Zinc secondary battery

Abstract

A zinc secondary battery (1) comprises: an electrode laminate (3); a case (2) which accommodates the electrode laminate (3); and an alkaline electrolyte solution (4) which is accommodated in the case (2) and in which the entire electrode laminate (3) is immersed. The electrode laminate (3) comprises: a positive electrode plate (31) that includes a positive electrode active material layer (312); a negative electrode plate (32) that faces the positive electrode plate (31) while being positioned away from the positive electrode plate (31) in the thickness direction thereof, the negative electrode plate (32) comprising a negative electrode active material layer (322) that comprises at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound; and a separator (33) that isolates the positive electrode plate (31) from the negative electrode plate (32) and can conduct hydroxide ions. An excess volume ratio, which is the percentage of a second volume V2 of the space from a ceiling surface (23) of the case (2), the ceiling surface serving as the upper end of the internal space, to a liquid surface (41) of the alkaline electrolyte solution (4), to a first volume V1 of the internal space of the case (2), is 3% or less.

Description

Zinc secondary battery

[0001] This disclosure relates to a zinc secondary battery. This application claims priority to Japanese Patent Application No. 2024-039436 filed on March 13, 2024, and to International Application No. PCT / JP2024 / 036003 filed on October 8, 2024, and incorporates by reference all the contents of the aforementioned international applications.

[0002] A secondary battery (nickel-metal hydride secondary battery) is known that includes an electrode stack, a case, and an alkaline electrolyte (see, for example, Patent Document 1 below). In the secondary battery described in Patent Document 1, the alkaline electrolyte is poured into the case in an amount that is 85% to 100% of the internal space of the case.

[0003] Japanese Patent Application Publication No. 10-247514

[0004] In zinc secondary batteries containing zinc in the negative electrode active material layer of the electrode laminate, oxygen in the upper space of the internal space of the case, i.e., oxygen in the space above the liquid level of the alkaline electrolyte, is likely to dissolve in the alkaline electrolyte. In this case, the oxygen promotes the oxidation of zinc. This causes problems such as a decrease in the capacity of the zinc secondary battery and a shortened lifespan of the zinc secondary battery.

[0005] An object of the present disclosure is to provide a zinc secondary battery that can suppress a decrease in capacity and has a long life.

[0006] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and immersed entirely in the electrode stack. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. An excess volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte, relative to a first volume V1 of the internal space of the case, is 3% or less.

[0007] In the zinc secondary battery according to the present disclosure, the decrease in capacity can be suppressed and the battery life is long.

[0008] Fig. 1 is a perspective view of an embodiment of a zinc secondary battery according to the present disclosure. Fig. 2 is a cross-sectional view of the zinc secondary battery shown in Fig. 1. Fig. 3 is a cross-sectional view of the zinc secondary battery shown in Fig. 1. Fig. 4 is a perspective view of an electrode laminate. Fig. 5 is a cross-sectional view of an electrode laminate. Fig. 6 is a cross-sectional view of a first modified zinc secondary battery. Fig. 7 is a cross-sectional view of a valve seat and a valve body portion provided in the zinc secondary battery shown in Fig. 6. Fig. 8 is a cross-sectional view of a valve seat and a valve body portion provided in a second modified zinc secondary battery.

[0009] [Summary of the embodiment] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and in which the entire electrode stack is immersed. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. An excess volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte, relative to a first volume V1 of the internal space of the case, is 3% or less.

[0010] In this zinc secondary battery, the excess volume ratio is small, at 3% or less, so the internal space is relatively narrow, which reduces the dissolution of oxygen into the alkaline electrolyte. This prevents the capacity of the zinc secondary battery from decreasing. As a result, this zinc secondary battery has a long life.

[0011] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and in which the entire electrode stack is immersed. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. The excess volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte relative to a first volume V1 of the internal space of the case, is 8% or less. In the depth direction of the alkaline electrolyte, the electrode stack includes a lower end and an upper end. The immersion ratio, which is the percentage of a length L4 from the lower end to the level of the alkaline electrolyte relative to a length L3 from the lower end to the upper end, is 104% or more.

[0012] In this zinc secondary battery, the excess volume ratio is low at 8% or less, and the immersion ratio is high at 104% or more. Therefore, the internal space is relatively narrow. This reduces the dissolution of oxygen into the alkaline electrolyte. Therefore, the decrease in capacity of the zinc secondary battery can be suppressed. As a result, this zinc secondary battery has a long life.

[0013] In the zinc secondary battery described above, the immersion rate may be 109% or more.

[0014] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and immersed entirely in the electrode stack. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. A surplus volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte relative to a first volume V1 of the internal space of the case, is 8% or less. The battery further includes a container made of an impregnated sheet that can be impregnated with the alkaline electrolyte and has a closed space therein.

[0015] In this zinc secondary battery, the excess volume ratio is low, at 8% or less, so the internal space is relatively narrow, thereby reducing the dissolution of oxygen into the alkaline electrolyte. This reduces the capacity loss of the zinc secondary battery. As a result, this zinc secondary battery has a long life. Furthermore, at least one of the positive and negative electrode plates is housed within the closed space of the housing. Because at least one of the positive and negative electrode plates is housed within the closed space of the housing, particles made of the material of the positive electrode plate are prevented from flowing onto the negative electrode plate, thereby reducing the capacity loss.

[0016] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and immersing the entire electrode stack. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. A surplus volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte, relative to a first volume V1 of the internal space of the case, is 8% or less. The case includes a case body having an opening at the upper end and a lid that closes the opening. The zinc secondary battery comprises a first terminal that penetrates the lid, a first tab lead connected to the positive electrode plate and the first terminal, a first joint portion that joins the first terminal and the first tab lead, a second terminal that penetrates the lid and is positioned apart from the first terminal, a second tab lead that is connected to the negative electrode plate and the second terminal, a second joint portion that joins the second terminal and the second tab lead, and a covering portion that covers at least one of the first joint portion and the second joint portion, and that can prevent alkaline electrolyte from coming into contact with the joint portion.

[0017] In this zinc secondary battery, the above-mentioned excess volume ratio is low, at 8% or less, so the internal space is relatively narrow, thereby reducing oxygen dissolution into the alkaline electrolyte. This reduces capacity degradation of the zinc secondary battery. As a result, this zinc secondary battery has a long life. Furthermore, in the present disclosure, when the tab lead and the terminal are joined, if the joint contains conductive foreign matter (such as metallic foreign matter), the foreign matter is likely to contaminate the alkaline electrolyte. In particular, in this zinc secondary battery, the immersion rate is high as described above, so there is a high probability of contact between the foreign matter and the alkaline electrolyte. Therefore, the capacity of the zinc secondary battery is likely to decrease. However, in this zinc secondary battery, the covering portion covers the joint and prevents the alkaline electrolyte from contacting the joint, thereby reducing the above-mentioned contamination and reducing capacity degradation.

[0018] A zinc secondary battery according to the present disclosure includes an electrode stack, a case that houses the electrode stack, and an alkaline electrolyte housed in the case and immersed entirely in the electrode stack. The electrode stack includes a positive electrode plate including a positive electrode active material layer, a negative electrode plate facing the positive electrode plate and spaced apart in the thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a separator that separates the positive electrode plate and is capable of conducting hydroxide ions. An excess volume ratio, which is the percentage of a second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the level of the alkaline electrolyte, relative to a first volume V1 of the internal space of the case, is 8% or less. The case includes a case body having an opening at its upper end, a lid that closes the opening and has an exhaust passage formed therein that connects the interior space of the case to the exterior space of the case, and a valve body attached to the lid and closing the exhaust port, which is the end of the exhaust passage formed on the surface of the lid that contacts the exterior space. The lid includes a plate-shaped base portion including a lower surface that defines a ceiling surface and an inner circumferential surface connected to the inner edge of the lower surface, a second inner circumferential surface that extends from an edge of the inner circumferential surface farther from the lower surface and defines the exhaust passage together with the inner circumferential surface, and an outer circumferential surface located outside the second inner circumferential surface, and a valve seat portion having an upper edge that defines the exhaust port. The valve body includes a cylindrical first portion that contacts at least the upper end of the outer circumferential surface over the entire circumferential direction, and a second portion that faces the exhaust port and closes the second opening defined by the edge of the first portion farther from the lower surface. The first portion is elastically deformable outward based on the pressure in the interior space. When the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the first part elastically deforms outward, forming a gap between the outer peripheral surface and the first part, thereby opening the exhaust port. A liquid level distance L5, which is the distance from the exhaust port to the liquid level of the alkaline electrolyte in the depth direction of the alkaline electrolyte, is 15 mm or more.

[0019] In this zinc secondary battery, the excess volume ratio is as low as 8% or less, so the internal space is relatively narrow, which reduces the dissolution of oxygen into the alkaline electrolyte. This prevents the capacity of the zinc secondary battery from decreasing. As a result, this zinc secondary battery has a long life.

[0020] Generally, when a zinc secondary battery discharges, oxygen is generated by a side reaction in the positive electrode plate. If oxygen remains in the internal space of the case, it dissolves in the alkaline electrolyte, resulting in a shortened lifespan of the zinc secondary battery. However, in the zinc secondary battery of the present disclosure, the valve body opens the exhaust port when the pressure in the internal space becomes 1 kPa to 40 kPa higher than the pressure in the external space. In other words, the valve body opens the exhaust port when the difference between the pressure in the internal space and the pressure in the external space (operating pressure) becomes 1 kPa to 40 kPa higher. This allows oxygen in the internal space to be exhausted to the external space through the exhaust port before an excessive amount of oxygen remains in the internal space. Therefore, the zinc contained in the negative electrode plate is less likely to oxidize. As a result, the lifespan of the zinc secondary battery can be extended.

[0021] On the other hand, when the operating pressure is low, between 1 kPa and 40 kPa, the alkaline electrolyte is likely to leak into the external space through the exhaust port. However, in the zinc secondary battery of the present disclosure, the liquid level distance L5 is long, at 15 mm or more, so the alkaline electrolyte is less likely to leak into the external space through the exhaust port.

[0022] As a result, in the zinc secondary battery of the present disclosure, even though oxygen in the internal space is exhausted to the external space through the exhaust port, the alkaline electrolyte is less likely to leak into the external space through the exhaust port.

[0023] In the zinc secondary battery described above, the liquid level may be located below the exhaust passage. According to the present disclosure, even if the alkaline electrolyte solution splashes above the liquid level, droplets of the alkaline electrolyte solution are unlikely to leak into the external space through the exhaust passage.

[0024] In the zinc secondary battery described above, the alkaline electrolyte may contain sodium hydroxide, which has a relatively large hydrated ionic radius, and therefore can prevent the alkaline electrolyte from leaking out of the case.

[0025] [Specific Example of Embodiment] Specific embodiments of the zinc secondary battery of the present disclosure will be described with reference to Figs. 1 to 5. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and their description will not be repeated. Fig. 1 is a perspective view of an embodiment of the zinc secondary battery according to the present disclosure. Fig. 2 is a cross-sectional view of the zinc secondary battery shown in Fig. 1. Fig. 2 is a cross-sectional view taken along line YY in Fig. 3. Fig. 3 is a cross-sectional view of the zinc secondary battery shown in Fig. 1. Fig. 3 is a cross-sectional view taken along line XX in Fig. 2. Fig. 4 is a perspective view of an electrode laminate. Fig. 5 is a cross-sectional view of the electrode laminate.

[0026] [Basic Configuration of Zinc Secondary Battery 1 ] The zinc secondary battery 1 includes a case 2 , an electrode stack 3 , and an alkaline electrolyte 4 .

[0027] [Case 2] Case 2 has a rectangular box shape. Case 2 has a case body 21 and a lid 22. The case body 21 has an opening 210 at its upper end. When a bottom wall 211 (described below) of the case 2 is placed on a horizontal surface S, the upper end is the end facing opposite the vertically downward direction. The case body 21 includes the bottom wall 211 and side walls 212, 213, 214, and 215. When the case 2 is placed on the horizontal surface S, the bottom wall 211 extends along the horizontal surface S. The bottom wall 211 has a rectangular shape when viewed in the thickness direction TD. The side walls 212, 213, 214, and 215 extend upward from the outer edge of the bottom wall 211. The side walls 212 and 213 face each other. The side walls 212 and 213 are parallel to each other. The side walls 214 and 215 face each other. The side walls 214 and 215 are parallel to each other. The upper ends of the side walls 212, 213, 214, and 215 form an opening 210. The lid 22 closes the opening 210. The lid 22 faces the bottom wall 211. The lid 22 has a flat plate shape. The lower surface of the lid 22 is a ceiling surface 23 that forms the upper end of the internal space of the case 2. The case 2 is made of an insulator. The insulator of the case 2 is resistant to the alkaline electrolyte 4. The insulator contains a resin. Examples of resins include polyolefin, acrylonitrile-butadiene-styrene, and modified polyphenylene ether.

[0028] [Electrode Stack 3] The electrode stack 3 is housed in the case 2. The electrode stack 3 has a rectangular shape when viewed in the thickness direction TD of the electrode stack 3. The electrode stack 3 includes an upper end 35 and a lower end 36. The lower end 36 is located away from the upper end 35 in the depth direction DD of the alkaline electrolyte 4. As shown in FIG. 4 , the electrode stack 3 includes a positive electrode plate 31 and a negative electrode plate 32. Specifically, the electrode stack 3 includes a plurality of positive electrode plates 31 and a plurality of negative electrode plates 32. In the electrode stack 3, the positive electrode plates 31 and the negative electrode plates 32 are arranged alternately in the thickness direction TD.

[0029] [Positive Electrode Plate 31] As shown in Fig. 5, the positive electrode plate 31 includes a positive electrode current collector 311 and a positive electrode active material layer 312. The positive electrode current collector 311 has a rectangular flat plate shape. The positive electrode current collector 311 is made of a conductor. The positive electrode current collector 311 may be a conductor foam. The positive electrode active material layer 312 is disposed in contact with the positive electrode current collector 311. The positive electrode active material layer 312 contains nickel hydroxide or nickel oxyhydroxide. Because the positive electrode active material layer 312 contains nickel hydroxide or nickel oxyhydroxide, the zinc secondary battery 1 is sometimes referred to as a nickel-zinc secondary battery.

[0030] [Negative Electrode Plate 32] The negative electrode plate 32 faces the positive electrode plate 31 in the thickness direction TD. The negative electrode plate 32 is positioned away from the positive electrode plate 31 in the thickness direction TD. The negative electrode plate 32 includes a negative electrode current collector 321 and a negative electrode active material layer 322. The negative electrode current collector 321 overlaps the positive electrode current collector 311 in the thickness direction TD. The negative electrode current collector 321 has a rectangular plate shape. The negative electrode active material layer 322 is disposed in contact with the negative electrode current collector 321. The negative electrode active material layer 322 includes at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. Examples of zinc alloys include zinc alloys containing indium, bismuth, and aluminum. Examples of zinc compounds include zinc hydroxide and calcium zincate.

[0031] [Separator 33 and Container 34] The electrode stack 3 further includes a separator 33 and a container 34. The separator 33 separates the positive electrode plates 31 and the negative electrode plates 32. Specifically, the separator 33 encases each of the multiple negative electrode plates 32. A portion of the separator 33 is located between the positive electrode plates 31 and the negative electrode plates 32. The separator 33 and the negative electrode plates 32 are included in the negative electrode structure 325. That is, the negative electrode structure 325 includes the separator 33 and the negative electrode plates 32. The separator 33 can conduct hydroxide ions. An example of the separator 33 is a layered double hydroxide (LDH) separator. An LDH separator is described in JP 2023-124426 A.

[0032] In the present disclosure, the container 34 is composed of an impregnated sheet 341 that can be impregnated with the alkaline electrolyte 4. The container 34 has a closed space inside. The positive electrode plate 31 is housed in the closed space of the container 34. The container 34 and the positive electrode plate 31 are included in a positive electrode structure 315. In other words, the positive electrode structure 315 includes the container 34 and the positive electrode plate 31. Examples of the impregnated sheet 341 include a nonwoven fabric, a water-absorbent resin sheet, a porous sheet, and a spacer, and nonwoven fabric is preferred. The thickness of the impregnated sheet 341 is 10 μm or more and 200 μm or less. In the present disclosure, in the container 34, the outer edges of multiple impregnated sheets 341 are joined together at overlapping portions. In the electrode stack 3, the positive electrode structures 315 and the negative electrode structures 325 are alternately arranged (stacked).

[0033] [First terminal 51, first tab lead 52, first joint portion 53, second terminal 61, second tab lead 62, and second joint portion 63] The zinc secondary battery 1 further includes a first terminal 51, a first tab lead 52, a first joint portion 53, a second terminal 61, a second tab lead 62, and a second joint portion 63.

[0034] As shown in FIGS. 1 to 3 , the first terminal 51 penetrates the lid 22. Specifically, as shown in FIG. 1 , the first terminal 51 penetrates a first sealant 221 filled in a first through-hole of the lid 22. The first sealant 221 is made of rubber. The first terminal 51 extends in the height direction. As shown in FIGS. 2 and 5 , a lower end 511 of the first terminal 51 has a flat plate shape. The first terminal 51 is made of a conductor. The conductor includes iron. A plating layer 5110 is provided on the surface of the lower end 511 of the first terminal 51. The first terminal 51 is used as a positive electrode terminal.

[0035] The first tab lead 52 is connected to the positive electrode plate 31 and the first terminal 51. That is, the positive electrode plate 31 and the first terminal 51 are electrically connected to each other by the first tab lead 52. The first tab leads 52 extend from the upper ends of the multiple positive electrode plates 31 and are stacked together. The first tab leads 52 include a stacking portion 521 at their tips. Each of the multiple first tab leads 52 penetrates a joint portion corresponding to the upper edge of each of the multiple housings 34. The first tab leads 52 extend from the upper end of the positive electrode current collector 311.

[0036] The first joint portion 53 joins the first terminal 51 and the first tab lead 52. The first joint portion 53 is formed by joining such as laser welding at the overlapping portion of the lower end portion 511 of the first terminal 51 and the laminated portion 521 of the first tab lead 52. When viewed in the thickness direction TD, an opening 5111 is formed in the plating layer 5110 facing the laminated portion 521 at the center of the first joint portion 53. In the peripheral portion of the first joint portion 53, metallic foreign matter 55 resulting from the joining described above is allowed to be present on the surface of the laminated portion 521.

[0037] As shown in FIG. 1 , the second terminal 61 penetrates the lid 22. The second terminal 61 is positioned apart from the first terminal 51. The second terminal 61 penetrates a second sealant 222 filled in the second through-hole of the lid 22. The second sealant 222 is made of rubber. The second terminal 61 extends in the height direction. As shown in FIGS. 2 and 5 , a lower end 611 of the second terminal 61 has a flat plate shape. The second terminal 61 is made of a conductor. The conductor includes iron. A plating layer 6110 is provided on the surface of the lower end 611 of the second terminal 61. The second terminal 61 is used as a negative terminal.

[0038] The second tab lead 62 is connected to the negative electrode plate 32 and the second terminal 61. That is, the negative electrode plate 32 and the second terminal 61 are electrically connected to each other by the second tab lead 62. The second tab leads 62 extend from the upper ends of the multiple negative electrode plates 32 and are aggregated and stacked. The second tab lead 62 includes a laminated portion 621 at its tip. As shown in FIG. 4 , the second tab lead 62 is misaligned with the first tab lead 52 when viewed in the thickness direction TD. The laminated portion 621 of the second tab lead 62 is disposed at a distance from the laminated portion 521 of the first tab lead 52.

[0039] 5 , the second joint portion 63 joins the second terminal 61 and the second tab lead 62. The second joint portion 63 is formed by joining such as laser welding at the overlapping portion of the lower end portion 611 of the second terminal 61 and the laminated portion 621 of the second tab lead 62. When viewed in the thickness direction TD, an opening 6111 is formed in the plating layer 6110 facing the laminated portion 621 at the center of the second joint portion 63. In the peripheral portion of the second joint portion 63, metallic foreign matter 65 resulting from the joining described above is allowed to be present on the surface of the laminated portion 621.

[0040] [Alkaline Electrolyte 4] As shown in FIGS. 2 and 3 , the alkaline electrolyte 4 is contained in the case 2. The entire electrode stack 3 is immersed in the alkaline electrolyte 4. The alkaline electrolyte 4 contains an alkali metal hydroxide and water. That is, the alkaline electrolyte 4 is an aqueous solution containing an alkali metal hydroxide. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. These can be used alone or in combination. A preferred example of the alkali metal hydroxide is sodium hydroxide. Because the hydrated ionic radius of sodium hydroxide is larger than that of potassium hydroxide, at least one of the following phenomena can be suppressed: the phenomenon of electrolyte migration between the first sealant 221 (see FIG. 1 ) and the first terminal 51 and leaking out of the case 2 (creep phenomenon); and the phenomenon of electrolyte migration between the second sealant 222 (see FIG. 1 ) and the second terminal 61 and leaking out of the case 2 (creep phenomenon). The concentration of the alkali metal hydroxide in the alkaline electrolyte 4 is 0.1 mol / L or more and 10 mol / L or less. The liquid level 41 of the alkaline electrolyte 4 is located above the upper end 35 of the electrode stack 3. The liquid level 41 of the alkaline electrolyte 4 may be located above the first bonding portion 53 and the second bonding portion 63 (see FIG. 5 ). The liquid level 41 is located below the ceiling surface 23 of the lid 22.

[0041] [Excess Volume Ratio] In the present disclosure, the excess volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface 23 of the case 2 that forms the upper end of the internal space to the liquid level 41 of the alkaline electrolyte 4 relative to the first volume V1 of the internal space of the case 2, is 8% or less, preferably 5% or less, and more preferably 3% or less. In the present disclosure, since the excess volume ratio is equal to or less than the above-mentioned upper limit, the space above the liquid level 41 of the alkaline electrolyte 4 is narrow. Therefore, the amount of oxygen present in the space that dissolves into the alkaline electrolyte 4 is reduced. This oxygen then suppresses oxidation of zinc in the negative electrode active material layer 322 of the negative electrode plate 32. This suppresses a decrease in the capacity of the zinc secondary battery 1. As a result, the life of the zinc secondary battery 1 is extended (effect based on the excess volume ratio).

[0042] The excess volume ratio can also be defined as the percentage of the height H2 from the liquid level 41 of the alkaline electrolyte 4 to the ceiling surface 23 of the lid 22 relative to the height H1 of the internal space of the case 2.

[0043] [Immersion Ratio] In the depth direction DD of the alkaline electrolyte 4, the immersion ratio, which is the percentage of the length L4 from the lower end 36 of the electrode stack 3 to the liquid level 41 of the alkaline electrolyte 4 relative to the length L3 from the lower end 36 to the upper end 35, is 104% or more, preferably 107% or more, and more preferably 109% or more. Specifically, if the excess volume ratio is equal to or less than the upper limit and the immersion ratio is equal to or greater than the lower limit, the amount of oxygen dissolved in the alkaline electrolyte 4 is reduced, similar to the effect based on the excess volume ratio. This oxygen then suppresses oxidation of zinc in the negative electrode active material layer 322 of the negative electrode plate 32. This suppresses a decrease in the capacity of the zinc secondary battery 1. As a result, the life of the zinc secondary battery 1 is extended.

[0044] The oxygen mentioned above is oxygen contained in the atmosphere that enters the case 2 when the lid 22 closes the opening 210, as well as oxygen (O ２ 2NiOOH+H ２ O → 2Ni(OH) ２ +1 / 2O ２

[0045] [Coating portions 7A, 7B] As shown in Figure 5, the zinc secondary battery 1 further includes two coating portions 7A, 7B. The coating portion 7A covers the first bonding portion 53. The coating portion 7A can prevent the alkaline electrolyte 4 from coming into contact with the first bonding portion 53. The coating portion 7A covers the opening 5111 of the plating layer 5110. Furthermore, the coating portion 7A covers the metal foreign matter 55. The coating portion 7A has a band shape. The coating portion 7A is made of a material that is resistant to the alkaline electrolyte 4. Examples of the coating portion 7A include insulating tape and insulating adhesive.

[0046] The covering portion 7B covers the second bonding portion 63. The covering portion 7B can prevent the alkaline electrolyte 4 from coming into contact with the second bonding portion 63. The covering portion 7B covers the opening 6111 of the plating layer 6110. Furthermore, the covering portion 7B covers the metallic foreign matter 65. The covering portion 7B has a band shape. The covering portion 7B is made of a material that is resistant to the alkaline electrolyte 4. Examples of the covering portion 7B include insulating tape and insulating adhesive.

[0047] The present disclosure includes a zinc secondary battery 1 having an excess volume ratio of 3% or less and an immersion ratio of less than 104%. A zinc secondary battery 1 having an excess volume ratio of 3% or less and an immersion ratio of 104% or more is preferred.

[0048] [Modifications] Each modification will be described below. The above-described [Specific examples of embodiments] and each "modification" can be combined as appropriate.

[0049] [First Modification] Fig. 6 is a cross-sectional view of a first modification of the zinc secondary battery. Fig. 7 is a cross-sectional view of a valve body portion and a valve seat provided in the zinc secondary battery shown in Fig. 6. The first modification of the zinc secondary battery will be described with reference to Figs. 6 and 7.

[0050] 6 , the case 2 provided in the first modified example includes a case body 21, a lid 22, a valve body 28, and a cover 30. An exhaust path 25 is formed in the lid 22. The exhaust path 25 communicates with the internal space of the case 2 and the external space of the case 2. The valve body 28 is attached to the lid 22.

[0051] 7 , the valve body 28 closes the exhaust port 250. The exhaust port 250 is the end of the exhaust path 25 formed in the surface 220 of the lid 22 that contacts the external space. The cover 30 covers the valve body 28. On the other hand, when the valve body 28 opens the exhaust port 250, the cover 30 allows gas in the internal space of the case 2 to flow (be exhausted) into the external space.

[0052] [Details of the lid 22] The lid 22 includes a base portion 26 and a valve seat portion 27. The base portion 26 has a plate shape. The base portion 26 includes a lower surface 261, an upper surface 260, and an inner circumferential surface 262. The lower surface 261 defines the ceiling surface 23. The upper surface 260 corresponds to the surface 220 of the lid 22 that contacts the external space. The inner circumferential surface 262 is connected to the inner edge of the lower surface 261. The inner circumferential surface 262 extends from the inner edge of the lower surface 261.

[0053] The valve seat portion 27 has a cylindrical shape including a second inner circumferential surface 271 and an outer circumferential surface 272. The second inner circumferential surface 271 extends from the edge of the inner circumferential surface 262 that is farthest from the lower surface 261. The second inner circumferential surface 271, together with the inner circumferential surface 262, defines the exhaust path 25. That is, the exhaust path 25 is defined by the inner circumferential surface 262 and the second inner circumferential surface 271. The second inner circumferential surface 271 is flush with the inner circumferential surface 262 in the depth direction DD. The outer circumferential surface 272 is located radially outward of the second inner circumferential surface 271. The valve seat portion 27 includes an upper edge 273. The upper edge 273 is the edge farthest from the lower surface 261 in the depth direction DD. The upper edge 273 defines the exhaust port 250. The liquid level 41 of the alkaline electrolyte 4 is located below the exhaust path 25. The valve seat 27 is hard and may be made of a resin or a metal.

[0054] [Details of Valve Body 28] The valve body 28 includes a first portion 281 and a second portion 282. The first portion 281 has a cylindrical shape that contacts at least an upper end portion 2721 of the outer circumferential surface 272 over the entire circumferential direction. In this modification, the first portion 281 contacts the entire outer circumferential surface 272 (including the upper end portion 2721 and the intermediate portion 2722). The intermediate portion 2722 is located in the middle of the outer circumferential surface 272 in the depth direction DD.

[0055] The second portion 282 faces the exhaust port 250. The second portion 282 is located above the exhaust port 250. The second portion 282 may be separated from the upper edge 273 or may be in contact with the upper edge 273. The second portion 282 closes the second opening 280. The second opening 280 is defined by an edge 2821 of the first portion 281 that is far from the lower surface 261. The second portion 282 is formed integrally with the first portion 281. An example of a material for the valve body portion 28 is rubber. Note that the second portion 282 may be formed separately from the first portion 281, and the first portion 281 may be made of resin or metal, and the second portion 282 may be made of rubber.

[0056] [Deformation of First Portion 281] The first portion 281 is elastically deformable outward based on the pressure in the internal space. In the first modified example, when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the first portion 281 elastically deforms outward, forming a gap between the outer circumferential surface 272 and the first portion 281, thereby opening the exhaust port 250. In other words, in the first modified example, when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the valve body portion 28 elastically deforms, causing the valve body portion 28 to open the exhaust port 250.

[0057] The above-mentioned pressure (1 kPa or more and 40 kPa or less) is sometimes referred to as the operating pressure of the valve body portion 28. The operating pressure is 40 kPa or less, and may be 30 kPa or less, 20 kPa or less, or 10 kPa or less. If the operating pressure is equal to or less than the above-mentioned upper limit, oxygen in the internal space, which is at a relatively low pressure, is exhausted to the external space through the exhaust port 250.

[0058] The operating pressure is 1 kPa or more, or may be 3 kPa or more, or 5 kPa or more. If the operating pressure is equal to or higher than the above-mentioned lower limit, the valve body 28 can be prevented from accidentally opening the exhaust port 250.

[0059] As described above, the operating pressure is 1 kPa to 40 kPa, or may be 3 kPa to 30 kPa, 3 kPa to 20 kPa, or 5 kPa to 10 kPa. If the operating pressure is within the above range, oxygen in the relatively low-pressure internal space is exhausted to the external space through the exhaust port 250, while preventing the valve body 28 from accidentally opening the exhaust port 250. The operating pressure of the valve body 28 is adjusted appropriately by at least one of the material and thickness of the valve body 28.

[0060] [Liquid Level Distance L5] The liquid level distance L5 is 15 mm or more. The liquid level distance L5 is the distance from the exhaust port 250 to the liquid level 41 of the alkaline electrolyte 4 in the depth direction DD of the alkaline electrolyte 4. If the liquid level distance L5 is equal to or greater than the above-mentioned lower limit, the alkaline electrolyte 4 is less likely to leak into the external space through the exhaust port 250. The liquid level distance L5 may be 20 mm or more. The liquid level distance L5 is equal to or less than 50 mm, may be equal to or less than 40 mm, or may be equal to or less than 30 mm. If the liquid level distance L5 is equal to or less than the above-mentioned upper limit, the excess volume ratio can be easily set within a desired (low) range, and the immersion ratio can be easily set within a desired (high) range.

[0061] [Effects of the First Modification] When the zinc secondary battery 1 is discharged, oxygen is generated by a side reaction in the positive electrode plate 31. If oxygen remains in the internal space of the case 2, the oxygen dissolves in the alkaline electrolyte 4, which results in a shortened life of the zinc secondary battery 1.

[0062] However, in the zinc secondary battery of the first modification, when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the valve body portion 28 opens the exhaust port 250, and oxygen in the internal space is exhausted to the external space through the exhaust port 250 before an excessive amount of oxygen accumulates in the internal space. Therefore, the zinc contained in the negative electrode plate 32 is less likely to oxidize. As a result, the life of the zinc secondary battery 1 can be extended.

[0063] On the other hand, when the operating pressure is low as described above, there is an aspect that the alkaline electrolyte 4 is likely to leak into the external space through the exhaust port 250. However, in the first modified example, the liquid level distance L5 is long, at 15 mm or more, so the alkaline electrolyte 4 is less likely to leak into the external space through the exhaust port 250.

[0064] As a result, in the first variant, oxygen in the internal space is exhausted to the external space through the exhaust port 250 before it stagnates in the internal space of the case 2, while the alkaline electrolyte 4 is less likely to leak into the external space through the exhaust port 250.

[0065] [Second Modification] In a second modification, the liquid level distance L5 is not limited to 15 mm or more, and may be, for example, less than 15 mm. Meanwhile, the operating pressure of the valve body portion 28 is 1 kPa or more and 40 kPa or less.

[0066] 8 is a cross-sectional view of the valve seat and valve body portion provided in the second modified zinc secondary battery. The lid 22 and valve body portion 28 included in the second modified zinc secondary battery will be described with reference to FIG.

[0067] The base portion 26 of the lid 22 includes a third portion 263, a fourth portion 264, and a fifth portion 265. The third portion 263 is located radially outwardly away from the valve seat portion 27. The third portion 263 is aligned along the horizontal plane S. The fourth portion 264 is continuous with the lower end of the valve seat portion 27. The fourth portion 264 is located below the third portion 263. The fourth portion 264 is aligned along the horizontal plane S. The fourth portion 264 has a cylindrical shape. The fifth portion 265 connects the inner edge of the third portion 263 and the outer edge of the fourth portion 264. In the second modified example, the liquid level distance L5 is less than 15 mm and may be 10 mm or less. The lower limit of the liquid level distance L5 is not limited.

[0068] The valve body portion 28 has the same configuration as the valve body portion 28 in the first modified example. Therefore, the operating pressure of the valve body portion 28 in the second modified example is 1 kPa or more and 40 kPa or less.

[0069] [Third Modification] In a third modification, the operating pressure of the valve body portion 28 is not limited and may be, for example, greater than 40 kPa. However, as shown in Fig. 7, the liquid level distance L5 is 15 mm or greater.

[0070] [Fourth Modification] In the fourth modification, the configurations of the valve body portion 28 and the valve seat portion 27 are not limited to the configurations exemplified in the first to third modifications, and it is sufficient that the valve body portion 28 and the valve seat portion 27 are configured so that, at least, when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the first portion 281 elastically deforms outward and the exhaust port 250 opens.

[0071] [Other Modifications] The housing 34 may encase each of the plurality of negative electrode plates 32. The housing 34 may encase each of the positive electrode plates 31 and the negative electrode plates 32. The zinc secondary battery 1 may include either one of the covering portion 7A and the covering portion 7B.

[0072] Hereinafter, the zinc secondary battery 1 of the present disclosure will be described in more detail with reference to examples and comparative examples.

[0073] Example 1 A positive electrode plate 31, a first tab lead 52, a negative electrode plate 32, a second tab lead 62, a separator 33, a container 34, a case 2, and an alkaline electrolyte 4 shown below were prepared.

[0074] Positive electrode plate 31: A nickel foam whose pores were filled with a positive electrode paste containing nickel hydroxide and a binder and then dried (an uncoated portion near one edge of the nickel foam where the positive electrode paste was not applied existed). First tab lead 52: The uncoated portion of the nickel foam constituting the positive electrode plate 31 was compressed with a roll press to form a tab, and a tab lead (made of pure nickel, thickness: 100 μm) was ultrasonically welded to this tab to extend it. Negative electrode plate 32: 100 parts by mass of ZnO powder (average particle size D50: 0.2 μm), 5.3 parts by mass of metal Zn powder (average particle size D50: 100 μm), and 1.2 parts by mass of polytetrafluoroethylene were blended and kneaded with propylene glycol. The resulting mixture was rolled with a roll press to obtain a negative electrode active material sheet. The negative electrode active material sheet was pressure-bonded to a tin-plated copper expand metal to obtain the negative electrode plate 32. Second tab lead 62: A tab lead (made of copper, thickness: 100 μm) connected to an uncoated portion of the copper expanded metal by ultrasonic welding. Separator 33: A hydroxide ion conductive separator having gas impermeability, thickness: 20 μm, formed by hydrothermally precipitating Ni-Al-Ti-LDH (layered double hydroxide) within the pores and on the surface of a polyethylene microporous membrane and then roll-pressing the precipitated layer, thickness: 20 μm. Container 34: A polypropylene nonwoven fabric (impregnated sheet 341), thickness: 100 μm. Case 2: Made of modified polyphenylene ether resin, internal dimensions: a length in the thickness direction (TD) of 24 mm, a length in the depth direction (DD) of 159 mm, and a length in the direction perpendicular to the thickness direction (TD) and the depth direction (DD) of 195 mm. Alkaline electrolyte 4: A 6.0 mol / L aqueous NaOH solution in which 0.4 mol / L ZnO has been dissolved.

[0075] The positive electrode plate 31 was housed in a housing 34. Specifically, the positive electrode plate 31 was housed in a closed space inside the housing 34 made of the above-described impregnated sheet 341. A plurality of positive electrode structures 315 were fabricated, each including the housing 34 and the positive electrode plate 31. A plurality of negative electrode structures 325 were fabricated, each including the separator 33 and the negative electrode plate 32, by encasing the negative electrode plate 32 in a separator 33. A plurality of positive electrode structures 315 and a plurality of negative electrode structures 325 were stacked alternately. In this way, an electrode stack 3 was fabricated. The length L3 from the lower end 36 to the upper end 35 of the electrode stack 3 was 139.1 mm.

[0076] The stacked portions 521 of the multiple first tab leads 52 were joined to the lower ends 511 of the first terminals 51 by laser welding to form the first joint portions 53. The first joint portions 53 were covered with a covering portion 7A made of adhesive tape. The stacked portions 621 of the multiple second tab leads 62 were joined to the lower ends 611 of the second terminals 61 by laser welding to form the second joint portions 63. The second joint portions 63 were covered with a covering portion 7B made of adhesive tape.

[0077] The above-described electrode laminate 3 was placed in the case body 21, and the alkaline electrolyte 4 was poured in to impregnate the electrode laminate 3, and the opening 210 was closed with the lid 22. As shown in Fig. 8 , the lid 22 included a valve seat portion 27. A valve body portion 28 was provided on the lid 22. In this way, a zinc secondary battery 1 was produced.

[0078] In the zinc secondary battery 1 of Example 1, the excess volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface 23 of the lid 22 of the case 2 that forms the upper end of the internal space to the liquid surface 41 of the alkaline electrolyte 4, relative to the first volume V1 of the internal space of the case 2, was 3%. Specifically, when the first volume V1 was 744 cm ３ and the second volume V2 is 22.3 cm ３ It was.

[0079] In the depth direction DD of the alkaline electrolyte 4, the immersion ratio, which is the percentage of the length L4 from the lower end 36 to the liquid level 41 of the alkaline electrolyte 4 relative to the length L3 from the lower end 36 to the upper end 35 of the electrode stack 3, was 109%. The length L4 from the lower end 36 to the liquid level 41 of the alkaline electrolyte 4 was 151.6 mm. The excess volume ratio and the immersion ratio are shown in Table 1. The mass of the alkaline electrolyte 4 was 440 g. The liquid level distance L5 was 10 mm. The operating pressure of the valve body portion 28 was 150 kPa. The liquid level 41 of the alkaline electrolyte 4 was located below the exhaust path 25.

[0080] [Example 2 to Comparative Example 2] Zinc secondary batteries 1 of Example 2 to Comparative Example 2 were fabricated in the same manner as Example 1. However, the excess volume ratio, immersion ratio, liquid surface distance L5, operating pressure, and configuration were changed according to Table 1. The mass of the alkaline electrolyte 4 of Example 2 was 380 g. The mass of the alkaline electrolyte 4 of each of Comparative Examples 1 and 2 was 360 g. Case 2 of each of Examples 4 to 7 employed the configuration depicted in FIG. 7 .

[0081] [Evaluation of Lifespan (Trickle Charge Intermittent Charging Accelerated Test)] The zinc secondary batteries 1 of Example 1 to Comparative Example 2 were fully charged at 65°C, and the number of days until the battery capacity reached 50% or less was measured to evaluate their pass / fail status. Specifically, two zinc secondary batteries 1 were charged at 0.2 C and discharged at 0.1 C to measure the initial discharge capacity. Then, the batteries were charged to 100% SOC at 0.2 C, left in a dormant state for approximately 168 hours (approximately 7 days) at 65°C, and then discharged at 0.1 C to calculate the capacity loss due to self-discharge of the zinc secondary batteries 1. The zinc secondary batteries 1 were then charged to 100% SOC at 0.025 C at 65°C to compensate for the self-discharge capacity loss. The zinc secondary batteries 1 were then left in a dormant state for approximately 168 hours and then intermittent charged three more times, maintaining the high SOC for approximately one month while undergoing intermittent trickle charging. Thereafter, 0.2 C charging and 0.1 C discharging were performed, and the discharge capacity after approximately 29 days was measured. The discharge capacity thus measured was divided by the initial discharge capacity and multiplied by 100 to calculate the discharge capacity retention rate (%). Similarly, the test for approximately 29 days (28 days of rest + 1 day of three chargings) was repeated until the discharge capacity was 50% or less of the initial discharge capacity, and the number of days until 50% was reached was calculated.

[0082] When converted to the 10°C double rule, a rating of A was given for 11 years or more at 25°C. When converted to the 10°C double rule, a rating of B+ was given for 10 years or more but less than 11 years at 25°C. When converted to the 10°C double rule, a rating of B was given for 9 years or more but less than 10 years at 25°C. When converted to the 10°C double rule, a rating of C was given for less than 9 years at 25°C. The results are shown in Table 1.

[0083] [Evaluation of Leakage of Alkaline Electrolyte 4] The battery was stored (left to stand) in a 65°C environment for one month in the fully charged state described above. Leakage of the alkaline electrolyte 4 was evaluated based on the following criteria. When the alkaline electrolyte 4 did not leak from the case 2, it was evaluated as A. When the alkaline electrolyte 4 leaked from the case 2, it was evaluated as B. The results are shown in Table 1.

[0084] [Results] Example 1 is compared with Comparative Example 1. In Example 1, the excess volume is 3% or less and the immersion rate is 104% or more. The life of Example 1 was longer than that of Comparative Example 1, which had an excess volume of 10% (more than 3% and also more than 8%) and an immersion rate of 102% (less than 104%).

[0085] Example 3 is compared with Example 4. In Example 4, the liquid level distance L5 is 15 mm or more. Compared to Example 3, in which the liquid level distance L5 is less than 15 mm, in Example 4, the alkaline electrolyte was less likely to leak.

[0086] Example 5 is compared with Example 6. In Example 5, the operating pressure is 40 kPa or less. The life of Example 5 was longer than that of Example 6, in which the operating pressure exceeded 40 kPa.

[0087]

[0088] Other aspects of the present disclosure are described below. [1] A zinc secondary battery comprising: an electrode stack; a case that houses the electrode stack; an alkaline electrolyte housed in the case and in which the entire electrode stack is immersed; and a container made of an impregnated sheet that can be impregnated with the alkaline electrolyte and having an internal closed space, wherein the electrode stack comprises: a positive electrode plate including a positive electrode active material layer; a negative electrode plate facing the positive electrode plate and spaced apart in a thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound; and a separator that separates the positive electrode plate and the negative electrode plate and is capable of conducting hydroxide ions, wherein at least one of the positive electrode plate and the negative electrode plate is housed in the closed space of the container.

[0089] [2] An electrode stack comprising: an electrode stack; a case that accommodates the electrode stack; and an alkaline electrolyte that is accommodated in the case and in which the entire electrode stack is immersed, wherein the electrode stack comprises: a positive electrode plate including a positive electrode active material layer; a negative electrode plate facing the positive electrode plate and positioned apart in a thickness direction of the positive electrode plate, the negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound; and a separator that separates the positive electrode plate and the negative electrode plate and is capable of conducting hydroxide ions, wherein the case comprises: a case body having an opening at an upper end; and a lid that closes the opening, wherein the zinc secondary battery comprises: a first terminal that penetrates the lid; a first tab lead connected to the positive electrode plate and the first terminal; a first joint portion that joins the first terminal and the first tab lead; a second terminal that penetrates the lid and positioned apart from the first terminal; and a second tab lead connected to the negative electrode plate and the second terminal. A zinc secondary battery comprising: a second joint portion that joins the second terminal and the second tab lead; and a covering portion that covers at least one of the first joint portion and the second joint portion, the covering portion being capable of preventing the alkaline electrolyte from coming into contact with the joint portion.

[0090] [3] The zinc secondary battery described in [1], wherein the case includes: a case body having an opening at the top end; a lid that closes the opening, the lid having an exhaust path that connects the internal space of the case to the external space of the case; and a valve body portion that is attached to the lid and closes the exhaust port, which is the end of the exhaust path formed on the surface of the lid that contacts the external space; and the valve body portion opens the exhaust port when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space.

[0091] [4] The case includes: a case body having an opening at an upper end; a lid that closes the opening, the lid having an exhaust path formed therein that communicates with the internal space of the case and the external space of the case; and a valve body portion that is attached to the lid and closes the exhaust port, which is an end of the exhaust path formed in the surface of the lid that contacts the external space; the lid includes: a base portion that is plate-shaped and includes a lower surface that defines the ceiling surface and an inner circumferential surface connected to an inner edge of the lower surface; a valve seat portion that is tubular in shape and includes a second inner circumferential surface that extends from an edge of the inner circumferential surface that is far from the lower surface and that defines the exhaust path together with the inner circumferential surface, and an outer circumferential surface located outside the second inner circumferential surface, and includes an upper edge that defines the exhaust port; and the valve body portion includes: a first portion that has a cylindrical shape and is in contact with at least an upper end of the outer circumferential surface over the entire circumferential direction; and a second portion that faces the exhaust port and closes a second opening that is defined by the edge of the first portion that is far from the lower surface. The zinc secondary battery of [1], wherein the first part is elastically deformable outward based on the pressure in the internal space, and when the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the first part elastically deforms outward, forming a gap between the outer peripheral surface and the first part, thereby opening the exhaust port.

[0092] [5] The case includes: a case body having an opening at an upper end; a lid that closes the opening, the lid having an exhaust path formed therein that communicates with the internal space of the case and the external space of the case; and a valve body portion that is attached to the lid and closes the exhaust port, which is an end of the exhaust path formed in the surface of the lid that contacts the external space; the lid includes: a base portion that is plate-shaped and includes a lower surface that defines the ceiling surface and an inner circumferential surface connected to an inner edge of the lower surface; and a valve seat portion that is tubular in shape and includes a second inner circumferential surface that extends from an edge of the inner circumferential surface that is far from the lower surface and that defines the exhaust path together with the inner circumferential surface, and an outer circumferential surface that is located outside the second inner circumferential surface, and includes an upper edge that defines the exhaust port; and the valve body portion includes: a first portion that has a cylindrical shape and is in contact with at least an upper end of the outer circumferential surface over the entire circumferential direction; and a second portion that faces the exhaust port and closes a second opening that is defined by the edge of the first portion that is far from the lower surface. The zinc secondary battery according to [1], wherein the first portion is elastically deformable outward based on the pressure in the internal space, and a liquid level distance L5, which is the distance from the exhaust port to the liquid level of the alkaline electrolyte in the depth direction of the alkaline electrolyte, is 15 mm or more.

[0093] [6] The zinc secondary battery according to [1], wherein the liquid level is located below the exhaust path.

[0094] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present disclosure is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0095] REFERENCE SIGNS LIST 1 Zinc secondary battery, 2 Case, 3 Electrode laminate, 4 Alkaline electrolyte, 7A Covering portion, 7B Covering portion, 21 Case body, 22 Lid, 23 Ceiling surface, 25 Exhaust path, 26 Base portion, 27 Valve seat portion, 28 Valve body portion, 30 Cover portion, 31 Positive electrode plate, 32 Negative electrode plate, 33 Separator, 34 Container, 35 Upper end, 36 Lower end, 41 Liquid level, 51 First terminal, 52 First tab lead, 53 First bonding portion, 55 Metal foreign matter, 61 Second terminal, 62 Second tab lead, 63 Second bonding portion, 65 Metal foreign matter, 210 Opening, 211 Bottom wall, 212, 213, 214, 215 Side wall, 220 Surface, 221 First sealing material, 222 Second sealing material, 250 Exhaust port, 260 Upper surface, 261 Lower surface, 262 Inner peripheral surface, 263 Third portion, 264 Fourth portion, 265 Fifth portion, 271 Second inner peripheral surface, 272 Outer peripheral surface, 273 Upper edge, 280 Second opening, 281 First portion, 282 Second portion, 311 Positive electrode current collector, 312 Positive electrode active material layer, 315 Positive electrode structure, 321 Negative electrode current collector, 322 Negative electrode active material layer, 325 Negative electrode structure, 341 Impregnated sheet, 511 Lower end, 521 Laminated portion, 611 Lower end, 621 Laminated portion, 2721 Upper end, 2722 Middle portion, 2821 Edge, 5110 Plating layer, 5111 Opening, 6110 Plating layer, 6111 Opening, DD Depth direction, H1, H2 Height, L5 distance, S horizontal plane, TD thickness direction, V1 first volume, V2 second volume.

Claims

1. Electrode stack and, A case for housing the electrode stack, An alkaline electrolyte solution housed in the aforementioned case, in which the entire electrode stack is immersed, Equipped with, The electrode stack is A positive electrode plate containing a positive electrode active material layer, A negative electrode plate facing the positive electrode plate and positioned away from the positive electrode plate in the thickness direction, the negative electrode plate includes a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compounds, The positive electrode plate and the negative electrode plate are separated by a separator capable of conducting hydroxide ions, A zinc secondary battery in which the surplus volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the liquid level of the alkaline electrolyte, relative to the first volume V1 of the internal space of the case, is 3% or less.

2. In the depth direction of the alkaline electrolyte, the electrode stack includes a lower end and an upper end, The zinc secondary battery according to claim 1, wherein the immersion rate, which is the percentage of the length L4 from the lower end to the liquid surface of the alkaline electrolyte to the length L3 from the lower end to the upper end, is 104% or more.

3. The zinc secondary battery according to claim 2, wherein the immersion rate is 109% or more.

4. Electrode stack and, A case for housing the electrode stack, An alkaline electrolyte solution housed in the aforementioned case, in which the entire electrode stack is immersed, Equipped with, The electrode stack is A positive electrode plate containing a positive electrode active material layer, A negative electrode plate facing the positive electrode plate and positioned away from the positive electrode plate in the thickness direction, the negative electrode plate includes a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compounds, The positive electrode plate and the negative electrode plate are separated by a separator capable of conducting hydroxide ions, The surplus volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the liquid surface of the alkaline electrolyte, relative to the first volume V1 of the internal space of the case, is 8% or less. The container is further composed of an impregnating sheet that can be impregnated with the aforementioned alkaline electrolyte, and has a closed space inside, A zinc secondary battery in which at least one electrode plate of the positive electrode plate and the negative electrode plate is housed in the closed space of the housing.

5. Electrode stack and, A case for housing the electrode stack, An alkaline electrolyte solution housed in the aforementioned case, in which the entire electrode stack is immersed, A zinc secondary battery comprising, The electrode stack is A positive electrode plate containing a positive electrode active material layer, A negative electrode plate facing the positive electrode plate and positioned away from the positive electrode plate in the thickness direction, the negative electrode plate includes a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compounds, The positive electrode plate and the negative electrode plate are separated by a separator capable of conducting hydroxide ions, The surplus volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the liquid surface of the alkaline electrolyte, relative to the first volume V1 of the internal space of the case, is 8% or less. The aforementioned case is, A case body having an opening at the top end, A lid that closes the aforementioned opening, The aforementioned zinc secondary battery is A first terminal that penetrates the aforementioned cover, The positive electrode plate and the first tab lead connected to the first terminal, A first joining portion that joins the first terminal and the first tab lead, A second terminal that penetrates the cover and is located away from the first terminal, The negative electrode plate and the second tab lead connected to the second terminal, A second joining portion that joins the second terminal and the second tab lead, A covering portion that covers at least one of the first and second joining portions, the covering portion which can suppress the alkaline electrolyte from coming into contact with the joining portion, A zinc secondary battery equipped with the following features.

6. Electrode stack and, A case for housing the electrode stack, An alkaline electrolyte solution housed in the aforementioned case, in which the entire electrode stack is immersed, Equipped with, The electrode stack is A positive electrode plate containing a positive electrode active material layer, A negative electrode plate facing the positive electrode plate and positioned away from the positive electrode plate in the thickness direction, the negative electrode plate includes a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compounds, The positive electrode plate and the negative electrode plate are separated by a separator capable of conducting hydroxide ions, The surplus volume ratio, which is the percentage of the second volume V2 of the space from the ceiling surface of the case that forms the upper end of the internal space to the liquid surface of the alkaline electrolyte, relative to the first volume V1 of the internal space of the case, is 8% or less. The aforementioned case is, A case body having an opening at the top end, A lid that closes the opening, the lid having an exhaust passage that communicates with the internal space of the case and the external space of the case, It includes a valve body attached to the lid and forming on the surface of the lid that is in contact with the external space, which closes the exhaust port, which is the end of the exhaust passage, The aforementioned lid is A base portion having a plate shape, including a lower surface that defines the ceiling surface, and an inner circumferential surface connected to the inner edge of the lower surface, The valve seat portion includes a cylindrical shape having a second inner circumferential surface extending from the edge furthest from the lower surface and defining the exhaust passage together with the inner circumferential surface, and an outer circumferential surface located outside the second inner circumferential surface, and an upper edge defining the exhaust port, The valve body portion is A first part having a cylindrical shape that contacts at least the upper end of the outer circumferential surface over the entire circumferential area, It includes a second part that faces the exhaust port and closes a second opening defined in the first part by the edge furthest from the lower surface, The first part is elastically deformable outward based on the pressure in the internal space, When the pressure in the internal space becomes 1 kPa or more and 40 kPa or less higher than the pressure in the external space, the first part elastically deforms outward, forming a gap between the outer surface and the first part, thereby opening the exhaust port. A zinc secondary battery in which the liquid level distance L5, which is the distance from the exhaust port to the liquid surface of the alkaline electrolyte in the depth direction of the alkaline electrolyte, is 15 mm or more.

7. The zinc secondary battery according to claim 6, wherein the liquid level is located below the exhaust passage.

8. The zinc secondary battery according to any one of claims 1 to 7, wherein the alkaline electrolyte contains sodium hydroxide.