JP7797219B2 - air secondary battery - Google Patents

Description

The present invention relates to an air secondary battery.

Air batteries are batteries that 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 provide a positive electrode active material inside the battery, they have attracted attention due to their high energy density and ease of miniaturization and lightweight design. Furthermore, because air secondary batteries can be repeatedly charged and discharged, they are expected to be used as driving power sources for electric vehicles and for storing natural energy. When such air batteries are connected in series as battery cells, for example, within an insulating frame to create a battery pack, it is necessary to supply air to each battery cell.

Patent No. 6056496

Typically, in air secondary batteries, the 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 from leaking into the passage. On the other hand, 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.

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 can leak into the air passage due to the expansion and contraction of the electrode plate during charge/discharge cycles, or the increase in internal pressure caused by gas generation during overcharge.

In view of the above problems, the object of the present invention is to provide an air secondary battery that prevents electrolyte leakage into the ventilation path.

To achieve the above objective, 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. The housing comprises 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 air passage and prevents the electrolyte from leaking into the air passage, and a conductive frame that secures the liquid-tight gas-permeable membrane to the flow path plate and surrounds the air electrode. The air passage is a groove formed on the one main surface in an area defined within the frame, and one and the other ends of the air passage in the direction of air flow are located within the area. 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.

The air secondary battery according to the embodiment of the present invention can prevent the electrolyte contained in the separator from leaking into the air passage.

1 shows a cross-sectional view of an air secondary battery according to an embodiment of the present invention. 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 direction BB in FIG. 1A. FIG. 10 is a schematic diagram showing a cross section of a flow path plate according to a second embodiment. FIG. 10 is a schematic diagram showing a cross section of a flow path plate according to a third embodiment.

The air secondary battery according to this embodiment will be described below with reference to the drawings.

Figure 1 shows a cross-sectional view of an air secondary battery according to an embodiment. An air secondary battery comprises two stacked air secondary battery cells (hereinafter referred to as battery cells) 1, 1 connected in series and housed in a battery case 10. Arranged in each battery cell 1, from the positive electrode side to the negative electrode side, in this order, are 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 via the separator 50.

The flow path plate 20 is made of a conductive rectangular flat plate, and as shown in Figure 2(A), on one main surface 21 facing the air electrode 40, there are formed 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 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.

Furthermore, the water-repellent film 30 is fixed to the main surface 21 of the flow path plate 20 via a rectangular frame 32 and 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 outlet path 24, while blocking the opening on the main surface 21 of the air passage 22. In other words, the air passage 22 is located in the inner-frame area 25 defined by the frame 32, and the inlet path 23 and outlet path 24 are both located in the outer-frame area 26.

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 below). 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 exhaust 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 intersecting the air passage direction are formed into an appropriate shape, such as a rectangle. Note that the shape of the air passage 22 on one main surface 21, i.e., in plan view, shown in Figure 2(A) is merely an example, and the number of folds in the serpentine shape is not particularly limited. In other embodiments, the shape can be adjusted according to the characteristics and specifications of the battery cell 1.

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

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

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, fixing the water-repellent film 30 to the flow path plate 20 and enclosing the air electrode 40 inside the frame 32.

The air electrode 40 consists of a conductive electrode plate substrate with 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 the dual redox function. A preferred redox catalyst is pyrochlore-type bismuth ruthenium oxide.

The separator 50 is disposed between the air electrode 40 and the negative electrode 60 to electrically insulate them. The separator 50 is made, for example, of a nonwoven fabric made of polyamide fibers or a nonwoven fabric made of polyolefin fibers, and contains an alkaline electrolyte solution. In this embodiment, the separator 50 has an overall rectangular shape, and its planar shape is larger than the planar shapes of the air electrode 40 and the negative electrode 60.

The negative electrode 60 consists of a conductive negative electrode substrate with 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 hydrogen storage alloy powder, which serves as the negative electrode active material and is made of hydrogen storage alloy particles capable of absorbing and releasing hydrogen, a conductive agent, and a binder. Examples of conductive agents that can be used include graphite and carbon black. The hydrogen storage alloy that makes up the hydrogen storage alloy particles is, for example, a rare earth-Mg-Ni hydrogen storage alloy.

The negative electrode current collector plate 70 is made of a conductive material, with one side electrically connected to the negative electrode 60 and the other side 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.

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

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, respectively. In the air intake path 81, drawn-in air flows through the air intake path 81 toward the air vent path 22. Meanwhile, in the exhaust path 82, the air flow that has flowed through the air vent path 22 is discharged to the outside.

Two of the above 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.

Next, the communication structure of the air passage 22, inlet passage 23, and outlet passage 24 in the flow path plate 20 will be described. First, the communication structure between the air passage 22 and 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 area 25 on the main surface 21 facing the air electrode 40, surrounded by the frame 32 that secures the water-repellent film 30. The inlet passage 23 is formed in an area 26 outside the frame 32, penetrating the flow path plate 20 in the thickness direction.

The inlet passage 23 communicates with the ventilation passage 22 via a communication passage 27. The communication passage 27 is formed in the shape of a culvert inside the flow path plate 20, 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 inlet passage 23. In this embodiment, as shown in FIG. 2(B), the flow path 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 inlet passage 23 and the other end penetrating the first metal plate 201 in the thickness direction and communicating with the ventilation passage 22. When the groove in the first metal plate 201 is blocked by the second metal plate 202, 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 easily be made into a culvert within the flow path plate 20.

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, preventing leakage of 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 outlet passage 24 is located in a different position on the flow path plate 20 from the inlet passage 23 and the air flows in the opposite direction.

Figure 3 shows the flow path plate 120 that constitutes the 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.

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 passage 22 is formed in a frame region 125 surrounded by a frame 32 that secures the water-repellent film 30 on the main surface 121A of the first metal plate 121 facing the air electrode 40, and one end of the air passage 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 secured to the first metal plate 121. One end of the groove 124 opens to the side surface 23A of the introduction path 23, and the other end is located at a position corresponding to the through-hole 123 in the first metal plate 121. When the first metal plate 121 and the second metal plate 122 are integrated, the through-hole 123 and groove 124 form the communication path 27.

Figure 4 shows the flow path plate 220 that constitutes the 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.

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 area 225 surrounded by a frame 32 that secures the water-repellent film 30 on the 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 through 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 path 23. The third metal plate 223 is formed with a through-hole 228 that becomes part of the introduction path 23. When the first metal plate 221 through the third metal plate 223 are integrated in order, a communication passage 27 is formed that connects the air passage 22 and the introduction path 23, forming an underdrain.

In an air secondary battery, regardless of the battery cell 1 using any of the embodiments of the flow path plates 20, 120, and 220, 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, and 220, and the flow path plate 20, 120, and 220, nor do the air passages 22 intersect. This reliably prevents leakage of the electrolyte contained in the electrode group 100 into the air passage 22.

Furthermore, the inlet passages 23 and outlet passages 24 both penetrate the stacked battery cells 1 in a linear manner 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 connected to the linear passages. In this way, the air secondary battery is provided with intake passages 81 and exhaust passages 82 that extend linearly, allowing air to be supplied to and discharged from each battery cell 1 uniformly.

Furthermore, the flow path plate 20 is made by processing at least two metal plates and then integrating them. Therefore, the communication path 27 can be made by forming a groove on the surface of one metal plate opposite the air electrode and then blocking the opening of that groove with the other metal plate. Therefore, the communication path can easily be made into a culvert-like shape within the flow path plate.

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.

REFERENCE SIGNS LIST 1 Battery cell 10 Battery case 20 Flow path plate 23, 24 Flow path 22 Ventilation path 27 Communication path 30 Water-repellent film 32 Frame 40 Air electrode 50 Separator 60 Negative electrode

Claims (4)

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