JP2013125736A - Metal air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal air battery from which recovery of the solid of a product material in an electrolyte can be easily performed at low cost.SOLUTION: In a metal air battery, an air electrode and a negative electrode are separated by an electrolyte separator having permeability to metal ions of a negative electrode active material, an aqueous electrolyte 2 is filled on the air electrode side of the electrolyte separator, and a nonaqueous electrolyte 5 is filled on the negative electrode side of the electrolyte separator. The metal air battery includes a heating means for making the temperature of the center axis side of a space, where a liquid corresponding to the aqueous electrolyte among an electrolyte on an outer side electrode and an electrolyte on an inner side electrode is filled, to be higher than that of the outer side.

Description

  The present invention relates to a metal-air battery such as a lithium-air battery.

  In recent years, miniaturization of portable electronic devices has been progressing rapidly, and the power source is also required to have a high energy density. An air battery using oxygen in the air as a positive electrode active material has a higher capacity than a lithium secondary battery that is currently widely used, and is promising as a next-generation power source. As an air battery, metal air batteries, such as a lithium air battery, a magnesium air battery, and a zinc air battery, are known, for example.

In metal-air batteries, solids generated by electrode reactions (hereinafter referred to as product solids) accumulate in the air electrode, causing the air electrode to become clogged, blocking the contact between the electrolyte and air, and charging and discharging. There was a problem of causing trouble.
As a technique for solving the problem of precipitation of product solids, it has been proposed to use an aqueous electrolyte as the electrolyte of a metal-air battery. In the case of a metal-air battery using an aqueous electrolyte, a metal hydroxide is generated as a product solid, and the product solid is water-soluble, so that the product solid can be dissolved in the aqueous electrolyte. Precipitation of physical solids can be suppressed.
However, the metal-air battery using the aqueous electrolyte has a problem that the product solid is deposited when the saturation solubility of the salt in the aqueous electrolyte is exceeded, and the battery is deactivated.
As a technique for eliminating such battery deactivation, for example, in Patent Document 1, in a lithium-air battery, the temperature of the portion where the aqueous electrolyte is not immersed in the air electrode is immersed in the air electrode. By providing a temperature control means that lowers the temperature of the portion where the water is present, a temperature gradient is positively formed in the aqueous electrolyte solution, convection is generated to improve ion conductivity, and the product concentration is locally increased. A technique for preventing the battery from being deactivated by suppressing the precipitation of lithium hydroxide (LiOH), which is a product solid in an undesired place, is disclosed.
Conventionally, a system for suppressing the precipitation of product solids in an undesired place has been proposed, but although the life of the battery can be extended by suppressing the precipitation of product solids, It is difficult to completely prevent precipitation. Therefore, not only the precipitation of the product solid itself is prevented, but also a maintenance method such as removing and recovering the deposited material and reusing it is important.

JP 2011-096456 A

In the conventional metal-air battery as disclosed in Patent Document 1, the temperature adjustment means is provided to positively form a temperature gradient in the aqueous electrolyte, thereby causing vertical convection due to the temperature difference. In vertical convection, turbulent flow is likely to occur, and a product solid having a small average particle size is generated in the electrolyte in a highly dispersed manner. Therefore, it is difficult to recover the product solid, and a recovery process using expensive equipment is required for recovery, which raises a problem that the recovery cost increases.
The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a metal-air battery in which product solids can be easily recovered and can be recovered at low cost.

In the present invention, the air electrode and the negative electrode are partitioned by an electrolyte separator that is permeable to metal ions of the negative electrode active material, and the aqueous electrolyte is filled on the air electrode side of the electrolyte separator. A metal-air battery in which the negative electrode side of the separator is filled with a non-aqueous electrolyte,
Inside the exterior part having a hollow columnar shape and arranging the outer electrode selected from the air electrode and the negative electrode on at least a part of the side surface,
An interior part having a hollow columnar shape whose diameter is smaller than that of the exterior part and at least a part of the side surface of which is formed by the electrolytic separator is made parallel to the central axis of the exterior part and the central axis of the interior part. Housed,
An inner pole that is a counter electrode of the outer pole is accommodated in the interior portion,
Filling the space partitioned by the side surface of the exterior portion and the side surface of the interior portion with the electrolyte solution of the outer electrode,
Filling the interior part with the electrolyte solution of the inner electrode,
Among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode, the space filled with the liquid corresponding to the aqueous electrolyte solution, provided with a heating means that makes the central axis side higher temperature than the outside,
A metal-air battery is provided.
In this invention, it is preferable to provide the heating means which heats the said inner side pole.
In this invention, it is preferable that the said interior part is coaxially arrange | positioned inside the said exterior part.
In this invention, it is preferable that the said exterior part and the said interior part have the shape of a polygonal column or a cylinder.
In this invention, it is preferable to provide a cooling means for cooling the outer electrode.
In the present invention, the electrolyte separator is preferably a multilayer film including a solid electrolyte membrane facing the non-aqueous electrolyte and a cation exchange membrane facing the aqueous electrolyte.
In the present invention, it is preferable that the inner electrode has a higher temperature than the outer electrode, and the temperature difference can be 40 ° C. or more.
In this invention, it is preferable to provide the electrode only for charge which contacts the said aqueous electrolyte solution.
In this invention, it is preferable to provide the collection | recovery means which collect | recovers the solids produced | generated from the said aqueous electrolyte solution.
The metal air battery of the present invention is preferably a lithium air battery.

  ADVANTAGE OF THE INVENTION According to this invention, the metal air battery which can be collect | recovered easily and can be collect | recovered at low cost can be provided by precipitating the product solid with a large average particle diameter to the battery lower part.

It is explanatory drawing explaining the metal air battery of this invention. It is explanatory drawing explaining the metal air battery of this invention. It is explanatory drawing explaining the state at the time of the horizontal convection generation | occurrence | production of the metal air battery of this invention. It is explanatory drawing explaining the metal air battery used by the comparative example 1. FIG. 4 is a graph showing changes in the amount of LiOH particles collected in the battery lower part in Example 1. FIG. 2 is a graph comparing LiOH particle diameters recovered in Example 1 and Comparative Example 1. FIG. 2 is an electron micrograph of LiOH particles collected in the upper part of the battery in Example 1. FIG. 2 is an electron micrograph of LiOH particles collected at the bottom of the battery in Example 1. FIG. 2 is an electron micrograph of LiOH particles recovered in Comparative Example 1.

The present invention partitions an air electrode and a negative electrode with an electrolyte separator that is permeable to metal ions of the negative electrode active material, and fills the air electrode side of the electrolyte separator with an aqueous electrolyte, A metal-air battery in which a negative electrode side is filled with a non-aqueous electrolyte,
Inside the exterior part having a hollow columnar shape and arranging the outer electrode selected from the air electrode and the negative electrode on at least a part of the side surface,
An interior part having a hollow columnar shape whose diameter is smaller than that of the exterior part and at least a part of the side surface of which is formed by the electrolytic separator is made parallel to the central axis of the exterior part and the central axis of the interior part. Housed,
An inner pole that is a counter electrode of the outer pole is accommodated in the interior portion,
Filling the space partitioned by the side surface of the exterior portion and the side surface of the interior portion with the electrolyte solution of the outer electrode,
Filling the interior part with the electrolyte solution of the inner electrode,
Among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode, the space filled with the liquid corresponding to the aqueous electrolyte solution, provided with a heating means that makes the central axis side higher temperature than the outside,
A metal-air battery is provided.
In the present invention, the “center axis side” means a position where the center axis of the exterior part and the interior part exists in the space or a position closest to the position where the center axis exists, and “outside” means the center axis. Means the farthest position (outermost edge).
Hereinafter, the configuration and embodiments of the present invention will be described in detail. Although the present invention will be described in detail with reference to the drawings and examples, the present invention is not limited to these drawings and examples.

FIG. 1 is a schematic view showing an example (reference numeral 101) of the metal-air battery of the present invention. A metal-air battery 101 shown in FIG. 1 includes an interior portion 3 having a hollow quadrangular prism shape whose diameter is smaller than that of the exterior portion 1 inside the exterior portion 1 having a hollow quadrangular prism shape. It has the structure arrange | positioned coaxially so that the side surface of the part 3 may become parallel.
A metal-air battery 101 shown in FIG. 1 uses an air electrode as an outer electrode and a negative electrode as an inner electrode, and reference numeral 101A denotes an internal structure of the exterior part 1 of the metal-air battery 101. The exterior part 1 is provided with an air electrode (not shown) on at least a part of its side surface and accommodates the interior part 3. A space divided by the side surface of the exterior part 1 and the side surface of the interior part 3 is filled with the aqueous electrolyte 2. Furthermore, the electrode 4 only for charge is provided in the position which contacts the aqueous electrolyte 2, and does not contact an air electrode (not shown).
Reference numeral 101 </ b> B is an enlarged top view of the interior portion 3 for showing the internal configuration of the interior portion 3 of the metal-air battery 101. The interior portion 3 is formed by an electrolyte separator including a solid electrolyte membrane 6 facing at least a part of the side surface of the nonaqueous electrolyte solution 5 and a cation exchange membrane 7 facing the aqueous electrolyte solution 2. Is filled with a non-aqueous electrolyte solution 5. In addition, a sheath heater 9 that houses the negative electrode 8 in a shape that extends in a direction parallel to the central axis and that heats the negative electrode 8 is wired along the negative electrode 8 inside the interior portion 3.
A drainage pipe 10 for recovering the product solid is provided in at least a part of a portion where the aqueous electrolyte 2 is located at the bottom of the battery.
In the case of FIG. 1, the space filled with the liquid corresponding to the aqueous electrolytic solution among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode is partitioned by the side surface of the exterior portion 1 and the side surface of the interior portion 3. The central axis side of the space corresponding to the space and filled with the liquid corresponding to the aqueous electrolyte corresponds to the position of the side surface of the interior part 3, and the outside of the space filled with the liquid corresponding to the aqueous electrolyte is the exterior part. Corresponds to the position of 1 side.

FIG. 2 shows that the interior part 3 having a hollow cylindrical shape whose diameter is smaller than that of the exterior part 1 is arranged inside the exterior part 1 having a hollow cylindrical shape so that the side surface of the exterior part 1 and the side surface of the interior part 3 are parallel to each other. It is the schematic which shows an example (code | symbol 102) of the metal air battery which has the structure arrange | positioned coaxially.
The metal-air battery 102 shown in FIG. 2 uses a negative electrode for the outer electrode and an air electrode for the inner electrode, and reference numeral 102A is a diagram showing the internal structure of the exterior part 1 of the metal-air battery 102. Is provided with a negative electrode (not shown) on at least a part of its side surface and accommodates the interior portion 3. A non-aqueous electrolyte solution 5 is filled in a space partitioned by the side surface of the exterior portion 1 and the side surface of the interior portion 3.
Reference numeral 102 </ b> B is an enlarged top view of the interior part 3 for showing the internal configuration of the interior part 3 of the metal-air battery 102, and the interior part 3 is a solid whose at least part of the side faces the non-aqueous electrolyte 5. It is formed by an electrolyte separator composed of an electrolyte membrane 6 and a cation exchange membrane 7 facing the aqueous electrolyte solution 2 and accommodates an air electrode 11. The air electrode 11 is processed into a hollow cylindrical shape, and is coaxially arranged so that the side surface of the interior portion 3 and the side surface of the air electrode 11 are parallel to each other. In addition, a space that is inside the interior part 3 and is partitioned by the side surface of the interior part 3 and the side surface of the air electrode 11 is filled with the aqueous electrolyte 2. Furthermore, the electrode 4 only for charge is provided in the position which contacts the aqueous electrolyte 2 and does not contact the air electrode 11.
A blower 12 for sending high-temperature air to the air electrode 11 is provided outside the metal-air battery 102, and the direction of blowing is indicated by an arrow 13. An air hole 14 for sending high-temperature air to the air electrode 11 is provided so as to penetrate the metal air battery 102 in a direction parallel to the central axis of the air electrode 11 in alignment with the air electrode 11.
A drainage pipe 10 for recovering the product solid is provided in at least a part of a portion where the aqueous electrolyte 2 is located at the bottom of the battery.
In the case of FIG. 2, the space filled with the liquid corresponding to the aqueous electrolyte among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode is partitioned by the side surface of the interior part 3 and the side surface of the air electrode 11. The central axis side of the space corresponding to the space and filled with the liquid corresponding to the aqueous electrolyte corresponds to the position of the side surface of the air electrode 11, and the outside of the space filled with the liquid corresponding to the aqueous electrolyte is the interior portion. This corresponds to the position of the side surface 3.

FIG. 3 is a schematic diagram showing an example (reference numeral 103) of the metal-air battery of the present invention when horizontal convection occurs. The metal-air battery 103 shown in FIG. 3 uses an air electrode for the outer electrode and a negative electrode for the inner electrode. By heating the negative electrode with a sheath heater, the non-aqueous electrolyte filled in the interior portion 3 is It becomes a heat medium, the interior part 3 as a whole is heated, a temperature gradient is positively formed between the side surface of the interior part 3 and the side surface of the exterior part 1, and a temperature difference in the horizontal direction is given. Two horizontal convections 15 are generated in a space partitioned by the side surface of the exterior portion 1 and the side surface of the interior portion 3. The product solid 16 having a small average particle diameter generated by the electrode reaction by the horizontal convection 15 can be dispersed in the battery upper part 18 and the product solid 17 having a large average particle diameter can be precipitated in the battery lower part 19. The product solid 17 having a large average particle size precipitated in the battery lower part 19 can be recovered from the drain tube 10 provided at the battery bottom.
Here, “horizontal convection” is fluid movement that occurs when a horizontal temperature difference is given to the fluid. In the present invention, the central axis of the exterior part and the central axis of the interior part are parallel to each other. The interior part is housed inside the exterior part, and the central axis side of the space filled with the liquid corresponding to the aqueous electrolyte solution among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode is uniformly heated along the axial direction. In addition, it refers to convection of the aqueous electrolyte that occurs when a temperature difference in the horizontal direction is applied between the center axis side and the outside of the space such that the center axis side is hotter than the outside.
That is, in the space filled with the aqueous electrolyte solution, the rising liquid flow is generated along the side surface on the central axis side due to the heat input to the central axis side, and outward in the radial direction from the battery ceiling. A series of fluid movements are repeated, being pushed out, lowered while being cooled by heat release at the outer side surface, and pushed back toward the central axis side at the battery bottom. A series of fluid movements between the central axis side and the outside is horizontal convection.
In addition, when using the negative electrode for the outer electrode as shown in FIG. 2 and the air electrode for the inner electrode, the aqueous electrolyte is filled in the space partitioned by the side surface of the interior part and the side surface of the air electrode, The air electrode is heated uniformly along the axial direction by the high-temperature air, and a horizontal temperature difference is given between the side surface of the interior part and the side surface of the air electrode, so that the side surface of the interior part and the side surface of the air electrode Horizontal convection occurs in the partitioned space.

In the metal-air battery of the present invention, when the air electrode is selected as the outer electrode, the negative electrode is selected as the inner electrode, and when the negative electrode is selected as the outer electrode, the air electrode can be selected as the inner electrode. In the present invention, the outside of the exterior part is easier to take in air than the inside of the interior part, and from the viewpoint of protecting the metal used for the negative electrode from moisture, carbon dioxide, etc., the air electrode on the outer electrode and the negative electrode on the inner electrode It is preferable to select.
The structure of the metal-air battery when the air electrode is selected as the inner electrode is not particularly limited as long as air can be sent to the air electrode, but the viewpoint of uniformly heating the air electrode along the axial direction is not limited. 2, the air electrode itself is processed into a hollow column shape, the air electrode is arranged so that the side surface of the interior part and the side surface of the air electrode are parallel, and the air hole for sending air to the air electrode A structure in which the metal-air battery is passed through in a direction parallel to the central axis of the air electrode while being aligned with the air electrode is preferable.
In the metal-air battery of the present invention, it is sufficient that the interior part is accommodated at least inside the exterior part so that the central axis of the exterior part and the central axis of the interior part are parallel to each other. From the viewpoint of recovering the product solids having the same size, it is more preferable that the interior portion is coaxially arranged inside the exterior portion.
The shape of the exterior part and interior part of the metal-air battery of the present invention may be at least a hollow columnar shape, but preferably has a polygonal columnar or cylindrical shape, and the shape of the product solid can be spherical, A cylindrical shape is particularly preferable because recovery becomes easier.

The metal-air battery of the present invention corresponds to the aqueous electrolyte solution by setting the central axis side of the space filled with the solution corresponding to the aqueous electrolyte solution out of the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode to a temperature higher than the outside. Any device capable of causing a temperature difference between the central axis side and the outside of the space filled with the liquid may be used, but between the central axis side and the outside of the space filled with the liquid corresponding to the aqueous electrolyte solution. The temperature difference is preferably 40 ° C. or more from the viewpoint of the amount of product solid recovered.
The temperature difference is preferably during discharging.

The present inventor suppresses the high dispersion of the product solid by generating horizontal convection, and precipitates the product solid having a larger average particle diameter and a larger size than the conventional product solid at the bottom of the battery. And found that it can be collected. According to the present invention, the recovery of the product solid is facilitated, and the product solid can be recovered at a low cost.
Here, “recovery at a low cost” means that a recovery process using expensive equipment such as a concentrator and a solidifying device, which is necessary at the time of recovery, is not required for reusing product solids, or the device configuration is simplified. Particularly preferably, the step of granulation → drying → classification can be made unnecessary. In the present invention, by precipitating and collecting product solids having a large average particle size at the bottom of the battery, precipitation is facilitated, ideally no granulation step is required, and product solids with uniform sizes are obtained. As a result, the classification step is not necessary, so that collection is possible without using expensive equipment, and the collection cost can be reduced.
In addition, it is preferable that an average particle diameter is 1 micrometer or more from a viewpoint of the ease of collection | recovery.
Further, the “particle diameter” in the present invention means the average value of the measured major axis and minor axis when the major axis and minor axis of the particle are measured under an electron microscope, and the “average particle diameter” It means the average value of the particle diameter of each particle arbitrarily selected from the group.

  Hereinafter, the material of the metal-air battery of the present invention will be described.

(Air electrode)
The air electrode has an air electrode layer containing at least a conductive material, and usually has an air electrode current collector and an air electrode lead connected to the air electrode current collector. . In the air electrode layer, the supplied oxygen (active material) and metal ions react to generate metal oxide or metal hydroxide.

The conductive material is not particularly limited as long as it has conductivity, and examples thereof include a conductive carbon material. Although it does not specifically limit as a conductive carbon material, From the viewpoint of the area and space of the reaction field which a metal oxide and a metal hydroxide produce | generate, the carbon material which has a high specific surface area is preferable.
Specifically, 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. Here, the specific surface area of the conductive material can be measured by, for example, the BET method. The addition amount of the conductive material is preferably in the range of 10% by weight to 99% by weight in the air electrode layer.
Specific examples of the conductive carbon material having a high specific surface area include graphite, ketjen black (registered trademark, KB), acetylene black, carbon nanotube, and carbon fiber.

The conductive material may carry a catalyst.
Examples of the catalyst include cobalt phthalocyanine, manganese phthalocyanine, nickel phthalocyanine, tin phthalocyanine oxide, titanium phthalocyanine, and dilithium phthalocyanine; naphthocyanine compounds such as cobalt naphthocyanine; and porphyrin compounds such as iron porphyrin; _{MnO 2, La 0.8 Sr 0.2 CoO} 3, 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, LiCrO 2, LiCoO 2, LiCuO 2 , L _{ZnO 2, Li 2 MoO 4,} LiNbO 3, LiTaO 3, Li 2 WO 4, Li 2 ZrO 3, NaMnO 2, CaMnO 3, CaFeO 3, MgTiO 3, KMnO metal oxides such as _2; Au, Pt, Ag, etc. Noble metals; composites of these, and the like. In the air electrode layer, the content of the air electrode catalyst is preferably in the range of 1% by weight to 90% by weight, for example.

  The air electrode layer preferably contains a binder that fixes the conductive material. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR). Although it does not specifically limit as content of the binder contained in the said air electrode layer, For example, it is preferable that it is 1 to 40 weight%, and it is especially preferable that it is 10 to 30 weight%. When the binder content is 10% by weight or more, the air electrode layer can be easily formed. On the other hand, when the binder content is 30% by weight or less, a desired reaction can be efficiently advanced without reducing the reaction field of the air electrode.

  Examples of the method for preparing the air electrode layer include a slurry method. When the air electrode layer is prepared by a slurry method, examples of the solvent include solvents having a boiling point of 200 ° C. or lower, such as acetone, ethanol, N-methyl-2-pyrrolidone (NMP), and the like. Examples of the slurry application method include a doctor blade method and an ink jet method. After applying the slurry to the current collector or carrier film, the air electrode layer can be formed by drying, rolling and cutting. When a porous metal is used as the current collector, a part of the air electrode layer can be infiltrated into the current collector by applying a slurry. Moreover, the method of crimping | bonding to the collector the thing which dried and rolled the electrode composition which adjusted the slurry to the clay form to the film form may be sufficient. The thickness of the air electrode layer varies depending on the use of the air battery, but is preferably in the range of 2 to 500 μm, particularly in the range of 5 to 300 μm.

  The air electrode current collector has a porous structure as long as it can exist stably in the operating range of lithium-air battery (2 to 4.5 V (vs lithium)) and has a desired electronic conductivity. However, from the viewpoint of diffusibility of air (oxygen), those having a porous structure are preferable. Examples of 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.

  Examples of the material of the air electrode current collector include metal materials such as stainless steel, nickel, aluminum, iron, titanium, and copper, carbon materials such as carbon fiber and carbon paper, and high electron conductive ceramic materials such as titanium nitride. Is mentioned. A current collector using a carbon material has high corrosion resistance, and when a strong alkaline metal oxide is generated by a discharge reaction at the air electrode, the current collector is prevented from eluting, and the battery resulting therefrom It has the merit that deterioration of characteristics can be suppressed. Preferred specific air electrode current collectors include carbon paper and metal mesh. The thickness of the air electrode current collector is not particularly limited as long as the current collector itself is not curved when the cell is constrained, but is preferably 10 to 1000 μm, particularly preferably 20 to 400 μm, for example. Moreover, in this invention, the protective case mentioned later may have the function as an air electrode electrical power collector.

(Negative electrode)
The negative electrode has a negative electrode layer containing at least a negative electrode active material. In general, the negative electrode has a negative electrode current collector and a negative electrode lead connected to the negative electrode current collector. In the negative electrode layer, metal ions are occluded / released in response to the reaction at the air electrode.

  The negative electrode active material is not particularly limited as long as it can occlude and release metal ions. The metal ion is not particularly limited as long as it moves between the air electrode and the negative electrode to generate an electromotive force. Specifically, lithium ion, sodium ion, aluminum ion, magnesium ion , Cesium ions, etc., among which lithium ions are preferred.

Specific examples of the negative electrode active material include alkali metals such as lithium, sodium, and potassium; group 2 elements such as magnesium and calcium; group 13 elements such as aluminum; transition metals such as zinc and iron; Examples include noble metals; or alloy materials and compounds containing these metals.
The negative electrode active material of the lithium-air battery is not particularly limited as long as it has a lithium element, and the same negative electrode active material used in a general lithium ion battery can be used. Specifically, lithium metal, lithium alloy, metal oxide, metal sulfide, metal nitride, and the like can be given. Among them, metal lithium is more preferable from the viewpoint of increasing the capacity.

  In the present invention, the negative electrode layer may contain at least a negative electrode active material, but may contain a binder for immobilizing the negative electrode active material, if necessary. About the kind of binder, usage-amount, etc., since it is the same as that of the content described in the air electrode mentioned above, description here is abbreviate | omitted.

  The material of the negative electrode current collector is not particularly limited as long as it can stably exist in the operating range (2 to 4.5 V (vs lithium)) of a lithium-air battery and has conductivity. For example, copper, stainless steel, nickel, etc. can be mentioned. Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh shape. The thickness of the negative electrode current collector is not particularly limited as long as the current collector itself is not curved when the cell is constrained, and is preferably 10 to 1000 μm, particularly preferably 20 to 400 μm, for example. Further, a protective case described later may also have a function as a negative electrode current collector.

(Electrolyte)
The electrolytic solution in the present invention can be used by filling the space partitioned by the side surface of the exterior part on the outer electrode side and the side surface of the interior part, and the interior of the interior part on the inner electrode side.
In the present invention, an aqueous electrolyte can be used on the air electrode side, and a non-aqueous electrolyte can be used on the negative electrode side.
The aqueous electrolytic solution contains a supporting electrolyte salt and water. The supporting electrolyte salt is not particularly limited as long as it has solubility in water and expresses desired ionic conductivity. Usually, a hydroxide or a metal salt containing a metal ion to be conducted can be used. For example, in the case of a lithium-air battery, for example, lithium hydroxide (LiOH) or a lithium salt such as LiCl, LiNO ₃ , Li ₂ SO ₄ , CH ₃ COOLi, or a mixture thereof can be used.

As the non-aqueous electrolytic solution, an ionic liquid-based electrolytic solution, an organic electrolytic solution, or the like can be used.
The ionic liquid base electrolyte contains an ionic liquid and a supporting electrolyte salt.
Examples of the ionic liquid include N, N, N-triethyl-N-propylammonium bis (trifluoromethanesulfonyl) amide (abbreviation TMPA-TFSA), N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl). Amide (abbreviation PP13-TFSA), N-methyl-N-propylpyrrolidinium bis (trifluoromethanesulfonyl) amide (abbreviation P13-TFSA), N-methyl-N-butylpyrrolidinium bis (trifluoromethanesulfonyl) amide ( Abbreviation P14-TFSA), N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide (abbreviation DEME-TFSA) and the like, and 1- Methyl-3-ethylimida Tetrafluoroborate (abbreviation EMIBF _4), 1-methyl-3-ethyl imidazolium bis (trifluoromethanesulfonyl) amide (abbreviation EMITFSA), 1- allyl-3-ethyl imidazolium bromide (abbreviated AEImBr), 1- allyl - 3-ethylimidazolium tetrafluoroborate (abbreviation AEImBF ₄ ), 1-allyl-3-ethylimidazolium bis (trifluoromethanesulfonyl) amide (abbreviation AEImTFSA), 1,3-diallylimidazolium bromide (abbreviation AAImBr), 1 , 3-diallyl tetrafluoroborate (abbreviation AAImBF _4), 1,3- diallyl imidazolium bis (trifluoromethanesulfonyl) amide (abbreviation AAImTFSA) Arukiruimi such Zoriumu quaternary salts.

The organic electrolytic solution contains a nonaqueous solvent and a supporting electrolyte salt.
The non-aqueous solvent is not particularly limited. For example, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate. , Isopropiomethyl carbonate, ethyl propionate, methyl propionate, γ-butyrolactone, ethyl acetate, methyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetonitrile (AcN), dimethyl sulfoxide (DMSO) , Diethoxyethane, dimethoxyethane (DME), tetraethylene glycol dimethyl ether (TEGDME), etc. .

The supporting electrolyte salt only needs to be soluble in an ionic liquid or a non-aqueous solvent and express desired metal ion conductivity. Usually, a metal salt containing a metal ion to be conducted can be used. For example, in the case of a lithium air battery, lithium hydroxide (LiOH) or a lithium salt can be used as the supporting electrolyte salt. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCl, LiNO ₃ , and Li ₂ SO ₄ . In addition, an organic lithium salt such as CH ₃ CO ₂ Li, lithium bisoxalate borate (abbreviation LiBOB), LiN (CF ₃ SO ₂ ) ₂ (abbreviation LiTFSA), LiN (C ₂ F ₅ SO ₂ ) ₂ (abbreviation LiBETA) Can also be used.
In the ionic liquid-based electrolytic solution or the organic electrolytic solution, the content of the supporting electrolyte salt with respect to the ionic liquid or the nonaqueous solvent is not particularly limited, but the concentration of the lithium salt in the ionic liquid-based electrolytic solution is, for example, 0.1 to 3 mol. Within the range of / L.

(Interior part)
As for an interior part, at least one part of a side surface is normally formed of an electrolyte separator.
The part other than the electrolyte separator of the interior part is not particularly limited as long as it has a function of separating the air electrode and the negative electrode and storing the electrolyte, but for example, polyethylene, polypropylene, etc. Examples thereof include porous membranes; non-woven fabrics such as acrylic resins, non-woven fabrics such as glass fiber non-woven fabrics; and polymer materials used in lithium polymer batteries.
The electrolyte separator is a multilayer film composed of a solid electrolyte membrane facing a non-aqueous electrolyte and a cation exchange membrane facing an aqueous electrolyte. The cation exchange membrane is provided to protect the solid electrolyte membrane from the aqueous electrolyte.
The solid electrolyte membrane is preferably one having alkali resistance, but is not particularly limited, and examples thereof include inorganic solid electrolytes, polymer electrolytes, and gel electrolytes. The inorganic solid electrolyte may be glass, crystal, or glass ceramic.
What is necessary is just to select a specific inorganic solid electrolyte suitably according to a conductive metal ion. For example, in the case of a lithium air battery, a NASICON type oxide, a perovskite type oxide, a LISICON type oxide, a garnet type oxide, etc. can be mentioned.
As the NASICON type oxide, for example, the general formula Li _{1 + X} Al _X Ge _2-X (PO ₄ ) ₃ (0 ≦ x ≦ 1), Li _{1 + y} Al _y Ti _2-y (PO ₄ ) ₃ (0 ≦ y ≦ 1) and the like, and LATP manufactured by OHARA INC. May be used.
Examples of the LISICON-type oxide include LISICON manufactured by OHARA INC.

The cation exchange membrane is not particularly limited as long as it has a function of storing an electrolytic solution and is permeable to metal ions of the negative electrode active material. For example, a cation exchange resin, Nonwoven fabrics made of cation exchange fibers can be mentioned.
Examples of the cation exchange resin include Diaion (registered trademark) SK104 manufactured by Mitsubishi Chemical Corporation.
Examples of the non-woven fabric made of the cation exchange fiber include Nichibi IEF-SC.

(Exterior part)
The exterior part is usually provided with an outer pole on at least a part of the side surface.
The part other than the outer electrode of the exterior part is not particularly limited as long as it has a function of storing an electrolyte solution, and the same part as that used as a part other than the electrolyte separator of the interior part can be exemplified. .

(Protective case)
If necessary, the metal-air battery of the present invention may have a protective case for protecting the outer electrode. When the negative electrode is selected as the outer electrode, it is preferable to have a protective case from the viewpoint of protecting the metal used for the negative electrode from water in the air, carbon dioxide, and the like. If the protective case is not provided, the exterior portion may be sealed with rubber, Teflon (registered trademark) tape or the like in order to prevent liquid leakage.
The shape of the protective case is not particularly limited as long as it can protect the outer electrode.
The protective case is not particularly limited as long as it can block water, carbon dioxide and the like, and examples thereof include a resin case such as an acrylic resin.

(Heating means)
As a means for heating the inner pole, a heating means capable of making the central axis side of the space filled with the liquid corresponding to the aqueous electrolyte out of the outer pole electrolyte and the inner pole electrolyte higher than the outside. If it is not particularly limited, from the viewpoint of causing stable horizontal convection, it is a heating means capable of uniformly heating the central axis side of the space filled with the liquid corresponding to the aqueous electrolyte along the axial direction. Is preferred.
When the negative electrode is selected as the inner electrode, it is not particularly limited as long as it is a heating unit that can heat the negative electrode, but is preferably a heating unit that can uniformly heat the negative electrode along the axial direction. , Sheath heater, plug heater and the like.
When the air electrode is selected as the inner electrode, it is not particularly limited as long as it is a heating means that can heat the air electrode, but it may be a heating means that can uniformly heat the air electrode along the axial direction. Preferably, for example, a blower that blows high-temperature air, a heat exchanger for air conditioning, and the like can be given.
Moreover, the metal-air battery of this invention may be provided with the cooling means which cools the outer side of the space filled with the liquid applicable to aqueous electrolyte solution, if necessary.
The cooling means is not particularly limited as long as it is a cooling means capable of cooling the outside of the space filled with the liquid corresponding to the aqueous electrolyte, but from the viewpoint of causing stable horizontal convection, the liquid corresponding to the aqueous electrolyte is It is preferable that the cooling means can uniformly cool the outside of the filled space along the axial direction.
In addition, when cooling an outer pole, if it is a cooling means which can cool an outer pole, it will not specifically limit, However, It is preferable that it is a cooling means which can cool an outer pole uniformly along an axial direction. .
Examples of the cooling means include a cooling jacket, a blower that blows cold air, and a Peltier cooling unit.

(Charge-only electrode)
The charge-only electrode in the present invention is used in place of the air electrode during charging in order to avoid oxidation of carbon used in the air electrode.
From the viewpoint of preventing oxidation of the air electrode, the charge-dedicated electrode is preferably provided at a position in contact with the aqueous electrolyte and not in contact with the air electrode.
Although it will not specifically limit as long as it has electroconductivity as an electrode for charge, For example, titanium, silver, iron, nickel, aluminum etc. are mentioned.

(Recovery means)
The recovery means is not particularly limited as long as it is a means capable of recovering the product solid produced from the aqueous electrolyte solution. For example, a means for providing a drainage pipe that can be opened and closed as necessary at the bottom of the battery, a forced circulation concentration means, etc. Can be mentioned.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

(Example 1) Outer air electrode inner negative electrode type coaxially arranged square columnar air battery The skeleton of the interior part (12 × 12 × 50 mm ³ ) and the exterior part (25 × 25 × 50 mm ³ ) is made of acrylic resin, and the air electrode current collector The body used Ni mesh. The exterior part was sealed with rubber and Teflon tape.
The negative electrode was produced by processing Li foil into a rectangle (50 × 5 × 0.2 mm ³ ) and polishing the surface.
The aqueous electrolyte solution on the air electrode side was prepared by dissolving LiOH.H ₂ O solid (Aldrich, 99%) with ultrapure water (18.2 MΩcm) to a concentration of 11 mol / L.
An ionic liquid-based electrolyte is used as the non-aqueous electrolyte on the negative electrode side, and N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium (DEME) is mixed with LiN (CF ₃ SO ₂ ) ₂ (LITFSA ) Was added to adjust to 0.32 mol / kg.
The air electrode is made of carbon paper (made by Ketjen Black International, ECP600JD): binder polyvinylidene fluoride (PVDF) = 90: 10 (weight ratio) and acetone. EC-TP-120T, thickness 370 μm).
The air electrode slurry was dried at 80 ° C. for 1 hour in the atmosphere. The basis weight was adjusted to 6 mg / cm ² .
The air electrode was arranged so as to cover the entire four side surfaces of the exterior part.
The negative electrode used was a Li foil (50 × 5 × 0.2 mm ³ , purity 99.99%) attached to a Ni current collector (50 mesh, manufactured by Nilaco Corp.). An Ag / AgCl commercial electrode was used as a reference electrode, and was inserted into an aqueous electrolyte.
As the electrolyte separator, LATP (manufactured by OHARA INC., Thickness: 159 μm, 1.0 × 10 ⁻⁴ S / cm) is used as the solid electrolyte, and Diaion (registered trademark) SK104 (Mitsubishi Chemical Corporation) is used as the cation exchange membrane. Co., Ltd.) (50 μm) was used.

(Evaluation conditions)
The electrochemical measurement was performed using a VMP-3 potentiostat (Biologic) at room temperature (about 25 ° C.) and in the air.
The discharge current density was 0.35 mA / cm ² , the discharge time was 3 hours, the electrode area was 50 cm ² , and the discharge capacity was 52.5 mAh. The voltage was about 1.8V. The total precipitation amount of LiOH particles was controlled by defining the discharge capacity.

(Recovery of LiOH particles)
With the air electrode (low temperature part) kept constant at 10 ° C. using a LIT7070-AL Peltier module (manufactured by Sensor Controls), the temperature of the negative electrode (high temperature part) was changed with a sheath heater, and the air electrode (low temperature part) The amount of LiOH particles recovered in the lower part of the air battery was investigated while making a temperature difference between the negative electrode and the negative electrode (high temperature part).
After 3 hours of discharge, the aqueous electrolyte solution on the air electrode side was withdrawn from the lower part of the battery and filtered through a filter paper (5C, manufactured by Toyo Filter Paper Co., Ltd.) to recover LiOH particles from the lower part of the battery.
FIG. 5 shows the amount of LiOH particles recovered at the lower part of the battery with respect to the temperature difference between the air electrode (low temperature part) and the negative electrode (high temperature part).
As shown in FIG. 5, the amount of LiOH particles recovered at the lower part of the battery was balanced at a temperature difference of 40 ° C. or higher, so that the temperature difference was 50 ° C. (air electrode side aqueous electrolyte 10 ° C./negative electrode side ionic liquid 60 ° C.) The average particle diameter of LiOH particles collected from the lower part of the battery was measured with an electron microscope.
The average particle diameter was calculated by arbitrarily selecting 100 particles and measuring the major axis and minor axis of each particle under an electron microscope. The results are shown in FIG.
In order to compare the size of LIOH particles floating at the top of the battery and LiOH particles precipitated at the bottom of the battery, an electron micrograph of LiOH particles collected from the top of the battery is shown in FIG. An electron micrograph of the recovered LiOH particles is shown in FIG.

(Comparative Example 1)
A battery disclosed in Japanese Patent Application Laid-Open No. 2011-096456 shown in FIG. 4 is used, and an aqueous electrolyte similar to the aqueous electrolyte used on the air electrode side in Example 1 is used as the electrolyte. Example except that the temperature of the portion where the aqueous electrolyte solution is not immersed in the air electrode (cooling portion) is 0 ° C., and the temperature of the portion where the aqueous electrolyte solution is immersed in the air electrode (aqueous electrolyte solution is 10 ° C.) Discharge was performed under the same evaluation conditions as in. After the discharge, LiOH particles dispersed in the aqueous electrolyte were recovered. The average particle diameter of the collected LiOH particles was measured and shown in FIG. 6, and an electron micrograph of the LiOH particles was shown in FIG.

(Observation results)
As shown in FIG. 6, the average particle diameter of the LiOH particles recovered in Example 1 is 72 μm, and the average particle diameter of the LiOH particles recovered in Comparative Example 1 is 11 μm, which is compared with Comparative Example 1. It can be seen that the average particle diameter of the LiOH particles recovered in Example 1 is larger.
Also, the LiOH particles recovered from the battery lower part of Example 1 shown in FIG. 8 are larger than the LiOH particles recovered from the battery upper part of Example 1 shown in FIG. 7 and the LiOH particles recovered in Comparative Example 1 shown in FIG. This shows that the LiOH particles recovered from the battery lower part of Example 1 are the largest.

DESCRIPTION OF SYMBOLS 1 Exterior part 2 Aqueous electrolyte 3 Interior part 4 Charge-only electrode 5 Non-aqueous electrolyte 6 Solid electrolyte membrane 7 Cation exchange membrane 8 Negative electrode 9 Sheath heater 10 Drain pipe 11 Air electrode 12 Blower 13 Arrow which shows the direction of high temperature air 14 Air hole 15 Horizontal convection 16 Product solid with small average particle diameter 17 Product solid with large average particle diameter 18 Upper part of battery 19 Lower part of battery 20 Comparative example 1 Air electrode 21 Comparative example 1 Negative electrode 22 Comparative example 1 Aqueous electrolyte 23 Exterior Body 24 Separator 25 Peltier element 26 Thermal conductor 27 Heat receptor 28 Insulator 50 Conductivity meter 51 Air electrode side thermocouple 52 Electrolyte side thermocouple 101 Coaxially arranged square columnar metal air battery 101A Exterior part internal structure 101B Interior part Internal structure 102 Coaxially arranged cylindrical metal-air battery 102A Exterior part internal structure 102B Interior part internal structure 103 Coaxial arrangement when horizontal convection occurs Quadrangular prism shape metal-air battery

Claims (10)

The air electrode is separated from the negative electrode by an electrolyte separator that is permeable to the metal ions of the negative electrode active material, the aqueous electrolyte is filled on the air electrode side of the electrolyte separator, and the negative electrode side of the electrolyte separator is A metal-air battery filled with a non-aqueous electrolyte,
Inside the exterior part having a hollow columnar shape and arranging the outer electrode selected from the air electrode and the negative electrode on at least a part of the side surface,
An interior part having a hollow columnar shape whose diameter is smaller than that of the exterior part and at least a part of the side surface of which is formed by the electrolytic separator is made parallel to the central axis of the exterior part and the central axis of the interior part. Housed,
An inner pole that is a counter electrode of the outer pole is accommodated in the interior portion,
Filling the space partitioned by the side surface of the exterior portion and the side surface of the interior portion with the electrolyte solution of the outer electrode,
Filling the interior part with the electrolyte solution of the inner electrode,
Among the electrolyte solution of the outer electrode and the electrolyte solution of the inner electrode, the space filled with the liquid corresponding to the aqueous electrolyte solution, provided with a heating means that makes the central axis side higher temperature than the outside,
A metal-air battery characterized by the above.   The metal-air battery according to claim 1, comprising heating means for heating the inner electrode.   The metal-air battery according to claim 1 or 2, wherein the interior part is coaxially arranged inside the exterior part.   The metal-air battery according to any one of claims 1 to 3, wherein the exterior part and the interior part have a polygonal column shape or a cylindrical shape.   The metal-air battery according to any one of claims 1 to 4, further comprising a cooling unit that cools the outer electrode.   The metal-air battery according to any one of claims 1 to 5, wherein the electrolyte separator is a multilayer film including a solid electrolyte membrane facing a non-aqueous electrolyte solution and a cation exchange membrane facing an aqueous electrolyte solution. .   7. The metal-air battery according to claim 1, wherein the inner electrode has a higher temperature than the outer electrode, and the temperature difference can be 40 ° C. or more.   The metal-air battery according to any one of claims 1 to 7, further comprising a charging-dedicated electrode that contacts the aqueous electrolytic solution.   The metal-air battery according to any one of claims 1 to 8, further comprising recovery means for recovering a solid generated from the aqueous electrolyte.   The metal-air battery according to any one of claims 1 to 9, which is a lithium-air battery.