Zinc-air secondary battery system

Abstract

The air-zinc secondary battery system of the present invention comprises an air-zinc battery array in a rectangular case, in which a plurality of air-zinc battery cells are connected, each having an air positive electrode part, a separator, and a zinc gel negative electrode part containing an electrolyte, an external electrolyte tank for storing electrolyte, and an electrolyte transport part configured to flow electrolyte from the external electrolyte tank into the zinc gel negative electrode part in each air-zinc battery cell, thereby circulating the electrolyte in the external electrolyte tank and the electrolyte in the zinc gel negative electrode part. The external electrolyte tank and the case are provided with gas vents, and the case is provided with an electrolyte inlet part for flowing electrolyte from the external electrolyte tank into the zinc gel negative electrode part, and an electrolyte outlet part for flowing electrolyte in the zinc gel negative electrode part to the outside, and the electrolyte outlet part is provided at a position higher than the position where the electrolyte inlet part is provided.

Description

[Technical field]

[0001] The present invention relates to an air-zinc secondary battery system having an electrolyte and gas flow system. [Background technology]

[0002] An electrochemical power source means a device in which electrical energy can be generated by an electrochemical reaction, and an air-zinc secondary battery also falls under the category of electrochemical power sources. An air-zinc secondary battery employs a zinc gel anode made of zinc gel that is converted to zinc oxide during discharge, and employs an air cathode in the form of a membrane that is a permeable membrane containing water molecules and that generates hydroxide ions when in contact with oxygen in the air as the cathode. In addition, a separation membrane (separator) is disposed between the air cathode and the zinc gel anode. The separator is a member that prevents an internal short circuit caused by direct contact between the air cathode and the zinc gel anode, and plays an important role not only in the ion passage within the battery but also in improving the safety of the battery.

[0003] Such zinc-air secondary batteries have many advantages over conventional hydrogen fuel cells. In particular, because fuels such as zinc are abundant in the form of metals and their oxides, the energy supply provided by the zinc-air secondary battery is not visibly depleted. In addition, whereas conventional hydrogen fuel cells require recharging, zinc-air secondary batteries can be electrically recharged and used, and have the advantage of being able to deliver a higher output voltage (1.4V) than conventional fuel cells (<0.8V).

[0004] In air-zinc secondary batteries, a slurry-type electrolyte solution is generally used, which is a mixture of zinc (Zn), potassium hydroxide (KOH) and water (H2O). The electrolyte solution is contained inside the zinc gel negative electrode part, and the electrolyte solution passes through the separator to impregnate a part of the air positive electrode part, forming a gas-liquid interface. The air-zinc secondary battery configured as above operates by the movement of electrons generated when the zinc contained in the electrolyte solution reacts with oxygen in the air and changes to zinc oxide.

[0005] In the conventional air-zinc secondary battery as described above, the water in the electrolyte is consumed during the discharge of the air-zinc secondary battery, and the concentration of potassium hydroxide in the electrolyte increases. As a result, potassium hydroxide is precipitated in the air positive electrode, the air positive electrode is destroyed, and the performance of the air-zinc secondary battery is reduced. Furthermore, the rapid change in the concentration of the electrolyte causes zinc dendrite to form in the zinc gel negative electrode, which further reduces the performance of the air-zinc secondary battery.

[0006] Therefore, a system for maintaining an optimal electrolyte concentration in such air-zinc secondary batteries is needed.

[0007] In addition, in the case of a zinc-air secondary battery that can be discharged and recharged, the zinc in the zinc gel negative electrode turns into zinc oxide as the discharge proceeds, and conversely, when recharging, oxygen in the zinc oxide is separated and discharged, returning it to its original state as zinc. In other words, when sufficient discharge is performed, it is recognized that the higher the oxygen discharge efficiency of the zinc gel negative electrode, the higher the charging performance of the zinc-air secondary battery.

[0008] Therefore, in order to improve the charging performance of an air-zinc secondary battery, a system is required that supplies oxygen gas to the air positive electrode during discharging and discharges the oxygen gas to the outside of the air-zinc secondary battery during recharging. Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide an air-zinc secondary battery system that can maintain optimal electrolyte concentration, efficiently supply oxygen gas to the air-zinc secondary battery during discharge, and efficiently discharge oxygen gas from the air-zinc secondary battery during recharge. [Means for solving the problem]

[0010] These objects can be achieved by the present invention described below in (1) to (7).

[0011] (1) An air-zinc battery array including a plurality of air-zinc battery cells connected together in a rectangular case, the air-zinc battery cells each having an air positive electrode portion, a separator, and a zinc gel negative electrode portion containing an electrolyte therein; an external electrolyte tank for storing an electrolyte; and an electrolyte transport unit configured to flow the electrolyte from the external electrolyte tank into the zinc gel negative electrode portion in each of the air-zinc battery cells, thereby circulating the electrolyte in the external electrolyte tank and the electrolyte in the zinc gel negative electrode portion; the external electrolyte tank and the case are provided with gas vents; The case includes an electrolyte inlet portion for allowing the electrolyte from the external electrolyte tank to flow into the zinc gel negative electrode portion, and an electrolyte outlet portion for allowing the electrolyte from the zinc gel negative electrode portion to flow out to the outside, The air-zinc secondary battery system is characterized in that the electrolyte outlet is disposed at a position higher than a position at which the electrolyte inlet is provided.

[0012] (2) An air-zinc secondary battery system as described in (1) above, in which the electrolyte outlet portion of one of the air-zinc battery cells and the electrolyte inlet portion of the other of the air-zinc battery cells are connected to each other.

[0013] (3) The air-zinc secondary battery system described in (1) above, wherein the separator is composed of nonwoven fibers formed from a polymer solution using an electrospinning method.

[0014] (4) As the polymer solution, a mixture of Nafion and a polyacrylic acid solution is used, The air-zinc secondary battery system according to the above (1), wherein the nonwoven fiber has a sulfur skeleton derived from a Nafion structure and a rigid structure derived from polyacrylic acid.

[0015] (5) An air-zinc secondary battery system according to the above (1), wherein the zinc gel negative electrode portion contains an elastic conductive material. (6) The air-zinc secondary battery system according to (1) above, wherein the elastic conductive material is at least one of expanded graphite and graphene.

[0016] (7) The air-zinc secondary battery system described in (1) above, wherein the air positive electrode portion has a slow oxygen transport membrane used when charging the air-zinc battery cell, and a fast oxygen transport membrane used when discharging the air-zinc battery cell and having a higher oxygen transport capacity than the slow oxygen transport membrane. Effect of the Invention

[0017] According to the present invention, the electrolyte contained in the zinc gel negative electrode part and the electrolyte in the external electrolyte tank are circulated, thereby maintaining the concentration of the electrolyte in the air-zinc battery cell, more specifically, the concentration of potassium hydroxide in the electrolyte. In particular, in the present invention, the electrolyte outlet part for discharging the electrolyte in the zinc gel negative electrode part to the outside is disposed at a higher position than the electrolyte inlet part for discharging the electrolyte from the external electrolyte tank into the zinc gel negative electrode part. Therefore, by operating the electrolyte transport part, the electrolyte with a relatively high concentration of potassium hydroxide that has accumulated in the lower part of the zinc gel negative electrode part can be discharged from the electrolyte outlet part located at the upper part of the zinc gel negative electrode part. As a result, the electrolyte concentration of the entire zinc gel negative electrode part is maintained, and as a result, the precipitation of potassium hydroxide in the air positive electrode part can be suppressed, and the formation of zinc dendrite in the zinc gel negative electrode part can be suppressed. In addition, oxygen gas can be supplied to the air positive electrode part during discharging, and oxygen gas can be discharged to the outside of the air-zinc secondary battery during recharging. As a result, it is possible to provide an air-zinc secondary battery system that has high charging performance and maintains a high output voltage for a long period of time. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing a preferred embodiment of the air-zinc secondary battery system of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the internal structure of an air-zinc battery cell provided in the air-zinc secondary battery system of FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the zinc-air battery cell of FIG. [Figure 4] FIG. 4 is a cross-sectional view that shows a schematic diagram of another configuration example of the air-zinc battery cell provided in the air-zinc secondary battery system of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention can be modified in various ways and can have various embodiments, and a specific embodiment will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, and it should be understood that the present invention includes all modifications, equivalents, or alternatives within the spirit and technical scope of the present invention. In describing the present invention, if it is determined that a detailed description of related publicly known technology may make the gist of the present invention unclear, the detailed description will be omitted.

[0020] The terms used in this application are merely used to describe certain embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In this application, the terms "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0021] Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another.

[0022] Hereinafter, the air-zinc secondary battery system of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0023] Fig. 1 is a schematic diagram showing a preferred embodiment of the air-zinc secondary battery system of the present invention. Fig. 2 is a schematic diagram showing the internal structure of an air-zinc battery cell provided in the air-zinc secondary battery system of Fig. 1. Fig. 3 is a cross-sectional view of the air-zinc battery cell of Fig. 2.

[0024] As shown in Figure 1, the air-zinc secondary battery system 1 of this embodiment has an air-zinc battery array 100 consisting of a plurality of air-zinc battery cells 10 connected in series, an external electrolyte tank (not shown), and an electrolyte transport section 20 that circulates the electrolyte in the external electrolyte tank and the electrolyte in each air-zinc battery cell 10. Prior to a detailed description of the air-zinc secondary battery system 1 of this embodiment, each air-zinc battery cell 10 included in the air-zinc secondary battery system 1 will be described.

[0025] <Zinc-air battery cell> As shown in Figures 2 and 3, the air-zinc battery cell 10 has a rectangular case 11 and, arranged within the rectangular case 11, an air positive electrode portion 11, a separator 13, and a zinc gel negative electrode portion 14 containing an electrolyte therein.

[0026] The case 11 has a rectangular shape and has a cell storage section 111 in the center thereof for storing the air positive electrode section 11, the separator 13, and the zinc gel negative electrode section 14. A plurality of gas vent holes 112 for supplying air (oxygen) to the air positive electrode section 11 are formed on the surface of the cell storage section 111 on the side where the air positive electrode section 11 is disposed.

[0027] In addition, the case 11 is provided with an electrolyte inlet 113 that allows electrolyte from an external electrolyte tank to flow into the zinc gel negative electrode portion 14, and an electrolyte outlet 114 that allows electrolyte from the zinc gel negative electrode portion 14 to flow out to the outside. In this embodiment, the electrolyte inlet 113 and the electrolyte outlet 114 are arranged symmetrically with respect to the center of the case 11, and the electrolyte outlet 114 is arranged at a higher position than the electrolyte inlet 113.

[0028] In addition, auxiliary electrolyte reservoirs 30 are provided on both sides of the cell storage section 111 via lattice filters 40. Each auxiliary electrolyte reservoir 30 is filled with a plurality of filters (not shown), and impurities in the electrolyte are filtered through these filters and the lattice filters 40. The case 11 is also provided with exposed terminal portions (not shown) for passing current from the air-zinc battery cell 10 during discharge and for applying voltage to the air-zinc battery cell 10 during recharge.

[0029] The air cathode part 12 is composed of an air diffusion layer, a catalytic active layer, and a cathode current collector layer, as is commonly known. The air diffusion layer is preferably made of a hydrophobic membrane material such as polytetrafluoroethylene (PTFE) to prevent moisture and carbon dioxide in the external air from entering the battery and extend the life of the air-zinc secondary battery. The catalytic active layer is made of a carbon material that reacts with the inflowing oxygen to cause a reaction according to Chemical Formula 1 below. The cathode current collector layer collects electrons generated by the chemical reaction of the catalytic active layer, and is preferably a mesh structure made of a conductive material such as metal.

[0030] [ka]

[0031] The separator 13 is interposed between the air positive electrode part 12 and the zinc gel negative electrode part 14 to prevent a short circuit between the air positive electrode part 12 and the zinc gel negative electrode part 14. It also plays a role in transmitting hydroxide ions generated by a chemical reaction with oxygen in the catalytic active layer of the air positive electrode part 12 to the negative electrode part.

[0032] As the separator 13, a membrane formed from a resin material such as polypropylene having ion permeability can be used, but it is preferable to use nonwoven fibers formed from a polymer solution using an electrospinning method.

[0033] Conventionally, membranes used as separators (e.g., propylene membranes) cannot control selective ion transport, and potassium ions (K + In contrast, the use of separator 13 made of nonwoven fibers formed from a polymer solution using an electrospinning method prevents the transport of certain ions such as potassium ions (K + ) can be prevented from transporting certain ions.

[0034] More specifically, a mixture of Nafion and a polyacrylic acid solution is used as the polymer solution, and nonwoven fibers are formed by an electrospinning method, and the nonwoven fibers are used to form the separator 13. Nafion is a copolymer of tetrafluoroethylene and perfluoro-2-(2-fluorosulfonylethoxy)propylvinyl ether.

[0035] The nonwoven fiber formed by the electrospinning method has a sulfur skeleton derived from the Nafion structure and a rigid structure derived from polyacrylic acid. This sulfur skeleton transports protons (H + ) transport channel. Each ion is a hydroxide ion (OH - ), potassium ions in the electrolyte are prevented from migrating to the air positive electrode portion 11. In addition, because potassium ions are prevented from migrating to the air positive electrode portion 11, the formation of water, which is advantageous for stabilizing the electrolyte concentration, is promoted. As a result, the concentration of the electrolyte is maintained, and the precipitation of potassium hydroxide in the air positive electrode portion 12 is suppressed, and the formation of zinc dendrites in the zinc gel negative electrode portion 14 is suppressed.

[0036] The prepared separator 13 is attached to the air positive electrode part 12 by adhering, pressing, or thermal laminating to the positive electrode current collector layer side of the air positive electrode part 12 .

[0037] The zinc gel negative electrode part 14 contains zinc gel in the form of a gel in which zinc (Zn) and an electrolyte are mixed, and functions as an anode by causing the reaction of the following chemical formula 2. The electrolyte in the zinc gel negative electrode part 14 is a slurry-type electrolyte in which zinc (Zn), potassium hydroxide (KOH), and water (H2O) are mixed, and is impregnated in the zinc gel.

[0038] [ka]

[0039] Water molecules are generated in the zinc gel anode part 14 by the reaction of Chemical Formula 2, and the water molecules thus generated move to the air cathode part 12 and are used in the chemical reaction of Chemical Formula 1.

[0040] 3, a plurality of gel retaining pins 141 are provided on the surface of the case 11 opposite to the surface on which the gas vent holes 112 are formed. The zinc gel is retained by the gel retaining pins 141 so as to cover the entire surface of the separator 13.

[0041] In addition, the zinc gel of the zinc gel negative electrode portion 14 preferably contains an elastic conductive material. Such an elastic conductive material may include at least one of expanded graphite and graphene. The zinc gel negative electrode part 14 changes its volume every time it goes through a recharge and discharge cycle. This phenomenon causes the zinc gel negative electrode part 14 to aggregate and the specific surface area to decrease. By including an elastic conductive material in the zinc gel of the zinc gel negative electrode part 14, the zinc gel negative electrode part 14 is prevented from agglomerating, and the charging and discharging characteristics of the air-zinc battery cell 10 can be maintained. Furthermore, by including an elastic conductive material in the zinc gel, a gap is formed which is necessary for more rapid electrolyte exchange between the electrolyte from the external electrolyte tank and the electrolyte in the zinc gel negative electrode portion 14. In addition, the above-mentioned effects can be obtained by incorporating a tension-reinforced zinc alloy coil spring in the zinc gel.

[0042] <Zinc-air secondary battery system> As described above, the air-zinc secondary battery system 1 of this embodiment has an air-zinc battery array 100 consisting of a plurality of air-zinc battery cells 10 connected in series, an external electrolyte tank (not shown), and an electrolyte transport section 20 that circulates the electrolyte in the external electrolyte tank and the electrolyte in each air-zinc battery cell 10.

[0043] As shown in Fig. 1, the air-zinc battery array 100 is formed by connecting four air-zinc battery cells 10 in series. The electrolyte outlet 114 of one air-zinc battery cell 10 and the electrolyte inlet 113 of the other air-zinc battery cell 10 of two adjacent air-zinc battery cells 10 are connected to each other via respective liquid transfer tubes 23, 24, and 25 described later. The number of air-zinc battery cells 10 constituting the air-zinc battery array 100 is not limited, and the air-zinc battery array 100 may be composed of a single air-zinc battery cell 10, or the air-zinc battery array 100 may be composed of any number of air-zinc battery cells 10, two or more.

[0044] The external electrolyte tank has a capacity capable of supplying a sufficient amount of electrolyte to each of the air-zinc battery cells 10, and is filled with unused electrolyte. The external electrolyte tank is also provided with a gas vent hole, through which oxygen gas contained in the electrolyte sent from each of the air-zinc battery cells 10 of the air-zinc battery array 100 can be discharged. The external electrolyte tank has an electrolyte outlet that is connected to the electrolyte supply tube 21 of the electrolyte transport unit 20, and an electrolyte inlet that is connected to the electrolyte supply tube 26 that flows the electrolyte discharged from each air-zinc battery cell 10 of the air-zinc battery array 100. By operating the electrolyte transport unit 20, the external electrolyte tank sends unused electrolyte from the electrolyte outlet and collects electrolyte discharged from each air-zinc battery cell 10 from the electrolyte inlet.

[0045] The electrolyte transport section 20 is configured to flow electrolyte from an external electrolyte tank into the inside of the zinc gel negative electrode section 14 in each air-zinc battery cell 10, circulating the electrolyte in the external electrolyte tank and the electrolyte inside the zinc gel negative electrode section 14. The electrolyte transport section 20 includes a liquid supply pump 200 such as a peristaltic pump, a liquid supply tube 21 connecting the electrolyte outlet of the external electrolyte tank to the liquid supply pump 200, a liquid supply tube 22 connecting the liquid supply pump 200 to the electrolyte inlet 113 of the first air-zinc battery cell 10 of the air-zinc battery array 100 (the first from the front in Figure 1), liquid supply tubes 23, 24, 25 connecting the electrolyte outlet 114 of one of two adjacent air-zinc battery cells 10 to the electrolyte inlet 113 of the other air-zinc battery cell 10, and a liquid supply tube 26 connecting the electrolyte outlet 114 of the last air-zinc battery cell 10 of the air-zinc battery array 100 (the fourth from the front in Figure 3) to the electrolyte inlet of the external electrolyte tank.

[0046] When the liquid supply pump 200 is operated, unused electrolyte from the external electrolyte tank flows into the electrolyte inlet 113 of the first air-zinc battery cell 10 through the liquid supply tubes 21 and 22. Subsequently, the electrolyte in the first air-zinc battery cell 10 and unused electrolyte from the external electrolyte tank are discharged from the electrolyte outlet 114 and flow into the electrolyte inlet 113 of the second air-zinc battery cell 10 through the liquid supply tube 23. In this way, the electrolyte in each air-zinc battery cell 10 is replaced with unused electrolyte from the external electrolyte tank and is discharged from the electrolyte outlet 114 of the last air-zinc battery cell 10. The discharged electrolyte in each air-zinc battery cell 10 is sent to the external electrolyte tank through the liquid supply tube 26.

[0047] In this embodiment, the electrolyte contained in the zinc gel negative electrode portion 14 and the electrolyte in the external electrolyte tank are circulated, thereby maintaining the concentration of the electrolyte in each air-zinc battery cell 10, more specifically, the concentration of potassium hydroxide in the electrolyte. In particular, in the present invention, the electrolyte outlet 114 of each air-zinc battery cell 10 is disposed at a higher position than the electrolyte inlet 113 of each air-zinc battery cell 10. Therefore, by operating the liquid pump 200, the electrolyte with a relatively high concentration of potassium hydroxide that has accumulated at the bottom of the zinc gel negative electrode part 14 can be discharged from the electrolyte outlet 114 located at the top of the zinc gel negative electrode part 14. As a result, the electrolyte concentration of the entire zinc gel negative electrode part 14 is maintained, and the precipitation of potassium hydroxide in the air positive electrode part 12 is suppressed, and the formation of zinc dendrite in the zinc gel negative electrode part 14 can be suppressed. During discharge, oxygen gas can be supplied to the air positive electrode portion 12 through the gas vent hole 112 of the case 11, and during recharge, the oxygen gas can be discharged to the outside of the air-zinc secondary battery together with the electrolyte. As a result of the above-mentioned operations, in the air-zinc secondary battery system 1 of this embodiment, each air-zinc battery cell 10 has high charging performance and can maintain a high output voltage for a long period of time.

[0048] In the above-mentioned embodiment of the air-zinc secondary battery system 1, the electrolyte in the external electrolyte tank and the electrolyte in the air-zinc battery cell 10 are circulated using the liquid pump 200, but the invention is not limited thereto. For example, the electrolyte in the external electrolyte tank and the electrolyte in the air-zinc battery cell 10 may be circulated by utilizing the concentration difference between the electrolytes.

[0049] Also, a configuration may be adopted in which a liquid delivery pump 200 is provided for each air-zinc battery cell 10. Furthermore, a configuration may be adopted in which the electrolyte is circulated between an external electrolyte tank and each air-zinc battery cell 10.

[0050] In the air-zinc battery cell shown in FIG. 3, one air positive electrode portion 12 is disposed on one side of the zinc gel negative electrode portion 14, but the following configuration may also be used. FIG. 4 is a cross-sectional view that shows a schematic diagram of another configuration example of the air-zinc battery cell provided in the air-zinc secondary battery system of the present invention.

[0051] In the air-zinc battery cell 10 shown in Fig. 4, a low-speed oxygen transport membrane 121 used when charging the air-zinc battery cell 10 is disposed on one side of the zinc gel negative electrode part 14 via a separator not shown. Also, a high-speed oxygen transport membrane 122 used when discharging the air-zinc battery cell 10 and having a higher oxygen transport capacity than the low-speed oxygen transport membrane 121 is disposed on the other side of the zinc gel negative electrode part 14 via a separator not shown. The high-speed oxygen transport membrane 122 is disposed on the side where the gas vent hole 112 of the case 11 is formed.

[0052] The high-speed oxygen transport membrane 122 has a higher oxygen transport rate than the low-speed oxygen transport membrane 121. In the charging reaction of the air-zinc battery cell 10, oxygen gas is generated from ZnO. This oxygen gas increases the internal pressure of the air-zinc battery cell 10, slowing down the reaction rate during charging. In the configuration of FIG. 4, a voltage is applied between the low-speed oxygen transport membrane 121 and the zinc gel negative electrode part 14 when the air-zinc battery cell 10 is charged. This suppresses the supply of oxygen through the low-speed oxygen transport membrane 121, and the action of the electrolyte transport part 20 allows the oxygen gas to be efficiently discharged to the outside of the air-zinc battery cell 10 together with the electrolyte. On the other hand, in the configuration of Fig. 4, a voltage is applied between the high-speed oxygen transport membrane 122 and the zinc gel negative electrode part 14 when discharging the air-zinc battery cell 10. This allows oxygen to be efficiently supplied through the high-speed oxygen transport membrane 122, increasing the reaction rate during discharging. As a result, an air-zinc secondary battery system 1 with a high output voltage can be obtained.

[0053] As described above, it is understood by those skilled in the art that the present invention can be embodied in other specific forms without changing the technical idea or essential features of the present invention. The scope of the present invention is defined by the claims set forth below rather than the above detailed description, and all modifications and variations derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. [Industrial Applicability]

[0054] According to the present invention, the electrolyte contained in the zinc gel negative electrode part and the electrolyte in the external electrolyte tank are circulated, thereby maintaining the concentration of the electrolyte in the air-zinc battery cell, more specifically, the concentration of potassium hydroxide in the electrolyte. In particular, in the present invention, the electrolyte outlet part for discharging the electrolyte in the zinc gel negative electrode part to the outside is disposed at a higher position than the electrolyte inlet part for discharging the electrolyte from the external electrolyte tank into the zinc gel negative electrode part. Therefore, by operating the electrolyte transport part, the electrolyte with a relatively high concentration of potassium hydroxide that has accumulated in the lower part of the zinc gel negative electrode part can be discharged from the electrolyte outlet part located at the upper part of the zinc gel negative electrode part. As a result, the electrolyte concentration of the entire zinc gel negative electrode part is maintained, and as a result, the precipitation of potassium hydroxide in the air positive electrode part can be suppressed, and the formation of zinc dendrite in the zinc gel negative electrode part can be suppressed. In addition, oxygen gas can be supplied to the air positive electrode part during discharging, and oxygen gas can be discharged to the outside of the air-zinc secondary battery during recharging. As a result, it is possible to provide an air-zinc secondary battery system that has high charging performance and maintains a high output voltage for a long period of time. Therefore, the present invention has industrial applicability.

Claims

1. An air-zinc battery array including a plurality of air-zinc battery cells connected together in a rectangular case, the air-zinc battery cells each having an air positive electrode portion, a separator, and a zinc gel negative electrode portion containing an electrolyte therein; an external electrolyte tank for storing an electrolyte; and an electrolyte transport unit configured to flow the electrolyte from the external electrolyte tank into the zinc gel negative electrode portion in each of the air-zinc battery cells, thereby circulating the electrolyte in the external electrolyte tank and the electrolyte in the zinc gel negative electrode portion; the external electrolyte tank and the case are provided with gas vents; The case includes an electrolyte inlet portion for allowing the electrolyte from the external electrolyte tank to flow into the zinc gel negative electrode portion, and an electrolyte outlet portion for allowing the electrolyte from the zinc gel negative electrode portion to flow out to the outside, The air-zinc secondary battery system is characterized in that the electrolyte outlet is disposed at a position higher than a position at which the electrolyte inlet is provided.

2. The air-zinc secondary battery system according to claim 1, wherein the electrolyte outlet of one of the air-zinc battery cells and the electrolyte inlet of the other of the air-zinc battery cells are connected to each other.

3. 2. The air-zinc secondary battery system of claim 1, wherein the separator is made of nonwoven fibers formed from a polymer solution using an electrospinning method.

4. As the polymer solution, a mixture of Nafion and a polyacrylic acid solution is used, The air-zinc secondary battery system according to claim 1, wherein the nonwoven fibers have a sulfur skeleton derived from a Nafion structure and a rigid structure derived from polyacrylic acid.

5. The air-zinc secondary battery system according to claim 1 , wherein the zinc gel negative electrode portion contains an elastic conductive material.

6. 2. The air-zinc secondary battery system according to claim 1, wherein the elastic conductive material is at least one of expanded graphite and graphene.

7. The air-zinc secondary battery system according to claim 1, wherein the air positive electrode part has a low-speed oxygen transport membrane that is used when charging the air-zinc battery cell, and a high-speed oxygen transport membrane that is used when discharging the air-zinc battery cell and has a higher oxygen transport capacity than the low-speed oxygen transport membrane.

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