Air battery

Abstract

This air battery comprises: an air electrode; a metal electrode; an electrolyte; a hollow fiber membrane having pores permeable to oxygen and being in contact with the air electrode; and a case that accommodates at least part of the air electrode, the metal electrode, the electrolyte, and the hollow fiber membrane. The hollow fiber membrane has a communication portion in which the inside and outside of the hollow fiber membrane are in communication with each other through the pores, and a non-communication portion in which the inside and outside of the hollow fiber membrane are not in communication with each other.

Description

Air battery

[0001] This disclosure relates to an air battery.

[0002] Conventionally, air batteries have been known that comprise a metal electrode (negative electrode) with a metal such as zinc as the active material, and an air electrode (positive electrode) with oxygen from the air as the active material. Patent Document 1 describes an air battery that uses a hollow fiber membrane as the water-repellent film of the air electrode. In the air battery described in Patent Document 1, by using a hollow fiber membrane as the water-repellent film of the air electrode, even if the electrolyte leaks, the electrolyte is retained within the hollow fiber membrane and does not leak to the outside.

[0003] Japanese Patent Application Publication No. 05-047388

[0004] In the air battery described in Patent Document 1, a hollow fiber membrane with uniformly distributed micropores having an average pore size of 10 μm is used as the water-repellent membrane. Therefore, even if the hollow fiber membrane is water-repellent, when gases such as oxygen, hydrogen, and carbon dioxide are generated during charging and the pressure inside the case increases, the electrolyte inside the case may leak out of the air battery by permeating through the micropores throughout the hollow fiber membrane. Furthermore, if the micropores are uniformly distributed in the hollow fiber membrane, an excess supply of oxygen may cause oxygen bubbles to form in the electrolyte, potentially further increasing the pressure inside the case.

[0005] Therefore, the object of this disclosure is to provide an air battery that can suppress the leakage of electrolyte.

[0006] [1] The air battery according to the present disclosure comprises an air electrode, a metal electrode, an electrolyte, a hollow fiber membrane having oxygen permeable pores and in contact with the air electrode, and a case housing at least a part of the air electrode, the metal electrode, the electrolyte, and the hollow fiber membrane, wherein the hollow fiber membrane has a communicating portion in which the inside and outside of the hollow fiber membrane are in communication through pores, and a non-communicating portion in which the inside and outside of the hollow fiber membrane are not in communication.

[0007] In this air battery, a hollow fiber membrane with oxygen-permeable pores is in contact with the air electrode, allowing oxygen from the air to be supplied to the air electrode. Furthermore, the hollow fiber membrane has not only a communicating section where the inside and outside of the membrane are connected by pores, but also a non-communicating section where the inside and outside of the membrane are not connected. Therefore, even if the pressure inside the case increases due to the gas generated during charging, leakage of the electrolyte is suppressed, at least from the non-communicating section of the hollow fiber membrane. In addition, because the hollow fiber membrane has a non-communicating section, the amount of oxygen supplied can be reduced compared to when the hollow fiber membrane does not have a non-communicating section, thus suppressing the generation of oxygen bubbles in the electrolyte. This suppresses the leakage of the electrolyte.

[0008] [2] In the air battery described in [1], the surface of the non-communicating portion may be covered with resin. In this air battery, since the surface of the non-communicating portion is covered with resin, the non-communicating portion can be easily formed. For example, an intermediate product in which the entire hollow fiber membrane is a communicating portion can be made, and then a hollow fiber membrane having a communicating portion and a non-communicating portion can be made by covering a part of the surface of the intermediate product with resin.

[0009] [3] In the air battery described in [1] or [2], the non-communicating portion may be impregnated with resin. In this air battery, since the non-communicating portion is impregnated with resin, the non-communicating portion can be easily formed. For example, an intermediate product in which the entire hollow fiber membrane is a communicating portion can be made, and then a hollow fiber membrane having a communicating portion and a non-communicating portion can be made by impregnating a part of the intermediate product with resin.

[0010] [4] In the air battery described in any of [1] to [3], the portion of the hollow fiber membrane in contact with the air electrode is a communicating portion, and at least a portion of the portion of the hollow fiber membrane not in contact with the air electrode may be a non-communicating portion. In this air battery, since the portion of the hollow fiber membrane in contact with the air electrode is a communicating portion and at least a portion of the portion of the hollow fiber membrane not in contact with the air electrode is a non-communicating portion, it is possible to maintain the supply of oxygen to the air electrode while suppressing the leakage of electrolyte.

[0011] [5] In the air battery described in any of [1] to [4], the hollow fiber membrane has a case covering portion that is covered by a case, and the case covering portion may be a non-communicating portion. In this air battery, since the case covering portion that is covered by the case of the hollow fiber membrane is a non-communicating portion, even if an electrolyte enters between the hollow fiber membrane and the case, it is possible to suppress the electrolyte from permeating through the hollow fiber membrane and leaking out.

[0012] [6] In the air battery described in any of [1] to [5], the hollow fiber membrane may be water-repellent. In this air battery, because the hollow fiber membrane is water-repellent, even if the pores of the hollow fiber membrane are large, it is possible to suppress the permeation of the electrolyte inside the case through the hollow fiber membrane.

[0013] [7] In the air battery described in any of [1] to [6], the contact angle between the hollow fiber membrane and water may be 90 degrees or more. In this air battery, since the contact angle between the hollow fiber membrane and water is 90 degrees or more, even if the pores of the hollow fiber membrane are large, it is possible to suppress the permeation of the electrolyte inside the case through the hollow fiber membrane.

[0014] [8] In the air battery described in any of [1] to [7], the hollow fiber membrane may penetrate the air electrode. In this air battery, since the hollow fiber membrane penetrates the air electrode, oxygen from the air can be efficiently supplied to the air electrode.

[0015] [9] In the air battery described in any of [1] to [8], the hollow portion of the hollow fiber membrane may be open to the outside of the case from both ends of the hollow fiber membrane. In this air battery, air can be circulated from the opening on one side of the hollow fiber membrane to the opening on the other side. This allows, for example, air to be forcibly circulated in the hollow portion of the hollow fiber membrane by supplying air to the opening on one side of the hollow fiber membrane. Alternatively, for example, the air in the hollow portion of the hollow fiber membrane can be heated by the heat generated by the air battery, allowing air to circulate naturally in the hollow portion of the hollow fiber membrane. This allows for temperature control of the air battery.

[0016] According to this disclosure, it is possible to suppress the leakage of electrolytes.

[0017] This is a schematic diagram of an air battery according to the embodiment. This is a schematic cross-sectional view of a hollow fiber membrane. This is a schematic diagram showing an example of the arrangement of multiple hollow fiber membranes. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of another example of an air battery according to the embodiment. This is a schematic diagram of a modified air battery. This is a schematic diagram of a modified air battery.

[0018] The air battery of this embodiment will be described in detail below with reference to the drawings. In all the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0019] Figure 1 is a schematic diagram of an air battery according to an embodiment. As shown in Figure 1, the air battery 1 comprises an air electrode 2, a metal electrode 3, a separator 4, an electrolyte 5, a hollow fiber membrane 6, a case 7, a positive electrode terminal (not shown), and a negative electrode terminal (not shown).

[0020] The air electrode 2 is housed in case 7 and is an electrode that primarily causes a reduction reaction of oxygen in the air within case 7. In other words, the air electrode 2 is an electrode in which the oxygen reduction reaction mainly proceeds when oxygen from the air is supplied. When the air battery 1 is used as a secondary battery, the oxygen reduction reaction proceeds in the air electrode 2 during discharge and the oxygen evolution reaction proceeds during charging. The air electrode 2 is electrically connected to the positive electrode terminal by lead wires or the like. The air electrode 2 is composed of a conductive material such as activated carbon, graphite, carbon black, or Ketjenblack, to which additives such as catalysts that promote oxidation-reduction reactions are added. Examples of catalysts that can be used include precious metals or compounds thereof such as platinum, ruthenium, and iridium; transition metals or compounds thereof such as manganese, iron, and cobalt; organometallic complexes; perovskite-type oxides; and carbon materials.

[0021] The metal electrode 3 is housed in the case 7 and is an electrode that primarily causes metal oxidation reactions within the case 7. In other words, the metal electrode 3 is an electrode where metal oxidation reactions mainly proceed. When the air battery 1 is used as a secondary battery, metal oxidation (dissolution) reactions proceed in the metal electrode 3 during discharge, and metal reduction (deposition) reactions proceed during charging. The metal electrode 3 is electrically connected to the negative electrode terminal by lead wires or the like. As the metal material that forms the metal electrode 3, for example, metal species such as zinc, lithium, aluminum, iron, calcium, sodium, manganese, magnesium, nickel, lead, tin, and cadmium, or their oxides, can be used.

[0022] The separator 4 prevents direct contact between the air electrode 2 and the metal electrode 3. The separator 4 is formed, for example, as a film or plate. As the material for forming the separator 4, a porous membrane or resin nonwoven fabric made of resin materials such as cellulose, polyethylene, polyolefins such as polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, etc., is used.

[0023] The electrolyte 5 is housed in case 7 and is the substance that moves ions between the air electrode 2 and the metal electrode 3. As the electrolyte 5, for example, aqueous solutions of sodium chloride, potassium chloride, sodium hydroxide, potassium hydroxide, etc., or non-aqueous solutions can be used.

[0024] Figure 2 is a schematic cross-sectional view of the hollow fiber membrane. As shown in Figures 1 and 2, the hollow fiber membrane 6 is a hollow fiber membrane that allows gases such as oxygen to pass through but does not allow liquids such as electrolytes 5 to pass through. The hollow fiber membrane 6 has pores 68 through which oxygen can pass. The hollow fiber membrane 6 may be a water-repellent membrane or a hydrophilic membrane. If the hollow fiber membrane 6 is a water-repellent membrane, the contact angle between the hollow fiber membrane 6 and water may be, for example, 90 degrees or more, preferably 95 degrees or more, and more preferably 100 degrees or more.

[0025] The hollow fiber membrane 6 has a communicating portion 6A in which the inside and outside of the hollow fiber membrane 6 communicate with each other through holes 68, and a non-communicating portion 6B in which the inside and outside of the hollow fiber membrane 6 do not communicate with each other. In the communicating portion 6A, for example, a large number of holes 68 communicate with each other, so that the inside and outside of the hollow fiber membrane 6 communicate with each other. In the non-communicating portion 6B, for example, a large number of holes 68 do not communicate with each other, or a large number of holes 68 do not communicate with each other to such an extent that the inside and outside of the hollow fiber membrane 6 communicate with each other, so that the inside and outside of the hollow fiber membrane 6 do not communicate with each other.

[0026] Each of the communicating portion 6A and the non-communicating portion 6B has a predetermined length in the extending direction of the hollow fiber membrane 6. The communicating portion 6A and the non-communicating portion 6B are adjacent to each other in the extending direction of the hollow fiber membrane 6. Each of the communicating portion 6A and the non-communicating portion 6B may be provided only one or a plurality in one hollow fiber membrane 6. Also, the number of each of the communicating portion 6A and the non-communicating portion 6B in one hollow fiber membrane 6 may be the same or different.

[0027] Examples of the membrane shape (shape of the side wall) of the communicating portion 6A include a porous membrane and a microporous membrane. The porous membrane is a membrane having a large number of holes 68 through which liquid can permeate. The microporous membrane is a membrane having a large number of holes 68 through which liquid cannot permeate. In the communicating portion 6A, for example, a large number of holes 68 of the porous membrane communicate with each other, or a large number of holes 68 of the microporous membrane communicate with each other, so that the inside and outside of the hollow fiber membrane 6 communicate with each other.

[0028] Examples of the film shape (side wall shape) of the non-connecting portion 6B include a porous film, a microporous film, and a homogeneous film without porosity (non-porous film). Examples of the film form of the non-connecting portion 6B include a symmetric film (homogeneous film) in which the chemical or physical structure of the entire film is homogeneous, and an asymmetric film (heterogeneous film) in which the chemical or physical structure of the film varies depending on the part of the film. When the non-connecting portion 6B is a symmetric film (homogeneous film), the non-connecting portion 6B may be, for example, a non-porous film. By having no pores, it can be ensured that the inside and outside of the hollow fiber membrane 6 are not connected. When the non-connecting portion 6B is an asymmetric film (heterogeneous film), the non-connecting portion 6B may be a porous film or a microporous film whose surface is covered with a resin, or a porous film or a microporous film impregnated with a resin. By covering the surface of the porous film or the microporous film with a resin, or by impregnating the porous film or the microporous film with a resin, it can be ensured that the inside and outside of the hollow fiber membrane 6 are not connected. When the surface of the porous film or the microporous film is covered with a resin, the resin may cover either the inner surface or the outer surface of the porous film or the microporous film. The inner surface of the porous film or the microporous film is the surface on the side of the hollow portion 61 of the hollow fiber membrane 6, and the outer surface of the porous film or the microporous film is the surface on the side opposite to the hollow portion 61 of the hollow fiber membrane 6.

[0029] The oxygen permeability in the connecting portion 6A is higher than the oxygen permeability in the non-connecting portion 6B. The oxygen permeability in the connecting portion 6A is, for example, 0.1×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 5000×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less, preferably 1.0×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 2000×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less, more preferably 5×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 1000×10-５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less. The oxygen permeability in the non-communication part 6B is, for example, 0 [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 50×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less, preferably 1.0×10 -２０ [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 20×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less, more preferably 1.0×10 -１６ [cm ３ (STP) / cm ２ ·sec·cmHg] or more and 5×10 -５ [cm ３ (STP) / cm ２ ·sec·cmHg] or less. The oxygen permeability is measured by a method conforming to ASTM-D1434.

[0030] The ratio of the holes 68 on the membrane surface in the communication part 6A is larger than the ratio of the holes 68 on the membrane surface in the non-communication part 6B. The ratio of the holes 68 on the membrane surface in the communication part 6A is, for example, 0.1% or more and 50% or less, preferably 0.5% or more and 40% or less, more preferably 1% or more and 30% or less. The ratio of the holes 68 on the membrane surface in the non-communication part 6B is, for example, 0% or more and 10% or less, preferably 0% or more and 5% or less, more preferably 0% or more and 1% or less. The ratio of the holes 68 on the membrane surface is measured by image analysis using ImageJ with an image of 50,000 times or more obtained by SEM, for example, JSM-7800F (manufactured by JEOL Ltd.).

[0031] At least a portion of the hollow fiber membrane 6 is housed in the case 7 and positioned within the case 7 to be in contact with the air electrode 2. The portion of the hollow fiber membrane 6 that is in contact with the air electrode 2 is a communication portion 6A, and at least a portion of the portion of the hollow fiber membrane 6 that is not in contact with the air electrode 2 is a non-communication portion 6B. Therefore, air supplied to the hollow portion 61 of the hollow fiber membrane 6 permeates through the communication portion 6A, supplying oxygen to the air electrode 2. At this time, some of the air that has permeated through the hollow fiber membrane 6 in the communication portion 6A may remain in the case 7 without being used in the reduction reaction of the air electrode 2. Also, when the air battery 1 is used as a secondary battery, the oxygen generation reaction proceeds at the air electrode 2 during charging, generating gases such as oxygen. In these cases, gases such as oxygen will be present in the case 7, but these gases will permeate through the hollow fiber membrane 6 and be discharged to the outside of the case 7 via the hollow portion 61. This allows for the leakage of electrolyte 5 to be suppressed while gases such as oxygen present inside case 7 can be discharged to the outside of case 7.

[0032] The hollow fiber membrane 6 may be a single fiber or multiple fibers. The hollow fiber membrane 6 may be arranged so as to be in contact with the outer surface of the air electrode 2, or it may be arranged so as to penetrate the air electrode 2. If there are multiple hollow fiber membranes 6, the multiple hollow fiber membranes 6 may be arranged in a straight line as shown in Figure 3, or they may be bundled together. Figure 3 is a schematic diagram showing an example of the arrangement of multiple hollow fiber membranes. In this embodiment, as an example, it will be described that multiple hollow fiber membranes 6 arranged in a straight line are arranged so as to penetrate the air electrode 2.

[0033] Examples of materials for the hollow fiber membrane 6 include polyolefin resins such as polypropylene, polyethylene, and polymethylpentene; silicon resins such as polydimethylsiloxane and its copolymers; and fluorine resins such as PTFE and vinylidene fluoride.

[0034] Case 7 houses the air electrode 2, the metal electrode 3, the separator 4, the electrolyte 5, and at least a portion of the hollow fiber membrane 6. Case 7 may be a single unit or may be composed of multiple components combined together. If case 7 is a single unit, it may have holes formed in it for passing the hollow fiber membrane 6 through. If case 7 is composed of multiple components combined together, it may be divided into, for example, a container section (not shown) with an opening formed at the top and a lid section (not shown) that closes the opening of the container section, and the hollow fiber membrane 6 may be sandwiched between the container section and the lid section.

[0035] The hollow portion 61 of the hollow fiber membrane 6 may or may not be open to the outside of the case 7. When the hollow portion 61 of the hollow fiber membrane 6 is said to be open to the outside of the case 7, it means that the hollow portion 61 of the hollow fiber membrane 6 is in communication with the space outside the case 7. On the other hand, when the hollow portion 61 of the hollow fiber membrane 6 is said not to be open to the outside of the case 7, it means that the hollow portion 61 of the hollow fiber membrane 6 is not in communication with the space outside the case 7.

[0036] If the hollow portion 61 is open to the outside of the case 7, the hollow portion 61 may be open to the outside of the case 7 from both ends of the hollow fiber membrane 6, or it may be open to the outside of the case 7 from one end of the hollow fiber membrane 6.

[0037] When the hollow portion 61 is open to the outside of the case 7 from both ends of the hollow fiber membrane 6, the hollow fiber membrane 6 has, for example, an opening 62 at one end of the hollow fiber membrane 6 through which the hollow portion 61 opens, and an opening 63 at the other end of the hollow fiber membrane 6 through which the hollow portion 61 opens. Both openings 62 and 63 are open to the outside of the case 7.

[0038] On the other hand, if the hollow portion 61 is open to the outside of the case 7 from one end of the hollow fiber membrane 6, the hollow fiber membrane 6 has, for example, an opening 62 at one end of the hollow fiber membrane 6 through which the hollow portion 61 opens, and the hollow portion 61 is sealed at the other end of the hollow fiber membrane 6. The opening 62 is open to the outside of the case 7. In this case, the other end of the hollow fiber membrane 6 may or may not protrude from the surface of the case 7. If the other end of the hollow fiber membrane 6 protrudes from the surface of the case 7, the portion of the hollow fiber membrane 6 protruding from the surface of the case 7 may be a communication portion 6A. Since the portion of the hollow fiber membrane 6 protruding from the surface of the case 7 is a communication portion 6A, oxygen can be supplied to the hollow portion 61 through the hole 68. In addition, the other end of the hollow fiber membrane 6 may be sealed with a sealing material made of an oxygen-permeable material. This allows oxygen to be supplied to the hollow portion 61 via the sealing material. The material of this sealing material may be the same as the material that constitutes the hollow fiber membrane 6, or it may be different from that material.

[0039] If the hollow portion 61 is not open to the outside of the case 7, the hollow fiber membrane 6 is sealed at both ends, for example. In this case, the ends of the hollow fiber membrane 6 may or may not protrude from the surface of the case 7. If the ends of the hollow fiber membrane 6 protrude from the surface of the case 7, the portion of the hollow fiber membrane 6 protruding from the surface of the case 7 may be a communication portion 6A. The portion of the hollow fiber membrane 6 protruding from the surface of the case 7 being a communication portion 6A allows oxygen to be supplied to the hollow portion 61 through the holes 68. Furthermore, both ends of the hollow fiber membrane 6 may be sealed with a sealing material made of an oxygen-permeable material. This allows oxygen to be supplied to the hollow portion 61 through the sealing material. The material of this sealing material may or may not be the same as the material constituting the hollow fiber membrane 6.

[0040] The configuration in which the hollow portion 61 is open to the outside of the case 7 from both ends of the hollow fiber membrane 6 is not particularly limited.

[0041] For example, as shown in Figure 1, both ends of the hollow fiber membrane 6 may protrude from the surface of the case 7. In the air battery 1 shown in Figure 1, the hollow fiber membrane 6 has an opening 62 at one end of the hollow fiber membrane 6 where the hollow portion 61 opens, and an opening 63 at the other end of the hollow fiber membrane 6 where the hollow portion 61 opens. The vicinity 66 of one end 64 of the hollow fiber membrane 6 is covered by the case 7, so that one end 64 of the hollow fiber membrane 6 protrudes from the surface of the case 7. As a result, the opening 62 of the hollow portion 61 is open to the outside of the case 7. Also, the vicinity 67 of the other end 65 of the hollow fiber membrane 6 is covered by the case 7, so that the other end 65 of the hollow fiber membrane 6 protrudes from the surface of the case 7. As a result, the opening 63 of the hollow portion 61 is open to the outside of the case 7.

[0042] Furthermore, as shown in Figures 4 and 5, the ends of the hollow fiber membrane 6 do not need to protrude from the surface of the case 7. Figures 4 and 5 are schematic diagrams of other examples of the air battery according to the embodiment.

[0043] In the air battery 1 shown in Figure 4, the hollow fiber membrane 6 has an opening 62 at one end of the hollow fiber membrane 6 where the hollow portion 61 opens, and an opening 63 at the other end of the hollow fiber membrane 6 where the hollow portion 61 opens. The ends of the hollow fiber membrane 6 do not protrude from the surface of the case 7. However, one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the opening 62 of the hollow portion 61 is positioned flush with the surface of the case 7. As a result, the opening 62 of the hollow fiber membrane 6 is open to the outside of the case 7. Also, the other end 65 of the hollow fiber membrane 6 is covered by the case 7, and the opening 63 of the hollow portion 61 is positioned flush with the surface of the case 7. As a result, the opening 63 of the hollow portion 61 is open to the outside of the case 7.

[0044] In the air battery 1 shown in Figure 5, the hollow fiber membrane 6 has an opening 62 at one end of the hollow fiber membrane 6 through which the hollow portion 61 opens, and an opening 63 at the other end of the hollow fiber membrane 6 through which the hollow portion 61 opens. The ends of the hollow fiber membrane 6 do not protrude from the surface of the case 7. However, one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the case 7 has a first communication passage 73 that connects the opening 62 of the hollow portion 61 to the outside of the case 7. As a result, the opening 62 of the hollow portion 61 is open to the outside of the case 7 through the first communication passage 73. Also, the other end 65 of the hollow fiber membrane 6 is covered by the case 7, and the case 7 has a second communication passage 74 that connects the opening 63 of the hollow portion 61 to the outside of the case 7. As a result, the opening 63 of the hollow portion 61 is open to the outside of the case 7 through the second communication passage 74.

[0045] The configuration in which the hollow portion 61 is opened to the outside of the case 7 from one end of the hollow fiber membrane 6 is not particularly limited.

[0046] For example, in the air battery 1 shown in Figures 1, 4, and 5, the opening 62 or opening 63 of the hollow fiber membrane 6 may be sealed. Also, in the air battery 1 shown in Figure 5, the first communication passage 73 or the second communication passage 74 of the case 7 may be sealed. Furthermore, as shown in Figure 6, if one end of the hollow fiber membrane 6 is sealed, the sealed end of the hollow fiber membrane 6 may be located inside the case 7. Figure 6 is a schematic diagram of another example of the air battery according to the embodiment.

[0047] In the air battery 1 shown in Figure 6, the hollow fiber membrane 6 has an opening 62 at one end of the hollow fiber membrane 6 where the hollow portion 61 opens. The vicinity 66 of one end 64 of the hollow fiber membrane 6 is covered by the case 7, and one end 64 of the hollow fiber membrane 6 protrudes from the surface of the case 7. As a result, the opening 62 of the hollow portion 61 is open to the outside of the case 7. On the other hand, the hollow portion 61 at the other end 65 of the hollow fiber membrane 6 is sealed by a sealing material 69. The other end 65 of the hollow fiber membrane 6 is located inside the case 7. In other words, the other end 65 of the hollow fiber membrane 6 is completely housed inside the case 7.

[0048] The configuration in which the hollow portion 61 is not open to the outside of the case 7 is not particularly limited.

[0049] For example, as shown in Figures 7 to 10, both ends of the hollow fiber membrane 6 may be sealed with a sealing material 69. Figures 7 to 10 are schematic diagrams of other examples of air batteries according to the embodiment.

[0050] In the air battery 1 shown in Figures 7 to 10, the hollow fiber membrane 6 has a hollow portion 61 sealed with a sealing material 69 at one end 64 of the hollow fiber membrane 6, and the hollow portion 61 at the other end 65 of the hollow fiber membrane 6 is also sealed with a sealing material 69.

[0051] In the air battery 1 shown in Figure 7, the vicinity 66 of one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the one end 64 of the hollow fiber membrane 6 protrudes from the surface of the case 7. Also, the vicinity 67 of the other end 65 of the hollow fiber membrane 6 is covered by the case 7, and the other end 65 of the hollow fiber membrane 6 protrudes from the surface of the case 7. Here, the ends 64 and 65 of the hollow fiber membrane 6 protruding from the surface of the case 7 may be connecting portions 6A. Since the ends 64 and 65 of the hollow fiber membrane 6 protruding from the surface of the case 7 are connecting portions 6A, oxygen can be supplied to the hollow portion 61 through the holes 68. The sealing material 69 may also be made of an oxygen-permeable material. Since the sealing material 69 is made of an oxygen-permeable material, oxygen can be supplied to the hollow portion 61 through the sealing material 69. The material of this sealing material 69 may be, for example, the same as the material that makes up the hollow fiber membrane 6, in particular the material that makes up the connecting portion 6A.

[0052] Furthermore, in the air battery 1 shown in Figure 8, one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the tip of this end 64 is positioned flush with the surface of the case 7. The other end 65 of the hollow fiber membrane 6 is also covered by the case 7, and the tip of this end 65 is positioned flush with the surface of the case 7. Here, the sealing material 69 may be made of an oxygen-permeable material, similar to the sealing material 69 of the air battery 1 shown in Figure 7. By making the sealing material 69 an oxygen-permeable material, oxygen can be supplied to the hollow portion 61 through the sealing material 69.

[0053] Furthermore, in the air battery 1 shown in Figure 9, one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the tip of this end 64 is positioned recessed from the surface of the case 7. The other end 65 of the hollow fiber membrane 6 is also covered by the case 7, and the tip of this end 65 is positioned recessed from the surface of the case 7. Here, the sealing material 69 may be made of an oxygen-permeable material, similar to the sealing material 69 of the air battery 1 shown in Figure 7. By making the sealing material 69 an oxygen-permeable material, oxygen can be supplied to the hollow portion 61 through the sealing material 69.

[0054] Furthermore, in the air battery 1 shown in Figure 10, the vicinity 66 of one end 64 of the hollow fiber membrane 6 is covered by the case 7, and the tip of this end 64 protrudes from the surface of the case 7. On the other hand, the other end 65 of the hollow fiber membrane 6 is located inside the case 7. In other words, the other end 65 of the hollow fiber membrane 6 is completely housed inside the case 7. Here, the sealing material 69, particularly the sealing material 69 that seals the hollow portion 61 at the end 64, may be made of an oxygen-permeable material, similar to the sealing material 69 of the air battery 1 shown in Figure 7. By making the sealing material 69 an oxygen-permeable material, oxygen can be supplied to the hollow portion 61 via the sealing material 69.

[0055] The hollow fiber membrane 6 may be formed in any shape within the case 7. For example, the hollow fiber membrane 6 may extend in a straight line, be curved, bent, or wound within the case 7. If the hollow fiber membrane 6 is curved within the case 7, it may be curved in a U-shape or an L-shape. If the hollow fiber membrane 6 is bent within the case 7, it may be bent in an L-shape or a V-shape. If the hollow fiber membrane 6 is wound within the case 7, it may be wound circumferentially or spirally. If the hollow fiber membrane 6 is curved, bent, or wound within the case 7, the openings 62 and 63 of the hollow portion 61 may be formed on the same wall surface of the case 7 or on different wall surfaces of the case 7.

[0056] If the portion of the hollow fiber membrane 6 covered by the case 7 is considered the case covering portion, then the case covering portion is a non-communicating portion 6B. In the air battery 1 shown in Figures 1 and 7, the vicinity 66 of the end 64 and the vicinity 67 of the end 65 of the hollow fiber membrane 6 become the case covering portion. In the air battery 1 shown in Figures 4, 5, 8, and 9, the end 64 and the end 65 of the hollow fiber membrane 6 become the case covering portion. In the air battery 1 shown in Figures 6 and 10, the vicinity 66 of the end 64 of the hollow fiber membrane 6 becomes the case covering portion.

[0057] The portion of the hollow fiber membrane 6 between the part of the hollow fiber membrane 6 that contacts the air electrode 2 and the case covering portion may be either a communicating portion 6A or a non-communicating portion 6B, but it is preferable that it be a non-communicating portion 6B. Alternatively, the portion of the hollow fiber membrane 6 between the part of the hollow fiber membrane 6 that contacts the air electrode 2 and the case covering portion may be partly a communicating portion 6A and the remainder non-communicating portion 6B. In this case, the portion of the hollow fiber membrane 6 between the part of the hollow fiber membrane 6 that contacts the air electrode 2 and the case covering portion may be a communicating portion 6A, and the portion adjacent to the case covering portion may be a non-communicating portion 6B.

[0058] As described above, in the air battery 1 according to this embodiment, the hollow fiber membrane 6 having oxygen-permeable pores 68 is in contact with the air electrode 2, so that oxygen from the air can be supplied to the air electrode 2. Furthermore, the hollow fiber membrane 6 has not only a communicating portion 6A where the inside and outside of the hollow fiber membrane 6 are connected by the pores 68, but also a non-communicating portion 6B where the inside and outside of the hollow fiber membrane 6 are not connected. Therefore, even if the pressure inside the case 7 increases due to the gas generated during charging, leakage of the electrolyte 5 is suppressed, at least from the non-communicating portion 6B of the hollow fiber membrane 6. In addition, because the hollow fiber membrane 6 has a non-communicating portion 6B, the amount of oxygen supplied can be reduced compared to when the hollow fiber membrane 6 does not have a non-communicating portion 6B, so that the generation of oxygen bubbles in the electrolyte 5 can be suppressed. This prevents the electrolyte 5 from leaking out.

[0059] Furthermore, in this air battery 1, if the surface of the non-communicating portion 6B is covered with resin, the non-communicating portion 6B can be easily formed. For example, an intermediate product can be made in which the entire hollow fiber membrane is a communicating portion 6A, and then a hollow fiber membrane 6 having a communicating portion 6A and a non-communicating portion 6B can be made by covering a part of the surface of the intermediate product with resin.

[0060] Furthermore, in this air battery, if the non-communicating portion 6B is impregnated with resin, the non-communicating portion 6B can be easily formed. For example, by creating an intermediate product in which the entire hollow fiber membrane is a communicating portion 6A, and then impregnating a part of the intermediate product with resin, a hollow fiber membrane 6 having a communicating portion 6A and a non-communicating portion 6B can be produced.

[0061] Furthermore, in this air battery 1, the portion of the hollow fiber membrane 6 that is in contact with the air electrode 2 is a communication portion 6A, and at least a part of the portion of the hollow fiber membrane 6 that is not in contact with the air electrode 2 is a non-communication portion 6B. Therefore, it is possible to maintain the amount of oxygen supplied to the air electrode 2 while suppressing leakage of the electrolyte 5.

[0062] Furthermore, in this air battery 1, since the case covering portion that is covered by the case 7 of the hollow fiber membrane 6 is a non-communicating portion 6B, even if the electrolyte 5 enters between the hollow fiber membrane 6 and the case 7, it is possible to suppress the leakage of this electrolyte 5 through the hollow fiber membrane 6.

[0063] Furthermore, in this air battery 1, since the hollow fiber membrane 6 is water-repellent, even if the pores 68 of the hollow fiber membrane 6 are large, it is possible to suppress the permeation of the electrolyte 5 inside the case 7 through the hollow fiber membrane 6.

[0064] Furthermore, in this air battery 1, the contact angle between the hollow fiber membrane 6 and water is 90 degrees or more, preferably 95 degrees or more, and more preferably 100 degrees or more. Therefore, even if the pores 68 of the hollow fiber membrane 6 are large, it is possible to suppress the permeation of the electrolyte 5 in the case 7 through the hollow fiber membrane 6.

[0065] Furthermore, in this air battery 1, since the hollow fiber membrane 6 penetrates the air electrode 2, oxygen from the air can be efficiently supplied to the air electrode 2.

[0066] Furthermore, in this air battery, air can be circulated from one opening 62 to the other opening 63 of the hollow fiber membrane 6. This allows, for example, air to be forcibly circulated in the hollow portion 61 of the hollow fiber membrane 6 by supplying air to the opening 62 on one side of the hollow fiber membrane 6. Alternatively, for example, the air in the hollow portion 61 of the hollow fiber membrane 6 can be heated by the heat generated by the air battery 1, allowing air to circulate naturally in the hollow portion 61 of the hollow fiber membrane 6. This enables temperature control of the air battery 1.

[0067] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above.

[0068] For example, although the above embodiment was described as including a separator, a separator may be omitted as long as the air electrode and the metal electrode do not come into contact.

[0069] Furthermore, for example, if the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends of the hollow fiber membrane, the air battery may be equipped with an air supply device that supplies air to the opening on one side of the hollow fiber membrane.

[0070] Figure 11 is a schematic diagram of a modified air battery. The modified air battery 1A shown in Figure 11 is basically the same as the air battery 1 shown in Figure 1, but differs from the air battery 1 shown in Figure 1 in that it is equipped with an air supply device 8 that supplies air to the opening 63 of the hollow fiber membrane 6. The air supply device 8 may be directly connected to the hollow fiber membrane 6, or it may be indirectly connected to the hollow fiber membrane 6 via a pipe (not shown). The air supply device 8 may also supply hot air or cold air to the opening 63 of the hollow fiber membrane 6. For example, a pump that blows out air can be used as the air supply device 8.

[0071] Furthermore, for example, if the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends of the hollow fiber membrane, the air battery may be composed of multiple air battery cells, with the hollow fiber membranes of each air battery cell communicating with one another.

[0072] Figure 12 is a schematic diagram of a modified air battery. The modified air battery 1B shown in Figure 12 comprises a plurality of air battery cells 11. Each of the plurality of air battery cells 11 has the same configuration as the air battery 1 shown in Figure 4. That is, each of the plurality of air battery cells 11 has the same air electrode 2, metal electrode 3, separator 4, electrolyte 5, hollow fiber membrane 6, and case 7 as the air battery 1 shown in Figure 4. The hollow fiber membranes 6 of the plurality of air battery cells 11 are in communication with each other. In this case, the hollow fiber membranes 6 of the plurality of air battery cells 11 may be made of one identical hollow fiber membrane, or different hollow fiber membranes 6 may be used for each air battery cell 11. When different hollow fiber membranes 6 are used for each air battery cell 11, the hollow fiber membranes 6 of each air battery cell 11 may be directly connected, or they may be indirectly connected via pipes.

[0073] 1...Air battery, 1A...Air battery, 1B...Air battery, 2...Air electrode, 3...Metal electrode, 4...Separator, 5...Electrolyte, 6...Hollow fiber membrane, 6A...Communicating section, 6B...Non-communicating section, 7...Case, 8...Air supply device, 11...Air battery cell, 61...Hollow section, 62...Opening, 63...Opening, 64...End (Case covering section), 65...End (Case covering section), 66...Near the end (Case covering section), 67...Near the end (Case covering section), 68...Hole, 69...Sealing material, 73...First communication passage, 74...Second communication passage.

Claims

1. An air battery comprising: an air electrode; a metal electrode; an electrolyte; a hollow fiber membrane having oxygen-permeable pores and in contact with the air electrode; and a case housing at least a portion of the air electrode, the metal electrode, the electrolyte, and the hollow fiber membrane, wherein the hollow fiber membrane has a communicating portion where the inside and outside of the hollow fiber membrane are in communication through the pores, and a non-communicating portion where the inside and outside of the hollow fiber membrane are not in communication.

2. The air battery according to claim 1, wherein the surface of the non-communicating portion is covered with resin.

3. The non-communicating portion is impregnated with resin, as described in claim 1.

4. The portion of the hollow fiber membrane in contact with the air electrode is the communication portion, and at least a portion of the portion of the hollow fiber membrane not in contact with the air electrode is the non-communication portion, as described in claim 1.

5. The air battery according to claim 1, wherein the hollow fiber membrane has a case covering portion that is covered by the case, and the case covering portion is the non-communicating portion.

6. The air battery according to claim 1, wherein the hollow fiber membrane is water-repellent.

7. The air battery according to claim 1, wherein the contact angle between the hollow fiber membrane and water is 90 degrees or more.

8. The air battery according to claim 1, wherein the hollow fiber membrane penetrates the air electrode.

9. The air battery according to claim 1, wherein the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends of the hollow fiber membrane.

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