueous methanol solution is consumed by the reaction on the air electrode side, and the concentration of methanol at the air electrode is reduced. For this reason, the methanol aqueous solution always cross-leaks from the fuel electrode to the air electrode. This cross leak of the methanol aqueous solution continues until the difference in concentration between the fuel electrode and the air electrode becomes almost zero.

  Even if the opening of the air intake cannot be adjusted, if the fuel cell is operated at a high output, the amount of methanol that cross-leaks and reacts on the air electrode side will be smaller than the amount of methanol consumed in power generation. . However, when the fuel cell is in a resting state or a low-power operation state, the amount of methanol that cross-leaks and reacts on the air electrode side is relatively larger than the amount of methanol consumed by power generation. Accordingly, the amount of fuel that can be converted into electric power is reduced.

  In view of the above, an object of the present invention is to provide a fuel cell that can maintain the wet state of the proton conductive membrane in an appropriate state and can further suppress waste of fuel.

  The present invention is provided in (1) a fuel electrode, (2) an air electrode, (3) a proton conductive membrane sandwiched between the fuel electrode and the air electrode, and (4) an air intake port to the air electrode. The present invention relates to a fuel cell comprising an openable / closable door (or gate). Thereby, the proton conductivity in the proton conductive membrane can be controlled, and in the case of DMFC, the cross leak of the fuel can be controlled within a certain range.

  The fuel cell preferably further includes control means for controlling the opening degree of the openable / closable door according to at least one of an output density and a current density of the fuel cell. Thereby, the controllability of proton conductivity and the controllability of cross leak can be improved.

In the fuel cell, it is preferable that the openable / closable door is a stable door composed of a plurality of rotatable blades arranged in parallel. Moreover, you may comprise the door which can be opened and closed from several sliding doors. Thereby, the opening degree of the door can be controlled with a simple configuration.
Further, in each of the plurality of slats, it is more preferable that at least one type of packing selected from the group consisting of chloroprene rubber and fluororubber is disposed on the edge thereof. Thereby, the sealing performance of a door can be improved.

  The present invention also relates to a portable electronic device equipped with the fuel cell as described above. By using the fuel cell according to the present invention, output stabilization and high fuel utilization are achieved, so that the reliability of the portable electronic device can be improved and the portable electronic device can be used for a long time. Enables widespread use.

  According to the present invention, since the proton conductivity of the proton conducting membrane can be kept high when the fuel cell is in a rest state and a low output operation state, it is possible to suppress a decrease in output during the next start-up and operation. Furthermore, it is possible to suppress wasteful consumption of fuel in the resting state and the low output operation state.

Embodiment 1
The fuel cell of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view of a notebook computer equipped with a fuel cell according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the power generation unit of the fuel cell according to the embodiment of the present invention.
In the present embodiment, the fuel cell includes a fuel electrode, an air electrode, and a power generation unit including a membrane electrode assembly including a proton conductive membrane sandwiched between the fuel electrode and the air electrode, and the air electrode and the outside. It consists of an openable / closable door (or gate) provided in a communicating opening.

  As shown in FIG. 2, the power generation unit 20 of the fuel cell includes a membrane electrode assembly including a fuel electrode 30, an air electrode 31, and a proton conductive membrane 23 sandwiched between the fuel electrode 30 and the air electrode 31. Is provided. The fuel electrode 30 includes a catalyst layer 21 and a diffusion layer 24, and the diffusion layer 24 includes a porous carbon sheet. The air electrode 31 includes a catalyst layer 22 and a diffusion layer 27, and the diffusion layer 27 includes a porous carbon sheet having water repellency.

A carbon separator 25 is laminated on the diffusion layer 24 on the fuel electrode side, and a plurality of grooves 26 through which fuel flows are formed on the carbon separator 25 on the side in contact with the diffusion layer 24.
A metal sheet 28 is laminated on the diffusion layer 27 on the air electrode side, and a plurality of holes 29 through which air passes are formed in the metal sheet 28.

The catalyst layers 21 and 22 are made of carbon carrying a catalyst. As the catalyst and carbon, those known in the art can be used. As the porous carbon sheet and the proton conductive membrane, those known in the art can be used.
However, since the fuel cell of the present invention may use hydrogen gas or a methanol aqueous solution as the fuel, it is necessary to select a fuel electrode or the like depending on the type of fuel used.

Next, the openable / closable door provided at the air inlet to the air electrode will be described.
This openable / closable door is provided in an opening that communicates the air electrode with the outside, and as shown in FIG. It consists of the attached door 13. Here, the wing board 14 is arrange | positioned so that it may open in the left-right direction.

  A fuel cell having a power generation unit shown in FIG. 2 is installed in the lid portion 11 of the notebook computer 10 shown in FIG. At this time, the fuel electrode is disposed on the display 12 side, and the air electrode is disposed on the back side of the lid portion 11. A keyboard or the like is mounted on the main body 15 of the notebook computer.

Next, FIG. 3 shows a cross-sectional view taken along the line II of FIG. Here, FIG. 3 (a) shows a state where the armored door is closed, and FIG. 3 (b) shows a state where the armored door is fully open.
The plurality of slats 14 are arranged so as to be pivotable in parallel and around the axis 32.
In a state where the wing plate 14 is closed, the wing plate 14 overlaps with other wing plates, and a packing 33 is disposed in the overlapping portion. Here, as the packing, it is preferable to use at least one rubber selected from the group consisting of chloroprene rubber and fluororubber. Thereby, the sealing performance when the open door is closed can be improved.

  In the present invention, the opening degree of the armor door 13 is adjusted according to the output state of the fuel cell. That is, when the fuel cell is in a resting state, the stable door 13 is closed, and the opening degree of the stable door 13 increases as the operation output increases. And the opening degree becomes the maximum in the state operated with the maximum output.

  That is, when the fuel cell is in a resting state, the wing plate is in a closed state as shown in FIG. As the output of the fuel cell increases, the slat 14 pivots about the axis 32 and the angle of the slat 14 relative to the back of the notebook computer display gradually increases. Thereby, the opening degree of a stable door increases. In a state where the fuel cell is operated at the maximum output, as shown in FIG. 3B, the angle of the slats is 90 ° with respect to the back surface, and the opening degree of the stable door is maximized.

  As described above, when the fuel cell is operated in a high output state, water is generated at the air electrode, so that the proton conductive membrane can be maintained in a wet state. However, when the outside air is dry, if the opening of the air intake port cannot be adjusted in a resting state or a low power operation state, the proton conductive membrane is dried and proton conductivity is lowered. In the present invention, as described above, a door that can be opened and closed such as an open door that communicates between the air electrode and the outside is provided, and the door is closed in a resting state, and low-power operation is performed. In the state, the opening of the door is reduced. This reduces the contact between the proton conducting membrane and the outside air, so that the proton conducting membrane is kept moist even in a resting state or a low power operation state where the amount of water generated at the air electrode is small. It becomes possible to do.

  In particular, in a conventional DMFC using a methanol aqueous solution as a fuel, the amount of methanol that cross-leaks and reacts on the air electrode side in a resting state or low-power operation state is relatively large compared to the amount of methanol consumed in power generation. Thus, the amount of fuel that can be converted into electric power is reduced. However, according to the present invention, the opening degree of the door that can be opened and closed can be reduced in the resting state and the low-power operation state, so that the amount of oxygen supplied to the air electrode is limited. Thereby, the quantity of methanol which cross leaks and reacts on the air electrode side can be reduced. Therefore, wasteful consumption of methanol as a fuel can be prevented.

Next, a method for controlling the opening degree of the door that can be opened and closed will be described.
Control of the opening degree of the door is performed by control means for controlling the opening degree of the door according to at least one of the output density and the current density of the fuel cell. For example, a power supply control unit incorporated in a notebook personal computer can be used as the control means.

In the present embodiment, it is preferable that the power supply control unit not only adjusts the opening degree of the door that can be opened and closed, but also controls the power generation of the fuel cell, its output density, current density, and the like. Thereby, the opening degree of a door can be controlled according to the output density, current density, etc. of the fuel cell.
The power control unit preferably includes a rechargeable power source such as a secondary battery or a capacitor. This makes it possible to operate the power supply control unit itself even when the fuel cell is not operating.

Next, when the door that can be opened and closed is a stable door, an example of a drive unit for moving a slat constituting the stable door will be described with reference to FIG.
The drive unit 40 shown in FIG. 4 includes a motor 43, a shaft 44 that is an axis of the motor 43, and a ball screw 45 attached to the shaft 44. Further, the vane 41 is provided with a gear 46 that engages with the ball screw 45 at the end opposite to the side on which the packing 42 is attached. The gear 46 is supported by, for example, a bearing (not shown).

  The operation of the motor 43 can be controlled by the power supply control unit. When the motor 43 is operated by the power supply control unit, the shaft 44 rotates, and thereby the ball screw 45 attached to the shaft 44 also rotates. By rotating the ball screw 45, the gear 46 engaged with the ball screw 45 rotates. This increases the angle of the slats with respect to the back of the display, as shown in FIG. Therefore, it is possible to adjust the angle of the slats, that is, the opening degree of the stable door, by adjusting the operating time of the motor, the rotation direction, and the like.

  In this embodiment, as shown in FIG. 1, the wing plate 14 opens left and right, but as shown in FIG. 5, the same effect can be obtained even when the wing plate 14 opens up and down. can get. Here, FIG. 5 is a perspective view of a notebook computer equipped with a fuel cell according to another embodiment of the present invention.

Next, the supply of fuel to the fuel cell will be described.
The fuel is supplied from the fuel tank to the fuel cell. At this time, it is preferable that the fuel supply speed, the supply amount, and the like are controlled by the power supply control unit in accordance with the output density of the fuel cell.

  As described above, hydrogen gas or methanol aqueous solution is used as the fuel. In particular, when the fuel is hydrogen gas, it is preferable to use a hydrogen storage alloy that can store and release hydrogen gas in order to improve safety and the amount of hydrogen gas that can be stored. An example of the hydrogen storage alloy is TiCrV-based hydrogen storage alloy (specific gravity: 4.5). This TiCrV-based hydrogen storage alloy can store 2.0 wt% hydrogen gas of its own weight. This hydrogen storage alloy is accommodated in a fuel tank.

In addition, the fuel tank may be, for example, a portion in which a battery pack of a conventional laptop computer is inserted (for example, the inside of the main body, the joint between the lid and the main body) so that the fuel can be supplied to the fuel tank. It is preferable to be arranged in a portion or the like.
The fuel cell preferably has a pump for supplying fuel from the fuel tank to the fuel electrode. This pump is also preferably controlled by a power supply control unit.

  Further, the power generation by the fuel cell may be performed not only to operate the notebook personal computer but also to charge a secondary battery or the like included in the power supply control unit. Furthermore, the operation of the personal computer may use the secondary battery or the like, or may use electric power from the fuel cell. Furthermore, you may use both a secondary battery and a fuel cell for the operation | movement of a notebook personal computer.

  In addition, when a secondary battery is charged using a fuel cell, the power generation output of the fuel cell may be reduced as the charge amount of the secondary battery increases.

  Also, the output of the fuel cell increases as the voltage decreases, for example, up to about 0.5 V when the fuel is hydrogen and up to about 0.3 V when the fuel is methanol. When it becomes smaller than that, the output of the fuel cell decreases. Therefore, the output of the fuel cell is controlled by changing the voltage output to the power supply control unit.

  In addition, after using the notebook computer and performing the termination process, the secondary battery included in the power supply control unit may be charged by power generation by the fuel cell. Also in this case, as described above, the power generation output of the fuel cell may be reduced as the charge amount of the secondary battery increases.

Embodiment 2
Next, the case of having an openable / closable door composed of a plurality of sliding doors will be described with reference to FIGS. Here, FIG. 6 is a perspective view of a notebook computer equipped with a fuel cell according to another embodiment of the present invention, and FIG. 7 is a cross-sectional view taken along the line AB of FIG.
In the present embodiment, the door that can be opened and closed includes a plurality of sliding doors 62 and a plurality of windows 63 opened in the casing on the back of the notebook computer, as shown in FIGS. 6 and 7. In addition, the window disposed between the upper and lower windows is spaced about the same as the width of the sliding door, so that the vertical width of the window is slightly narrower than the vertical width of the sliding door. ing. Furthermore, when the window is closed by the sliding door, the surface facing the window frame of the sliding door is edged by the packing 64 in order to improve the sealing performance. Also in this case, it is preferable to use at least one rubber selected from the group consisting of chloroprene rubber and fluororubber as the packing.

  Also in this embodiment, when the fuel cell is in a resting state, the window is closed by the sliding door. As the output of the fuel cell increases, the sliding door is slid downward and the window is opened. When operating at maximum power, the window is fully opened. Also in this case, the opening and closing of the window by sliding the sliding door is controlled by the power supply control unit according to the output state of the fuel cell.

  The sliding door can be slid using, for example, a drive unit as shown in FIG. In this case, it is possible to slide the sliding door by putting a horizontal groove on the display side surface of the sliding door, engaging the ball screw in this groove, and rotating the ball screw.

  When opening and closing a door using a sliding door as in this embodiment, compared with the case where the above-mentioned door is used, a width that can accommodate the sliding door between the windows is required. The area occupied by the opening is reduced. However, unlike external doors, the external size does not change. For example, it is effective for portable electronic devices that have a dimensional constraint on the back of a notebook computer or that require that the external size does not change. is there.

Embodiment 3
Next, the case where the slats are driven by a shape door using a shape memory alloy will be described with reference to FIG. Here, FIG. 8 is a schematic view showing a drive mechanism of a stable door using a coil spring and a shape memory alloy coil.

In the case of the present embodiment, the drive unit includes a fixture 83, a shaft 84, a coil spring 85, a first coil 86, and a second coil 87.
The fixture 83 is fixed to, for example, a door frame that can be opened and closed. A plurality of slats 81 are rotatably fixed to the fixture 83 at predetermined positions in the slat length direction.
One end portion of the plurality of blades 81 is rotatably attached to the shaft 84 over the length direction. Furthermore, one end of a coil spring 85, a first coil 86, and a second coil 87 is attached to one end of the shaft 84. The other end of the coil spring 85 is fixed to the door frame.

  The first coil 86 and the second coil 87 are made of a shape memory alloy, and a rod-shaped heater (not shown) for heating is incorporated in the hollow portions of the spiral coils 86 and 87. When the first coil 86 or the second coil 87 is heated by the heater, they extend. In addition, the 1st coil 86 and the 2nd coil 87 are each arrange | positioned in the orthogonal direction, as FIG. 8 shows. A packing 82 is disposed at the end of the wing plate 81 opposite to the side on which the shaft 84 is attached.

  When the fuel cell is in a resting state, as shown in FIG. 8A, the armored door is closed due to the tension of the coil spring 85. When the fuel cell is in a low power operation state, the first coil 86 is extended and the shaft 84 is moved by operating the heater built in the core of the first coil to heat the first coil. . Due to the movement of the shaft 84, the wing plate 81 is rotated, and as shown in FIG. When the fuel cell is in a high output operation state, when the heater built in the core of the second coil is further operated to heat the second coil, the second coil is extended and the shaft 84 is further extended. Moving. Thereby, as shown in FIG.8 (c), the opening degree of a stable door becomes the maximum. Such heating by the heater of the first coil or the second coil by the heater is controlled by the power supply control unit in accordance with, for example, the output density of the fuel cell.

  When the operation state of the fuel cell changes from the high output operation state to the low output operation state, the heating of the second coil is stopped. The second coil is naturally cooled, the second coil is contracted, and the shaft is now moved in the opposite direction, so that the opening of the stable door is reduced. Further, when the heating of the first coil is stopped, the first coil is contracted and returned to the rest position by the tension of the coil spring, so that the armor door is closed. In this way, it is possible to open and close the open door with a simple configuration using a coil spring and a coil made of a shape memory alloy.

  Therefore, in this embodiment, the opening degree of the stable door can be changed in three stages such as 0%, 50%, and 100% by using the coil spring and the coil made of the shape memory alloy. . For example, when the secondary battery in the power supply control unit is charged using a fuel cell, when the charge amount of the secondary battery is 95%, the fuel cell is stopped and the charge amount is 30 to 95%. If the charging amount is less than 30%, the power is generated at 100% output. At this time, when the fuel cell is in a resting state, the opening of the stable door is set to 0%, and when power generation is performed at an output of 50%, the opening of the stable door is set to 50% and the output of 100% When power generation is performed, the opening degree of the stable door is set to 100%, so that the opening degree of the stable door can be adjusted according to the output of the fuel cell, and the fuel cell can be operated efficiently.

  Moreover, since the fuel cell of the present invention is an air breathing type, the output density cannot be increased as much as the forced air supply type. However, it is sufficiently possible to use it in a portable electronic device that consumes little power. For this reason, as shown in FIG. 9, a fuel cell including an openable / closable door composed of a stable door 92 can be mounted on the mobile phone 91.

  The present invention will be described in detail based on the following examples.

In this example, a polymer electrolyte fuel cell using hydrogen gas as a fuel was produced.
First, a power generation unit as shown in FIG. 2 was produced as follows.
A catalyst layer made of platinum-supported carbon was formed on both sides of a proton conductive membrane (Nafion 117 membrane: manufactured by DuPont). Next, a diffusion layer made of a porous carbon sheet was laminated on one catalyst layer to obtain a fuel electrode. Next, a diffusion layer made of a porous carbon sheet having water repellency was laminated on the other catalyst layer to produce a membrane electrode assembly (hereinafter abbreviated as MEA) as an air electrode. On the MEA fuel electrode, a carbon separator having a groove formed as a flow path on one surface was disposed. At this time, the carbon separator was disposed so that the surface on which the groove was formed was in contact with the porous carbon sheet.
Next, a metal sheet having a plurality of holes was arranged on the air electrode of the MEA to produce a power generation unit as shown in FIG.

  Next, on the metal sheet on the air electrode side, a frame provided with an openable / closable door such as that shown in FIG. 1 was attached to produce a fuel cell. At this time, the slats constituting the armored door can be driven using a drive unit as shown in FIG.

  The fuel cell obtained as described above was arranged on the back of the display of a notebook computer as shown in FIG.

  Hydrogen gas as a fuel was stored in 113 g of a TiCrV hydrogen storage alloy (specific gravity: 4.5) placed in a fuel tank having an internal volume of 50 cc. Since this TiCrV hydrogen storage alloy can store 2.0 wt% hydrogen gas of its own weight, the amount of hydrogen gas that can be stored in the TiCrV hydrogen storage alloy 113 g was about 2.3 g.

Next, a graph showing the relationship between the output density and the current density of the manufactured fuel cell is shown in FIG.
As shown in FIG. 10, the obtained fuel cell was able to generate power at a maximum power density of 0.05 W / cm ² . Therefore, since the area of the power generation unit is 140 cm ² , it can be seen that this fuel cell was able to generate power with a maximum output of 7 W. As described above, since about 2.3 g of hydrogen gas is present in the fuel tank, the produced fuel cell has an electric energy of about 33 Wh without supplying fuel from the outside when generating power at the maximum output. Can generate electricity.

  Since the DC-DC converter is passed to perform voltage control, when the fuel cell generates power with 100% output (that is, 7 W output), the average conversion efficiency is 90%. The fuel cell had the ability to supply 6.3 W.

(Power generation test)
In a dry environment with a temperature of 25 ° C. and a humidity of 20% RH, the fuel cell obtained as described above (cell 1) and a conventional fuel cell in which the opening of the air intake port cannot be adjusted as a comparison (comparative cell 1) Was tested. Here, the power generation unit of the comparative battery 1 was the same as the power generation unit of the battery 1. In addition, the area of the air intake port of the comparative battery 1 was set to be the same as the area of the opening when the opening degree of the stable door of the fuel cell of the present invention was the maximum.
FIG. 11 shows the relationship between the current density and the single cell voltage of the battery 1 (A) and the comparative battery 1 (B) when left standing for 2 hours and then generating power.

As shown in FIG. 11, the comparative battery 1 had a single cell voltage lower than that of the battery 1 at the same current density. This is presumably because the proton conducting membrane is dried because the opening of the air intake port cannot be adjusted, so that the proton conductivity is lowered and the internal resistance is increased. Further, the comparative battery 1 did not improve the internal resistance even when power generation was continued.
On the other hand, the battery 1 could be operated at a high output and could be operated stably without increasing the internal resistance during the operation. Therefore, according to the present invention, it is understood that the proton conductive membrane can be maintained in a wet state, and therefore, the proton conductivity can be maintained high.

In this example, a direct methanol fuel cell was produced.
A fuel cell was prepared and attached to a notebook computer in the same manner as in Example 1 except that a fuel electrode containing platinum ruthenium-supported carbon as a catalyst and an air electrode containing platinum-supported carbon as a catalyst were used. Here, the area of the power generation unit was 320 cm ² .

  In this example, a methanol aqueous solution having a concentration of about 10% by weight (3 mol / L), which is a fuel, was accommodated in a fuel tank having an internal volume of 330 cc.

Next, a graph showing the relationship between the output density and the current density of the produced fuel cell is shown in FIG.
As shown in FIG. 12, the obtained fuel cell was able to generate power at a maximum power density of 0.022 W / cm ² . Moreover, since the area of the power generation unit is 320 cm ² , this fuel cell was able to generate power with a maximum output of about 7 W. As described above, since the fuel tank can contain 330 cc of methanol aqueous solution of fuel, the produced fuel cell theoretically does not supply fuel from the outside when generating power at the maximum output. Can generate an electric energy of about 60 Wh. However, in DMFC, after methanol cross-leaks, it reacts and is consumed at the air electrode, so the amount of power generated is smaller than the theoretical value. Further, since the amount of methanol consumed varies depending on the operating state of the fuel cell, the amount of power generated depends on the operating state of the fuel cell.

  Since the DC-DC converter is passed to perform voltage control, when the fuel cell generates power with 100% output (that is, 7 W output), the average conversion efficiency is 90%. The fuel cell had the ability to supply 6.3 W.

(Power generation test)
In a dry environment with a temperature of 25 ° C. and a humidity of 20% RH, the fuel cell obtained as described above (cell 2) and a conventional fuel cell in which the opening of the air intake port cannot be adjusted as a comparison (comparative cell 2) Was tested. Here, the power generation unit of the comparative battery 2 was the same as the power generation unit of the battery 2. In addition, the area of the air intake port of the comparative battery 2 was set to be the same as the area of the opening when the opening degree of the stable door of the fuel cell of the present invention was the maximum.
FIG. 13 shows the relationship between the current density and the single cell voltage of the battery 2 (C) and the comparative battery 2 (D) when the battery 2 (C) and the comparative battery 2 (D) are left to stand for 2 hours and then generate power.

As shown in FIG. 13, the comparative battery 2 had a single cell voltage lower than that of the battery 2 at the same current density. This is presumably because the proton conducting membrane is dried because the opening of the air intake port cannot be adjusted, so that the proton conductivity is lowered and the internal resistance is increased. Further, the comparative battery 2 did not improve the internal resistance even when power generation was continued.
Furthermore, in the comparative battery 2, when the concentration of the methanol aqueous solution filled in the flow path (volume 20 cc) of the carbon separator of the fuel electrode was measured during the rest of 2 hours before power generation, the concentration was 0.1 mol. / L. As a result, about 97% of methanol in the flow path (about 6 mol% of methanol contained in the whole 330 cc) was wasted.

On the other hand, the battery 2 of the present invention could be operated at a high output, and could be stably operated without increasing the internal resistance during the operation. That is, as in the case of the battery 1, it can be seen that the proton conductivity of the proton conductive membrane is maintained high.
Furthermore, when the measurement was performed in the same manner as the comparative battery 2, the wasteful consumption of fuel in the battery 2 was reduced. This was investigated in more detail as follows.

(Cross leak test)
For comparison, the battery 2 and the conventional fuel cell (comparative battery 3) in which the area of the comparative battery 2 and the air intake port is half of that of the comparative battery 2 are used. The operation was changed to 50% power generation, shutdown, and 100% power generation. The flow rate / concentration of the aqueous methanol solution at the fuel electrode outlet at that time was measured for each of the three types of fuel cells, and the amount of methanol that cross-leaked and reacted with oxygen at the air electrode was obtained. The 100% power generation means power generation at an output of 7W. The power generation unit of the comparative battery 3 was the same as the power generation unit of the battery 2.

The results obtained for battery 2, comparative battery 2 and comparative battery 3 are shown in FIGS. 14, 15 and 16, respectively. 14 to 16, the amount of reacted methanol was converted into current density for easy comparison with the current value (conversion formula: 1 g / cm ² · sec = 96485 × 6/32 = 189090 A / cm ^2). ).

In the case of the battery 2 of the present invention, as shown in FIG. 14, the amount of methanol cross-leaked and reacted at the air electrode is zero and 7 W (100%) power generation in the rest state when converted into current density. In this case, it was 0.02 A / cm ² , and in the case of 3.5 W (50%) power generation, it was 0.04 A / cm ² .

On the other hand, in the case of the comparative battery 2, as shown in FIG. 15, the amount of methanol cross-leaked and reacted at the air electrode is 0.12 A / cm ² and 7 W power generation in the rest state when converted to current density. Was 0.02 A / cm ² in the case of, and 0.09 A / cm ² in the case of 3.5 W power generation.
In the case of the comparative battery 3, as shown in FIG. 16, the amount of methanol cross-leaked and reacted at the air electrode is 0.09 A / cm ² and 7 W power generation in the rest state when converted into current density. Was 0.02 A / cm ² , and 0.07 A / cm ² in the case of 3.5 W power generation.

  As described above, after cross leaking, methanol that reacts with oxygen at the air electrode can be brought to zero in a resting state in the present invention. In addition, even when generating power at a low output, wasteful consumption of methanol could be greatly reduced. Therefore, it can be seen that the present invention can suppress wasteful consumption of fuel.

  The fuel cell of the present invention is useful as a power source for lightweight and small portable electronic devices.

1 is a perspective view of a notebook computer equipped with a fuel cell according to an embodiment of the present invention. It is a schematic block diagram which shows the electric power generation part of the fuel cell of this invention. Sectional drawing in the II line | wire of FIG. 1 is shown. An example of the drive part for moving a slat is shown. The perspective view of the notebook computer equipped with the fuel cell concerning another embodiment of the present invention is shown. The perspective view of the notebook personal computer equipped with the fuel cell concerning another embodiment of this invention is shown. Sectional drawing in the AB line | wire of FIG. 6 is shown. It is the schematic which shows the drive mechanism of the armor door which uses a coil spring and a shape memory alloy coil. 1 is a perspective view of a mobile phone equipped with a fuel cell according to an embodiment of the present invention. 4 is a graph showing the relationship between the power density and the current density of the fuel cell used in Example 1. It is a graph which shows the relationship between the voltage of a single cell after leaving it to stand in a dry environment for 2 hours, and current density. It is a graph which shows the relationship between the power density of the fuel cell used in Example 2, and current density. It is a graph which shows the relationship between the voltage of a single cell after leaving it to stand in a dry environment for 2 hours, and current density. It is a graph which shows the amount of methanol which reacted with oxygen in an air electrode when fluctuating the fuel cell concerning the present invention with 100% power generation, 50% power generation, rest, and 100% power generation. It is a graph which shows the amount of methanol which reacted with oxygen in the air electrode, when the conventional fuel cell which has the air intake of a predetermined | prescribed area is fluctuate | varied with 100% power generation, 50% power generation, a rest, and 100% power generation. It is a graph which shows the amount of methanol which reacted with oxygen in an air electrode when fluctuating the conventional fuel cell which made the area of an air intake small into 100% power generation, 50% power generation, a stop, and 100% power generation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Notebook-type personal computer 11 Cover part 12 Display 13, 92 Armored door 14, 41, 81 Wing board 15 Main part 20 Power generation part 21 Fuel electrode side catalyst layer 22 Air electrode side catalyst layer 23 Proton conductive film 24 Fuel electrode Side diffusion layer 25 Carbon separator 26 Groove 27 Air electrode side diffusion layer 28 Metal sheet 29 Hole 30 Fuel electrode 31 Air electrode 32 Shaft 33, 42, 64, 82 Packing 40 Drive part 43 Motor 44 Shaft 45 Ball screw 46 Gear 62 Sliding door 63 Window 83 Fixing tool 84 Shaft 85 Coil spring 86 First coil 87 Second coil 91 Mobile phone

Claims (8)

(1) Fuel electrode,
(2) air electrode,
(3) A fuel cell comprising: a proton conductive membrane sandwiched between the fuel electrode and the air electrode; and (4) an openable / closable door provided at an air intake port to the air electrode.   The fuel cell according to claim 1, further comprising control means for controlling the opening degree of the door that can be opened and closed in accordance with at least one of an output density and a current density of the fuel cell.   3. The fuel cell according to claim 2, wherein the control means controls the opening degree of the door that can be opened and closed so that the proton conductivity of the proton conductive membrane is maintained within a certain range.   3. The fuel cell according to claim 2, wherein the control means controls the opening degree of the door that can be opened and closed so as to maintain a permeation amount of fuel in the proton conductive membrane within a certain range.   2. The fuel cell according to claim 1, wherein the openable / closable door is a flexible door including a plurality of pivotable blades arranged in parallel.   The fuel cell according to claim 1, wherein the openable / closable door includes a plurality of sliding doors.   The packing of at least one selected from the group consisting of chloroprene rubber and fluororubber is arranged at the edge of each of the plurality of slats or the plurality of sliding doors. Fuel cell.   A portable electronic device equipped with the fuel cell according to claim 1.

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