JP6255423B2 - Metal air battery - Google Patents

Description

  The present invention relates to a metal-air battery.

Since metal-air batteries have high energy density, they are attracting attention as next-generation batteries. A metal-air battery generates electricity by using a metal electrode containing an electrode active material and being disposed in an electrolyte as an anode and an air electrode as a cathode.
As a typical metal-air battery, a zinc-air battery using metal zinc as an electrode active material can be mentioned. In a zinc-air battery, it is considered that an electrode reaction of the following chemical formula 1 proceeds at the cathode.
(Chemical formula 1): O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
Further, it is considered that an electrode reaction as represented by the following chemical formula 2 proceeds at the anode.
(Chemical formula 2): Zn + 4OH ⁻ → Zn (OH) ₄ ²⁻ + 2e ⁻

When such an electrode reaction proceeds, the electrode active material of the metal electrode is consumed and gradually decreases. In addition, the concentration of metal-containing ions (Zn (OH) ₄ ²⁻ ) in the electrolyte solution gradually increases, and when saturation is reached, a reaction such as the following chemical formula 3 or chemical formula 4 proceeds and uniform nucleation or Heterogeneous nucleation occurs. Then, as the produced nucleus grows, a metal oxide or metal hydroxide precipitate is deposited and accumulated in the electrolytic solution tank as a used active material.
(Chemical formula 3): Zn (OH) ₄ ²⁻ → ZnO + 2OH ⁻ + H ₂ O
(Chemical formula 4): Zn (OH) ₄ ²⁻ → Zn (OH) ₂ + 2OH ⁻
Moreover, the metal electrode after the electrode active material is consumed is replaced with a new metal electrode (see, for example, Patent Document 1).

JP 2005-509262 A

However, in the conventional metal-air battery, the used active material may be deposited as a passive film on the surface of the metal electrode, the anode reaction may be inhibited, and the output of the metal-air battery may be reduced. In this case, since the output of the metal-air battery is lowered with a large amount of the electrode active material remaining on the metal electrode, the utilization efficiency of the electrode active material is lowered.
The present invention has been made in view of such circumstances, and can prevent a used active material from being deposited as a passive film on the surface of a metal electrode, and can be a metal with high utilization efficiency of an electrode active material. An air battery is provided.

  The present invention relates to an electrolytic bath that contains an electrolytic solution, a metal electrode that is provided in the electrolytic bath and has an electrode active material and serves as an anode, an air electrode that serves as a cathode, and physical properties of the electrolytic solution. The metal-air battery is characterized in that the control means controls the ion concentration of the electrolyte based on the physical property value measured by the measurement part.

  According to the present invention, a metal tank includes an electrolyte tank that contains an electrolyte, a metal electrode that is provided in the electrolyte tank and has an electrode active material and serves as an anode, and an air electrode that serves as a cathode. The anode reaction can proceed at the electrode, and the cathode reaction can proceed at the air electrode. Thereby, an electromotive force can be generated between the metal electrode and the air electrode, and a discharge current can flow.

According to the present invention, since the control means for controlling the ion concentration of the electrolytic solution is provided, the ion concentration of the electrolytic solution accommodated in the electrolytic solution tank can be controlled by the control means.
The control means is not particularly limited as long as the ion concentration of the electrolytic solution can be controlled. For example, a switch that switches on / off of the discharge current, a precipitation promoting mechanism that accelerates the precipitation reaction of the precipitate generated from the electrode active material An electrolyte exchange mechanism, an electrolyte solution, water or electrolyte supply mechanism, and an electrodeposition mechanism for electrodepositing a metal as an electrode active material.
Since the discharge current flows with the progress of the anode reaction and the cathode reaction, the anode reaction and the cathode reaction can be controlled by switching the discharge current on and off with a switch. In the anode reaction, hydroxide ions are consumed and metal-containing ions are generated. In the cathode reaction, hydroxide ions are generated. For this reason, the metal-containing ion concentration and the hydroxide ion concentration can be controlled by controlling the discharge current using a switch.
Further, in the precipitation reaction of the precipitate generated from the electrode active material, metal-containing ions are consumed and hydroxide ions are generated. For this reason, the metal-containing ion concentration and the hydroxide ion concentration can be controlled by adjusting the acceleration of the precipitation reaction of the precipitate using the precipitation promoting mechanism.
When the electrolyte in the electrolyte bath is replaced with a new electrolyte, the metal-containing ion concentration and hydroxide ion concentration of the electrolyte in the electrolyte bath are changed from the ion concentration of the electrolyte before replacement to a new electrolysis solution. It can be changed to the ionic concentration of the liquid. For this reason, it is possible to control the metal-containing ion concentration and the hydroxide ion concentration of the electrolytic solution in the electrolytic solution tank by exchanging the electrolytic solution using the electrolytic solution exchange mechanism.
In addition, when a new electrolytic solution, water, or electrolyte is supplied into the electrolytic solution tank, the metal-containing ion concentration and the hydroxide ion concentration of the electrolytic solution in the electrolytic solution tank change. For this reason, the metal-containing ion concentration and the hydroxide ion concentration can be controlled by adjusting the supply of the electrolyte solution, water, or electrolyte using the electrolyte solution, water, or electrolyte supply mechanism.
Further, when a voltage is applied to the electrode disposed in the electrolytic solution to deposit a metal as an electrode active material, metal-containing ions are consumed. For this reason, metal-containing ion density | concentration is controllable by electrodepositing using the electrodeposition mechanism which electrodeposits the metal which is an electrode active material.

According to the present invention, since the measurement unit that measures the physical property value of the electrolytic solution is provided, the physical property value such as the pH value, conductivity, viscosity, or density of the electrolytic solution can be measured by the measurement unit. Since the physical property values such as pH value, conductivity, viscosity or density of the electrolytic solution have a correlation with the metal-containing ion concentration, hydroxide ion concentration, etc. of the electrolytic solution, the physical property value of the electrolytic solution is measured by the measuring unit. As a result, the metal-containing ion concentration and hydroxide ion concentration of the electrolytic solution can be indirectly measured.
According to the present invention, since the control means controls the ion concentration of the electrolytic solution based on the physical property value measured by the measuring unit, the electrolysis is performed so that the metal-containing ion concentration and the hydroxide ion concentration are within a predetermined range. The ion concentration of the liquid can be controlled.

  In addition, the present inventors have found that the metal-containing ion concentration becomes excessive due to changes in the metal-containing ion concentration and hydroxide ion concentration of the electrolyte accompanying the progress of the battery reaction, and the hydroxide ion concentration is necessary for the anode reaction. It has been found that when the concentration is below the concentration, the used active material is deposited as a passive film on the surface of the metal electrode to inhibit the anode reaction. Therefore, according to the present invention, the ion concentration of the electrolytic solution can be controlled so that the metal-containing ion concentration and the hydroxide ion concentration do not become the concentration at which the passive film is deposited, and the passive film Can be prevented from inhibiting the anode reaction. Thereby, it is possible to prevent the output of the metal-air battery from being lowered, and the utilization efficiency of the electrode active material can be increased.

It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a flowchart for controlling the metal air battery of one Embodiment of this invention. It is a graph which shows the fluctuation | variation of the metal containing ion concentration of the electrolyte solution in the electrolyte solution tank contained in the metal air battery of one Embodiment of this invention. It is a graph which shows the fluctuation | variation of the hydroxide ion concentration of the electrolyte solution in the electrolyte solution tank contained in the metal air battery of one Embodiment of this invention. It is a flowchart for controlling the metal air battery of one Embodiment of this invention. It is a flowchart for controlling the metal air battery of one Embodiment of this invention. It is a graph which shows the fluctuation | variation of the metal containing ion concentration of the electrolyte solution in the electrolyte solution tank contained in the metal air battery of one Embodiment of this invention. It is a flowchart for controlling the metal air battery of one Embodiment of this invention. It is a flowchart for controlling the metal air battery of one Embodiment of this invention. It is a graph which shows the result of a discharge experiment. (A) and (b) are photographs of the metal electrodes used in the discharge experiment.

  The metal-air battery of the present invention includes an electrolytic bath that contains an electrolytic solution, a metal electrode that is provided in the electrolytic bath and has an electrode active material and serves as an anode, an air electrode that serves as a cathode, and the electrolytic bath. A measurement unit that measures a physical property value of the liquid and a control unit are provided, and the control unit controls the ion concentration of the electrolytic solution based on the physical property value measured by the measurement unit.

In the metal-air battery of the present invention, it is preferable that the measurement unit measures at least one of pH value, conductivity, viscosity, and density.
According to such a configuration, the ion concentration of the electrolytic solution can be indirectly measured.
In the metal-air battery of the present invention, the control means includes a switch for switching on / off a discharge current, a precipitation promoting mechanism for promoting a precipitation reaction of a precipitate generated from the electrode active material, and an electrolyte exchange mechanism. It is preferable to include at least one of an electrolyte solution, water or electrolyte supply mechanism and an electrodeposition mechanism for electrodepositing a metal as the electrode active material.
According to such a configuration, the ion concentration of the electrolytic solution can be controlled.

In the metal-air battery of the present invention, the deposition promoting mechanism stirs the electrolytic solution, a circulation flow path for circulating the electrolytic solution, a precipitation portion that contacts the substance that promotes the precipitation reaction, and the electrolytic solution. It is preferable that at least one of a stirring unit, an ultrasonic vibration unit that applies ultrasonic waves to the electrolytic solution, and a heating unit that heats the electrolytic solution.
According to such a configuration, the precipitation reaction of the precipitate can be promoted. Further, the ion concentration of the electrolytic solution can be controlled by adjusting the precipitation promoting mechanism.
The metal-air battery of the present invention preferably further includes a control unit that inputs the physical property value measured by the measurement unit as an input signal and outputs an output signal calculated based on the input signal to the control means.
According to such a structure, the ion concentration of electrolyte solution can be controlled based on the physical property value which the control means measured by the measurement part.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

Configuration of Metal-Air Battery FIGS. 1 to 7 are schematic cross-sectional views of the metal-air battery of this embodiment.
The metal-air battery 30 of the present embodiment includes a first electrolytic solution tank 2 that contains the electrolytic solution 3, a metal electrode 5 that is provided in the first electrolytic solution tank 2, has an electrode active material, and serves as an anode, An air electrode 9 serving as a cathode, a measurement unit 24 that measures a physical property value of the electrolytic solution 3, and a control unit 15, and the control unit 15 is based on the physical property value measured by the measurement unit 24 and the ion concentration of the electrolytic solution. It is characterized by controlling.
Hereinafter, the metal-air battery 30 of this embodiment will be described.

1. Metal-air battery The metal-air battery 30 of the present embodiment is a battery in which the metal electrode 5 containing a metal serving as an electrode active material is a negative electrode (anode) and the air electrode 9 is a positive electrode (cathode). For example, a zinc air battery, a lithium air battery, a sodium air battery, a calcium air battery, a magnesium air battery, an aluminum air battery, and an iron air battery. Further, the metal-air battery 30 of the present embodiment may be a primary battery.
The metal-air battery 30 has a metal-air battery body composed of the electrolytic solution tank 2, the air electrode 9 and the like, and a structure that can be attached to and detached from the metal-air battery body. You may comprise from an electrode holder.

2. Cell The cell is a structural unit of the metal-air battery 30, and has an electrode pair that is provided in the electrolytic solution tank 2 (electrolytic solution chamber) and includes a metal electrode 5 serving as an anode and an air electrode 9 serving as a cathode. The cell may have, for example, an electrode pair in which one air electrode 9 and one metal electrode 5 are provided so as to sandwich the electrolytic solution 3, and 2 cells like the metal-air battery 30 shown in FIG. One air electrode 9 may have an electrode pair provided so as to sandwich one metal electrode 5.
The cell may include an electrolytic solution tank 2 or an electrolytic solution chamber, a metal electrode 5 provided in the electrolytic solution tank 2 or the electrolytic solution chamber and serving as an anode, and an air electrode 9 serving as a cathode.

3. Cell assembly The cell assembly has a stack structure in which a plurality of cells are stacked. In the cell assembly, a plurality of cells may be provided in one electrolytic solution tank 2, and each cell may have the electrolytic solution tank 2 or the electrolytic solution chamber. The number of cells constituting the cell assembly is not particularly limited, and the number of cells may be determined according to the required power generation capacity.
In addition, when a plurality of cells constituting the cell assembly each have the electrolytic solution tank 2, the electrolytic solution tank 2 included in each cell may be provided in a common housing 1, and each cell has the housing 1. The casing 1 may be provided with an electrolytic solution tank 2.
Note that two or three cells may be provided in one casing 1, and a plurality of such casings 1 may be combined to form a cell aggregate.
The electrode pairs of a plurality of cells included in the cell assembly may be connected in series or in parallel.

4). Electrolytic Solution, First Electrolytic Solution Tank The electrolytic solution 3 is a liquid having ionic conductivity by dissolving an electrolyte in a solvent. The electrolytic solution 3 is stored in the first electrolytic solution tank 2 or circulates in the first electrolytic solution tank 2. The type of the electrolytic solution 3 is different depending on the type of the electrode active material contained in the metal electrode 5, but may be an electrolytic solution (aqueous electrolyte solution) using a water solvent.
In addition, the electrolytic solution 3 is a measurement target of the measurement unit 24.
For example, in the case of a zinc-air battery, an aluminum-air battery, or an iron-air battery, an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used as the electrolytic solution. An aqueous sodium chloride solution can be used.

The first electrolytic solution tank 2 is an electrolytic cell that stores or distributes the electrolytic solution 3 and has corrosion resistance to the electrolytic solution. The first electrolytic solution tank 2 can have an electrolytic solution chamber.
The first electrolytic solution tank 2 or the electrolytic solution chamber has a structure in which the metal electrode 5 can be installed so that it can be taken out. The 1st electrolyte solution tank 2 can be provided in a metal air battery main body. The first electrolyte bath 2 may have a plurality of electrolyte chambers.

The metal-air battery 30 may have a mechanism for causing the electrolyte 3 in the first electrolyte tank 2 to flow. As a result, the anode reaction at the metal electrode 5 can be promoted, and the performance of the metal-air battery 30 can be improved. As a mechanism for flowing the electrolytic solution, for example, the electrolytic solution 3 is circulated using the pump 25, the second electrolytic solution tank 18, and the electrolytic solution flow path 29, and the electrolytic solution 3 in the first electrolytic solution tank 2 is caused to flow. May be. This fluidizing mechanism can also function as a precipitation promoting mechanism 6 described later.
Moreover, the metal air battery 30 may be provided with the stirring part 32 which moves the electrolyte solution 3 in the electrolyte tank 2 physically, such as a stirrer and a vibrator. The stirring unit 32 can also function as a precipitation promoting mechanism 6 described later.

  The material of the housing 1 constituting the first electrolytic solution tank 2 is not particularly limited as long as it is a material having corrosion resistance to the electrolytic solution. For example, polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyacetic acid Vinyl, ABS, vinylidene chloride, polyacetal, polyethylene, polypropylene, polyisobutylene, fluorine resin, epoxy resin, and the like.

5. Metal electrode The metal electrode 5 is an electrode that serves as an anode, and includes a metal that is an electrode active material of the anode. Moreover, the metal electrode 5 can be provided in the 1st electrolyte solution tank 2 so that extraction is possible.
The metal electrode 5 may be, for example, a metal plate containing a metal that is an electrode active material. In addition, the metal electrode 5 may include, for example, a metal electrode current collector and an electrode active material layer provided on the metal electrode current collector.
The electrode active material contained in the metal electrode 5 is a metal that generates a charge in the metal electrode 5 by an anodic reaction and dissolves in the electrolyte as metal-containing ions. In the case of a zinc-air battery, the anode reaction proceeds as shown in Chemical Formula 2 above. For this reason, the electrode active material contained in the metal electrode 5 is gradually consumed as the anode reaction proceeds. When the electrode active material contained in the metal electrode 5 decreases, the charge generated in the metal electrode 5 decreases and the metal electrode 5 is used. By removing the used metal electrode 5 from the first electrolyte tank 2 and inserting a new metal electrode 5 into the first electrolyte tank 2, power generation by the metal-air battery 30 can be continued.
The charge generated in the metal electrode 5 is output to the outside as a discharge current and then used for the cathode reaction in the air electrode 9. This discharge current may be measured by an ammeter, a voltmeter or the like.

When metal-containing ions are generated by the anodic reaction, the metal-containing ion concentration of the electrolytic solution 3 gradually increases, and when the metal-containing ion concentration exceeds the saturation concentration, fine particles of metal oxide or metal hydroxide in the electrolytic solution 3 Precipitate as (Precipitate 17). For example, in the case of a zinc-air battery, this precipitation reaction proceeds as shown in Chemical Formulas 3 and 4 above.
Therefore, the metal-containing ion concentration gradually increases until the metal-containing ion concentration reaches the saturation concentration. Further, since the amount of hydroxide ions consumed by the anode reaction as represented by the chemical formula 2 is larger than the amount of hydroxide ions supplied by the cathode reaction as represented by the chemical formula 1, the hydroxide ion concentration (OH ^- ion concentration) gradually decreases.

When the metal-containing ion concentration is equal to or higher than the saturation concentration, a precipitation reaction (hereinafter, referred to as a normal precipitation reaction) in which the particulate precipitate 17 is precipitated in the electrolytic solution as represented by the above chemical formulas 3 and 4 proceeds. However, the reaction rate of this normal precipitation reaction is considered to be very slow, and even when the metal-containing ion concentration exceeds the saturation concentration, the metal-containing ion concentration increases and the electrolytic solution becomes supersaturated. Further, since the reaction rate of this precipitation reaction is slow, the OH ⁻ ion concentration decreases.
In the supersaturated state, when the metal-containing ion concentration becomes excessive and the OH ⁻ ion concentration falls below the concentration required for the anode reaction, the used active material is deposited as a passive film on the surface of the metal electrode. (Hereinafter referred to as a passive film deposition reaction) proceeds to inhibit the anode reaction. The concentration at which this used active material precipitates as a passive film is referred to as a “threshold for forming a passive film”.
Accordingly, the precipitate 17 is deposited as a deposition reaction (usually a deposition reaction) that precipitates as fine particles that float in the electrolyte or settles at the bottom of the electrolyte bath, and a passive film that adheres to the surface of the metal electrode 5. And a deposition reaction (passive film deposition reaction).
As described above, there is a correlation between the metal-containing ion concentration and the OH ⁻ ion concentration of the electrolytic solution.

Usually, the precipitate 17 is precipitated as fine particles by the precipitation reaction, and if these fine particles are excessively present in the electrolyte solution 3 in the vicinity of the metal electrode 5, the ion conduction path of OH ⁻ ions is hindered, and the ionic conductivity between the anode and the cathode is reduced. Decreases, and the output of the metal-air battery 30 decreases. For this reason, when the fine particles of the precipitate 17 accumulate in the first electrolytic solution tank 2, it is necessary to remove the fine particles from the first electrolytic solution tank 2.
When the precipitate 17 is deposited as a passive film by the passive film deposition reaction, and this passive film covers most of the surface of the metal electrode 5, the anode reaction on the surface of the metal electrode 5 is inhibited, and the metal-air battery 30. Output decreases. For this reason, it is possible to continue the power generation by the metal-air battery 30 by removing the metal electrode 5 whose surface is covered with the passive film from the electrolytic solution tank 2 and inserting a new metal electrode 5 into the electrolytic solution tank 2. . However, since a large amount of electrode active material often remains on the metal electrode 5 whose surface is covered with the passive film, the utilization efficiency of the electrode active material decreases.
The passive film deposition reaction is considered to proceed electrochemically because the precipitate 17 occurs so as to cover the metal electrode 5.

For example, in the case of a zinc-air battery, the electrode active material is metallic zinc, and zinc hydroxide or zinc oxide is deposited in the electrolytic solution. In the case of an aluminum air battery, the electrode active material is metallic aluminum, and aluminum hydroxide is deposited in the electrolytic solution. In the case of an iron-air battery, the electrode active material is metallic iron, and iron oxide hydroxide or iron oxide is deposited in the electrolytic solution. In the case of a magnesium air battery, the electrode active material is metallic magnesium, and magnesium hydroxide is deposited in the electrolyte.
In the case of lithium-air batteries, sodium-air batteries, and calcium-air batteries, the electrode active materials are metallic lithium, metallic sodium, and metallic calcium, respectively, and oxides and hydroxides of these metals are contained in the electrolyte. Precipitate. In the case of a lithium air battery, a sodium air battery, or a calcium air battery, a solid electrolyte membrane may be provided between the metal electrode 5 and the electrolytic solution. Thereby, it can suppress that an electrode active material is corroded by electrolyte solution. In this case, the electrode active material is dissolved in the electrolytic solution after ion conduction through the solid electrolyte membrane.
In addition, an electrode active material is not limited to these examples, What is necessary is just a metal air battery. Moreover, although the electrode active material contained in the metal electrode 5 mentioned the metal which consists of a kind of metal element in said example, the electrode active material contained in the metal electrode 5 may be an alloy.

The metal electrode current collector has conductivity. Further, the shape of the metal electrode current collector is preferably a plate shape, a shape provided with a hole penetrating in the thickness direction of the plate, an expanded metal or a mesh. In addition, the metal electrode current collector can be formed of, for example, a metal having corrosion resistance against the electrolytic solution. The material of the metal electrode current collector is, for example, nickel, gold, silver, copper, stainless steel or the like. The metal electrode current collector may be a nickel-plated, gold-plated, silver-plated, or copper-plated conductive substrate. For this conductive substrate, iron, nickel, stainless steel, or the like can be used.
As a result, the charge generated in the metal electrode 5 by the anode reaction can be collected by the metal electrode current collector, and the generated charge can be output to an external circuit. The electrode active material layer may be fixed on the main surface of the metal electrode current collector, for example, by pressing metal particles or lumps that are electrode active materials against the surface of the metal electrode current collector. A metal may be deposited on the current collector by plating or the like. Regarding the shape of the metal electrode current collector, the plate shape is preferable from the viewpoint of conductivity when the electrode active material is deposited by plating, and when the metal particles or lump is fixed, the particles or lump is dropped. From the viewpoint of preventing this, a plate provided with a through hole, or an expanded metal or mesh is preferable.

The metal electrode 5 can constitute a metal electrode holder together with the metal electrode support. The metal electrode holder is provided so that the metal electrode 5 can be inserted into the electrolytic solution tank 2 and the used metal electrode 5 can be extracted from the first electrolytic solution tank 2. Thus, the electrode active material can be supplied to the metal-air battery 30 by replacing the metal electrode 5.
A metal electrode support body can be provided so that it may become a lid | cover of the electrode insertion port provided in the metal air battery main body. Thus, the metal electrode 5 can be inserted into the first electrolytic solution tank 2 and the electrode insertion port can be covered, and the reaction between the components in the atmosphere and the electrolytic solution 3 can be suppressed.

6). Air electrode The air electrode 9 is an electrode having an air electrode catalyst and serving as a cathode. Further, the air electrode 9 may include a porous gas diffusion layer 8 and a porous air electrode catalyst layer 7 provided on the gas diffusion layer 8. In the air electrode 9, water supplied from the electrolytic solution 3 and the like, oxygen gas supplied from the atmosphere, and electrons react on the air electrode catalyst to generate hydroxide ions (OH ⁻ ) (cathode reaction). That is, the cathode reaction as shown in Chemical Formula 1 proceeds at the three-phase interface of the air electrode 9.
The air electrode 9 is provided so that oxygen gas contained in the atmosphere can diffuse into the air electrode 9. For example, the air electrode 9 can be provided so that at least a part of the surface of the air electrode 9 is exposed to the atmosphere. In the metal-air battery 30 shown in FIG. 1, a plurality of holes 23 are provided in the housing 1, and oxygen gas contained in the atmosphere can diffuse into the air electrode 9 through the holes 23. Further, for example, an air flow path through which air flows may be formed and oxygen gas may be supplied to the air electrode 9. Note that water may be supplied to the air electrode 9 through this air flow path.

The air electrode catalyst layer 7 may include, for example, a conductive porous carrier and an air electrode catalyst supported on the porous carrier. This makes it possible to form a three-phase interface in which oxygen gas, water, and electrons coexist on the air electrode catalyst, thereby allowing the cathode reaction to proceed. The air electrode catalyst layer 7 may contain a binder.
The air electrode 9 composed of the air electrode catalyst layer 7 and the gas diffusion layer 8 is produced by applying a porous carrier carrying the air electrode catalyst to the conductive porous substrate (gas diffusion layer 8). May be. For example, the air electrode 9 can be produced by applying carbon carrying an air electrode catalyst to carbon paper or carbon felt. The gas diffusion layer 8 may function as an air electrode current collector.
The thickness of the air electrode 9 can be, for example, not less than 300 μm and not more than 3 mm.
The air electrode 9 can be electrically connected to the air electrode terminal 10. Thereby, the electric charge generated in the air electrode catalyst layer 7 can be taken out to the external circuit.

The metal-air battery 30 may include an air electrode current collector that collects charges generated in the air electrode catalyst layer 7. As a result, charges generated in the air electrode catalyst layer 7 can be efficiently taken out to the external circuit. The material of the air electrode current collector is not particularly limited as long as it has corrosion resistance with respect to the electrolytic solution 3, and examples thereof include nickel, gold, silver, copper, and stainless steel. The air electrode current collector may be a nickel-plated, gold-plated, silver-plated, or copper-plated conductive substrate. For this conductive substrate, iron, nickel, stainless steel, or the like can be used.
The shape of the air electrode current collector can be, for example, a plate shape, a mesh shape, a punching metal, an expanded metal, a porous body, a foam, or the like.
In addition, as a method of joining the air electrode current collector and the porous carrier or the conductive porous substrate (gas diffusion layer 8), a method of pressure bonding by screwing through a frame, or a conductive adhesive can be used. The method of using and combining is mentioned.

The air electrode 9 included in one cell may be provided only on one side of the metal electrode 5, or may be provided on both sides of the metal electrode 5 as shown in FIG.
Examples of the porous carrier contained in the air electrode catalyst layer 7 include carbon black such as acetylene black, furnace black, channel black and ketjen black, and conductive carbon particles such as graphite and activated carbon. In addition, carbon fibers such as vapor grown carbon fiber (VGCF), carbon nanotube, carbon nanowire, and the like can be used.
Examples of the air electrode catalyst include fine particles made of platinum, iron, cobalt, nickel, palladium, silver, ruthenium, iridium, molybdenum, manganese, lanthanum, these metal compounds, and alloys containing two or more of these metals. Can be mentioned. This alloy is preferably an alloy containing at least two of platinum, iron, cobalt and nickel. For example, platinum-iron alloy, platinum-cobalt alloy, iron-cobalt alloy, cobalt-nickel alloy, iron-nickel alloy And iron-cobalt-nickel alloy.
The binder contained in the air electrode catalyst layer 7 is, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).
Further, the porous carrier contained in the air electrode catalyst layer 7 may be subjected to a surface treatment so that a cationic group exists as a fixed ion on the surface thereof. As a result, hydroxide ions can be conducted on the surface of the porous carrier, so that the hydroxide ions generated on the air electrode catalyst can easily move.
The air electrode catalyst layer 7 may have an anion exchange resin supported on a porous carrier. Thereby, since hydroxide ions can be conducted through the anion exchange resin, the hydroxide ions generated on the air electrode catalyst are easily moved.

  The air electrode catalyst layer 7 may be provided so as to be in contact with the electrolytic solution 3 in the first electrolytic solution tank 2. Thus, hydroxide ions generated in the air electrode catalyst layer 7 can easily move to the electrolyte solution 3. Further, water necessary for the electrode reaction in the air electrode catalyst layer 7 is easily supplied from the electrolytic solution 3 to the air electrode catalyst layer 7.

  Further, the air electrode catalyst layer 7 may be provided so as to be in contact with the separator 14 that is in contact with the electrolytic solution 3 accommodated in the first electrolytic solution tank 2. The separator 14 can be a porous resin membrane, an ion exchange membrane or a nonwoven fabric of resin fibers. The separator 14 can be provided so as to partition the electrolytic solution 3 in the electrolytic solution tank 2 and the air electrode catalyst layer 7. By providing the separator 14, the electrolyte 3 can be prevented from leaking outside the metal-air battery 30 through the pores of the air electrode 9, and the safety of the metal-air battery 30 can be improved. . Moreover, since the water contained in the electrolytic solution 3 penetrates into the air electrode 9 after passing through the separator 14, it is possible to suppress excess water from being supplied to the air electrode 9. In addition, by providing the separator 14, it is possible to prevent the electrode active material contained in the electrolytic solution 3 and the extremely fine particles of the precipitate 17 from adhering to the air electrode catalyst layer 7.

  Moreover, the ion species which move between the air electrode catalyst layer 7 and the electrolyte solution 3 can be limited by making the separator 14 into an ion exchange membrane. The separator 14 may be an anion exchange membrane. As a result, hydroxide ions generated in the air electrode catalyst layer 7 can conduct through the anion exchange membrane and move to the electrolytic solution. Since the anion exchange membrane has a cation group which is a fixed ion, the cation in the electrolytic solution 3 cannot be conducted to the air electrode catalyst layer 7. On the other hand, since the hydroxide ions generated in the air electrode catalyst layer 7 are anions, they can be conducted to the electrolytic solution 3. As a result, the battery reaction of the metal-air battery 30 can proceed, and the cations in the electrolyte aqueous solution 3 can be prevented from moving to the air electrode catalyst layer 7. Thereby, precipitation of the metal and carbonate compound in the air electrode catalyst layer 7 can be suppressed.

The material of the porous resin film or the nonwoven fabric of resin fibers used for the separator 14 can be an alkali-resistant resin, for example, polyethylene, polypropylene, nylon 6, nylon 66, polyolefin, polyvinyl acetate, polyvinyl alcohol-based material. And polytetrafluoroethylene (PTFE). The pore diameter of the pores of the separator 14 is not particularly limited, but is preferably 30 μm or less. The separator 14 is preferably subjected to a hydrophilic treatment so as to improve the flow of the electrolytic solution.
Examples of the ion exchange membrane used in the separator 14 include perfluorosulfonic acid, perfluorocarboxylic acid, styrene vinylbenzene, and quaternary ammonium solid polymer electrolyte membranes (anion exchange membranes).

7). Switch (control means)
A switch 12 that switches on / off the discharge current of the metal-air battery 30 may be provided. The switch 12 serves as a control unit 15 that controls the ion concentration of the electrolytic solution 3.
The switch 12 can be provided on an electric wire 27 (discharge circuit) that electrically connects the metal electrode 5 and the air electrode 9 like the metal-air battery 30 shown in FIG. As a result, the discharge current can be switched on / off.
The switch 12 is provided so that the controller 4 can be switched on / off. For example, the switch 12 and the control unit 4 are connected by the signal line 28 or wirelessly, and the switch 12 is provided so that it can be switched on / off by an output signal of the control unit 4.

  When the switch 12 is turned on, a discharge current flows between the metal electrode 5 and the air electrode 9, and the charge moves. Therefore, the anode reaction proceeds at the metal electrode 5 and the cathode reaction proceeds at the air electrode 9. When the switch 12 is turned off, the discharge current does not flow between the metal electrode 5 and the air electrode 9 and the charge does not move, so that the anode reaction and the cathode reaction do not proceed. Therefore, the anode reaction and the cathode reaction can be controlled by switching the switch 12 on and off by the control unit 4. In addition, since the anodic reaction or the cathodic reaction involves consumption of metal-containing ions or consumption or generation of hydroxide ions, the ion concentration of the electrolytic solution can be controlled by controlling the switch 12.

For example, when the metal-containing ion concentration is in a supersaturated state, when the switch 12 is turned off to stop the anode reaction and the cathode reaction, the supply of metal-containing ions from the electrode active material is stopped. However, since a normal precipitation reaction in which a metal oxide or a metal hydroxide is generated from a metal-containing ion such as the chemical formulas 3 and 4 proceeds, when the switch 12 is turned off, the metal-containing ion concentration of the electrolytic solution 3 is It gradually decreases and the OH ⁻ ion concentration gradually increases.
When the switch 12 is turned on again, the anode reaction and the cathode reaction proceed, so that the metal-containing ion concentration of the electrolytic solution 3 gradually increases and the OH ⁻ ion concentration gradually decreases.
Therefore, by controlling the switch 12 by the control unit 4, the metal-containing ion concentration and the OH ⁻ ion concentration of the electrolytic solution 3 can be controlled.

8). Measuring Unit The measuring unit 24 is provided so as to measure the physical property value of the electrolytic solution 3. The measurement part 24 may be provided so that the physical property value of the electrolyte solution 3 can be measured in the 1st electrolyte tank 2 like the metal air battery 30 shown in FIG. The electrolytic solution 3 may be sampled so that the physical property value of the electrolytic solution 3 can be measured. Further, when the electrolytic solution 3 in the first electrolytic solution tank 2 is circulated by the electrolytic solution flow path 29 and the pump 25, the measuring unit 24 is provided so that the physical property value of the electrolytic solution 3 can be measured in the electrolytic solution flow path 29. Alternatively, the electrolyte solution 3 in the electrolyte channel 29 may be sampled and the physical property value of the electrolyte solution 3 may be measured.
Further, like the metal-air battery 30 shown in FIG. 1, a second electrolytic solution tank 18 is provided, and the electrolytic solution 3 in the first electrolytic solution tank 2 and the electrolytic solution 3 in the second electrolytic solution tank 18 are circulated. In this case, the measuring unit 24 may be provided so as to measure the physical property value of the electrolytic solution 3 in the second electrolytic solution tank 18. The electrolytic solution 3 is sampled from the electrolytic solution 3 in the second electrolytic solution tank 18. 3 may be provided so that the physical property value of 3 can be measured.
Moreover, you may provide the measurement part 24 in the 1st electrolyte solution tank 2 and the 2nd electrolyte solution tank 18, respectively like the metal air battery 30 shown in FIG.

The measuring unit 24 may use only the electrolytic solution 3 as a measurement target, or may use a mixture of the electrolytic solution 3 and the fine particles of the precipitate 17 as a measurement target.
For example, the measurement unit 24 can measure physical property values such as pH value, ORP, conductivity, viscosity, density, etc., with the electrolytic solution 3 as a measurement target. Further, the measuring unit 24 may be provided to measure other physical property values that are related to the OH ⁻ ion concentration or the metal-containing ion concentration in the electrolytic solution.
Moreover, the measurement part 24 may be provided so that two or more types of physical property values can be measured. The measurement unit 24 is, for example, a pH meter, an ORP meter, a conductivity meter, a viscometer, a density meter, or the like.

  The measurement unit 24 and the control unit 4 can be connected so that the measurement result of the measurement unit 24 is input to the control unit 4 as an input signal. For example, the measurement unit 24 and the control unit 4 can be connected by the signal line 28 or wirelessly. Thus, the control unit 4 can control the control means 15 such as the switch 12 or the precipitation promoting mechanism 6 based on the measurement result of the measurement unit 24.

  The measurement part 24 can be provided so that the pH value of the electrolyte solution 3 can be measured, for example. Moreover, the measurement part 24 may be provided so that ORP of the electrolyte solution 3 can be measured. In this case, the measurement unit 24 is a pH meter or an ORP meter. Moreover, the measurement unit 24 may be a pH meter having a glass electrode, or a pH meter having an ion-responsive field effect transistor. Further, the measuring unit 24 can continuously measure the pH value of the electrolytic solution 3.

The pH value of the electrolytic solution 3 is a value reflecting the OH ⁻ ion concentration of the electrolytic solution 3. For this reason, there is a correlation between the pH value of the electrolytic solution 3 and the OH ⁻ ion concentration. Therefore, when the relationship between the OH ⁻ ion concentration of the electrolytic solution 3 accommodated in the first electrolytic solution tank 2 and the pH value of the electrolytic solution 3 is measured in advance and a calibration curve is created, the measurement result of the measuring unit 24 is obtained. OH of the electrolyte 3 from pH values of the electrolyte solution 3 ^- can be calculated ion concentration, OH ^- it can be indirectly measured ion concentration.
In addition, since there is a correlation between the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution, there is also a correlation between the pH value of the electrolytic solution 3 and the metal-containing ion concentration. Therefore, if the relationship between the pH value of the electrolytic solution 3 and the metal-containing ion concentration is measured in advance and a calibration curve is prepared, the metal-containing ion concentration can be calculated from the pH value of the electrolytic solution 3, The ion concentration can be measured indirectly.
Further, when the pH value corresponding to the threshold value formed by the passive film having the OH ⁻ ion concentration and the metal-containing ion concentration is examined in advance, the control unit 4 switches the switch 12 and the precipitation promoting unit 6 based on the measurement result of the measurement unit 24. By controlling the control means 15 such as the above, it is possible to prevent the metal electrode 5 from being covered with the passive film.

  The measurement part 24 can be provided so that the electrical conductivity of the electrolyte solution 3 can be measured, for example. In this case, the measurement unit 24 may measure the conductivity of the electrolytic solution 3 including the fine particles of the precipitate 17. Moreover, the measurement part 24 may be provided so that electrical conductivity may be measured, for example by the alternating current 2 electrode method, and may be provided so that electrical conductivity may be measured by the electromagnetic induction method.

The conductivity of the electrolytic solution 3 reflects the concentration of ions having the highest transport number in the electrolytic solution. For example, when the electrolytic solution 3 is an alkaline aqueous solution such as an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution, the conductivity of the electrolytic solution 3 reflects the OH ⁻ ion concentration. For this reason, there is a correlation between the conductivity of the electrolytic solution 3 and the OH ⁻ ion concentration. Therefore, when the relationship between the OH ⁻ ion concentration of the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the conductivity of the electrolytic solution 3 is measured in advance and a calibration curve is prepared, the measurement result of the first measuring unit 24 is obtained. OH of the electrolyte 3 from the conductivity of the electrolyte 3 ^- can be calculated ion concentration, OH ^- can be indirectly measured ion concentration.
In addition, since there is a correlation between the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution, there is also a correlation between the conductivity of the electrolytic solution 3 and the metal-containing ion concentration. For this reason, when the relationship between the electrical conductivity of the electrolytic solution 3 and the metal-containing ion concentration is measured in advance and a calibration curve is prepared, the metal-containing ion concentration can be calculated from the electrical conductivity of the electrolytic solution 3, The ion concentration can be measured indirectly.
Further, when the electrical conductivity corresponding to the threshold value formed by the passive film having the OH ⁻ ion concentration and the metal-containing ion concentration is examined in advance, the control unit 4 switches the switch 12 and the precipitation promoting unit 6 based on the measurement result of the measurement unit 24. By controlling the control means 15 such as the above, it is possible to prevent the metal electrode 5 from being covered with the passive film.

  The measurement part 24 can be provided so that the viscosity of the electrolyte solution 3 may be measured, for example. In this case, the measurement unit 24 may measure the viscosity of the electrolytic solution 3 including the fine particles of the precipitate 17. Moreover, the measurement part 24 is a tuning fork vibration type viscometer, for example.

The viscosity of the electrolytic solution 3 is a value that reflects the amount of the heaviest metal-containing ions in the electrolytic solution. In the case of a zinc-air battery, the viscosity of the electrolytic solution 3 is a value that reflects the amount of Zn (OH) ₄ ^2- ion concentration. For this reason, there is a correlation between the viscosity of the electrolytic solution 3 and the metal-containing ion concentration. Therefore, when a relationship between the metal-containing ion concentration of the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the viscosity of the electrolytic solution 3 is measured in advance and a calibration curve is prepared, the electrolytic solution 3 that is a measurement result of the measuring unit 24 is obtained. From this viscosity, the metal-containing ion concentration of the electrolytic solution 3 can be calculated, and the metal-containing ion concentration can be indirectly measured.
Further, since the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution are correlated, there is also a correlation between the viscosity of the electrolytic solution 3 and the OH ⁻ ion concentration. Therefore, viscosity and OH of the electrolyte 3 ^- When you create a previously measured calibration curve the relationship between the ion concentration, OH from the viscosity of the electrolyte 2 ^- can be calculated ion concentration, OH ^- ion concentration Can be measured indirectly.
Further, when the viscosity corresponding to the threshold value formed by the passive film of the OH ⁻ ion concentration and the metal-containing ion concentration is examined in advance, based on the measurement result of the measurement unit 24, the control unit 4 switches the switch 12, the precipitation promoting unit 6 and the like. By controlling the control means 15, it is possible to prevent the metal electrode 5 from being covered with the passive film.

  The measurement part 24 can be provided so that the density of the electrolyte solution 3 may be measured, for example. In this case, the measurement unit 24 may measure the density of the electrolytic solution 3 including the fine particles of the precipitate 17. Moreover, the measurement part 24 is a vibration-type density meter, for example.

The density of the electrolytic solution 3 is a value that reflects the amount of the heaviest metal-containing ions in the electrolytic solution. In the case of a zinc-air battery, the density of the electrolytic solution 3 is a value that reflects the amount of Zn (OH) ₄ ^2- ion concentration. For this reason, there is a correlation between the density of the electrolytic solution 3 and the metal-containing ion concentration. Therefore, when the relationship between the metal-containing ion concentration of the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the density of the electrolytic solution 3 is measured in advance and a calibration curve is created, the electrolysis that is the measurement result of the first measuring unit 24 is obtained. The metal-containing ion concentration of the electrolytic solution 3 can be calculated from the density of the liquid 3, and the metal-containing ion concentration can be indirectly measured.
Further, since the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution are correlated, there is also a correlation between the density of the electrolytic solution 3 and the OH ⁻ ion concentration. Thus, density and OH of the electrolyte 3 ^- When you create a previously measured calibration curve the relationship between the ion concentration, OH from the density of the electrolyte 2 ^- can be calculated ion concentration, OH ^- ion concentration Can be measured indirectly.
Further, when the density corresponding to the threshold value formed by the passive film having the OH ⁻ ion concentration and the metal-containing ion concentration is examined in advance, based on the measurement result of the measurement unit 24, the control unit 4 switches the switch 12, the precipitation promoting unit 6, etc. By controlling the control means 15, it is possible to prevent the metal electrode 5 from being covered with the passive film.

9. Deposition promotion mechanism (control means)
The electrode active material contained in the metal electrode 5 is dissolved in the electrolytic solution 3 as metal-containing ions by an anodic reaction. When the metal-containing ion concentration becomes equal to or higher than the saturation concentration, the metal-containing ions are precipitated as a precipitate 17 by the precipitation reaction as shown in the above chemical formulas 3 and 4 (normally precipitation reaction). However, the reaction rate of this precipitation reaction is considered to be very slow, and the metal-containing ion concentration increases even when the metal-containing ion concentration exceeds the saturation concentration. When the metal-containing ion concentration and the OH ⁻ ion concentration reach the threshold value at which the passive film is formed, the metal-containing ions are considered to precipitate on the surface of the metal electrode 5 as the precipitate 17 that is the passive film (non-conductive). Dynamic membrane deposition reaction).

The precipitation promoting mechanism 6 is a mechanism that normally promotes the precipitation reaction. Since the normal precipitation reaction is a reaction that consumes metal-containing ions and generates OH ^- ions, the ion concentration of the electrolytic solution can be controlled by adjusting the acceleration of the normal precipitation reaction by the precipitation promotion mechanism 6. Therefore, the precipitation promoting mechanism 6 becomes the control means 15.
The precipitation promoting mechanism 6 may promote heterogeneous nucleation or promote crystal growth of crystal nuclei. The precipitation promoting mechanism 6 may be a mechanism that promotes a normal precipitation reaction in the first electrolyte bath 2 like the metal-air battery 30 shown in FIGS. A mechanism that normally promotes the precipitation reaction in the second electrolytic solution tank 18 provided so that the electrolytic solution in the first electrolytic solution tank 2 can flow in like the air battery 30 may be used.
By accelerating the normal precipitation reaction by the precipitation promoting mechanism 6, the reaction rate of the normal precipitation reaction can be increased, the metal-containing ion concentration of the electrolytic solution can be decreased, and the OH ⁻ ion concentration can be increased. Further, by providing the precipitation promoting mechanism 6, it is possible to lengthen the time until the metal-containing ion concentration and the OH ⁻ ion concentration reach the threshold value at which the passive film is formed, and the discharge time of the metal-air battery 30 is lengthened. can do.

Further, the precipitation promoting mechanism 6 is provided to be controlled by the control unit 4. Thus, when the metal-containing ion concentration of the electrolytic solution becomes high, the precipitation promoting mechanism 6 can be operated, and the metal-containing ion concentration can be lowered and the OH ⁻ ion concentration can be raised. Therefore, the control unit 4 can control the ion concentration of the electrolytic solution by controlling the precipitation promoting mechanism 6.
The deposition promoting mechanism 6 includes, for example, a circulation channel for circulating the electrolytic solution, a deposition unit 22 for bringing the substance 20 for promoting deposition into contact with the electrolytic solution 3, a stirring unit 32 for stirring the electrolytic solution 3, and an ultrasonic wave on the electrolytic solution. And an ultrasonic vibration unit 36 for heating, a heating unit 38 for heating the electrolytic solution, and the like.

When the deposition promoting mechanism 6 is a circulation channel for circulating the electrolyte, the deposition promoting mechanism 6 includes, for example, the pump 25, the electrolyte channels 29a and 29b, and the valve 26a included in the metal-air battery 30 shown in FIG. The second electrolyte bath 18 is configured. The pump 25 causes the electrolytic solution 3 in the second electrolytic solution tank 18 to flow into the first electrolytic solution tank 2, opens the valve 26a, and the electrolytic solution 3 in the first electrolytic solution tank 2 enters the second electrolytic solution tank 18. The electrolyte 3 can be circulated by making it flow. When the electrolytic solution 3 is circulated, the heterogeneous nucleation of the precipitate 17 can be promoted by the water flow. When crystal nuclei are generated by heterogeneous nucleation, precipitation of the precipitates 17 can be promoted by crystal growth of the generated crystal nuclei. Therefore, this precipitation promoting mechanism 6 can promote the normal precipitation reaction, and can reduce the metal-containing ion concentration of the electrolytic solution 3.
In addition, although the 2nd electrolyte solution tank 18 is provided in FIG. 1, the 2nd electrolyte solution tank 18 does not need to be provided. In this case, the electrolyte flow paths 29a and 29b are connected. Further, when the connecting portion between the electrolytic solution channel 29b and the first electrolytic solution tank 2 is provided near the liquid surface of the electrolytic solution 3 in the first electrolytic solution tank 2, the valve 26a may not be provided.

In order to control the deposition promoting mechanism 6 by the control unit 4, for example, the pump 25 and the valve 26 a are connected to the control unit 4 by a signal line 28 or wirelessly. The precipitation promoting mechanism 6 is provided so that on / off and opening / closing of the valve 26a can be switched.
For example, the deposition promoting mechanism 6 can be operated by sending a signal for turning on the pump 25 from the control unit 4 to the pump 25 and sending a signal for opening the valve 26a from the control unit 4 to the valve 26a. Further, the deposition promoting mechanism 6 can be stopped by sending a signal for turning off the pump 25 from the control unit 4 to the pump 25 and sending a signal for closing the valve 26a from the control unit 4 to the valve 26a.

In the case where the deposition promoting mechanism 6 is the deposition portion 22 that contacts the substance 20 that promotes deposition and the electrolytic solution 3, the deposition promoting mechanism 6 includes, for example, the pump 25 included in the metal-air battery 30 shown in FIG. The liquid flow paths 29a and 29b, the valve 26a, the second electrolytic solution tank 18, and the precipitation part 22 including the substance 20 that promotes the precipitation are configured.
For example, a signal for turning on the pump 25 is sent from the control unit 4 to the pump 25, and a signal for opening the valve 26a is sent from the control unit 4 to the valve 26a, so that the electrolyte 3 in the first electrolyte bath 2 and the second The electrolytic solution 3 in the electrolytic solution tank 18 can be circulated, and the electrolytic solution 3 can be brought into contact with the substance 20 that promotes deposition. Thereby, the normal precipitation reaction in the precipitation part 22 can be accelerated | stimulated, and the precipitation promotion mechanism 6 can be operated.
Further, the circulation of the electrolytic solution 3 can be stopped by sending a signal for turning off the pump 25 from the control unit 4 to the pump 25 and sending a signal for closing the valve 26a from the control unit 4 to the valve 26a. Thereby, the inflow to the 2nd electrolyte solution tank 18 which provided the precipitation part 22 of the electrolyte solution 3 in the 1st electrolyte solution tank 2 can be stopped, and the precipitation promotion mechanism 6 can be stopped.

In FIG. 1, the precipitation portion 22 is provided in the second electrolyte bath 18, but the precipitation portion 22 may be provided in the first electrolyte bath 2.
Moreover, you may provide the precipitation part 22 so that the substance 20 which accelerates | stimulates precipitation can be added in the electrolyte solution 3 in the 1st electrolyte solution tank 2, or the electrolyte solution 3 in the 2nd electrolyte solution tank 18. FIG. In this case, the precipitation promoting mechanism 6 can be operated by adding the substance 20 that promotes the precipitation, and the addition of the substance 20 that promotes the precipitation is stopped or the substance 20 that promotes the precipitation is pulled up from the electrolytic solution. Thus, the precipitation promoting mechanism 6 can be stopped.

The substance 20 that promotes precipitation can be a substance made of the same metal oxide or the same metal hydroxide as the precipitate 17. For example, when the metal-air battery 30 is a zinc-air battery, the precipitate 17 is made of zinc oxide or zinc hydroxide. Therefore, the substance 20 that promotes precipitation may be, for example, zinc oxide or zinc hydroxide particles. it can.
The same kind of metal oxide or the same kind of metal hydroxide as the precipitate 17 can serve as a crystal nucleus for the precipitate 17 to precipitate. For this reason, by bringing the electrolytic solution 3 into contact with the substance 20 that promotes precipitation, the precipitate 17 can be crystal-grown on the surface of the substance 20 that promotes precipitation, and the reaction rate of the normal precipitation reaction is usually increased. Can do.

  The substance 20 that promotes precipitation can be a porous substance such as alumina, activated carbon, or zeolite. Since the porous material has minute irregularities on the contact surface with the electrolytic solution 3, heterogeneous nucleation tends to occur on the surface of the porous material. For this reason, by bringing the electrolytic solution 3 into contact with the substance 20 that promotes precipitation, heterogeneous nucleation on the surface of the substance 20 that promotes precipitation can be promoted, and the growth of the generated crystal nuclei is promoted. be able to. As a result, the reaction rate of the normal precipitation reaction can be increased.

When the deposition promoting mechanism 6 is the stirring unit 32 that stirs the electrolytic solution 3, the deposition promoting mechanism 6 can be provided, for example, like the metal-air battery 30 shown in FIG. When the electrolytic solution 3 is stirred by the stirring unit 32, the heterogeneous nucleation of the precipitate 17 can be promoted by the water flow. When crystal nuclei are generated by heterogeneous nucleation, precipitation of the precipitates 17 can be promoted by crystal growth of the generated crystal nuclei. Therefore, this precipitation promoting mechanism 6 can promote the normal precipitation reaction, and can reduce the metal-containing ion concentration of the electrolytic solution 3.
In FIG. 3, the first electrolytic solution tank 2 is provided with the stirring unit 32, but the stirring unit 32 is provided with the second electrolytic solution tank 18 provided so that the electrolytic solution in the first electrolytic solution tank 2 flows in. May be provided.
In order to control the precipitation promoting mechanism 6 by the control unit 4, for example, the stirring unit 32 and the control unit 4 are connected by a signal line 28 or wirelessly, and the stirring unit 32 is turned on by an output signal of the control unit 4. Precipitation promoting mechanism 6 is provided so that / off can be switched.

When the deposition promoting mechanism 6 is an ultrasonic vibration unit 36 that applies ultrasonic waves to the electrolytic solution, the deposition promoting mechanism 6 can be provided, for example, like the metal-air battery 30 shown in FIG. When ultrasonic waves are applied to the electrolytic solution 3 by the ultrasonic vibration unit 36, the heterogeneous nucleation of the precipitate 17 can be promoted by the vibration of the electrolytic solution. When crystal nuclei are generated by heterogeneous nucleation, precipitation of the precipitates 17 can be promoted by crystal growth of the generated crystal nuclei. Therefore, this precipitation promoting mechanism 6 can promote the normal precipitation reaction, and can reduce the metal-containing ion concentration of the electrolytic solution 3.
In FIG. 4, the ultrasonic vibration unit 36 is provided so as to apply ultrasonic waves to the electrolytic solution in the first electrolytic solution tank 2, but the ultrasonic vibration unit 36 is an electrolytic solution in the first electrolytic solution tank 2. May be provided so as to apply ultrasonic waves to the electrolytic solution in the second electrolytic solution tank 18 provided to flow in.
In order to control the precipitation promoting mechanism 6 by the control unit 4, for example, the ultrasonic vibration unit 36 and the control unit 4 are connected by a signal line 28 or wirelessly, and the ultrasonic vibration is generated by an output signal of the control unit 4. The precipitation promoting mechanism 6 is provided so that the on / off of the part 36 can be switched.

When the deposition promoting mechanism 6 is the heating unit 38 that heats the electrolytic solution, the deposition promoting mechanism 6 can be provided, for example, like the metal-air battery 30 shown in FIG. When the electrolytic solution 3 is heated by the heating unit 38, the precipitation of the precipitate 17 can be promoted. Therefore, this precipitation promoting mechanism 6 can promote the normal precipitation reaction, and can reduce the metal-containing ion concentration of the electrolytic solution 3.
In FIG. 5, the heating unit 38 is provided so as to heat the electrolytic solution in the first electrolytic solution tank 2, but the heating unit 38 is provided so that the electrolytic solution in the first electrolytic solution tank 2 flows in. You may provide so that the electrolyte solution in the obtained 2nd electrolyte solution tank 18 may be heated.
In order to control the precipitation promoting mechanism 6 by the control unit 4, for example, the heating unit 38 and the control unit 4 are connected by a signal line 28 or wirelessly, and the heating unit 38 is turned on by an output signal of the control unit 4. Precipitation promoting mechanism 6 is provided so that / off can be switched.

10. Electrodeposition mechanism (control means)
The metal-air battery 30 of this embodiment can have an electrodeposition mechanism for electrodepositing a metal that is an electrode active material of the anode. The electrodeposition mechanism may include a first electrode 43 for electrodeposition on which metal as an electrode active material is deposited and a second electrode 44 for electrodeposition that is a counter electrode of the electrode 43 for first electrodeposition. it can. In addition, the electrodeposition mechanism may include a power supply unit 42 that applies a voltage between the first electrodeposition electrode 43 and the second electrodeposition electrode 44. The electrodeposition mechanism is provided such that an electrode reaction in which the metal-containing ions in the electrolytic solution are consumed and the metal as the electrode active material is deposited on the surface of the first electrodeposition electrode 43 proceeds.
According to such an electrodeposition mechanism, a voltage is applied between the first electrodeposition electrode 43 and the second electrodeposition electrode 44 by the power supply unit 42, whereby the metal is used as the raw material for the first metal. It can be deposited on the electrode 43 for electrodeposition, and the metal-containing ion concentration of the electrolytic solution can be reduced. Therefore, the metal-containing ion concentration of the electrolytic solution 3 can be controlled by adjusting the electrodeposition by the electrodeposition mechanism. Therefore, the electrodeposition mechanism becomes the control means 15.
In order to control this electrodeposition mechanism by the control unit 4, for example, a switch or power supply unit 42 provided on an electric wire between the power supply unit 42 and the first or second electrodeposition electrode 43, 44, and the control unit 4 is connected by a signal line 28 or wirelessly, and an electrodeposition mechanism is provided so that the power supply unit 42 or the switch can be switched on / off by an output signal of the control unit 4.

For example, when the metal-air battery 30 is a zinc-air battery, by applying a voltage from the power supply unit 42, an electrode reaction as shown in the following chemical formula 5 proceeds in the first electrode 43 for electrodeposition, and the second electrodeposition. An electrodeposition mechanism can be provided so that an electrode reaction of the following chemical formula 6 proceeds in the working electrode 44.
(Chemical formula 5): 2Zn (OH) ₄ ²⁻ + 4e ⁻ → 2Zn + 8OH ⁻
(Chemical formula 6): 4OH ⁻ → O ₂ + 2H ₂ O + 4e ⁻

The metal electrode 5 may be the first electrode 43 and the air electrode 9 may be the second electrode 44. As a result, the number of parts of the metal-air battery 30 can be reduced, and the manufacturing cost can be reduced.
Further, as in the metal-air battery 30 shown in FIGS. 6 and 7, the metal electrode 5 is used as the first electrodeposition electrode 43, and the third electrode provided between the metal electrode 5 and the air electrode 9 is used as the second electrode. The electrode 44 for analysis may be used. As a result, the air electrode 9 can be prevented from being damaged during electrodeposition, and the life characteristics of the metal-air battery 30 can be improved. The third electrode may be provided such that the main surface of the third electrode faces one main surface of the metal electrode 5 as in the metal-air battery 30 shown in FIG. 6, and the metal-air battery shown in FIG. 30, two third poles may be provided so as to sandwich the metal electrode 5.
Further, the first electrode 43 and the second electrode 44 may be provided in the second electrolyte tank 18 provided so that the electrolyte 3 in the first electrolyte tank 2 flows. As a result, metal can be deposited on the first electrodeposition electrode 43 while continuing discharge by the metal-air battery 30, and the metal-containing ion concentration of the electrolytic solution 3 can be reduced.
When the metal electrode 5 is used as the first electrode 43, a metal electrodeposited in the anode reaction in the metal electrode 5 accompanying discharge may be used. Moreover, the metal electrode 5 which has the electrodeposited metal may be taken out from the first electrolyte bath 2, and a process for making the electrodeposited metal efficiently available for the anode reaction may be performed.

  When the first and second electrodeposition electrodes 43 and 44 are provided separately from the metal electrode 5 and the air electrode 9, the material of the first and second electrodeposition electrodes 43 and 44 is more than the metal that is the electrode active material. A metal material (for example, metallic nickel) or a carbon material having a low ionization tendency may be used. Further, the first and second electrodeposition electrodes 43 and 44 may be in the form of a plate, a mesh, a punching metal, an expanded metal, a porous body, a foamed body, or the like.

11. Control unit The control unit 4 is provided so as to perform control of the discharge current, control of the precipitation reaction of the precipitate 17, exchange of the electrolytic solution, or supply of the electrolytic solution, water, or electrolyte based on the measurement result of the measuring unit 24. be able to. The control unit 4 can control the metal-air battery 30 so that the surface of the metal electrode 5 is not covered with the passive film.
The control unit 4 can include, for example, an arithmetic circuit, a storage device, and the like. Further, the control unit 4 inputs the measurement result of the measurement unit 24 as an input signal, performs an operation based on the input signal, calculates an output signal, and outputs the output signal to the switch 12, the pump 25, the valve 26, and the deposition promoting mechanism 6. It can provide so that it can output to the control means 15, such as. Thereby, based on the measurement result of the measurement unit 24, the discharge current is controlled, the precipitation reaction of the precipitate 17 is controlled, the exchange of the electrolytic solution is controlled, or the supply of the electrolytic solution, water, or the electrolyte is performed. It becomes possible to control. Moreover, it becomes possible to control the ion concentration of the electrolyte solution 3 by these control, and it can suppress that a passive film precipitation reaction arises.
Further, the control unit 4 can be connected to the measurement unit 24, the switch 12, the pump 25, the valve 26, the deposition promoting mechanism 6 and the like by the signal line 28 or wirelessly. This enables signal transmission / reception.
Moreover, the control part 4 is provided so that a branch condition can be memorize | stored. This branching condition can be set so that the metal electrode 5 is not covered with the passive film and the discharge by the metal-air battery can be continued. The branching condition can also be set so that the water level of the electrolytic solution 3 in the first electrolytic solution tank 2 does not change significantly, so that the electrolyte concentration of the electrolytic solution 3 in the first electrolytic solution tank 2 does not change significantly. Can also be set.
The branch condition can be set based on the result of an experiment such as a discharge experiment described later.

In the metal-air battery 30 shown in FIG. 1, a case where the conductivity of the electrolytic solution 3 is measured by the conductivity meter as the measurement unit 24 and the discharge current is controlled by the switch 12 will be described. In this case, the control unit 4 can control the switch 12 as shown in the flowchart of FIG.
In the flowchart shown in FIG. 8, the branch condition is “whether or not the conductivity of the electrolytic solution measured by the conductivity meter is 0.35 S / cm or less”. In addition, it is known from the discharge experiment described later that the metal electrode 5 can be prevented from being covered with the passive film when the discharge is stopped when the conductivity of the electrolytic solution is 0.35 S / cm.

First, the control unit 4 inputs the conductivity of the electrolyte measured by the conductivity meter as an input signal. And the control part 4 judges whether the input electrical conductivity is 0.35 S / cm or less.
When the electrical conductivity is higher than 0.35 S / cm, the control unit 4 sends a signal for turning on the switch 12 to the switch 12 to discharge. If the switch 12 is already turned on, the discharge is continued. If the discharge is continued, the OH ⁻ ion concentration decreases, so the conductivity of the electrolyte decreases.

When the electrical conductivity is 0.35 S / cm or less, the control unit 4 sends a signal for switching the switch 12 to the switch 12 to stop the discharge, and the metal-air battery is kept on standby for a predetermined time. Thereby, the anode reaction and the cathode reaction can be stopped. As a result, the increase in the metal-containing ion concentration and the decrease in the OH ⁻ ion concentration can be stopped, and the surface of the metal electrode 5 can be prevented from being covered with the passive film.
In addition, since the normal precipitation reaction does not stop even when the discharge is stopped, the normal precipitation reaction as shown in the above chemical formulas 3 and 4 proceeds during the standby time, the OH ⁻ ion concentration increases, and the metal-containing ion concentration decreases. To do. Accordingly, the conductivity of the electrolyte gradually increases during the standby time. Note that the standby time can be set based on the results of experiments performed in advance.
Thereafter, the conductivity of the electrolytic solution is again measured with a conductivity meter to determine whether or not the branch condition is satisfied.
By controlling the metal-air battery 30 in this manner, the discharge can be continued while suppressing the formation of a passive film on the surface of the metal electrode 5. Therefore, in this metal-air battery, it is possible to prevent the discharge from being stopped due to the inhibition of the anode reaction by the passive film, and the utilization efficiency of the electrode active material contained in the metal electrode 5 can be increased. .

When the zinc-air battery is controlled as shown in the flowchart shown in FIG. 8, it is considered that the Zn (OH) ₄ ²⁻ ion concentration in the electrolytic solution changes as shown in FIG. That is, the Zn (OH) ₄ ^2- ion concentration gradually increases during discharge. When the switch 12 is turned off and the discharge is stopped, the Zn (OH) ₄ ²⁻ ion concentration gradually decreases. Therefore, it is considered that the discharge can be performed again if a sufficient discharge interval is provided.
Further, it is considered that the OH ⁻ ion concentration in the electrolytic solution changes as shown in FIG. That is, the OH ⁻ ion concentration during discharge gradually decreases. When the switch 12 is turned off and the discharge is stopped, the OH ⁻ ion concentration gradually increases. Therefore, it is considered that the discharge can be performed again if a sufficient discharge interval is provided.

Next, in the metal-air battery 30 shown in FIG. 1, the case where the conductivity of the electrolytic solution 3 is measured by the conductivity meter as the measuring unit 24 and the precipitation reaction of the precipitate 17 is controlled by the precipitation promoting mechanism 6 will be described. To do.
The controller 4 can control the precipitation promoting mechanism 6 as in the flowchart shown in FIG.
In the flowchart shown in FIG. 11, the branching condition is “whether or not the conductivity of the electrolyte measured by the conductivity meter is 0.45 S / cm or more”. In addition, it is known from the discharge experiment described later that the re-discharge can be sufficiently performed when the conductivity of the electrolytic solution is 0.45 S / cm or more.

First, the control unit 4 inputs the conductivity of the electrolyte measured by the conductivity meter as an input signal. And the control part 4 judges whether the input electrical conductivity is 0.45 S / cm or more.
When the electrical conductivity is smaller than 0.45 S / cm, the control unit 4 sends a signal for starting the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to start the precipitation promoting mechanism 6. Moreover, when the precipitation promotion mechanism 6 has already moved, the precipitation promotion by the precipitation promotion mechanism 6 is continued. Specifically, a signal for opening the valve 26 a and a signal for starting the pump 25 are sent to the valve 26 a and the pump 25. As a result, the electrolytic solution in the first electrolytic solution tank 2 can come into contact with the substance 20 that promotes precipitation provided in the second electrolytic solution tank 18, and the normal precipitation reaction can be promoted. When the normal precipitation reaction is promoted in this way, the rate of increase of the metal-containing ion concentration accompanying the discharge can be reduced, and the discharge time by the metal-air battery 30 can be lengthened.

When the electrical conductivity is 0.45 S / cm or more, the control unit 4 sends a signal for stopping the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to stop the precipitation promoting mechanism 6. Specifically, a signal for closing the valve 26 a and a signal for stopping the pump 25 are sent to the valve 26 a and the pump 25.
Thereby, it is possible to suppress the power consumption by the deposition promoting mechanism 6 or the consumption of the substance 20 that promotes the deposition.

Next, in the metal-air battery 30 shown in FIG. 1, the case where the conductivity of the electrolyte solution 3 is measured by the conductivity meter as the measurement unit 24, the electrolyte solution exchange mechanism is controlled, and the electrolyte solution is replaced will be described. .
The controller 4 can control the precipitation promoting mechanism 6 as in the flowchart shown in FIG.
In the flowchart shown in FIG. 12, the branching condition is “whether or not the conductivity of the electrolytic solution measured by a conductivity meter is 0.35 S / cm or less”. In addition, it is known from the discharge experiment described later that the metal electrode 5 can be prevented from being covered with a passive film when the electrolyte has a conductivity of 0.35 S / cm and the electrolyte is replaced with a new one.

First, the control unit 4 inputs the conductivity of the electrolyte measured by the conductivity meter as an input signal. And the control part 4 judges whether the input electrical conductivity is 0.35 S / cm or less.
If the conductivity is greater than 0.35 S / cm, the discharge is continued. If the discharge is continued, the OH ⁻ ion concentration decreases, so the conductivity of the electrolyte decreases.
When the electrical conductivity is 0.35 S / cm or less, the control unit 4 sends a signal for exchanging the electrolytic solution to the electrolytic solution exchanging mechanism. Specifically, a signal for opening the valves 26a and 26c is sent to the valves 26a and 26c. As a result, the electrolytic solution 3 in the first electrolytic solution tank 2 and the electrolytic solution 3 in the second electrolytic solution tank 18 can be discharged. Thereafter, a signal for closing the valves 26a and 26c and opening the valve 26b is sent to the valves 26a, 26b and 26c, and a signal for starting the pump 25 is sent to the pump 25. As a result, a new electrolytic solution 3 in the third electrolytic solution tank 19 can be supplied into the first electrolytic solution tank 2, and the electrolytic solution in the first electrolytic solution tank 2 can be exchanged. Since the new electrolyte 3 does not contain metal-containing ions, the discharge by the metal-air battery 30 can be resumed.
Controlling the metal-air battery 30 in this way can increase the continuous discharge time.
When the conductivity is 0.35 S / cm or less, the control unit 4 may output a signal for switching the switch 12 off before outputting a signal for replacing the electrolytic solution. In addition, when it is determined that the conductivity is 0.35 S / cm or more, the control unit 4 may output a signal for turning on the switch 12.

If the zinc-air battery is controlled as shown in the flowchart of FIG. 12, the Zn (OH) ₄ ²⁻ ion concentration in the electrolytic solution is considered to change as shown in FIG. That is, the Zn (OH) ₄ ^2- ion concentration gradually increases during discharge. Then, when the electrolytic solution is replaced, the Zn (OH) ₄ ^2- ion concentration returns to zero, and can be discharged again.

Next, in the metal-air battery 30 shown in FIG. 1, the conductivity of the electrolytic solution 3 is measured by the conductivity meter that is the measuring unit 24, the discharge current is controlled by the switch 12, and the precipitate 17 by the precipitation promoting mechanism 6. The case of controlling the normal precipitation reaction will be described.
The control unit 4 can control the switch 12 and the precipitation promoting mechanism 6 as in the flowchart shown in FIG.
In the flowchart shown in FIG. 14, the branching condition is a first branching condition “whether or not the conductivity of the electrolyte measured by the conductivity meter is 0.35 S / cm or less” and “the electrolyte measured by the conductivity meter”. The second branching condition was “whether the electrical conductivity of 0.45 S / cm or more”.

First, the control unit 4 inputs the conductivity of the electrolyte measured by the conductivity meter as an input signal. Then, the control unit 4 determines whether or not the conductivity input under the first branch condition is 0.35 S / cm or less.
In the first branch condition, when it is determined that the electrical conductivity is greater than 0.35 S / cm, the control unit 4 sends a signal for turning on the switch 12 to the switch 12 to discharge. If the switch 12 is already turned on, the discharge is continued. Next, the control unit 4 determines whether or not the input conductivity is 0.45 S / cm or more under the second branch condition.
In the first branch condition, when it is determined that the conductivity is 0.35 S / cm or less, the control unit 4 sends a signal for turning off the switch 12 to the switch 12 to stop the discharge. Further, the control unit 4 sends a signal for starting the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to start the precipitation promoting mechanism 6. Moreover, when the precipitation promotion mechanism 6 has already moved, the precipitation promotion by the precipitation promotion mechanism 6 is continued. Thereby, the anode reaction and the cathode reaction can be stopped. Moreover, the precipitation reaction can usually be promoted, the OH ^- ion concentration can be increased, and the metal-containing ion concentration can be decreased. As a result, the waiting time until the metal-air battery 30 can be re-discharged can be shortened.

When it is determined that the electrical conductivity is smaller than 0.45 S / cm in the second branch condition, the control unit 4 sends a signal for starting the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to start the precipitation promoting mechanism 6. Moreover, when the precipitation promotion mechanism 6 has already moved, the precipitation promotion by the precipitation promotion mechanism 6 is continued. As a result, the rate of increase of the metal-containing ion concentration accompanying discharge can be reduced, and the discharge time by the metal-air battery 30 can be lengthened.
When it is determined that the electrical conductivity is 0.45 S / cm or more under the second branch condition, the control unit 4 sends a signal for stopping the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to stop the precipitation promoting mechanism 6. . Thereby, it is possible to suppress the power consumption by the deposition promoting mechanism 6 or the consumption of the substance 20 that promotes the deposition.

Next, in the metal-air battery 30 shown in FIG. 3, the conductivity of the electrolytic solution 3 in the first electrolytic solution tank 2 is measured by the conductivity meter A which is the first measuring unit 24a, and the second measuring unit 24b The conductivity of the electrolytic solution 3 in the second electrolytic solution tank 18 is measured by a certain conductivity meter B, the discharge current is controlled by the switch 12, the precipitation reaction of the precipitate 17 is controlled by the precipitation promoting mechanism 6, and the electrolytic solution A case where the exchange of the electrolytic solution 3 is controlled by an exchange mechanism or the like will be described.
The control unit 4 can control the switch 12, the deposition promoting mechanism 6, and the electrolyte exchange mechanism as in the flowchart shown in FIG.
In the flowchart shown in FIG. 15, the branching condition is a first branching condition “whether the conductivity of the electrolyte measured by the conductivity meter is 0.35 S / cm or less” and “the electrolyte measured by the conductivity meter”. The second and third branching conditions were “whether the electrical conductivity of 0.45 S / cm or more”.

First, the control unit 4 inputs the conductivity of the electrolytic solution in the first electrolytic solution tank 2 measured by the conductivity meter A as an input signal. Then, the control unit 4 determines whether or not the input conductivity is 0.35 S / cm or less under the first branch condition.
In the first branch condition, when it is determined that the electrical conductivity is greater than 0.35 S / cm, the control unit 4 sends a signal for turning on the switch 12 to the switch 12 to discharge. If the switch 12 is already turned on, the discharge is continued. Next, the control unit 4 inputs the conductivity of the electrolytic solution in the second electrolytic solution tank 18 measured by the conductivity meter B as an input signal. Then, the control unit 4 determines whether or not the input conductivity is 0.45 S / cm or more under the second branch condition.
In the first branch condition, when it is determined that the conductivity is 0.35 S / cm or less, the control unit 4 sends a signal for turning off the switch 12 to the switch 12 to stop the discharge. Next, the control unit 4 inputs the conductivity of the electrolytic solution in the second electrolytic solution tank 18 measured by the conductivity meter B as an input signal. Then, the control unit 4 determines whether or not the input conductivity is 0.45 S / cm or more under the third branch condition. Thereby, the anode reaction and the cathode reaction can be stopped.

When it is determined that the electrical conductivity is smaller than 0.45 S / cm in the second branch condition, the control unit 4 sends a signal for starting the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to start the precipitation promoting mechanism 6. Moreover, when the precipitation promotion mechanism 6 has already moved, the precipitation promotion by the precipitation promotion mechanism 6 is continued. Specifically, the deposition promoting mechanism 6 can be started by immersing the substance 20 that promotes the deposition in the electrolytic solution. Thereby, the normal precipitation reaction can be promoted, the OH ⁻ ion concentration of the electrolytic solution 3 in the second electrolytic solution tank 18 can be increased, and the metal-containing ion concentration can be decreased. As a result, the electrolytic solution 3 in the second electrolytic solution tank 18 can be used for re-discharge of the metal-air battery 30.
When it is determined that the electrical conductivity is 0.45 S / cm or more under the second branch condition, the control unit 4 sends a signal for stopping the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to stop the precipitation promoting mechanism 6. . Specifically, the precipitation promoting mechanism 6 can be stopped by pulling up the substance 20 that promotes precipitation from the electrolytic solution. Thereby, consumption of the substance 20 that promotes precipitation can be suppressed.

When it is determined that the electrical conductivity is smaller than 0.45 S / cm in the third branch condition, the control unit 4 sends a signal for starting the precipitation promoting mechanism 6 to the precipitation promoting mechanism 6 to start the precipitation promoting mechanism 6. Moreover, when the precipitation promotion mechanism 6 has already moved, the precipitation promotion by the precipitation promotion mechanism 6 is continued. Thereby, the normal precipitation reaction can be promoted, the OH ⁻ ion concentration of the electrolytic solution 3 in the second electrolytic solution tank 18 can be increased, and the metal-containing ion concentration can be decreased. As a result, the electrolytic solution 3 in the second electrolytic solution tank 18 can be used for re-discharge of the metal-air battery 30.
When it is determined that the electrical conductivity is 0.45 S / cm or more under the third branch condition, the control unit 4 performs the electrolytic solution 3 in the first electrolytic solution tank 2 and the electrolytic solution 3 in the second electrolytic solution tank 18. A signal for exchanging is sent to the electrolyte exchange mechanism. Further, the control unit 4 outputs a signal for starting the precipitation promoting mechanism 6. Specifically, the control unit 4 outputs a signal for opening the valve 26 d and discharges the electrolytic solution 3 in the first electrolytic solution tank 2 to the fourth electrolytic solution tank 40. And after discharge | emission, the control part 4 outputs the signal which closes the valve 26d, and the signal which starts the pump 25, and supplies the electrolyte solution 3 in the 2nd electrolyte solution tank 18 in the 1st electrolyte solution tank 2. FIG. Thereafter, the control unit 4 outputs a signal for opening the valve 26 e and supplies the electrolytic solution 3 in the fourth electrolytic solution tank 40 into the second electrolytic solution tank 18. Moreover, since the electrolyte solution 3 supplied to the 2nd electrolyte solution tank 18 and the substance 20 which accelerates | stimulates precipitation can be made to contact by this, the precipitation promotion mechanism 6 can be started.
By such an operation, the conductivity of the electrolytic solution 3 in the first electrolytic solution tank 2 can be set to 0.45 S / cm or more, and sufficient discharge can be performed again. Further, the OH ⁻ ion concentration of the electrolytic solution 3 in the second electrolytic solution tank 18 can be increased, and the metal-containing ion concentration can be decreased. As a result, the electrolytic solution 3 in the second electrolytic solution tank 18 can be used for re-discharge of the metal-air battery 30.
By controlling the metal-air battery 30 in this way, the electrolytic solution with a high concentration of metal-containing ions can be regenerated by the deposition promoting mechanism 6, so that the amount of electrolytic solution used can be reduced.
8, 11, 12, 14, and 15, a conductivity meter is used as the measurement unit 24, but the measurement unit 24 may be a pH meter, a viscometer, or a density meter.

  Next, in the case where the metal-air battery 30 has an electrolyte solution or water supply mechanism, the pH of the electrolyte solution 3 is measured by a pH meter that is the measurement unit 24, and the electrolyte solution to the first electrolyte tank 2 or A case where the water supply is controlled will be described.

When the metal-air battery 30 discharges for a long time, moisture contained in the electrolyte solution 3 in the first electrolyte solution tank 2 is gradually lost, and the amount of the electrolyte solution 3 gradually decreases.
For example, water contained in the electrolyte 3 may be lost due to evaporation at the air electrode 9 or the like. Since O ₂ consumed by the above chemical formula 1 is supplied from the atmosphere, the air electrode 9 is open to the atmosphere. In addition, since the temperature of the air electrode 9 rises due to the reaction heat of Chemical Formula 1, it is considered that the water evaporated in the air electrode 9 diverges into the atmosphere. For this reason, it is thought that the water | moisture content contained in the electrolyte solution 3 is lost gradually with progress of a battery reaction.

When water contained in the electrolytic solution 3 is gradually lost, the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution 3 gradually increase. As described above, the OH ⁻ ion concentration or the metal-containing ion concentration correlates with the pH value of the electrolytic solution. Therefore, by measuring the relationship between the pH value of the electrolytic solution 3 and the water level of the electrolytic solution 3 in advance and creating a calibration curve, the water level of the electrolytic solution 3 can be calculated from the measurement result of the measuring unit 24.
Moreover, the water level which supplies electrolyte solution or water to the 1st electrolyte solution tank 2 can be decided beforehand, and pH value corresponding to this water level can be made into branch conditions. For example, the branching condition can be “whether the pH value of the electrolyte measured by a pH meter is 14 or more”. Here, the case where the control part 4 controls supply of electrolyte solution or water on this branch condition is demonstrated.

First, the controller 4 inputs the pH value of the electrolyte 3 measured by the pH meter as an input signal. And the control part 4 judges whether the input pH value is 14 or more.
When the pH value is 14 or more, the control unit 4 sends a signal for causing the supply mechanism to supply the electrolytic solution or water into the first electrolytic solution tank 2 to the supply mechanism, and the supply mechanism supplies the signal into the first electrolytic solution tank 2. A predetermined amount of electrolyte or water is supplied. Note that the electrolyte concentration of the electrolyte solution supplied into the first electrolyte solution tank 2 by the supply mechanism can be made lower than the electrolyte concentration of the electrolyte solution 3 in the first electrolyte solution tank 2. As a result, by supplying the electrolytic solution, the electrolyte concentration of the electrolytic solution 3 in the first electrolytic solution tank 2 is lowered, and the pH value measured by the pH meter is reduced.
When the pH value of the electrolytic solution 3 measured by the pH meter is smaller than 14, the control unit 4 does not send a signal for causing the supply mechanism to supply the electrolytic solution or water into the first electrolytic solution tank 2.
By repeating such an operation, the water level of the electrolytic solution 3 in the first electrolytic solution tank 2 can be suppressed from becoming lower than a predetermined height. Thereby, it can suppress that the area of the metal electrode 5 which contacts the electrolyte solution 3 by the fall of the water level of the electrolyte solution 3 can be suppressed, and it can suppress that the output of the metal air battery 30 falls. .
Here, a pH meter is used for the measuring unit 24, but the measuring unit 24 may be a conductivity meter, a viscometer, or a density meter. Here, the electrolytic solution or water is supplied into the first electrolytic solution tank 2, but the electrolytic solution or water may be supplied into the electrolytic solution circulation channel or the second electrolytic solution tank 18. .

Next, in the case where the metal-air battery 30 has a high-concentration electrolyte solution or electrolyte supply mechanism, the pH of the electrolyte solution 3 is measured by a pH meter that is the measurement unit 24, and is supplied to the first electrolyte tank 2. A case where the supply of a high concentration electrolyte or electrolyte is controlled will be described.
For example, when the electrolytic solution 3 in the first electrolytic solution tank 2 is a potassium hydroxide aqueous solution, the supply mechanism uses a high concentration potassium hydroxide aqueous solution or potassium hydroxide in the form of powder or particles as the first electrolytic solution. It can provide so that it may supply in the tank 2. FIG.
When the deposit 17 is accumulated in the first electrolyte bath 2 or the second electrolyte bath 18, the deposit 17 is removed from the electrolyte 3. The electrolyte in the electrolytic solution 3 may be lost with the removal of the precipitate 17. When the electrolyte is lost, the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution 3 are lowered. As described above, the OH ⁻ ion concentration or the metal-containing ion concentration correlates with the pH value of the electrolytic solution. Therefore, by measuring the pH value with the pH meter which is the measuring unit 24, it is possible to know the decrease in the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution 3.
Further, a preferable OH ⁻ ion concentration and metal-containing ion concentration of the electrolyte solution 3 in the first electrolytic solution tank 2 are determined in advance, and pH values corresponding to these OH ⁻ ion concentration and metal-containing ion concentration are determined as branching conditions. can do. For example, the branching condition can be “whether the pH value of the electrolytic solution measured by a pH meter is 14 or less”. Here, a case where the control unit 4 controls the supply of a high concentration electrolyte or electrolyte under this branching condition will be described.

After removing the precipitate 17, the control unit 4 inputs the pH value of the electrolytic solution 3 measured by the pH meter as an input signal. And the control part 4 judges whether the input pH value is 14 or less.
When the pH value is 14 or less, the control unit 4 sends a signal that causes the supply mechanism to supply a high-concentration electrolytic solution or electrolyte into the first electrolytic solution tank 2, and supplies the first electrolytic solution tank by the supply mechanism. A predetermined amount of high-concentration electrolytic solution or electrolyte is supplied into 2. Thereby, the electrolyte concentration of the electrolytic solution 3 in the first electrolytic solution tank 2 is increased, and the pH value measured by the pH meter is increased.
When the pH value of the electrolytic solution 3 measured by the pH meter is greater than 14, the control unit 4 does not send a signal for causing the supply mechanism to supply a high concentration electrolytic solution or electrolyte into the first electrolytic solution tank 2.
By performing such an operation every time the precipitate 17 is removed, it is possible to suppress a decrease in the OH ⁻ ion concentration and the metal-containing ion concentration of the electrolytic solution 3. As a result, an increase in the ion conduction resistance between the anode and the cathode can be suppressed, and a decrease in the output of the metal-air battery 30 can be suppressed.
Here, a pH meter is used for the measuring unit 24, but the measuring unit 24 may be a conductivity meter, a viscometer, or a density meter. Further, here, a high concentration electrolyte or electrolyte is supplied into the first electrolyte bath 2, but the high concentration electrolyte or electrolyte is contained in the electrolyte circulation path or the second electrolyte bath 18. May be supplied.

Discharge experiment A zinc-air battery as shown in FIG. 4 was prepared, and the change in the conductivity of the electrolyte accompanying the discharge of the zinc-air battery was measured. The manufactured zinc-air battery is not provided with the control unit 4, the switch 12, the ultrasonic vibration unit 36, and the like.
As the metal electrode 5, a zinc plate having a thickness of 10 mm was used. Further, the size of the portion of the metal electrode 5 immersed in the electrolytic solution was 50 mm × 50 mm.
As the air electrode 9, an air electrode catalyst layer 7 and a gas diffusion layer 8 laminated are used. The air electrode 9 had a thickness of about 300 μm and a size of 50 mm × 50 mm.
As the gas diffusion layer 8, 35BC made of SGL carbon was used. 35BC consists of a carbon fiber and a microporous layer, and the microporous layer is a layer made of carbon black and a water repellent resin (PTFE).
As the air electrode catalyst layer 7, a material containing Pt-supported carbon and water-repellent resin (PTFE) was used. In order to increase the reaction surface area, Pt is supported as fine particles on carbon having a large surface area.
As the electrolytic solution, a 7M KOH aqueous solution in which zinc oxide was dissolved to 0.7 mol / L, which is the saturation solubility of zinc oxide, was used.
Further, a conductivity meter was provided as the measuring unit 24 so that the sensor unit was immersed in the electrolytic solution 3 in the electrolytic solution tank 2.
In addition, an ammeter was provided in the discharge circuit.

The produced metal-air battery was discharged at a discharge current density of 30 mA / cm ² , and the discharge capacity and the conductivity of the electrolyte were measured. The result is shown in FIG. As the discharge capacity of the metal-air battery increases, the conductivity of the electrolyte gradually decreases, and when the conductivity of the electrolyte reaches 0.3 to 0.33 S / cm, The discharge voltage dropped rapidly and became zero, and the discharge stopped.
Further, the surface of the metal electrode 5 after discharge was observed. A photograph of the metal electrode 5 after discharge is shown in FIG. For comparison, a photograph of the metal electrode 5 before discharge is shown in FIG.
From this surface observation, it was found that the metal electrode 5 after discharge was covered with a dense passive film.
From these results, when the electrical conductivity of the electrolytic solution reached 0.3 to 0.33 S / cm, the Zn (OH) ₄ ^2- ion concentration of the electrolytic solution reached the threshold value for depositing the passive film and deposited. It is considered that the passive film inhibited the anode reaction and the discharge of the metal-air battery was stopped.
Further, it was found that when the discharge by the metal-air battery is stopped when the conductivity of the electrolytic solution reaches about 0.35 S / cm, the metal electrode can be prevented from being covered with the passive film.

In addition, when the zinc-air battery whose discharge was stopped was left for several hours, the conductivity of the electrolyte measured by the conductivity meter was recovered to about 0.45 S / cm, so an attempt was made to re-discharge. In the re-discharge, the re-discharge was able to be performed until the conductivity of the electrolytic solution reached about 0.35 S / cm.
This is because, when a zinc-air battery that has stopped discharging is left to stand, the normal precipitation reaction of the above chemical formulas 3 and 4 proceeds in the electrolytic solution 3, and the OH ⁻ ion concentration in the electrolytic solution increases and Zn (OH) ₄ ^{2 -} presumably because ion concentration is lowered.
Further, it was found that when the conductivity of the electrolytic solution is recovered to about 0.45 S / cm, re-discharge can be sufficiently performed.

  1: Housing 2: First electrolyte bath 3: Electrolyte solution 4: Control unit 5: Metal electrode 6: Deposition promoting mechanism 7: Air electrode catalyst layer 8: Gas diffusion layer 9: Air electrode 10: Air electrode terminal 11: Metal electrode terminal 12: Switch 14: Separator 15: Control means 17: Deposit (used active material) 18: Second electrolyte bath 19: Third electrolyte bath 20: Substance that promotes deposition 21: Container 22: Precipitation Portion 23: Hole 24, 24a, 24b: Measuring unit 25: Pump 26, 26a, 26b, 26c, 26d, 26e: Valve 27: Electric wire 28: Signal wire 29, 29a, 29b, 29c, 29d, 29e: Electrolyte Flow path 30: Metal-air battery 32: Stirrer 33: Stirrer 34: Stirrer body 36: Ultrasonic vibrator 38: Heater 40: Fourth Solution tank 42: power supply unit 43: first conductive 析用 electrode 44: second conductive 析用 electrode

Claims (13)

Measurement of measuring the physical property value of the electrolytic solution containing the electrolytic solution, the metal electrode provided in the electrolytic solution tank, having an electrode active material and serving as an anode, the cathode serving as a cathode And a control means,
The electrolytic solution is an aqueous electrolyte solution,
The control means controls the ion concentration of the electrolyte based on the physical property value measured by the measurement unit ,
A physical property value measured by the measurement unit is input as an input signal, and further includes a control unit that outputs an output signal calculated based on the input signal to the control unit,
As the control means, at least a switch for switching on / off the discharge current is provided,
The controller is
Determining whether the physical property value measured by the measuring unit meets a predetermined first condition;
If the predetermined first condition is met, turn on the switch,
If the predetermined first condition is not met, control is performed to turn off the switch,
The metal air battery according to claim 1, wherein the predetermined first condition is a condition as to whether or not the physical property value is within a predetermined first predetermined range .   The metal-air battery according to claim 1, wherein the measurement unit measures at least one of pH value, conductivity, viscosity, and density related to the electrolyte solution.   The control means includes a switch for switching on / off a discharge current, a precipitation promoting mechanism for promoting a precipitation reaction of a precipitate generated from the electrode active material, an electrolyte exchange mechanism, an electrolyte solution, water or an electrolyte 3. The metal-air battery according to claim 1, comprising at least one of a supply mechanism and an electrodeposition mechanism for electrodepositing a metal that is the electrode active material.   The deposition promoting mechanism includes a circulation channel for circulating the electrolytic solution, a precipitation unit for bringing the substance that promotes the deposition reaction into contact with the electrolytic solution, a stirring unit for stirring the electrolytic solution, and the electrolytic solution. The metal-air battery according to claim 3, wherein the metal-air battery is at least one of an ultrasonic vibration unit that applies ultrasonic waves and a heating unit that heats the electrolytic solution. The electrolyte bath includes a first electrolyte bath and a second electrolyte bath,
The first electrolyte bath and the second electrolyte bath are connected by an electrolyte flow path,
2. The metal-air battery according to claim 1, wherein the electrolytic solution is circulated between the first electrolytic bath and the second electrolytic bath. The exchange mechanism is
Unlike the electrolyte bath, a third electrolyte bath containing the electrolyte,
A first valve for discharging the electrolyte contained in the electrolyte bath;
A second valve disposed in an electrolyte flow path connecting the electrolyte tank and the third electrolyte tank;
The controller is
Input the physical property value measured by the measurement unit as an input signal,
By the output signal calculated based on the input signal,
Open the first valve, drain the electrolyte from the electrolyte bath,
After draining of the electrolyte, the second opening of the valve, metal-air battery according to claim 3, wherein the supplying the electrolytic solution to the electrolytic tank from the third electrolytic solution tank. The controller is
The physical property value measured by the measurement unit is input as an input signal, and the output signal calculated based on the input signal
The metal-air battery according to claim 3 , wherein the electrolytic solution, water, or an electrolyte is supplied from the supply mechanism to the electrolytic solution tank. The electrodeposition mechanism is
A first electrode for electrodeposition;
A second electrode for electrodeposition that is a counter electrode of the electrode for first electrodeposition;
4. The metal-air battery according to claim 3, further comprising a power supply unit that applies a voltage between the first electrode for electrodeposition and the electrode for second electrodeposition. 5. The metal-air battery according to claim 8 , wherein the first electrode for electrodeposition is the metal electrode. The electrolyte bath includes a first electrolyte bath and a second electrolyte bath,
The first electrolyte bath and the second electrolyte bath are connected by an electrolyte flow path,
The deposition unit is included in either the first electrolytic solution tank of the second electrolytic tank,
The controller is
Input the physical property value measured by the measurement unit as an input signal,
By the output signal calculated based on the input signal,
The metal-air battery according to claim 4 , wherein a substance for promoting precipitation of the electrode active material is added from the precipitation part. Substance for promoting the deposition of the electrode active material, the metal oxide of the electrode active material, according to claim 10, wherein an electrode active material of a metal hydroxide or a porous material, Metal-air battery. The metal-air battery according to claim 10 , wherein the measurement unit is disposed in each of the first electrolyte tank and the second electrolyte tank. Of the control means, comprising at least the switch and the precipitation promoting mechanism,
The controller is
Determining whether the physical property value measured by the measuring unit meets a predetermined first condition;
If the predetermined first condition is met, turn on the switch,
If the predetermined first condition is not met, control is performed to turn off the switch,
Further, when the predetermined first condition is not met and the predetermined second condition is met, the precipitation promoting mechanism is stopped,
If the predetermined first condition is not met and the predetermined second condition is not met, the precipitation promoting mechanism is started ,
4. The metal-air battery according to claim 3 , wherein the predetermined second condition is a condition as to whether or not the physical property value is within a predetermined second predetermined range .