WO2013046403A1 - 金属空気電池 - Google Patents
金属空気電池 Download PDFInfo
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- WO2013046403A1 WO2013046403A1 PCT/JP2011/072439 JP2011072439W WO2013046403A1 WO 2013046403 A1 WO2013046403 A1 WO 2013046403A1 JP 2011072439 W JP2011072439 W JP 2011072439W WO 2013046403 A1 WO2013046403 A1 WO 2013046403A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M12/00—Hybrid cells; Manufacture thereof
- H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M12/00—Hybrid cells; Manufacture thereof
- H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
- H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
- H01M12/065—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode with plate-like electrodes or stacks of plate-like electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a metal-air battery.
- a metal-air battery using oxygen as a positive electrode active material has advantages such as high energy density, easy size reduction and weight reduction. Therefore, it is attracting attention as a high-capacity battery that exceeds the lithium secondary battery that is currently widely used.
- metal-air batteries for example, lithium-air batteries, magnesium-air batteries, zinc-air batteries, and the like are known.
- the metal-air battery can be charged and discharged by performing an oxidation-reduction reaction of oxygen at the air electrode (positive electrode) and performing an oxidation-reduction reaction of a metal contained in the negative electrode at the negative electrode.
- the following charge / discharge reaction is considered to proceed.
- M represents a metal species.
- Negative electrode M ⁇ M + + e ⁇ Air electrode: 2M + + O 2 + 2e ⁇ ⁇ M 2 O 2 [When charging] Negative electrode: M + + e ⁇ ⁇ M Air electrode: M 2 O 2 ⁇ 2M + + O 2 + 2e ⁇
- the air battery includes, for example, an air electrode layer containing a conductive material and a binder, an air electrode current collector that collects the air electrode layer, and a negative electrode layer made of a negative electrode active material (metal, alloy, etc.) And a negative electrode current collector for collecting current of the negative electrode layer, and an electrolyte interposed between the air electrode layer and the negative electrode layer.
- an air electrode layer containing a conductive material and a binder
- an air electrode current collector that collects the air electrode layer
- a negative electrode layer made of a negative electrode active material (metal, alloy, etc.)
- a negative electrode current collector for collecting current of the negative electrode layer, and an electrolyte interposed between the air electrode layer and the negative electrode layer.
- Patent Documents 1 to 6 Specific metal-air batteries include those disclosed in Patent Documents 1 to 6, for example.
- Patent Document 1 includes a positive electrode layer, a negative electrode layer, and a non-aqueous electrolyte layer interposed between the positive electrode layer and the negative electrode layer, and the non-aqueous electrolyte layer impregnates and holds a non-aqueous electrolyte in a separator.
- a metal-air battery formed in the above is disclosed.
- Patent Document 5 includes a battery container having an air intake hole, an electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and the intake hole of the battery container.
- a metal-air battery having a gap holding member between a surface and the positive electrode is disclosed.
- Patent Document 6 discloses a porous current collector and a second electrode material formed inside the surface of the porous current collector and having a particle diameter smaller than the opening diameter of the porous current collector.
- a battery electrode comprising: an internal electrode layer containing; and an external electrode layer formed on the internal electrode layer and containing a first electrode material having a particle diameter larger than an opening diameter of the porous current collector. It is disclosed.
- metal-air batteries it is known that metal oxides such as LiO x are deposited on the air electrode during discharge.
- the present inventor has obtained the knowledge that the electrolytic solution impregnated in the air electrode is pushed out of the air electrode by the generation of the precipitate in the air electrode. It was also found that when the charged electrolyte does not return to the air electrode at the time of charging, a shortage of electrolyte occurs in the air electrode and the charge / discharge capacity decreases.
- the electrolytic solution pushed out from the air electrode at the time of discharge and taken into the separator is not the deposit generated at the time of discharge, but the liquid retention of the separator. Because it is strong, it is difficult to return to the air electrode during charging. Therefore, in the conventional metal-air battery, it is difficult to quickly supply the electrolytic solution to the air electrode during charging, and the charge / discharge capacity is reduced.
- the present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a metal capable of quickly and efficiently supplying an electrolytic solution to an air electrode and improving charge / discharge capacity. It is to provide an air battery.
- the metal-air battery of the present invention includes an air electrode layer, a negative electrode layer, and an electrolyte layer disposed between the air electrode layer and the negative electrode layer,
- the electrolyte layer has a separator having an insulating and porous structure, and an electrolytic solution impregnated in the separator,
- An electrolyte reserve layer having a porous structure having a pore size larger than that of the separator is provided between the separator and the air electrode layer.
- the pore diameter of the electrolyte reserve layer is preferably larger than the pore diameter of the air electrode layer. This is because the supply of the electrolyte from the electrolyte reserve layer to the air electrode layer is further promoted.
- specific pore diameters of the electrolyte reserve layer and the separator are not particularly limited, but as a preferable range, for example, the pore diameter of the electrolyte reserve layer is 1 to 50 ⁇ m, An embodiment in which the pore diameter is 0.02 to 1 ⁇ m can be mentioned.
- the porosity of the electrolyte reserve layer is preferably 50 to 90%. This is because a sufficient amount of electrolyte can be retained.
- the electrolyte reserve layer has conductivity. This is because the conductive electrolyte reserve layer can also function as a current collector for the air electrode layer, and the metal-air battery can be miniaturized.
- a specific example of the metal-air battery of the present invention is a lithium-air battery.
- the electrolyte solution can be supplied to the air electrode layer quickly and efficiently during subsequent charging. It is possible and the charge / discharge capacity can be improved. Therefore, according to the present invention, it is possible to provide a metal-air battery having a high energy density.
- the metal-air battery of the present invention includes an air electrode layer, a negative electrode layer, and an electrolyte layer disposed between the air electrode layer and the negative electrode layer,
- the electrolyte layer has a separator having an insulating and porous structure, and an electrolytic solution impregnated in the separator,
- An electrolyte reserve layer having a porous structure having a larger pore size than the separator is provided between the separator and the air electrode layer.
- FIG. 1 to 3 are schematic cross-sectional views showing examples of the metal-air battery of the present invention.
- the air electrode layer 1, the negative electrode layer 2, and the electrolyte layer 3 are laminated such that the electrolyte layer 3 is disposed between the air electrode layer 1 and the negative electrode layer 2.
- An electrolytic solution is interposed between the air electrode 1 and the negative electrode layer 2.
- An electrolyte reserve layer 4 is provided between the electrolyte layer 3 and the air electrode layer 1.
- the air electrode layer 1, the electrolyte solution reserve layer 4, the electrolyte layer 3, and the negative electrode layer 2 are laminated in this order, and are accommodated in a battery case that includes the air electrode can 5 and the negative electrode can 6.
- the air electrode can 5 and the negative electrode can 6 are fixed by a gasket 7.
- the air electrode layer 1 is an electrode reaction layer using oxygen as an active material, and includes a conductive material (for example, carbon black), a catalyst (for example, manganese dioxide), and a binder (for example, polytetrafluoroethylene and hexafluoropropylene). Copolymer).
- the air electrode layer 1 has a porous structure and is supplied with air (oxygen) taken in from the air holes 8 provided in the air electrode can 5.
- the negative electrode layer 2 contains a negative electrode active material (for example, Li metal) that can release and incorporate metal ions that are conductive ion species.
- a negative electrode active material for example, Li metal
- the electrolyte layer 3 has a separator made of an insulating porous material (for example, polypropylene nonwoven fabric) and an electrolyte solution (for example, a propylene carbonate solution of lithium salt) impregnated in the separator.
- an insulating porous material for example, polypropylene nonwoven fabric
- an electrolyte solution for example, a propylene carbonate solution of lithium salt
- the electrolyte reserve layer 4 is disposed between the separator constituting the electrolyte layer 3 and the air electrode layer 1 and has a porous structure having a pore diameter larger than that of the insulating porous body constituting the separator. (For example, carbon paper) and impregnated with an electrolytic solution.
- the present inventor has obtained the knowledge that in the air electrode layer of the metal-air battery, the electrolyte solution impregnated in the air electrode layer is pushed out of the air electrode layer due to the formation of precipitates during discharge. If the extruded electrolyte does not return to the air electrode layer, the electrolyte will be insufficient in the air electrode layer during charging, resulting in a problem of reduced charge / discharge capacity.
- the electrolyte solution pushed out from the air electrode layer and taken into the separator has a stronger liquid holding power and capillary force than the precipitates generated during discharge, so that during charging, Even if the precipitate is decomposed, it is difficult to return to the air electrode layer.
- the electrolyte solution reserve layer having the porous structure having the above pore diameter is disposed between the air electrode layer and the separator, thereby promoting the supply of the electrolyte solution to the air electrode layer. It was possible to suppress the shortage of electrolyte in the air electrode layer.
- a porous structure having a pore size larger than that of a separator has a smaller liquid retention and capillary force than a separator, and therefore, compared with a separator, an electrolyte solution incorporated therein easily moves to an air electrode layer. is there.
- the balance between the electrolyte supply capacity to the air electrode layer and the storage capacity of the electrolyte extruded from the air electrode layer is excellent, and the liquid retention between the separator and the air electrode layer And the supply of the electrolyte solution to the air electrode layer can be promoted by disposing a porous structure that exhibits an excellent function as a buffer layer for capillary force.
- the electrolyte reserve layer can efficiently improve the performance of the air electrode without hindering the downsizing of the metal-air battery.
- the metal-air battery refers to an oxygen redox reaction of the positive electrode active material in the air electrode layer, and a metal redox reaction in the negative electrode layer.
- the metal air battery include a lithium air battery, a sodium air battery, a potassium air battery, a magnesium air battery, a calcium air battery, a zinc air battery, and an aluminum air battery.
- a lithium-air battery has a strong effect of the present invention because a solid metal oxide (lithium oxide) is likely to be deposited in the air electrode layer during discharge and the amount of the electrolyte solution pushed out from the air electrode layer is large. It can be said.
- the air metal battery may be a primary battery or a secondary battery.
- the effect of the present invention such as improvement of charge / discharge capacity is strongly exhibited, which is preferable. .
- the pore diameters of the separator, the electrolyte reserve layer, and the air electrode layer mean the smallest diameter (bottleneck diameter) of the pores penetrating in the cross-sectional direction of these layers. It is possible to measure by the bubble point method.
- the gas pressure is applied while the porous sample is wet with liquid, the gas pressure is gradually increased, and the pore size distribution of the porous sample is obtained from the gas pressure at which the liquid in the pores is pushed out.
- This method can measure the diameter of the neck portion of the porous sample that governs the liquid permeability.
- the cross-sectional direction of a layer means a direction in which each layer and a layer (member) adjacent to the layer are stacked (see arrows in FIG. 1).
- the air electrode layer usually includes at least a conductive material and has a porous structure.
- the reaction between the supplied oxygen and metal ions generation or decomposition of metal oxide, metal hydroxide, etc.
- the voids in the porous structure are impregnated with an electrolytic solution and function as a metal ion conduction path and an oxygen diffusion path. Furthermore, it functions as a storage place for precipitates generated during discharge.
- the conductive material is not particularly limited as long as it has conductivity, and examples thereof include a conductive carbon material.
- the conductive carbon material is not particularly limited, but a carbon material having a high specific surface area is preferable from the viewpoint of the reaction field area and space in the air electrode layer.
- the conductive carbon material preferably has a specific surface area of 10 m 2 / g or more, particularly 100 m 2 / g or more, and more preferably 600 m 2 / g or more.
- Specific examples of the conductive carbon material having a high specific surface area include carbon black, activated carbon, carbon carbon fiber (for example, carbon nanotube, carbon nanofiber, etc.).
- the specific surface area of the conductive material can be measured by, for example, the BET method based on nitrogen adsorption measurement.
- the conductive carbon material may or may not have a porous structure, but from the viewpoint of securing a reaction field space, a conductive carbon material preferably has a porous structure, and particularly has a high pore of 1 cc / g or more. Those having a volume are preferred.
- Specific examples of the conductive carbon material having a high pore volume include carbon black, activated carbon, carbon carbon fiber (for example, carbon nanotube, carbon nanofiber, etc.) and the like.
- the pore volume of the conductive material can be measured by, for example, the BJH method based on nitrogen adsorption measurement.
- the content of the conductive material in the air electrode layer is preferably in the range of 10% by weight to 99% by weight, for example, depending on the density, specific surface area, and the like.
- the air electrode layer may contain an air electrode catalyst that promotes the reaction of oxygen in the air electrode layer.
- Such an air electrode catalyst may be supported on the conductive material.
- the air electrode catalyst is not particularly limited.
- phthalocyanine compounds such as cobalt phthalocyanine, manganese phthalocyanine, nickel phthalocyanine, tin phthalocyanine oxide, titanium phthalocyanine, and dilithium phthalocyanine; naphthocyanine compounds such as cobalt naphthocyanine; iron porphyrin Organic materials such as porphyrin-based compounds such as MnO 2 , CeO 2 , Co 3 O 4 , NiO, V 2 O 5 , Fe 2 O 3 , ZnO, CuO, LiMnO 2 , Li 2 MnO 3 , LiMn 2 O 4 , Li 4 Ti 5 O 12, Li 2 TiO 3, LiNi 1/3 Co 1/3 Mn 1/3 O 2, LiNiO 2, LiVO 3, Li 5 FeO 4, LiFeO 2, LiCr
- complex which combined two or more of the said material can also be used as an air electrode catalyst.
- the content of the air electrode catalyst in the air electrode layer is preferably in the range of 1% by weight to 90% by weight, for example.
- the air electrode layer preferably further contains a binder from the viewpoint of fixing the conductive material and the air electrode catalyst.
- a binder examples include polyvinylidene fluoride (PVdF), a copolymer of PVdF and hexafluoropropylene (HFP), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), and the like.
- the content of the binder in the air electrode layer is preferably in the range of 1% by weight to 40% by weight, for example.
- the thickness of the air electrode layer varies depending on the use of the metal-air battery, but is preferably in the range of 2 ⁇ m to 500 ⁇ m, particularly preferably in the range of 5 ⁇ m to 300 ⁇ m.
- the pore size of the porous structure of the air electrode layer is not particularly limited, but is preferably in the range of 0.02 to 1 ⁇ m, particularly preferably in the range of 0.05 to 0.2 ⁇ m.
- the air electrode layer may be provided with an air electrode current collector that collects the air electrode layer.
- the air electrode current collector may have a porous structure or a dense structure as long as it has a desired electronic conductivity, but it may diffuse air (oxygen). From the viewpoint of safety, those having a porous structure are preferred.
- the porous structure include a mesh structure in which constituent fibers are regularly arranged, a nonwoven fabric structure in which constituent fibers are randomly arranged, and a three-dimensional network structure having independent holes and connecting holes.
- the porosity of the current collector having a porous structure is not particularly limited, but is preferably in the range of 20 to 99%, for example.
- the arrangement position of the air electrode current collector is not particularly limited as long as it is electrically connected to the air electrode layer, and the air electrode current collector may be laminated on the surface of the air electrode layer opposite to the electrolyte reserve layer side. Alternatively, when an air electrode current collector having a porous structure is used, it may be disposed inside the air electrode layer.
- the air electrode current collector examples include metal materials such as stainless steel, nickel, aluminum, iron, titanium, and copper, carbon materials such as carbon fiber, carbon paper, and carbon cloth, and high electron conductive ceramics such as titanium nitride. Materials and the like.
- Preferable specific examples of the air electrode current collector include porous structures such as carbon paper, carbon cloth, and metal mesh, particularly porous carbon.
- the thickness of the air electrode current collector is not particularly limited, but for example, it is preferably in the range of 10 ⁇ m to 1000 ⁇ m, particularly in the range of 20 to 400 ⁇ m.
- the battery case of the metal air battery mentioned later may have the function as a collector of an air electrode.
- the electrolyte solution reserve layer mentioned later has electroconductivity, you may function this reserve layer as an air electrode electrical power collector.
- the electrolyte reserve layer functions as an air electrode current collector, it is possible to reduce the size of the metal-air battery, reduce the number of components, and the like.
- the method for producing the air electrode layer is not particularly limited.
- it can be formed by using an air electrode layer material in which a conductive material and other materials such as a binder are mixed.
- an air electrode layer material containing a solvent is applied to the surface of the porous body constituting the electrolyte reserve layer described later, and subjected to a drying treatment, a pressure treatment, a heat treatment, etc. as necessary.
- a laminate in which the air electrode layer and the electrolyte reserve layer are laminated can be produced.
- an air electrode layer material containing a solvent is rolled or coated on a base material and molded, and an air electrode layer is produced by performing drying treatment, pressure treatment, heat treatment, etc. as necessary. You can also.
- An air electrode layer containing an electrolytic solution or an electrolytic solution solvent can also be formed in advance using an electrolytic solution or a material for an air electrode layer to which an electrolytic solution solvent has been added.
- an electrolytic solution described later and a nonaqueous solvent used for the electrolytic solution can be used as the electrolytic solution and the electrolytic solution solvent.
- the air electrode layer thus prepared is appropriately laminated with the air electrode current collector and the porous body for the electrolyte solution reserve layer, and laminated with these members by applying pressure, heating, or the like as necessary. be able to.
- the solvent used for the air electrode layer material is not particularly limited as long as it has volatility, and can be appropriately selected. Specific examples include acetone, N, N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and the like. A solvent having a boiling point of 200 ° C. or lower is preferable because the air electrode layer material can be easily dried.
- the method for applying the air electrode layer material is not particularly limited, and general methods such as a doctor blade method, an ink jet method, and a spray method can be used.
- the electrolyte layer includes a separator having an insulating property and a porous structure, and an electrolytic solution impregnated in the separator.
- the separator is not particularly limited as long as it has an insulating property that can ensure the insulating property between the air electrode layer and the negative electrode layer, and a porous structure that can hold the electrolytic solution. Can be adopted.
- the material for the separator include insulating resins such as polyethylene and polypropylene, and glass.
- the porous structure of the separator include a mesh structure in which constituent fibers are regularly arranged, a nonwoven fabric structure in which constituent fibers are randomly arranged, and a three-dimensional network structure having independent holes and connecting holes.
- the pore diameter of the separator is not particularly limited, but from the viewpoint of liquid retention, for example, it is preferably 0.02 to 1 ⁇ m, and particularly preferably 0.05 to 0.2 ⁇ m.
- the thickness of the separator is not particularly limited, and may be about 10 to 500 ⁇ m, for example.
- the electrolytic solution impregnated in the separator is not particularly limited as long as it can conduct metal ions between the air electrode layer and the negative electrode layer, and may be a nonaqueous electrolytic solution containing a supporting electrolyte salt and a nonaqueous solvent, or a supporting electrolyte.
- An aqueous electrolyte containing a salt and an aqueous solvent may be used.
- a non-aqueous electrolyte precipitates are easily generated in the air electrode layer. Therefore, it can be said that the metal-air battery of the present invention exhibits a great effect when a non-aqueous electrolyte is used.
- the non-aqueous solvent is not particularly limited.
- PC propylene carbonate
- EC ethylene carbonate
- VMC dimethyl carbonate
- EMC ethyl methyl carbonate
- DEC diethyl carbonate
- methyl propyl carbonate methyl propyl carbonate.
- an ionic liquid can also be used as a non-aqueous solvent.
- the ionic liquid include N, N, N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) amide [abbreviation: TMPA-TFSA], N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl).
- the supporting electrolyte salt may be any one that has solubility in a nonaqueous solvent and expresses desired metal ion conductivity.
- a metal salt containing a metal ion to be conducted can be used.
- a lithium salt can be used as the supporting electrolyte salt.
- the lithium salt include inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiOH, LiCl, LiNO 3 , Li 2 SO 4 .
- LiBOB lithium bisoxalate borate
- LiTFSA LiN (CF 3 SO 2 ) 2
- LiBETA LiN (CF 3
- An organic lithium salt such as (SO 2 ) (C 4 F 9 SO 2 ) can also be used.
- the content of the supporting electrolyte salt with respect to the non-aqueous solvent is not particularly limited.
- the concentration of the lithium salt can be in the range of 0.5 mol / L to 3 mol / L, for example.
- the supporting electrolyte salt is not particularly limited as long as it has solubility in water and expresses desired ionic conductivity.
- a metal salt containing a metal ion to be conducted can be used.
- a lithium salt such as LiOH, LiCl, LiNO 3 , Li 2 SO 4 , or CH 3 COOLi can be used.
- the electrolytic solution may be gelled or may contain a solid electrolyte.
- a polymer such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), or polymethyl methacrylate (PMMA) is added to the non-aqueous electrolyte.
- PEO polyethylene oxide
- PAN polyacrylonitrile
- PVDF polyvinylidene fluoride
- PMMA polymethyl methacrylate
- the solid electrolyte is not particularly limited as long as it is appropriately selected according to the conductive metal ion.
- Li a Xb Y cP d O e (X is at least one selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, Sb, and Se)
- Y is at least one selected from the group consisting of Ti, Zr, Ge, In, Ga, Sn and Al, and a to e are 0.5 ⁇ a ⁇ 5.0, 0 ⁇ b ⁇ 2.98, 0.5 ⁇ c ⁇ 3.0, 0.02 ⁇ d ⁇ 3.0, 2.0 ⁇ b + d ⁇ 4.0, 3.0 ⁇ e ⁇ 12.0.
- NASICON type oxide Perovskite type oxide such as Li x La 1-x TiO 3 ; Li 4 XO 4 -Li 3 YO 4 (X is at least one selected from Si, Ge, and Ti; Y is at least one selected from P, as and V) as well as Li 3 DO 3 - i 3 YO 4 (D is B, Y is P, at least one selected from As and V) LISICON type oxides such as; Li 7 La 3 Zr 2 O 12 Li-La-Zr-O system such as Examples thereof include garnet-type oxides such as oxides.
- the electrolyte reserve layer is provided between the air electrode layer and the separator constituting the electrolyte layer. That is, the electrolyte reserve layer is in contact with both the air electrode layer and the separator.
- an air electrode, an electrolyte reserve layer and a separator are laminated in this order, and each of these layers is impregnated with the electrolyte.
- the electrolyte reserve layer has a porous structure, and the pore diameter thereof is larger than the pore diameter of the separator constituting the electrolyte layer.
- the pore diameter of the electrolyte reserve layer may be larger than the pore diameter of the separator.
- the electrolyte solution taken into the electrolyte reserve layer can be supplied to the air electrode layer more efficiently, it is preferably larger than the pore diameter of the air electrode layer.
- the specific pore size of the electrolyte reserve layer is not particularly limited, but from the viewpoint of capillary force as a driving force for supplying the electrolyte to the air electrode layer, for example, it is preferably 1 to 50 ⁇ m, particularly 10 to 40 ⁇ m. Preferably there is.
- the porous structure of the electrolyte reserve layer is not particularly limited. For example, a mesh structure in which constituent fibers are regularly arranged, a nonwoven structure in which constituent fibers are randomly arranged, a three-dimensional network structure having independent holes and connecting holes, and the like. Is mentioned.
- the material constituting the porous structure of the electrolyte solution reserve layer is not particularly limited, and an insulating material such as polypropylene can be used, but since it can also function as a current collector for the air electrode layer, it has conductivity.
- the conductive material constituting the electrolyte reserve layer include metal materials such as stainless steel, nickel, aluminum, iron, titanium, and copper, carbon materials such as carbon fiber, carbon paper, and carbon cloth, and high electrons such as titanium nitride.
- Examples thereof include conductive ceramic materials, and among them, a carbon porous body containing carbon fibers such as carbon paper and carbon cloth is preferable.
- the porosity of the electrolytic solution reserve layer is not particularly limited, but is preferably 50 to 90%, for example, and particularly preferably 70 to 90% so that a sufficient amount of electrolytic solution can be retained.
- the porosity of the electrolyte reserve layer can be measured, for example, by a mercury intrusion method.
- the thickness of the electrolytic solution reserve layer is not particularly limited, and may be about 2 to 500 ⁇ m, for example.
- the negative electrode layer contains a negative electrode active material capable of releasing and capturing metal ions (conducting ions).
- the negative electrode layer may be provided with a negative electrode current collector that collects current from the negative electrode layer.
- the negative electrode active material is not particularly limited as long as it is capable of releasing and taking up conductive ion species, typically metal ions.
- a carbon material can also be used as the negative electrode active material.
- As the negative electrode active material a single metal or an alloy is preferable, and a single metal is particularly preferable.
- Examples of the single metal include lithium, sodium, potassium, magnesium, calcium, aluminum, zinc, and iron.
- Examples of the alloy include alloys containing at least one of these single metals. More specifically, examples of the negative electrode active material of the lithium-air battery include metal lithium; lithium alloys such as lithium aluminum alloy, lithium tin alloy, lithium lead alloy, and lithium silicon alloy; tin oxide, silicon oxide, and lithium titanium.
- Metal oxides such as oxides, niobium oxides and tungsten oxides; metal sulfides such as tin sulfides and titanium sulfides; metal nitrides such as lithium cobalt nitrides, lithium iron nitrides and lithium manganese nitrides; and Examples thereof include carbon materials such as graphite, among which metal lithium and carbon materials are preferable, and metal lithium is more preferable from the viewpoint of increasing capacity.
- the negative electrode layer may contain at least the negative electrode active material, but may contain a binder for immobilizing the negative electrode active material as necessary.
- the negative electrode layer can be configured to contain only the negative electrode active material, but when a powdered negative electrode active material is used, the negative electrode layer Can be made into a form containing a negative electrode active material and a binder.
- the negative electrode layer may contain a conductive material. About the kind, usage-amount, etc. of a binder and an electroconductive material, it can be the same as that of the air electrode layer mentioned above.
- the material of the negative electrode current collector is not particularly limited as long as it has conductivity.
- copper, stainless steel, nickel and the like can be mentioned, among which stainless steel or nickel is preferable.
- the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh shape. Further, the battery case may have a function as a negative electrode current collector.
- the manufacturing method of the negative electrode layer and the negative electrode current collector is not particularly limited.
- a foil-like negative electrode active material and a negative electrode current collector can be overlaid and pressed to produce a negative electrode in which a negative electrode layer and a negative electrode current collector are stacked.
- a negative electrode layer material containing a negative electrode active material, a binder, and the like is prepared, and the negative electrode layer and the negative electrode current collector are coated and dried on a base material (for example, a negative electrode current collector). Can be produced.
- the metal-air battery of the present invention may have other components other than the air electrode layer, the electrolyte reserve layer, the electrolyte layer, and the negative electrode layer as described above.
- the air electrode layer 1 is provided on the opposite side of the electrolyte reserve layer 4 and adjacent to the air electrode layer 1.
- An air reserve layer 9 is provided.
- the air reserve layer 9 has a structure capable of storing oxygen supplied to the air electrode layer, and can be formed of, for example, a porous body.
- the porous body constituting the air reserve layer may have conductivity or may have insulating properties.
- porous body constituting the air reserve layer examples include porous bodies such as polyethylene, polypropylene, polytetrafluoroethylene, carbon paper, and carbon cloth.
- the air reserve layer preferably has a thickness of about 2 to 500 ⁇ m, for example.
- the negative electrode protective layer 11 can also be provided between the negative electrode layer 2 and the electrolyte layer 3 like the metal air battery 101 of FIG.
- the negative electrode protective layer 11 has a reservoir structure (gap) capable of storing an electrolytic solution. By providing such a negative electrode protective layer 11, the increase / decrease of the electrolytic solution in the entire battery can be reduced.
- the metal-air battery of the present invention usually has a battery case that houses an air electrode layer, a negative electrode, and an electrolyte layer.
- the shape of the battery case is not particularly limited, and specific examples include a coin type, a flat plate type, a cylindrical type, and a laminate type.
- the battery case may be an open air type or a sealed type.
- the battery case that is open to the atmosphere has a structure in which at least the air electrode layer can sufficiently contact the atmosphere.
- the air intake hole 8 may be provided with an oxygen permeable membrane 10 capable of selectively transmitting oxygen, like the metal air battery 101 in FIG.
- the oxygen permeable membrane 10 can prevent water (water vapor) and carbon dioxide in the air from being taken into the battery case.
- the oxygen permeable film include a polysiloxane film.
- the air intake hole may be provided with a water repellent film such as a polytetrafluoroethylene film.
- the oxygen permeable film may also have a function as a water repellent film.
- a sealed battery case can be provided with an introduction pipe and an exhaust pipe for oxygen (air), which is a positive electrode active material.
- the oxygen concentration supplied to the metal-air battery is preferably high and particularly preferably pure oxygen.
- a metal-air battery takes a structure (for example, a laminated structure or a wound structure) in which a laminated body in which an air electrode layer, an electrolyte solution reserve layer, an electrolyte layer, and a negative electrode layer are arranged in order is repeatedly stacked.
- a separator between the air electrode and the negative electrode belonging to different laminates.
- porous films such as polyethylene and polypropylene
- nonwoven fabrics such as a resin nonwoven fabric and a glass fiber nonwoven fabric.
- Each of the air electrode current collector and the negative electrode current collector can be provided with a terminal serving as a connection portion with the outside.
- the method for producing the metal-air battery of the present invention is not particularly limited, and a general method can be adopted.
- Example 1 A lithium air battery having the form shown in FIG. 2 was produced as follows. However, in the following lithium air battery, the negative electrode current collector was laminated on the outer surface side of the negative electrode layer. A polytetrafluoroethylene film was prepared as an air reserve layer.
- the obtained coated product was cut to obtain a laminate of an air electrode layer and an electrolyte solution reserve layer (pore diameter: 30 ⁇ m).
- pore diameter 30 ⁇ m.
- LiTFSA lithium bistrifluoromethanesulfonylamide, manufactured by Kishida Chemical
- lithium salt lithium salt
- propylene carbonate manufactured by Kishida Chemical
- a PEEK ring for forming a negative electrode protective layer (space) was prepared.
- SUS304 foil manufactured by Nilaco
- metal Li made by Honjo Metal
- a battery case having an oxygen uptake hole on the air electrode side was prepared.
- An oxygen permeable film (polytetrafluoroethylene film) was disposed inside the surface of the battery case where the oxygen uptake holes were provided.
- the air reserve layer, the air electrode layer, the electrolyte solution reserve layer, the separator, the negative electrode protective layer, the negative electrode layer, and the negative electrode current collector are laminated in order from the oxygen intake hole side (oxygen permeable membrane side).
- Each member was accommodated.
- the electrolyte solution reserve layer, the separator, and the negative electrode protective layer were filled with a non-aqueous electrolyte solution to produce a lithium-air battery.
- Example 1 A lithium-air battery was produced in the same manner as in Example 1 except that the air electrode layer was produced as follows and the electrolyte reserve layer was not provided. That is, the air electrode layer was prepared by coating and drying the same air electrode layer slurry as in Example 1 on a glass substrate, and peeling and cutting the obtained coated material from the glass substrate.
- Example 2 A lithium air battery having the configuration shown in FIG. 3 was produced as follows. However, in the following lithium air battery, the negative electrode current collector was laminated on the outer surface side of the negative electrode layer. A polytetrafluoroethylene film was prepared as an air reserve layer.
- Ketjen Black manufactured by Ketjen Black International, ECP600JD
- conductive material conductive material
- PVdF-HFP copolymer manufactured by Alkema, Kynar 2801
- PP13TFSA N-methyl-N-propylpiperidine Nitrobistrifluoromethanesulfonylamide (manufactured by Kanto Chemical) (non-aqueous solvent) was mixed and stirred so that the weight ratio was 25:15:60 to prepare an air electrode layer slurry.
- the air electrode layer slurry was coated on a carbon paper (manufactured by Toray, TGP-H-30, pore size 30 ⁇ m, porosity 78%) (conductive porous body) by a doctor blade method and dried.
- the obtained coated product was cut to obtain a laminate of an air electrode layer and an electrolyte solution reserve layer (pore diameter: 30 ⁇ m).
- pore diameter of the air electrode layer formed in the same manner as described above was measured by palm porometry, it was 120 nm.
- SUS304 foil manufactured by Niraco
- current collector was attached to metal Li (manufactured by Honjo Metal) (negative electrode active material) to obtain a negative electrode in which a negative electrode layer and a negative electrode current collector were laminated.
- a battery case having an oxygen uptake hole on the air electrode side was prepared.
- An oxygen permeable film (polytetrafluoroethylene film) was disposed inside the surface of the battery case where the oxygen uptake holes were provided.
- Each member is housed in the battery case so that an air reserve layer, an air electrode layer, an electrolyte solution reserve layer, a separator, a negative electrode layer, and a negative electrode current collector are stacked in this order from the oxygen intake hole side (oxygen permeable membrane side). did.
- the electrolyte reserve layer and the separator were filled with a non-aqueous electrolyte solution to produce a lithium air battery.
- Example 2 A lithium-air battery was produced in the same manner as in Example 2 except that the air electrode layer was produced as follows and the electrolyte reserve layer was not provided. That is, the air electrode layer was prepared by coating and drying the same air electrode layer slurry as in Example 2 on a glass substrate, and peeling and cutting the obtained coated material from the glass substrate.
- Example 1 and Comparative Example 1 The lithium air batteries of the above Examples and Comparative Examples were evaluated as follows.
- Example 1 and Comparative Example 1 First, the gas replacement operation of depressurizing the inside of the battery case at 60 kPa and then sealing (purging) argon gas was repeated 15 times to seal the argon gas in the battery case. Thereafter, the inside of the battery case was sufficiently replaced with oxygen gas (pure oxygen, manufactured by Taiyo Nippon Sanso, 99.9%). Subsequently, the lithium air battery was allowed to stand at 25 ° C. for 3 hours. After standing, constant current charge / discharge measurement was performed at 0.02 mA / cm 2 and 25 ° C. under an oxygen atmosphere (pure oxygen, manufactured by Taiyo Nippon Sanso, 99.9%), and the unit weight of the air electrode layer The initial discharge capacity of was measured. The final discharge voltage was 2.0V. The results are shown in Table 1 and FIG.
- Example 2 and Comparative Example 2 Except for changing the static temperature and the constant current charge / discharge measurement temperature to 60 ° C. and the current density of the constant current charge / discharge measurement to 0.05 mA / cm 2 , the same as in Example 1 and Comparative Example 1, Evaluation was performed. The results are shown in Table 2 and FIG.
- the metal-air batteries of Example 1 and Example 2 in which an electrolyte reserve layer having a porous structure having a larger pore size than the separator was provided adjacent to the air electrode layer are Comparative Example 1.
- Comparative Example 2 it was confirmed that the discharge capacity was increased. This is presumably because the formation of the electrolyte reserve layer promoted the supply of the electrolyte to the air electrode layer.
- the metal-air battery of each example performed before the constant current charge / discharge measurement was compared with the metal-air battery of each comparative example during the gas replacement operation and standing. It is considered that the increase in the initial discharge capacity occurred because the electrolyte solution was effectively transferred from the air electrode layer to the air electrode layer.
- the electrolyte solution in the separator or the electrolyte reserve layer moves into the air electrode layer by being left still.
- the electrolyte solution in the air electrode layer moves, for example, moves into the electrolyte reserve layer or the separator. That is, during the gas replacement operation and the stationary treatment, in the metal-air batteries of Examples 1 and 2 compared to Comparative Examples 1 and 2, the movement of the electrolyte solution to the air electrode layer is promoted, and the air electrode It is considered that the initial discharge capacity was increased because the state of impregnation of the electrolyte in the layer was improved.
- Example 1 and Example 2 since the hole diameter of the electrolyte reserve layer is larger than the hole diameter of the air electrode layer, the supply of the electrolyte from the electrolyte reserve layer to the air electrode layer is more effectively promoted. It is thought.
- Example 2 and Comparative Example 2 compared to Example 1 and Comparative Example 1, constant current charge / discharge measurement was performed under high temperature and high current density conditions. Under high temperature and high current density, Example 2 has an effect superior to that of Comparative Example 2 despite the fact that the electrolyte solution exhibits low viscosity and the load is high because of the high load. Indicated.
Abstract
Description
金属空気電池は、空気極(正極)において酸素の酸化還元反応が行われ、負極において負極に含まれる金属の酸化還元反応が行われることで、充放電が可能である。例えば、伝導イオンが一価の金属イオンである金属空気電池(二次電池)では、以下のような充放電反応が進むと考えられる。尚、下記式においてMは金属種を示す。
負極 : M → M+ + e-
空気極 : 2M+ + O2 + 2e- → M2O2
[充電時]
負極 : M+ + e- → M
空気極 : M2O2 → 2M+ + O2 + 2e-
特許文献1には、正極層、負極層、及び該正極層と負極層との間に介在する非水電解質層を有し、非水電解質層が非水電解液をセパレータに含浸・保持することで形成された金属空気電池が開示されている。
また、特許文献5には、空気取り入れ孔を有する電池容器と、正極、負極、及び正極と負極との間に配置されたセパレータを含む電極群と、前記電池容器の前記取り入れ孔が形成された面と前記正極との間に空隙保持部材と、を有する金属空気電池が開示されている。
また、特許文献6には、多孔質集電体と、前記多孔質集電体の表面内部に形成され、前記多孔質集電体の開口径よりも小さな粒径を有する第2の電極材料を含有する内部電極層と、前記内部電極層上に形成され、前記多孔質集電体の開口径よりも大きな粒径を有する第1の電極材料を含有する外部電極層と、を有する電池電極が開示されている。
しかしながら、特許文献1に記載されているような従来の金属空気電池では、放電時に空気極から押し出され、セパレータ内に取り込まれた電解液は、放電時に生成した析出物よりもむしろセパレータの保液力が強いゆえに、充電時に空気極へ戻りにくい。従って、従来の金属空気電池では、充電時の空気極への速やかな電解液供給が難しく、充放電容量の低下が生じてしまう。
前記電解質層が、絶縁性及び多孔質構造を有するセパレータと、該セパレータ内に含浸された電解液とを有し、
前記セパレータと前記空気極層との間に、前記セパレータよりも孔径が大きい多孔質構造を有する電解液リザーブ層を備えることを特徴とする。
本発明の金属空気電池は、上記のような電解液リザーブ層により、空気極層への電解液供給が促進されるため、高い充放電容量を得ることができる。
前記電解質層が、絶縁性及び多孔質構造を有するセパレータと、該セパレータ内に含浸された電解液とを有し、
前記セパレータと前記空気極層との間に、前記セパレータよりも孔径が大きい多孔質構造を有する電解液リザーブ層を備えることを特徴とするものである。
図1の金属空気電池100において、空気極層1、負極層2、及び電解質層3は、空気極層1と負極層2との間に電解質層3が配置されるように積層されており、電解液が、空気極1と負極層2との間に介在している。電解質層3と空気極層1との間には、電解液リザーブ層4が設けられている。これら空気極層1、電解液リザーブ層4、電解質層3及び負極層2は、この順序で積層され、空気極缶5及び負極缶6で構成される電池ケース内に収容されている。空気極缶5及び負極缶6は、ガスケット7により固定されている。
空気極層1は、多孔質構造を有し、空気極缶5に設けられた空気孔8から取り込まれる空気(酸素)が供給される。
そこで、本発明では、上記のような孔径を有する多孔質構造を有する電解液リザーブ層を、空気極層とセパレータとの間に配置することによって、空気極層への電解液の供給を促進し、空気極層での電解液不足の抑制を可能にした。セパレータよりも孔径が大きい多孔質構造体は、セパレータよりもその保液力及び毛管力が小さいために、セパレータと比較してその内部に取り込まれた電解液が空気極層へ移動しやすいからである。
一方、空気極層とセパレータとの間に、電解液を保持可能な空間(空隙)を設けた場合、類似の効果を奏するが、電池が大型化してしまい、体積ロスにつながるという問題が生じる。或いは、空間に溜まった電解液を空気極層が吸い続けるフラッティング現象にもつながりかねない。
しかも、上記電解液リザーブ層は、金属空気電池の小型化を阻むことなく、効率良く空気極性能の向上が実現可能である。
尚、本発明において、金属空気電池とは、空気極層において、正極活物質である酸素の酸化還元反応が行われ、負極層において、金属の酸化還元反応が行われ、空気極層と負極層との間に介在する電解質によって金属イオンが伝導される電池を指す。金属空気電池の種類としては、例えば、リチウム空気電池、ナトリウム空気電池、カリウム空気電池、マグネシウム空気電池、カルシウム空気電池、亜鉛空気電池、アルミニウム空気電池等を挙げることができる。特にリチウム空気電池は、放電時、空気極層において固体金属酸化物(リチウム酸化物)が析出しやすく、空気極層から押し出される電解液の量が多いことから、本発明の効果が強く発揮されるといえる。
また、本発明において、空気金属電池は、一次電池であっても二次電池であってもよいが、二次電池の場合、充放電容量向上等の本発明の効果が強く発揮されるため好ましい。
空気極層は、通常、少なくとも導電性材料を含み、多孔質構造を有するものである。空気極層では、導電性材料の表面において、供給された酸素と金属イオンとの反応(金属酸化物や金属水酸化物等の生成、分解など)が起こる。多孔質構造の空隙には、電解液が含浸され、金属イオンの伝導パスとして、また、酸素の拡散パスとして機能する。さらには、放電時に生成する析出物の格納場としても機能する。
導電性炭素材料は特に限定されないが、空気極層における反応場の面積や空間の観点から、高比表面積を有する炭素材料が好ましい。具体的には、導電性炭素材料は10m2/g以上、特に100m2/g以上、さらに600m2/g以上の比表面積を有することが好ましい。高比表面積を有する導電性炭素材料の具体例として、カーボンブラック、活性炭、カーボン炭素繊維(例えばカーボンナノチューブ、カーボンナノファイバー等)等を挙げることができる。ここで、導電性材料の比表面積は、たとえば、窒素吸着測定によるBET法によって測定することができる。
導電性炭素材料は、多孔質構造を有するものであってもなくてもよいが、反応場の空間を確保する観点から、多孔質構造を有するものが好ましく、特に1cc/g以上の高い細孔容積を有するものが好ましい。高い細孔容積を有する導電性炭素材料の具体例としては、カーボンブラック、活性炭、カーボン炭素繊維(例えばカーボンナノチューブ、カーボンナノファイバー等)等を挙げることができる。ここで、導電性材料の細孔容積は、たとえば窒素吸着測定によるBJH法によって測定することができる。
空気極層における導電性材料の含有量は、その密度や比表面積等にもよるが、例えば、10重量%~99重量%の範囲であることが好ましい。
空気極触媒としては、特に限定されず、例えば、コバルトフタロシアニン、マンガンフタロシアニン、ニッケルフタロシアニン、スズフタロシアニンオキサイド、チタンフタロシアニン、ジリチウムフタロシアニン等のフタロシアニン系化合物;コバルトナフトシアニン等のナフトシアニン系化合物;鉄ポルフィリン等のポリフィリン系化合物等の有機材料や、MnO2、CeO2、Co3O4、NiO、V2O5、Fe2O3、ZnO、CuO、LiMnO2、Li2MnO3、LiMn2O4、Li4Ti5O12、Li2TiO3、LiNi1/3Co1/3Mn1/3O2、LiNiO2、LiVO3、Li5FeO4、LiFeO2、LiCrO2、LiCoO2、LiCuO2、LiZnO2、Li2MoO4、LiNbO3、LiTaO3、Li2WO4、Li2ZrO3、NaMnO2、CaMnO3、CaFeO3、MgTiO3、KMnO2等の金属酸化物;Au、Pt、Ag等の貴金属等の無機材料等が挙げられる。また、上記材料の複数を組み合わせた複合体を空気極触媒として用いることもできる。
空気極層における空気極触媒の含有量は、例えば、1重量%~90重量%の範囲であることが好ましい。
結着材としては、例えば、ポリフッ化ビニリデン(PVdF)、PVdFとヘキサフルオロプロピレン(HFP)の共重合体、ポリテトラフルオロエチレン(PTFE)、スチレンブタジエンゴム(SBR)等が挙げられる。
空気極層における結着材の含有量は、例えば、1重量%~40重量%の範囲であることが好ましい。
空気極層の多孔質構造の孔径は特に限定されないが、例えば、0.02~1μmの範囲内、特に0.05~0.2μmの範囲内であることが好ましい。
空気極集電体としては、所望の電子伝導性を有していれば、多孔質構造を有するものであっても、或いは緻密構造を有するものであってもよいが、空気(酸素)の拡散性の観点から、多孔質構造を有するものが好ましい。多孔質構造としては、例えば、構成繊維が規則正しく配列されたメッシュ構造、構成繊維がランダムに配列された不織布構造、独立孔や連結孔を有する三次元網目構造等が挙げられる。多孔質構造を有する集電体の空隙率は特に限定されないが、例えば、20~99%の範囲であることが好ましい。
空気極集電体は、空気極層と電気的に接続されていればその配置位置は特に限定されず、空気極層の電解液リザーブ層側とは反対側の面に積層されてもよいし、或いは、多孔質構造を有する空気極集電体を用いる場合には、空気極層の内部に配置されてもよい。
空気極集電体の厚さは特に限定されないが、例えば、10μm~1000μmの範囲内、特に20~400μmの範囲内であることが好ましい。
尚、後述する金属空気電池の電池ケースが空気極の集電体としての機能を兼ね備えていてもよい。また、後述する電解液リザーブ層が導電性を有する場合には、該リザーブ層を空気極集電体として機能させてもよい。電解液リザーブ層を空気極集電体として機能させる場合、金属空気電池の小型化、構成部材の削減等が可能である。
このようにして作製した空気極層は、適宜、空気極集電体や電解液リザーブ層用多孔質体と重ね合わせ、必要に応じて加圧や加熱等を行うことで、これら部材と積層することができる。
空気極層用材料を塗布する方法は特に限定されず、ドクターブレード法、インクジェット法、スプレー法等の一般的な方法を用いることができる。
電解質層は、絶縁性及び多孔質構造を有するセパレータと、該セパレータ内に含浸された電解液とを有する。
セパレータの孔径は特に限定されないが、保液性の観点から、例えば、0.02~1μmであることが好ましく、特に0.05~0.2μmであることが好ましい。
セパレータの厚さは特に限定されず、例えば、10~500μm程度でよい。
非水系電解液において、非水溶媒に対する支持電解質塩の含有量は、特に限定されないが、例えば、リチウム塩の濃度は、例えば0.5mol/L~3mol/Lの範囲内とすることができる。
例えば、非水電解液のゲル化方法としては、非水系電解液に、ポリエチレンオキシド(PEO)、ポリアクリルニトリル(PAN)、ポリビニリデンフルオライド(PVDF)またはポリメチルメタクリレート(PMMA)等のポリマーを添加する方法が挙げられる。
また、固体電解質は、伝導金属イオンに応じて適宜選択すればよく特に限定されない。例えば、リチウム空気電池の場合、LiaXbYcPdOe(XはB、Al、Ga、In、C、Si、Ge、Sn、Sb及びSeよりなる群から選択される少なくとも1種であり、YはTi、Zr、Ge、In、Ga、Sn及びAlよりなる群から選択される少なくとも1種であり、a~eは、0.5<a<5.0、0≦b<2.98、0.5≦c<3.0、0.02<d≦3.0、2.0<b+d<4.0、3.0<e≦12.0の関係を満たす)で表されるNASICON型酸化物;LixLa1-xTiO3等のペロブスカイト型酸化物;Li4XO4-Li3YO4(XはSi、Ge,及びTiから選ばれる少なくとも1種であり、YはP、As及びVから選ばれる少なくとも1種である)並びにLi3DO3-Li3YO4(DはB、YはP、As及びVから選ばれる少なくとも1種である)等のLISICON型酸化物;Li7La3Zr2O12等のLi-La-Zr-O系酸化物等のガーネット型酸化物等が挙げられる。
電解液リザーブ層は、空気極層と電解質層を構成するセパレータとの間に設けられる。すなわち、電解液リザーブ層は、空気極層及びセパレータの両方に接触する。典型的には、空気極、電解液リザーブ層及びセパレータが、この順序で積層され、これらの各層は電解液を含浸する。
電解液リザーブ層は多孔質構造を有し、その孔径は、電解質層を構成するセパレータの孔径よりも大きい。電解液リザーブ層の孔径はセパレータの孔径よりも大きければよいが、電解液リザーブ層に取り込まれた電解液をより効率良く空気極層へ供給できることから、空気極層の孔径よりも大きいことが好ましい。
電解液リザーブ層の具体的な孔径は特に限定されないが、空気極層へ電解液を供給する駆動力としての毛管力の観点から、例えば、1~50μmであることが好ましく、特に10~40μmであることが好ましい。
電解液リザーブ層の多孔質構造は、特に限定されず、例えば、構成繊維が規則正しく配列されたメッシュ構造、構成繊維がランダムに配列された不織布構造、独立孔や連結孔を有する三次元網目構造等が挙げられる。
電解液リザーブ層の厚さは特に限定されず、例えば、2~500μm程度でよい。
負極層は、金属イオン(伝導イオン)を放出・取り込み可能な負極活物質を含有する。負極層には、負極層の集電を行う負極集電体が設けられてもよい。
負極活物質は、伝導イオン種、典型的には金属イオンの放出・取り込みが可能なものであれば特に限定されず、例えば、伝導イオン種である金属イオンを含有する単体金属、合金、金属酸化物、金属硫化物、及び金属窒化物等が挙げられる。また、炭素材料も負極活物質として用いることができる。負極活物質としては、単体金属又は合金が好ましく、特に単体金属が好ましい。単体金属としては、例えば、リチウム、ナトリウム、カリウム、マグネシウム、カルシウム、アルミニウム、亜鉛及び鉄等が挙げられ、合金としては、これら単体金属を少なくとも1種含む合金が挙げられる。
より具体的には、リチウム空気電池の負極活物質としては、例えば金属リチウム;リチウムアルミニウム合金、リチウムスズ合金、リチウム鉛合金、リチウムケイ素合金等のリチウム合金;スズ酸化物、ケイ素酸化物、リチウムチタン酸化物、ニオブ酸化物、タングステン酸化物等の金属酸化物;スズ硫化物、チタン硫化物等の金属硫化物;リチウムコバルト窒化物、リチウム鉄窒化物、リチウムマンガン窒化物等の金属窒化物;並びにグラファイト等の炭素材料等を挙げることができ、中でも金属リチウム及び炭素材料が好ましく、高容量化の観点から金属リチウムがより好ましい。
本発明の金属空気電池は、上記したような空気極層、電解液リザーブ層、電解質層、及び負極層以外のその他構成部材を有していてもよい。
例えば、図2に示す金属空気電池101及び図3に示す金属空気電池102において、空気極層1には、電解液リザーブ層4とは反対側に、空気極層1に隣接して設けられた空気リザーブ層9が設けられている。空気リザーブ層9は、空気極層へ供給される酸素を貯留しておくことが可能な構造を有しており、例えば、多孔質体により構成することができる。空気リザーブ層を構成する多孔質体は、導電性を有していてもよいし、又は、絶縁性を有していてもよい。空気リザーブ層を構成する多孔質体としては、例えば、ポリエチレン、ポリプロピレン、ポリテトラフルオロエチレン、カーボンペーパー、カーボンクロス等の多孔質体が挙げられる。空気リザーブ層は、例えば、2~500μm程度の厚さを有していることが好ましい。
また、図2の金属空気電池101のように、負極層2と電解質層3との間に、負極保護層11を設けることもできる。負極保護層11は、電解液を貯留しておくことが可能な液だめ構造(間隙)を有するものである。このような負極保護層11を設けることで、電解液の電池全体での増減を緩和することができる。
大気開放型の電池ケースは、少なくとも空気極層が十分に大気を接触可能な構造を有する。例えば、図1~図3の金属空気電池100、101、及び102のように、空気極層1に連通する空気取り込み孔8を有する構造が挙げられる。空気取り込み孔8には、図2の金属空気電池101及び図3の金属空気電池102のように、酸素を選択的に透過可能な酸素透過膜10を設けてもよい。酸素透過膜10は、空気中の水(水蒸気)や二酸化炭素が電池ケース内に取り込まれるのを阻止できることが好ましい。具体的な酸素透過膜としては、例えば、ポリシロキサン系膜等が挙げられる。また、空気取り込み孔には、ポリテトラフルオロエチレン膜等の撥水膜を設けてもよい。酸素透過膜が撥水膜としても機能を兼ね備えていてもよい。
一方、密閉型の電池ケースは、正極活物質である酸素(空気)の導入管及び排気管を設けることができる。
金属空気電池に供給される酸素濃度は高いことが好ましく、純酸素であることが特に好ましい。
本発明の金属空気電池の製造方法は特に限定されず、一般的な方法を採用することができる。
(実施例1)
以下のようにして図2に示す形態のリチウム空気電池を作製した。ただし、下記リチウム空気電池では、負極層の外面側に負極集電体を積層させた。
空気リザーブ層として、ポリテトラフルオロエチレン膜を用意した。
カーボンブラック(TIMCAL製、SuperP)(導電性材料)と、MnO2(三井金属鉱山製)(触媒)と、PVdF-HFP共重合体(Alkema製、Kynar2801)(結着材)とを、重量比で、25:42:33となるように、アセトン溶媒中、混合及び攪拌し、空気極層スラリーを調製した。空気極層スラリーを、カーボンペーパー(東レ製、TGP-H-90、孔径30μm、空隙率80%)(導電性多孔質体)上に、ドクターブレード法により塗工し、乾燥させた。得られた塗工物を切断し、空気極層と電解液リザーブ層(孔径30μm)との積層体を得た。
上記同様にして形成した空気極層の孔径をパームポロメトリーにより測定したところ、120nmであった。
また、セパレータとして、ポリプロピレン製不織布(孔径50nm)を用意した。
金属Li(本城金属製)(負極活物質)に、SUS304製箔(ニラコ製)(集電体)を貼付し、負極層と負極集電体とが積層した負極を得た。
電池ケース内に、酸素取り込み孔側(酸素透過膜側)から順に、空気リザーブ層、空気極層、電解液リザーブ層、セパレータ、負極保護層、負極層及び負極集電体が積層するように、各部材を収容した。電解液リザーブ層、セパレータ及び負極保護層に、非水系電解液を充填させ、リチウム空気電池を作製した。
空気極層を以下のようにして作製し、電解液リザーブ層を設けなかったこと以外は、実施例1と同様にしてリチウム空気電池を作製した。すなわち、空気極層は、実施例1と同様の空気極層スラリーをガラス基板上に塗工及び乾燥させ、得られた塗工物をガラス基板から剥離及び切断することによって作製した。
以下のようにして図3に示す形態のリチウム空気電池を作製した。ただし、下記リチウム空気電池では、負極層の外面側に負極集電体を積層させた。
空気リザーブ層として、ポリテトラフルオロエチレン膜を用意した。
ケッチェンブラック(ケッチェンブラック・インターナショナル製、ECP600JD)(導電性材料)と、PVdF-HFP共重合体(Alkema製、Kynar2801)(結着材)と、PP13TFSA(N-メチル-N-プロピルピペリジニウムビストリフルオロメタンスルフォニルアミド、関東化学製)(非水系溶媒)を、重量比で、25:15:60となるように、混合及び攪拌し、空気極層スラリーを調製した。空気極層スラリーを、カーボンペーパー(東レ製、TGP-H-30、孔径30μm、空隙率78%)(導電性多孔質体)上に、ドクターブレード法により塗工し、乾燥させた。得られた塗工物を切断し、空気極層と電解液リザーブ層(孔径30μm)との積層体を得た。
上記同様にして形成した空気極層の孔径をパームポロメトリーにより測定したところ、120nmであった。
また、セパレータとして、ポリプロピレン製不織布(孔径50nm)を用意した。
電池ケース内に、酸素取り込み孔側(酸素透過膜側)から順に、空気リザーブ層、空気極層、電解液リザーブ層、セパレータ、負極層及び負極集電体が積層するように、各部材を収容した。電解液リザーブ層及びセパレータに、非水系電解液を充填させ、リチウム空気電池を作製した。
空気極層を以下のようにして作製し、電解液リザーブ層を設けなかったこと以外は、実施例2と同様にしてリチウム空気電池を作製した。すなわち、空気極層は、実施例2と同様の空気極層スラリーをガラス基板上に塗工及び乾燥させ、得られた塗工物をガラス基板から剥離及び切断することによって作製した。
上記実施例及び比較例のリチウム空気電池を以下のようにして評価した。
(実施例1及び比較例1)
まず、電池ケース内を60kPaで減圧した後アルゴンガスを封入(パージ)するというガス置換操作を15回繰り返し、電池ケース内にアルゴンガスを密封した。その後、電池ケース内を酸素ガス(純酸素、大陽日酸製、99.9%)で充分に置換した。続いて、リチウム空気電池を、25℃で3時間静置した。
静置後、酸素雰囲気(純酸素、大陽日酸製、99.9%)下、0.02mA/cm2、25℃にて、定電流充放電測定を行い、空気極層の単位重量あたりの初回放電容量を計測した。放電終止電圧は2.0Vとした。表1及び図5に結果を示す。
静置温度及び定電流充放電測定温度を60℃、並びに、定電流充放電測定の電流密度を0.05mA/cm2に変更したこと以外は、実施例1及び比較例1と同様にして、評価を行った。表2及び図5に結果を示す。
また、上記実施例1及び実施例2では、電解液リザーブ層の孔径が空気極層の孔径よりも大きいため、電解液リザーブ層から空気極層への電解液の供給がより効果的に促進されたと考えられる。
2…負極層
3…電解質層
4…電解液リザーブ層
5…空気極缶
6…負極缶
7…ガスケット
8…空気取り込み孔
9…空気リザーブ層
10…酸素透過膜
11…負極保護層
100…金属空気電池
101…金属空気電池
102…金属空気電池
Claims (6)
- 空気極層と、負極層と、前記空気極層及び前記負極層との間に配置される電解質層とを備え、
前記電解質層が、絶縁性及び多孔質構造を有するセパレータと、該セパレータ内に含浸された電解液とを有し、
前記セパレータと前記空気極層との間に、前記セパレータよりも孔径が大きい多孔質構造を有する電解液リザーブ層を備えることを特徴とする金属空気電池。 - 前記電解液リザーブ層の孔径が、前記空気極層の孔径よりも大きい、請求の範囲第1項に記載の金属空気電池。
- 前記電解液リザーブ層の孔径が1~50μmであり、前記セパレータの孔径が0.02~1μmである、請求の範囲第1項又は第2項に記載の金属空気電池。
- 前記電解液リザーブ層の空隙率が50~90%である、請求の範囲第1項乃至第3項のいずれかに記載の金属空気電池。
- 前記電解液リザーブ層が導電性を有する、請求の範囲第1項乃至第4項のいずれかに記載の金属空気電池。
- リチウム空気電池である、請求の範囲第1項乃至第5項のいずれかに記載の金属空気電池。
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CN201180071729.2A CN103828121A (zh) | 2011-09-29 | 2011-09-29 | 金属空气电池 |
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CN104600399B (zh) * | 2014-12-11 | 2016-02-17 | 渤海大学 | 电解液补给式锂氧电池 |
KR20170125807A (ko) * | 2014-12-14 | 2017-11-15 | 보오드 오브 트러스티스 오브 더 유니버시티 오브 일리노이즈 | 진보된 금속-공기 배터리용 촉매 시스템 |
KR102544961B1 (ko) | 2014-12-14 | 2023-06-19 | 보오드 오브 트러스티스 오브 더 유니버시티 오브 일리노이즈 | 진보된 금속-공기 배터리용 촉매 시스템 |
JP2018517252A (ja) * | 2015-05-26 | 2018-06-28 | ユニスト(ウルサン ナショナル インスティテュート オブ サイエンス アンド テクノロジー) | コイン形二次電池とその製造方法、およびコイン形二次電池充放電装置 |
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JP5637317B2 (ja) | 2014-12-10 |
JPWO2013046403A1 (ja) | 2015-03-26 |
CN103828121A (zh) | 2014-05-28 |
US20140205917A1 (en) | 2014-07-24 |
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