JP2000353533A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell capable of smoothly vaporizing and supplying liquid fuel with a simple structure without using a pump or a blower or the like and providing stable and high output. SOLUTION: In this fuel cell having an electrolyte plate 1, an oxidizer electrode 3 and a fuel electrode 2 provided on faces opposing this electrolyte plate 1, and a liquid fuel holding part 6 holding fuel supplied to the fuel electrode 2, gaseous fuel is introduced to the fuel electrode 2 without using a pump or a blower by vaporizing the fuel held by the liquid fuel holding part 6 with reaction heat of a cell reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell, and more particularly to a fuel cell suitable for miniaturization.

[0002]

2. Description of the Related Art Fuel cells have recently attracted attention because of their high efficiency as a single power generation device. Fuel cells include phosphoric acid type fuel cells using gas as fuel, molten carbonate type fuel cells, solid electrolyte type fuel cells, alkaline electrolyte type fuel cells, etc., as well as methanol fuel cells using liquid as fuel, and hydrazine fuel. It is roughly divided into batteries and the like. Since these fuel cells are mainly intended for power generators and power sources for operating large equipment, compressors and pumps for introducing gas or liquid fuel or oxidizing gas into the cells are used. Are required, and not only is the system complicated, but also consumes power for these introductions.

On the other hand, as a social trend, various devices such as OA devices, audio devices, and wireless devices are required to be miniaturized with the development of semiconductor technology and to be more portable. As a power source for satisfying such a demand, a simple primary battery or a secondary battery is used. However, the primary battery and the secondary battery are functionally limited in use time, and the use time is naturally limited in OA equipment and the like using such a battery. When a primary battery is used, after the battery is discharged, the battery can be replaced and the OA equipment can be moved, but the use time is short with respect to its weight, and it is not suitable for portable equipment. In addition, the secondary battery can be charged after the discharge, but has a drawback that not only the power source is required for charging, the place of use is restricted, but also the charging takes time. As described above, in order to operate various small devices for a long time, it is difficult to cope with the extension of the conventional primary battery and secondary battery, and a battery suitable for longer operation is required.

[0004] One solution to such a problem is the fuel cell as described above. Fuel cells not only have the advantage of being able to generate power simply by supplying fuel and oxidant, but also have the advantage of being able to generate power continuously if only the fuel is replaced. For example, it can be said that the system is extremely advantageous for the operation of small devices such as OA devices with low power consumption.

[0005] Since air can be used as an oxidizing agent in a fuel cell, there is no restriction on the place or time of use from the viewpoint of the oxidizing agent. Although the power consumption is small, the volume of gas required for power generation is large considering the gas density, which is not suitable for miniaturization of batteries. On the other hand, liquid fuel has a higher density than gas, and is overwhelmingly advantageous as a fuel for a fuel cell for a small device. Therefore, if the size of a fuel cell using a liquid fuel can be reduced, a power supply for a small device that can be operated for a long time, which has not been available in the past, can be realized. Obstacles in realizing such a small device power supply are, as described above,
A conventional system using a liquid fuel requires a pump, a blower, and the like to feed the liquid fuel into the battery body. Therefore, the system is complicated, and it is difficult to reduce the size with the structure as it is.

A description will be given of a methanol fuel cell using methanol as a liquid fuel as an example. Methanol fuel cells are roughly classified into a liquid supply type in which liquid fuel is supplied to the cell body as it is and a vaporization supply type in which vaporized methanol is supplied to the cell body, depending on a method of supplying fuel to the cell body.

In a liquid supply type system, a liquid fuel is circulated by pumping a liquid fuel between a methanol tank and a battery body. For this reason, a pump is required in addition to the battery main body, which is not suitable for downsizing the device. In addition, since the electrode reaction is performed between the fuel and the liquid fuel, there is a problem that the activation is reduced and the performance is reduced as compared with the case where the electrode reaction is performed by vaporizing methanol. Furthermore, when a proton conductive solid polymer membrane such as perfluorosulfonic acid (trade name: manufactured by Nafion Du Pont) is used as an electrolyte, a liquid organic fuel such as methanol permeates to the oxidant electrode side. There is also the problem of over.

[0008] In the case of the vaporization supply type, there is known a method in which liquid fuel conventionally pumped from a methanol tank is vaporized once, and the vaporized fuel is supplied to a battery body by a blower. However, also in this method, it is necessary to separately provide an auxiliary device such as a carburetor, which causes a problem that the size of the device is increased.

A fuel cell is usually used in the form of a stack in which a plurality of unit cells are stacked, but when fuel is pumped by a pump or a blower, the distribution of the fuel in the stacking direction becomes non-uniform.
There is a problem that the performance of the cells constituting the stack varies.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional fuel cell and to provide a small fuel cell useful as a power source for small equipment. It is an object of the present invention to provide a fuel cell which simplifies a system and supplies a fuel vaporized with a simple structure to a fuel electrode, thereby enabling downsizing while maintaining high performance.

[0011]

According to a first aspect of the present invention, there is provided an electrolyte plate, an oxidizer electrode and a fuel electrode provided on opposing surfaces of the electrolyte plate, and a liquid fuel for holding fuel to be supplied to the fuel electrode. A fuel cell having a holding section, wherein the fuel held in the liquid fuel holding section is vaporized by reaction heat of a cell reaction.

With such a configuration, the cell reaction at the fuel electrode can be made a reaction with the vaporized fuel, a highly active reaction can be achieved, and perfluorosulfonic acid (trade name: Nafion) Methanol crossover, which is a problem when a proton-conductive solid polymer membrane such as DuPont) is used as an electrolyte and a liquid organic fuel such as methanol is used as a fuel.

Further, since the liquid fuel is vaporized by utilizing the reaction heat generated in the battery reaction, an auxiliary device such as a vaporizer is not necessarily required, and the apparatus can be downsized.

More specifically, an oxidant electrode, an electrolyte plate laminated on the oxidant electrode, a fuel electrode laminated on the electrolyte plate, and a liquid fuel laminated on the fuel electrode A fuel cell comprising a holding unit and a liquid fuel vaporizing unit provided in contact with the fuel electrode and the liquid fuel holding unit.

Further, an electrolyte plate, an oxidizer electrode and a fuel electrode provided on opposing surfaces of the electrolyte plate, a liquid fuel vaporizer provided on the fuel electrode, and a distance of 1 cm or less from the fuel electrode. And a liquid fuel holding unit connected to the liquid fuel vaporizing unit.

According to a second aspect of the present invention, there is provided an oxidant electrode, an electrolyte plate laminated on the oxidant electrode, a fuel electrode laminated on the electrolyte plate, a liquid fuel holding portion, and each of the fuel electrode and the liquid fuel holding portion. A fuel cell comprising: a plurality of cells having a liquid fuel vaporization section provided in contact with the fuel cell; and a liquid fuel source connected to the plurality of cells via respective liquid fuel holding sections. .

According to the present invention, in addition to the above-described effects of the first invention of the present application, since the fuel is vaporized in each of the individual cells, the gas distribution as in the conventional vaporized supply type fuel cell is not sufficient. Variations in battery performance in the stacking direction due to uniformity can be reduced.

Further, it is preferable that the liquid fuel holding section is formed of a permeating member exhibiting a capillary phenomenon, and the liquid fuel is supplied to the liquid fuel vaporizing section by the capillary force of the permeating member.

With such a configuration, since the liquid fuel is introduced into the cell by capillary force, it is possible to eliminate a driving unit such as a pump for supplying fuel. Further, since the gaseous fuel in the fuel vaporizing section is kept substantially saturated, the liquid fuel is vaporized from the fuel permeable member by the amount of the gaseous fuel consumed by the fuel vaporizing section due to the cell reaction, and the liquid fuel is further capillaryly moved by the vaporized amount. Is introduced into the cell. in this way,
Since the amount of fuel supply is linked to the amount of fuel consumed, there is almost no fuel unreacted and discharged outside the cell, and the processing system on the fuel outlet side can be simplified as in a conventional liquid fuel cell. It becomes possible.

[0020]

Embodiments of the present invention will be described below.

FIG. 1 is a cross-sectional view showing the structure of a main part of a fuel cell according to one embodiment.

In FIG. 1, an electrolyte plate 1 is sandwiched between a fuel electrode (anode) 2 and an oxidant electrode (cathode) 3 and is arranged to face each other. The electrolyte plate 1, the fuel electrode 2 and the oxidant electrode 3 constitute an electromotive section 4. Here, the fuel electrode 2 and the oxidant electrode 3 are formed of a conductive porous body so as to allow fuel and oxidant gas to flow and to pass electrons.

In the fuel cell according to the first aspect of the present invention, a fuel holding portion having a function of holding a liquid fuel, and a fuel for guiding a gaseous fuel obtained by evaporating the liquid fuel held by the fuel holding portion to the fuel electrode 2 are provided. A vaporizing section 7 is provided, and a liquid fuel holding section is arranged at a position where reaction heat generated by a cell reaction is transmitted. At this time, it is desirable to bring the fuel holding unit close to a position where it is heated to about 40 ° C. or more by the reaction heat.

In FIG. 1, a fuel permeable member 6 functioning as a fuel holding unit is laminated via a fuel vaporizing unit 7 provided in a layer on the electromotive unit 4 so that the fuel holding unit and the fuel electrode are Can be used as a unit cell in the vicinity. In addition, a plurality of such unit cells are stacked via a separator 5 to form a stack 9 serving as a battery body.
An oxidizing gas supply groove 8 for flowing an oxidizing gas is provided as a continuous groove on a surface of the separator 5 which is in contact with the oxidizing electrode 3.

As means for supplying fuel to the fuel permeable members 6 in a stacked state, a fuel introduction passage 10 connected to a liquid fuel tank is formed on at least one side of the stack 9. The fuel introduction path 10 is not always necessary, and may be any mechanism that can supply the fuel in the liquid fuel tank to a fuel infiltration section described later. The liquid fuel introduced into the liquid fuel introduction passage 10 is
Is supplied to the fuel infiltration member from the side surface, and is further vaporized in the fuel vaporizing section 7 and supplied to the fuel electrode 2. At this time, by configuring the fuel holding unit with a member exhibiting a capillary phenomenon, the liquid fuel can be permeated by capillary force and supplied to the fuel holding unit 6 without using an auxiliary device. To do so, the liquid fuel introduction channel 1
The structure is such that the liquid fuel introduced into the cylinder 0 directly contacts the end face of the fuel permeable member.

When the stack 9 is formed by stacking the unit cells as shown in FIG. 1, the generated electrons are used by using a conductive material for the separator 5, the fuel permeable member 6 or the fuel vaporizing section 7. It is also possible to function as a conducting current collecting plate.

Further, if necessary, a layered, island-shaped or granular catalyst layer may be formed between the fuel electrode 2 or the oxidizer electrode 3 and the electrolyte plate 1. The presence or absence of a suitable catalyst layer is not limited. Further, the fuel electrode 2 or the oxidant electrode 3 may be used as the catalyst electrode. The catalyst electrode may be a single catalyst layer, or may have a multilayer structure in which a catalyst layer is formed on a support such as conductive paper or cloth.

As described above, the separator 5 in this embodiment can also have a function as a channel for flowing an oxidizing gas. As described above, by using the component 5 having both functions of the separator and the channel (hereinafter, referred to as a channel / separator), the number of components can be further reduced, and the size can be further reduced. . Note that a normal channel can be used instead of the separator 5.

As a method of supplying the liquid fuel from the fuel storage tank to the liquid fuel introduction passage 10, there is a method of allowing the liquid fuel in the fuel storage tank to fall naturally and introducing it into the liquid fuel introduction passage 10. This method can reliably introduce the liquid fuel into the liquid fuel introduction passage 10 except for the structural restriction that the fuel storage tank must be provided at a position higher than the upper surface of the stack 9. As another method, there is a method of drawing liquid fuel from a fuel storage tank by the capillary force of the liquid fuel introduction passage 10. According to this method, the connection point between the fuel storage tank and the liquid fuel introduction passage 10, that is, the position of the fuel inlet provided in the liquid fuel introduction passage 10 does not need to be higher than the upper surface of the stack 9. When combined with the drop method, there is an advantage that the installation location of the fuel tank can be freely set.

However, in order to continuously supply the liquid fuel introduced into the liquid fuel introduction passage 10 by the capillary force to the fuel osmotic member 6 by the capillary force, the fuel osmosis member is formed by the capillary force of the liquid fuel introduction passage 10. It is important to set the capillary force to 6 to be greater. The number of the liquid fuel introduction passages 10 is not limited to one along the side surface of the stack 9, and the liquid fuel introduction passage 10 can be formed on the other stack side surface.

The fuel storage tank as described above is
It can be detachable from the battery body. Thus, by replacing the fuel storage tank, the operation of the battery can be continued for a long time. Further, the supply of the liquid fuel from the fuel storage tank to the liquid fuel introduction path 10 may be configured such that the liquid fuel is pushed out by the above-described natural fall, the internal pressure in the tank, or the like. It is also possible to adopt a configuration in which fuel is drawn out with a capillary force of 10.

The liquid fuel introduced into the liquid fuel introduction passage 10 is supplied to the fuel permeable member 6 by the above-described method. However, the form of the fuel holding portion is not limited to the liquid fuel permeable member, but may be a liquid fuel permeable member. The fuel is not particularly limited as long as it has a function of holding the fuel therein and supplying only the vaporized fuel to the fuel electrode 2 through the fuel vaporizing section 7.
For example, it may have a passage for a liquid fuel and include a gas-liquid separation membrane at the interface with the fuel vaporization section 7.

Further, when the liquid fuel is supplied to the fuel permeable member 6 by capillary force, the form of the fuel permeable member 6 is not particularly limited as long as the liquid fuel can be permeable by capillary force. In addition to a porous body made of glass or a filler, a nonwoven fabric manufactured by a papermaking method, a woven fabric woven with fibers, and the like, it is also possible to use a narrow gap formed between the plates such as glass or plastic. it can.

The case where a porous body is used as the fuel permeable member 6 will be described below. As the capillary force for drawing the liquid fuel into the fuel permeable member 6 side, first, the capillary force of the porous body itself that becomes the fuel permeable member 6 can be mentioned. When such a capillary force is used, a so-called continuous hole is formed by connecting the holes of the fuel permeable member 6 which is a porous body, the diameter of the hole is controlled, and the side surface of the fuel permeable member 6 on the side of the liquid fuel introduction passage 10 is controlled. To at least one other surface, the liquid fuel can be smoothly supplied by the capillary force even in the lateral direction.

The pore diameter and the like of the porous body serving as the fuel permeable member 6 may be any as long as the liquid fuel in the liquid fuel introduction passage 10 can be drawn in, and is not particularly limited. 0.01-1 in consideration of capillary force
Preferably, the thickness is about 50 μm. Further, the volume of pores, which is an index of continuity of pores in the porous body, is 20 to 90.
% Is preferable. If the hole diameter is smaller than 0.01 μm, the permeation speed of the liquid fuel inside the fuel permeation member 6 becomes slow, so that a smooth fuel supply cannot be performed.
If it exceeds 150 μm, the capillary force will be reduced. When the volume of the holes is less than 20%, the amount of continuous holes decreases,
Since the number of closed holes increases, sufficient capillary force cannot be obtained. Conversely, if the volume of the pores exceeds 90%, the amount of continuous pores increases, but the strength becomes weak and the production becomes difficult. Practically, the pore size is 0.5-100μ
m, and the volume of the pores is preferably in the range of 30 to 75%.

The capillary force for drawing the liquid fuel into the fuel permeable member 6 is not limited to the above-described capillary force of the porous body itself serving as the fuel permeable member 6. FIG. 2 shows a modified example of the fuel cell according to the present invention. As shown in FIG. 2, for example, as shown in FIG.
It is also possible to provide a liquid fuel supply groove 11 on the surface in contact with the liquid fuel supply groove 11 and draw the liquid fuel toward the fuel permeable member 6 by utilizing the capillary force of the liquid fuel supply groove 11. In this case, the liquid fuel introduction passage 10 is provided so that at least the open end of the liquid fuel supply groove 11 is in direct contact with the liquid fuel. It is also possible to use both the capillary force of the liquid fuel supply groove 11 and the capillary force of the porous body itself that becomes the fuel permeable member 6.

The shape of the liquid fuel supply groove 11 is not particularly limited as long as it can exert a capillary force, but it is necessary that at least the capillary force of the groove 11 be smaller than the capillary force of the fuel permeable member 6. If the capillary force of the groove 11 is larger than that of the fuel permeable member 6, the liquid fuel in the liquid fuel introduction passage 10 is supplied to the liquid fuel supply groove 11 but is supplied to the fuel permeable member 6. Can not be done.

Further, since the liquid fuel supply groove 11 draws the liquid fuel from the liquid fuel introduction passage 10 by its capillary force, the capillary force is transferred from the fuel storage tank to the liquid fuel introduction passage 10 as described above. In the case where the liquid fuel is introduced in the step (1), the capillary force of the liquid fuel supply groove 11 is set to be larger than the capillary force of the liquid fuel introduction passage 10. Thus, the shape of the liquid fuel supply groove 11 is
It is set in consideration of the shape of the porous body and the liquid fuel introduction passage 10 to be formed.

As described above, the channel / separator 5
For example, by providing a liquid fuel supply groove 11 extending in the horizontal direction, the liquid fuel is supplied to the fuel permeable member 6 from the entire end portion of the fuel electrode 2, and the liquid fuel is simultaneously supplied to the fuel permeable member 6 in the lateral direction through the groove 11. Since the fuel can be supplied, the liquid fuel in the liquid fuel introduction passage 10 can be more smoothly supplied to the fuel permeable member 6.

In the above-described embodiment, the case where both the oxidizing gas supply groove 8 and the liquid fuel supply groove 11 are formed in the channel / separator 5 has been described. Channels may be set individually. In such a case, the liquid fuel and the oxidizing gas are separated from each other by installing a conductive plate that does not allow gas to pass between the two channels, or by closing a hole in the surface of at least one of the channels. . However, in order to reduce the number of parts and further reduce the size, it is preferable to use the channel also.

In each of the above-described embodiments, the electromotive unit 4, the fuel permeable member 6,
Although the description has been given of the fuel cell having the stack 9 in which the fuel vaporization sections 7 are stacked, the separator and the channel are not always necessary in the fuel cell of the present invention. FIG.
Is a schematic cross-sectional view showing a modification of the fuel cell according to the present invention. For example, as shown in FIG. 3, a plurality of electromotive units 4, fuel permeable members 6, and fuel vaporization units 7 are directly stacked. It is also possible to configure the stack 12. At this time, the oxidizing gas supply groove 8 is formed as a continuous groove on the surface of the oxidizing electrode 3 which is in contact with the fuel permeable member 6, as shown in FIG. 3, for example.

When the fuel electrode 2 is in direct contact with the oxidant electrode 3 as described above, it is necessary to prevent the liquid fuel from being drawn into the oxidant electrode 3 from the fuel permeable member 6. Is desired. This is because, when the liquid fuel is drawn into the oxidant electrode 3, the oxidant gas becomes difficult to flow, thereby inhibiting the cell reaction. As a method for preventing the infiltration of the liquid fuel into the oxidant electrode 3 described above, basically, the pore diameter of the porous body serving as the oxidant electrode 3 is controlled to a size such that the liquid fuel is not drawn in by capillary action. do it. However, depending on the equipment to be applied, the hole diameter may need to be large enough to draw the liquid fuel by capillary action. In such a case, the pores on the surface of the porous body serving as the fuel permeable member 6 on the oxidant electrode 3 side may be closed.

However, the oxidant gas supply groove 8 is
Is provided, the fuel permeable member 6 excluding the groove 8 of the oxidizer electrode 3
May be closed, but there is a risk that liquid fuel may enter the oxidant electrode 3 through the side surface of the oxidant gas supply groove 8, and in this case, the contact surface of the oxidant electrode 3 with the fuel permeable member 6. It is preferable to close the hole on the side surface of the oxidant gas supply groove 8.

The liquid fuel thus introduced into the cell is vaporized by the fuel vaporizing section 7 and reaches the fuel electrode 2.
For this purpose, it is important to set the capillary force of the fuel vaporizing section 7 to be smaller than the capillary force of the fuel permeating member 6. If the capillary force of the fuel vaporizing part 7 is larger than that of the fuel permeable member 6, the liquid fuel in the fuel permeable member 6 does not vaporize but permeates into the fuel vaporizing part 7 in a liquid state, and the liquid fuel is 2 will be supplied.

The condition required for the fuel vaporizing section 7 is that the liquid fuel in the fuel holding section 6 has a space in which the vaporized gas is diffused, and the reaction heat by the fuel cell is transmitted to the liquid fuel in the fuel holding section 6. In the case where a stack is formed by stacking unit cells, electronic conductivity is further required. The form is not particularly limited as long as the above conditions are satisfied. For example, if conductivity is not required, a space may be simply provided between the fuel holding portion and the fuel electrode, and a conductive porous body or a conductive mesh may be provided between the fuel electrode 2 and the fuel permeable member 6. It is also possible to form a minute space by laminating or by sandwiching a conductive wire, fiber, particle or the like as a pillar between the fuel electrode 2 and the fuel holding portion.

Further, by setting the fuel vaporizing section to a shape such that the interface between the fuel holding section and the fuel vaporizing section where the liquid fuel vaporizes is within 1 cm, preferably within 5 mm from the electromotive section, The reaction heat of the battery can be effectively used for vaporizing the liquid fuel. Further, as described above, the fuel electrode 2
It is possible to effectively transfer the reaction heat to the liquid fuel by holding an appropriate material between the fuel and the fuel holding portion.

When the fuel vaporizing section 7 is formed of a porous body,
As described above, the pore diameter and the like are not particularly limited as long as the vaporized fuel can diffuse without drawing the liquid fuel in the fuel permeable member 6. In consideration of the capillary force of No. 6, the thickness is preferably 5 μm or more. The volume of the pores of the porous body is 20 to 90.
% Is preferable.

In the example of FIG. 1, the fuel permeating member 6 and the fuel vaporizing section 7 are constituted by independent members. However, the liquid fuel is held inside each unit cell and vaporized inside the cell. If there is, it is not limited to this configuration. For example,
There is also a method using a porous gradient material in which the average pore diameter is changed along the thickness direction. In this case, it is arranged such that the surface having the larger average pore diameter is in contact with the fuel electrode 2. That is, the side with a smaller hole diameter functions as a fuel permeable member, and the side with a larger hole diameter functions as a fuel vaporization unit. In this case, the surface of the vaporizing section in contact with the liquid fuel holding section can be adjusted according to the type of fuel, the distribution of the pore diameter of the porous body, or the degree of pressure of the liquid fuel.

In addition, one side of the porous plate in the thickness direction is formed of a material having good wettability with liquid fuel, and the other side is formed of a material having poor wettability. There is also a method in which the fuel infiltration member or the one with poor wettability functions as a fuel vaporizing section. In this case, the fuel electrode 2 is arranged such that the surface having poor wettability with the liquid fuel is in contact with the fuel electrode 2.

FIG. 1 shows an example in which the fuel vaporizing section 7 is provided between the fuel permeable member 6 and the fuel electrode 2, but the fuel vaporizing section may be formed as a part of the fuel permeable member. An example is shown below with reference to the drawings.

FIG. 4A is a sectional view showing an example of the present invention.
FIG. 4B is a plan view of the flat plate used in FIG.

A thin gap 17 is formed between the two opposed flat plates 15 and 16 so that a capillary phenomenon occurs, and the liquid fuel is held in the gap 17. That is, 2
The flat plates 15 and 16 form a liquid permeable member.

Here, an opening is provided in the flat plate 16 which is in contact with the fuel electrode 2 among the two flat plates. This allows
The liquid fuel is held in the portion sandwiched between the smooth plates 15 and 16, but in the opening, the gap 17 sandwiched between the fuel electrode and the flat plate 15 is widened so that the liquid fuel is not held and the space is reduced. It is formed. The liquid fuel held in the gap 17 is vaporized by the reaction heat of the cell at the interface with the space, and is supplied to the fuel electrode 2 through the hole of the perforated plate 16.
That is, the portion where the flat plates 15 and 16 are opposed to each other (the portion of the perforated plate 16 having no hole) functions as the fuel permeable member 6,
The gap formed between the fuel electrode 2 and the flat plate 15 (perforated plate 1
6) functions as the fuel vaporizing section 7. Thus, by arranging the fuel permeation section 6 and the fuel vaporization section 7 in parallel, the thickness of the battery can be reduced.

This structure is suitable for a flat fuel cell in which each unit cell is arranged on a plane and electrically connected in series.

FIG. 5 shows an embodiment of a flat type fuel cell using the fuel cell of FIG.

When the cells are connected in series, the oxidizer electrode of the first cell and the fuel electrode of the second cell are connected by the connecting conductor 18. Further, since the fuel infiltration members share the flat plates 15 and 16, the fuel introduction path 10 can be shared.

In this case, since the cells are connected in series using the connecting conductor 18, the flat plates 15, 16 forming the fuel permeable member 6 and the fuel vaporizing section 7 do not need to have electric conductivity. Normal glass or plastic can be used.

The method for forming the fuel vaporizing portion in a part of the fuel permeable member is not limited to the above-described method. For example, as shown in FIG. A method for forming a space as a fuel vaporizing part 7 in a part in contact with the
There is also a method of embedding a porous plate having a larger pore diameter than the porous body constituting the above. At this time, it is necessary to take measures to prevent the liquid fuel from directly penetrating from the fuel permeable member 6 to the fuel electrode 2 at the interface between the porous body constituting the fuel permeable member 6 and the fuel electrode 2.
Examples of the method include a method of closing pores at the interface of the fuel permeable member 6 with the fuel electrode 2 and a method of providing a liquid fuel impermeable membrane at the interface.

[0059]

Next, specific examples of the fuel cell of the present invention and evaluation results thereof will be described. Since the object of the present invention is a simplified and miniaturized fuel cell, as described above, the conventional fuel vaporization supply type fuel cell whose system is extremely complicated and difficult to miniaturize is excluded from comparison. A comparison is made with a liquid supply type liquid fuel cell that may be downsized.

Embodiment 1 FIG. 7 is a sectional view of a fuel cell used in this embodiment.

It was manufactured in the following manner. First, a Pt-Ru-based catalyst layer was applied on a carbon cloth and was 32 mm x 32 mm.
A fuel electrode 2 having a thickness of 0.5 mm and a thickness of 0.5 mm, and an oxidizer electrode 3 having a size of 32 mm × 32 mm and a thickness of 0.5 mm formed by coating a Pt black catalyst layer on carbon cloth so that the catalyst layer is in contact with the electrolyte membrane. Composed of a perfluorosulfonic acid membrane
An electrolyte membrane 1 of mm × 40 mm and thickness of 0.2 mm was sandwiched. 100 kg / cm ² at 120 ° C. for 5 minutes.
Then, they were joined by hot pressing at a pressure of 5 ° C. to produce an electromotive section 4.

On the fuel electrode 2 of the electromotive section 4, a porous plate serving as the fuel vaporizing layer 7 and the fuel permeable layer 6 was sequentially arranged. This is combined with an oxidant electrode side holder 13 having an oxidant supply groove and a fuel electrode side holder 14 which are arranged on the oxidant electrode side of the electromotive section 4.
And a reaction area of 10cm
^{Two unit} cells were produced.

The porous plate used for the fuel vaporization layer 7 has an average pore diameter of 100 μm, 32 mm × 40 mm, and a thickness of 5 mm.
By exposing a part of the carbon porous plate to the outside of the holder, CO ₂ generated by the battery reaction can be released to the outside of the unit cell.

The porous plate used for the fuel permeable layer 6 was a carbon porous plate having an average pore diameter of 20 μm, 32 mm × 40 mm, and a thickness of 5 mm. It was immersed in the tank.

The oxidizing agent supply groove formed in the oxidizing agent side holder 13 is formed with a plurality of grooves having a depth of 1 mm and a width of 1 mm at equal intervals, and air is introduced from one end of the oxidizing agent supply groove. Water, which is a reaction product, is discharged from the other end.

A 1: 1 (molar ratio) mixture of methanol and water as a liquid fuel is introduced into the thus obtained liquid fuel cell from the side surface of the fuel permeable layer 6 by capillary force, and 1 atm of oxidant gas is supplied. Air was generated at 80 ° C. by flowing air through the gas channel 8 at 100 ml / min. FIG. 8 shows the current-voltage characteristics of this battery.

Comparative Example 1 A conventional liquid supply type fuel cell (cell) was manufactured in the following manner. First, a joined body of the electromotive section was manufactured in the same manner as in Example 1. A unit cell having a reaction area of 10 cm ² was produced by sandwiching the electromotive section on the fuel electrode side with the liquid fuel flow channel plate and the oxidant electrode side with the same gas channel as in Example 1.

A 1: 1 (molar ratio) mixture of methanol and water as a liquid fuel is circulated through the thus obtained liquid fuel cell at a rate of 1 atm and 3 ml / min by a pump. Was passed through a gas channel at 100 ml / min to generate power at 80 ° C. FIG. 8 shows the current-voltage characteristics of this battery.

As is clear from FIG. 8, in the liquid fuel cell of the first embodiment, the output can be taken out stably up to about 5 A, but in the liquid fuel cell of the first comparative example, the output is rapidly increased as the current increases. And the current cannot be taken for 2A.
The low performance of the liquid supply type fuel cell of Comparative Example 1 is due to the low electrode reaction activity between the liquid fuel and the fuel electrode, and the fact that the liquid methanol permeates the electrolyte membrane toward the oxidant electrode side. Due to crossover. On the other hand, in the fuel cell of Example 1, since the fuel electrode is supplied with vaporized fuel, the electrode reaction activity is high and methanol crossover is unlikely to occur. Therefore, high performance can be stably obtained even under a high load.

Example 2 Five unit cells produced in the same manner as in Example 1 were stacked, and the protruding portions of each fuel permeable member were mixed with a mixed solution of methanol and water formed at a mixing ratio of 1: 1. The connection was made via a filled fuel introduction channel.

1 atm of air as oxidant gas is 500 m
The gas was passed through the gas channel 8 at 1 / min to generate power at 80 ° C. with a load of 2 A.

FIG. 9 shows the output value of each cell.

COMPARATIVE EXAMPLE 2 The fuel infiltration member was removed, and the position corresponding to the fuel infiltration member was used as a space.
The same experiment as in Example 1 was performed, except that the gas was flowed for min.

FIG. 9 also shows the output value of each unit cell of the fuel cell used in this comparative example.

As is apparent from FIG. 9, in the example 2, substantially uniform output was obtained in each cell, whereas in the comparative example 2, the output of each cell varied, and the output was sufficient. It can be seen that there is a single cell for which no is obtained.

In the examples, the mixed liquid consisting of methanol and water was used as the liquid fuel. However, the liquid fuel in the present invention is not limited to this. Any fuel that can supply ions can be used. For example, a liquid fuel containing alcohols such as ethanol, ethers such as dimethyl ether, hydrazine, and the like can be used.

[0077]

As described above, according to the fuel cell of the present invention, it is possible to smoothly vaporize and supply liquid fuel with a simple structure without using a pump, a blower or the like. This makes it possible to provide a small fuel cell that has been difficult in the past.

Further, it is possible to suppress a variation in the concentration of the fuel supplied to the plurality of unit cells, thereby enabling stable power generation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a main part of a fuel cell according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a main part of another embodiment of the fuel cell of the present invention.

FIG. 3 is a cross-sectional view showing a main configuration of a fuel cell without a separator according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing another essential configuration of the fuel cell according to the embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration example of a flat panel fuel cell using the fuel cell shown in FIG. 4;

FIG. 6 is a cross-sectional view showing still another essential configuration of the fuel cell according to one embodiment of the present invention.

FIG. 7 is a sectional view of the fuel cell according to the first embodiment.

FIG. 8 is a current-voltage characteristic diagram of the fuel cell according to Example 1 and Comparative Example 1 of the present invention.

FIG. 9 is a diagram showing battery outputs according to an example of the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrolyte plate 2 ... Fuel electrode 3 ... Oxidizer electrode 4 ... Electromotive part 5 ... Separator 6 ... Fuel penetration member 7 ... Fuel vaporization part 8 ... Oxidation Agent gas supply groove 9 ... Stack 10 ... Liquid fuel introduction path 11 ... Liquid fuel supply groove 12 ... Stack without using separator 13 ... Oxidant electrode side holder 14 ... Fuel electrode side Holder 15: Flat plate 16: Flat plate with opening 17 ... Gap 18: Conductor for connection

Continuing from the front page (72) Inventor Yoshihiro Akasaka 1 Tokoba, Komukai Toshiba-cho, Saisaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Research and Development Center Co., Ltd. Inside the Toshiba R & D Center (72) Inventor Masahiro Takashita 1 in Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center 5H026 AA06 CC03 HH03

Claims (6)

[Claims] 1. An oxidant electrode, an electrolyte plate laminated on the oxidant electrode, a fuel electrode laminated on the electrolyte plate, a liquid fuel holding part laminated on the fuel electrode, and the fuel electrode And a liquid fuel vaporization unit provided in contact with each of the liquid fuel holding units. 2. An oxidant electrode, an electrolyte plate laminated on the oxidant electrode, a fuel electrode laminated on the electrolyte plate, a liquid fuel holding part, and a liquid fuel holding part provided in contact with each of the fuel electrode and the liquid fuel holding part. A fuel cell, comprising: a plurality of unit cells having a liquid fuel vaporization unit provided; and a liquid fuel source connected to the plurality of unit cells via respective liquid fuel holding units. 3. An electrolyte plate, an oxidizer electrode and a fuel electrode provided on opposing surfaces of the electrolyte plate, a liquid fuel vaporizer provided on the fuel electrode, and a distance of 1 cm or less from the fuel electrode. A fuel cell, comprising: a liquid fuel holding unit connected to the liquid fuel vaporizing unit. 4. The liquid fuel holding section according to claim 1, wherein the liquid fuel holding section is formed of a permeating member exhibiting a capillary phenomenon, and the liquid fuel is supplied to the liquid fuel vaporizing section by a capillary force of the permeating member. Fuel cell. 5. The liquid fuel holding section is a liquid fuel holding layer including a first flat plate having an opening provided on a fuel electrode, and a second flat plate opposed to the first flat plate. The fuel cell according to claim 4, wherein: 6. A fuel cell comprising: an electrolyte plate; an oxidizer electrode and a fuel electrode provided on opposing surfaces of the electrolyte plate; and a liquid fuel holding portion for holding fuel supplied to the fuel electrode. A fuel cell characterized in that fuel held in a fuel holding unit is vaporized by reaction heat of a cell reaction.