JP2017183003A - Air secondary battery - Google Patents

Abstract

An air secondary battery capable of maintaining a three-phase interface in an air electrode satisfactorily and performing stable charging and discharging. An air secondary battery (1) includes an electrode body (20) in which an air electrode (23) and a negative electrode (21) are laminated via a separator (22), a battery case (10) containing the electrode body (20) together with an alkaline electrolyte, and a battery case (10). And an electrolyte storage unit 30 for storing an alkaline electrolyte that increases during charging and supplying an alkaline electrolyte that decreases when discharging, the level of the alkaline electrolyte in the electrolyte storage unit 30. Is higher than the uppermost surface of the cathode 23. [Selection diagram] Fig. 1

Description

  The present invention relates to a chargeable / dischargeable air secondary battery.

  In recent years, an air battery using oxygen in the atmosphere as a positive electrode active material has attracted attention as an energy conversion device that has a high energy density and can be easily reduced in size and weight.

  As such an air battery, a zinc-air primary battery used for a power source of a hearing aid or the like is well known. In addition, rechargeable air secondary batteries are expected to be put to practical use as new secondary batteries that exceed the capacity density of conventional lithium ion batteries. However, an air secondary battery using a metal for a negative electrode is a so-called dendrite in which the metal for a negative electrode is repeatedly dissolved and precipitated in association with a chemical reaction during charging and discharging (hereinafter referred to as a battery reaction), and the metal for the negative electrode precipitates in a dendritic shape. Since it grows, there is a problem of causing an internal short circuit, and it has not yet been put into practical use.

  By the way, as a kind of air secondary battery, an air battery using an alkaline aqueous solution as an electrolyte and using hydrogen as a negative electrode active material is known (see, for example, Patent Document 1 and Non-Patent Document 1. Hereinafter, it is referred to as a hydrogen-air secondary battery. ). Although the hydrogen-air secondary battery uses a hydrogen storage alloy as the metal for the negative electrode, the negative electrode active material is hydrogen that is stored and released in this hydrogen storage alloy, so the dissolution and precipitation reaction of the hydrogen storage alloy itself accompanying the battery reaction is It does not occur, and the problem of internal short circuit due to dendrite growth as described above does not occur. For this reason, hydrogen air secondary batteries are considered to be close to practical use among air secondary batteries.

In an air secondary battery using an alkaline electrolyte such as the above hydrogen-air secondary battery, a charge / discharge reaction represented by the following formula occurs in the air electrode.
Discharge: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (1)
Charging: 4OH ⁻ → O ₂ + 2H ₂ O + 4e ⁻ (2)
The air electrode of the hydrogen-air secondary battery generates hydroxide ions by reducing oxygen as represented by reaction formula (1) during discharge, and oxygen as represented by reaction formula (2) during charging. And produce water. Oxygen generated at the air electrode is released into the atmosphere from a portion of the air electrode that is open to the atmosphere. As described above, in the hydrogen-air secondary battery, the amount of moisture in the electrolytic solution changes with the battery reaction during charging and discharging.

JP 2012-64477 A

M.M. Morimitsu, T .; Kondo, N .; Osada, K .; Takano, Electrochemistry, vol. 78, No5, pp. 493-496 (2010)

  By the way, the discharge reaction of the air electrode in the hydrogen-air secondary battery is good only at the three-phase interface where all of the catalyst component (solid phase), electrolyte (liquid phase) and oxygen (gas phase) contained in the air electrode are present. proceed. For this reason, in a state where the three-phase interface is not maintained, for example, when the air electrode is completely immersed in the electrolytic solution, oxygen is not supplied and the progress of the battery reaction is hindered. In a dry state that is not in contact, there arises a problem that the discharge voltage decreases.

  However, since the air electrode of the hydrogen-air secondary battery consumes water during discharge and generates water during charging as described above, it is difficult to maintain the three-phase interface in a good state. For this reason, in the hydrogen-air secondary battery, it becomes more difficult to maintain a good three-phase interface, particularly as the electrode area is large and the battery capacity is large, and the high capacity that is the original purpose cannot be achieved.

  In addition, the air electrode of a hydrogen-air secondary battery is generally water-repellent in order to secure an air diffusion path because the progress of the battery reaction is inhibited unless oxygen (gas phase) is present as described above. It is formed with the material which has. Therefore, the air electrode has a low water absorption of the electrolytic solution, and in order to perform a stable discharge especially when the electrolytic solution is reduced, the electrolytic solution needs to be sufficiently supplied to the air electrode.

  However, if the electrolyte solution is not sufficiently supplied to the air electrode, the electrolyte solution in the electrode body is depleted and the three-phase interface in the air electrode cannot be maintained well. There is a risk that it will decrease.

  The present invention has been made in view of such circumstances, and an object of the present invention is to maintain an excellent three-phase interface in the air electrode and to perform stable charge and discharge. Is to provide.

<First Aspect of the Present Invention>
According to a first aspect of the present invention, there is provided an electrode body in which an air electrode and a negative electrode are laminated via a separator, a housing that houses the electrode body together with an alkaline electrolyte, and the housing. An electrolyte storage unit that stores the alkaline electrolyte that sometimes increases and supplies the alkaline electrolyte that decreases at the time of discharge, and the level of the alkaline electrolyte in the electrolyte storage unit is the air electrode It is an air secondary battery that is higher than the uppermost surface.

  The air secondary battery is formed so that the housing for housing the electrode body and the electrolyte storage unit communicate with each other. Therefore, the alkaline electrolyte increased at the time of charging in the electrode body moves from the housing to the electrolyte storage part and is stored. Moreover, the alkaline electrolyte decreased at the time of discharge in the electrode body is moved and supplied from the electrolyte storage unit to the housing. Here, the hydrostatic pressure of the electrolytic solution in the air electrode of the electrode body increases according to the liquid level of the electrolytic solution in the electrolytic solution storage unit. Then, the amount of the electrolyte is set so that the level of the electrolyte in the electrolyte reservoir is higher than the reference when the height of the uppermost surface of the air electrode constituting the electrode body is used as a reference. ing. As a result, although the air electrode is made of a material having water repellency, the electrolyte solution can easily penetrate into the internal pores even during discharge when the electrolyte solution decreases, and the three-phase interface can be maintained well. it can.

  Thereby, according to the 1st aspect of this invention, since the hydrostatic pressure of the electrolyte solution in an air electrode can be raised, the three-phase interface in an air electrode can be maintained favorably, and stable charge / discharge can be performed. The effect that the air secondary battery which can be provided can be provided is acquired.

<Second Aspect of the Present Invention>
The second aspect of the present invention is the above-described first aspect of the present invention, further comprising a water-repellent film that allows air to permeate and does not permeate the alkaline electrolyte, and the casing conducts air inside and outside. A vent hole is formed, and the water repellent film is an air secondary battery arranged so that one surface side is in contact with the air electrode and the other surface side covers the vent hole from the inside of the housing.

  In the air secondary battery, since the air electrode accommodated in the inside absorbs oxygen during charging and releases oxygen during discharging, the casing is formed with a vent for conducting air inside and outside. The air secondary battery includes a water-repellent film that allows air to pass through but does not allow electrolyte to pass through. Since the water repellent film is arranged so that one surface side is in contact with the air electrode and the other surface side covers the vent from the inside of the housing, air can be moved between the outside of the housing and the air electrode, Functions as a gas diffusion layer. In addition, the air electrode has moderate water repellency so as to be advantageous for the formation of a three-phase interface, whereas the water repellent film does not allow electrolyte to permeate, so the electrolyte inside the casing overflows from the vent. You can prevent it from coming out. Therefore, the air secondary battery can prevent a decrease in the electrolytic solution due to the leakage of the electrolytic solution from the housing even when the electrolytic solution increases during charging.

  Thus, according to the second aspect of the present invention, in addition to the operational effects of the first aspect of the present invention described above, leakage of the electrolytic solution is prevented even when the hydrostatic pressure of the electrolytic solution inside the housing is increased. The effect that an air secondary battery can be provided is obtained.

<Third Aspect of the Present Invention>
According to a third aspect of the present invention, in the second aspect of the present invention described above, the housing includes a plurality of the vent holes, and further communicates the plurality of vent holes along the surface of the water repellent film. It is an air secondary battery in which a ventilation path is formed.

  The casing of the air secondary battery has a plurality of air vents that conduct air inside and outside. The casing is further formed with an air passage that allows the plurality of vents to communicate with each other, so that air that has entered the housing through one of the vents passes through the vent path while touching the water-repellent film. , The other vent will come out of the housing. The air passage is formed along the surface of the water repellent film. Accordingly, the water repellent film can smoothly exchange air with the air electrode by touching the air flow in the air passage. Therefore, the air secondary battery can smoothly supply oxygen to the air electrode without the air inside the housing staying.

  Thereby, according to the 3rd aspect of this invention, in addition to the effect by the 1st or 2nd aspect of this invention mentioned above, the effect that the possibility that oxygen runs short in the battery reaction in an air electrode can be reduced. Is obtained.

<Fourth aspect of the present invention>
According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention described above, the level of the alkaline electrolyte in the electrolyte storage section is the alkaline electrolyte in the air electrode. It is an air secondary battery which is lower than the liquid level height of the alkaline electrolyte in the electrolyte storage part in a state where the amount of absorption of water is saturated.

  The air electrode can maintain the three-phase interface satisfactorily by allowing the electrolytic solution to permeate the pores inside appropriately. When the hydrostatic pressure of the electrolytic solution in the air electrode is excessively increased, the absorption amount of the electrolytic solution in the air electrode may be saturated when all the internal pores are filled with the electrolytic solution. In a state where the amount of absorption of the electrolytic solution is saturated, the air electrode is deviated from the ideal three-phase interface because oxygen present in the air electrode is reduced. Therefore, the hydrostatic pressure in a state where the amount of electrolyte absorbed in the air electrode is saturated is determined in advance, and by setting the upper limit of the liquid level of the electrolyte in the electrolyte reservoir so as not to reach the hydrostatic pressure, An ideal three-phase interface can be easily maintained.

  As a result, according to the fourth aspect of the present invention, in addition to the operational effects of any one of the first to third aspects of the present invention described above, the three-phase interface in the air electrode is more favorably maintained and stable charging is achieved. The effect that the air secondary battery which can discharge can be provided is acquired.

It is sectional drawing in the XZ plane of the air secondary battery which concerns on this invention. It is sectional drawing which showed the cross section along the AA line in FIG. It is sectional drawing which represents typically the pore of an air electrode. It is a graph which shows a charge characteristic. It is a graph which shows a discharge characteristic.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, in FIG. 1 and FIG. 2, each direction of the three-dimensional space is indicated by reference signs X, Y, and Z.
FIG. 1 is a cross-sectional view in the XZ plane of an air secondary battery 1 according to the present invention. FIG. 2 is a cross-sectional view showing a cross section taken along the line AA in FIG.

  The air secondary battery 1 includes a battery case 10 as an “enclosure”, an electrolyte storage unit 30, and a connecting unit 40.

  The battery case 10 has a housing portion 11 formed therein, and a vent 12 that conducts air is formed between the outside of the battery case 10 and the housing portion 11. In the present embodiment, two vent holes 12 are formed at positions separated from each other in the X direction of the battery case 10. Further, the battery case 10 includes a lid body 13 at a position connecting the two vent holes 12.

  The battery case 10 accommodates the electrode body 20 on which the negative electrode 21, the separator 22, and the air electrode 23 are laminated and the water-repellent film 24 in the accommodating portion 11 together with the electrolytic solution.

  The negative electrode 21 is formed of a material containing a hydrogen storage alloy as will be described in detail later, and is disposed on the inner bottom surface of the housing portion 11.

  The separator 22 is a general separator for a nickel metal hydride battery, and is placed on the negative electrode 21, and its four ends are sandwiched and fixed between the upper part and the lower part of the battery case 10. Here, the battery case 10 is sealed with a gasket 14 so that the electrolytic solution does not leak outside through the gap at the end of the separator 22.

  The air electrode 23 includes a catalyst having a dual function of oxygen generation and oxygen reduction, as will be described in detail later. The air electrode 23 has appropriate water repellency so as not to prevent oxygen from entering and exiting, and is placed on the separator 22.

  The water-repellent film 24 is formed of a material that allows air to pass through but does not allow electrolyte to pass through. The water-repellent film 24 is placed on the air electrode 23 and disposed so that the upper surface is in contact with the two vent holes 12 and the lid body 13. As shown in FIG. 2, the lid 13 has a shape having a plurality of peaks and valleys in the ZY plane, and the valley portions constitute a plurality of ventilation paths 130 in the X direction that allow the two vents 12 to communicate with each other. At the same time, the top of the mountain presses and fixes the water-repellent film 24 from the upper side in the Z direction.

  Air flows through the ventilation path 130 from one of the two vents 12 to the other. The air flowing through the air passage 130 diffuses into the water repellent film 24 facing the air passage 130. The water repellent film 24 allows the air diffused therein to pass through the air electrode 23 that is in direct contact therewith. Thereby, the water repellent film 24 functions as a gas diffusion layer. The water repellent film 24 allows oxygen generated from the air electrode 23 to pass through the air passage 130. The oxygen that has permeated into the air passage 130 is released into the atmosphere outside the battery case 10 through the air vent 12.

  Here, it is preferable that the battery case 10 forcibly forms an air flow between the two vent holes 12 by providing a blower, for example. As a result, the air secondary battery 1 can stably supply oxygen to the air electrode 23 via the water repellent film 24 and can cope with high capacity and high output.

  On the other hand, permeation of the electrolyte inside the battery case 10 to the vent hole 12 and the vent path 130 is prevented by the water repellent film 24. Therefore, when the pressure of the electrolytic solution inside the battery case 10 increases, the possibility that the electrolytic solution leaks to the outside through the vent 12 can be reduced.

  The electrolytic solution storage unit 30 stores the electrolytic solution therein and is connected to the battery case 10 via the connection unit 40. And since the inside of the electrolyte storage part 30 and the accommodating part 11 of the battery case 10 are connected, electrolyte solution can move between both. For this reason, when the electrolytic solution increases due to the air electrode 23 generating water at the time of charging, the excess electrolytic solution inside the storage unit 11 moves to the electrolytic solution storage unit 30 and is stored. In addition, when the electrolytic solution decreases due to the air electrode 23 decomposing water at the time of discharge, the electrolytic solution stored in the electrolytic solution storage unit 30 moves to the storage unit 11 and the shortage of the electrolytic solution in the air electrode 23 occurs. Can be supplemented.

Next, the three-phase interface in the air electrode 23 will be described more specifically.
FIG. 3 is a cross-sectional view schematically showing the pores of the air electrode 23.

More specifically, FIG. 3 assumes that the pores of the air electrode 23 are circular holes having a diameter d, and the three-phase interface at the moment when air exists on one side of the pores and the electrolyte permeates from the other side. Indicates the state. The surface tension determined by the characteristics of this time the electrolyte gamma, tables in when the air electrode 23 and the contact angle Θ with the electrolytic solution, osmotic pressure P _O of the moment of the electrolyte electrolyte into the pores to penetrate the following formula Is done.
P _O = 4γ cos Θ / d (3)
The value of cosΘ in equation (3) increases the larger becomes osmotic pressure P _O as water-repellent degree of the air electrode 23 is high. The osmotic pressure _PO increases as the pore diameter d decreases. For this reason, the pressure required to appropriately permeate the electrolyte into the pores of the air electrode 23 depends on the water repellency of the air electrode 23 and the pore diameter distribution. In order for the electrolyte to permeate into the pores of the air electrode 23 and to maintain a good three-phase interface, the pressure of the electrolyte is expressed by the formula (3) even when the electrolyte is decreased particularly during discharge. ) it must be higher than the osmotic pressure P _O, represented by.

Here, in the air secondary battery 1, as shown in FIG. 1, the liquid level in the electrolyte storage unit 30 is set higher by a height H with respect to the uppermost surface of the air electrode 23. The inside of the electrolytic solution storage unit 30 communicates with the housing unit 11 of the battery case 10, and the negative electrode 21 and the separator 22 transmit the electrolytic solution. As hydrostatic pressure P _H of the electrolytic solution in the cathode 23 for it can be increased according to the following equation by increasing the liquid level of the electrolyte storage unit 30.
P _H = ρGH (4)
Here, ρ represents the density of the electrolytic solution, and G represents the acceleration of gravity. Specifically, for example ρ = 1.23g / cm ^3, when the G = 9.8m / s ^2, the hydrostatic pressure P _H under the conditions of H = 10 mm is about 120 Pa.

Therefore, the osmotic pressure required for the electrolyte to permeate into the pores of the air electrode 23 in the air electrode 23 when the liquid level in the electrolyte storage unit 30 is higher than the uppermost surface of the air electrode 23. the P _O can reduce the risk of hydrostatic pressure P _H of the electrolyte is below. As a result, the air secondary battery 1 can discharge stably without exhausting the electrolyte inside the air electrode 23 even during the discharge when the electrolyte decreases.

On the other hand, when the electrolyte increases during charging, the electrolyte generated excessively in the air electrode 23 moves to the electrolyte storage unit 30 and is stored. Here, if the hydrostatic pressure P _H of the electrolytic solution in the cathode 23 is excessively increased, it may occur that the absorption amount of the electrolytic solution due to the air electrode 23 is saturated. However, since the water repellent film 24 is in contact with the upper surface of the air electrode 23 and covers the vent 12 and the air passage 130 from the inside of the battery case 10, even when the pressure of the electrolyte rises, the electrolyte is not in the battery case. The possibility of leakage to the outside of 10 can be reduced. Thereby, for example, even when a crack is generated in the gap between the air electrode 23 and the battery case 10 or the air electrode 23 itself by repeating charging and discharging, it is possible to prevent a decrease due to leakage of the electrolyte.

When the amount of electrolyte absorbed by the air electrode 23 is saturated as described above, the pores inside the air electrode 23 are all filled with the electrolyte, and the area of the three-phase interface is less than the optimum value. There is a risk of a decrease. Therefore, it is preferable that the upper limit value of the liquid level height of the electrolytic solution in the electrolytic solution storage unit 30 is set within a range in which such a state does not occur. For example, the amount of the electrolytic solution in the electrolytic solution storage unit 30 is gradually increased, and the liquid level height _HL at the time when all the pores inside the air electrode 23 are filled with the electrolytic solution is confirmed in advance. And in the manufacturing process of the air secondary battery 1 used for charging / discharging, when pouring electrolyte solution, the liquid level height H of the electrolyte solution in the electrolyte storage part 30 is set between 0 and _HL . Thereby, the air secondary battery 1 can suppress the excessive penetration of the electrolytic solution into the air electrode 23, and reduce the possibility that the discharge voltage is lowered by reducing the area of the three-phase interface from the optimum value. Can do.
[Example]

1. Production of air secondary battery 1 (Example 1)
(1) Production of air electrode 23 (catalyst synthesis)
As the catalyst for the air electrode 23, a Bicroaur type bismuth iridium oxide having a dual catalytic activity for oxygen generation and oxygen reduction was used. Bi (NO ₄ ) ₃ · 5H ₂ O and H ₂ IrCl ₆ · 6H ₂ O are dissolved in 75 ° C. distilled water so as to have the same concentration, stirred and mixed, and then 2 mol% / L NaOH aqueous solution. Was added. The bath temperature at this time was 75 ° C., and the mixture was stirred for 3 days while performing oxygen publishing. The solution containing the precipitate formed thereby was maintained at 85 ° C. and evaporated to dryness to obtain a paste. The pasty product was transferred to an evaporating dish, dried in an environment of 120 ° C. for 12 hours, pulverized in a mortar, and then baked in an air atmosphere at 600 ° C. for 2 hours. Further, in order to remove by-products contained in the fired product, suction filtration was performed using distilled water at 70 ° C., and bicroa bismuth iridium oxide was isolated. Furthermore, after drying this for 12 hours in 120 degreeC environment, the catalyst of the air electrode 23 was synthesize | combined by grind | pulverizing using a mortar.

(Air electrode plate)
The thus obtained bismuth iridium oxide powder, nickel powder (particle size 10 to 20 μm), and commercially available PTFE particles were mixed at a mass ratio of 20:70:10 to form a clay. The thing was molded into a plate shape. This was dried at room temperature for 30 minutes and then press-bonded to a nickel mesh. Further, after baking at 370 ° C. for 13 minutes in a nitrogen gas atmosphere, the air electrode 23 was produced by cutting into a predetermined size.

(2) Manufacture of negative electrode (hydrogen storage alloy)
Nd, Zr, Mg, Ni, and Al were mixed so as to have a predetermined alloy composition. This was melted in a high-frequency induction melting furnace in an argon gas atmosphere, poured into a mold, and cooled to room temperature to obtain an alloy ingot. The alloy ingot was heat-treated at 1000 ° C. for 10 hours in an argon gas atmosphere to obtain an ingot having a composition of (Nd _0.99 Zr _0.01 ) _0.89 Mg _0.11 Ni _3.33 Al _0.17 . The ingot was mechanically pulverized in an inert atmosphere and sieved to obtain a hydrogen storage alloy powder having a particle size of 60 μm.

(Negative electrode plate)
With respect to 100 parts by mass of the obtained hydrogen storage alloy powder, 0.2 parts by mass of sodium polyacrylate, 0.04 parts by mass of carboxymethyl cellulose, 30 parts by mass of styrene butadiene rubber (SBR), carbon black 0 0.5 parts by mass and 22.4 parts by mass of water were added and kneaded to prepare a paste for the negative electrode mixture. This active material slurry was filled in foamed nickel, dried and then rolled and rolled to increase the amount of alloy per volume, and cut into a predetermined size to produce a negative electrode 21.

(Measurement of negative electrode capacity)
A negative electrode 21 produced in the above process, a sintered nickel hydroxide positive electrode having a sufficiently large capacity with respect to the negative electrode 21, and a separator 22 for a nickel metal hydride battery are inserted into an acrylic case, and a certain amount of electrolyte is injected. The single electrode cell of the nickel-hydrogen secondary battery of a negative electrode capacity | capacitance regulation was produced. After suspending this monopolar cell for 5 hours, charging it at 0.5 It for 2.8 hours, then discharging at the same rate (end voltage = 0.70 V), and repeating this multiple times, the maximum value of the battery capacity The capacity of the negative electrode 21 was used. At this time, the capacity of the negative electrode 21 was 640 mAh.

(3) Configuration of housing 11 Negative electrode 21 (40 mm × 40 mm, thickness 0.25 mm) subjected to capacity measurement in the above process, a separator for a nickel metal hydride battery, and air electrode 23 (40 mm × 40 mm) prepared in the above process. 40 mm, thickness 0.2 mm) and a carbon non-woven fabric (45 mm × 45 mm, thickness 0.2 mm) subjected to water repellent treatment with PTFE and carbon are stacked in this order and placed in the accommodating portion 11 of the battery case 10. The lid 13 was fixed so as to be pressed from the Z direction. The 5 mol / L KOH aqueous solution was used as the electrolytic solution and poured into the electrolytic solution storage unit 30, whereby the electrolytic solution was also poured into the storage unit 11 communicating with the electrolytic solution storage unit 30. In Example 1, the electrolytic solution was poured until the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30 with respect to the height of the uppermost surface of the air electrode became 10 mm, whereby the air secondary battery 1 was obtained. The amount of the electrolyte poured at this time was about 50 mL.

(Battery characteristics evaluation)
The air secondary battery 1 having the above configuration is allowed to stand at 25 ° C. for 1 hour, and after the electrolyte solution is absorbed by the electrode body 20, charging is performed for 10 hours at a current value of 100 mA with respect to 1 g of the catalyst amount of the air electrode 23. did. Further, the air secondary battery 1 was discharged at the same rate (end voltage = 0.00 V). And the cell voltage during charging / discharging was measured. In addition, air of 0.8 mL per minute was constantly kept flowing through the air passage 130 through the charging and discharging of the example.

(Example 2)
After the completion of charging / discharging in Example 1 above, the air secondary battery 1 of Example 1 is allowed to stand for 1 hour, and reset so that the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30 is 5 mm. Thus, the air secondary battery 1 of Example 2 was obtained. And the battery characteristic was evaluated by charging / discharging 1 cycle like Example 1 with respect to the air secondary battery 1 of Example 2. FIG.

(Example 3)
After the end of charging / discharging in Example 2, the air secondary battery 1 of Example 2 is allowed to stand for 1 hour, and is reset so that the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30 is 0 mm. Thus, the air secondary battery 1 of Example 3 was obtained. And the battery characteristic was evaluated by charging / discharging 1 cycle similarly to Example 1 with respect to the air secondary battery 1 of Example 3. FIG.

(Comparative Example 1)
After the completion of charging / discharging in Example 3 above, the air secondary battery 1 of Example 3 is allowed to stand for 1 hour, and is again adjusted so that the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30 is −10 mm. By setting, the air secondary battery 1 of Comparative Example 1 was obtained. And the battery characteristic was evaluated by charging / discharging 1 cycle similarly to Example 1 with respect to the air secondary battery 1 of the comparative example 1. FIG. In Comparative Example 1, although the liquid level of the electrolytic solution in the electrolytic solution storage unit 30 is lower than the bottom surface of the housing unit 11, at least the separator 22 and the negative electrode 21 hold the electrolytic solution. It is possible.

2. Evaluation Results of Air Secondary Battery 1 (1) Charging Characteristics FIG. 4 is a graph showing charging characteristics in Examples 1 to 3 and Comparative Example 1. In FIG. 4, the horizontal axis indicates the charge capacity that is increased by charging the air secondary battery 1, and the vertical axis indicates the cell voltage at that time. When the air secondary battery 1 is charged to a certain charge capacity, the secondary battery having a higher cell voltage has a higher reaction resistance inside and needs to be applied with a higher voltage during charging. From FIG. 4, the charging characteristics are hardly changed in Examples 1 to 3, and the cell voltage is increased in Comparative Example 1. More specifically, assuming that the voltage at the time when the air secondary battery 1 is charged for 10 hours is the charging voltage, the charging voltage of Example 2 is 0.9 mV higher than the charging voltage of Example 1, and the charging of Example 3 The voltage was 2.0 mV higher than the charging voltage of Example 1. Regarding the charging voltage of Comparative Example 1, it was 17.3 mV higher than the charging voltage of Example 1.

(2) Discharge characteristics FIG. 5 is a graph showing the discharge characteristics in Examples 1 to 3 and Comparative Example 1. In FIG. 5, the horizontal axis indicates the charge capacity that decreases by discharging the air secondary battery 1, and the vertical axis indicates the cell voltage at that time. When the air secondary battery 1 is discharged to a certain discharge capacity, the secondary battery with a lower cell voltage has a higher internal reaction resistance and cannot output a high voltage during discharge. From FIG. 5, the discharge characteristics are the best in Example 1, and decrease in the order of Example 2, Example 3, and Comparative Example 1. More specifically, assuming that the voltage when discharging to 50% of the charge capacity of the air secondary battery 1 is a discharge voltage, the discharge voltage of Example 2 is 4.4 mV lower than the discharge voltage of Example 1, and The discharge voltage of Example 3 was 7.1 mV lower than the charge voltage of Example 1. The discharge voltage of Comparative Example 1 was 17.8 mV lower than the discharge voltage of Example 1.

3. Consideration of characteristic evaluation From the above evaluation results, by increasing the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30, it was possible to suppress the reaction resistance during charging and to improve the charging characteristic. This is presumably because the electrolytic solution was not supplied to the electrode body 20 and the electrolytic solution was not exhausted. In addition, by increasing the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30, it was possible to suppress the reaction resistance during discharge and improve the discharge characteristics. This is advantageous for discharge because the decrease in the hydrostatic pressure of the electrolytic solution is suppressed even when the electrolytic solution is reduced, and the electrolytic solution penetrates into the pores inside the air electrode 23 having water repellency. This is probably due to the formation of many three-phase interfaces.

  Although the description of the embodiment has been completed above, the present invention is not limited to the above-described embodiment. For example, the air secondary battery 1 has been described by taking a hydrogen-air secondary battery as an example, but the battery reaction at the air electrode 23 is the same in other air secondary batteries using an alkaline electrolyte, and can be applied. It is. Moreover, although the said air secondary battery 1 was osmose | permeated to the pore in the air electrode 23 with the hydrostatic pressure of electrolyte solution, even if it adjusts the pressure of electrolyte solution using a pump etc., the same effect is obtained.

DESCRIPTION OF SYMBOLS 1 Air secondary battery 10 Battery case 11 Storage part 12 Ventilation hole 13 Cover body 14 Gasket 20 Electrode body 21 Negative electrode 22 Separator 23 Air electrode 24 Water-repellent film 30 Electrolyte storage part 40 Connection part 130 Ventilation path

Claims (4)

An electrode body in which an air electrode and a negative electrode are laminated via a separator;
A housing that houses the electrode body together with an alkaline electrolyte;
An electrolyte storage unit that communicates with the housing, stores the alkaline electrolyte that increases during charging, and supplies the alkaline electrolyte that decreases during discharge; and
The air secondary battery, wherein the alkaline electrolyte has a liquid level height higher than that of the uppermost surface of the air electrode. The air secondary battery according to claim 1, further comprising a water-repellent film that allows air to pass therethrough and does not pass the alkaline electrolyte.
The casing is formed with a vent hole that conducts air inside and outside,
The water repellent film is an air secondary battery in which one surface side is in contact with the air electrode and the other surface side is disposed so as to cover the vent from the inside of the housing.   The air secondary battery according to claim 2, wherein the casing is formed with a plurality of the vents, and further, a ventilation path is formed to communicate the plurality of vents along the surface of the water repellent film. Air secondary battery.   The air secondary battery according to any one of claims 1 to 3, wherein the alkaline electrolyte solution level in the electrolyte storage unit is saturated with the amount of absorption of the alkaline electrolyte solution in the air electrode. The air secondary battery which is lower than the liquid level height of the alkaline electrolyte in the electrolyte reservoir in the state.

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