JP2015141862A - metal-air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-air battery retaining a favorable three-phase interface of a catalyst layer and exhibiting excellent discharge characteristics.SOLUTION: A metal-air battery includes: a metal electrode; an air electrode; an electrolyte layer interposed between the metal electrode and the air electrode; and a water-repellent film provided outside the air electrode. The air electrode comprises a plurality of catalyst layers laminated therein, and the water repellency of the catalyst layers becomes higher toward a water-repellent film side from an electrolyte layer side.

Description

  The present invention relates to a chargeable / dischargeable metal-air battery including a metal electrode using fuel metal and an air electrode using air.

  A metal-air battery is a battery that is composed of a metal electrode, an air electrode, an electrolyte, and the like, and takes out electric energy obtained in the process in which the fuel metal used as fuel is converted into a metal oxide by an electrochemical reaction. is there. In the metal-air battery, typical fuel metals include zinc, iron, magnesium, aluminum, sodium, calcium, and lithium.

  In the air electrode of a metal-air battery, a three-phase interface of electrolyte, air, and catalyst is required to advance the reaction of the catalyst layer. Water and oxygen react with this three-phase interface, and hydroxide ions and As a result, power generation occurs. In order to maintain such a three-phase interface, it was necessary to appropriately control the water repellency of the catalyst layer.

  For example, as shown in FIG. 5, the air battery 200 of Patent Document 1 includes an air electrode composed of a conductive water repellent layer 201 and a catalyst layer 202, and the catalyst layer 202 in contact with the electrolyte solution layer 203 has a catalyst-attached carbon 211. A hydrophilic portion 212 made of carbon and a water repellent portion 214 made of carbon 213 with PTFE are formed, and the hydrophilic portion 212 and the water repellent portion 214 increase the three-phase interface near the catalyst.

JP-A-6-267594

  However, in the above-described air battery in Patent Document 1, the water repellency of the water repellent portion 214 gradually decreases with long-term use, and the electrolytic solution 203 penetrates into the water repellent portion 214 and cannot maintain the three-phase interface. There was a problem.

  Further, there is a problem that it is difficult to uniformly disperse the hydrophilic portion 212 and the water repellent portion 214 in the catalyst layer 202, and the discharge characteristics are likely to vary.

  This invention is made | formed in view of said subject, and it aims at providing the metal-air battery which hold | maintains the favorable three-phase interface of a catalyst layer, and shows the outstanding discharge characteristic.

  The metal-air battery of the present invention is a metal-air battery comprising a metal electrode, an air electrode, an electrolyte solution layer interposed between the metal electrode and the air electrode, and a water-repellent film provided outside the air electrode. The air electrode is characterized in that a plurality of catalyst layers are laminated, and the water repellency of the catalyst layer is increased from the electrolyte layer side toward the water repellent film side.

  In addition, a current collector is provided at an interface where the catalyst layers are stacked.

  Further, the air electrode is disposed so as to face the metal electrode.

  Further, the metal electrode has a rod shape and is arranged at the center of an air electrode formed in a cylindrical shape.

  Further, an auxiliary electrode is provided between the metal electrode and the air electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the metal air battery which hold | maintains the favorable three-phase interface of a catalyst layer, and shows the outstanding discharge characteristic can be provided.

It is a schematic sectional drawing of the metal air battery 101 which concerns on Example 1 of this invention. 2 is an enlarged conceptual view of a catalyst layer in Example 1. FIG. 6 is a schematic cross-sectional view of a metal-air battery 102 according to Example 2. FIG. 6 is a schematic cross-sectional view of a metal-air battery 103 according to Example 3. FIG. It is the conceptual diagram which expanded the cross section of the catalyst layer of the conventional metal air battery.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, a characteristic configuration of the metal-air battery will be described, but a general battery technology can be applied to other configurations.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a metal-air battery 101 according to the present embodiment.

  As shown in FIG. 1, the metal-air battery 101 of Example 1 includes a metal electrode 2, an air electrode 3, and an electrolyte solution layer 4 in a cell 1. Although not shown, the cell 1 may be provided with a precipitate of fuel metal oxide, a separator, or the like. In addition, the metal oxide produced | generated by discharge first exists as a metal ion in electrolyte solution, and when a metal ion concentration becomes high, it will precipitate as a metal oxide.

  At the time of charging, it is reduced from the metal ions in the electrolytic solution and deposited on the fuel supporting metal 21, and the metal ion concentration in the electrolytic solution becomes low. Can be used. Further, by disposing a not-shown separator between the metal electrode 2 and the air electrode 3, the fuel metal dendrite generated in the metal electrode 2 can be short-circuited with the air electrode 3.

  The air electrode 3 is a positive electrode and includes a current collector 31 and a catalyst layer 32. In the air electrode 3, oxygen is taken from outside air through the water repellent film 5, and the reaction with the catalyst proceeds at the three-phase interface of the catalyst layer 32. Details of the catalyst layer 32 will be described later.

  The metal electrode 2 is a negative electrode. In the metal-air battery 101, the metal electrode 2 is formed of a fuel support metal 21 for supporting a fuel metal. The fuel support metal 21 is made of a metal different from the fuel metal and does not chemically react during charge / discharge. As the fuel support metal 21, for example, a metal such as SUS or Ni is used, but the type thereof is not particularly limited. Moreover, the metal electrode 2 is not limited to the structure which consists of fuel support metal 21 single-piece | unit, The structure by which the fuel support metal 21 is formed in the surface by plating etc. may be sufficient.

  The fuel metal is deposited on the surface of the metal electrode 2, that is, the surface of the fuel supporting metal 21 by charging. In addition, the manner of existence of the fuel metal oxide generated by the discharge differs depending on the type of fuel metal used.

  For example, when zinc is used as the fuel metal, zinc oxide generated by discharge is precipitated in the electrolyte layer 4. Of course, the fuel metal that can be used in the metal-air battery 101 is not limited to zinc, and other types of fuel metals (for example, lithium) can also be used.

  The type of electrolyte used for the electrolyte layer 4 is not particularly limited. For example, when zinc is used as the fuel metal, an alkali metal hydroxide such as potassium hydroxide is generally used. Is done.

  The metal-air battery 101 of the present invention maintains a three-phase interface composed of an electrolyte (liquid phase), a catalyst (solid phase), and oxygen (gas phase), which is required for the air electrode 3, and is used for a long time. The electrode 3 is characterized in that a catalyst layer 32 having different water repellency is laminated. FIG. 2 is a conceptual diagram in which the cross section of the catalyst layer 32 of the metal-air battery 101 is enlarged.

  As shown in FIG. 2, the catalyst layer 32 is formed by laminating catalyst layers 32a, 32b, and 32c having different water repellency, and arranged so that the water repellency becomes higher from the electrolyzed liquid layer 4 side toward the water repellent film 5 side. It is out. Each catalyst layer 32 includes a catalyst 35 and a binder resin 36 for promoting the reaction. As said catalyst 35, what added catalyst particles, such as platinum and manganese oxide, on electroconductive particles, such as carbon, is used. Further, a current collector 31 is provided at the interface where the catalyst layer 32 is laminated.

  The water repellency of each of the catalyst layers 32a, 32b, and 32c can be adjusted by, for example, the filling rate of the catalyst 35. In this case, the filling rate of the catalyst 35 is increased and the gap between the catalysts 35 is reduced. Can improve water repellency. Further, by adjusting the filling rate of the catalyst 35, each catalyst layer 32 having different water repellency can be easily formed, and the variation in water repellency in each catalyst layer 32 can be reduced.

  When the metal-air battery 101 is used, the catalyst layer 32a on the side of the electrolyzed liquid layer 4 functions first, and when the water repellency is lowered by continuing use, the main part becomes the original water repellency. It moves to the catalyst layer 32b and the catalyst layer 32c which were high. For this reason, the metal-air battery 101 of the present invention can keep a good three-phase interface for a long period of time.

  In addition, the metal-air battery 101 of the present invention includes the current collector 31 at the interface between the catalyst layer 32a and the catalyst layer 32b and the interface 32c between the catalyst layer 32b and the catalyst layer 32c. Current collection efficiency can be improved, and a decrease in discharge voltage due to long-term use can be suppressed.

  In the metal-air battery 101 according to the first embodiment, the catalyst layer 32 has three layers. However, the catalyst layer 32 may be composed of two or more layers, and is limited to the configuration of the metal-air battery 101 according to the first embodiment. It is not a thing.

  FIG. 3 is a cross-sectional view illustrating a schematic configuration of the metal-air battery 102 according to the second embodiment. Of the metal-air battery 102 according to the second embodiment, components that are the same as those of the metal-air battery 101 according to the first embodiment are denoted by the same reference numerals as those of the metal-air battery 101 according to the first embodiment. Detailed description will be omitted.

  As shown in FIG. 3, the metal-air battery 102 according to the second embodiment includes two air electrodes 3 </ b> A and 3 </ b> B arranged to face each other, and the metal electrode 2 is disposed between the air electrode 3 </ b> A and the air electrode 3 </ b> B. It has a bi-cell structure. The structure of the catalyst layer 32 of the air electrode 3A and the air electrode 3B is the same as that of the metal-air battery 101 shown in the first embodiment.

  By adopting such a bicell structure, the reaction of the air electrode 3 is further promoted, and the discharge voltage and the discharge time can be increased.

  The metal electrode 2 may be a mesh structure instead of a flat plate. By making the metal electrode 2 have a mesh structure, it is possible to prevent the deposited metal from peeling and dropping from the metal electrode 2. This is considered to be because the mesh structure obtains a larger contact area than the flat plate and grows so that the deposited metal covers the voids of the mesh.

  The metal-air battery of the present invention can be applied to a cylindrical structure (not shown) in addition to the bicell structure. In the case of a cylindrical structure, the rod-shaped metal electrode 2 is disposed at the center of the air electrode 3 having a cylindrical shape. The cylindrical air electrode 3 is configured such that the catalyst layer 32 has higher water repellency from the inner electrolyte layer 4 side toward the outer water repellent film 5 side.

  FIG. 4 is a cross-sectional view illustrating a schematic configuration of the metal-air battery 103 according to the third embodiment. Of the metal-air battery 103 of the third embodiment, components that are equivalent to the components of the metal-air battery 102 of the second embodiment are given the same reference numerals as those of the metal-air battery 102 of the second embodiment. Detailed description will be omitted.

  The metal-air battery 103 of Example 3 is a three-pole metal-air battery. The metal-air battery 101 according to the first embodiment and the metal-air battery 102 according to the second embodiment described above are two-pole type batteries including the metal electrode 2 and the air electrode 3, but the present invention is a three-pole type metal-air battery. It is also applicable to.

  As shown in FIG. 4, the metal-air battery 103 according to the third embodiment is further provided with an auxiliary electrode 6 in addition to the metal electrode 2 and the air electrode 3 in the bi-cell structure metal-air battery 102 according to the second embodiment. The auxiliary electrode 6 is disposed between the metal electrode 2 and the air electrode 3 and has a mesh structure so as not to hinder the movement of ions in the electrolytic solution. In the three-pole system to which such an auxiliary electrode 6 is added, deterioration of the air electrode 3 in the two-pole system can be mitigated by using the auxiliary electrode 5 without using the air electrode 3 during charging.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining technical means disclosed in different embodiments. The form is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Cell 2 Metal electrode 3, 3A, 3B Air electrode 4 Electrolyte layer 5 Water repellent film 6 Auxiliary electrode 21 Fuel support metal 31 Current collector 32, 32a, 32b, 32c Catalyst layer 35 Catalyst 36 Binder resin 101, 102, 103 Metal air battery

Claims (5)

A metal-air battery comprising a metal electrode, an air electrode, an electrolyte layer interposed between the metal electrode and the air electrode, and a water repellent film provided outside the air electrode,
The air electrode has a plurality of catalyst layers laminated, and the water repellency of the catalyst layer increases from the electrolyte layer side toward the water repellent film side.   The metal-air battery according to claim 1, wherein a current collector is provided at an interface where the catalyst layers are laminated.   The metal-air battery according to claim 1, wherein the air electrode is disposed opposite to the metal electrode.   The metal-air battery according to claim 1, wherein the metal electrode has a rod shape and is arranged at the center of the air electrode formed in a cylindrical shape.   The metal-air battery according to any one of claims 1 to 3, further comprising an auxiliary electrode between the metal electrode and the air electrode.