JP2014075269A - Metal-air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-air battery having discharge capacity higher than that of conventional ones.SOLUTION: A metal-air battery includes a positive electrode layer, a negative electrode layer and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a first layer disposed on the electrolyte layer side and a second layer disposed on the side opposite to the electrolyte layer side. Each of the first layer and the second layer contains a solid electrolyte and a carbon material, and a ratio of the content ratio of the solid electrolyte contained in the second layer relative to the content ratio of the solid electrolyte contained in the first layer is more than 1 and 2.1 or less.

Description

  The present invention relates to a metal-air battery that uses oxygen as a positive electrode active material.

  With the spread and progress of devices such as mobile phones in recent years, it is desired to increase the capacity of the battery as the power source. Under such circumstances, the metal-air battery uses the oxygen in the atmosphere as the positive electrode active material at the positive electrode, and the oxygen reduction reaction of the oxygen is performed. On the other hand, the redox of the metal constituting the negative electrode is performed at the negative electrode. Since the reaction can be performed, the battery can be charged or discharged, so that it has a high energy density and has attracted attention as a high-capacity battery that is superior to the currently used lithium ion batteries (Non-patent Document 1).

  In order to increase the capacity of a lithium air battery, a lithium air battery including a positive electrode mixed with carbon and a solid electrolyte having lithium ion conductivity as an electrode catalyst has been proposed (Patent Document 1).

JP 2010-244827 A

National Institute of Advanced Industrial Science and Technology (AIST), “Development of high-performance lithium-air battery with new structure”, [online], press release on February 24, 2009, [search on August 19, 2011], Internet <http: // www. aist. go. jp / aist_j / press_release / pr2009 / pr20090224 / pr20090224. html>

  As described above, for the purpose of increasing the capacity of a lithium air battery, a lithium air battery having a positive electrode in which carbon and a solid electrolyte are mixed has been proposed. However, a metal air battery having still higher capacity is still proposed. Is desired.

The present invention is a metal-air battery including a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
The positive electrode layer includes a first layer disposed on the electrolyte layer side and a second layer disposed on the side opposite to the electrolyte layer side,
Each of the first layer and the second layer includes a solid electrolyte and a carbon material;
The ratio of the content ratio of the solid electrolyte contained in the second layer to the content ratio of the solid electrolyte contained in the first layer is greater than 1 and 2.1 or less.
It is a metal-air battery.

  ADVANTAGE OF THE INVENTION According to this invention, the metal air battery which has a higher discharge capacity than before can be provided.

FIG. 1 is a schematic cross-sectional view showing the configuration of a positive electrode layer used in a metal-air battery according to the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of the positive electrode layer used in the metal-air battery of the comparative example. FIG. 3 is a schematic cross-sectional view of an example of an electrochemical cell including a metal-air battery according to the present invention. FIG. 4 is a graph showing the relationship between the ratio of the solid electrolyte content contained in the second layer with respect to the solid electrolyte content contained in the first layer and the discharge capacity of the cell.

  The positive electrode layer included in the metal-air battery according to the present invention includes a first layer disposed on the electrolyte layer side and a second layer disposed on the side opposite to the electrolyte layer side. And the second layer includes a solid electrolyte and a carbon material, respectively, and the ratio of the content ratio of the solid electrolyte included in the second layer to the content ratio of the solid electrolyte included in the first layer is larger than 1. .1 or less.

  In a metal-air battery, during discharge, an oxidation-reduction reaction occurs in which oxygen in the air is reduced in the positive electrode layer and metal ions in the negative electrode are oxidized.

  When a positive electrode layer formed by mixing a solid electrolyte with a conductive material such as carbon is used in a metal-air battery as in Patent Document 1, a solid electrolyte that is a catalyst having high oxygen reduction activity in the positive electrode layer Since the discharge product is deposited uniformly, deposits are likely to be deposited on the entire positive electrode layer, and the positive electrode layer is opposite to the electrolyte layer side (metal ion supply side) and the electrolyte layer side ( It has been found that problems such as the oxygen supply side) being clogged and the supply of oxygen and metal ions being hindered are likely to occur.

  In particular, before metal ions such as lithium ions reach the side opposite to the electrolyte layer side (oxygen supply side) of the positive electrode layer, metal ions are trapped on the electrolyte layer side (metal ion supply side), It was found that the supply of metal ions is likely to be hindered.

  In order to solve such a problem, the present inventor is a metal-air battery including a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer has metal ion conductivity. The present inventors have found a metal-air battery that includes a solid electrolyte and a carbon material, and has a configuration in which the content of the solid electrolyte in the positive electrode layer is large in the oxygen supply region of the positive electrode layer and small in the region of the electrolyte layer. Thus, by using the positive electrode layer in which the content ratio of the solid electrolyte is inclined for the metal-air battery, it becomes possible to improve the supply of oxygen and metal ions, and the discharge capacity of the metal-air battery can be improved. .

  The configuration of the positive electrode layer used in the metal-air battery according to the present invention will be described with reference to the drawings.

  In FIG. 1, the cross-sectional schematic diagram showing the structure of the positive electrode layer used for the metal air battery which concerns on this invention is shown. As shown in FIG. 1, the positive electrode layer used in the metal-air battery according to the present invention includes a first layer 11 disposed on the electrolyte layer side (metal ion supply side) and a side opposite to the electrolyte layer side (oxygen layer). The second layer 12 is disposed on the supply side, and the first layer 11 and the second layer 12 each include a solid electrolyte and a carbon material.

  The content rate of the solid electrolyte contained in the second layer is larger than the content rate of the solid electrolyte contained in the first layer. That is, the ratio of the content ratio of the solid electrolyte contained in the second layer to the content ratio of the solid electrolyte contained in the first layer is greater than 1, preferably 1.2 or more, more preferably 1.3 or more. It is.

  By increasing the ratio of the content ratio of the solid electrolyte contained in the first layer to the content ratio of the solid electrolyte contained in the second layer, the electron conductivity is increased in the region on the electrolyte layer side of the positive electrode layer. While ensuring, it can suppress generation | occurrence | production of a discharge product and can ensure supply of metal ions, such as lithium ion, and can utilize the area | region by the side of the air hole of a positive electrode layer effectively.

  The ratio of the content ratio of the solid electrolyte contained in the second layer to the content ratio of the solid electrolyte contained in the first layer is 2.1 or less, preferably 1.9 or less, more preferably 1 .8 or less.

  If the ratio of the content ratio of the solid electrolyte contained in the second layer to the content ratio of the solid electrolyte contained in the first layer is too large, the region on the opposite side of the positive electrode layer from the electrolyte layer side (region on the oxygen supply side) ), The electron conductivity is reduced, or the supply of oxygen is likely to be hindered due to the generation of a large amount of discharge products. Therefore, the upper limit value of the ratio is preferably in the above range.

  The content ratio of the solid electrolyte contained in the first layer and the second layer is preferably 10 to 40% by mass, respectively. For example, when the content ratio of the solid electrolyte contained in the second layer is 30% by mass, the content ratio of the solid electrolyte contained in the first layer is preferably 14.3 so as to satisfy the above ratio. The content may be from mass% to less than 30 mass%, more preferably from 15.8 mass% to less than 30 mass%, and even more preferably from 16.7 mass% to less than 30 mass%.

  As the solid electrolyte material contained in the first layer and the second layer, a material that can be used as a solid electrolyte of an all-solid battery can be used, and a solid electrolyte having lithium ion conductivity can be preferably used.

Examples of solid electrolyte materials contained in the first layer and the second layer include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ S—P ₂ S ₅ , and LiI—Li ₂ S. _{-B 2 S 3, Li 3 PO} 4 -Li 2 S-Si 2 S, Li 3 PO 4 -Li 2 S-SiS 2, LiPO 4 -Li 2 S-SiS, LiI-Li 2 S-P 2 O 5 , LiI—Li ₃ PO ₄ —P ₂ S ₅ , sulfide-based solid electrolytes such as Li ₂ S—P ₂ S ₅ , Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₂ O—B ₂ O ₃ , Li ₂ O—B ₂ O ₃ —ZnO or other oxide-based amorphous solid electrolyte, Li _1.3 Al _0.3 Ti _0.7 (PO ₄ ) ₃ , Li _{1 + x + y A x Ti 2-x Si y} P 3-y O 12 (A is, Al or Ga, 0 ≦ x ≦ 0.4,0 < y ≦ 0.6), [(B 1/2 Li 1/2) _1-z C _z] TiO ₃ Is B, La, Pr, Nd or Sm, C is Sr or Ba, 0 ≦ z ≦ 0.5) , Li 5 La 3 Ta 2 O 12, Li 7 La 3 Zr 2 O 12, (LLZO), Li 6 Crystalline oxides such as BaLa ₂ Ta ₂ O ₁₂ or Li _3.6 Si _0.6 P _0.4 O ₄ , crystalline oxynitrides such as Li ₃ PO _{(4-3 / 2w)} N _w (w <1), or LiI , it can be used _{LiI-Al 2 O 3, Li} 3 N, or Li ₃ N-LiI-LiOH and the like. Further, as the solid electrolyte contained in the first layer and the second layer, a semi-solid polymer electrolyte such as polyethylene oxide containing lithium salt, polypropylene oxide, polyvinylidene fluoride, or polyacrylonitrile can also be used.

  The thickness of the first layer and the second layer included in the positive electrode layer used in the metal-air battery according to the present invention is preferably 10 to 200 μm, more preferably 20 to 100 μm, and still more preferably 30 to 70 μm. Can do.

  The carbon material contained in the first layer and the second layer is preferably a porous material. Preferred examples of the porous material include carbon black such as ketjen black, acetylene black, channel black, furnace black, and mesoporous carbon, activated carbon, carbon carbon fiber, and the like, and a carbon material having a large specific surface area is more preferably used. . Moreover, as a porous material, what has the pore volume of nanometer order of about 1 mL / g is desirable.

  The carbon material preferably accounts for 10 to 90% by mass, more preferably 20 to 70% by mass, and more preferably 40 to 50% by mass in the positive electrode layer. The content of the carbon material contained in the first layer and the second layer can be changed according to the content ratio of the solid electrolyte contained in the first layer and the second layer, respectively.

  Further, the types of the carbon material contained in the first layer and the carbon material contained in the second layer may be the same or different. The first layer and the second layer preferably comprise the same carbon material.

  In the positive electrode layer used in the metal-air battery according to the present invention, the first layer is disposed on the electrolyte layer side, the second layer is disposed on the opposite side (oxygen supply side) to the electrolyte layer side, and the solid electrolyte As long as the content ratio of is higher in the second layer than in the first layer at the predetermined ratio, it can have other modified configurations. For example, as shown in FIG. 1, the first layer and the second layer may be arranged adjacent to each other, or in addition to the first layer and the second layer, a third layer or more. In this case, the third layer or even more may be provided so that the solid electrolyte content has a gradient between the first layer and the second layer having different solid electrolyte content. Layers can be placed.

  The first layer and the second layer can include a binder. As the binder, for example, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, a thermoplastic resin such as polypropylene, polyethylene, polyacrylonitrile, or styrene butadiene rubber (SBR) is used. be able to. The binder preferably occupies 1 to 30% by mass in the first layer and the second layer. The content of the binder contained in the first layer and the content of the binder contained in the second layer should be changed according to the content of the solid electrolyte and the carbon material that can be contained in the first layer and the second layer. Can do.

  The first layer and the second layer may include a redox catalyst. Examples of the redox catalyst include metal oxides such as manganese dioxide, cobalt oxide, and cerium oxide, noble metals such as Pt, Pd, Au, and Ag, Examples thereof include transition metals such as Co, metal phthalocyanines such as cobalt phthalocyanine, and organic materials such as Fe porphyrin. The redox catalyst preferably occupies 1 to 90% by mass, more preferably 1 to 50% by mass, and even more preferably 1 to 30% by mass in each of the first layer and the second layer.

  The metal-air battery according to the present invention can include the above-described positive electrode layer, negative electrode layer, and an electrolyte layer between the positive electrode layer and the negative electrode layer.

  The electrolyte layer conducts metal ions between the positive electrode layer and the negative electrode layer, and can include a liquid electrolyte, a solid electrolyte, a gel electrolyte, a polymer electrolyte, or a combination thereof.

  As the liquid electrolyte that can be included in the electrolyte layer between the positive electrode layer and the negative electrode layer, a liquid that can exchange metal ions between the positive electrode layer and the negative electrode layer can be used, and an aprotic organic solvent, Or it can be an ionic liquid or the like.

  Examples of organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane. 1,3-dioxolane, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, glymes and the like.

  As the ionic liquid, those having high resistance to oxygen radicals capable of suppressing side reactions are preferable. For example, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide ( DEMETFSA), N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) amide (PP13TFSA), or combinations thereof. Further, as the liquid electrolyte, a combination of the above ionic liquid and an organic solvent can be used.

A supporting salt may be dissolved in the liquid electrolyte. Examples of the supporting salt include lithium ions and the following anions:
Halide anions such as Cl ⁻ , Br ⁻ and I ⁻ ; Boron anions such as BF ₄ ⁻ , B (CN) ₄ ⁻ and B (C ₂ O ₄ ) ₂ ⁻ ; (CN) ₂ N ⁻ , [N ( Amide anion or imide anion such as CF ₃ ) ₂ ] ⁻ , [N (SO ₂ CF ₃ ) ₂ ] ⁻ ; RSO ₃ ⁻ (hereinafter, R represents an aliphatic hydrocarbon group or aromatic hydrocarbon group), RSO Sulfate anion or sulfonate anion such as ₄ ⁻ , R ^f SO ₃ ⁻ (hereinafter, R ^f represents a fluorinated halogenated hydrocarbon group), R ^f SO ₄ ^—, etc .; R ^f ₂ P (O) O ⁻ Phosphorus-containing anions such as PF ₆ ⁻ , R ^f ₃ PF ₃ ⁻ ; antimony-containing anions such as SbF ₆ ; or anions such as lactate, nitrate ion, trifluoroacetate, tris (trifluoromethanesulfonyl) methide,
A salt consisting of
For example, LiPF ₆ , LiBF ₄ , lithium bis (trifluoromethanesulfonyl) amide (LiN (CF ₃ SO ₂ ) ₂ , hereinafter referred to as LiTFSA), LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ and LiClO _{4 and the} like, and LiTFSA is preferably used. Two or more such supporting salts may be used in combination. Moreover, although the addition amount of the supporting salt with respect to a liquid electrolyte is not specifically limited, It is preferable to set it as about 0.1-1 mol / kg.

  The polymer electrolyte that can be contained in the electrolyte layer disposed between the positive electrode layer and the negative electrode layer can be used together with, for example, an ionic liquid, and preferably contains a lithium salt and a polymer. As the lithium salt, for example, the lithium salt used as the support salt described above can be used. The polymer is not particularly limited as long as it forms a complex with a lithium salt, and examples thereof include polyethylene oxide.

  The gel electrolyte that can be included in the electrolyte layer disposed between the positive electrode layer and the negative electrode layer can be used, for example, with an ionic liquid, and preferably contains a lithium salt, a polymer, and a nonaqueous solvent. The lithium salt described above can be used as the lithium salt. The non-aqueous solvent is not particularly limited as long as it can dissolve the lithium salt. For example, the above-described organic solvents can be used. These nonaqueous solvents may be used alone or in combination of two or more. The polymer is not particularly limited as long as it can be gelled. Examples thereof include polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride (PVdF), polyurethane, polyacrylate, and cellulose. It is done.

  As the solid electrolyte material that can be included in the electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a material that can be used as a solid electrolyte of an all-solid battery can be used, and the solid electrolyte included in the positive electrode layer described above. Any of the materials or a combination thereof can be used, and preferably the same solid electrolyte material as the solid electrolyte material contained in the positive electrode layer can be used.

  The electrolyte layer included in the metal-air battery according to the present invention may include a separator. Although it does not specifically limit as a separator, For example, polymer nonwoven fabrics, such as a nonwoven fabric made from a polypropylene, a nonwoven fabric made from a polyphenylene sulfide, microporous films, such as olefin resin, such as polyethylene and a polypropylene, or these combinations can be used. For example, the electrolyte layer may be formed by impregnating a separator with a liquid electrolyte or the like.

  The negative electrode layer included in the metal-air battery according to the present invention is a layer containing a negative electrode active material containing a metal. As the negative electrode active material, a metal, an alloy material, a carbon material, or the like can be used. For example, an alkali metal such as lithium, sodium, or potassium, an alkaline earth metal such as magnesium or calcium, or a Group 13 element such as aluminum Transition metals such as zinc, iron, silver, alloy materials containing these metals, materials containing these metals, carbon materials such as graphite, and negative electrode materials that can be used for lithium ion batteries, etc. Can be mentioned.

  When a material containing lithium is used as the negative electrode active material, a lithium-containing material, an alloy containing lithium element, or an oxide, nitride, or sulfide containing lithium element is used as the material containing lithium. be able to. Examples of the alloy containing lithium element include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy. Examples of the metal oxide containing lithium element include lithium titanium oxide. Examples of the metal nitride containing lithium element include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride.

  The negative electrode layer may further contain a conductive material and / or a binder. For example, when the negative electrode active material is in the form of a foil, it can be a negative electrode layer containing only the negative electrode active material, and when the negative electrode active material is in a powder form, the negative electrode layer has a negative electrode active material and a binder. be able to. In addition, about a electrically conductive material and a binder, the thing similar to the carbon material and binder which can be used for the above-mentioned positive electrode layer can be used.

  As an exterior material that can be used for the metal-air battery according to the present invention, a material that is usually used as an exterior material for an air battery, such as a metal can, a resin, or a laminate pack, can be used.

  The exterior material can be provided with a hole for supplying oxygen at an arbitrary position, for example, toward the contact surface of the positive electrode layer with air. As the oxygen source, dry air or pure oxygen is preferable.

  The metal-air battery according to the present invention may include an oxygen permeable membrane. The oxygen permeable membrane may be disposed on the oxygen supply side, for example, on the positive electrode layer. As the oxygen permeable membrane, a water-repellent porous membrane that allows oxygen in the air to permeate and prevents moisture from entering can be used. For example, a porous membrane such as polyester or polyphenylene sulfide can be used. . A water repellent film may be provided separately.

  A positive electrode current collector can be disposed adjacent to the positive electrode layer. The positive electrode current collector is usually on the positive electrode layer and can be disposed on the oxygen supply side, but may be disposed between the positive electrode layer and the electrolyte layer. The positive electrode current collector is not particularly limited as long as it is a material conventionally used as a current collector, such as a carbon paper, a porous structure such as a metal mesh, a network structure, a fiber, a nonwoven fabric, etc. A metal mesh formed from SUS, nickel, aluminum, iron, titanium, or the like can be used. A metal foil having oxygen supply holes can also be used as the positive electrode current collector.

  A negative electrode current collector can be disposed adjacent to the negative electrode layer. The negative electrode current collector is not particularly limited as long as it is a material conventionally used as a negative electrode current collector, such as a conductive substrate having a porous structure, a non-porous metal foil, etc. For example, copper, SUS, A metal foil formed from nickel or the like can be used.

  The shape of the metal-air battery according to the present invention is not particularly limited as long as it has an oxygen uptake hole, and can take a desired shape such as a cylindrical shape, a square shape, a button shape, a coin shape, or a flat shape. .

  The metal-air battery according to the present invention can be used as a secondary battery, but may be used as a primary battery.

  Formation of the positive electrode layer and the negative electrode layer included in the metal-air battery according to the present invention can be performed by any conventional method. For example, when forming a positive electrode layer containing carbon particles, solid electrolyte particles, and a binder, a predetermined amount of carbon particles, solid electrolyte particles, and a binder are mixed with an appropriate amount of a solvent such as ethanol, and the resulting mixture is mixed. The positive electrode layer can be formed by rolling to a predetermined thickness with a roll press, drying and cutting. Next, the positive electrode current collector is pressure-bonded and heated and vacuum dried to obtain a positive electrode layer in which the current collector is combined.

  Alternatively, a predetermined amount of carbon particles, solid electrolyte particles, and a binder can be mixed with an appropriate amount of solvent to obtain a slurry, and the slurry is coated on a substrate and dried to obtain a positive electrode layer. it can. The positive electrode layer obtained as desired may be press-molded. As a solvent for obtaining the slurry, acetone, NMP or the like having a boiling point of 200 ° C. or less can be used. Examples of the process for applying the slurry onto the base material of the positive electrode layer include a doctor blade method, a gravure transfer method, and an ink jet method. The base material used is not particularly limited, and a current collector plate used as a current collector, a base material having film-like flexibility, a hard base material, and the like can be used. For example, SUS foil, polyethylene terephthalate ( A substrate such as PET) film or Teflon (registered trademark) can be used. The same applies to the method of forming the negative electrode layer.

(Production of cell)
Example 1
22. 44.5 wt% Ketjen Black (KB) (ECP-600JD, manufactured by Ketjen Black International), 33.3 wt% polytetrafluoroethylene (PTFE) binder (F-104, manufactured by Daikin) A 2 wt% Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) (manufactured by NGK Corporation) powder and an appropriate amount of ethanol as a solvent were mixed to obtain a mixture. The obtained mixture was rolled with a roll press, dried and cut to produce a first layer having a diameter of 18 mmφ and a thickness of 75 μm.

30. Ketjen black (KB) (ECP-600JD, manufactured by Ketjenblack International) having a mass ratio of 40.0 wt%, 30.0 wt% polytetrafluoroethylene (PTFE) binder (F-104, manufactured by Daikin), 30. A powder of 0 wt% Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) (manufactured by NGK Corporation) and an appropriate amount of ethanol as a solvent were mixed to obtain a mixture. The obtained mixture was rolled with a roll press, dried and cut to produce a second layer having a diameter of 18 mmφ and a thickness of 75 μm.

  Using SUS304 100 mesh (manufactured by Niraco) as the positive electrode current collector, the first layer, the second layer, and the positive electrode current collector laminated in this order are pressure-bonded, and then heated and vacuum dried. A positive electrode current collector was combined with the positive electrode layer while forming a positive electrode layer having a thickness of 150 μm.

  N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide (DEMETFSA, manufactured by Kanto Chemical) is used as a solvent, and lithium bis (trifluoromethanesulfonyl) amide ( LiTFSA (manufactured by Kishida Chemical Co., Ltd.) was mixed and dissolved in an Ar atmosphere at 25 ° C. for 12 hours to a concentration of 0.35 mol / kg to prepare an electrolyte solution.

  As a negative electrode layer, a metal lithium foil (made by Honjo Metal) having a diameter of 22 mmφ and a thickness of 500 μm was prepared, and attached to a negative electrode current collector of a SUS304 plate (manufactured by Niraco) having a diameter of 22 mm and a thickness of 2 cm.

  As shown in FIG. 3, the negative electrode current collector is placed on the lower side in a metal sealed container 9 in which an insulating resin is interposed between the positive electrode layer and the negative electrode layer so that the positive electrode layer and the negative electrode layer are electrically insulated. The negative electrode current collector 7 and the negative electrode layer 3 were arranged so that a polypropylene nonwoven fabric having a thickness of 40 μm and a diameter of 28 mmφ was arranged on the negative electrode layer 3 as a separator, and 100 μl of the prepared electrolyte was injected. The separator is impregnated to form the electrolyte layer 2, and then the positive electrode layer 1 and the positive electrode current collector 6 are assembled so that the electrolyte solution penetrates into the voids in the positive electrode (air electrode) layer 1. The electrochemical cell 10 for evaluation provided with this was produced.

  Next, the electrochemical cell 10 was placed in a glass desiccator (500 mL specification) with a gas replacement cock, and the atmosphere in the glass desiccator was replaced with an oxygen atmosphere using pure oxygen (Taiyo Nippon Sanso, 99.9%). .

(Comparative Example 1)
40.0 wt% of ketjen black (KB), 30.0 wt% of polytetrafluoroethylene (PTFE) binder, 30.0 _{wt% Li 7 La 3 Zr 2 O} 12 (LLZO) powder, and a solvent An evaluation cell was prepared in the same manner as in Example 1 except that the first layer was prepared using an appropriate amount of ethanol, and the positive electrode layer was obtained by combining the first layer and the second layer. In the glass desiccator, the atmosphere in the glass desiccator was replaced with an oxygen atmosphere.

(Comparative Example 2)
36.3 wt% Ketjen Black (KB), 27.3 wt% polytetrafluoroethylene (PTFE) binder, 36.4 wt% Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) powder, and solvent An evaluation cell was prepared in the same manner as in Example 1 except that the first layer was prepared using an appropriate amount of ethanol, and the positive electrode layer was obtained by combining the first layer and the second layer. In the glass desiccator, the atmosphere in the glass desiccator was replaced with an oxygen atmosphere.

(Comparative Example 3)
50.0 wt% of ketjen black (KB), 37.5 wt% of polytetrafluoroethylene (PTFE) binder, 12.5 _{wt% Li 7 La 3 Zr 2 O} 12 (LLZO) powder, and a solvent An evaluation cell was prepared in the same manner as in Example 1 except that the first layer was prepared using an appropriate amount of ethanol, and the positive electrode layer was obtained by combining the first layer and the second layer. In the glass desiccator, the atmosphere in the glass desiccator was replaced with an oxygen atmosphere.

(Comparative Example 4)
40% by weight ketjen black (KB), 30% by weight polytetrafluoroethylene (PTFE) binder, 30% by weight Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) powder, and an appropriate amount of ethanol as a solvent Except that a positive electrode layer having a thickness of 150 μm as shown in FIG. 2 was obtained, an evaluation cell was prepared in the same manner as in Example 1, put in a glass desiccator, and the atmosphere in the glass desiccator was changed. The atmosphere was replaced with an oxygen atmosphere.

(Discharge test)
The evaluation cell placed in the glass desiccator prepared in Example 1 and Comparative Examples 1 to 4 was allowed to stand for 3 hours in a 60 ° C. thermostat before the start of the test. Then, using a multichannel potentiostat / galvanostat VMP3 (manufactured by Bio-Logic) charge / discharge IV measurement device, the area standard of the positive electrode layer is 0.1 mA under the conditions of 60 ° C., pure oxygen, and 1 atm. The discharge characteristics of the cell were measured at a discharge current density of / cm ² .

  FIG. 4 shows the discharge capacity when the cell voltage of the cells produced in Example 1 and Comparative Examples 1 to 4 is 2.3V.

  Table 1 shows the composition of the first layer and the second layer in Example 1 and Comparative Examples 1 to 4, and the content of the solid electrolyte contained in the second layer relative to the content ratio of the solid electrolyte contained in the first layer. The ratio of the content ratio and the discharge capacity of the cell are shown.

  In FIG. 4, circles correspond to the data of Example 1 and Comparative Examples 1 to 3, and triangles correspond to the data of Comparative Example 4. Moreover, the curve shown with the wavy line is the quadratic approximate curve by the least square method fitted to the data of Example 1 and Comparative Examples 1-3.

  When the ratio of the content of the solid electrolyte contained in the second layer to the content of the solid electrolyte contained in the first layer is greater than 1 and less than or equal to 2.1, it is possible to obtain a higher discharge capacity than before. It was. Further, the discharge capacity of the cell produced in Comparative Example 4 was equivalent to the discharge capacity of the cell produced in Comparative Example 1.

DESCRIPTION OF SYMBOLS 1 Positive electrode layer 2 Electrolyte layer 3 Negative electrode layer 6 Positive electrode collector 7 Negative electrode collector 8 Gas reservoir part 9 Sealed container 10 Electrochemical cell 11 1st layer 12 2nd layer

Claims (8)

A metal-air battery comprising a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
The positive electrode layer includes a first layer disposed on the electrolyte layer side, and a second layer disposed on the opposite side of the electrolyte layer side,
Each of the first layer and the second layer includes a solid electrolyte and a carbon material;
The ratio of the content ratio of the solid electrolyte contained in the second layer to the content ratio of the solid electrolyte contained in the first layer is greater than 1 and 2.1 or less.
Metal-air battery. The metal-air battery according to claim 1, wherein the solid electrolyte contained in the first layer and the second layer is Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO).   The metal-air battery according to claim 1, wherein the electrolyte layer includes a separator.   The metal-air battery according to claim 1, wherein the negative electrode layer includes a material containing lithium.   The metal-air battery according to any one of claims 1 to 4, wherein the electrolyte layer includes a liquid electrolyte containing an ionic liquid.   The ionic liquid is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide (DEMETFSA), N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl). 6. The metal-air battery of claim 5, which is amide (PP13TFSA), or a combination thereof.   The metal-air battery according to claim 5 or 6, wherein the liquid electrolyte includes a lithium-containing metal salt.   The metal-air battery according to claim 7, wherein the lithium-containing metal salt is lithium bis (trifluoromethanesulfonyl) amide (LiTFSA).

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