Air cell

Abstract

An air cell according to the present invention comprises an air electrode, a metal electrode, an electrolyte, a hollow fiber membrane in contact with the air electrode, and a case that houses the air electrode, the metal electrode, the electrolyte, and at least a portion of the hollow fiber membrane. A hollow part of the hollow fiber membrane is open to outside of the case from both ends of the hollow fiber membrane.

Description

Air battery

[0001] This disclosure relates to an air battery.

[0002] Conventionally, an air battery including a metal electrode (negative electrode) using a metal such as zinc as an active material and an air electrode (positive electrode) using oxygen in the air as an active material has been known. Patent Document 1 describes an air battery using a hollow fiber membrane for the water-repellent film of the air electrode. In the air battery described in Patent Document 1, by using a hollow fiber membrane for the water-repellent film of the air electrode, even if the electrolyte leaks, the electrolyte is retained inside the hollow fiber membrane and prevented from leaking to the outside.

[0003] Japanese Patent Application Laid-Open No. 05-047388

[0004] An air battery may become hot due to heat generation or the like by electrochemical reactions at the metal electrode and the air electrode. In particular, when the air battery is enlarged, the heat generation of the air battery becomes even greater. When the air battery becomes hot, the battery performance and the lifespan decrease. On the other hand, when the air battery becomes cold, such as when the air battery is exposed to a low-temperature environment, the rate of the electrochemical reaction decreases and the battery performance also decreases.

[0005] However, since conventional air batteries do not have a structure for temperature management, it is not easy to perform temperature management. In addition, since the air battery described in Patent Document 1 uses a hollow fiber membrane as the water-repellent film of the air electrode, it is possible to introduce external air into the air battery. However, since one side of the hollow fiber membrane is sealed with a lower gasket, it is not easy to circulate air inside the hollow fiber membrane.

[0006] Therefore, an object of this disclosure is to provide an air battery capable of easily performing temperature management of the air battery.

[0007] [1] The air battery according to this disclosure includes an air electrode, a metal electrode, an electrolyte, a hollow fiber membrane in contact with the air electrode, and a case that houses at least a part of the air electrode, the metal electrode, the electrolyte, and the hollow fiber membrane, and the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends of the hollow fiber membrane.

[0008] In this air battery, a hollow fiber membrane connected to the outside of the case is in contact with the air electrode, allowing oxygen from the air to be supplied to the air electrode. Furthermore, since the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends, air can circulate from one opening to the other. This means that, for example, by supplying air to one opening of the hollow fiber membrane, air can be forced to circulate within the hollow portion of the membrane. Alternatively, for example, the heat generated by the air battery can warm the air within the hollow portion of the membrane, allowing air to circulate naturally. This makes temperature control of the air battery easy.

[0009] [2] In the air battery described in [1], both ends of the hollow fiber membrane may protrude from the surface of the case. In this air battery, since both ends of the hollow fiber membrane protrude from the surface of the case, air can be circulated from the opening on one side of the hollow fiber membrane to the opening on the other side.

[0010] [3] In the air battery described in [1], both ends of the hollow fiber membrane do not protrude from the surface of the case, and the case may have a first communication passage that connects one opening of the hollow portion of the hollow fiber membrane to the outside of the case, and a second communication passage that connects the other opening of the hollow portion of the hollow fiber membrane to the outside of the case. In this air battery, although both ends of the hollow fiber membrane do not protrude from the surface of the case, the case has a first communication passage that connects one opening of the hollow portion of the hollow fiber membrane to the outside of the case, and a second communication passage that connects the other opening of the hollow portion of the hollow fiber membrane to the outside of the case, so that air can be circulated from one opening to the other of the hollow fiber membrane.

[0011] [4] In the air battery described in any of [1] to [3], 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, and the temperature of the air electrode can be easily controlled.

[0012] [5] An air battery according to any of [1] to [4] may further be provided with an air supply device that supplies air to an opening on one side of the hollow fiber membrane. In this air battery, because an air supply device that supplies air to an opening on one side of the hollow fiber membrane is provided, air can be forcibly circulated in the hollow portion of the hollow fiber membrane. This makes temperature control of the air battery even easier.

[0013] [6] An air battery according to any of [1] to [5], comprising a plurality of air battery cells each having an air electrode, a metal electrode, an electrolyte, a hollow fiber membrane, and a case, wherein the hollow fiber membranes of the plurality of air battery cells may be in communication with each other. In this air battery, since the hollow fiber membranes of the plurality of air battery cells are in communication with each other, the temperature of the plurality of air battery cells can be controlled efficiently and easily.

[0014] According to this disclosure, temperature control of air batteries can be easily performed.

[0015] This is a schematic diagram of an air battery according to the embodiment. 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 a modified air battery. This is a schematic diagram of a modified air battery.

[0016] 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.

[0017] 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).

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The hollow fiber membrane 6 is a hollow fiber membrane that allows gases such as oxygen to permeate but does not allow liquids such as electrolytes 5 to permeate. The material, membrane shape, and membrane form of the hollow fiber membrane 6 are not particularly limited. 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. Examples of membrane shapes (sidewall shapes) of the hollow fiber membrane 6 include porous membranes, microporous membranes, and homogeneous membranes (non-porous membranes) that do not have porosity. Examples of membrane forms of the hollow fiber membrane 6 include symmetrical membranes (homogeneous membranes) in which the chemical or physical structure of the entire membrane is homogeneous, and asymmetrical membranes (heterogeneous membranes) in which the chemical or physical structure of the membrane differs depending on the part of the membrane. An asymmetrical membrane (heterogeneous membrane) is a membrane having a non-porous dense layer and a porous layer. Non-porous means that it does not have pores through which liquid can permeate. Porous means having pores through which liquid can permeate. In this case, the dense layer may be formed anywhere in the membrane, such as on the surface or inside the porous membrane. Heterogeneous membranes include composite membranes with different chemical structures and multilayer membranes such as three-layer structures. Heterogeneous membranes using poly-4-methylpentene-1 resin are particularly preferred because they have a dense layer that blocks liquid. Microporous membranes are membranes that have pores through which liquid cannot permeate. 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.

[0023] 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. Air supplied to the hollow portion 61 of the hollow fiber membrane 6 permeates through the membrane, supplying oxygen to the air electrode 2. At this time, some of the air that has permeated through the hollow fiber membrane 6 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 discharge of gases such as oxygen from the case 7 while suppressing leakage of the electrolyte 5.

[0024] 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 2, or they may be bundled together. Figure 2 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.

[0025] 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.

[0026] The hollow portion 61 of the hollow fiber membrane 6 is open to the outside of the case 7 from both ends of the hollow fiber membrane 6. That is, the hollow portion 61 has an opening 62 that opens at one end of the hollow fiber membrane 6 and an opening 63 that opens at the other end of the hollow fiber membrane 6. Both the opening 62 and the opening 63 are open to the outside of the case 7. The statement that the hollow portion 61 of the hollow fiber membrane 6 is open to the outside of the case 7 means that the hollow portion 61 of the hollow fiber membrane 6 is in communication with the space outside the case 7.

[0027] 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.

[0028] 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 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. 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, and 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.

[0029] Furthermore, as shown in Figures 3 and 4, the ends of the hollow fiber membrane 6 do not need to protrude from the surface of the case 7. Figures 3 and 4 are schematic diagrams of other examples of the air battery according to the embodiment.

[0030] In the air battery 1 shown in Figure 3, both 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.

[0031] In the air battery 1 shown in Figure 4, both 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.

[0032] 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.

[0033] As described above, in the air battery 1 according to this embodiment, the hollow fiber membrane 6, which is in communication with the outside of the case 7, is in contact with the air electrode 2, so that oxygen from the air can be supplied to the air electrode 2. Furthermore, since the hollow portion 61 of the hollow fiber membrane 6 is open to the outside of the case 7 from both ends of the hollow fiber membrane 6, air can be circulated from the opening 62 on one side of the hollow fiber membrane 6 to the opening 63 on the other side. 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 63 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. By arranging the air battery 1 so that the hollow fiber membrane 6 extends in the vertical direction, the natural circulation of air in the hollow portion 61 of the hollow fiber membrane 6 can be promoted. This makes it easy to control the temperature of the air battery 1.

[0034] Furthermore, in this air battery 1, since the ends 64 and 65 of the hollow fiber membrane 6 protrude from the surface of the case 7, air can be circulated from the opening on one side of the hollow fiber membrane to the opening on the other side.

[0035] Furthermore, in this air battery 1, even if the ends 64 and 65 of the hollow fiber membrane 6 do not protrude from the surface of the case 7, the case 7 has a first communication passage 73 that connects one opening 62 of the hollow portion 61 of the hollow fiber membrane 6 to the outside of the case 7, and a second communication passage 74 that connects the other opening 63 of the hollow portion 61 of the hollow fiber membrane 6 to the outside of the case 7, thereby allowing air to flow from one opening 62 to the other opening 63 of the hollow fiber membrane 6.

[0036] 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, and the temperature of the air electrode 2 can be easily controlled.

[0037] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above.

[0038] 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.

[0039] Furthermore, for example, if the hollow portion of the hollow fiber membrane is open to the outside of the case from both ends, the entire hollow fiber membrane may be housed in the case. In this case, for example, by connecting both ends of the hollow fiber membrane to a pipe that connects the inside and outside of the case, the hollow portion of the hollow fiber membrane can be made open to the outside of the case from both ends.

[0040] Furthermore, for example, an air battery may be equipped with an air supply device that supplies air to an opening on one side of the hollow fiber membrane.

[0041] Figure 5 is a schematic diagram of a modified air battery. The modified air battery 1A shown in Figure 5 is basically the same as the air battery 1 of the above embodiment, but differs from the air battery 1 of the above embodiment 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.

[0042] As shown in Figure 5, the air battery 1A is equipped with an air supply device 8 that supplies air to the opening 63 of the hollow fiber membrane 6, so that air can be forcibly circulated in the hollow portion 61 of the hollow fiber membrane 6. This makes temperature control of the air battery 1A even easier.

[0043] Furthermore, for example, an air battery may be composed of multiple air battery cells, with the hollow fiber membranes of each air battery cell being connected to one another.

[0044] FIG. 6 is a schematic diagram of a modified air battery. The modified air battery 1B shown in FIG. 6 includes 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 of the above embodiment. 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 of the above embodiment. And the hollow fiber membranes 6 of the plurality of air battery cells 11 are communicated with each other. In this case, the hollow fiber membranes 6 of the plurality of air battery cells 11 may be constituted by one same 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 may be indirectly connected via a pipe.

[0045] Thus, in the air battery 1B shown in FIG. 6, since the hollow fiber membranes 6 of the plurality of air battery cells 11 are communicated with each other, the temperature management of the plurality of air battery cells 11 can be efficiently and easily performed.

[0046] 1... air battery, 1A... air battery, 1B... air battery, 2... air electrode, 3... metal electrode, 4... separator, 5... electrolyte, 6... hollow fiber membrane, 7... case, 8... air supply device, 11... air battery cell, 61... hollow portion, 62... opening, 63... opening, 64... end portion, 65... end portion, 66... vicinity of end portion, 67... vicinity of end portion, 73... first communication path, 74... second communication path.

Claims

1. An air battery comprising: an air electrode; a metal electrode; an electrolyte; a hollow fiber membrane 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 portion of the hollow fiber membrane is open to the outside of the case from both ends of the hollow fiber membrane.

2. The air battery according to claim 1, wherein both ends of the hollow fiber membrane protrude from the surface of the case.

3. The air battery according to claim 1, wherein both ends of the hollow fiber membrane do not protrude from the surface of the case, and the case has a first communication passage that connects one opening of the hollow portion of the hollow fiber membrane to the outside of the case, and a second communication passage that connects the other opening of the hollow portion of the hollow fiber membrane to the outside of the case.

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

5. The air battery according to claim 1, further comprising an air supply device for supplying air to an opening on one side of the hollow fiber membrane.

6. The air battery according to claim 1, comprising a plurality of air battery cells each having an air electrode, a metal electrode, an electrolyte, a hollow fiber membrane, and a case, wherein the hollow fiber membranes of the plurality of air battery cells are in communication with one another.

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