JP2004014149A - Liquid fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid fuel cell which is small and can generate electricity stably. <P>SOLUTION: Provided is the liquid fuel cell comprising a positive electrode 8 which reduces oxygen, a negative electrode 10 which comprises a hydrogen storage material, an electrolytic layer 9 provided between the positive electrode 8 and the negative electrode 10, liquid fuel 4 which has a metal hydride dissolved therein, and a liquid fuel storing portion 3 which stores the liquid fuel 4, the positive electrode 8, the negative electrode 10 and the electrolytic layer 9 constituting an electrode/electrolyte integrated product, a plurality of the electrode/electrolyte integrated products being arranged on the same plane and electrically connected to each other in series, the liquid fuel storing portion 3 being separated by a partition 12 for each electrode/electrolyte integrated product. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid fuel cell using a liquid as fuel.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the spread of cordless devices such as personal computers and mobile phones, there is a demand for smaller and higher capacity secondary batteries as power sources. At present, lithium ion secondary batteries have been put to practical use as secondary batteries having a high energy density and can be reduced in size and weight, and demand for portable power sources is increasing. However, depending on the type of cordless device used, this lithium secondary battery has not yet reached a level where sufficient continuous use time is guaranteed.
[0003]
Under such circumstances, an air battery, a fuel cell, or the like can be considered as an example of a battery that can meet the above demand. An air battery is a battery that uses oxygen in the air as an active material of a positive electrode. Since most of the internal volume of the battery can be used for filling the negative electrode, a battery suitable for increasing the energy density is used. It is considered to be. However, this air battery has a problem that the self-discharge is large because an alkaline solution used as an electrolyte reacts with carbon dioxide in the air and deteriorates.
[0004]
In addition, some candidates for the fuel cell to be used are listed as fuel cells, but each has various problems, and a final decision has not been made yet. For example, when pure hydrogen is used as a fuel, it takes time and a huge amount of money to prepare a fuel supply facility such as a hydrogen station. Further, hydrogen is a very light combustible gas, so its handling is difficult, and there is a problem in terms of safety. Further, when gasoline is used as fuel and reforming gasoline to extract hydrogen requires a reformer, there are also problems such as the efficiency of reforming being not very high. Also, when methanol is used as a fuel, the same problem as gasoline occurs when reformed methanol is used.If methanol is used as fuel without reforming, the output, efficiency, etc. will be reduced, and There is a problem that a certain amount of methanol permeates the electrolyte membrane.
[0005]
[Problems to be solved by the invention]
On the other hand, an alkaline fuel cell using a metal hydride such as NaBH ₄ , KBH ₄ , LiAlH ₄ , KH, and NaH as a fuel and using a hydrogen storage alloy as a negative electrode is supplied with fuel to the negative electrode and reacts with the positive electrode. Reacts. Therefore, it can be used continuously as long as fuel and oxygen are supplied. However, since the conventional fuel cell is configured by stacking a plurality of unit cells, the whole cell becomes bulky. In addition, oxygen and fuel must be circulated and supplied to the respective positive electrode and negative electrode, and an auxiliary device for that purpose is required. For this reason, the conventional fuel cell is much larger than a small secondary battery such as a lithium ion battery, and there is a problem in using it as a small portable power supply.
[0006]
Here, although the output is reduced by removing the auxiliary device for forcibly flowing the oxygen and the fuel, the size of the fuel cell can be reduced. However, in this case, a structure that can supply the fuel to each negative electrode of the unit cell is required because the fuel does not automatically flow even if outside air is used for oxygen.
[0007]
The present invention has been made to solve the above-mentioned conventional problems, and provides a liquid fuel cell which is small and capable of stably generating power.
[0008]
[Means for Solving the Problems]
The liquid fuel cell of the present invention has a positive electrode for reducing oxygen, a negative electrode provided with a hydrogen storage material, and an electrolyte layer provided between the positive electrode and the negative electrode, and has a metal hydride dissolved therein. A liquid fuel cell comprising a liquid fuel and a liquid fuel storage unit for storing the liquid fuel, wherein the positive electrode, the negative electrode, and the electrolyte layer constitute an electrode-electrolyte integrated body, A plurality of electrolyte monoliths are arranged on the same plane, each electrode / electrolyte monolith is electrically connected in series, and the liquid fuel storage unit is separated by a partition wall for each electrode / electrolyte monolith. Features.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0010]
The liquid fuel cell of the present invention has a positive electrode for reducing oxygen, a negative electrode provided with a hydrogen storage material, and an electrolyte layer provided between the positive electrode and the negative electrode, and has a metal hydride dissolved therein. A liquid fuel cell comprising a liquid fuel and a liquid fuel storage unit for storing the liquid fuel, wherein the positive electrode, the negative electrode, and the electrolyte layer constitute an electrode-electrolyte integrated body, A plurality of the electrolyte integrated materials are arranged on the same plane, the respective electrode / electrolyte integrated materials are electrically connected in series, and the liquid fuel storage unit is separated by a partition wall for each of the electrode / electrolyte integrated materials.
[0011]
In the liquid fuel cell of the present invention, the positive electrode, the negative electrode, and the electrolyte layer constitute an electrode-electrolyte integrated body, and a plurality of the electrode-electrolyte integrated bodies are arranged on the same plane. It is possible to do. In addition, since each electrode / electrolyte integrated body is electrically connected in series, high output can be exhibited even with a small size. Further, since the liquid fuel storage section is separated by the partition wall for each electrode / electrolyte integrated material, no short circuit occurs between cells even when using liquid fuel in which metal hydride is dissolved.
[0012]
In addition, it is preferable that an on-off valve that can communicate the separated liquid fuel storage units is provided on the partition wall of the liquid fuel storage unit. This is because when replenishing the fuel, the fuel can be continuously supplied from one fuel filling port to each liquid fuel storage unit.
[0013]
Preferably, the liquid fuel storage unit includes a gas-liquid separation hole in which a gas-liquid separation membrane is disposed. This is because unnecessary gas generated when the fuel cell is used is discharged without causing the liquid fuel to leak.
[0014]
Further, it is preferable that a liquid fuel impregnated portion that impregnates and holds the liquid fuel and supplies the liquid fuel to the negative electrode is provided, and the liquid fuel impregnated portion is disposed at a portion in contact with the negative electrode. This is because even if the fuel is consumed, the contact between the fuel and the negative electrode is maintained, so that the fuel can be completely used up.
[0015]
Further, it is preferable that the hydrogen storage material is one selected from the group consisting of a hydrogen storage alloy and a carbon nanotube. This is because they have excellent hydrogen storage capacity.
[0016]
Preferably, the metal hydride is at least one selected from the group consisting of NaBH ₄ , KBH ₄ , LiAlH ₄ , KH and NaH. This is because they can be easily dissolved in water and supply a large amount of hydrogen per unit mass.
[0017]
The electrolyte layer preferably contains an alkaline aqueous solution in which at least one selected from the group consisting of KOH, NaOH and LiOH is dissolved. This is because high ionic conductivity can be imparted.
[0018]
Next, an embodiment of the present invention will be described with reference to the drawings.
[0019]
(Embodiment 1)
FIG. 1 shows a sectional view of a liquid fuel cell according to Embodiment 1 of the present invention. The positive electrode 8 is formed, for example, by laminating a carbon layer 8b made of porous carbon powder and carbon powder carrying a catalyst, and a gas-liquid separation sheet 8a made of polytetrafluoroethylene (PTFE). The positive electrode 8 has a function of reducing oxygen, and its performance can be improved by supporting a catalyst on carbon. As the catalyst, silver, platinum, ruthenium, iridium oxide, rare earth oxide, manganese oxide, or an alloy containing at least silver, platinum, or ruthenium is used. Further, the positive electrode 8 contains PTFE resin particles.
[0020]
As the electrolyte of the present invention, any electrolyte may be used as long as it is in a liquid state, but an aqueous alkali solution is particularly preferably used. As the alkaline aqueous solution as the electrolyte, for example, a solution in which a hydroxide of an alkali metal such as KOH, NaOH and LiOH is dissolved in water at a concentration of about 20 to 40% by mass is preferable, and includes a plurality of hydroxides of an alkali metal. Some mixed electrolytes can also be used.
[0021]
In order to form the electrolyte layer while holding the above electrolyte, a separator 9 is disposed between the positive electrode 8 and the negative electrode 10. The material of the separator 9 is not particularly limited as long as it is stable with respect to the electrolyte. For example, a nonwoven fabric such as polypropylene and polyethylene is used. Furthermore, when water is used as the electrolyte solvent, it is preferable to subject the surface of the separator 9 to a hydrophilic treatment.
[0022]
As the hydrogen supply source of the liquid fuel of the present invention, a metal hydride is used. As the metal hydride, for example, NaBH ₄ , KBH ₄ , LiAlH ₄ , KH, NaH and the like are preferably used, and particularly, NaBH ₄ Is preferably used. This is because NaBH ₄ is more stable than other metal hydrides in water or an aqueous alkali solution, and has a mild reaction with a hydrogen storage alloy. The metal hydride as a hydrogen supply source can be used in a state of being dissolved or mixed in a liquid electrolyte.
[0023]
The negative electrode 10 is formed by fixing a hydrogen storage material to a conductive substrate, and has a function of oxidizing fuel. As the hydrogen storage material, a carbon material such as a hydrogen storage alloy or a carbon nanotube can be used, and a hydrogen storage alloy is particularly suitable. Although the hydrogen storage alloy is not particularly limited, for example, an AB _5- type hydrogen storage alloy represented by LaNi ₅ , an AB _2- type hydrogen storage alloy represented by ZnMn ₂ or a substitute thereof, Mg ₂ Ni Alternatively, a magnesium-based A ₂ B-type hydrogen storage alloy, a solid solution-type vanadium-based hydrogen storage alloy, or the like represented by a substitute thereof may be used. Among them, use of a misch metal (Mm) which is a mixture of rare earth elements, and AB ₅ type hydrogen storage alloy part of MmNi ₅ system was replaced with such as Co and Ni are particularly preferably used. This is because they have excellent hydrogen storage / release capabilities.
[0024]
The conductive substrate of the negative electrode 10 may be any substrate made of a material having corrosion resistance to the electrolyte and capable of obtaining electrical contact from the hydrogen storage material. For example, a punching metal made of nickel or nickel-plated iron, A foamed metal body or the like is used.
[0025]
As the binder for fixing the hydrogen storage material of the negative electrode 10 to the conductive substrate, any material may be used as long as it is chemically stable and sticky in the electrolyte. For example, polytetrafluoroethylene, latex, or the like is used. be able to.
[0026]
The positive electrode 8, the separator 9 constituting the electrolyte layer, and the negative electrode 10 are laminated in this order from the air hole 1 side to the positive electrode 8, the separator 9, and the negative electrode 10 to form an integrated electrode / electrolyte. Further, a plurality of the electrode / electrolyte integrated materials are arranged on the same plane.
[0027]
A fuel tank 3 for storing the liquid fuel 4 is provided adjacent to the side of the negative electrode 10 opposite to the separator 9. The fuel tank 3 is made of, for example, a plastic such as polytetrafluoroethylene, hard polyvinyl chloride, polypropylene, or polyethylene, or a corrosion-resistant metal such as stainless steel. However, when the fuel tank 3 is made of metal, it is necessary to introduce an insulator so that the respective negative electrodes arranged on the same plane do not short-circuit electrically. A fuel supply hole 3a is provided in a portion of the fuel tank 3 in contact with the negative electrode 10, and the liquid fuel 4 is supplied to the negative electrode 10 from this portion. Further, a fuel wicking material 5 which impregnates and holds the liquid fuel 4 and supplies the liquid fuel 4 to the negative electrode 10 is disposed inside the fuel tank 3 including a portion in contact with the negative electrode 10. Thereby, even if the liquid fuel 4 is consumed, the contact between the liquid fuel 4 and the negative electrode 10 is maintained, so that the liquid fuel 4 can be completely used up. As the fuel wicking material 5, a nonwoven fabric made of glass fiber, plastic stable against liquid fuel, or the like can be used. However, the material does not change much due to impregnation with liquid fuel and is chemically stable. Any other material may be used.
[0028]
In the present invention, a metal hydride dissolved in an alkaline aqueous solution is used as a hydrogen supply source. However, since the alkaline aqueous solution has electric conductivity, the fuel tank 3 installed for each electrode / electrolyte integrated body is electrically insulated. In addition, it is necessary to prevent a short circuit between the cells due to the liquid fuel 4. Therefore, the fuel tank 3 installed for each electrode / electrolyte integrated material is separated by the partition 12 for each electrode / electrolyte integrated material. However, an on-off valve 11 is provided between each fuel tank 3 so that fuel can be supplied to each fuel tank 3 from one fuel filling port 6b during fuel supply.
[0029]
A cover plate 2 is provided on the side of the positive electrode 8 opposite to the separator 9, and an air hole 1 is provided in a portion of the cover plate 2 that contacts the positive electrode 8. Thereby, oxygen in the atmosphere comes into contact with the positive electrode 8 through the air hole 1. At the end of the cover plate 2, a gas-liquid separation hole / fuel filling port 6 b having a structure penetrating the cover plate 2 and the fuel tank 3 is provided. A detachable gas-liquid separation film 6a is provided on the opposite side of the fuel tank 3 from the gas-liquid separation hole / fuel filling port 6b. The gas-liquid separation membrane 6a is made of a PTFE sheet having pores, and discharges hydrogen and the like that have not been used after the anode and the metal hydride have reacted and discharged from the fuel tank 3 without leaking the fuel. be able to. Further, by making the gas-liquid separation film 6a detachable, fuel can be replenished from the gas-liquid separation hole / fuel filling hole 6b. The gas-liquid separation hole / fuel filling port 6b, the cover plate 2, and the air hole 1 are made of, for example, the same material as the fuel tank 3.
[0030]
A current collector 7 is provided between the positive electrode 8 and the adjacent electrode / electrolyte integrated material negative electrode 10, and the positive electrode 8 is electrically connected to the adjacent electrode / electrolyte integrated material negative electrode 10. I have. The current collector 7 has a role of electrically connecting adjacent electrode / electrolyte integrated bodies in series, and all the electrode / electrolyte integrated bodies arranged on the same plane are electrically connected in series by the current collector 7. Is done. The current collector 7 is made of, for example, a noble metal such as platinum or gold, a corrosion-resistant metal plated with nickel or nickel, or carbon.
[0031]
(Embodiment 2)
FIG. 2 shows a sectional view of a liquid fuel cell according to Embodiment 2 of the present invention. This embodiment has the same structure as the first embodiment except that the upper and lower parts of the fuel tank 3 are formed symmetrically.
[0032]
(Embodiment 3)
FIG. 3 shows a sectional view of a liquid fuel cell according to Embodiment 3 of the present invention. This embodiment has a structure in which two liquid fuel cells of the first embodiment are stacked so that an air hole 1 and a cover plate 2 face each other. A gap is provided between the facing air holes 1 and the cover plate 2 to diffuse air. The current collector 7 is connected so that all the electrode / electrolyte integrated bodies are electrically connected in series. Further, all the fuel tanks 3 are also connected by a bypass having an on-off valve 11, and the liquid fuel 4 can be circulated by opening the on-off valve 11. Other configurations of the present embodiment are almost the same as those of the first embodiment.
[0033]
【The invention's effect】
As described above, the present invention includes a positive electrode for reducing oxygen, a negative electrode including a hydrogen storage material, and an electrolyte layer provided between the positive electrode and the negative electrode, and dissolving a metal hydride. A liquid fuel, and a liquid fuel storage unit for storing the liquid fuel, wherein the positive electrode, the negative electrode, and the electrolyte layer constitute an electrode-electrolyte integrated body, the electrode・ By arranging a plurality of the electrolyte integrated bodies on the same plane, electrically connecting each electrode / electrolyte integrated body in series, and separating the liquid fuel storage unit by the partition wall for each of the electrode / electrolyte integrated bodies, It is possible to provide a liquid fuel cell that is small and capable of stably generating power.
[Brief description of the drawings]
FIG. 1 is a sectional view of a liquid fuel cell according to Embodiment 1 of the present invention.
FIG. 2 is a sectional view of a liquid fuel cell according to Embodiment 2 of the present invention.
FIG. 3 is a sectional view of a liquid fuel cell according to Embodiment 3 of the present invention.
[Explanation of symbols]
Reference Signs List 1 air hole 2 cover plate 3 fuel tank 3a fuel supply hole 4 liquid fuel 5 fuel sucking material 6a gas-liquid separation film 6b gas-liquid separation hole and fuel filling port 7 current collector 8 positive electrode 8a gas-liquid separation sheet 8b carbon layer 9 separator 10 Negative electrode 11 Open / close valve 12 Partition wall

Claims (7)

A positive electrode for reducing oxygen, a negative electrode provided with a hydrogen storage material, and an electrolyte layer provided between the positive electrode and the negative electrode, a liquid fuel in which metal hydride is dissolved, and the liquid fuel A liquid fuel cell comprising a liquid fuel storage unit for storing, wherein the positive electrode, the negative electrode, and the electrolyte layer constitute an electrode-electrolyte integrated body, and the electrode-electrolyte integrated body is on the same plane. A liquid fuel cell, wherein a plurality of the electrode / electrolyte integrated bodies are electrically connected in series, and the liquid fuel storage unit is separated by a partition wall for each of the electrode / electrolyte integrated bodies. 2. The liquid fuel cell according to claim 1, wherein an on-off valve capable of communicating the separated liquid fuel storage units is provided on a partition wall of the liquid fuel storage unit. 3. The liquid fuel cell according to claim 1, wherein the liquid fuel storage unit includes a gas-liquid separation hole in which a gas-liquid separation membrane is disposed. 2. The liquid fuel according to claim 1, further comprising a liquid fuel impregnating section that impregnates and holds the liquid fuel and supplies the liquid fuel to the negative electrode, wherein the liquid fuel impregnating section is disposed at a portion in contact with the negative electrode. 3. battery. The liquid fuel cell according to claim 1, wherein the hydrogen storage material is one selected from the group consisting of a hydrogen storage alloy and a carbon nanotube. The metal _{hydride, NaBH 4, KBH 4, LiAlH} 4, liquid fuel cell according to claim 1 from the group consisting of KH and NaH at least one selected. The liquid fuel cell according to claim 1, wherein the electrolyte layer includes an alkaline aqueous solution in which at least one selected from the group consisting of KOH, NaOH, and LiOH is dissolved.

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