JP2010157401A - Air cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cell wherein loss caused by liquid resistance is properly suppressed. <P>SOLUTION: In this air cell, a porous and insulating separator held from both sides by a positive electrode and a negative electrode is provided between both the electrodes. Since the negative electrode is being continuously pushed against the separator by a pushing means, even if the negative electrode is consumed with the passage of a power generating time, a clearance between the negative electrode and the positive electrode can be maintained regardless of the passage of the power generating time. Thereby, since a distance between the negative electrode and the positive electrode can be always maintained to a minimum distance corresponding to the thickness of the separator, loss resulting from the magnitude of liquid resistance can be always suppressed to the minimum, and good battery characteristics can be exerted for a long period of time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air battery, and more particularly to an air battery in which loss due to liquid resistance is suitably suppressed.

An air battery is a battery using oxygen in the air as a positive electrode active material (for example, Patent Document 1). The negative electrode active material in this air battery is generally a metal. In an air battery, an electromotive force is generated (power generation) by a combination of an oxygen reduction reaction at the positive electrode and a metal ionization reaction with electron emission at the negative electrode.
JP 2008-181853 A

  The longer the moving distance of ions that move in the electrolyte solution from the negative electrode to the positive electrode, the greater the liquid resistance and the lower the battery characteristics. Such a problem is particularly noticeable when an electrolyte solution having a low electrical conductivity is used.

  This invention is made | formed in view of the situation mentioned above, and it aims at providing the air battery by which the loss by liquid resistance was suppressed suitably.

  In order to achieve this object, the air battery according to claim 1 uses oxygen as a positive electrode active material, has a porous and conductive positive electrode, a negative electrode capable of releasing metal ions, and the negative electrode And an electrolyte solution interposed between the positive electrode, a porous and insulating separator sandwiched between the negative electrode and the positive electrode, and a pressing means for pressing the negative electrode against the separator. I have.

  The air battery according to claim 2 is the air battery according to claim 1, further comprising: a discharge unit that discharges oxygen-reduced species generated by power generation and attached to the positive electrode using a fluid containing oxygen flowing through the positive electrode. I have.

  According to the air battery of the first aspect, the porous and insulating separator sandwiched from both sides by the both electrodes is provided between the positive electrode and the negative electrode. As a result of the electrode reaction of the negative electrode during power generation (discharge), metal ions are released from the negative electrode, so that the negative electrode is gradually consumed from the surface.

  Here, since the negative electrode is pressed against the separator by the pressing means, even if the negative electrode is consumed as the power generation time (discharge time) elapses, the separation distance between the negative electrode and the positive electrode is determined as the power generation time elapses. Can be maintained independently of.

  Therefore, since the distance between the negative electrode and the positive electrode can always be kept at the minimum distance according to the thickness of the separator, the loss due to the magnitude of the liquid resistance can always be suppressed to the minimum. it can. Therefore, there is an effect that the deterioration of the battery characteristics with the lapse of the power generation time is suppressed, and good battery characteristics can be exhibited for a long time.

  According to the air battery of Claim 2, in addition to the effect which the air battery of Claim 1 show | plays, there exists the following effect. Since the oxygen reduction species generated by the power generation and attached to the positive electrode are discharged by the discharge means, it is possible to suppress a decrease in reaction efficiency due to the adhesion of the oxygen reduction species generated by the power generation, and for a long time. There is an effect that good battery characteristics can be exhibited. Since the oxygen reducing species is discharged by the discharge means using a fluid containing oxygen flowing through the positive electrode, the oxygen reducing species should be discharged together with the supply of the positive electrode active material (oxygen) to the positive electrode. Can do.

  In addition, since the oxygen reducing species attached to the positive electrode is discharged by the discharging means, it is not necessary to increase the thickness of the positive electrode so as not to be affected by the attachment of the oxygen reducing species, so that the thickness of the positive electrode can be reduced. is there. By reducing the thickness of the positive electrode, it is possible to reduce the liquid resistance caused by the electrolyte solution that has penetrated into the pores of the positive electrode having porosity and conductivity, so that loss due to the liquid resistance is suppressed, and good battery characteristics are achieved. An air battery can be provided.

  Hereinafter, an air battery of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view showing an air battery (air battery 100) of the present invention. As shown in FIG. 1, an air battery 100 of the present invention is a battery using oxygen in the air as a positive electrode active material, and includes an air electrode 11 as a positive electrode, a metal electrode 12 as a negative electrode, and both electrodes 11, 12. Electrolytic solution 13 interposed therebetween, electrolytic solution tank 14 as a liquid tank for storing electrolytic solution 13, separator 15 sandwiched between air electrode 11 and metal electrode 12, and metal electrode 12 to separator 15 And an air flow path 18 for supplying air to the air electrode 11.

The air electrode 11 is a gas diffusion electrode having porosity and conductivity, and is a general gas diffusion electrode having a catalyst layer containing an oxygen reduction catalyst (for example, Pt, MnO ₂ , perovskite oxide, etc.). Can be used.

  Since the air electrode 11 is a porous gas diffusion electrode, the electrolytic solution 13 enters the hole. Therefore, when the thickness of the air electrode 11 is increased, the liquid resistance due to the electrolytic solution 13 immersed in the air electrode 11 is increased. Therefore, the thinning of the air electrode 11 is preferable because the influence of the liquid resistance is reduced, for example, 10 μm or less. It is preferable that

  The air electrode 11 is connected to a positive electrode terminal 11 ′ connected to the load 20 via a current collector (not shown). A current collector that collects electricity generated at the air electrode 11 may be provided as a part of the air electrode 11 or as a part of a battery case (not shown) that houses the air battery 100. It may be provided.

  The air electrode 11 is supplied with air (or oxygen) flowing from an air inlet (not shown) and flowing through the air flow path 18 to the air electrode 11. Alternatively, the electrolytic solution 13 may be circulated, and the air (oxygen) may be supplied to the air electrode 11 by flowing the electrolytic solution 13 enriched by oxygen bubbling through the air flow path 18. Good.

  The metal electrode 12 includes a reaction layer containing a negative electrode active material capable of releasing metal ions, and a current collector that collects electricity generated in the reaction layer. A negative electrode terminal 12 'to be connected is connected.

  Here, as a negative electrode active material that can be used for the reaction layer of the metal electrode 12, for example, metal ions such as lithium ions, aluminum ions, magnesium ions, sodium ions, zinc ions, and iron ions can be released. Examples of such materials (for example, metals, metal compounds, alloys, etc.) can be mentioned, but they are not particularly limited as long as metal ions move between the air electrode 11 and the metal electrode 12 to generate an electromotive force. It is not something.

  The metal electrode 12 is preferably smaller than the air electrode 11. The metal electrode 12 is configured to be smaller than the air electrode 11 and disposed so that the centers of both the electrodes 11 and 12 are aligned with each other, thereby facilitating current flow to the end of the surface of the metal electrode 12 on the air electrode 11 side. Accordingly, the consumption associated with the discharge of the surface of the metal electrode 12 on the air electrode 11 side can be made to be uniform, contributing to the maintenance of the smoothness of the surface.

  The electrolytic solution 13 is not particularly limited as long as it is a liquid capable of conducting metal ions released from the metal electrode 12, but is a non-aqueous electrolyte solution in which self-discharge of the metal electrode 12 is suppressed and a high cell voltage is easily obtained. Is preferred.

  Examples of the non-aqueous electrolyte solution include a room temperature molten salt (hereinafter referred to as “ionic liquid”) that becomes a liquid at room temperature, and an electrolyte solution in which an electrolyte is dissolved in an organic solvent. In addition, as an electrolyte (supporting salt) constituting an electrolytic solution in which an electrolyte is dissolved in an organic solvent, a known electrolyte that can be used as an electrolytic solution for an air battery can be used, and an organic solvent that can dissolve such an electrolyte is used. , And can be used as an organic solvent constituting an electrolytic solution obtained by dissolving an electrolyte in an organic solvent.

  In particular, the electrolytic solution 13 is preferably an ionic liquid. Since the ionic liquid has a low vapor pressure, when the ionic liquid is used as the electrolytic solution 13, it is difficult for the electrolytic solution 13 to volatilize from the air electrode 11, and a decrease in output due to a decrease in the electrolytic solution 13 can be prevented. Moreover, since the ionic liquid not only can suppress volatilization from the air electrode 11 but is flame retardant, the safety of the air battery 100 can be enhanced by using the ionic liquid as the electrolytic solution 13.

  Moreover, it is preferable that the electrolyte solution 13 is a hydrophobic nonaqueous electrolyte solution. By making the electrolyte solution 13 a hydrophobic non-aqueous electrolyte solution, it becomes difficult for moisture to be mixed into the electrolyte solution 13 via the air electrode 11, so that a decrease in battery performance due to moisture mixed from outside the system can be suitably suppressed. .

  As a preferable non-electrolyte solution as the electrolyte solution 13, a hydrophobic non-electrolyte solution such as a fluorohydrogenate ionic liquid, a TFSI (bistrifluoromethanesulfonylimide) ionic liquid, or diethylmethylammonium-trifluoromethanesulfonate is applied. it can.

  The separator 15 is porous so that the electrolytic solution 13 is interposed between the air electrode 11 and the metal electrode 12, and has insulation properties to insulate the air electrode 11 and the metal electrode 12. The separator 15 is not particularly limited as long as it has both porosity and insulation properties. For example, a porous polymer sheet, a porous ceramic plate, or the like can be used.

  The separator 15 is preferably thin so that the distance between the air electrode 11 and the metal electrode 12 (that is, the movement distance of metal ions) can be shortened. Therefore, as a preferable separator 15, a porous polymer sheet is mentioned, for example. Here, examples of the porous polymer sheet include a cellulose condensed ester membrane filter.

  As shown in FIG. 1, the air battery 100 of the present invention has a pressing member 16 as pressing means for pressing the metal electrode 12 against the separator 15. In the example illustrated in FIG. 1, only one pressing member 16 is illustrated for the purpose of simplifying the drawing, but the number of pressing members 16 may be plural.

  In the example shown in FIG. 1, the pressing member 16 is configured as an elastic body (for example, a spring member) having one end attached to the metal electrode 12 and the other end attached to the electrolytic solution tank 14. The elastic body as the pressing member 16 continues to press the metal electrode 12 against the separator 15 using the restoring force of the elastic body.

  By the way, the metal electrode 12 releases metal ions as a result of an electrode reaction during discharge (power generation). Therefore, as the discharge time (power generation time) elapses, the metal electrode 12 is gradually consumed from the surface. Such consumption of the metal electrode 12 occurs mainly on the surface facing the air electrode 11, that is, the surface in contact with the separator 15. Therefore, as the discharge time elapses, the separation distance between the metal electrode 12 and the air electrode 11 gradually increases.

  As the distance from the metal electrode 12 to the air electrode 11 increases, the moving distance of ions that move in the electrolyte solution 13 from the metal electrode 12 toward the air electrode 11 increases, so that the liquid resistance increases, and as a result, the battery Characteristics are degraded. A decrease in battery characteristics accompanying an increase in the separation distance between the metal electrode 12 and the air electrode 11 is significant when the electrolytic solution 13 is a non-aqueous electrolyte solution having a lower electrical conductivity than when the electrolytic solution is an aqueous electrolyte solution.

  On the other hand, according to the air battery 100 of the present invention, the pressing member 16 continues to press the metal electrode 12 against the separator 15, so that the distance between the metal electrode 12 and the air electrode 11 is set to the discharge time. Regardless of the course of the above, the thickness of the separator 15 can be kept to a minimum.

  As a result, since the loss due to the liquid resistance of the electrolyte 13 interposed between the metal electrode 12 and the air electrode 11 is always suppressed to the minimum, the battery performance of the air battery 100 decreases with the passage of the discharge time. Can be suppressed.

  In the example shown in FIG. 1, the pressing member 16 is an elastic body (for example, a spring member), and the metal electrode 12 is pressed against the separator 15 using the restoring force of the elastic body. You may comprise as an electric actuator.

  When the pressing member 16 is configured as an electric actuator, the pressing force for pressing the metal electrode 12 against the separator 15 can be appropriately controlled as necessary. For example, a plurality of electric actuators as pressing members 16 are provided, and a window capable of detecting the surface shape of the metal electrode 12 from the outside is provided in a battery case (not shown), and a laser sensor or the like is provided from the outside through the window. By controlling the pressing force of each electric actuator in accordance with the detected surface shape of the metal electrode 12, it is possible to prevent the pressing force from concentrating on a part of the separator 15.

By the way, as above-mentioned, the loss by the liquid resistance of the electrolyte solution 13 becomes small, so that the separation distance of the air electrode 11 and the metal electrode 12 is short. However, as the distance between the air electrode 11 and the metal electrode 12 is shorter, oxides (for example, Al ₂ O ₃ , Li ₂ O _2, etc.) that are oxygen-reduced species generated by the power generation reaction are generated in the air electrode 11. It becomes easy to adhere. When the oxygen reducing species adhere to the air electrode 11 and the reaction site in the catalyst layer is covered with the oxygen reducing species, the reaction efficiency decreases accordingly. In particular, when the electrolytic solution 13 is a nonaqueous electrolytic solution, the solubility of the oxygen-reducing species in the electrolytic solution 13 tends to be low, so that the attachment of the redox species to the air electrode 11 becomes significant.

  In addition, as described above, the thickness of the air electrode 11 is preferably as thin as possible because the influence of the liquid resistance can be reduced. On the other hand, when the thickness of the air electrode 11 is reduced, the oxygen reducing species is attached. The reaction efficiency is significantly reduced.

  Therefore, the air battery 100 of the present invention uses oxygen reducing species adhering to the surface of the air electrode 11 as a result of power generation (discharge) by the air battery 100 as air flowing through the air electrode 11 (that is, oxygen as a positive electrode active material). And a discharge means (not shown) for discharging out of the system.

  Therefore, oxygen-reduced species adhering to the surface of the air electrode 11 are discharged out of the system by the discharge means, and this is the case when the air electrode 11 and the metal electrode 12 are brought close to each other or the thickness of the air electrode 11 is reduced. However, it is possible to suitably suppress a reduction in reaction efficiency due to adhesion of oxygen-reducing species to the air electrode 11.

  Here, since the oxygen reducing species are discharged by the discharging means using the air flowing through the air electrode 11, the oxygen reducing species can be discharged together with the supply of the positive electrode active material to the air electrode 11. it can. In addition, it is preferable to further have a filter means for capturing oxygen-reduced species discharged by the discharge means.

  As a discharge means (not shown), for example, a configuration having an air amount adjusting means (for example, a fan or an air pump) for adjusting the flow rate of the air supplied to the air electrode 11 to be larger than a necessary amount can be mentioned. In addition, a configuration may be provided in which turbulent flow generating means (for example, the shape of the air flow path 18) that generates turbulent flow in the air electrode 11 is provided after the air supply means has increased the air flow rate from a necessary amount.

  Here, when the electrolytic solution 13 enriched with oxygen is circulated through the air flow path 18 to supply air to the air electrode 11, that is, the fluid containing oxygen as the positive electrode active material is the electrolytic solution 13. In some cases, an electrolytic solution flow rate adjusting means (for example, a pump) that adjusts the flow rate of the electrolytic solution 13 to be larger than a necessary amount can be used as the discharging means. Further, the flow rate of the electrolytic solution 13 is increased from the necessary amount by the electrolytic solution flow rate adjusting unit, and then the turbulent flow generating unit (for example, the shape of the air flow path 18) that generates the turbulent flow of the electrolytic solution 13 at the air electrode 11. It is good also as a structure which provides.

  Alternatively, for example, a peeling means (for example, a device that applies energy such as ultrasonic waves) that peels oxygen-reduced species attached to the air electrode 11 and the surface of the air flow path 18 are charged by static electricity and peeled off from the air electrode 11. An electrostatic adsorption means for attracting the reduced oxygen species to the air flow path 18 side by electrostatic coulomb force is provided, and the charge on the surface of the air flow path 18 is discharged as necessary, thereby the air flow path 18 side. A configuration in which the oxygen-reduced species attracted to the air is placed on the air and discharged outside the system may be used as the discharge means. Note that as the electrostatic attraction means, a general electrostatic attraction apparatus can be applied in which an electrode is disposed inside and a voltage is applied to the electrode to charge the surface with static electricity.

  As described above, according to the air battery 100 of the present invention, since the pressing member 16 that continues to press the metal electrode 12 against the separator 15 is provided, the distance between the metal electrode 12 and the air electrode 11. Can be maintained at the minimum thickness of the separator 15 regardless of the passage of discharge time, and the deterioration of the battery characteristics with the passage of power generation time is suppressed, and as a result, good over a long period of time. Battery characteristics can be exhibited.

  Further, according to the air battery 100 of the present invention, the oxygen-reduced species attached to the surface of the air electrode 11 due to the power generation (discharge) by the air battery 100 is a fluid that flows through the air electrode 11 (that is, the positive electrode active material). Is discharged out of the system by a discharge means using a fluid containing a certain oxygen), so that a reduction in reaction efficiency due to the attachment of oxygen-reducing species to the air electrode 11 can be suitably suppressed and good over a long period of time. Battery characteristics can be exhibited.

  Further, since the oxygen reducing species adhering to the surface of the air electrode 11 is discharged out of the system by the discharging means using the fluid flowing through the air electrode 11, the separation distance between the air electrode 11 and the metal electrode 12 can be shortened. At the same time, the air electrode 11 can be made thin.

  As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. It can be guessed.

It is a schematic diagram which shows the air battery of this invention.

Explanation of symbols

11 Air electrode (positive electrode)
12 Metal electrode (negative electrode)
13 Electrolytic solution (electrolyte solution)
15 Separator 16 Pressing member (Pressing means)
100 air battery

Claims (2)

An air battery using oxygen as a positive electrode active material,
A porous and conductive positive electrode;
A negative electrode capable of releasing metal ions;
An electrolyte solution interposed between the negative electrode and the positive electrode;
A porous and insulating separator sandwiched from both sides by the negative electrode and the positive electrode;
An air battery comprising: a pressing unit that presses the negative electrode against the separator. 2. The air battery according to claim 1, further comprising discharge means for discharging oxygen-reduced species generated by power generation and attached to the positive electrode using a fluid containing oxygen flowing through the positive electrode.

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