JP2010153234A - Air cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cell capable of preferably restraining degradation of cell performance caused by water contained in its electrolyte solution. <P>SOLUTION: The air cell has a liquid reservoir which includes a cathode, an anode, and nonaqueous electrolyte solution intercalated between them, and leads to a water removal means. The water removal means is equipped with a first electrode which can contact water contained in the nonaqueous electrolyte solution, and the other second electrode contacting oxygen, with an electrolytic layer intercalated between the electrodes. When a voltage difference is made by a voltage difference generating means where a voltage of the first electrode is higher than that of the second electrode, an oxidation reaction of water occurs at the first electrode resulting in decomposition of water, while, on the other hand, water generates at the second electrode by reduction reaction of oxygen. So, since the water contained in the nonaqueous electrolyte solution in the liquid reservoir is eliminated by the water removal means from the second electrode side as exhaust, degradation of cell performance caused by water contained in the electrolyte solution is able to be suitably suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air battery, and more particularly, to an air battery that can suitably suppress a decrease in battery performance due to moisture contained in an electrolyte solution.

  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.

When an aqueous electrolyte solution is used as the electrolyte solution in this air battery, self-discharge of the negative electrode by water and water decomposition reaction occur, thereby causing a decrease in energy density and output density. On the other hand, the non-aqueous electrolyte solution can suppress the above-described decrease in energy density and output density caused by water, and can achieve high energy density and high output density of the air battery. .
JP 2008-181853 A

  However, since the air battery is configured as a system in which the positive electrode is opened due to the property of using air as the positive electrode active material, it is not possible to completely prevent moisture from entering the system from outside the system. As the gas exchange area at the positive electrode increases, the amount of moisture mixed into the system also increases. Therefore, when the gas exchange area at the positive electrode is increased to accommodate a large current, the energy density and output due to the moisture mixed into the system. There was a problem that the density decreased.

  As measures against such a problem, a method of supplying pre-dried air to the positive electrode, a method of adding a dehumidifying material such as silica gel to the electrolyte solution in the system, and the like can be adopted. However, when air that has been dried in advance is supplied to the positive electrode, a large amount of energy is required to dry the air.

  On the other hand, when a dehumidifying material is added to the electrolyte solution in the system, it is necessary to add a large amount of dehumidifying material sufficient to absorb the mixed water. Or when a small amount of dehumidifying material is added, the operation | work which replaces as needed is needed.

  This invention is made | formed in view of the situation mentioned above, and it aims at providing the air battery which can suppress suitably the fall of the battery performance by the water | moisture content contained in electrolyte solution.

  In order to achieve this object, the air battery according to claim 1 uses oxygen as a positive electrode active material, and includes a positive electrode, a negative electrode capable of releasing metal ions, and the negative electrode and the positive electrode. An intervening non-aqueous electrolyte solution, a liquid tank for storing the non-aqueous electrolyte solution, and a water removing means for removing water from the non-aqueous electrolyte through the liquid tank, A first electrode capable of contacting moisture contained in the non-aqueous electrolyte, a second electrode in contact with oxygen, a proton conductive electrolyte layer interposed between the first electrode and the second electrode, and the first electrode And a potential difference generating means for generating a potential difference so that electrons flow from the electrode to the external circuit and function as an anode, and electrons flow from the external circuit to the second electrode and function as a cathode.

  The air battery according to claim 2 is provided with an anion exchange membrane interposed between the first electrode and the non-aqueous electrolyte solution in the air battery according to claim 1.

  The air battery according to claim 3 is the air battery according to claim 1 or 2, wherein the first gas flow path for supplying oxygen or an oxygen-containing gas to the positive electrode, and the pressure relief for depressurizing the liquid tank. And a second gas flow path for allowing the gas released by the pressure release by the pressure release means to flow into the first gas flow path.

  According to the air battery of the first aspect, the water removing means communicates with the liquid tank that stores the nonaqueous electrolyte liquid interposed between the positive electrode and the negative electrode. The first electrode in this water removing means can contact moisture contained in the non-aqueous electrolyte solution, and the other second electrode is in contact with oxygen, and a proton conductive electrolyte layer is interposed between these electrodes. ing.

  Here, when the potential difference generating means creates a potential difference in which the potential of the first electrode is higher than the potential of the second electrode, water is electrolyzed on the catalyst to release electrons in the first electrode, While oxygen molecules and protons are generated, at the second electrode, protons and oxygen react to generate water. Therefore, the water contained in the nonaqueous electrolyte solution in the liquid tank is drained and removed from the second electrode side by the water removing means.

  The potential difference required for the electrode reaction between the first electrode and the second electrode may be relatively small, and when no water is present in the nonaqueous electrolyte solution, no current flows even when a voltage is applied. Therefore, it can dehumidify with comparatively little energy consumption, and there exists an effect that the fall of the battery performance by the water | moisture content contained in electrolyte solution can be suppressed suitably.

  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 an anion exchange membrane is interposed between the first electrode and the non-aqueous electrolyte solution, the metal ion eluted from the negative electrode or the metal ion added as an electrolyte is present in the non-aqueous electrolyte solution. Ions can be trapped before reaching the first electrode. Therefore, there is an effect that each part constituting the water removing means can be prevented from being poisoned by the metal ions contained in the non-aqueous electrolyte solution.

  According to the air battery of Claim 3, in addition to the effect which the air battery of Claim 1 or 2 show | plays, there exists the following effect. Depressurization in the liquid tank is performed by the depressurizing means, and the gas released by the depressurization flows into the first gas flow path for supplying oxygen or oxygen-containing gas to the positive electrode through the second gas flow path. The

  Since oxygen is generated when water is decomposed by the first electrode in the water removing means, the internal pressure of the liquid tank communicating with the water removing means rises due to the generated oxygen. Therefore, by depressurizing the liquid tank by the depressurizing means, the pressure in the liquid tank can be maintained moderately, and safety is ensured.

  In addition, since the gas released by depressurization mainly contains oxygen generated by the decomposition of water by the first electrode, the gas is introduced into the first gas flow path to flow into the positive electrode. There is an effect that the concentration of supplied oxygen can be increased.

  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. An electrolyte solution 13 interposed therebetween, an electrolyte solution tank 14 as a solution tank for storing the electrolyte solution 13, an air channel 50 for supplying air to the air electrode 11, a water removal unit 30, and an anion exchange membrane layer 40 And have.

As the air electrode 11, a general air electrode having a catalyst layer containing an oxygen reduction catalyst (for example, Pt, MnO ₂ , perovskite oxide, etc.) can be used. The air electrode 11 is connected to the air flow path 50, and air (or oxygen) flowing through the air flow path 50 is supplied to the air electrode 11.

  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 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.

  In the air battery 100 of the present invention, the electrolyte solution 13 is a non-aqueous electrolyte solution, for example, a room temperature molten salt (hereinafter referred to as “ionic liquid”) that becomes a liquid at room temperature, or an electrolysis in which an electrolyte is dissolved in an organic solvent. Liquid can be used. 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.

  Here, 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 hydrophobic non-electrolyte solution preferable as the electrolyte solution 13, a fluorohydrogenate ionic liquid, a TFSI (bistrifluoromethanesulfonylimide) ionic liquid, diethylmethylammonium-trifluoromethanesulfonate, or the like can be applied.

  The air flow path 50 extends from an air inflow port (not shown) and is connected to the air electrode 11, and the second flow path 52 is disposed between the electrolytic solution tank 14 and the first flow path. And a valve 53 that opens and closes the second flow path 52.

  Although details will be described later, when water contained in the electrolytic solution 13 is removed by the water removal unit 30, oxygen is generated in the first catalyst layer 32, thereby increasing the internal pressure of the electrolytic solution tank 14. . Therefore, by opening the valve 53, the electrolyte tank 14 can be depressurized, so that the pressure inside the electrolyte tank 14 can be kept moderate and the safety of the air battery 100 can be ensured. it can.

  Further, the gas released from the electrolytic solution tank 14 by opening the valve 53 flows through the second flow path 52 in the arrow X direction and flows into the first flow path 51. Here, since the oxygen generated in the first catalyst layer 32 is mainly contained, the gas is supplied to the air electrode 11 as a result of flowing into the first flow path 51 via the second flow path 52. The oxygen concentration of the air can be increased.

  The valve 53 is opened by control by a control device (not shown). The valve 53 may be opened periodically, or the internal pressure of the electrolytic solution tank 14 may be measured by a sensor, and may be opened when a predetermined internal pressure is exceeded. It may be configured to open based on the amount of water discharged from the removal unit 30.

  As shown in FIG. 1, the air battery 100 of the present invention is provided with a water removal unit 30 that removes moisture mixed in the electrolytic solution 13.

  The water removal unit 30 includes a first electrode 32, a second electrode 33 provided to face the first electrode 32, and an electrolyte layer interposed between the first electrode 32 and the second electrode 33. 31 and a power supply 34 that applies a voltage between the first electrode 32 and the second electrode 33.

  The first electrode 32 is an electrode that can electrolyze water and includes a conductive catalyst layer. As the catalyst layer of the first electrode 32, for example, a catalyst layer including a catalyst-supported carbon (Pt-supported catalyst carbon) in which a catalyst such as platinum is supported on carbon particles and an electrolyte can be applied.

  The second electrode 33 is an electrode including a catalyst layer capable of reducing oxygen and having conductivity. As the catalyst layer of the second electrode 33, for example, the catalyst layer exemplified as the catalyst layer of the first electrode 32 can be applied.

  The electrolyte layer 31 is a layer responsible for ion conduction between the first electrode 32 and the second electrode 33. For example, a cation exchange membrane made of a cation exchange resin such as Nafion (registered trademark: manufactured by DuPont) can be used. . Note that an electrolytic solution interposed between the first electrode 32 and the second electrode 33 may be configured as the electrolyte layer 31.

  Here, when a cation exchange membrane is used as the electrolyte layer 31, the first electrode 32 is disposed on one surface side of the electrolyte layer 31, and the second electrode 33 is disposed on the other surface side. be able to.

  Specifically, first, a paste having an appropriate viscosity is prepared by mixing materials such as a solution containing catalyst particles such as Pt-supported catalytic carbon and an electrolyte (for example, Nafion (registered trademark)), and then obtained. The paste is applied as a thin layer on the surface of a conductor such as a metal mesh and dried to produce the electrodes 32 and 33. And by sandwiching both surfaces of the cation exchange membrane between the obtained electrodes 32 and 33 and pressurizing and joining, an electrode unit can be produced.

  As shown in FIG. 1, the water removal unit 30 communicates with a communication portion (not shown) provided on the side surface of the electrolytic solution tank 14 with the anion exchange membrane layer 40 interposed therebetween. More specifically, in the water removal unit 30, the first electrode 32 is directed to the electrolytic solution tank 14, and the first electrode 32 is included in the electrolytic solution 13 through the communicating portion of the electrolytic solution tank 14. Contact with moisture. In FIG. 1, the water removal unit 30 is illustrated as being adjacent to the anion exchange membrane layer 40 disposed on the side surface of the electrolytic solution tank 14, but is provided on the side surface of the electrolytic solution tank 14. The water removal unit 30 may be provided at the end of the passage connected to the communication portion (not shown).

  On the other hand, the second electrode 33 in the water removal unit 30 is disposed on a flow path through which air flows and is in contact with air (oxygen).

  The power supply 34 in the water removal unit 30 applies a voltage between the first electrode 32 and the second electrode 33 in order to create a potential difference in which the potential of the first electrode 32 is higher than the potential of the second electrode 33. .

When the potential of the first electrode 32 is made higher than the potential of the second electrode 33 by the application of the voltage by the power source 34, the reaction shown in the formula (1), that is, the electrolysis reaction of water, occurs in the first electrode 32. Arise.
2H ₂ O → 4H ⁺ + 4e ⁻ + O ₂ (1)

Protons generated as a result of the reaction shown in the formula (1) are transmitted to the second electrode 33 side by the electrolyte layer 31 and react with oxygen in the air in the second electrode 33 as shown in the formula (2). .
4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)

  Water generated as a result of the oxygen reduction reaction shown in the equation (2) is discharged out of the system. Therefore, as a result of the electrode reaction occurring in the water removal unit 30, the water contained in the electrolytic solution 13 can be discharged out of the system.

  Note that the voltage value applied between the first electrode 32 and the second electrode 33 by the power source 34 is used for the thickness of the electrolyte layer 31 (that is, the magnitude of the resistance of the electrolyte layer 31) and the electrodes 32 and 33. Although it can be appropriately selected according to various factors such as the type of catalyst (difference in activation overvoltage), it is preferably about 3 V at the maximum and more preferably about 2 V.

  As shown in FIG. 1, an anion exchange membrane layer 40 is provided between the first electrode 32 of the water removal unit 30 and the communication part of the electrolytic solution tank 14. The anion exchange membrane layer 40 can be formed by applying an anion exchange membrane resin to the surface of the first electrode 32 that faces the electrolytic solution tank 14 side.

  Although the kind of anion exchange resin which comprises the anion exchange membrane layer 40 is not specifically limited, For example, 1-3 primary amino group, quaternary ammonium group, pyridyl group, imidazole group, quaternary bilidium group, quaternary imidazolium group etc. An anion exchange resin having an anion exchange group can be used.

  In the air battery 100 of the present invention, since the anion exchange membrane layer 40 is disposed between the first electrode 32 and the communicating portion of the electrolytic solution tank 14, the metal ions contained in the electrolytic solution 13 are the first. The electrode 32 cannot be reached.

  When the electrolyte layer 31 is composed of a cation exchange membrane, the electrolyte layer 31 may be poisoned by metal ions (for example, Li ions or Al ions) contained in the electrolyte solution 13. However, since the anion exchange membrane layer 40 is provided on the surface of the first electrode 32 that faces the electrolytic solution tank 14 side, water as a reactive species can be selectively permeated. 31 (cation exchange membrane) poisoning can be prevented.

  As described above, according to the air battery 100 of the present invention, by providing the water removal unit 30, moisture mixed in the electrolyte solution 13 that is a non-aqueous electrolyte solution can be removed. A decrease in energy density and output density due to contained moisture can be suppressed.

  A voltage is applied between the first electrode 32 and the second electrode 33 of the water removal unit 30 by the power source 34, but when no water is present in the electrolytic solution 13 (that is, on the first electrode 32). In the absence of moisture), no current flows and no energy is consumed. Therefore, according to the air battery 100 of the present invention, the electrolyte solution 13 can be dehumidified with much less energy consumption than the method of previously drying the air supplied to the positive electrode (air electrode 11).

  In addition, since the water removal unit 30 is provided, the electrolytic solution 13 can be dehumidified constantly and continuously, so there is no need to supply a large amount of the dehumidifying material to the electrolytic solution, and no replacement work of the dehumidifying material is required. Therefore, moisture can be suitably removed from the electrolytic solution 13.

  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.

  In the above embodiment, the air electrode 11 is connected to the air flow channel 50 and the air flowing through the air flow channel 50 is supplied to the air electrode 11. However, the electrolytic solution 13 is circulated and the air is bubbled. Thus, the electrolytic solution 13 enriched with oxygen may be passed through the air electrode 11 to supply air (oxygen) to the air electrode 11.

  In the configuration in which the electrolytic solution 13 is circulated and the air is supplied to the air electrode 11, the air flowing through the second flow path 52 by releasing the pressure by opening the valve 53 is used as the air supplied to the electrolytic solution 13. be able to.

  Alternatively, the air flowing through the second flow path 52 may be supplied to the second electrode 33 by depressurization by opening the valve 53.

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 Electrolyte (non-aqueous electrolyte)
14 Electrolyte tank (liquid tank)
30 Water removal unit (water removal means)
31 Electrolyte layer 32 First electrode 33 Second electrode 34 Power supply (potential difference generating means)
40 Anion exchange membrane layer (anion exchange membrane)
51 1st flow path (1st gas flow path)
52 Second channel (second gas channel)
53 Valve (Pressure release means)
100 air battery

Claims (3)

An air battery using oxygen as a positive electrode active material,
A positive electrode;
A negative electrode capable of releasing metal ions;
A nonaqueous electrolyte solution interposed between the negative electrode and the positive electrode;
A liquid tank for storing the non-aqueous electrolyte solution;
Water removal means for removing water from the non-aqueous electrolyte through the liquid tank,
The water removing means is
A first electrode that can contact moisture contained in the non-aqueous electrolyte;
A second electrode in contact with oxygen;
A proton conductive electrolyte layer interposed between the first electrode and the second electrode;
And a potential difference generating means for generating a potential difference so that electrons flow from the first electrode to the external circuit and function as an anode, and electrons flow from the external circuit to the second electrode and function as a cathode. Air battery to play.   The air battery according to claim 1, further comprising an anion exchange membrane interposed between the first electrode and the nonaqueous electrolyte solution. A first gas flow path for supplying oxygen or an oxygen-containing gas to the positive electrode;
Pressure release means for performing pressure release in the liquid tank;
The air battery according to claim 1, further comprising: a second gas flow path that allows the gas released by the pressure release by the pressure release means to flow into the first gas flow path.

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