JP6601367B2 - Metal air battery system - Google Patents

Description

  The present invention relates to a metal-air battery system.

  An air battery using oxygen as a positive electrode active material has many advantages such as high energy density. As an air battery, for example, a metal air battery such as an aluminum air battery or a magnesium air battery using a metal element as a negative electrode active material is known.

For example, Patent Document 1 includes first and second electrolytic baths that store an electrolytic solution, a metal electrode and an air electrode provided in the first electrolytic bath, and a metal ion or a metal compound in the electrolytic solution. Is disclosed as a deposit in the second electrolyte bath. Here, by providing a cooling unit for cooling the electrolytic solution in the second electrolytic solution tank, precipitates are deposited in the second electrolytic solution tank, and the cell reaction in the first electrolytic solution tank is inhibited by the precipitates. Is suppressed.

JP 2013-225444 A

  However, since the cooling unit is disposed in the second electrolyte bath, precipitates are easily formed on the surface of the cooling unit, and further, the cooling unit is provided apart from the recovery unit for collecting the precipitates, Since it does not have the structure which moves the deposit which precipitated in the cooling part to a recovery part, a precipitate cannot be easily recovered from a recovery part. This invention is made | formed in view of the said situation, and it aims at providing the metal air battery system which can collect | recover deposits easily.

  To achieve the above object, an air electrode, a negative electrode, an electrolytic solution serving as an ion conduction path between the air electrode and the negative electrode, and a first electrolytic solution tank and a second electrolytic solution tank that contain the electrolytic solution And a circulation path through which the electrolyte circulates between the first electrolyte tank and the second electrolyte tank, and the negative electrode is a metal ion or metal compound in the electrolyte as the discharge reaction of the battery proceeds The first electrolyte bath includes the air electrode and the negative electrode, and the second electrolyte bath cools the metal filter provided in a removable manner and the metal filter. A metal-air battery system comprising a cooling unit.

  According to the present invention, by providing a metal filter detachably provided in the second electrolytic solution tank and a cooling unit for cooling the metal filter, the precipitate is preferentially deposited on the metal filter. By removing the metal filter on which the deposit is deposited, a metal-air battery system that can easily collect the deposit can be obtained.

  The metal-air battery system of the present invention has an effect that precipitates can be easily collected.

It is the schematic which shows the structural example of the metal air battery system which has the 1st electrolyte solution tank which concerns on embodiment of this invention, a 2nd electrolyte solution tank, and a circulation path. It is the schematic which shows the structural example of the 2nd electrolyte solution tank of this invention. It is the schematic which has removed the metal filter of the 2nd electrolyte solution tank of this invention. It is sectional drawing which shows the structural example of the metal air battery cell which concerns on embodiment of this invention. It is an image which shows Al saturated solution in 25 degreeC. It is an image which shows the Al saturated solution in 0 degreeC.

  In a metal-air battery, a deposit of a metal compound derived from the negative electrode is generated by a discharge reaction. If the deposit adheres to the electrode surface or clogs the electrolytic solution path or the like, the discharge reaction may be inhibited, and the performance of the metal-air battery may be deteriorated. Even if the deposit is preferentially deposited at a specific site, if the deposit is present in the electrolytic solution, the precipitate is dissolved again in the electrolytic solution, and the metal ion concentration in the electrolytic solution increases. When the metal ion concentration reaches the saturation concentration, the precipitate is precipitated again, and the performance of the metal-air battery may be deteriorated. This continues unless the precipitate is removed. For this reason, it is necessary to periodically remove the deposit from the electrolytic solution.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  In the present invention, a metal-air battery refers to a metal oxidation reaction in the negative electrode, a reduction reaction of oxygen, which is an active material, in the air electrode, and an ion that is ionized by an electrolyte solution interposed between the negative electrode and the air electrode. Refers to a battery in which is conducted. The metal-air battery of the present invention may be a primary battery or a secondary battery.

  FIG. 1 is a schematic diagram illustrating a configuration example of a metal-air battery system having a first electrolyte tank, a second electrolyte tank, and a circulation path according to an embodiment of the present invention. As shown in FIG. 1, the metal-air battery system 100 includes a metal-air battery 10, a first electrolyte tank 13 that holds an electrolyte solution 14 inside the metal-air battery 10, and a second container for containing the electrolyte solution 14. And an electrolytic solution tank 22. Further, the first electrolyte tank 13 and the second electrolyte tank 22 are connected, and a circulation path 21 for circulating the electrolyte solution 14 and a liquid pump 23 for circulating the electrolyte solution 14 on the circulation path 21 are provided. .

  The circulation path is connected at two locations on the inflow side and the outflow side in the first electrolyte bath, and the connection location with the first electrolyte bath is such that a flow in one direction can be made from the inflow side toward the outflow side. Is set. The circulation path is also connected at two locations on the inflow side and the outflow side in the second electrolyte bath. During the discharge, the rotational speed of the pump is controlled so that the flow rate of the electrolyte is maintained at 0.1 to 3.0 L / min. The material of the circulation path other than the first electrolytic solution tank and the second electrolytic solution tank is not particularly limited as long as it is stable to the electrolytic solution. Usually, polyethylene, polypropylene, polyethylene terephthalate, tetrafluoroethylene, Ni , SUS, Cu or the like is used.

  The first electrolyte bath only needs to hold the electrolyte and can conduct ions between the negative electrode and the air electrode by the held electrolyte, and may have a layer shape disposed between the negative electrode and the air electrode. In addition, a tank shape in which the negative electrode, the air electrode, and the electrolytic solution are accommodated may be used.

  FIG. 2 is a schematic view showing a configuration example of the second electrolytic solution tank of the present invention. As shown in FIG. 2, the second electrolytic solution tank 22 includes a metal filter 31, a storage part 32 that stores the metal filter, a take-out part 33 provided in the storage part 32, and a cooling part 41. The cooling unit 41 can cool the metal filter 31 via the second electrolyte bath 22.

  FIG. 3 is a schematic view in which the metal filter of the second electrolyte bath of the present invention is removed. As shown in FIG. 3, the metal filter 31 can be removed from the second electrolyte bath 22 by the take-out part 33.

  The material of the second electrolytic solution tank is not particularly limited as long as it is stable to the electrolytic solution. Usually, polyethylene, polypropylene, polyethylene terephthalate, tetrafluoroethylene, Ni, SUS, Cu, or the like is used.

The metal filter is configured to be removable from the second electrolytic solution tank, and deposits can be removed out of the metal air system.
The material of the metal filter is not particularly limited as long as it has alkali resistance and excellent thermal conductivity, and examples thereof include Ni or a material plated with Ni.
In addition, the shape of the metal filter is not particularly limited as long as precipitates can be deposited on the surface, but examples include a fine structure such as a foam or a mesh.

  A cooling part will not be specifically limited if a metal filter can be cooled. By cooling the metal filter present in the electrolytic solution, the saturation concentration of the precipitate on the surface of the metal filter is reduced, and the precipitate can be preferentially deposited on the surface of the metal filter.

  It is preferable to have a heating part on the circulation path where electrolyte solution moves from a 2nd electrolyte solution tank to a 1st electrolyte solution tank. By increasing the temperature of the electrolytic solution in the first electrolytic solution tank, it is possible to suppress precipitation of precipitates in the first electrolytic solution tank.

FIG. 4 is a cross-sectional view showing a configuration example of the metal-air battery cell according to the embodiment of the present invention.
As shown in FIG. 4, the metal-air battery 10 includes a negative electrode 11, an air electrode 12 that is spaced apart from the negative electrode 11, and a first electrolyte bath that is disposed between the negative electrode 11 and the air electrode 12. 13, a negative electrode current collector 15 connected to the negative electrode 11, an air electrode current collector 16 connected to the air electrode 12, and an exterior body 17 for housing them, and a part of the exterior body 17 is repellent. It is composed of a water film 18. The metal-air battery 10 is configured so that the electrolytic solution 14 does not leak from the exterior body 17 using a water repellent film 18 or the like.

The air electrode contains at least a conductive material.
The conductive material is not particularly limited as long as it has conductivity, and examples thereof include a carbon material, a perovskite-type conductive material, a porous conductive polymer, and a metal body.
The carbon material may have a porous structure or may not have a porous structure, but preferably has a porous structure. This is because the specific surface area is large and many reaction fields can be provided. Specific examples of the carbon material having a porous structure include mesoporous carbon and carbon paper. On the other hand, specific examples of the carbon material having no porous structure include graphite, acetylene black, carbon black, carbon nanotube, and carbon fiber.
A metal body can be comprised with the well-known metal stable with respect to electrolyte solution. Specifically, for example, the metal body has a metal layer (coating film) containing at least one metal selected from the group consisting of Ni, Cr, and Al formed on the surface, The whole may be composed of a metal material made of at least one metal selected from the group consisting of Ni, Cr, and Al. The form of the metal body can be a known form such as a metal mesh, a metal foil that has been punched, or a metal foam body.
As content of the electroconductive material in an air electrode, when the mass of the whole air electrode is 100 mass%, for example, it is preferable that it is 10-99 mass%, especially 50-95 mass%.

The air electrode may contain a catalyst that promotes an electrode reaction, and the catalyst may be supported on the conductive material. The catalyst may be supported on carbon paper or a metal body.
As the catalyst, a known catalyst having an oxygen reducing ability that can be used in a metal-air battery can be appropriately used. Examples of the catalyst include at least one metal selected from the group consisting of ruthenium, rhodium, palladium, and platinum; a perovskite oxide containing a transition metal such as Co, Mn, or Fe; a porphyrin skeleton or a phthalocyanine skeleton. Examples thereof include metal coordination organic compounds having inorganic ceramics such as manganese dioxide (MnO ₂ ) and cerium oxide (CeO ₂ ); and composite materials obtained by mixing these materials.
For example, the content of the catalyst in the air electrode is preferably 0 to 90% by mass, and more preferably 1 to 90% by mass, when the mass of the entire air electrode is 100% by mass.

The air electrode contains a binder for immobilizing the conductive material as necessary.
Examples of the binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene / butadiene rubber (SBR), and the like.
Although content of the binder in an air electrode is not specifically limited, For example, when the mass of the whole air electrode is 100 mass%, it is preferable that it is 1-40 mass%, and 10-30 mass. % Is particularly preferred.

Examples of the method for producing the air electrode include a method in which the air electrode material such as a conductive material is mixed and rolled, and a method in which a slurry containing the air electrode material and a solvent is applied. Examples of the solvent used for preparing the slurry include acetone, ethanol, N-methyl-2-pyrrolidone (NMP), and the like. Examples of the slurry application method include a spray method, a screen printing method, a gravure printing method, a die coating method, a doctor blade method, and an ink jet method. Specifically, the slurry can be applied to an air electrode current collector or carrier film, which will be described later, and then dried, and the air electrode can be formed by rolling and cutting as necessary.
The thickness of the air electrode varies depending on the use of the metal-air battery, but is preferably in the range of 0.1 to 3000 μm, particularly preferably in the range of 1 to 1000 μm.

The air electrode has an air electrode current collector that collects current as necessary. 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 property, those having a porous structure such as a mesh shape are preferable. Examples of the shape of the air electrode current collector include a foil shape, a plate shape, a mesh (grid) shape, a punching metal, and a foam metal. 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 for the air electrode current collector include metal materials such as stainless steel, nickel, aluminum, iron, titanium, copper, gold, silver and palladium, carbon materials such as carbon fiber and carbon paper, and high electrons such as titanium nitride. Examples thereof include conductive ceramic materials.
Although the thickness of an air electrode electrical power collector is not specifically limited, For example, it is preferable that it is 1-1000 micrometers, especially 10-400 micrometers. Moreover, the exterior body mentioned later may have the function as an air electrode electrical power collector.
The air electrode current collector may have a terminal serving as a connection portion with the outside.

The negative electrode is made of a metal electrode, or a mesh current collector and a metal active material.
In the case where the negative electrode is a mesh current collector and a metal active material, a tank for storing a metal active material to be dispersed in the electrolytic solution is further provided.

The metal electrode or the metal active material is made of a metal that emits electrons by a discharge reaction of the battery and becomes a metal ion or a metal compound in the electrolytic solution.
Examples of the metal include an aluminum metal containing an impurity, a magnesium metal containing an impurity, an aluminum alloy, a magnesium alloy, an aluminum compound, and a magnesium compound, and an aluminum metal containing an impurity is preferable.
Examples of the aluminum alloy include an alloy with a metal material selected from the group consisting of vanadium, silicon, magnesium, iron, zinc, and lithium. The metal other than aluminum constituting the aluminum alloy may be one kind or two or more kinds. Good.
Examples of the aluminum compound include aluminum (III) nitrate, aluminum (III) chloride oxide, aluminum (III) oxalate, aluminum (III) bromide, and aluminum (III) iodide.
The purity of aluminum when the negative electrode is an aluminum metal containing impurities is not particularly limited. The lower limit of the element ratio of aluminum contained in the aluminum metal containing impurities is preferably 50% or more, particularly 80% or more, more preferably 95% or more, and especially 99.5% or more. Further, the upper limit of the element ratio of aluminum contained in the aluminum metal containing impurities may be less than 99.999%, 99.99% or less, or 99.9% or less. May be. Furthermore, an iron element may be contained in the aluminum metal containing impurities. The element ratio of the iron element contained in the aluminum metal containing impurities is not particularly limited, and may be less than 0.001%, less than 0.01%, or less than 0.1%. May be. Examples of other impurities include metal elements such as silicon, zinc, manganese, zirconium, copper, nickel, titanium, and chromium.
The aluminum alloy preferably has an aluminum content of 50% by mass or more when the mass of the entire alloy is 100% by mass.

  When aluminum metal is used as the metal, for example, aluminum hydroxide is deposited as a precipitate.

The shape of the metal electrode is not particularly limited, and examples thereof include plates, rods, particles, and mesh shapes. In addition, the particle diameter of the particles when the shape is particulate is preferably 1 nm or more, particularly 10 nm or more, more preferably 100 nm or more as the lower limit, and the upper limit is 100 mm or less, particularly 10 mm or less, and further 1 mm or less. Preferably there is.
The average particle diameter of the particles in the present invention is calculated by a conventional method. An example of a method for calculating the average particle size of the particles is as follows. First, a transmission electron microscope (hereinafter referred to as TEM) image or a scanning electron microscope (hereinafter referred to as SEM) image at an appropriate magnification (for example, 50,000 to 1,000,000 times). Then, for a certain particle, the particle diameter when the particle is regarded as spherical is calculated. Calculation of the particle size by such TEM observation or SEM observation is performed for 200 to 300 particles of the same type, and the average of these particles is taken as the average particle size.

  The metal electrode contains at least one of a binder that immobilizes the conductive material and the negative electrode active material, if necessary. For example, when the negative electrode active material is plate-shaped, a negative electrode containing only the negative electrode active material can be obtained. On the other hand, when the negative electrode active material is in a powder (sphere) shape, a negative electrode containing at least one of a conductive material and a binder and the negative electrode active material can be obtained. In addition, about the kind and usage-amount of an electroconductive material, the kind and usage-amount of a binder, it can be made to be the same as the content described in the air electrode mentioned above.

The negative electrode has a negative electrode current collector that collects current from the negative electrode as necessary. The material for the negative electrode current collector is not particularly limited as long as it has conductivity, and examples thereof include stainless steel, nickel, copper, and carbon. Examples of the shape of the negative electrode current collector include a foil shape, a plate shape, and a mesh shape. An exterior body described later may have a function as a negative electrode current collector.
In addition, the negative electrode current collector may have a terminal serving as a connection portion with the outside.

  The 1st electrolyte solution tank arrange | positioned between a negative electrode and an air electrode is satisfy | filled with electrolyte solution. An electrolyte circulation path is connected to the first electrolyte tank, and the electrolyte flowing in from the circulation path moves in the first electrolyte tank at a specific flow rate.

The electrolytic solution is an aqueous solution containing at least a self-discharge reaction inhibitor and an electrolyte compound.
The self-discharge reaction ^{inhibitor, S 2-anion,} SCN ^- _anion, S ^{₂ O 3 2-} _{anions, (CH} 3) 2 NCSS ^- anions, _and one selected from the group consisting of P ₂ ^{O 7 4-} anion is not particularly limited as long as it contains more anions, it preferably contains S ^₂ O ₃ ^2- anions. Specific examples of the cation contained in the self-discharge reaction inhibitor include Li ⁺ , K ⁺ , Na ⁺ , Rb ⁺ , Cs ⁺ , Fr ^{+ and the} like, and K ⁺ and Na ⁺ are preferable. The cation contained in the self-discharge reaction inhibitor is a metal cation that is electrochemically less basic than iron. Therefore, the cation hardly reacts with iron, which is a negative electrode metal, in the electrolytic solution. Therefore, if it is the said cation, it will be hard to inhibit the preferential adsorption | suction of the said anion to iron contained in a negative electrode metal for self-discharge reaction suppression.
Specific examples of the self-discharge reaction inhibitor include Na ₂ S ₂ O ₃ , NaSCN, and (CH ₃ ) ₂ NCSSNa, and Na ₂ S ₂ O ₃ is preferable.
Although content of the self-discharge reaction inhibitor contained in electrolyte solution is not specifically limited, It is preferable that they are 0.005 mol / L or more and 1 mol / L or less.

The electrolyte compound is not particularly limited as long as it has solubility in water and expresses desired ionic conductivity, but the aqueous solution is preferably neutral or basic. From the viewpoint of improving reactivity, those that are basic are particularly preferred.
The electrolyte compound preferably contains at least one metal selected from the group consisting of Li, K, Na, Rb, Cs, Fr, Mg, Ca, Sr, Ba, and Ra. Specific examples of the electrolyte compound include LiCl, NaCl, KCl, MgCl ₂ , CaCl ₂ , LiOH, KOH, NaOH, RbOH, CsOH, Mg (OH) ₂ , Ca (OH) ₂ , and Sr (OH) _2. NaOH and KOH are preferable, and NaOH is particularly preferable.
The concentration of the electrolyte compound is not particularly limited, but the lower limit is preferably 0.01 mol / L or more, particularly 0.1 mol / L or more, more preferably 1 mol / L or more, and the upper limit is preferably 20 mol / L or less. In particular, it is 10 mol / L or less, and further 8 mol / L or less.
When the concentration of the electrolyte compound is less than 0.01 mol / L, the reactivity of the negative electrode metal may be reduced. On the other hand, when the concentration of the electrolyte compound exceeds 20 mol / L, the self-discharge of the metal-air battery is accelerated, and the battery characteristics may be deteriorated.
The pH of the electrolytic solution is preferably 7 or more, more preferably 10 or more, and particularly preferably 14 or more.

The metal-air battery has a separator for ensuring the insulation between the air electrode and the negative electrode as necessary. It is preferable that a separator has a porous structure from a viewpoint of hold | maintaining electrolyte solution. The porous structure of the separator is not particularly limited as long as the electrolyte solution can be retained. For example, the separator has a mesh structure in which constituent fibers are regularly arranged, a nonwoven fabric structure in which constituent fibers are randomly arranged, independent holes, and connecting holes. Examples include a three-dimensional network structure. A conventionally well-known thing can be used for a separator. Specific examples include porous films such as polyethylene, polypropylene, polyethylene terephthalate, and cellulose, and nonwoven fabrics such as a resin nonwoven fabric and a glass fiber nonwoven fabric.
The thickness of a separator is not specifically limited, For example, the range of 0.1-400 micrometers is preferable.
The porosity of the separator is preferably 30 to 90%, and more preferably 45 to 70%. If the porosity is too low, ion diffusion tends to be inhibited, and if it is too high, the strength tends to decrease.

A metal-air battery usually has an exterior body that houses an air electrode, a negative electrode, a first electrolyte bath, and the like.
Examples of the shape of the exterior body include a coin type, a flat plate type, a cylindrical type, and a laminate type.
The material of the exterior body is not particularly limited as long as it is stable to the electrolytic solution, but a metal body including at least one selected from the group consisting of Ni, Cr, and Al, and polypropylene, polyethylene, and acrylic resin And the like. When the exterior body is a metal body, only the surface of the exterior body may be composed of a metal body, or the entire exterior body may be composed of a metal body.
The exterior body is open to the atmosphere, has a hole for taking in oxygen from the outside, and has a structure in which at least the air electrode can sufficiently come into contact with the atmosphere. A water repellent film or the like may be provided in the oxygen uptake hole.
The water repellent film is not particularly limited as long as the electrolyte does not leak and the air can reach the air electrode. Examples of the water repellent film include porous fluororesin sheets (PTFE and the like), porous cellulose subjected to water repellent treatment, and the like.
Usually, air is used as the oxygen-containing gas supplied to the air electrode.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Reference example

[Reference Example 1]
An Al plate (manufactured by Niraco Co., Ltd.) having a purity of 99.5%, 10 mm × 10 mm × 1 mm was prepared. Next, 20 cc of 1 mol / L NaOH (made by Kanto Chemical Co., Inc.) aqueous solution was prepared as electrolyte solution.
FIG. 5 shows an Al plate immersed in an electrolytic solution, covered with parafilm for suppressing volatilization, punched with a needle for removing hydrogen, and left overnight at 25 ° C. FIG. 6 shows that the generation of bubbles was confirmed, a transparent solution supernatant was extracted, temperature-controlled at 0 ° C., and left overnight.
As shown in FIG. 5 and FIG. 6, the saturated concentration decreases by cooling and precipitates are deposited.
From the above results, it was confirmed that the precipitate can be preferentially deposited by cooling the electrolytic solution.

DESCRIPTION OF SYMBOLS 10 ... Metal-air battery 11 ... Negative electrode 12 ... Air electrode 13 ... 1st electrolyte solution tank 14 ... Electrolyte solution 15 ... Negative electrode collector 16 ... Air electrode collector 17 ... Exterior body 18 ... Water-repellent film 21 ... Circuit 22 2nd electrolyte bath 23 ... Pump 31 ... Metal filter 32 ... Housing part 33 ... Extraction part 41 ... Cooling part 51 ... Deposit 100 ... Metal-air battery system

Claims (1)

The air electrode,
A negative electrode,
An electrolyte solution serving as an ion conduction path between the air electrode and the negative electrode;
A first electrolyte bath and a second electrolyte bath containing the electrolyte;
A circulation path through which the electrolytic solution circulates between the first electrolytic solution tank and the second electrolytic solution tank;
The negative electrode has a metal that becomes a metal ion or a metal compound in the electrolyte as the discharge reaction of the battery proceeds,
The first electrolyte bath includes the air electrode and the negative electrode,
The second electrolytic solution tank includes a metal filter that is detachably provided, and a cooling unit that cools the metal filter.