JP5262580B2 - Air battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air battery having simple constitution and decreasing attachment of aggregates of air bubbles generated in a system during charge discharge to an electrode. <P>SOLUTION: The air battery has an air electrode layer, a negative electrode layer, and an electrolyte layer housing an electrolyte performing metallic ion conduction between the air electrode layer and the negative electrode layer, and includes an air bubble aggregation decreasing means decreasing the aggregation of air bubbles in the electrolyte layer. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an air battery that can suppress bubbles generated in the system from collecting and adhering to an electrode.

  The air battery is a battery that uses oxygen as a positive electrode active material, and uses air containing oxygen from the outside during discharge. Therefore, it is possible to increase the proportion of the negative electrode active material in the battery container as compared with a general battery having positive and negative electrode active materials in the battery. Therefore, in principle, the electric capacity that can be discharged is large, and it is easy to reduce the size and weight. Further, since the oxidizing power of oxygen used as the positive electrode active material is strong, the battery electromotive force is relatively high. Furthermore, since oxygen has a feature that it is a clean material without resource restrictions, the air battery has a small environmental load. As described above, the air battery has many advantages and is expected to be used for a battery for a portable device, a battery for an electric car, a battery for a hybrid car, a battery for a fuel cell car, and the like.

Several techniques relating to such an air battery have been disclosed so far. For example, in Patent Document 1, an air electrode arranged in a vertical direction is immersed in an electrolytic solution, and the electrolytic solution and air are circulated by a pump. A technique relating to an air battery is disclosed, in which air is brought into contact with an air electrode to cause an electrochemical reaction.
Japanese Patent Laid-Open No. 4-154055

  When durability evaluation was performed using a conventional air battery, a rapid decrease in discharge capacity occurred during repeated charge and discharge. While the internal resistance before the durability evaluation was about 300Ω, the internal resistance after a sudden drop in the discharge capacity was about 30000Ω, and an increase of 100 times was confirmed. Moreover, when the air battery after the sudden decrease in discharge capacity was disassembled, large bubbles were found under the air electrode. After removing the bubbles, the internal resistance again decreased to about 300Ω, so it became clear that the main cause of the rapid decrease in discharge capacity was an increase in internal resistance due to the presence of bubbles under the air electrode. .

  Such bubbles are a problem when the electrodes are arranged substantially horizontally. This is because bubbles exist so as to cover the electrode surface due to the relationship with gravity, and the electrolyte is prevented from being supplied to the electrode. Therefore, when the electrodes are arranged in the vertical direction as in the air battery disclosed in Patent Document 1, it is difficult to cause a problem. However, the air battery disclosed in Patent Document 1 has a complicated configuration.

  Therefore, an object of the present invention is to provide an air battery that has a simple configuration and can suppress bubbles generated in the system from collecting and adhering to the electrode during charging and discharging.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention has an air electrode layer, a negative electrode layer, and an electrolyte solution layer containing an electrolyte solution that conducts ions between the air electrode layer and the negative electrode layer, and bubbles are collected in the electrolyte solution layer. It is an air battery provided with the bubble aggregation suppression means which suppresses doing.

  In the air battery of the present invention, it is preferable that the bubble aggregation suppressing means includes a stirring means for stirring the electrolyte in the electrolyte layer. This is because, by stirring the electrolytic solution in the electrolytic solution layer, it is possible to suppress bubble aggregation and adhesion to the electrode in the electrolytic solution layer. The stirring means is not particularly limited as long as it can stir the electrolyte in the electrolyte layer and can withstand the environment in which the air battery is used. Specifically, for example, a magnetic stirrer in which a magnetic stirrer is arranged in the electrolyte layer and power is transmitted to the stirrer by a magnetic field rotating from outside the electrolyte layer, a rod shape, a plate shape, a propeller shape, etc. The mechanical stirrer which arrange | positions this stirring element in an electrolyte layer, and transmits motive power to the stirring element from the outside of an electrolyte layer via a rotating shaft can be used.

  In the air battery of the present invention, the bubble aggregation suppressing means includes a reserve tank provided outside the electrolyte layer, and an electrolyte circulation means for circulating the electrolyte between the reserve tank and the electrolyte layer. It is preferable. This is because, by circulating the electrolytic solution between the reserve tank outside the electrolytic solution layer and the electrolytic solution layer, it is possible to suppress bubbles from being collected in the electrolytic solution layer.

  In the air battery of the present invention in which the bubble aggregation suppressing means includes the reserve tank and the electrolyte circulation means, the electrolyte flow passage for circulating the electrolyte between the reserve tank and the electrolyte layer in the electrolyte circulation means It is preferable that a filter for refining bubbles is provided in the electrolyte flow passage. This is because, by adopting such a form, when the electrolyte circulates between the reserve tank and the electrolyte layer, the bubbles can be made finer. The filter is not particularly limited as long as it can pass an electrolytic solution and can withstand the environment in which the air battery is used.

  In the air battery of the present invention, it is preferable that the bubble aggregation suppressing means includes vibration transmitting means for transmitting vibration to the electrolyte layer. This is because by transmitting vibration to the electrolyte layer, it is possible to suppress bubbles from being collected and attached to the electrode. The vibration transmitting means is not particularly limited as long as it can transmit vibration to the electrolyte layer. Specifically, for example, when an air battery is mounted on an automobile, a fixing member that fixes the vehicle body and the air battery so that vibration generated when the automobile is decelerated or accelerated can be transmitted to the air battery. In addition, a means for transmitting vibration by ultrasonic waves or the like can be considered.

  In the air battery of the present invention in which the bubble aggregation suppressing means includes vibration transmission means, it is preferable that a vibration promoting member is attached to the outside. This is because such a configuration can transmit more vibration to the electrolyte layer. An elastic member such as a spring can be considered as the vibration promoting member.

  According to the present invention, it is possible to provide an air battery that has a simple configuration and can suppress bubbles generated in the system during charging and discharging from being collected and attached to the electrode.

  Hereinafter, the air battery of the present invention will be described in detail.

  The air battery of the present invention includes an air electrode layer, a negative electrode layer, and an electrolyte solution layer that contains an electrolyte solution that conducts metal ions between the air electrode layer and the negative electrode layer. Bubble aggregation suppressing means for suppressing bubbles from collecting in the layer is provided.

  According to the air battery of the present invention, since the bubble aggregation suppressing means for suppressing the aggregation of bubbles generated in the system during charging / discharging is provided, the bubbles are aggregated when repeated charging / discharging is performed. It can suppress adhering to an electrode. Accordingly, it is possible to prevent a rapid decrease in discharge capacity that occurs when repeated charge / discharge is performed. Hereinafter, specific embodiments of the air battery of the present invention will be illustrated and described in detail.

1. First Embodiment FIG. 1 is a cross-sectional view schematically showing a part of an air battery 10 which is an embodiment of an air battery of the present invention.

  As shown in FIG. 1, the air battery 10 includes an air electrode layer 12, a negative electrode layer 14, and an electrolyte solution layer 13 interposed between the air electrode layer 12 and the negative electrode layer 14, and further suppresses bubble aggregation. Stirring means 17 as means is provided. The stirring unit 17 includes a stirring bar 16 installed in the electrolyte layer 13 and a power transmission unit 15 that transmits power to the stirring bar 16. The air battery 10 takes in oxygen from the oxygen layer 11 (or external air) provided outside the air electrode layer 12 during discharge. Hereinafter, the air battery 10 will be described for each configuration.

<Agitating means 17>
The stirring unit 17 includes a power transmission unit 15 installed outside the electrolyte layer 13 and a stirrer 16 installed inside the electrolyte layer 13. The stirrer 16 is not particularly limited as long as it can withstand the environment in which the air battery 10 is used.

  When the stirring means 17 is a magnetic stirrer, the power transmission means 15 is a magnetic stirrer main body, and the stirrer 16 can be a bar magnet sealed with Teflon (registered trademark) or the like. The magnetic stirrer main body is provided with a drive unit, in which a magnet can be rotated by a motor. Therefore, by rotating the magnet with a motor in the drive part of the magnetic stirrer main body, the stirrer 16 installed inside the electrolytic solution layer 13 rotates, and the electrolytic solution in the electrolytic solution layer 13 can be stirred. . Thus, the magnetic stirrer is preferable because stirring in a sealed container can be easily performed.

  When the stirring means 17 is a mechanical stirrer, the power transmission means 15 is composed of a rotating shaft and a power source that rotates the rotating shaft, and the stirrer 16 is a member having a bar shape, a plate shape, a propeller shape, or the like. Can be used. In this case, power is transmitted to the stirrer 16 disposed in the electrolytic solution layer 13 through the rotating shaft, and the electrolytic solution in the electrolytic solution layer 13 can be stirred.

<Air electrode layer 12>
Next, the air electrode layer 12 will be described. The air electrode layer 12 contains a conductive material. An air electrode current collector (not shown) that collects the air electrode layer 12 is provided in contact with the inside or the outer surface of the air electrode layer 12.

  The conductive material contained in the air electrode layer 12 is not particularly limited as long as it has conductivity. Specifically, a carbon material etc. can be mentioned, for example. Furthermore, the carbon material may have a porous structure or may not have a porous structure. However, in the present invention, it is preferable to have a porous structure. This is because the specific surface area is large and many reaction fields can be provided.

  Specific examples of the carbon material having a porous structure include mesoporous carbon. On the other hand, specific examples of the carbon material having no porous structure include graphite, acetylene black, carbon nanotube, and carbon fiber.

  As content of the electroconductive material in the air electrode layer 12, it is preferable to exist in the range of 10 mass%-99 mass%, for example. If the content of the conductive material is too small, the reaction field may decrease and the battery capacity may be reduced. If the content of the conductive material is too large, the content of the catalyst is relatively reduced and sufficient. Therefore, it is preferable to take appropriate measures according to the density and volume of the material.

  In the present invention, the conductive material preferably supports a catalyst. This is because the electrode reaction is performed more smoothly. Examples of the catalyst include cobalt phthalocyanine and manganese dioxide. As content of the catalyst in an air electrode layer, it is preferable to exist in the range of 1 mass%-90 mass%, for example. If the catalyst content is too low, sufficient catalytic function may not be achieved. If the catalyst content is too high, the content of the conductive material is relatively reduced, the reaction field is reduced, and the battery capacity is reduced. Therefore, it is preferable to determine appropriately depending on the conductive material to be combined.

  Although the air electrode layer 12 should just contain an electroconductive material at least, it is preferable to contain the binder which fixes an electroconductive material further. Examples of the binder include polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE). Although it does not specifically limit as content of the binder in an air electrode layer, For example, it is preferable that it is in the range of 40 mass% or less, especially 1 mass%-10 mass%.

  The thickness of the air electrode layer 12 varies depending on the use of the air battery 10 and the like, but is preferably in the range of 2 μm to 500 μm, and more preferably in the range of 5 μm to 300 μm.

  Further, as described above, the air electrode current collector is provided in contact with the inside or the outer surface of the air electrode layer 12. The air electrode current collector has a function of collecting the air electrode layer 12. The material for the air electrode current collector is not particularly limited as long as it has conductivity. Specific examples include stainless steel, nickel, aluminum, iron, titanium, and carbon. Examples of the shape of the air electrode current collector include a foil shape, a plate shape, and a mesh (grid) shape. Especially, in this invention, it is preferable that the shape of an air electrode electrical power collector is a mesh form. This is because the current collection efficiency is excellent. In this case, normally, a mesh-shaped air electrode current collector is disposed inside the air electrode layer 12. Furthermore, the air battery 10 may have another air electrode current collector (for example, a foil-shaped current collector) that collects the electric charge collected by the mesh-shaped air electrode current collector. In the present invention, a battery case to be described later may also have the function of an air electrode current collector.

<Negative electrode layer 14>
Next, the negative electrode layer 14 will be described. The negative electrode layer 14 contains a negative electrode active material. Further, a negative electrode current collector (not shown) for collecting the negative electrode layer 14 is provided in contact with the inside or the outer surface of the negative electrode layer 14.

  As a negative electrode active material contained in the negative electrode layer 14, a negative electrode active material of a general air battery can be used and is not particularly limited. When the air battery 10 is a lithium air secondary battery, the negative electrode active material can absorb and release Li ions. Specific examples include carbon materials such as metal lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, and graphite. Among these, metallic lithium and carbon materials are preferred, and metallic lithium is more preferred from the viewpoint of increasing capacity.

  The negative electrode layer 14 only needs to contain at least a negative electrode active material, but may contain a conductive material that improves the conductivity of the negative electrode active material and a binder that immobilizes the negative electrode active material as necessary. good. About the kind of conductive material and a binder, and usage-amount etc., since it is the same as that of what is used for the air electrode layer 12 mentioned above, description here is abbreviate | omitted.

  Further, as described above, the negative electrode current collector is provided in contact with the inside or the outer surface of the negative electrode layer 14. The negative electrode current collector has a function of collecting current of the negative electrode layer 14. The material of the negative electrode current collector is not particularly limited as long as it has conductivity. Specific examples include copper, stainless steel, nickel, and the like. Examples of the shape of such a negative electrode current collector include a foil shape, a plate shape, and a mesh (grid) shape. In the present invention, a battery case, which will be described later, may have the function of a negative electrode current collector.

<Electrolyte layer 13>
Next, the electrolytic solution layer 13 will be described. The electrolyte layer 13 contains an electrolyte solution that conducts metal ions between the air electrode layer 12 and the negative electrode layer 14. The form of the electrolytic solution is not particularly limited as long as it has metal ion conductivity, and examples thereof include a nonaqueous electrolytic solution.

The type of the non-aqueous electrolyte used in the present invention is preferably selected as appropriate according to the type of metal ion to be conducted. For example, the non-aqueous electrolyte of a lithium air battery usually contains a lithium salt and an organic solvent. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO _4, and LiAsF ₆ ; and LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , An organic lithium salt such as LiC (CF ₃ SO ₂ ) ₃ can be used. Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), butylene carbonate, γ-butyrolactone, sulfolane, acetonitrile, 1 , 2-dimethoxymethane, 1,3-dimethoxypropane, diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran and mixtures thereof. The organic solvent is preferably a solvent having high oxygen solubility. This is because dissolved oxygen can be used efficiently in the reaction. The concentration of the lithium salt in the nonaqueous electrolytic solution is, for example, in the range of 0.2 mol / L to 3 mol / L. In the present invention, a low volatile liquid such as an ionic liquid may be used as the nonaqueous electrolytic solution.

  In addition, the air battery 10 preferably includes a separator that holds the nonaqueous electrolytic solution between the air electrode layer 12 and the negative electrode layer 14. As said separator, porous membranes, such as polyethylene and a polypropylene, and nonwoven fabrics, such as a resin nonwoven fabric and a glass fiber nonwoven fabric, etc. can be mentioned, for example.

<Air battery 10>
In the air battery 10, at least the air electrode layer 12, the negative electrode layer 14, and the electrolyte layer 13 described above are used in a battery case (not shown).

  The shape of the battery case used for the air battery 10 is not particularly limited. The battery case may be an open-air battery case or a sealed battery case. An open-air battery case is a battery case that can come into contact with the atmosphere. On the other hand, when the battery case is a sealed battery case, it is preferable to provide a gas (air) supply pipe and a discharge pipe in the sealed battery case. In this case, the gas to be supplied / discharged preferably has a high oxygen concentration, and more preferably pure oxygen. In addition, it is preferable to increase the oxygen concentration during discharging and decrease the oxygen concentration during charging.

  Examples of the type of the air battery 10 include a lithium metal air battery, a potassium metal air battery, a magnesium air battery, an aluminum air battery, and a calcium air battery. Among these, a lithium metal air battery is preferable. In addition, examples of the use of the air battery 10 include a vehicle mounting application, a stationary power supply application, and a household power supply application.

2. Second Embodiment FIG. 2 is a cross-sectional view schematically showing a part of an air battery 20 which is one embodiment of the air battery of the present invention. The same components as those of the air battery 10 shown in FIG. Therefore, for the air battery 20, only the bubble aggregation suppressing means 30 will be described.

<Bubble aggregation suppression means 30>
The bubble aggregation suppressing means 30 provided in the air battery 20 includes a reserve tank 27 and an electrolyte solution circulating means for circulating the electrolyte solution between the reserve tank 27 and the electrolyte layer 13. The electrolytic solution circulating means includes an outward flow passage 25 through which the electrolytic solution flows from the electrolytic solution layer 13 to the reserve tank 27, a return flow passage 29 through which the electrolytic solution flows from the reserve tank 27 to the electrolytic solution layer 13, and a reserve tank. 27 and a pump (not shown) for circulating the electrolytic solution between the electrolytic solution layer 13. Further, by providing the valve 26 in the forward flow passage 25 and the valve 28 in the return flow passage 29, the flow rate of the electrolyte flowing through each flow path can be adjusted.

  In the air battery 20, the electrolytic solution in the electrolytic solution layer 13 flows to the reserve tank 27 through the forward flow passage 25, and further returns from the reserve tank 27 to the electrolytic solution layer 13 through the return flow passage 29. Then, it is circulated through a reserve tank 27 outside the electrolyte layer 13. Since the electrolytic solution in the electrolytic solution layer 13 is thus circulated, the bubbles in the electrolytic solution layer 13 are caused to flow together with the electrolytic solution, and the bubbles are prevented from collecting and the bubbles may adhere to the electrode. It is suppressed.

  Further, it is preferable that a filter capable of refining bubbles is provided in the forward flow passage 25 and / or the return flow passage 29. The filter is not particularly limited as long as it has an eye that allows the electrolytic solution to pass therethrough and can withstand the environment in which the air battery is used.

3. Third Embodiment Further, another embodiment of the air battery of the present invention will be described below. In the description of this embodiment, only the bubble aggregation suppressing means that is a feature of the present invention will be described.

  In the air battery of the present invention, the vibration transmitting means for transmitting vibration from the outside of the air battery to the electrolyte layer can be used as a bubble aggregation suppressing means. By transmitting vibrations to the electrolyte layer, it is possible to suppress bubbles from being collected and attached to the electrode.

  The vibration transmitting means is not particularly limited as long as it can transmit vibration to the electrolyte layer. Specifically, for example, when the air battery of the present invention is mounted on an automobile, the vehicle body and the air battery of the present invention can transmit vibrations generated when the automobile decelerates or accelerates to the air battery of the present invention. A fixing member or the like for fixing the frame can be considered. In addition, means for transmitting vibration from the outside of the air battery of the present invention to the electrolyte layer by ultrasonic waves or the like can be considered.

  Thus, in the case where the bubble transmission suppressing means is included in the bubble aggregation suppressing means, it is preferable that the vibration promoting member is mounted outside the air battery of the present invention. This is because such a configuration can transmit more vibration to the electrolyte layer. An elastic member such as a spring can be considered as the vibration promoting member.

  In the description of the air battery of the present invention so far, a plurality of bubble aggregation suppressing means has been described, but these may be used alone or two or more may be used simultaneously.

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

  The present invention will be further described below with reference to examples.

(Example)
In this example, a lithium air secondary battery was produced. The battery was assembled in an argon box. Moreover, the battery case which consists of a glass beaker cell, and the 1 L size sealed container were used.

First, metal Li (manufactured by Honjo Metal Co., Ltd., φ18 mm, thickness 0.25 mm) was placed in the battery case. Next, a separator (φ18 mm, thickness 1.0 μm) made of glass fiber was placed on the metal Li. Next, 4.8 mL of a non-aqueous electrolyte solution in which LiClO ₄ (manufactured by Kishida Chemical Co.) was dissolved at a concentration of 1M in propylene carbonate (PC, manufactured by Kishida Chemical Co., Ltd.) was injected from above the separator. Thereafter, a stir bar was further added.

Next, a composition having 25 parts by mass of carbon black, 42 parts by mass of MnO ₂ , and 33 parts by mass of polyvinylidene fluoride (PVDF) is obtained by using carbon paper (air electrode current collector, manufactured by Toray Industries, Inc., TGP-H- (090, φ18 mm, thickness 0.28 mm) was applied with a doctor blade to form an air electrode layer (φ18 mm, basis weight 5 mg). Next, the air electrode layer of the obtained air electrode was disposed and sealed so as to face the separator to obtain an evaluation cell.

  When performing the following evaluation, a magnetic stirrer was used as a bubble aggregation suppressing means. The stir bar was rotated at 10 rpm.

(Comparative example)
An evaluation cell was obtained in the same manner as in the example except that the bubble aggregation suppressing means was not provided.

<Evaluation>
About the evaluation cell of an Example and the evaluation cell of a comparative example, charging / discharging was performed 20 cycles, respectively, and the subsequent direct current resistance was measured. The results are shown in Table 1 below.

  In the evaluation cell of the example, a rapid increase in DC resistance after charging / discharging was not confirmed. Further, the evaluation cell was visually confirmed during the evaluation, but the presence of bubbles covering the electrodes could not be confirmed. On the other hand, in the evaluation cell of the comparative example, a rapid increase in DC resistance was confirmed. Moreover, when the evaluation cell under evaluation was confirmed visually, the presence of bubbles covering the electrodes was confirmed. Therefore, it is considered that in the evaluation cell of the example, bubbles in the electrolyte layer were removed by the bubble aggregation suppressing means, and a rapid increase in internal resistance after charge / discharge was prevented.

It is sectional drawing which shows schematically a part of one embodiment of the air battery of this invention. It is sectional drawing which shows schematically a part of one embodiment of the air battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Air battery 11 ... Oxygen layer 12 ... Air electrode layer 13 ... Electrolyte layer 14 ... Negative electrode layer 15 ... Power transmission means 16 ... Stirrer 17 ... Stirring means (bubble collection suppression means)
DESCRIPTION OF SYMBOLS 20 ... Air battery 25 ... Outward flow path 26 ... Valve 27 ... Reserve tank 28 ... Valve 29 ... Return flow path 30 ... Bubble collection suppression means

Claims (4)

An air electrode layer, a negative electrode layer, and an electrolyte solution layer containing an electrolyte solution that conducts ions between the air electrode layer and the negative electrode layer,
The bubble in the electrolyte layer is found with suppressing bubble set suppressing means to be set,
The bubble aggregation suppressing means includes a reserve tank provided outside the electrolyte layer, and an electrolyte circulation means for circulating the electrolyte between the reserve tank and the electrolyte layer,
The electrolyte circulation means includes an electrolyte flow passage for circulating the electrolyte between the reserve tank and the electrolyte layer, and a filter for minimizing the bubbles in the electrolyte flow passage,
Furthermore, the bubble aggregation suppressing means includes a magnetic stirrer or a mechanical stirrer,
Air battery. The bubble set suppressing means comprises said vibration transmitting means for transmitting the vibrations in the electrolytic solution layer, and external to the mounting vibration acceleration member, air battery according to claim 1. The air battery according to claim 2, wherein the vibration promoting member is an elastic member. The air cell according to any one of claims 1 to 3, wherein the bubble aggregation suppressing means includes means for transmitting vibration from the outside to the electrolyte layer by ultrasonic waves.

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