air secondary battery

Abstract

To provide an air secondary battery in which leakage of electrolyte to an air passage through which air passes is prevented.SOLUTION: An air secondary battery comprises: an electrode group including an air electrode 40 and a negative electrode 60 that are overlapped via a separator 50; and a housing that houses together with the electrolyte, electrode group inside the housing. The housing comprises: a flow passage plate 20 having in one surface, an air passage 22 in which air reacted with the air electrode flows; a water-repellent film 30 that blocks the air passage to prevent leakage of the electrolyte to the air passage; and a conductive frame body 32 fixing a fluid-tight passage film to the flow passage plate to enclose the air electrode. The air passage is a groove formed in a region of the frame body on the one surface, a one end portion and the other end portion in a direction where the air flows, of the air passage are positioned in the region. The flow passage plate includes: flow channels 23 and 24 that are formed outside the frame body and communicated with an external portion; and a communication passage 27 that communicates the one end portion of the air passage with the flow channel. The communication passage is formed in a culvert shape in the flow passage plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air secondary battery. [Background technology]

[0002] Air batteries use oxygen from the air as the positive electrode active material and metals such as Li, Zn, Al, and Mg as the negative electrode. Because there is no need to incorporate a positive electrode active material into the battery, they have attracted attention due to their high energy density and ease of miniaturization and weight reduction. Furthermore, because air secondary batteries can be repeatedly charged and discharged, they are expected to be used as a driving power source for electric vehicles and for storing natural energy. When such air batteries are connected in series within an insulating frame as battery cells to form an assembled battery, it is necessary to supply air to each battery cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6056496 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, in air secondary batteries, an air passage through which air that reacts with the air electrode flows along a liquid-tight gas-permeable membrane is formed on one main surface of the flow path plate of the battery cell. The opening of this air passage is blocked by the liquid-tight gas-permeable membrane, preventing electrolyte leakage into the air passage. Meanwhile, when battery cells are stacked for series connection, the flow path that communicates with the outside air to supply air to each battery cell is configured to penetrate the flow path plate in its thickness direction and communicate with the flow path of an adjacent battery cell. Therefore, a branch path is formed in each battery cell to connect the flow path to the air passage.

[0005] In this case, if the edge of the liquid-tight gas-permeable membrane overlaps the branch path, there will be a portion where the frame cannot secure the liquid-tight gas-permeable membrane to the flow path plate. As a result, electrolyte may leak into the air passage due to the expansion and contraction of the electrode plate with the charge / discharge cycle or the increase in internal pressure caused by gas generation during overcharge.

[0006] In view of the above problems, an object of the present invention is to provide an air secondary battery that prevents leakage of electrolyte into the ventilation path. [Means for solving the problem]

[0007] In order to achieve the above object, the air secondary battery of the present invention is an air secondary battery comprising: an electrode group including an air electrode and a negative electrode stacked with a separator interposed therebetween; and a housing that houses the electrode group together with an electrolyte, wherein the housing comprises: a flow path plate having, on one main surface thereof, an air passage through which air that reacts with the air electrode flows; a liquid-tight gas-permeable membrane that blocks the air passage to prevent leakage of the electrolyte into the air passage; and a conductive frame that fixes the liquid-tight gas-permeable membrane to the flow path plate and surrounds the air electrode, wherein the air passage is a groove formed on the one main surface in an area defined within the frame of the frame, and one end and the other end of the air passage in the direction of air flow are located within the area, and the flow path plate has a flow path formed outside the frame and communicating with the outside, and a communication passage that connects one end of the air passage to the flow path, and the communication passage is formed in the shape of a culvert within the flow path plate. [Effects of the Invention]

[0008] According to the air secondary battery according to the embodiment of the present invention, leakage of the electrolyte contained in the separator into the air passage can be prevented. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a cross-sectional view of an air secondary battery according to an embodiment of the present invention. [Figure 2]1A shows a plan view of a water-repellent film and a frame fixed to a flow path plate, and FIG. 1B shows a schematic cross-sectional view of the flow path plate as viewed from the BB direction in FIG. 1A. [Figure 3] FIG. 10 is a schematic diagram showing a cross section of a flow path plate according to a second embodiment. [Figure 4] FIG. 10 is a schematic view showing a cross section of a flow path plate according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an air secondary battery according to this embodiment will be described with reference to the drawings.

[0011] Fig. 1 shows a cross-sectional view of an air secondary battery according to an embodiment. The air secondary battery comprises two air secondary battery cells (hereinafter referred to as battery cells) 1, 1 stacked and connected in series and housed in a battery case 10. Each battery cell 1 is arranged, in order from the positive electrode side to the negative electrode side, with a flow path plate 20, a water-repellent film 30, an air electrode (positive electrode) 40, a separator 50, a negative electrode 60, and a negative electrode current collector plate 70. The air electrode (positive electrode) 40 faces the negative electrode 60 with the separator 50 interposed therebetween.

[0012] 2(A), the flow path plate 20 is formed on one main surface 21 facing the air electrode 40 with air passages 22 along the in-plane direction of the air that reacts with the air electrode 40, an inlet passage 23 that introduces air into the air passage 22, and an outlet passage 24 that discharges the air that has flowed through the air passage 22 to the outside. The inlet passage 23 and the outlet passage 24 each serve as a flow path and penetrate the flow path plate 20 in the thickness direction. The flow path plate 20 is located on the positive electrode terminal plate side of the battery case 1.

[0013] Furthermore, the water-repellent film 30 is fixed to the main surface 21 of the flow path plate 20 by a rectangular frame 32 via a gas diffusion film 31. The water-repellent film 30 is fixed to the flow path plate 20 without covering the inlet path 23 and the outlet path 24, while closing the opening of the air passage 22 on the main surface 21. That is, the air passage 22 is located in an inner-frame area 25 defined by the frame 32, and the inlet path 23 and the outlet path 24 are both located in an outer-frame area 26.

[0014] The air passages 22 are formed as grooves on the main surface 21 of the flow path plate 20, extending from one end 22B to the other end 22C in the air passage direction, forming a single serpentine shape in plan view. One end 22B of the air passages 22 is located near the inlet passage 23 and communicates with each other via a communication passage 27 (described later). The other end 22C of the air passages 22 is located near the outlet passage 24 and communicates with each other via the communication passage 27. The air passages 22 supply oxygen from the air to the air electrode 40 during discharge and discharge oxygen generated from the air electrode 40 to the outside during charge. The air passages 22 open toward the air electrode 40, and their cross sections in a direction intersecting the air passage direction are formed into an appropriate shape, such as a rectangle. Note that the shape of the air passages 22 on one main surface 21, i.e., in plan view, shown in FIG. 2(A) is merely an example, and the number of folds in the serpentine shape is not particularly limited. In other embodiments, the battery cell 1 may have any suitable shape depending on its characteristics and specifications.

[0015] The gas diffusion membrane 31 is made of, for example, a porous substrate, and has the function of efficiently diffusing air and hydrogen necessary for the charge / discharge reaction of the air electrode 40 .

[0016] The water-repellent film 30 is a liquid-tight, air-permeable film made of a microporous resin film that allows air flowing through the air passage 22 to pass to the air electrode 40 while preventing leakage of the electrolyte on the air electrode 40 side into the air passage 22. The water-repellent film 30 has a shape and size that closes the opening 22A of the air passage 22 over the entire length from one end 22B to the other end 22C along the air flow direction, but does not close the inlet path 23 or the outlet path 24.

[0017] The frame 32 is made of a conductive material and has a rectangular shape. The frame surface 34 facing the water-repellent film 30 is flat. The frame 32 fixes the water-repellent film 30 to the flow path plate 20 and surrounds the air electrode 40 inside the frame 32.

[0018] The air electrode 40 is composed of a conductive electrode plate substrate having numerous pores and an air electrode mixture (positive electrode mixture) held within the pores and on the surface of the electrode plate substrate. Examples of such electrode plate substrates include foamed nickel and nickel mesh. The air electrode mixture contains a redox catalyst, a conductive agent, and a fluororesin. The redox catalyst is not particularly limited as long as it has a dual redox function. A preferred redox catalyst is pyrochlore-type bismuth ruthenium oxide.

[0019] The separator 50 is disposed between the air electrode 40 and the negative electrode 60 to electrically insulate them from each other. The separator 50 is made of, for example, a nonwoven fabric made of polyamide fibers or a nonwoven fabric made of polyolefin fibers, and contains an alkaline electrolyte solution therein. In this embodiment, the separator 50 has an overall rectangular shape, and is larger in plan view than the air electrode 40 and the negative electrode 60.

[0020] The negative electrode 60 comprises a conductive negative electrode substrate having numerous pores and a negative electrode mixture held within the pores and on the surface of the negative electrode substrate. For example, foamed nickel is used as the negative electrode substrate. The negative electrode mixture contains a hydrogen storage alloy powder made of hydrogen storage alloy particles capable of absorbing and releasing hydrogen as the negative electrode active material, a conductive agent, and a binder. Examples of the conductive agent that can be used include graphite and carbon black. For example, a rare earth-Mg-Ni hydrogen storage alloy is used as the hydrogen storage alloy that constitutes the hydrogen storage alloy particles.

[0021] The negative electrode current collector plate 70 is made of a conductive material, one side of which is electrically connected to the negative electrode 60, and the other side of which is electrically connected to the positive electrode side of an adjacent battery cell 1 connected in series, or to the negative electrode terminal plate 12 of the battery case 1.

[0022] The air electrode 40, separator 50, and negative electrode 60 constitute an electrode assembly 100, which is fixed to the flow path plate 20 by a gasket 33, and forms one battery cell 1.

[0023] Furthermore, the inlet path 23 and outlet path 24 of the flow path plate 20 each extend linearly from the flow path plate 20 to the negative electrode current collector plate 70 within one battery cell 1, forming an air intake path 81 and an exhaust path 82 within the battery cell 1. In the air intake path 81, the drawn air flows through the air intake path 81 toward the air vent path 22. On the other hand, in the exhaust path 82, the air flow that has flowed through the air vent path 22 is discharged to the outside.

[0024] The two battery cells 1, 1 are connected in series to form a battery pack, which is housed in a battery case 10. A positive electrode terminal plate 11 is electrically connected to one end of the battery case 10, and a negative electrode terminal plate 12 is electrically connected to the other end.

[0025] Next, the communication structure of the air passage 22, the inlet passage 23, and the outlet passage 24 in the flow path plate 20 will be described. First, the communication structure between the air passage 22 and the inlet passage 23 will be described. As shown in FIG. 2(A), in a plan view, a water-repellent film 30 is attached by a frame 32 to the main surface 21 of the flow path plate 20 facing the air electrode 40, and the entire air passage 22 is located inside the frame 32. That is, the air passage 22 is formed in an inner-frame region 25 surrounded by the frame 32 that fixes the water-repellent film 30 on the main surface 21 facing the air electrode 40. The inlet passage 23 is formed in a region 26 outside the frame 32, penetrating the flow path plate 20 in the thickness direction.

[0026] The introduction passage 23 communicates with the ventilation passage 22 via a communication passage 27. The communication passage 27 is formed in the flow passage plate 20 in the shape of a culvert, with one end communicating with one end 22B of the ventilation passage 22 and the other end opening to the side surface 23A of the introduction passage 23. In this embodiment, as shown in FIG. 2(B), the flow passage plate 20 is formed by integrating two metal plates, a first metal plate 201 and a second metal plate 202. The communication passage 27 is formed as a linear groove on the other main surface of the first metal plate 201, with one longitudinal end opening to the side surface 23A of the introduction passage 23 and the other end penetrating the first metal plate 201 in the thickness direction and communicating with the ventilation passage 22. Then, the groove of the first metal plate 201 is blocked by the second metal plate 202, so that the communication passage 27 becomes a culvert. By cutting and photo-etching the two metal plates 201 and 202 to integrate them, the communication passage 27 can be easily made into a culvert within the flow path plate 20.

[0027] Furthermore, with the above configuration, the portion of the water-repellent film 30 sandwiched between the flow path plate 20 and the frame 32 does not overlap with the air passage 22 in the thickness direction of the flow path plate 20. Therefore, the entire opening 22A of the air passage 22 on the main surface 21 of the flow path plate 20 is blocked by the water-repellent film 30, which prevents leakage of the electrolyte from the electrode assembly 100 side into the air passage 22. Note that the communication structure between the air passage 22 and the outlet passage 24 is not described in detail here, as the position of the outlet passage 24 in the flow path plate 20 is different from that of the inlet passage 23 and the air flows in the opposite direction.

[0028] 3 shows a flow path plate 120 that constitutes a battery cell 1 of the second embodiment. In the second embodiment, the configuration other than the flow path plate 120 is the same as in the above embodiment, so detailed description will be omitted.

[0029] The flow path plate 120 is formed by integrating two metal plates, a first metal plate 121 and a second metal plate 122. The air passages 22 are formed in a frame region 125 surrounded by a frame 32 that fixes the water-repellent film 30 on a main surface 121A of the first metal plate 121 facing the air electrode 40, and one end of the air passages 22 forms a through-hole 123 that penetrates in the thickness direction. Meanwhile, linear grooves 124 are formed on the main surface 122A side of the second metal plate 122 that is fixed to the first metal plate 121. One end of the groove 124 opens to the side surface portion 23A of the introduction path 23, and the other end is located at a position corresponding to the through-hole 123 of the first metal plate 121. When the first metal plate 121 and the second metal plate 122 are integrated, the through-hole 123 and the groove 124 form the communication path 27.

[0030] 4 shows a flow path plate 220 that constitutes a battery cell 1 of the third embodiment. In the third embodiment, the configuration other than the flow path plate 220 is the same as in the previously described embodiments, so detailed description will be omitted.

[0031] The flow path plate 220 is formed by integrating three metal plates: a first metal plate 221, a second metal plate 222, and a third metal plate 223. The air passage 22 is formed in a frame region 225 surrounded by a frame 32 that fixes the water-repellent film 30 on a main surface 221A of the first metal plate 221 facing the air electrode 40, and one end of the air passage 22 has a through-hole 226 that penetrates in the thickness direction. The second metal plate 222 is formed with the through-hole 226 and an elongated opening 227 that opens into the side surface 23A of the introduction passage 23. The third metal plate 223 is formed with a through-hole 228 that becomes part of the introduction passage 23. When the first metal plate 221 to the third metal plate 223 are integrated in order, a communication passage 27 that connects the air passage 22 and the introduction passage 23 is formed, forming an underdrain.

[0032] In an air secondary battery, regardless of which embodiment of the flow path plate 20, 120, or 220 is used in the battery cell 1, no part of the air passage 22 is located between the frame 32 that fixes the water-repellent film 30 to the main surface of the flow path plate 20, 120, or 220 and the flow path plate 20, 120, or 220, and the air passage 22 does not intersect with the frame 32, so leakage of the electrolyte contained in the electrode group 100 into the air passage 22 is reliably prevented.

[0033] Furthermore, the inlet passages 23 and outlet passages 24 both linearly penetrate the stacked battery cells 1 in the thickness direction of each component. Therefore, when multiple battery cells 1 are stacked for series connection, the inlet passages 23 and outlet passages 24 of each battery cell 1 are in communication with the linear passages. In this way, the air secondary battery is provided with the intake passages 81 and exhaust passages 82 that extend linearly, allowing air to be supplied to and exhausted from each battery cell 1 uniformly.

[0034] Furthermore, the flow path plate 20 is fabricated by processing at least two metal plates and then integrating them. Therefore, the communication path 27 can be fabricated by forming a groove on the surface of one metal plate opposite the air electrode and closing the opening of the groove with the other metal plate. Therefore, the communication path can easily be formed in the shape of a culvert within the flow path plate.

[0035] The flow path plate according to the embodiment can also be used as a flow path plate for an air secondary battery consisting of a single battery cell. [Explanation of symbols]

[0036] 1 battery cell 10 Battery case 20 Flow path plate 23, 24 Flow path 22 Ventilation channel 27 Communication path 30 Water-repellent film 32 Frame 40 Air electrode 50 Separator 60 negative electrode

Claims

1. An air secondary battery comprising: an electrode group including an air electrode and a negative electrode stacked with a separator interposed therebetween; and a housing that houses the electrode group together with an electrolyte solution, The housing includes: a flow path plate having an air passage on one main surface through which air that reacts with the air electrode flows; a liquid-tight gas-permeable membrane that blocks the gas passage to prevent leakage of the electrolyte into the gas passage; a conductive frame that fixes the liquid-tight gas-permeable membrane to the flow path plate and surrounds the air electrode; Equipped with the air passage is a groove formed in an area defined within the frame of the frame body on the one main surface, and one end and the other end of the air passage in the air flow direction are located within the area, the flow path plate has a flow path formed outside the frame body and communicating with the outside, and a communication path that connects one end of the ventilation path to the flow path, The air secondary battery, wherein the communication passage is formed in the flow path plate in the shape of a culvert.

2. The air secondary battery in accordance with claim 1 , wherein the flow path is spaced apart from a frame-shaped region on one main surface of the flow path plate that faces a fixing surface of the frame.

3. The flow path plate is provided by stacking two or more metal plates in a thickness direction, the flow path is a through hole that penetrates the flow path plate in a thickness direction, 3. The air secondary battery according to claim 1, wherein one end of the communication passage in the air flow direction communicates with one end of the air passage, and the other end opens into a side surface of the flow path.

4. An air secondary battery in which a plurality of air secondary battery cells are stacked and connected in series, Each of the plurality of air secondary battery cells includes an electrode group including an air electrode and a negative electrode stacked with a separator interposed therebetween, and a housing that houses the electrode group together with an electrolyte solution, The housing includes: a flow path plate having an air passage on one main surface through which air that reacts with the air electrode flows and having two flow paths penetrating in a thickness direction; a liquid-tight gas-permeable membrane that blocks the gas passage to prevent leakage of the electrolyte into the gas passage; a conductive frame that fixes the liquid-tight gas-permeable membrane to the flow path plate and surrounds the air electrode; a negative electrode current collector located on the opposite side of the negative electrode from the separator, electrically connected to the negative electrode, and connected to an adjacent air secondary battery; Equipped with the air passage is a groove formed in a region on the one main surface surrounded by an inner frame of the frame body, and both ends of the air passage in the air flow direction are located within the region; the two flow paths are located outside the frame and communicate with the outside, the flow path plate has communication paths that connect both ends of the air passage to the corresponding flow paths, The air secondary battery, wherein the communication passage is formed in the flow path plate in the shape of a culvert and opens to a side surface of the flow path.

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