JP6583138B2 - Metal air battery - Google Patents

Description

  The present invention relates to a metal-air battery.

  The metal-air battery uses, for example, metal Li (lithium) as a negative electrode active material and oxygen in the atmosphere as a positive electrode active material. Metal-air batteries have a high energy density. In particular, lithium-air batteries are expected as batteries capable of obtaining an energy density of 700 Wh / kg, which is necessary for the spread of full-scale electric vehicles (EVs). This energy density is seven times higher than lithium-ion batteries that are currently being installed in vehicles.

  Lithium-air batteries use metal lithium or an alloy or compound containing metal lithium as a main component for the negative electrode active material. Lithium-air batteries are being actively researched because of their high energy density.

 Here, lithium-air batteries are roughly classified into two types, an aqueous solution type and a non-aqueous solution type (non-aqueous type), depending on the type of the electrolyte. In general, an aqueous lithium battery has a structure including a positive electrode made of a current collector carrying a catalyst, an aqueous electrolyte, an isolation layer (solid electrolyte), and a negative electrode.

  Here, in the aqueous lithium battery, if the water content of the aqueous electrolyte is volatilized and reduced, the function as the aqueous electrolyte may be hindered and it may be difficult to perform stable discharge and charge.

  As a countermeasure, conventionally, as disclosed in Patent Document 1, as a method for preventing volatilization of an aqueous electrolyte, an alkali metal hydroxide aqueous solution (electrolyte) of an air zinc battery is added to polyhydroxy 2-methacrylic acid, One or two or more vinyl compounds selected from polymethacrylic acid-ethylene glycol copolymer, dimethylaminopropyl acrylamide and polyethylene oxide derivative-3 functional acrylate, and a crosslinking agent as necessary are polymerized to polymerize. There is a technique that can prevent the volatilization of the electrolytic solution over a long period of time and maintain the discharge characteristics by using a gel body produced by adding zinc powder before or after.

  However, when this technology is applied to a lithium-air battery, there is a problem that the gel body deteriorates due to the basicity of the electrolyte in the gel body accompanying a long-term discharge, and volatilization cannot be prevented.

  Further, as disclosed in Patent Document 2, as a method for preventing volatilization of an aqueous electrolyte, an aqueous solution is provided by providing a water tank for supplying water to the volatilizing aqueous electrolyte and a humidifier for suppressing volatilization. There is a technology for making a metal-air battery system that can efficiently cope with the volatilization of moisture in the system electrolyte.

  However, when this technique is used, the volatilization of the aqueous electrolyte solution can be prevented, but there is a problem that it is difficult to ensure a high energy density because the weight increases due to the introduction of a water tank or a humidifier.

  Furthermore, as described in Patent Document 3, as a method for preventing volatilization of an aqueous electrolyte, a strongly acidic aqueous electrolyte having a boiling point higher than that of a general alkaline or weakly acidic aqueous electrolyte is used. There is a technique for suppressing volatilization of an aqueous electrolyte.

However, if this technique is used, the aqueous electrolyte solution becomes acidic and discharge is advantageous, but charging is disadvantageous and there is a problem in using it as a secondary battery.
In the aqueous lithium-air battery, it is necessary to protect the metallic lithium of the negative electrode with a solid electrolyte that is an isolation layer. The technique of Patent Document 3 has a problem that the solid electrolyte deteriorates with a strong acid.

JP 2002-343450 A JP 2012-204300 A JP2013-012385A

  In view of the above circumstances, an object of the present invention is to provide a metal-air battery capable of suppressing the volatilization of an electrolytic solution and performing stable discharge and charge.

  In order to achieve the above object, a metal-air battery according to the present invention is a metal-air battery including a positive electrode, an electrolytic solution, a solid electrolyte, and a negative electrode, wherein the electrolytic solution contains an organic solvent in an aqueous electrolyte solution. The hardly volatile aqueous electrolyte solution comprises 60% by mass to 80% by mass of the organic solvent.

  In the metal-air battery according to the present invention, the organic solvent preferably has a vapor pressure of less than 3000 Pa, preferably less than 500 Pa, at 25 ° C. and lower than the vapor pressure of water. .

  In the metal-air battery according to the present invention, it is preferable that the organic solvent is hygroscopic.

  In another embodiment of the metal-air battery according to the present invention, the organic solvent is NMP (N-methyl-2-pyrrolidone), DMSO (dimethyl sulfoxide), DMF (N, N-dimethylformamide), and their It is selected from the group consisting of two or more mixed solvents.

  In another embodiment, the metal-air battery according to the present invention uses metal lithium or an alloy or compound containing metal lithium as a main component as a negative electrode active material used for the negative electrode.

  In another embodiment, the metal-air battery according to the present invention comprises a negative electrode current collector, a negative electrode layer composed of a negative electrode active material, a buffer layer, and a laminate (laminate) of a solid electrolyte. And a negative electrode composite sandwiched between the lower exterior body, and among the layers constituting the upper exterior body, the layer that comes into contact with the hardly volatile aqueous electrolyte solution is composed of a polyolefin resin such as a polypropylene resin. ing.

  In another embodiment of the metal-air battery according to the present invention, among the layers constituting the upper exterior body, the layer to be joined to the solid electrolyte is composed of a polyolefin resin such as polypropylene resin.

  In another embodiment, the metal-air battery according to the present invention has a core layer of a laminated body constituting the upper exterior body made of a metal foil.

  In another embodiment of the metal-air battery according to the present invention, opposing layers of the upper exterior body and the lower exterior body are made of a polyolefin-based resin such as a polypropylene resin.

  ADVANTAGE OF THE INVENTION According to this invention, the volatilization of electrolyte solution is suppressed and the metal air battery which enabled it to perform the stable discharge and charge is provided.

It is typical sectional drawing explaining the basic concept of the metal air battery to which this invention is applied. (A) is a conceptual diagram explaining the action mechanism of the conventional aqueous solution type electrolyte solution, (b) is a conceptual diagram explaining the action mechanism of the hardly volatile aqueous solution type electrolyte solution which concerns on this invention. It is sectional drawing explaining one embodiment about the negative electrode composite_body | complex of the metal air battery which can be employ | adopted for this invention. It is sectional drawing explaining other embodiment about the negative electrode composite_body | complex of the metal air battery which can be employ | adopted for this invention. It is sectional drawing explaining one Embodiment of the metal air battery which concerns on this invention. It is a graph which shows the result of having performed the volatility test about the electrolyte solution employ | adopted by this invention, and the conventional electrolyte solution. It is a graph which compares and shows the performance regarding the charge / discharge of the lithium air battery by this invention, and the conventional lithium air battery.

  Embodiments of a metal-air battery according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 schematically shows a metal-air battery to which the present invention is applied. Here, an aqueous lithium-air battery 1 is schematically shown.
As shown in the drawing, the aqueous lithium-air battery 1 includes a positive electrode (air electrode) 2, an aqueous electrolyte 3, a solid electrolyte (separating layer) 4, and a negative electrode 5 each made of a current collector carrying a catalyst. The buffer layer (protective layer) 6 is also referred to as a separator, and is a layer for preventing the solid electrolyte 4 and the negative electrode from coming into direct contact. Note that the load 7 is schematically shown.

This aqueous lithium-air battery 1 is configured such that the following reactions occur at the negative electrode 5 and the positive electrode 2 respectively.
Negative electrode: Li → Li ⁺ + e ⁻
Positive electrode: O ₂ + 4e ⁻ + 2H ₂ O → 4OH ⁻
4Li + O ₂ + 6H ₂ O⇔4LiOH · H ₂ O

  An aqueous solution in which a salt such as lithium chloride is dissolved in water is used as the electrolytic solution of the aqueous lithium-air battery 1, and it volatilizes little by little even at room temperature. That is, here, as shown in FIG. 2 (a), the aqueous electrolyte solution 3 between the negative electrode composite 5 and the positive electrode 2 passes through the positive electrode 2 unless measures are taken. Will volatilize 8 and go. For this reason, when the aqueous lithium-air battery 1 is used for a long period of time, the discharge voltage and the charge performance may decrease, for example, the discharge voltage gradually decreases and the charge voltage increases.

  On the other hand, in the present invention, as shown in FIG. 2 (b), by taking a countermeasure, the electrolyte solution 3a is suppressed 9 from passing through the positive electrode 2 and volatilized.

  Specifically, the non-volatile aqueous electrolyte solution 3a obtained by mixing an aqueous electrolyte solution with a water-soluble, hygroscopic organic solvent having a low vapor pressure is used as the electrolyte solution.

In order to prepare such a hardly volatile aqueous electrolyte solution 3a, an aqueous lithium chloride solution is most commonly used as an aqueous electrolyte solution used in an aqueous lithium battery. However, as the aqueous electrolyte solution, it is only necessary to have electrical conductivity. In short, an aqueous electrolyte in which a lithium salt is dissolved in water is preferable. Examples of the lithium salt dissolved in water include LiCl (lithium chloride), LiOH (lithium hydroxide), LiNO ₃ (lithium nitrate), and CH ₃ COOLi (lithium acetate). An aqueous solution obtained by mixing two or more of these salt aqueous solutions may be used, and is not particularly limited.

  In addition, it should be understood that the present invention can be applied not only to lithium-air batteries as long as it is an air battery that uses an electrolytic solution. The electrolyte solution can be used as appropriate for the preparation of the hardly volatile aqueous electrolyte solution 3a.

  In the present invention, the organic solvent blended in the aqueous electrolyte may be any organic solvent that is water-soluble, hygroscopic, and has a low vapor pressure, and is limited to those using a specific organic solvent. Not. The vapor pressure of the organic solvent is preferably less than about 3000 Pa, more preferably less than 500 Pa, which is lower than the vapor pressure of water at 25 ° C. For example, NMP (N-methyl-2-pyrrolidone), DMSO (dimethyl sulfoxide), DMF (N, N-dimethylformamide) and the like can be mentioned. Two or more of these can also be used.

  The blending ratio of the organic solvent is preferably in the range of 60 to 80% by mass in the total amount of the hardly volatile aqueous electrolyte solution to be prepared. If it is this range, the volatilization of a water | moisture content can be suppressed and the function as electrolyte solution can be fulfilled.

  In the metal-air battery according to the present invention, a negative electrode composite and an air electrode including a positive electrode layer containing a conductive material are opposed to each other, and a hardly volatile aqueous electrolyte solution is placed between the negative electrode composite and the positive electrode layer. The solid electrolyte (separation layer) of the negative electrode composite and the air electrode layer of the air electrode can be configured to be in contact with the hardly volatile aqueous electrolyte solution.

  Hereinafter, an embodiment of a negative electrode composite that can be employed for a metal-air battery according to the present invention will be described with reference to FIGS. 3 and 4 by taking an aqueous lithium battery as an example.

  FIG. 3 shows an embodiment of a negative electrode composite for a metal-air battery that can be employed in the present invention. The embodiment shown in FIG. 3 is a form in which a solid electrolyte is provided only on one surface of a negative electrode composite to be produced. Hereinafter, the “negative electrode composite of a metal-air battery” is also simply referred to as “negative electrode composite”. FIG. 3 is a cross-sectional view of the negative electrode composite 31 according to the present embodiment. As a general form, the negative electrode composite 31 is configured to extend in a flat plate shape in a direction perpendicular to the paper surface, as in the conventionally known one.

  In the following description, elements located in the upward direction in the drawing are expressed as “upper side” or the like. However, this is merely for convenience of explanation, and what has been described as the upper side may be the lower side depending on the state in which the metal-air battery is arranged. Moreover, it may be located not in a vertical relationship but in a horizontal relationship.

  In the present embodiment, the negative electrode composite 31 is formed by laminating a negative electrode current collector 32, a negative electrode layer (metallic lithium negative electrode) 33 composed of a negative electrode active material, a buffer layer 34, and a solid electrolyte (separating layer) 35. To prepare. The negative electrode composite 31 is configured such that an opening of an upper exterior body 36 described later is positioned on the upper surface of the solid electrolyte 35.

  The negative electrode current collector 32 has a linear shape or a plate shape. The material of the negative electrode current collector 32 may be present stably in the operating range of a metal (lithium) air battery, and may have any desired conductivity. Examples thereof include copper and nickel.

The negative electrode active material of the negative electrode layer 33 is not particularly limited as long as it is a material capable of occluding and releasing metal ions. In this embodiment, it is metallic lithium capable of releasing lithium ions.
In addition to lithium, as the negative electrode active material, for example, metals such as sodium, calcium, magnesium, aluminum, zinc, and lithium can be used. Among these, an open circuit voltage is high and lithium is preferable from a practical viewpoint.

  Furthermore, the negative electrode active material is not limited to metallic lithium, and may be an alloy or compound containing lithium as a main component. The lithium-based alloy can include magnesium, calcium, aluminum, silicon, germanium, tin, lead, antimony, bismuth, silver, gold, zinc, and the like.

The solid electrolyte 35 is located on the surface where the negative electrode composite 31 is in contact with the hardly volatile aqueous electrolyte solution, and protects the negative electrode layer 33 from moisture.
Although the material of the solid electrolyte 35 will not be specifically limited if it has water resistance and metal ion conductivity, For example, a nonflammable solid electrolyte like glass ceramics can be used.

When metallic lithium is used as the negative electrode active material, the lithium ion conductivity of the solid electrolyte 35 is desirably 10 ⁻⁵ S / cm or more. As a material of such a solid electrolyte 35, for example, a glass ceramic having excellent lithium ion conductivity and nonflammability can be used. In particular, when an aqueous electrolytic solution is used as the electrolytic solution, an LTAP glass ceramic electrolyte having high water resistance can be used. LTAP is an oxide made of Li, Ti, Al, P, Si, O or the like having a NASICON type crystal structure.

  The buffer layer 34 is for preventing contact between the negative electrode layer 33 and the solid electrolyte 35. When the negative electrode layer 33 and the solid electrolyte 35 come into contact with each other, the negative electrode active material such as lithium in the negative electrode layer 33 and the glass ceramics in the solid electrolyte 35 may react to deteriorate the solid electrolyte 35. For this reason, the buffer layer 34 is for preventing contact between the negative electrode layer 33 and the solid electrolyte 35.

The buffer layer 34 is a metal ion conductive polymer electrolyte or organic electrolyte. For example, you may use what made the organic electrolyte solution immerse in a separator (sheets, such as porous polyethylene, polypropylene, and cellulose). When metallic lithium is used as the negative electrode active material, it is desirable that the lithium ion conductivity (also referred to as lithium ion conductivity) of the buffer layer 34 is 10 ⁻⁵ S / cm or more. The organic electrolyte used is, for example, one obtained by mixing diethyl carbonate or dimethyl carbonate with ethylene carbonate, which is a carbonate-based organic electrolyte, and further adding a lithium salt. For organic electrolytes other than those described above, ether electrolytes such as ethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether may be used.

In addition, the buffer layer 34 may be a solid electrolyte in which a lithium salt is dispersed in a polymer, or may be a gel electrolyte in which an organic electrolytic solution in which a lithium salt is dissolved is swollen in a polymer. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiTFSI (LiN (SO ₂ CF ₃ ) ₂ ), LiFSI (LiN (SO ₂ F)) ₂ , LiBOB (lithium bisoxalatoborate), and the like. .

  Examples of the polymer include PEO (polyethylene oxide) and PPO (polypropylene oxide). The polymer serving as the host for the gel electrolyte is PEO (polyethylene oxide), PVA (polyvinyl alcohol), PAN (polyacrylonitrile), PVP (polyvinylpyrrolidone), PEO-PMA (crosslinked product of polyethylene oxide-modified polymethacrylate), PVdF (polyfluoride). And vinylidene fluoride), PVA (polyvinyl alcohol), PAA (polyacrylic acid), PVdF-HFP (copolymer of polyvinylidene fluoride and hexafluoropropylene), and the like.

As shown in FIG. 3, in the negative electrode composite 31 according to the present embodiment, a laminate of a negative electrode layer 33, a buffer layer 34, and a solid electrolyte 35 is sandwiched between an upper exterior body 36 and a lower exterior body 37. It has a form.
The upper exterior body 36 is configured using a laminate film (laminate material) composed of a gas barrier metal layer 36a, an upper resin layer 36b, and a lower resin layer 36c.

  The metal layer 36a of the laminate film is a metal foil made of, for example, stainless steel or aluminum.

As the resin layers 36b and 36c of the laminate film, resins having high heat durability and strength are preferable, and those having durability against the organic solvent contained in the hardly volatile aqueous electrolyte solution are particularly preferable. Particularly preferred are polyolefin resins. Examples of the polyolefin resin include polyethylene (PE resin) and polypropylene (PP resin).
In the embodiment of FIG. 3, PP resin is used as the resin layers 36b and 36c.

The upper exterior body 36 is joined to the solid electrolyte 35 at a joint portion 38 as shown in FIG. The joining portion 38 can be configured by means known to those skilled in the art, such as an adhesive or a heat-welded film.
The upper exterior body 36 uses a polyolefin resin such as a polypropylene resin or a polyethylene resin for the resin layer 36c, so that the melting point is low, the heat processing is easy, and it is suitable for heat sealing (thermal welding).

In the embodiment of FIG. 3, the lower exterior body 37 is also configured using a laminate film of a metal layer 37a and resin layers 37b and 7c.
Both the upper exterior body 36 and the lower exterior body 37 employ the metal foil as the core material as described above, and have gas barrier properties.

  The negative electrode composite 31 includes an upper exterior member 36, a buffer layer (a separator for a lithium ion battery) 34, and a negative electrode current collector (copper foil) 32 so that the solid electrolyte 35 and the negative electrode layer (metal Li) 33 face each other. The negative electrode layer (metal lithium) 33 and the lower exterior material 37 are stacked in this order, and the end portions are heat-welded and bonded with a heat sealer.

  In the case of the negative electrode composite 31 according to the embodiment of FIG. 3, the upper exterior material (metal foil laminate material) 36 to which the solid electrolyte 35 is bonded is a PP resin laminate material. Therefore, it differs from a conventional metal foil laminate material of PP resin film (PP resin / Al foil / PET resin three-layer laminate material, etc.) only on one side. The conventional metal foil laminate material is PET resin or the like on one side, and has no resistance to a hardly volatile aqueous electrolyte solution mixed with an organic solvent. In the negative electrode composite 31 according to the present embodiment, there is no fear of damage to the metal foil laminate material due to such a reason.

  Further, since the upper exterior material 36 is a laminate material of PP resin on both sides and the lower exterior material 37 is a similar laminate material, the PP resin having heat sealability is bonded to each other when the negative electrode composite 31 is manufactured. It only has to be done and the burden on the process is small. That is, since the opposing layers of the upper exterior material 36 and the lower exterior material 37 are made of PP resin, they can be easily joined by thermal welding.

  The upper exterior material (metal foil laminate material) 36 uses a PP resin laminate material on both the upper and lower surfaces. However, the PP resin on both the upper and lower surfaces is not limited to three layers, and one or more resin layers may be laminated on the inner layer directed to the Al foil to form three or more layers. The same applies to the lower exterior member 37.

In the embodiment described with reference to FIG. 3, the solid electrolyte 35 is provided only on one surface of the negative electrode composite 31. FIG. 4 shows a form in which the solid electrolytes 35 are provided on both surfaces of the negative electrode composite 31.
In the embodiment of FIG. 4, a negative electrode current collector 32, a negative electrode layer (metal lithium negative electrode) 33 composed of a negative electrode active material, a buffer layer 34, and a solid electrolyte (separating layer) 35 are stacked, In the characteristic that the opening part of the upper exterior body 36 mentioned later is located in the upper surface of the solid electrolyte 35, it does not differ from embodiment of FIG. Moreover, the member to employ | adopt is the same. However, in place of the lower exterior body 37 employed in the embodiment of FIG. 3, a negative electrode current collector 32 is sandwiched between a negative electrode layer (metal lithium negative electrode) 33 composed of a negative electrode active material, a buffer layer 34, A solid electrolyte (separating layer) 35 is stacked to provide a similar configuration with approximately line symmetry.

In the embodiment shown in FIG. 4, the upper exterior materials 36 and 36 are both metal foil laminates made of double-sided PP resin. As a result, there is no risk of damage to the metal foil laminate material as in the embodiment of FIG.
In addition, in the case of the structure of FIG. 4, the volume can be made smaller than the structure in which one surface of one air electrode is directly opposed to one surface of one negative electrode composite 31 and sealed in a container.

  Since the metal-air battery according to the present invention including the embodiment described with reference to FIGS. 3 and 4 is composed of the PP resin on the side of the negative electrode composite that contacts the non-volatile electrolyte, the PET resin Unlike the conventional example using, there is no possibility of damage even if a hardly volatile aqueous electrolyte solution is used. In addition, PP resin can also be used as other polyolefin resin provided with the characteristic more than equivalent.

FIG. 5 shows an embodiment of a metal-air battery according to the present invention. This embodiment will also be described as an aqueous lithium battery.
The aqueous lithium battery according to the present embodiment has a negative electrode composite 71 and a positive electrode structure (positive electrode part) 73 provided with a positive electrode layer 72 containing a conductive material facing each other. The layer 72 is filled with a hardly volatile aqueous electrolyte solution 74, and the solid electrolyte (separating layer) 75 of the negative electrode composite 71 and the positive electrode layer 72 of the positive electrode structure 73 become the hardly volatile aqueous electrolyte solution 74. It is configured as a structure that touches.

The layer configuration of the negative electrode composite 71 is the same as the layer configuration of the negative electrode composite 31 described with reference to FIG. However, as shown in FIG. 5, the negative electrode composite 71 has a concave cross section.
The materials and functions of the negative electrode layer 76, the buffer layer 77, the solid electrolyte 75, the negative electrode current collector 78, and the upper exterior body 79 are the same as the corresponding negative electrode layer 33, buffer layer 34, solid electrolyte 35, and negative electrode current collector 32. 3 and the upper exterior body 36, and the description of FIG.
However, in the lower exterior body 80, the metal layer 80a and the upper resin layer 80b are the same as the lower exterior body 37, and the lower resin layer 80c is made of PET resin. This is because such a laminate of PP resin / Al foil / PET resin is rather common. The PET resin can be replaced with a resin other than the PET resin, for example, a resin having an equivalent performance such as a nylon resin, and a laminate material having a three-layer structure or more using a PET resin, a nylon resin, or the like is used. It is good. Note that the PP resin layer (upper resin layer 80 b) can also be configured as a resin layer in which three or more layers are laminated, as described above for the lower exterior body 37.

The negative electrode composite 71 can be combined with the positive electrode part to constitute a metal-air battery.
The positive electrode part is configured as a positive electrode structure 73. Such a positive electrode structure 73 is made of a material having conductivity and gas diffusibility, a material in which fine particles of noble metal such as platinum and gold are supported on conductive carbon black, or a material having catalytic activity such as MnO _2. And a positive electrode layer 72 composed of a mixture of carbon black, a positive electrode current collector 81 electrically connected to the positive electrode layer 72, and a positive electrode exterior body 82.

The positive electrode layer 72 has a thin plate shape. The positive electrode layer 72 includes a positive electrode exterior body 82. One surface of the positive electrode layer 72 faces one surface of the negative electrode composite 71 (that is, the surface of the solid electrolyte 75). The other surface of the positive electrode layer 72 faces the positive electrode exterior body 82.
The positive electrode exterior body 82 has a layer structure in which a PP resin 82c, an aluminum foil 82a, and a PET resin 82b are laminated in this order from the inside. As shown in FIG. 5, the positive electrode exterior body 82 is welded to the upper exterior body 79 of the negative electrode composite 71 with the positive electrode layer 72 interposed therebetween. The upper exterior body 79 is made of PP resin as the outermost layers on both sides, and can be joined to the PP resin 82c of the positive electrode exterior body 82 by thermal welding.

In addition, as with the lower exterior body 80 described above, the positive electrode exterior body 82 can also have a structure in which three or more resin layers are laminated as long as each of the PP resin 82c and the PET resin 82b does not impair the function. .
The electrolytic solution chamber 83 formed by the negative electrode composite 71 and the positive electrode structure 73 is filled with a hardly volatile aqueous electrolyte 74. In FIG. 5, the hardly volatile aqueous electrolyte 74 is indicated by an ellipse. However, in the case where the hardly volatile aqueous electrolyte 74 is a liquid, it is filled in conformity with the internal form of the electrolyte chamber 83 as understood by those skilled in the art.

  Further, the positive electrode exterior body 82 is provided with an air hole 84. The air holes 84 are closed with a moisture permeable waterproof sheet (PTFE resin or PP resin system). As a result, air necessary for discharge can be taken in while the electrolyte chamber 83 remains watertight, and stable discharge can be performed.

  The positive electrode current collector 81 may be present stably in the operating range of the metal-air battery and may have a desired conductivity. Examples of the material for the positive electrode current collector include metal materials such as stainless steel, nickel, aluminum, gold, and platinum, and carbon fiber materials such as carbon cloth and carbon nonwoven fabric.

[Example 1]
The volatility test of the hardly volatile aqueous electrolyte solution used in the metal-air battery according to the present invention was performed. The contents are shown below.

1. Preparation of hardly volatile aqueous electrolyte solution A 2M (mol / L) lithium chloride aqueous solution was prepared. 9 mL of N-methylpyrrolidone (NMP) was added to 1 mL of this 2M lithium chloride aqueous solution to obtain an electrolytic solution 1. Similarly, 8 mL of N-methylpyrrolidone (NMP) was added to 2 mL of 2M aqueous lithium chloride solution, and 7 mL of N-methylpyrrolidone (NMP) was added to 3 mL of electrolyte solution 2 and 2M lithium chloride aqueous solution. 6 mL of N-methylpyrrolidone (NMP) was added to 4 mL of an aqueous lithium chloride solution, and 5 mL of N-methylpyrrolidone (NMP) was added to 5 mL of an electrolytic solution 2 and 2M aqueous lithium chloride to obtain an electrolytic solution 5. Furthermore, 9 mL of dimethyl sulfoxide (DMSO) was added to 1 mL of 2 M lithium chloride aqueous solution, and electrolyte 6 was added. 8 mL of dimethyl sulfoxide (DMSO) was added to 2 mL of 2 M lithium chloride aqueous solution, and dimethyl sulfoxide was added to 3 mL of electrolyte 7 and 2 M lithium chloride aqueous solution. 7 mL of (DMSO) was added, 6 mL of dimethyl sulfoxide (DMSO) was added to 4 mL of electrolyte solution 8 and 2M lithium chloride aqueous solution, and 5 mL of dimethyl sulfoxide (DMSO) was added to 5 mL of electrolyte solution 9 and 2M lithium chloride aqueous solution. It was. Table 1 shows the experimental conditions of Example 1.

2. Volatilization test of hardly volatile aqueous electrolyte solution All the electrolyte solutions 1 to 10 prepared in “1. Preparation of hardly volatile aqueous electrolyte solution” were placed in a sample bottle and weighed. The sample was allowed to stand at room temperature and normal pressure without a lid, and weighed again every day. This was carried out for 10 days, and the results of evaluating the volatilization amount from the change in weight over 10 days are shown in FIG. 6 (electrolytic solutions 1 to 10) and Table 1.

[Comparative Example 1]
As a comparative example, a volatilization test performed with a conventional aqueous electrolyte is described.
1. Preparation of electrolyte solution 10 mL of 2M (mol / L) lithium chloride aqueous solution was prepared and used as the electrolyte solution.
2. Volatilization test of electrolyte solution All the electrolyte solutions prepared in “1. Preparation of electrolyte solution” were placed in a sample bottle and weighed. The sample was allowed to stand at room temperature and normal pressure without a lid, and weighed again every day. This was carried out for 10 days, and the results of evaluating the volatilization amount from the change in weight over 10 days are shown in FIG. 6 (Comparative Example 1) and Table 1. As a result, in Comparative Example 1, a weight loss of 20% or more occurred after 10 days, whereas it was confirmed that all the electrolytic solutions of Example 1 suppressed the weight loss more than Comparative Example 1. In particular, the electrolytic solution 2 had little weight change and was excellent in suppressing the volatilization of the electrolytic solution.
Table 1 [Results of volatilization test of electrolytes of Example 1 and Comparative Example 1]

[Example 2]
1. Production of positive electrode A positive electrode was produced by the following procedure.
(1) Weighed 20.8 g of MnO as a positive electrode catalyst, 0.1 g of ketjen black (specific surface area 800 m 2 / g) as a conductive auxiliary agent, and 0.1 g of polytetrafluoroethylene (PTFE) as a binder (binder). The mixture was transferred to a mortar, and 5 ml of ethanol was added and kneaded.
(2) The kneaded product of (1) was sandwiched between two 2 × 6 cm size carbon cloths, and rolled and pressure-bonded to a thickness of 1 mm with a roll press machine (an ultra-small tabletop heat roll press machine manufactured by Hosen Co., Ltd.). Except for the portion crimped to the 2 × 2 cm portion of the 2 × 6 cm size carbon cloth end, it was removed. Thereafter, it was naturally dried in air for 24 hours to produce a positive electrode.

2. Production of negative electrode composite In a glove box under an argon atmosphere, an exterior material obtained by punching the center part of a laminate film of PP resin / Al foil / PP resin double-sided PP resin into 2 × 2 cm square, an acid-modified polypropylene film punched product ( 3 × 3 cm for the outer periphery, 2 × 2 cm for the inner periphery, 2.5 × 2.5 cm square solid electrolyte (LTAP), and an acid-modified polypropylene film punched product (the outer periphery 3 × 3 cm, the inner periphery 2 × 2 cm). Then, it was heat-welded with a heat sealer to obtain an upper exterior material of the negative electrode composite.

Metal Li (size 1.45 × 1.4 cm, thickness 200 μm) is joined to the upper exterior material, the separator for lithium ion batteries, and the copper foil (current collector) so that the solid electrolyte and metal Li face each other. And the metal foil laminate film of the lower exterior material were stacked in this order, and the three edges were heat welded and joined with a heat sealer. From the unjoined end, 1 ml of a non-aqueous electrolyte (1MLiPF6 / EC: EMC = 1: 1) was injected into the negative electrode composite. Finally, the end of the remaining one side was joined and sealed with a heat sealer, and a negative electrode composite similar to that described with reference to FIG. 3 was produced.
In addition, LTAP (LICC manufactured by OHARA INC.) Was used as the solid electrolyte.

3. Production of Air Battery Cell In the same manner as described for the positive electrode outer package 82 in FIG. 5, a hole having a diameter of about 1 mm for the air hole of the metal foil laminate material (positive electrode outer package) of PP resin (inner surface) / Al foil / PET resin. The PP resin-based moisture permeable waterproof sheet was thermally welded to the PP resin (inner surface) side of the laminate material to provide air holes. The positive electrode was arranged on the negative electrode composite similar to that shown in FIG. 3 and covered with the positive electrode outer package, and the three sides were heat-welded and joined.
Mix 3 mL of 2M (mol / L) lithium chloride aqueous solution and 7 mL of N-methylpyrrolidone (NMP) to prepare an electrolyte solution of 70% NMP, and inject 2 mL of electrolyte solution from one side that is not joined. One side was joined to form an air battery cell.

4). Discharge and charge test In the cell corresponding to the theoretical capacity of 84 mAh in the example, the change in voltage when discharging and charging for 7 hours at a current density of 4 mA / cm 2 equivalent to 0.05 C with respect to the theoretical capacity was brought to a temperature of 25 ° C. The results of measurement with HJ1001SD8 manufactured by Hokuto Denko are shown in FIG. 7 (Example 2: structure of the present invention).

[Comparative Example 2]
As a comparative example, a discharge test conducted with a conventional aqueous electrolyte is described.
1. Fabrication of positive electrode
The same method as in Example 2 was used.
2. Production of negative electrode composite The negative electrode composite was produced in the same manner as in Example 2, but the material of the upper exterior material of the negative electrode composite was PET resin / Al foil / PP resin.

3. Production of Air Battery As shown in FIG. 5, a hole of about 1 mm in diameter for the air hole of a metal foil laminate material of PP resin (inner surface) / Al foil / PET resin is provided, and a PP resin moisture permeable waterproof sheet is laminated. The PP resin (inner surface) side was thermally welded and joined to provide air holes to form an air battery exterior material. A positive electrode layer was arranged on the same negative electrode composite as described above with reference to FIG. 3, a positive electrode outer package was placed, and three sides were heat-welded and joined. 2 mL of 2M (mol / L) lithium chloride aqueous solution was injected, and the remaining one side was joined to form an air battery cell.

4). Discharge and charge test It implemented by the same method as Example 2, and the result was shown in FIG. 7 (comparative example 2: conventional structure). As a result, in discharge, the discharge voltage decreased with the discharge time in Comparative Example 2, whereas in Example 2, the decrease in the discharge voltage with the increase in the discharge time was small and relatively stable. Similarly, in the charging, the charging voltage in Comparative Example 2 increases with the charging time, whereas in Example 2, the charging voltage increases with the increase in the charging time, and the charging voltage is stable. It was.

DESCRIPTION OF SYMBOLS 1 Aqueous system lithium air battery 2 Positive electrode 3 Aqueous system electrolyte 4 Solid electrolyte 5 Negative electrode 6 Buffer layer (protective layer)
7 Load 31, 71 Negative electrode composite 32, 78 Negative electrode current collector 33, 76 Negative electrode layer 34, 77 Buffer layer 35, 75 Solid electrolyte 36, 79 Upper exterior body 37, 80 Lower exterior body 38 Joint 36a, 37a, 80a Metal layer 36b, 36c, 37b, 37c, 80b, 80c Resin layer 72 Positive electrode layer 73 Positive electrode structure 74 Non-volatile aqueous electrolyte 81 Positive electrode current collector 82 Positive electrode exterior 83 Electrolyte chamber 84 Air hole

Claims (9)

  A metal-air battery comprising a positive electrode, an electrolytic solution, a solid electrolyte, and a negative electrode, wherein the electrolytic solution is a non-volatile aqueous electrolyte solution obtained by blending an aqueous solvent with an organic solvent, and the non-volatile aqueous solution A metal-air battery in which the system electrolyte solution is 60% by mass to 80% by mass and contains the organic solvent.   2. The metal-air battery according to claim 1, wherein the organic solvent has a vapor pressure of less than 3000 Pa at 25 ° C. 3.   The metal-air battery according to claim 1, wherein the organic solvent is hygroscopic.   The organic solvent is selected from the group consisting of NMP (N-methyl-2-pyrrolidone), DMSO (dimethyl sulfoxide), DMF (N, N-dimethylformamide) and a mixture of two or more thereof. The metal-air battery according to any one of claims 1 to 3, wherein:   The metal-air battery according to any one of claims 1 to 4, wherein the negative electrode active material used for the negative electrode is a metal lithium or an alloy or compound containing metal lithium as a main component. A negative electrode composite comprising a negative electrode current collector, a negative electrode layer composed of a negative electrode active material, a buffer layer, and a solid electrolyte sandwiched between an upper exterior body and a lower exterior body. 6. The metal-air battery according to claim 1 , wherein a layer in contact with the hardly volatile aqueous electrolyte solution is made of a polyolefin resin . 7. The metal-air battery according to claim 6 , wherein, of the layers constituting the upper exterior body, a layer bonded to the solid electrolyte is made of a polyolefin-based resin . The metal-air battery according to claim 6 or 7, wherein the core layer of the laminate constituting the upper exterior body is made of a metal foil.   The metal-air battery according to any one of claims 6 to 8, wherein opposing layers of the upper exterior body and the lower exterior body are made of a polyolefin-based resin such as polypropylene resin.

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