JP6761655B2 - Air secondary battery - Google Patents

Description

The present invention relates to an air secondary battery capable of charging and discharging.

An air battery using oxygen in the atmosphere as a positive electrode active material has been attracting attention in recent years as an energy conversion device having a high energy density and being easy to be miniaturized and lightened.

As such an air battery, a zinc-air primary battery used as a power source for hearing aids and the like is well known. Further, the rechargeable air secondary battery is expected to be put into practical use as a new secondary battery that exceeds the capacity density of the conventional lithium ion battery. However, in an air secondary battery using a negative electrode metal, the dissolution and precipitation reaction of the negative electrode metal is repeated along with a chemical reaction (hereinafter referred to as a battery reaction) during charging and discharging, and the negative electrode metal is deposited in a dendritic shape, so-called dendrite. Since it grows, it has a problem of causing an internal short circuit, and 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 hydrogen as a negative electrode active material is known (see, for example, Patent Document 1 and Non-Patent Document 1. Hereinafter, a hydrogen air secondary battery is referred to. ). 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 stored and released in this hydrogen storage alloy, so that the dissolution and precipitation reaction of the hydrogen storage alloy itself accompanying the battery reaction occurs. It does not occur, and the problem of internal short circuit due to dendrite growth as described above does not occur. Therefore, the hydrogen air secondary battery is considered to be close to practical use among the air secondary batteries.

In an air secondary battery that uses an alkaline electrolytic solution like the hydrogen air secondary battery described above, a charge / discharge reaction represented by the following equation occurs at the air electrode.
_{Discharge: O 2 + 2H 2 O +} 4e - → 4OH - ··· (1)
_{^{Charge: 4OH - → O 2 + 2H}} 2 O + 4e - ··· (2)
The air electrode of a hydrogen air secondary battery reduces oxygen as represented by the reaction formula (1) to generate hydroxide ions during discharge, and oxygen as represented by the reaction formula (2) during charging. And produce water. Oxygen generated at the air electrode is released into the atmosphere from the part of the air electrode that is open to the atmosphere. As described above, in the hydrogen air secondary battery, the amount of water in the electrolytic solution changes according to the battery reaction during charging and discharging.

Japanese Unexamined Patent Publication No. 2012-64477

M. Morimitsu, T.M. Kondo, N.M. Osada, K.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, and the air electrode becomes the electrolytic solution. In a dry state where they are not in contact with each other, there is a problem that the discharge voltage drops.

However, as described above, the air electrode of the hydrogen air secondary battery consumes water at the time of discharge and generates water at the time of charging, so that it is difficult to maintain the three-phase interface in a good state. For this reason, in a 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 original purpose of increasing the capacity cannot be achieved.

Further, as described above, the air electrode of a hydrogen air secondary battery is water repellent in order to secure an air diffusion path because the progress of the battery reaction is hindered in the absence of oxygen (gas phase). It is made of the material that it has. Therefore, the air electrode has low water absorption of the electrolytic solution, and it is necessary to sufficiently supply the electrolytic solution to the air electrode in order to perform stable discharge especially at the time of discharge when the electrolytic solution decreases.

However, if the electrolytic solution is not sufficiently supplied to the air electrode, the electrolytic solution in the electrode body is depleted and the three-phase interface in the air electrode cannot be maintained well, so that the discharge voltage increases due to the increase in internal resistance. There is a risk that it will decrease.

The present invention has been made in view of such a situation, and an object of the present invention is an air secondary battery capable of maintaining a good three-phase interface in an air electrode and performing stable charging and discharging. Is to provide.

<First aspect of the present invention>
In the first aspect of the present invention, an electrode body in which an air electrode and a negative electrode are laminated via a separator, a housing containing the electrode body together with an alkaline electrolytic solution, and the housing are communicated with each other for charging. It is provided with an electrolytic solution storage unit that stores the alkaline electrolytic solution that increases with time and supplies the alkaline electrolytic solution that decreases during discharge, and the liquid level height of the alkaline electrolytic solution in the electrolytic solution storage unit is the air electrode. It is an air secondary battery that is higher than the top surface of.

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

As a result, according to the first aspect of the present invention, the hydrostatic pressure of the electrolytic solution at the air electrode can be increased, so that the three-phase interface in the air electrode can be well maintained and stable charging / discharging can be performed. The effect of being able to provide an air secondary battery that can be obtained can be obtained.

<Second aspect of the present invention>
A second aspect of the present invention further includes, in the first aspect of the present invention described above, a water-repellent membrane that allows air to permeate and does not permeate the alkaline electrolyte, and the housing conducts air inside and outside. The water-repellent membrane is an air secondary battery in which a vent is formed, and the one side is in contact with the air electrode and the other side is arranged so as to cover the vent from the inside of the housing.

Since the air electrode housed inside the air secondary battery absorbs oxygen during charging and releases oxygen during discharging, the housing is provided with a vent for conducting air inside and outside. Further, the air secondary battery is provided with a water-repellent film that allows air to pass through but does not allow the electrolytic solution to pass through. Since the water-repellent film is arranged so that one side is in contact with the air electrode and the other side covers the vent from the inside of the housing, air can be moved between the outside of the housing and the air pole. Functions as a gas diffusion layer. Further, while the air electrode has appropriate water repellency so as to be advantageous for forming the three-phase interface, the water-repellent membrane does not allow the electrolytic solution to permeate, so that the electrolytic solution inside the housing overflows from the vent. It can be prevented from appearing. Therefore, the air secondary battery can prevent a decrease in the electrolytic solution due to leakage of the electrolytic solution from the housing even when the electrolytic solution increases during charging.

Thereby, according to the second aspect of the present invention, in addition to the action and effect according to the first aspect of the present invention described above, even if the hydrostatic pressure of the electrolytic solution inside the housing is increased, the leakage of the electrolytic solution is prevented. The effect of being able to provide an air secondary battery can be obtained.

<Third aspect of the present invention>
A third aspect of the present invention is that in the second aspect of the present invention described above, the housing is formed with a plurality of the vents, and the plurality of vents are communicated along the surface of the water-repellent film. It is an air secondary battery in which a ventilation path is formed.

The housing of the air secondary battery is formed with a plurality of vents for conducting air inside and outside. Then, since the housing is further formed with a ventilation path for communicating the plurality of ventilation holes, the air entering the inside of the housing from one of the ventilation holes passes through the ventilation path while touching the water-repellent membrane. , It will come out from the other vent to the outside of the housing. Further, the ventilation path is formed along the surface of the water-repellent membrane. As a result, the water-repellent membrane can smoothly transfer air to and from 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 third aspect of the present invention, in addition to the action and effect according to the first or second aspect of the present invention described above, the possibility of lack of oxygen in the battery reaction at the air electrode can be reduced. Is obtained.

<Fourth aspect of the present invention>
A fourth aspect of the present invention is that in any one of the first to third aspects of the present invention described above, the liquid level height of the alkaline electrolytic solution in the electrolytic solution storage unit is the alkaline electrolytic solution at the air electrode. This is an air secondary battery whose absorption amount is lower than the liquid level of the alkaline electrolytic solution in the electrolytic solution storage unit in a saturated state.

The air electrode can maintain a good three-phase interface by allowing the electrolytic solution to appropriately permeate the pores inside. In a state where the hydrostatic pressure of the electrolytic solution at the air electrode is excessively increased, the absorption amount of the electrolytic solution at the air electrode may be saturated because all the internal pores are filled with the electrolytic solution. When the absorption amount of the electrolytic solution is saturated, the air electrode deviates from the three-phase interface in the ideal state because the oxygen existing inside is reduced. Therefore, the hydrostatic pressure in a state where the absorption amount of the electrolytic solution at the air electrode is saturated is obtained in advance, and the upper limit of the liquid level height of the electrolytic solution in the electrolytic solution storage portion is set so as not to reach the hydrostatic pressure. It is possible to easily maintain the three-phase interface in an ideal state.

As a result, according to the fourth aspect of the present invention, in addition to the action and effect according to 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 filling is performed. The effect of being able to provide an air secondary battery capable of discharging can be obtained.

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 line AA in FIG. It is sectional drawing which shows typically the pore of an air electrode. It is a graph which shows the charging characteristic. It is a graph which shows the discharge characteristic.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, in FIGS. 1 and 2, each direction of the three-dimensional space is indicated by reference numerals X, Y, and Z.
FIG. 1 is a cross-sectional view of the air secondary battery 1 according to the present invention in the XX plane. 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 a "housing", an electrolytic solution storage unit 30, and a connecting unit 40.

The battery case 10 has an accommodating portion 11 formed inside, and a vent 12 for conducting air is formed between the outside of the battery case 10 and the accommodating portion 11. In this embodiment, two vents 12 are formed at positions separated from each other in the X direction of the battery case 10. Further, the battery case 10 is provided with a lid 13 at a position connecting the two vents 12.

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

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

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

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

The water-repellent film 24 is made of a material that allows air to pass through but does not allow the electrolytic solution to pass through, is placed on the air electrode 23, and is arranged so that the upper surface is in contact with the two vents 12 and the lid 13. As shown in FIG. 2, the lid 13 has a shape having a plurality of peaks and valleys in a cross section in the ZZ plane, and the valley portions constitute a plurality of ventilation passages 130 in the X direction in which the two vents 12 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 from one of the two vents 12 to the other through the vent 130. The air flowing through the air passage 130 diffuses inside the water-repellent membrane 24 facing the air passage 130. Then, the water-repellent film 24 allows the air diffused inside to permeate through the air electrode 23 which is in direct contact with the air electrode 23. As a result, the water-repellent film 24 functions as a gas diffusion layer. Further, the water-repellent membrane 24 allows oxygen generated from the air electrode 23 to permeate through the air passage 130. Oxygen that has permeated through the ventilation path 130 is released into the atmosphere outside the battery case 10 through the ventilation port 12.

Here, it is preferable that the battery case 10 forcibly forms an air flow between the two vents 12 by providing, for example, a blower. 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, the electrolytic solution inside the battery case 10 is prevented from permeating through the vent 12 and the vent 130 by the water-repellent film 24. Therefore, when the pressure of the electrolytic solution inside the battery case 10 rises, 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 inside and is connected to the battery case 10 via the connecting unit 40. Since the inside of the electrolyte storage unit 30 and the storage unit 11 of the battery case 10 are connected to each other, the electrolyte can move between the two. Therefore, when the electrolytic solution increases due to the air electrode 23 generating water during charging, the excess electrolytic solution inside the accommodating unit 11 is moved to the electrolytic solution storage unit 30 and stored. Further, when the electrolytic solution is reduced due to the decomposition of water by the air electrode 23 during discharge, the electrolytic solution stored in the electrolytic solution storage unit 30 moves to the storage unit 11 to reduce the shortage of the electrolytic solution in the air electrode 23. Can be supplemented.

Next, the three-phase interface at 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 pores having a diameter d, and the three-phase interface at the moment when air is present on one side of the pores and the electrolytic solution 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 Will be done.
_PO = 4γcosΘ / d ... (3)
In the formula (3), the value of cos Θ increases as the degree of water repellency of the air electrode 23 increases, and the osmotic pressure _PO increases. The higher the diameter d of the pores is less osmotic pressure P _O is increased. Therefore, the pressure required to appropriately permeate the electrolytic solution into the pores of the air electrode 23 depends on the degree of water repellency of the air electrode 23 and the pore size distribution. Then, in order for the electrolytic solution to permeate into the pores of the air electrode 23 and maintain a good three-phase interface, the pressure of the electrolytic solution is expressed by the formula (3) even when the electrolytic solution is reduced especially during discharge. ) it must be higher than the osmotic pressure P _O, represented by.

Here, as shown in FIG. 1, in the air secondary battery 1, the liquid level height in the electrolytic solution storage unit 30 is set higher by the 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 accommodating unit 11 of the battery case 10, and the negative electrode 21 and the separator 22 allow the electrolytic solution to permeate. 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 gravitational acceleration. 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, when the liquid level height in the electrolytic solution storage unit 30 is higher than the uppermost surface of the air electrode 23, the osmotic pressure required for the electrolytic solution to permeate the pores of the air electrode 23 in 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 perform stable discharge without depleting the electrolytic solution inside the air electrode 23 even at the time of discharge when the electrolytic solution is reduced.

On the other hand, when the electrolytic solution increases during charging, the electrolytic solution excessively generated in the air electrode 23 moves to the electrolytic solution 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 ventilation path 130 from the inside of the battery case 10, the electrolytic solution remains in the battery case even when the pressure of the electrolytic solution rises. The risk of leakage to the outside of 10 can be reduced. As a result, for example, even if a gap between the air electrode 23 and the battery case 10 or a crack occurs in the air electrode 23 itself due to repeated charging and discharging, it is possible to prevent a decrease due to leakage of the electrolytic solution.

Further, when the amount of the electrolytic solution absorbed by the air electrode 23 is saturated as described above, all the pores inside the air electrode 23 are filled with the electrolytic solution, and the area of the three-phase interface is larger than the optimum value. There is a risk that it will decrease. Therefore, it is preferable that the upper limit of the height of the electrolytic solution in the electrolytic solution storage unit 30 is set within a range that does not cause such a state. 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. Then, in the manufacturing process of the air secondary battery 1 used for charging / discharging, the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30 is set between 0 and _HL when the electrolytic solution is poured. As a result, the air secondary battery 1 can suppress excessive permeation of the electrolytic solution into the air electrode 23, and reduce the possibility that the discharge voltage is lowered due to the area of the three-phase interface being reduced from the optimum value. Can be done.
[Example]

1. 1. Manufacture of air secondary battery 1 (Example 1)
(1) Manufacture of air electrode 23 (catalyst synthesis)
As the catalyst of the air electrode 23, a Baicloa-type bismuth iridium oxide having a dual catalytic activity for oxygen evolution and oxygen reduction was used. Bi (NO _{4) 3} · 5H and ₂ O and H ₂ IrCl ₆ · 6H ₂ O was dissolved in 75 ° C. of distilled water to the same concentration, stirred and mixed, NaOH aqueous solution of 2 mol% / L Was added. The bath temperature at this time was 75 ° C., and the mixture was stirred for 3 days while performing oxygen publing. The solution containing the resulting precipitate was maintained at 85 ° C. and evaporated to dryness to form a paste. The paste-like 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 environment of 600 ° C. in an air atmosphere for 2 hours. Further, in order to remove the by-products contained in the calcined product, suction filtration was performed using distilled water at 70 ° C. to isolate a bismuth iridium oxide of the Baicloa type. Further, this was dried in an environment of 120 ° C. for 12 hours and then pulverized using a mortar to synthesize a catalyst for the air electrode 23.

(Air electrode plate)
The bismuth iridium oxide powder thus obtained, nickel powder (particle size 10 to 20 μm), and commercially available PTFE particles were mixed so as to have 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 firing at 370 ° C. for 13 minutes in a nitrogen gas atmosphere, the air electrode 23 was prepared 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 an argon gas atmosphere in a high-frequency induction melting furnace, poured into a mold, and cooled to room temperature to obtain an alloy ingot. Further, this 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 and sieved in an inert atmosphere to obtain a hydrogen storage alloy powder having a particle size of 60 μm.

(Negative electrode plate)
0.2 parts by mass of sodium polyacrylate, 0.04 parts by mass of carbosimyl cellulose, 30 parts by mass of styrene butadiene rubber (SBR) disversion, and 0 carbon black with respect to 100 parts by mass of the obtained hydrogen storage alloy powder. 5.5 parts by mass and 22.4 parts by mass of water were added and kneaded to prepare a paste of the negative electrode mixture. This active material slurry was filled with foamed nickel, dried, and then rolled to increase the amount of alloy per volume, and cut into a predetermined size to prepare a negative electrode 21.

(Measurement of negative electrode capacity)
The negative electrode 21 produced in the above step, the sintered nickel hydroxide positive electrode having a sufficiently large capacity with respect to the negative electrode 21, and the separator 22 for a nickel-metal hydride battery are combined, inserted into an acrylic case, and a fixed amount of electrolytic solution is injected. A unipolar cell of a nickel-metal hydride secondary battery with a negative electrode capacity regulation was prepared. After resting this unipolar cell for 5 hours, charging it at 0.5 It for 2.8 hours, discharging it at the same rate (final voltage = 0.70V), and repeating this multiple times, the maximum value of the battery capacity obtained is obtained. The capacity of the negative electrode 21 was set. At this time, the capacity of the negative electrode 21 was 640 mAh.

(3) Configuration of Housing Unit 11 The negative electrode 21 (40 mm × 40 mm, thickness 0.25 mm) whose capacity was measured in the above step, the separator for nickel-metal hydride battery, and the air electrode 23 (40 mm ×) produced in the above step. 40 mm (40 mm, 0.2 mm thick) and a carbon non-woven fabric (45 mm × 45 mm, 0.2 mm thick) water-repellent treated with PTFE and carbon were stacked in this order and placed in the housing portion 11 of the battery case 10. By attaching the lid 13, it was fixed so as to be pressed from the Z direction. By using a 5 mol / L KOH aqueous solution as an electrolytic solution and pouring it into the electrolytic solution storage unit 30, 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 when the height of the uppermost surface of the air electrode was used as a reference became 10 mm, and the air secondary battery 1 was used. The amount of the electrolytic solution poured at this time was about 50 mL.

(Battery characteristic evaluation)
The air secondary battery 1 having the above configuration is allowed to stand in an environment of 25 ° C. for 1 hour, and after the electrode body 20 absorbs the electrolytic solution, it is charged 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 (final voltage = 0.00V) at the same rate. Then, the cell voltage during charging and discharging was measured. Through the charging and discharging of the examples, 0.8 mL of air was constantly flowing through the ventilation path 130 per minute.

(Example 2)
After the completion of charging and discharging in Example 1, the air secondary battery 1 of Example 1 is allowed to stand for 1 hour, and the height H of the electrolytic solution in the electrolytic solution storage unit 30 is reset to 5 mm. As a result, the air secondary battery 1 of Example 2 was obtained. Then, the air secondary battery 1 of Example 2 was charged and discharged for one cycle in the same manner as in Example 1 to evaluate the battery characteristics.

(Example 3)
After the completion of charging and discharging in Example 2 above, the air secondary battery 1 of Example 2 is allowed to stand for 1 hour, and the height H of the electrolytic solution in the electrolytic solution storage unit 30 is reset to 0 mm. As a result, the air secondary battery 1 of Example 3 was obtained. Then, the air secondary battery 1 of Example 3 was charged and discharged for one cycle in the same manner as in Example 1 to evaluate the battery characteristics.

(Comparative Example 1)
After the charging / discharging in Example 3 is completed, the air secondary battery 1 of Example 3 is allowed to stand for 1 hour, and the electrolytic solution in the electrolytic solution storage unit 30 is reconstituted so that the liquid level H of the electrolytic solution becomes −10 mm. By setting, the air secondary battery 1 of Comparative Example 1 was used. Then, the air secondary battery 1 of Comparative Example 1 was charged and discharged for one cycle in the same manner as in Example 1 to evaluate the battery characteristics. In Comparative Example 1, although the height of the electrolytic solution in the electrolytic solution storage section 30 is lower than that of the bottom surface of the accommodating section 11, at least the separator 22 and the negative electrode 21 hold the electrolytic solution, so that charging and discharging are performed. It is possible in itself.

2. 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 represents the charging capacity increased by charging the air secondary battery 1, and the vertical axis represents the cell voltage at that time. When the air secondary battery 1 is charged to a certain charge capacity, the secondary battery whose cell voltage rises has a higher internal reaction resistance, and it is necessary to apply a higher voltage during charging. From FIG. 4, the charging characteristics are almost the same 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 is performed. The voltage was 2.0 mV higher than the charging voltage of Example 1. The charging voltage of Comparative Example 1 was 17.3 mV higher than the charging voltage of Example 1.

(2) Discharge Characteristics FIG. 5 is a graph showing discharge characteristics in Examples 1 to 3 and Comparative Example 1. In FIG. 5, the horizontal axis represents the charge capacity that is reduced by discharging the air secondary battery 1, and the vertical axis represents the cell voltage at that time. When the air secondary battery 1 is discharged to a certain discharge capacity, the secondary battery in which the cell voltage drops further has a higher internal reaction resistance, and it becomes impossible to output a high voltage at the time of discharging. 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 discharged to 50% of the charge capacity of the air secondary battery 1 is the discharge voltage, the discharge voltage of the second embodiment is 4.4 mV lower than the discharge voltage of the first embodiment. 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. 3. Consideration of characteristic evaluation From the above evaluation results, it was possible to suppress the reaction resistance during charging and improve the charging characteristics by increasing the liquid level height H of the electrolytic solution in the electrolytic solution storage unit 30. It is considered that this is because the electrolytic solution was promptly supplied to the electrode body 20 and the electrolytic solution was not exhausted. Further, 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 at the time of discharge and improve the discharge characteristics. This is advantageous for electric discharge because the decrease in the hydrostatic pressure of the electrolytic solution is suppressed and the electrolytic solution permeates into the pores inside the water-repellent air electrode 23 even at the time of discharge when the electrolytic solution decreases. It is considered that this is due to the formation of many three-phase interfaces.

Although the description of the embodiment is completed above, the present invention is not limited to the above embodiment. For example, the above-mentioned 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 electrolytic solution, and the application is possible. Is. Further, the above-mentioned air secondary battery 1 is permeated into the pores in the air electrode 23 by the hydrostatic pressure of the electrolytic solution, but the same effect can be obtained even if the pressure of the electrolytic solution is adjusted by using a pump or the like.

1 Air secondary battery 10 Battery case 11 Storage part 12 Vent 13 Lid body 14 Gasket 20 Electrode body 21 Negative electrode 22 Separator 23 Air electrode 24 Water repellent membrane 30 Electrolyte storage part 40 Connection part 130 Ventilation path

Claims (2)

An electrode body in which the air electrode and the negative electrode are vertically laminated via a separator,
A housing that houses the electrode body together with the alkaline electrolytic solution,
An electrolytic solution storage unit that communicates with the space between the housing and the electrode body, stores the alkaline electrolytic solution that increases during charging, and supplies the alkaline electrolytic solution that decreases during discharge.
A water-repellent membrane that allows air to permeate and does not permeate the alkaline electrolytic solution.
The housing is formed with vents that conduct air inside and outside.
The water-repellent membrane is arranged so that one side is in contact with the air electrode and the other side covers the vent from the inside of the housing.
The liquid level of the alkaline electrolyte of the electrolyte reservoir, the rather high than the top surface of the air electrode, the absorption amount of the alkaline electrolyte in the air electrode of the electrolyte storage unit in a state saturated An air secondary battery that is lower than the liquid level of the alkaline electrolyte . In the air secondary battery according to claim 1, the housing is formed with a plurality of the vents, and further, a vent is formed along the surface of the water-repellent film to communicate the plurality of vents. Air secondary battery.

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