JP2001093541A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell that makes a liquid fuel supply system simple, with smooth vaporization and shortened start time, and also can promote miniaturization. SOLUTION: The fuel cell includes unit batteries 10 each including a fuel electrode, an oxidizer electrode opposite to the fuel electrode, and an electrolyte layer interposed in between. A plurality of the unit batteries are stacked one on another, while intervening a fuel penetration/vaporization plate (11) into which a liquid fuel is introduced. Moreover, the fuel introduction side of the fuel battery is provided with heating means 8 for heating the fuel penetration/ vaporization plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly, to a fuel cell suitable for miniaturization capable of smoothly vaporizing fuel.

[0002]

2. Description of the Related Art A fuel cell is a power source that has recently attracted attention because of its high efficiency as a single power generator. Such fuel cells include a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid electrolyte fuel cell, and an alkaline electrolyte fuel cell using gas as fuel, and a methanol fuel cell and hydrazine using liquid as fuel. They are roughly divided into fuel cells and the like.

[0003] 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 to satisfy such demands,
Easy primary batteries and secondary batteries are used.

However, the primary battery and the secondary battery have a limited use time in terms of function, so that the use time of an OA device or the like using such a battery is naturally limited.
When these batteries are used, after the batteries have been discharged, the batteries can be replaced and the OA equipment can be moved, but the primary battery has a short usage time with respect to its weight, so it is not suitable for portable equipment. Not suitable. On the other hand, a secondary battery can be charged when discharge ends,
A power source is required for charging, and the place of use is limited. In addition, there is a disadvantage that 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 or secondary battery, and there is a demand for a battery suitably used for a longer operation.

[0006] One solution to meet such demands is a fuel cell. The fuel cell has an advantage that power can be generated only by supplying the fuel and the oxidant, and it is possible to continuously generate power by replacing the fuel. For this reason, if the size can be reduced, the fuel cell can be said to be a very advantageous system for the operation of small devices such as OA devices with low power consumption.

[0007] Since the fuel cell can use air as an oxidizing agent, there is no restriction on the place of use, the use time, and the like from the viewpoint of the oxidizing agent. However, when gas is used as a fuel, although the power consumption of OA equipment and the like is small, the gas amount required for power generation is large considering the density of the gas, 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 a fuel cell using a high-concentration liquid fuel can be miniaturized, a power source for a small device that can operate for a long time, which has not been available in the past, can be realized.

[0008] For example, a methanol fuel cell using methanol as a liquid fuel is a liquid supply type in which liquid fuel is supplied to the cell body as it is, or a liquid supply type in which liquid fuel is vaporized and then supplied to the cell body. It is roughly divided into a vaporization supply type that supplies.

In the liquid supply type system, since the electrode reaction is carried out with the liquid fuel, there is a problem that the activity is lower and the performance is lower than in the case where the electrode reaction is carried out by gasifying methanol. Furthermore, when a proton-conductive solid polymer membrane such as perfluorosulfonic acid (trade name: manufactured by Nafion DuPont) is used as an electrolyte, a cloth that permeates a liquid organic fuel such as methanol to the oxidant electrode side. There is also the problem of over.

On the other hand, in the vaporization supply type, a method is used in which a liquid fuel such as methanol pumped from a liquid fuel tank is vaporized by an auxiliary device such as a vaporizer and the vaporized fuel is supplied to a battery or the like by a blower. Is also known. Also in this method, there is a problem that an auxiliary device for vaporizing is required, which results in an increase in the size of the device.

A fuel cell is generally used in the form of a stack in which a plurality of unit cells are stacked. When the fuel vaporized in advance is pumped by a pump or a blower, the vaporized fuel may condense during the supply to each unit cell, or the temperature of the fuel in the stacking direction of the stack may be different. In such a case, the performance of the cells constituting the stack may vary.

Further, when the temperature is low in winter, liquid fuel such as methanol becomes difficult to vaporize.
There has been a problem that the rising speed of the battery is extremely delayed.

[0013]

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 another object of the present invention to provide a fuel cell which simplifies a liquid fuel supply system, smoothly evaporates the fuel, shortens the battery start-up time, and achieves downsizing.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a fuel electrode, an oxidizer electrode disposed opposite to the fuel electrode, and sandwiched between the fuel electrode and the oxidizer electrode. Heating unit for heating the fuel permeation vaporizing plate in a fuel cell in which a plurality of unit cells each having a separated electrolyte layer are stacked via a fuel permeation vaporizing plate and a liquid fuel is introduced into the fuel permeation vaporizing plate. Is provided on the fuel introduction side.

According to the present invention, there is provided a fuel cell having a fuel electrode, an oxidant electrode disposed opposite to the fuel electrode, and an electrolyte layer sandwiched between the fuel electrode and the oxidant electrode. A fuel cell in which liquid fuel is introduced into the fuel pervaporation plate by means of a fuel cell, wherein the fuel cell comprises means for directly energizing and heating the fuel pervaporation plate. I will provide a.

Hereinafter, the present invention will be described in detail.

FIG. 1 is a schematic diagram showing a configuration of an example of the fuel cell of the present invention.

As shown, the fuel cell of the present invention basically comprises a fuel tank 1, a fuel cell main body 2, and an introduction pipe 3 for introducing fuel into the main body.

Liquid fuel is stored in a liquid storage section 5 in the liquid fuel tank 1, and a core 6 is provided inside the liquid fuel. Further, the fuel tank 1 is provided with a permeable membrane 4 on the upper side surface, and is connected to the introduction pipe 3 by a junction 7 on the bottom.

The fuel cell body 2 has a plurality of layers of MEAs (Me
mbrane ElectrodeAssembly)
Numerals 10 are stacked via a fuel permeable vaporizing plate 11, and the liquid fuel introduced by the introduction pipe 3 is supplied to each fuel permeable vaporizing plate 11 via a receiver 13.

Although not shown in FIG. 1, the MEA 10 has a configuration in which a fuel electrode (anode) and an oxidant electrode (cathode) are arranged to face each other, and an electrolyte plate is sandwiched between them. Is adjacent to the fuel pervaporation plate 11. Similarly, although not shown, an oxidant introduction groove is formed on the oxidant electrode side of the separator that functions to separate the batteries. An oxidant such as air is introduced from one end of the oxidant introduction groove and discharged from the other end, whereby the oxidant is supplied to the oxidant electrode.

The fuel electrode and the oxidant electrode in the MEA 10 are formed of a conductive porous material so that the vaporized fuel and the oxidant gas can flow and pass electrons.

Further, as shown in the drawing, in the fuel cell of the present invention, between the receiver 13 and each fuel permeable vaporizing plate 11, it is possible to conduct and generate heat for heating the fuel permeable vaporizing plate 11 collectively. A heating means (heater unit) 8 is provided.

A gas permeable membrane 12 is provided on the side of the fuel cell main body 2 on the gas discharge side, and a tank connecting portion 14, a preheating power supply and circuit 15, a connector 1
6 are provided.

Here, the heater unit 8 in the fuel cell of the present invention will be described in detail with reference to the drawings. The heater unit 8 can be configured, for example, as shown in FIG. FIG. 2A is a front view of the heater unit 8, and FIG. 2B is a cross-sectional view of the heater unit 8.

As shown in FIG. 2B, the heater unit 8 includes an outer shell 21 and a heating element 22 disposed inside the outer shell 21.
It is composed of

The outer shell of the heater unit 8 is made of an electrically insulating fluorine resin or silicon resin, and a carbide ceramic, an oxide ceramic or a boride ceramic having excellent electric insulation and heat conductivity. Is preferred. In the present invention, a nitride ceramic is not used as the outer shell of the heater unit. Although nitride-based ceramics have good thermal conductivity,
This is because the moisture contained in the fuel may react with the nitride ceramics to generate ammonia gas. The outer shell of the heater unit may be made of Teflon, silicon rubber, or polyethylene having excellent electrical insulation.

Specifically, the material constituting the outer shell of the heater unit is Si, which has good electrical insulation and heat conductivity.
C, TiC, WC, W ₂ C, ZrC, VC, NbC, H
fC, BeO, MgO, CaO, Al ₂ O ₃ , ThO ₂ ,
ZrO ₂ , UO ₂ , CeO ₂ , ZrB ₂ , TiB ₂ , Hf
B, TaB _{2 and the} like.

It is preferable that the heater 22 in the heater unit provided inside the outer shell of the heater unit is a sintered body, a metal body, or a composite body having a heating resistance characteristic.

Specifically, as the heating element 22, Au,
Pt, Ni, Cr, W, Ta, Mo, Nb, Ti, Z
Metal heating elements and non-metal heating elements selected from the group consisting of r, Si, C, La, V, Fe, O, and Co can be used.

As shown in the figure, the heat insulation / heat storage unit 9 can be provided at the gas discharge portion opposite to the heater unit 8, but it is not always necessary. Although the heat insulation / heat storage unit 9 does not have the heat generation resistance characteristic, it can store the heat insulation and the heat generated by the battery reaction, and can have a shape as shown in FIG.

The heat insulation / heat storage unit 9 includes, for example, urethane foam, polystyrene foam, rubber foam,
Isocyanurate foam, styrene foam, phenol foam, urea foam, carbonized cork, calcium silicate plate, foam glass, rock wool, glass fiber, glass foam, silica foam, cork, magnesia, vermiculite, iron oxide brick and composites thereof It can be constituted by a product.

FIG. 4 is a schematic diagram showing the configuration of another example of the fuel cell of the present invention.

The fuel cell shown in the drawing is further provided with a means 18 for directly energizing the fuel pervaporation plate 11 and heating it. Otherwise, the configuration is the same as that of the fuel cell shown in FIG. When the means 18 for directly energizing and heating the fuel pervaporation plates is provided as shown in FIG. 4, the heater unit 8 for heating the fuel pervaporation plates 11 collectively can be omitted. .

As described above, since the heater unit 8 for heating the fuel vaporized perforated plate at a time or the means 18 for directly energizing and heating the fuel vaporized perforated plate is provided, the fuel cell of the present invention is It is possible to quickly vaporize the fuel required at startup. Moreover, in the fuel cell of the present invention, the liquid fuel can be vaporized without using a large auxiliary device or the like, so that the size of the device can be reduced.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to specific examples.

(Embodiment 1) In this embodiment, heat insulation and
A fuel cell similar to that shown in FIG. 1 was configured except that the heat storage unit 9 was not provided.

As the heater unit 8, Teflon having excellent insulating properties was used as the outer shell 21, and a sheath-type nichrome heating element was used as the heating element 22 and wired inside as shown in FIG. 2B.

The MEA 10 is 50 mm × 50 m
m, Nafion 117 (manufactured by DuPont), which is a polymer electrolyte membrane having a thickness of 0.18 mm, was used. The fuel electrode was a 50 μm-thick catalyst layer (Pt / Ru = 1/1, 4.0 mg / m) on the surface of the carbon cloth coated with the water-repellent carbon layer.
cm ² ). The oxidizer electrode is formed by coating a 50 μm-thick catalyst layer (Pt Black,
4.0 mg / cm ² ). The size of both the fuel electrode and the oxidizer electrode is 33 m
mx 33 mm, thickness 0.4 mm.

The carbon separators (33 mm × 33 mm, thickness 4 mm) were pressed against the MEA to make them airtight. Each separator has a depth of 1mm
Were formed by cutting. Air as an oxidant gas is introduced into a groove formed in the separator arranged on the oxidant electrode side. Methanol and water as fuel are supplied from a tank provided outside the cell to a groove formed in the separator provided on the fuel electrode side.

The fuel cell thus obtained was pressed and fixed at a pressure of ² kgf / cm ² in the stacking direction.

The fuel cell having the above-described configuration was started in the following procedure.

First, while applying a voltage of 3.5 V to the heater unit 8 from the preheating power supply 16 built in the stack body, a mixed solution of methanol and water was supplied to the separator provided on the fuel electrode side. Supplied so that the utilization rate might be 60%. On the other hand, air as an oxidant gas was supplied to the groove of the separator provided on the oxidant electrode side so that the utilization rate became 20%.

The change over time of the cell voltage when the battery of this embodiment was started from 0 ° C. is shown as a curve a in the graph of FIG.

As shown in the graph of FIG. 5, in the fuel cell of this embodiment, the voltage is stabilized at 1 V in a very short time of 40 seconds.

Example 2 A fuel cell having the structure shown in FIG. 1 was used. That is, a fuel cell was constructed under the same conditions as in Example 1 except that the heat insulation / heat storage unit 9 was provided. The battery was operated under the same conditions as described above, the power generation of the battery was terminated, and the battery was restarted after 5 minutes. The change over time of the cell voltage of the fuel cell at this time is shown as a curve b in the graph of FIG.

As shown in the graph of FIG. 5, in the fuel cell of this embodiment, the voltage is stabilized at 1 V in a very short time of 40 seconds.

Example 3 A fuel cell having the structure shown in FIG. 1 was used. That is, a fuel cell was constructed under the same conditions as in Example 1 except that the heat insulation / heat storage unit 9 was provided. This fuel cell was operated in the following procedure.

First, a voltage of 3.5 V was applied to the heater unit 8 from the preheating power supply 16 built in the stack body. After confirming that the temperature of the heater unit 8 was raised to 60 ° C., a mixed solution of methanol and water was supplied to a separator provided on the fuel electrode side so that the utilization rate became 60%. On the other hand, air as an oxidant gas was supplied to the groove of the separator provided on the oxidant electrode side so that the utilization rate became 20%.

The change over time of the cell voltage when the battery of this example was started from 0 ° C. is shown as a curve c in the graph of FIG.

As shown in the graph of FIG. 5, in the fuel cell of this embodiment, the voltage rises quickly, and the voltage is stabilized at 1 V in a very short time of 20 seconds after the fuel cell rises.

Comparative Example A fuel cell similar to that shown in FIG. 1 was constructed except that the heater unit 8 was not provided.
The operation was performed under the same conditions as described above. The change over time of the cell voltage of this battery is shown as a curve d in the graph of FIG.

As shown in the graph of FIG. 5, in the battery of the comparative example, it takes much time for the voltage to rise immediately after the start of operation. Specifically, it takes 180 seconds to obtain a cell voltage of 1 V, which indicates that this battery cannot be driven in a short time.

[0054]

As described in detail above, according to the present invention,
A fuel cell is provided, which simplifies a liquid fuel supply system, smoothly evaporates fuel, shortens the battery start-up time, and enables downsizing.
INDUSTRIAL APPLICABILITY The fuel cell of the present invention can be started well in a short time even in winter or in a low temperature state, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an example of a fuel cell according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of a heater unit used in the fuel cell of the present invention.

FIG. 3 is a schematic diagram showing an example of a heat insulation / heat storage unit that can be used in the fuel cell of the present invention.

FIG. 4 is a schematic diagram illustrating a configuration of another example of the fuel cell of the present invention.

FIG. 5 is a graph showing a relationship between a start-up time and a cell voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2 ... Fuel cell main body 3 ... Introductory pipe 4 ... Permeation membrane 5 ... Liquid storage part 6 ... Core 7 ... Junction 8 ... Heater unit 9 ... Heat insulation / heat storage unit 10 ... MEA 11 ... Fuel permeation vaporization plate 12 ... Gas permeable membrane 13 ... Receiver 14 ... Tank connection 15 ... Preheating power supply and circuit 16 ... Connector 18 ... Direct current heating means 21 ... Heater unit outer shell 22 ... Heater inside heating unit

Claims (3)

[Claims] 1. A unit cell comprising a fuel electrode, an oxidant electrode disposed opposite to the fuel electrode, and an electrolyte layer sandwiched between the fuel electrode and the oxidant electrode, via a fuel permeable vaporizing plate. A fuel cell in which a plurality of layers are stacked and liquid fuel is introduced into the fuel osmotic vaporizing plate, wherein a heating means for heating the fuel osmotic vaporizing plate is provided on the fuel introduction side. 2. A gas discharge unit, which is on the opposite side of said heating means, is provided with a heat insulation / heat storage unit capable of storing heat generated by a battery reaction and storing heat and having no heat generation resistance characteristic. The fuel cell according to claim 1, wherein 3. A unit cell comprising a fuel electrode, an oxidant electrode disposed opposite to the fuel electrode, and an electrolyte layer sandwiched between the fuel electrode and the oxidant electrode, via a fuel permeable vaporizing plate. A fuel cell having a plurality of layers stacked and in which liquid fuel is introduced into the fuel permeation vaporizing plate, comprising: means for directly energizing the fuel permeation vaporizing plate and heating the same.