JP6499351B2 - Air electrode and metal-air battery - Google Patents

Description

The present invention relates to an air electrode and a metal-air battery. More specifically, the present invention relates to an air electrode used for a long-life metal-air battery in which leakage of an electrolytic solution is prevented, and a metal-air battery including the air electrode.

A metal-air battery is composed of a metal electrode (negative electrode), an air electrode (positive electrode), and an electrolytic solution, and has a high energy density. Therefore, development and research for practical use are being promoted.

One side of the air electrode of the metal-air battery is in contact with the electrolyte, while the other side is in contact with the air. Since the air electrode uses oxygen in the air as an active material, air holes are usually provided to take air into the air electrode, and the air electrode has a porous structure. In addition, as the electrolytic solution, for example, an alkaline aqueous solution that reduces the surface tension of water and increases permeability is used. Due to the structure of the air electrode, the property of the electrolyte, and the like, the electrolyte penetrates inside the air electrode (the porous air electrode catalyst layer 515 and the mesh-like air electrode conductive layer 513) and leaks outside the air electrode. There is a problem (see, for example, FIG. 11).
If the electrolyte leaks, the battery performance will be significantly reduced, long-term reliability cannot be ensured (long life), and there will be problems in terms of safety such as battery users coming into contact with the electrolyte. is there.

With respect to these problems, an air battery including a specific air electrode catalyst layer made of a mixture of a catalyst, activated carbon, and a fluororesin is known (for example, see Patent Document 1). In addition, a specific air battery in which a porous polytetrafluoroethylene (PTFE) film is disposed on the outside (air side) of the air electrode is known (for example, see Patent Document 2). Furthermore, the air electrode provided on the side surface of the battery case and a metal cathode are operated by injecting the electrolyte solution or water, and the electrolyte solution is adsorbed with the passage of time in the battery case. An injection-type air battery that incorporates a solidifying agent to be solidified is disclosed (for example, see Patent Document 3).

JP-A-6-338355 Japanese Patent Laid-Open No. 8-7935 JP 54-129327 A

As described above, the conventional metal-air battery has a problem that the electrolytic solution penetrates inside the air electrode and leaks outside the air electrode.
On the other hand, as described in Patent Document 1, by mixing a fluorine resin having high water repellency inside the air electrode such as the air electrode catalyst layer, it is possible to suppress leakage of the electrolyte in the short term. However, even if such measures are taken, in conventional metal-air batteries, the electrolyte may leak through voids (oxygen diffusion paths) formed in the air electrode catalyst layer, and water repellent Even with high fluororesins, the water repellency gradually decreases due to high-concentration electrolyte (KOH aqueous solution), etc., so the electrolyte leaked out in the long term and long-term reliability and safety could not be secured. .
Further, as described in Patent Document 2, a metal-air battery having a porous polytetrafluoroethylene film outside the air electrode is known in order to prevent leakage of the electrolytic solution. However, if a porous PTFE membrane is disposed outside the air electrode (air side), the water repellency of the fluororesin may gradually decrease, and the electrolyte may leak through the air electrode. May decrease. In addition, the leaked electrolyte accumulates between the air electrode and the porous PTFE membrane, obstructing the air supply and deteriorating battery characteristics.

Furthermore, the invention described in the above-mentioned Patent Document 3 solidifies the electrolytic solution in the electrolytic solution tank by installing a solidifying agent for solidifying the electrolytic solution in the electrolytic solution tank, and reduces its fluidity. The leakage of electrolyte from the air electrode is prevented. However, when the electrolytic solution is solidified, ionic conduction in the electrolytic solution is lowered, so that a high output cannot be obtained.

The present invention has been made in view of the above situation, and provides an air electrode excellent in reliability and safety, and a metal-air battery including the air electrode, which prevents leakage of electrolyte in the metal-air battery. It is intended.

As a result of various studies on metal-air batteries capable of preventing leakage of the electrolytic solution, the present inventors have found that the air electrode provided with a water-absorbing layer containing a water-absorbing polymer on the other surface where the air electrode is in contact with the electrolytic solution. Found the configuration. And according to the metal-air battery comprising at least the air electrode having such a configuration, an electrolytic solution tank that stores the electrolytic solution, and a metal electrode that is provided in the electrolytic solution tank and serves as an anode, The inventors have arrived at the present invention by conceiving that the problem can be solved.

In addition, the invention described in Patent Document 1 suppresses leakage of the electrolytic solution with a fluororesin (PTFE or the like) disposed in the air electrode catalyst layer, and the invention described in Patent Document 2 describes the outside of the air electrode ( The porous PTFE membrane placed on the air side) suppresses leakage of the electrolyte, and the invention described in Patent Document 3 suppresses leakage of the electrolyte by a solidifying agent incorporated in the electrolyte bath. On the other hand, the present invention is different in that the water-absorbing polymer provided in the water-absorbing layer on the outside (air side) of the air electrode holds the electrolytic solution.

That is, one embodiment of the present invention is an air electrode used for a positive electrode of a metal-air battery, and the air electrode includes a catalyst layer, a conductive layer, and a water absorbing layer, and the water absorbing layer is a water absorbing polymer. And an air electrode provided on one side with respect to the catalyst layer and the conductive layer.

Another aspect of the present invention is a metal-air battery including the air electrode, an electrolyte bath, and a metal electrode, wherein the water absorption layer of the air electrode is disposed outside the catalyst layer and the conductive layer. It may be a metal-air battery.

Since the air electrode and the metal-air battery of the present invention have the above-described configuration, it is possible to prevent leakage of the electrolytic solution in the metal-air battery and realize a metal-air battery excellent in reliability and safety.

It is a cross-sectional schematic diagram which shows the whole structure of the metal air battery of Embodiment 1. 3 is a schematic cross-sectional view showing the structure of the air electrode according to Embodiment 1. FIG. 1 is a schematic cross-sectional view illustrating an overall configuration of an air electrode according to Embodiment 1. FIG. 6 is a schematic cross-sectional view showing an overall configuration of an air electrode according to Embodiment 2. FIG. 6 is a schematic cross-sectional view showing an overall configuration of an air electrode according to Embodiment 3. FIG. It is a cross-sectional schematic diagram which shows the structure of the diffusion layer used with the metal air battery of Embodiment 3, and respond | corresponds to the cross section along the A1-A2 line in FIG. 6 is a schematic cross-sectional view showing the overall configuration of an air electrode according to Embodiment 4. FIG. It is a cross-sectional schematic diagram which shows the structure of the diffusion layer used with the metal air battery of Embodiment 4, and respond | corresponds to the cross section along the B1-B2 line in FIG. It is a cross-sectional schematic diagram which shows the structure of the water absorption layer used with the metal air battery of Embodiment 4, and respond | corresponds to the cross section along the C1-C2 line | wire in FIG. 6 is a schematic cross-sectional view showing an overall configuration of an air electrode according to Embodiment 5. FIG. It is a cross-sectional schematic diagram which expands and shows the structure of the catalyst layer with which the air electrode structure and air electrode of the conventional metal air battery are equipped.

Embodiments will be described below, and the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited only to these embodiments. Note that in each embodiment, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings except that the hundreds are changed, and repeated description thereof is omitted.
In addition, the configurations of the respective embodiments may be appropriately combined or changed within a range not departing from the gist of the present invention.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view showing the overall configuration of the metal-air battery according to Embodiment 1 of the present invention.
The metal-air battery EC of Embodiment 1 includes a metal-air battery casing, a metal electrode (negative electrode) A, an air electrode (positive electrode) C, an electrolyte (KOH aqueous solution) E, and a separator S. The metal electrode (negative electrode) A is disposed at a position in contact with the electrolytic solution E. The electrolytic solution E is held in an electrolytic solution tank (not shown).
The metal-air battery housing is provided with holes H, which function as oxygen diffusion paths and the like.

The injection port I of the electrolytic bath is normally closed before injection. The electrolyte E may be provided in advance in a cell (electrolyte tank) or may be injected from an external tank or the like via a pump or the like immediately before using the battery. The liquid to be poured may be an electrolytic solution containing an electrolyte, and pure water or the like may be injected from the outside after the electrolyte is provided in a cell (electrolyte tank). In the zinc-air battery of Embodiment 1, an aqueous potassium hydroxide solution can be used as the electrolytic solution.
The separator S is one or more diaphragms for preventing the negative electrode (for example, zinc electrode) active material and the negative electrode reaction product from permeating the air electrode (positive electrode) C. The arrangement of the separator S is not limited between the air electrode C and the electrolytic solution E. For example, the separator S may be provided between the metal electrode A and the electrolytic solution E. Further, the separator S is not an essential configuration, and the air electrode C may be in direct contact with the electrolytic solution E.
The metal electrode A (negative electrode) is composed of a metal or metal alloy active material suitable for a metal-air battery.
Details of the metal-air battery EC will be described later.

FIG. 2 is a schematic cross-sectional view illustrating the structure of the air electrode according to the first embodiment.
The air electrode C (positive electrode) of Embodiment 1 is configured by arranging an air electrode catalyst layer 15, an air electrode conductive layer 13, and a water absorption layer 11 in this order from the electrolyte bath side to the air side. The arrangement of the air electrode conductive layer 13 is not particularly limited, and may be in the order of the air electrode conductive phase 13, the air catalyst layer 15, and the water absorption layer 11 from the electrolyte tank side to the air side. The air electrode catalyst layer 15, the air electrode conductive layer 13, the air electrode catalyst layer 15, and the water absorption layer 11 may be arranged in this order from the electrolytic solution tank side to the air side.

FIG. 3 is a schematic cross-sectional view illustrating the entire configuration of the air electrode C according to the first embodiment. When a metal-air battery including the air electrode C is configured, the left side in FIG. 3 is the electrolyte layer side, and the right side is the air side (outside). The same applies to FIGS. 4, 5, 7, and 10 described later.
The air electrode C of Embodiment 1 includes an air electrode catalyst layer 15, an air electrode conductive layer (current collector) 13, and a water absorption layer 11, and includes the air electrode catalyst layer 15 and the air electrode conductive layer (current collector) 13. The water-absorbing layer 11 containing a water-absorbing polymer is provided on the air side (the side opposite to the electrolyte bath side). Thereby, leakage of the electrolyte solution in the metal-air battery can be prevented, and the effect of the present invention for realizing a metal-air battery excellent in reliability and safety can be exhibited.
The air electrode C is not limited to that shown in FIG. 3, but preferably includes at least an air electrode catalyst layer, an air electrode conductive layer, and a water absorption layer, and more preferably integrated with a separator.
The air electrode conductive layer 13 used in Embodiment 1 is not particularly limited as long as it is a metal used as a current collector in a battery. For example, nickel is preferable. Further, the configuration of the air electrode conductive layer is not particularly limited, but the air electrode conductive layer is preferably in a mesh shape.
The air electrode catalyst layer 15 used in the first embodiment includes an electron conductive material (for example, carbon) 21, an electrode catalyst 17, and a fluororesin 19. The air electrode catalyst layer 15 preferably contains at least one of an electrode catalyst and a fluororesin, and more preferably contains an electron conductive substance. Examples of the fluororesin 19 include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and the like.
There are a plurality of voids 23 in the air electrode catalyst layer 15. Thus, the air electrode catalyst layer 15 is preferably porous. In the present specification, the porous material in the air electrode catalyst layer may be any material as long as voids communicate with each other and air (oxygen) can be passed as an oxygen diffusion path. The porous pore diameter in the air electrode catalyst layer is preferably 5 μm or less from the viewpoint of suppressing permeation of the negative electrode reaction product.

In the metal-air battery including the air electrode C according to the first embodiment, with the passage of time, the electrolytic solution gradually permeates the air electrode toward the water absorption layer on the air side. Thereafter, the electrolytic solution is leached from a part of the air electrode conductive layer 13 of the air electrode C of Embodiment 1 on the air side, and is held by the water absorbing polymer inside the water absorbing layer 11.
The water absorbing layer 11 is a layer provided with at least a water absorbing portion composed of at least a water absorbing polymer. It is preferable that the water absorbing layer 11 appropriately contains an electron conductive material such as carbon in addition to the water absorbing polymer.
As the water-absorbing polymer, a highly water-absorbing polymer or a water-soluble polymer can be used, and a material excellent in alkali resistance is preferably used.
Examples of the superabsorbent polymer include cross-linked polyacrylate and 2-acrylamido-2-methylpropanesulfonic acid having a sulfo group as a hydrophilic group. Moreover, although the kind of polyacrylate is not specifically limited, For example, polyacrylic acid sodium, polyacrylic acid potassium, polyacrylic acid calcium, and polyacrylic acid magnesium can be mentioned.
Examples of water-soluble polymers include starch-based acrylonitrile graft copolymers, acrylic acid graft copolymers, acrylamide graft copolymers, cellulose-based acrylonitrile graft copolymers, carboxymethylcellulose cross-linked polymers, Sugar-based hyaluronic acid, polyvinyl alcohol-based polyvinyl alcohol cross-linked product, polyvinyl alcohol water-absorbing gel freeze / thaw elastomer, acrylic acid-based acrylic acid / sodium vinyl alcohol copolymer, cross-linked sodium polyacrylate, acrylamide-based N-substituted acrylamide cross-linked products can be used.
These highly water-absorbing polymers or water-soluble polymers can increase the amount of water absorption by increasing the crosslinking density, and can be adjusted as appropriate. A crosslinking agent, a polymerization initiator, or the like may be used to adjust the crosslinking density.
The water absorption amount of the water-absorbing polymer is not particularly limited, but is preferably 100 mL / g or more, and more preferably 1000 mL / g or more. For example, when cross-linked potassium polyacrylate is used as the water-absorbing polymer, it is possible to absorb water from several hundred to about 1000 times the weight of the used cross-linked potassium polyacrylate. Therefore, by using the cross-linked potassium polyacrylate, the water absorbing layer 11 can be formed thin or formed into a film, so that the amount of potassium polyacrylate can be small and can be reduced at low cost.
Further, when an alkaline aqueous solution is used as the electrolytic solution E, the cross-linked potassium polyacrylate has excellent alkali resistance, so that the material deterioration is small, and the frequency can be reduced even if the water absorption layer 11 needs to be replaced.
The layer thickness of the water-absorbing layer 11 is not particularly limited, but as the layer thickness increases, the leaching of the electrolytic solution E can be prevented. Specifically, the thickness is preferably 0.01 mm or more, and 0.05 mm or more. Is more preferable, 0.1 mm or more is further preferable, and 0.3 mm or more is particularly preferable. On the other hand, from the viewpoint of electrical characteristics, the layer thickness is preferably 10 mm or less, more preferably 5 mm or less, still more preferably 2.0 mm or less, and particularly preferably 1.0 mm or less.
The layer thickness of the water absorbing layer means that calculated by averaging the thickness of the entire water absorbing layer.

(Effect of Embodiment 1)
In the metal-air battery including the air electrode C according to the first embodiment, the water-absorbing polymer (water-absorbing part) provided in the water-absorbing layer 11 holds (gels) the electrolytic solution E, and the electrolytic solution E is outside the air electrode C. Leakage can be prevented.
In the metal-air battery of the first embodiment, since the electrolyte E does not leak to the outside, adverse effects on the environment can be eliminated, and the risk of battery users and the like directly touching the electrolyte is reduced.
In the metal-air battery of the first embodiment, since the ion conduction inside the battery is not rate-limiting, a high output can be obtained (if the electrolyte is held (gelled) inside the electrolyte bath or the air electrode, the ion conductivity decreases). Therefore, high output cannot be obtained.)

Hereinafter, the air electrode C of Embodiment 1 will be described in detail. The preferable configuration of the air electrode of Embodiment 1 is the same as the preferable configuration of the air electrode of Embodiments 2 to 5 described later.

The air electrode C is used as a positive electrode (cathode) of the metal-air battery EC, and is an electrode that generates hydroxide ions (OH ⁻ ) from oxygen gas, water, and electrons in the atmosphere. Similarly to the metal electrode A, the electrode main surface is provided in the electrolytic solution tank so as to be parallel to the direction of gravity. The electrode main surface of the metal electrode A and the electrode main surface of the air electrode C are opposed to each other.

The electron conductive material 21 contained in the air electrode catalyst layer 15 of the air electrode C is preferably, for example, a conductive porous carrier. Further, it is more preferable that the electrode catalyst 17 is supported on the electron conductive material 21. According to such a configuration, oxygen gas, water, and electrons can coexist on the electrode catalyst 17, and the electrode reaction can proceed efficiently. The electrode catalyst 17 is preferably made fine particles and supported on a porous carrier. The water used for the electrode reaction may be supplied from the atmosphere or supplied from the electrolytic solution E.

Examples of porous carriers include carbon black such as acetylene black, furnace black, channel black, and ketjen black; conductive carbon particles such as graphite and activated carbon; vapor grown carbon fiber (VGCF), carbon nanotube, and carbon nanowire. Carbon fibers such as can be used.
The porous carrier may be surface-treated so that a cationic group exists as a fixed ion on the surface thereof. As a result, hydroxide ions can be conducted on the surface of the porous carrier, so that the hydroxide ions generated on the electrode catalyst 17 can easily move.
Moreover, it is preferable that the air electrode catalyst layer 15 of the air electrode C contains a fluororesin as described above. The fluororesin can impart water repellency to the air electrode catalyst layer 15 and suppress the permeation of the electrolytic solution E. The fluororesin also functions as a binder and can bind the porous carriers in the air electrode catalyst layer 15 to improve the strength of the air electrode C.

Examples of the electrode catalyst 17 include platinum (Pt), gold (Au), iron (Fe), cobalt (Co), nickel (Ni), titanium (Ti) palladium (Pd), silver (Ag), and copper (Cu). ), Ruthenium (Ru), iridium (Ir), selenium (Ce), tungsten (W), vanadium (V), molybdenum (Mo), manganese (Mn), niobium (Nb), and other metals; Metal compounds containing; alloys containing two or more of these metals can be used. The alloy is preferably an alloy containing at least two of platinum, iron, cobalt, and nickel. For example, platinum-iron alloy, platinum-cobalt alloy, iron-cobalt alloy, cobalt-nickel alloy, iron-nickel An alloy and an iron-cobalt-nickel alloy can be preferably used.
As the electrocatalyst 17, oxides or nitrides such as W, Ce, Ni, V, Ti, Co, Mo, Fe, Cu, Nb, and Mn can be used alone or in combination of two or more. Further, as the electrode catalyst 17, noble metals such as Pt, Ru, Au, Ag, Pd, and Ir, and oxidation of W, Ce, Ni, V, Ti, Co, Mo, Fe, Cu, Zn, Nb, Mn, and the like Two or more kinds of nitrides and nitrides may be used in combination as the air electrode catalyst 18.
The electrode catalyst 17 may be one in which the above-described metal or alloy is supported on carbon, and is preferably platinum-supported carbon, for example.

(Procedure for manufacturing the air electrode C and the like of the first embodiment)
Hereinafter, an example of a procedure for producing the air electrode according to Embodiment 1 will be described in detail, but the procedure is not limited to this, and can be changed as appropriate.
(1) Preparation of the air electrode catalyst layer 15 The electrode catalyst 17, the electron conductive material 21, and the fluororesin 19 are mixed and stirred, and the resulting mixture is passed through a pressure roller to form a sheet-like air electrode catalyst layer 15. Get.
(2) Preparation of water-absorbing layer 11 The electron conductive substance 21 and the water-absorbing polymer are mixed and stirred, and the resulting mixture is passed through a pressure-rolling roller to obtain a sheet-like water-absorbing layer.
(3) Production of the air electrode C The air electrode conductive layer 13 is pressure-bonded so as to be sandwiched between the sheet-like air electrode catalyst layer 15 obtained in (1) and the sheet-like water absorption layer 11 obtained in (2). The integrated product is formed into an air electrode C.

Hereinafter, the metal-air battery EC of Embodiment 1 will be described in detail. The preferred configuration of the metal-air battery of Embodiment 1 is the same as the preferred configuration of the metal-air batteries of Embodiments 2 to 5 described later.

In the metal-air battery EC of the first embodiment, the air electrode C may be provided in direct contact with the atmosphere via the holes H, or may be provided in contact with an air flow path (not shown). Thereby, oxygen gas can be supplied to the air electrode C. Moreover, when providing an air flow path, water can be supplied to the air electrode C together with oxygen gas by flowing humidified air through the air flow path.

Moreover, you may provide the air electrode C so that the electrolyte solution E in an electrolyte solution tank may be contacted. Thus, hydroxide ions generated at the air electrode C can easily move to the electrolytic solution E. Further, water necessary for the electrode reaction at the air electrode C is easily supplied from the electrolytic solution E to the air electrode C.

Since the electrolytic solution tank is a container in which the electrolytic solution E is stored, the electrolytic solution tank is preferably formed of a material having corrosion resistance to the electrolytic solution E. It is preferable that the metal electrode A can be attached to the inside of the electrolytic solution tank, and the air electrode C can be attached to the outer wall portion of the electrolytic solution tank.

The electrolytic solution E is a liquid having an ionic conductivity by dissolving an electrolyte in a solvent. The type of the electrolytic solution E may be selected according to the type of metal constituting the metal electrode A, and may be an electrolytic solution using an aqueous solvent (electrolyte aqueous solution), or an electrolytic solution using an organic solvent (organic electrolytic solution) ).
For example, in the case of a zinc air battery, an aluminum air battery, or an iron air battery, an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used as the electrolyte. In the case of a magnesium air battery, a neutral aqueous solution such as a sodium chloride aqueous solution can be used as the electrolytic solution. In the case of a lithium metal battery, a sodium air battery, or a calcium air battery, an organic electrolyte can be used.

The metal electrode A is used as a negative electrode (anode) of the metal-air battery EC. Since the metal constituting the metal electrode is consumed with the progress of the battery reaction, the metal electrode A is preferably exchangeable. That is, it is preferable that the metal air battery casing is provided with a support portion to which the metal electrode A can be attached. The form of the support portion is not particularly limited. For example, the metal electrode A may be a part accommodated in the electrolyte bath by inserting the metal electrode A from above in the gravity direction, or may be inserted into the electrolyte bath. It may be a fastener for holding the upper end of the formed metal electrode A, or a combination thereof. The support member preferably functions as a current collector, and preferably electrically connects the metal electrode A and an external circuit.

The arrangement of the metal electrode A is not particularly limited as long as the electrolytic solution E held in the electrolytic solution tank and the metal electrode A have ionic conduction, and the metal electrode A and the electrolytic solution E may be in direct contact. A separator S may be disposed between A and the electrolytic solution E. Further, in a state where the metal electrode A is attached to the metal-air battery casing, the metal electrode A is placed in the electrolyte bath so that the electrode main surface is parallel to the direction of gravity, in other words, the electrode main surface is It is preferable that the electrodes are arranged so as to intersect the horizontal direction because the distance between the electrodes of the metal electrode A and the air electrode C becomes uniform and short, and the resistance between the electrodes can be suppressed.

In Embodiment 1, a zinc electrode is used as the metal electrode A, but a metal electrode other than the zinc electrode can be used as the negative electrode. Examples of the material constituting the metal electrode other than the zinc electrode include lithium (Li), sodium (Na), calcium (Ca), magnesium (Mg), aluminum (Al), iron (Fe), cobalt (Co), Examples thereof include metals such as cadmium (Cd) and palladium (Pd), and alloys thereof. The metal constituting the metal electrode emits electrons by the discharge reaction of the battery, dissolves in the electrolyte solution E, and then deposits as a metal compound such as a metal oxide or metal hydroxide.

The metal-air battery EC of the present invention may or may not include the separator S, but preferably includes the separator S. Further, when the metal-air battery EC of the present invention includes the separator S, the air electrode C and the separator S of the present invention may or may not be integrated, but the air electrode of the present invention may not be integrated. It is preferable that C and the separator S are integrated.
As the separator S, a hydrophilic porous membrane is preferable. The pore size of the porous membrane is preferably 10 μm or less at maximum. When the pore diameter exceeds 10 μm, the permeation of the negative electrode reaction product cannot be suppressed, and it is deposited on the positive electrode, which may reduce the long-term stability of the battery. Separator S includes kraft paper, vinylon / synthetic pulp paper, cellophane, polyethylene graft membrane, polyolefin nonwoven fabric, polyamide nonwoven fabric and other resin materials, glass fiber nonwoven fabric and other nonwoven materials, ceramic materials, zeolite, activated carbon, Ni, stainless steel, etc. Among these, those obtained by laminating these metals can be mentioned as preferred, among which nonwoven fabrics are more preferred, and polyolefin nonwoven fabrics are even more preferred.

The metal-air battery EC of Embodiment 1 may be a primary battery or a secondary battery.
The structure of what is generally used as a metal air battery can be used for the other structure of the metal air battery of Embodiment 1.

[Embodiment 2]
FIG. 4 is a schematic cross-sectional view illustrating the entire configuration of the air electrode according to the second embodiment of the present invention.
The air electrode C of the second embodiment is configured by an air electrode catalyst layer 115, an air electrode conductive layer 113, a diffusion layer 112, and a water absorption layer 111 arranged in this order from the electrolyte bath side to the air side.
The air electrode C of the second embodiment includes an air electrode catalyst layer 115, an air electrode conductive layer 113, a diffusion layer 112, and a water absorption layer 111, and includes an air electrode catalyst layer 115, an air electrode conductive layer 113, and a water absorption layer 111. A diffusion layer 112 is disposed therebetween.
The air electrode C is not limited to the one shown in FIG. 4, but preferably includes at least an air electrode catalyst layer, an air electrode conductive layer, a diffusion layer, and a water absorption layer, and more preferably integrated with the separator. preferable.
The air electrode conductive layer 113 used in Embodiment 2 is not particularly limited as long as it is a metal used as a current collector in a battery. For example, nickel is preferable. Further, the configuration of the air electrode conductive layer is not particularly limited, but the air electrode conductive layer is preferably in a mesh shape.
The air electrode catalyst layer 115 used in the second embodiment includes an electron conductive material 121, an electrode catalyst 117, and a fluororesin 119. The air electrode catalyst layer 115 preferably includes at least an electrode catalyst and a fluororesin, and more preferably includes an electron conductive substance. More preferably, the electrode catalyst is supported on an electron conductive material. The fluororesin is more preferably PTFE.
There are a plurality of voids 123 in the air electrode catalyst layer 115. Thus, the air electrode catalyst layer 115 is preferably porous.

In the metal-air battery including the air electrode of Embodiment 1 described above, the electrolyte does not leached from the entire air side surface of the air electrode conductive layer 13 of the air electrode, but the air side of the air electrode conductive layer 13 of the air electrode. The electrolyte is preferentially leached from the portion of the surface that has been leached once (the portion where the leaching path is opened), and is retained by the surrounding water-absorbing polymer. Therefore, in the first embodiment, there is a new problem that only the portion of the water absorbing layer (water absorbing polymer) from which the electrolyte solution preferentially leaches is used, and the entire water absorbing layer may not be used.

In the second embodiment, the electrolyte solution leached from the air electrode conductive layer 113 is retained in a wider range of water-absorbing polymer in the water-absorbing layer 111 by diffusing inside the diffusion layer 112.
The diffusion layer 112 is preferably composed of a hydrophilic porous membrane.
The hydrophilic porous membrane is not particularly limited as long as it is hydrophilic and can pass air, and it is preferable to use the same material as the separator. For example, kraft paper, vinylon / synthetic pulp paper, cellophane, polyethylene graft membrane, polyolefin Non-woven fabrics such as non-woven fabric, polyamide non-woven fabric, and glass fiber non-woven fabric, and the like, which are laminated, are mentioned as preferred. Among these, non-woven fabric is more preferred, and polyolefin non-woven fabric is more preferred.
The porous pore diameter is preferably 5 μm or less at maximum.
“Hydrophilic” means that the water adhering to the surface does not form water droplets, and the water contact angle in the hydrophilic porous layer may be 40 degrees or less.

(Effect of Embodiment 2)
In the metal-air battery including the air electrode according to the second embodiment, in addition to the effects of the first embodiment, the electrolyte solution leached by the diffusion layer 112 can be diffused in a wider range. Can be used without waste. Therefore, more leached electrolyte can be retained, and the life of the battery can be further extended.

(Procedure for producing an air electrode or the like of Embodiment 2)
An example of a procedure for producing an air electrode or the like according to the second embodiment will be described in detail below, but is not limited thereto, and can be appropriately changed as necessary.
(1) Preparation of the air electrode catalyst layer 115 The electrode catalyst 117, the electron conductive material 121, and the fluororesin 119 are mixed and stirred, and the resulting mixture is passed through a pressure roller to form a sheet-like air electrode catalyst layer 115. Get.
(2) Preparation of the water-absorbing layer 111 The electron conductive substance 121 and the water-absorbing polymer are mixed and stirred, and the resulting mixture is passed through a pressure roller to obtain the sheet-like water-absorbing layer 111.
(3) Production of the air electrode C The air electrode conductive layer 113 and the sheet-shaped air electrode catalyst layer 115 obtained in the above (1) and the sheet-like water absorption layer 111 obtained in the above (2) The diffusion layer 112 is pressure-bonded to form an integrated product to obtain the air electrode C.

Other configurations of the second embodiment are the same as those of the first embodiment described above.

[Embodiment 3]
FIG. 5 is a schematic cross-sectional view illustrating the entire configuration of the air electrode according to the third embodiment of the present invention. 6 is a schematic cross-sectional view showing a configuration of a diffusion layer used in the metal-air battery of Embodiment 3, and corresponds to a cross section taken along line A1-A2 in FIG.
The air electrode of Embodiment 3 is configured by arranging an air electrode catalyst layer 215, an air electrode conductive layer 213, a diffusion layer 212, and a water absorption layer 211 in this order from the electrolyte bath side to the air side.
The air electrode of Embodiment 3 includes an air electrode catalyst layer 215, an air electrode conductive layer 213, a diffusion layer 212, and a water absorption layer 211, and includes an air electrode catalyst layer 215, an air electrode conductive layer 213, and a water absorption layer 211. A diffusion layer 212 is disposed therebetween, and a hydrophobic portion 212 a is provided in part of the diffusion layer 212. The portion other than the hydrophobic portion 212a of the diffusion layer 212 is composed of a hydrophilic portion 212b. That is, the third embodiment has the same configuration as that of the second embodiment except that the diffusion layer 212 includes the hydrophobic portion 212a together with the hydrophilic portion 212b.
The air electrode C is not limited to the one shown in FIG. 5, but preferably includes at least an air electrode catalyst layer, an air electrode conductive layer, a diffusion layer having a hydrophilic portion and a hydrophobic portion, and a water absorption layer, and is integrated with a separator. More preferably.
The air electrode conductive layer 213 used in Embodiment 3 is not particularly limited as long as it is a metal used as a current collector in a battery. For example, nickel is preferable. Further, the configuration of the air electrode conductive layer is not particularly limited, but the air electrode conductive layer is preferably in a mesh shape.
The air electrode catalyst layer 215 used in Embodiment 3 is composed of an electron conductive material 221, an electrode catalyst 217, and a fluororesin 219. The air electrode catalyst layer preferably contains at least an electrode catalyst and a fluororesin, and more preferably contains an electron conductive substance. More preferably, the electrode catalyst is supported on an electron conductive material. The fluororesin is more preferably PTFE.
There are a plurality of voids 223 in the air electrode catalyst layer 215. Thus, the air electrode catalyst layer 215 is preferably porous.

In the metal-air battery including the air electrode of Embodiment 2 described above, the electrolyte solution diffuses over a wide range by the diffusion layer, and the electrolyte solution is held by more water-absorbing polymer. Therefore, in Embodiment 2, since the diffusion layer is filled with the electrolyte as time passes, there is a new problem that the oxygen diffusion path inside the diffusion layer may be blocked.

The electrolyte solution leached from the air electrode of the third embodiment is held in a wider range of water-absorbing polymer by diffusing outside the hydrophobic portion 212a in the diffusion layer 212. In addition, even when time elapses, the oxygen diffusion path in the diffusion layer 212 is secured by the hydrophobic portion 212 b in the diffusion layer 212.
The hydrophilic part 212b in the diffusion layer 212 used in Embodiment 3 is preferably made of the same material as the separator (for example, a hydrophilic porous film). That is, as the hydrophilic portion 212b in the diffusion layer 212, the diffusion layer 112 as described above can be used.
The hydrophobic portion 212a in the diffusion layer 212 is preferably composed of a hydrophobic porous membrane. The hydrophobic material constituting the hydrophobic porous membrane is preferably, for example, a fluororesin, and more preferably PTFE. The hydrophobic porous membrane may further contain carbon. Hydrophobicity may be any water that adheres to the surface in the form of water droplets.
The porous membrane only needs to be capable of passing air. The porous pore diameter is preferably 10 μm or less at maximum.
The position of the hydrophobic portion 212a is not limited to that shown in FIG. 6, and can be appropriately arranged.

(Effect of Embodiment 3)
In the metal-air battery including the air electrode according to the third embodiment, in addition to the effect of the second embodiment, the oxygen diffusion path in the diffusion layer 212 is secured by the hydrophobic portion 212a in the diffusion layer 212. (Long life) can be achieved. Moreover, since the metal air battery provided with the air electrode of Embodiment 3 has an oxygen diffusion path secured, it can generate power even when high output is required.

(Procedure for producing an air electrode or the like of Embodiment 3)
An example of a procedure for producing an air electrode or the like according to Embodiment 3 will be described in detail below, but is not limited thereto, and can be appropriately changed as necessary.
(1) Preparation of the air electrode catalyst layer 215 The electrode catalyst 217, the electron conductive material 221 and the fluororesin 219 are mixed and stirred, and the resulting mixture is passed through a pressure roller to form a sheet-like air electrode catalyst layer 215. Get.
(2) Preparation of the water-absorbing layer 211 The electron conductive substance 221 and the water-absorbing polymer are mixed and stirred, and the resulting mixture is passed through a pressure roller to obtain a sheet-like water-absorbing layer 211.
(3) Preparation of diffusion layer 212 The diffusion layer 212 (hydrophilic portion) is cut out like the hydrophilic portion 212b shown in FIG. The hydrophobic porous membrane is cut out to be slightly larger than the hydrophobic portion 212a in FIG. 6, and is stacked so as to have the configuration shown in FIG.
(4) Production of Air Electrode C The air electrode conductive layer 213 and the above described so as to be sandwiched between the sheet-like air catalyst layer 215 obtained in the above (1) and the sheet-like water absorbing layer 211 obtained in the above (2). The diffusion layer 212 obtained in (3) is pressure-bonded to form an integrated product to obtain the air electrode C.

Other configurations of the third embodiment are the same as those of the second embodiment described above.
In the air electrode C of the third embodiment, the hydrophobic portion 212a provided in a part of the diffusion layer 212 is not limited to the rectangular shape as shown in FIG. Further, in one hydrophobic portion 212a, the position of the end surface of the sheet-like diffusion layer 212 that is in contact with the air electrode catalyst layer 215 or the air electrode conductive layer 213 is in contact with the water absorption layer 211 of the sheet-like diffusion layer 212. It is preferable that the position be lower than the position of the end face, that is, be located on the ground surface side of a metal-air battery housing (not shown). According to such a configuration, the supply of oxygen to the air electrode C is not impaired, and the weight of the electrolyte E leached into the diffusion layer 212 is added to the air electrode catalyst layer 215 side. Can be suppressed.

[Embodiment 4]
FIG. 7 is a schematic cross-sectional view illustrating the entire configuration of the air electrode according to the fourth embodiment. FIG. 8 is a schematic cross-sectional view showing the configuration of the diffusion layer used in the metal-air battery of Embodiment 4, and corresponds to a cross section taken along line B1-B2 in FIG. FIG. 9 is a schematic cross-sectional view illustrating a configuration of a water absorption layer used in the metal-air battery of Embodiment 4, and corresponds to a cross section taken along line C1-C2 in FIG.
The air electrode of Embodiment 4 is configured by arranging an air electrode catalyst layer 315, an air electrode conductive layer 313, a diffusion layer 312 and a water absorption layer 311 in this order from the electrolyte bath side to the air side.
The air electrode of Embodiment 4 includes an air electrode catalyst layer 315, an air electrode conductive layer 313, a diffusion layer 312, and a water absorption layer 311, and includes the air electrode catalyst layer 315, the air electrode conductive layer 313, and the water absorption layer 311. A diffusion layer 312 is disposed therebetween, a hydrophobic portion 312 a is provided in a part of the diffusion layer 312, and a hydrophobic portion 311 a is also provided in the water absorption layer 311 at the same position as the hydrophobic portion 312 a of the diffusion layer 312. The same position as the hydrophobic portion 312a of the diffusion layer 312 means that it overlaps with the hydrophobic portion 312a of the diffusion layer 312 when the main surface of each layer of the air electrode C of the present invention is viewed in plan. In the fourth embodiment, the hydrophobic part of the water absorption layer and the hydrophobic part of the diffusion layer constitute an air flow path.
The portion of the diffusion layer 312 other than the hydrophobic portion 312a is composed of a hydrophilic portion 312b, and the portion of the water absorbing layer 311 other than the hydrophobic portion 311a is composed of a water absorbing portion 311c. That is, the fourth embodiment has the same configuration as that of the third embodiment except that the water absorption layer 311 has the hydrophobic portion 311a at the same position as the hydrophobic portion 312a of the diffusion layer 312 together with the water absorption portion 311c.
The air electrode C is not limited to the one shown in FIG. 7, but includes at least an air electrode catalyst layer, an air electrode conductive layer, a diffusion layer having a hydrophobic portion together with a hydrophilic portion, and a water absorbing layer having a hydrophobic portion together with a water absorbing portion. It is preferable that it is integrated with the separator.
The air electrode conductive layer 313 used in Embodiment 4 is not particularly limited as long as it is a metal used as a current collector in a battery. For example, nickel is preferable. Further, the configuration of the air electrode conductive layer is not particularly limited, but the air electrode conductive layer is preferably in a mesh shape.
The air electrode catalyst layer 315 used in the fourth embodiment includes an electron conductive material 321, an electrode catalyst 317, and a fluororesin 319. The air electrode catalyst layer preferably contains at least an electrode catalyst and a fluororesin, and more preferably contains an electron conductive substance. More preferably, the electrode catalyst is supported on an electron conductive material. The fluororesin is more preferably PTFE.
There are a plurality of voids 323 in the air electrode catalyst layer 315. Thus, the air electrode catalyst layer 315 is preferably porous.

The hydrophobic part 312a in the diffusion layer 312 used in the fourth embodiment is usually composed of a hydrophobic porous film. As the hydrophobic porous membrane, a material similar to the hydrophobic portion 212a in the diffusion layer 212 used in Embodiment 3 can be suitably used. The position of the hydrophobic portion 312a is not limited to that shown in FIG. 8, and can be appropriately arranged.
It is preferable that the hydrophobic part 311a in the water absorption layer 311 used in Embodiment 4 is composed of a hydrophobic porous film. As the hydrophobic porous membrane in the water absorbing layer, the same hydrophobic portion as that in the diffusion layer can be used, but it is more preferably composed of a fluororesin and carbon. The position of the hydrophobic portion 311a is not limited to that shown in FIG. 8 as long as it overlaps with the hydrophobic portion 312a, and can be appropriately arranged.

In the metal-air battery including the air electrode of Embodiment 3 described above, the electrolyte solution diffuses over a wide range by the diffusion layer 212 and is held in more water-absorbing polymer, and oxygen is absorbed by the hydrophobic portion 212a in the diffusion layer 212. A diffusion path is secured. Therefore, in the third embodiment, the oxygen diffusion path in the diffusion layer 212 is secured even when time passes, but the oxygen diffusion path in the water absorption layer 211 is blocked by the water-absorbing polymer absorbed as time passes. There was a new problem that there is a risk of being lost.

The electrolyte solution leached from the air electrode according to the fourth embodiment is retained in a wider range of water-absorbing polymer by diffusing outside the hydrophobic portion 312 a in the diffusion layer 312. Further, even when time elapses, the oxygen diffusion path in the diffusion layer 312 is secured by the hydrophobic portion 312a in the diffusion layer 312, and the oxygen diffusion path in the water absorption layer 311 is secured by the hydrophobic portion 311a in the water absorption layer 311. The

(Effect of Embodiment 4)
In the metal-air battery including the air electrode according to the fourth embodiment, an oxygen diffusion path from the outside of the air electrode to the air electrode catalyst layer is ensured, so that power generation (life extension) can be performed for a longer period. Moreover, since the metal air battery provided with the air electrode of Embodiment 4 has an oxygen diffusion path secured, it can generate power even when high output is required.

(Procedure for producing an air electrode or the like of Embodiment 4)
An example of a procedure for producing an air electrode or the like according to Embodiment 4 will be described in detail below, but is not limited to this, and can be changed as appropriate.
(1) Preparation of the air electrode catalyst layer 315 The electrode catalyst 317, the electron conductive material 321 and the fluororesin 319 are mixed and stirred, and the resulting mixture is passed through a pressure roller to form a sheet-like air electrode catalyst layer 315. Get.
(2) Preparation of water absorption layer 311 The electron conductive material 321 and the water absorbing polymer are mixed and stirred, and the resulting mixture is passed through a pressure roller to obtain a water absorbing portion sheet. The water absorption part 311c shown in FIG. 9 was obtained by punching with a mold.
The electron conductive substance 321 and the fluororesin 319 are mixed and stirred, and the obtained mixture is passed through a rolling roller to obtain a hydrophobic part sheet. A water-absorbing layer 311 is obtained by punching in a strip shape with a mold and passing the rolling unit roller over the hydrophobic part sheet and the water-absorbing part sheet so that the hydrophobic part sheet covers the punched part of the water-absorbing part sheet.
(3) Preparation of diffusion layer 312 The diffusion layer (hydrophilic portion) 312 is cut out like the hydrophilic portion 312b shown in FIG. The hydrophobic porous membrane is cut out to be slightly larger than the hydrophobic portion 312a in FIG. 8 and stacked so as to have the configuration shown in FIG.
(4) Production of air electrode C The air electrode conductive layer 313 and the sheet-like air electrode catalyst layer 315 obtained in the above (1) and the sheet-like water absorption layer 311 obtained in the above (2) The diffusion layer 312 obtained in the above (3) is pressure-bonded to form an integrated product to obtain the air electrode C.
Did.

Other configurations of the fourth embodiment are the same as those of the third embodiment described above.
In the air electrode C of the fourth embodiment, the hydrophobic portions 311a and 312a provided in part of the water absorption layer 311 or the diffusion layer 312 are not limited to the rectangular shape as shown in FIG. Further, in one hydrophobic portion 311a, the position of the end face in contact with the diffusion layer 312 is set lower than the position of the end face in contact with the atmosphere, that is, located on the ground plane side of the metal battery housing (not shown). It is preferable to keep it. Similarly, in one hydrophobic portion 312a, the end surface in contact with the air electrode catalyst layer 315 or the air electrode conductive layer 313 is set lower than the position of the end surface in contact with the water absorption layer 311. It is preferable to be located on the grounding surface side of the metal battery housing that does not. According to such a configuration, the supply of oxygen to the air electrode C is not impaired, and the own weight of the electrolyte E leached into the water absorption layer 311 or the diffusion layer 312 is added to the air electrode catalyst layer 315 side. The leaching rate of the liquid E can be suppressed.

[Embodiment 5]
FIG. 10 is a schematic cross-sectional view illustrating the entire configuration of the air electrode according to the fifth embodiment.
The air electrode according to the fifth embodiment includes an air electrode catalyst layer 415, an air electrode conductive layer 413, a water absorbing layer 411, and a water repellent layer 410 arranged in this order from the electrolyte bath side to the air side. Yes.
The air electrode of Embodiment 5 includes an air electrode catalyst layer 415, an air electrode conductive layer 413, a water absorbing layer 411, and a water repellent layer 410, and the air side (electrolyte solution) of the air electrode catalyst layer 415 and the air electrode conductive layer 413. A water-absorbing layer 411 containing a water-absorbing polymer is provided on the side opposite to the tank side, and a water-repellent layer 410 is further provided on the air side of the water-absorbing layer 411.
The air electrode of Embodiment 5 is the same as the structure of the air electrode of Embodiment 1 except that a water repellent layer is provided outside the water absorbing layer.
The air electrode C is not limited to the one shown in FIG. 10, but preferably includes at least an air electrode catalyst layer, an air electrode conductive layer, a water absorbing layer, and a water repellent layer, and is integrated with a separator. More preferred.
The air electrode conductive layer 413 used in Embodiment 5 is not particularly limited as long as it is a metal used as a current collector in a battery. For example, nickel is preferable. Further, the configuration of the air electrode conductive layer is not particularly limited, but the air electrode conductive layer is preferably in a mesh shape.
The air electrode catalyst layer 415 used in the fifth embodiment includes an electron conductive material 421, an electrode catalyst 417, and a fluororesin 419. The air electrode catalyst layer preferably contains at least an electrode catalyst and a fluororesin, and more preferably contains an electron conductive substance. More preferably, the electrode catalyst is supported on an electron conductive material. The fluororesin is more preferably PTFE.
There are a plurality of voids 423 in the air electrode catalyst layer 415. Thus, the air electrode catalyst layer 415 is preferably porous.

In the metal-air battery including the air electrodes of Embodiments 1 to 4 described above, the electrolytic solution is held in the water-absorbing polymer inside the water-absorbing layer as time passes. When the outermost water-absorbing polymer finally holds the electrolytic solution, there is a new problem that a battery user may come into contact with the electrolytic solution.

The water-repellent layer 410 used in the fifth embodiment prevents battery users from coming into contact with the electrolytic solution and prevents moisture outside the battery from being absorbed by the water-absorbing polymer in the water-absorbing layer.
The water repellent layer 410 used in the fifth embodiment may be composed of a fluororesin and carbon, or may be composed of a fluororesin porous film. In addition, you may use what mixed the fluororesin and carbon instead of PTFE as a hydrophobic part of a diffused layer.

(Effect of Embodiment 5)
In the metal-air battery including the air electrode of the fifth embodiment, in addition to the effects of the first embodiment, the possibility that a battery user or the like contacts the electrolyte can be further reduced, and the battery can be handled safely. Further, by providing the water repellent layer, it is possible to prevent moisture outside the battery from being absorbed by the water absorbing polymer of the water absorbing layer. In order to prevent moisture outside the battery from being absorbed, the battery characteristics can be maintained even in a humid environment.

(Procedure for producing an air electrode or the like of Embodiment 5)
(1) Production of Air Electrode Catalyst Layer 415 Electrocatalyst 417, electron conductive material 421, and fluororesin 419 are mixed and stirred, and the resulting mixture is passed through a pressure roller to form a sheet-like air electrode catalyst layer 415. Get.
(2) Preparation of water-absorbing layer 411 The electron conductive substance 421 and the water-absorbing polymer are mixed and stirred, and the resulting mixture is passed through a pressure-rolling roller to obtain a thick sheet-like water-absorbing layer 411.
(3) Preparation of water-repellent layer 410 The electron conductive substance 421 and the fluororesin 419 are mixed and stirred, and the resulting mixture is passed through a pressure roller to obtain a sheet-like water-repellent layer 410.
(4) Production of integrated product of water-absorbing layer 411 and water-repellent layer 410 The sheet-like water-absorbing layer 411 obtained in (2) above and the sheet-like water-repellent layer 410 obtained in (3) above are pressure-bonded. Integrated.
(5) Production of air electrode C The air electrode conductive layer 413 is pressed and integrated so as to be sandwiched between the sheet-like air electrode catalyst layer 415 obtained in (1) above and the integrated product obtained in (4) above. The cathode is molded to obtain the air electrode C. (Press bonding is performed so that the water absorption layer 411 and the air electrode conductive layer 413 are in contact with each other.)

Other configurations of the fifth embodiment are the same as the configurations of the first embodiment described above.

Each structure of embodiment mentioned above can be combined suitably. For example, the water repellent layer 410 used in the fifth embodiment can be used in the air electrode C of the second to fourth embodiments.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
Example 1
(Procedure for manufacturing the air electrode C and the like of the first embodiment)
(1) Preparation of air electrode catalyst layer Electrocatalyst, electron conductive substance, and fluororesin are mixed and stirred, and the resulting mixture is passed through a rolling roller to obtain a sheet having a thickness of 1 mm. It was.
Specifically, platinum 50 wt% supported carbon (electrode catalyst, manufactured by Tanaka Kikinzoku Co., Ltd., TEC10E50E) 0.1 g, carbon black (manufactured by Electroconductive Substance Cabot Co., Ltd., VULCAN XC72-R) 1.5 g, and polytetrafluoro 0.7 g of ethylene (PTFE) (manufactured by Aldrich) was kneaded in a mortar to obtain a mixture. The obtained mixture was passed through a rolling roller to form a sheet having a thickness of 1 mm.
(2) Preparation of water-absorbing layer The electron conductive substance and the water-absorbing polymer were mixed and stirred, and the resulting mixture was passed through a pressure-rolling roller to obtain a sheet having a thickness of 0.5 mm, which was used as the water-absorbing layer.
Specifically, 1.0 g of carbon black (electroconductive material, manufactured by Cabot, VULCAN XC72-R) and 0.1 g of crosslinked potassium polyacrylate (water-absorbing polymer, manufactured by Aldrich) were kneaded in a mortar. A mixture was obtained. The obtained mixture was passed through a rolling roller to form a sheet having a thickness of 0.5 mm.
(3) Preparation of air electrode C Press the air electrode conductive layer (nickel mesh, wire diameter 0.15 mm, 40 mesh) so as to be sandwiched between the sheet obtained in (1) and the sheet obtained in (2). An integrated product was formed by pressure bonding at 5 kN for 5 minutes using a machine, and the air electrode C of Example 1 was obtained.
(4) Integration of air electrode C and separator S The separator (air electrode of Example 1) obtained by (3) is pressed with a separator at 2 kN for 5 minutes to be integrated with the separator (polyolefin nonwoven fabric). Formed air electrode.

(Comparative Example 1)
The metal-air battery of Comparative Example 1 is the same as Example 1 except that the water absorption layer is not provided.

(Comparative Example 2)
The metal-air battery of Comparative Example 2 is the same as that of Embodiment 1 except that a layer (water repellent layer) made only of carbon black (manufactured by Cabot, VULCAN XC72-R) is provided instead of the water absorbing layer.

[Evaluation method]
(1) 300 ml of electrolytic solution (7 mol / dm ³ , KOH) is injected into an electrolytic bath provided with the air electrode manufactured in the examples and comparative examples on the leakage wall of the electrolytic solution, and the environment at room temperature (25 ° C.) Let stand under. Thereafter, the electrolyte solution was leached from the air electrode of the example and the comparative example, and it was visually observed whether or not the outer wall of the electrolyte bath was wetted with the electrolyte solution.
The area of the air electrode in contact with the atmosphere and the electrolyte was 50 mm × 50 mm. The depth of the inner wall of the electrolytic solution tank was 80 mm, and the material of the electrolytic solution tank other than the air electrode portion was made of ABS.

(2) 300 ml of electrolyte solution (7 mol / dm ³ , KOH) was injected into an electrolyte bath provided with the air electrode manufactured in the examples and comparative examples on the long-term reliability wall.
The zinc electrode was formed by pressing a support made of SUS304 (70 mm × 50 mm, thickness 1 mm) with a mixture of zinc powder and PTFE dispersion as a binder, and pressing. The formed zinc electrode was unified to 50 mm × 50 mm and a thickness of 20 mm.
A discharge experiment was conducted in which a zinc electrode was inserted into the electrolyte bath and the zinc-air battery was discharged at a constant current load of 1.5 A (current density 30 mA / cm 2) at room temperature (25 ° C.) for 5 hours per day. The zinc electrode used for one day was not repeatedly used, and an experiment was conducted using a new zinc electrode. In the measurement of the discharge voltage, Fuel Cell Test System (manufactured by Toyo Technica Co., Ltd., model number 890CL) was used.

[result]
Table 1 shows the evaluation results using the air electrodes of Example 1, Comparative Example 1 and Comparative Example 2. The leaching in Table 1 indicates the period from the start of the leaching evaluation of the electrolytic solution until the leaching of the electrolytic solution is visually confirmed. The long-term reliability is a discharge at a stable voltage (constant voltage). Indicates the completed period.

In the air electrode of Example 1, no leaching of the electrolytic solution could be confirmed even after one year from the start of the experiment. On the other hand, each of the air batteries of Comparative Example 1 and Comparative Example 2 is confirmed to be leached out of the electrolyte solution in about one month, prevents leakage of the electrolyte solution over a longer period, and is excellent in reliability and safety. It became clear.
Moreover, when the air electrode of Example 1 was used, it was possible to discharge at a constant voltage for one year or more.

[Appendix]
From the above embodiments, the following aspects of the present invention are derived.
One embodiment of the present invention is an air electrode used for a positive electrode of a metal-air battery, and the air electrode includes a catalyst layer 15, a conductive layer 13, and a water absorption layer 11, and the water absorption layer 11 includes a water absorption layer. It may be an air electrode that has a water absorbing part containing a polymer and is provided on one side with respect to the catalyst layer 15 and the conductive layer 13. The water absorption layer 11 may be composed of only the water absorption part.

In the metal-air battery including the air electrode of the above aspect, the water-absorbing polymer provided in the water-absorbing layer 11 can retain (gel) the electrolyte solution and prevent the electrolyte solution from leaking outside the air electrode. In the metal-air battery, since the electrolytic solution does not leak to the outside, adverse effects on the environment can be eliminated, and the risk of battery users and the like directly touching the electrolytic solution is reduced. In the metal-air battery, since the ion conduction inside the battery is not rate-limiting, a high output can be obtained.

In the above aspect, the air electrode further includes a diffusion layer 112, and the diffusion layer 112 has a hydrophilic portion composed of a hydrophilic porous membrane, and is between the catalyst layer and the conductive layer and the water absorption layer. May be provided. The diffusion layer 112 may be composed only of a hydrophilic portion. With such a configuration, the electrolyte solution leached out by the diffusion layer 112 can be diffused in a wider range, so that the water-absorbing polymer inside the water-absorbing layer can be used without waste. Therefore, more leached electrolyte can be retained, and the life of the battery can be further extended.

In the above aspect, the diffusion layer may further include a hydrophobic portion 212a composed of a hydrophobic porous membrane. With such a configuration, since the oxygen diffusion path in the diffusion layer 212 is secured by the hydrophobic portion 212a in the diffusion layer, power generation (long life) can be performed for a longer period. In addition, since the metal-air battery has an oxygen diffusion path, it can generate power even when high output is required.

In the above aspect, the water absorbing layer further includes a hydrophobic portion 311a composed of a hydrophobic porous membrane. It may overlap with the hydrophobic part of the diffusion layer. With such a configuration, even when time elapses, the oxygen diffusion path in the water absorption layer 311 is also secured by the hydrophobic portion 311a in the water absorption layer.

In the above aspect, the air electrode may further include a water-repellent layer 410, and the water-repellent layer 410 may be disposed on the opposite side of the water-absorbing layer to the catalyst layer and the conductive layer side. With such a configuration, it is possible to further reduce the possibility of battery users and the like coming into contact with the electrolytic solution and handle the battery safely. Further, by providing the water repellent layer, it is possible to prevent moisture outside the battery from being absorbed by the water absorbing polymer of the water absorbing layer. In order to prevent moisture outside the battery from being absorbed, the battery characteristics can be maintained even in a humid environment.

In the above aspect, the water-absorbing polymer may be a crosslinked polyacrylate. By setting it as such a structure, the effect which can prevent the leakage of electrolyte solution for a long term can be made more remarkable.

In the above embodiment, the water repellent layer 410 may contain a fluororesin. By setting it as such a structure, possibility that the user of a battery etc. will contact electrolyte solution is further reduced, and a battery can be handled safely. In addition, it is possible to further prevent moisture outside the battery from being absorbed by the water-absorbing polymer in the water-absorbing layer. Therefore, the battery characteristics can be further maintained even in a humid environment.

Another aspect of the present invention is a metal-air battery EC including the air electrode C, the electrolytic solution E, and the metal electrode A, wherein the water absorption layer of the air electrode C is outside the catalyst layer and the conductive layer. May be arranged. The metal-air battery of the present invention can prevent the water-absorbing polymer provided in the water-absorbing layer from holding (gelling) the electrolytic solution, and preventing the electrolytic solution from leaking outside the air electrode. In the metal-air battery, since the electrolytic solution does not leak to the outside, adverse effects on the environment can be eliminated, and the risk of battery users and the like directly touching the electrolytic solution is reduced. In the metal-air battery, since the ion conduction inside the battery is not rate-limiting, a high output can be obtained.

EC: Metal-air battery A: Metal electrode C: Air electrode E: Electrolyte S: Separator H: Hole I: Injection port 11, 111, 211, 311, 411: Water absorption layer 13, 113, 213, 313, 413 513: Air electrode conductive layer 15, 115, 215, 315, 415, 515: Air electrode catalyst layer 17, 117, 217, 317, 417, 517: Electrode catalyst 19, 119, 219, 319, 419, 519: Fluorine Resins 21, 121, 221, 321, 421: electron conductive materials 23, 123, 223, 323, 423: voids 112, 212, 312: diffusion layers 212 a, 311 a, 312 a: hydrophobic portions 212 b, 312 b: hydrophilic portions 311 c: Water absorption part 410: water repellent layer

Claims (4)

A metal electrode;
An air electrode disposed to face the metal electrode;
A water-absorbing layer provided outside the air electrode and containing a water-absorbing polymer;
A metal-air battery comprising a water-repellent layer provided outside the water-absorbing layer. The air electrode is
A conductive layer;
The metal-air battery according to claim 1, comprising a catalyst layer in contact with the conductive layer and including an electrode catalyst. The metal-air battery according to claim 2, wherein the catalyst layer further includes a first electron conductive material. The metal-air battery according to claim 1, wherein the water absorption layer further contains a second electron conductive material.

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