Zinc secondary battery

Abstract

Provided is an upper tab current collection–type zinc secondary battery that, despite employing a simple terminal that can be produced by heading, can effectively delay liquid leakage from a terminal sealing structure caused by creep. This zinc secondary battery comprises: an upper tab current collection–type laminated cell; a battery case body that accommodates the laminated cell such that each battery component thereof has a vertical orientation; a lid that closes an upper opening of the battery case body; an electrode terminal that passes through the lid; and a liquid leakage–suppressing current collection structure that suppresses liquid leakage from the electrode terminal. The current collection structure comprises: a stepped hole that has at least three steps; two O-rings; the electrode terminal; an upper current collection plate; the laminated cell, which is suspended from a bent part of the current collection plate; and a protrusion that is provided to a back surface of the lid. The ratio b / a of the distance b between the center axis A1 of the electrode terminal and the center axis A3 of the protrusion at the position farthest from the electrode terminal in the X direction to the distance a between center axis A1 and the center axis A2 of the joint between the bent part and a tab lead is at least 0.85.

Description

[Technical Field]

[0001] The present invention relates to a zinc secondary battery. [Background technology]

[0002] Zinc secondary batteries are known that include stacked cells with an upper tab current collection system in which tab leads extend from the top. For example, Patent Document 1 (WO2021 / 193436) discloses a zinc secondary battery that includes a stack including a positive electrode plate and a negative electrode plate, a positive electrode current collector tab connected to the positive electrode current collector and protruding upward from the stack, and a negative electrode current collector tab connected to the negative electrode current collector and protruding upward from the stack. It is believed that by having the positive electrode current collector tab and the negative electrode current collector tab protruding in the same direction from the stack in this way, it is possible to reduce the number of locations where measures to prevent electrical short circuits between the positive electrode current collector and the negative electrode current collector are required.

[0003] Meanwhile, methods have been proposed to strengthen the seal between the lid body and the electrode terminals to prevent electrolyte leakage from the terminals of zinc secondary batteries. For example, Patent Document 2 (WO2021 / 193409) discloses a secondary battery comprising a stack including positive and negative electrode plates, a case housing the stack, and a lid covering the opening of the case. The lid comprises a lid body, a terminal penetrating the lid body, a first O-ring sandwiched between the lid body and the terminal and generating a repulsive force in a first direction, and a second O-ring sandwiched between the lid body and the terminal and generating a repulsive force in a second direction. A first imaginary plane extending from the first O-ring in the first direction and a second imaginary plane extending from the second O-ring in the second direction do not coincide with each other. This prevents the repulsive forces generated by the first O-ring and the second O-ring from being applied to the lid body in an overlapping manner. This reduces the stress applied to the lid body, reduces deformation of the lid body, and strengthens the seal between the lid body and the terminal.

[0004] In zinc secondary batteries, such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc precipitates from the negative electrode in the form of dendrites during charging, penetrates the pores of separators such as nonwoven fabrics, and reaches the positive electrode, resulting in a short circuit. Such short circuits caused by zinc dendrites shorten the battery's lifespan after repeated charge and discharge. To address this issue, batteries have been proposed that include a layered double hydroxide (LDH) separator that selectively allows hydroxide ions to pass through while preventing the penetration of zinc dendrites (see, for example, Patent Documents 1 and 2, Patent Document 3 (WO2016 / 076047), and Patent Document 4 (WO2019 / 124270)). Furthermore, Patent Document 5 (WO2019 / 069760) and Patent Document 6 (WO2019 / 077953) propose a zinc secondary battery configured such that the entire negative electrode active material layer is covered or wrapped with a liquid-retaining member and an LDH separator, and the positive electrode active material layer is covered or wrapped with a liquid-retaining member. A nonwoven fabric is used as the liquid-retaining member. This configuration is said to eliminate the need for a complicated sealing joint between the LDH separator and the battery container, and to enable extremely simple and highly productive production of zinc secondary batteries (particularly stacked batteries) capable of preventing zinc dendrite extension.

[0005] Furthermore, although they cannot be called LDHs, LDH-like compounds are known as hydroxides and / or oxides with a layered crystal structure similar to LDHs, and they exhibit hydroxide ion conductive properties similar enough to be collectively referred to as hydroxide ion-conducting layered compounds together with LDHs (see, for example, Patent Documents 1 and 2). Specifically, Patent Document 7 (WO 2020 / 255856) discloses a hydroxide ion-conducting separator comprising a porous substrate and a layered double hydroxide (LDH)-like compound that plugs the pores of the porous substrate, wherein the LDH-like compound is a hydroxide and / or oxide with a layered crystal structure that contains Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al. Patent Document 8 (WO2021 / 229916) discloses an LDH separator using an LDH-like compound containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) an additional element M, which is at least one selected from the group consisting of In, Bi, Ca, Sr, and Ba. Furthermore, Patent Document 9 (WO2021 / 229917) discloses an LDH separator containing a mixture of an LDH-like compound and In(OH)3, in which the LDH-like compound is a hydroxide and / or oxide having a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In. The separators disclosed in Patent Documents 7 to 9 are said to have superior alkali resistance compared to conventional LDH separators and to be able to more effectively suppress short circuits caused by zinc dendrites. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2021 / 193436 [Patent Document 2] WO2021 / 193409 [Patent Document 3] WO2016 / 076047 [Patent Document 4] WO2019 / 124270 [Patent Document 5] WO2019 / 069760 [Patent Document 6] WO2019 / 077953 [Patent Document 7] WO2020 / 255856 [Patent Document 8] WO2021 / 229916 [Patent Document 9] WO2021 / 229917 Summary of the Invention

[0007] A phenomenon known as creep (hereinafter referred to as creep) is known in alkaline batteries. Creep occurs when alkaline components in the electrolyte creep up the surface of the electrode terminal and leak out of the battery container. Therefore, it is desirable to suppress leakage due to creep. Patent Document 2 (WO2021 / 193409) proposes a structure for suppressing leakage, which includes a lid body, a terminal penetrating the lid body, and a first O-ring and a second O-ring sandwiched between the lid body and the terminal. However, because this terminal has a complex shape, its manufacture requires many steps, resulting in high manufacturing costs. Furthermore, suppressing leakage is not easy in zinc secondary batteries with an upper tab current collection system in which a tab lead extends from the top, as shown in Patent Document 1 (WO2021 / 193436). That is, as in the zinc secondary battery 110 shown in FIG. 17 , a stacked cell 112 employing an upper tab current collection system is configured such that the stacked cell 112 is suspended from a positive electrode tab lead 122p and a negative electrode tab lead 122n, which are joined to a positive electrode upper current collector 130p and a negative electrode upper current collector 130n, respectively. Therefore, as shown in FIG. 18 , the weight of the stacked cell 112 deforms components such as the top cover 116, causing the positive electrode upper current collector 130p and the negative electrode upper current collector 130n to tilt downward toward the center of the battery. As a result, as shown in FIG. 19 , the O-rings 126 and 128, which are sealing members, are insufficiently compressed at the outer portions (dotted line portions) of the positive electrode terminal 118p or the negative electrode terminal 118n, respectively, reducing the liquid-tightness of those portions. As a result, leakage is likely to occur from the insufficiently compressed portions.

[0008] The inventors have now discovered that in a terminal sealing structure for a zinc secondary battery using an upper tab current collection method, which uses two O-rings, by arranging the joint between the electrode terminal and the tab lead of the upper current collector plate, and the convex portion that provides a fulcrum on the back surface of the upper cover so that they satisfy a predetermined positional relationship, it is possible to effectively delay leakage due to creep from the terminal sealing structure, while using a simple terminal that can be manufactured by pressing.

[0009] Therefore, the object of the present invention is to provide a zinc secondary battery with an upper tab current collection system that employs simple terminals that can be manufactured by pressing, while effectively delaying leakage due to creep from the terminal sealing structure.

[0010] According to the present invention, the following aspects are provided. [Aspect 1] a stacked cell having battery components of an upper tab current collection type zinc secondary battery with tab leads extending from the top; a box-shaped battery case body in which the stacked cells are housed so that each of the battery components is oriented vertically; a long plate-shaped top cover that closes an upper opening of the battery case body; an electrode terminal that penetrates the upper cover and protrudes to the outside; a leakage suppression current collecting structure that suppresses leakage from the electrode terminal; A zinc secondary battery comprising: The liquid leakage suppressing current collecting structure is - stepped holes as through holes having at least three stages, each having a large diameter hole, a medium diameter hole, and a small diameter hole in this order from the front surface to the back surface of the upper cover; a first O-ring placed in a step formed by the large diameter hole and the medium diameter hole; a second O-ring placed in the step formed by the medium diameter hole and the small diameter hole; - the electrode terminal is inserted into the stepped hole and fits liquid-tightly with the stepped hole via the first O-ring and the second O-ring, the electrode terminal comprising: an external terminal portion protruding from an upper surface of the top cover; a flange-shaped large diameter portion in surface contact with the upper surface of the top cover; a medium diameter portion having a diameter that fits into the medium diameter hole; and a small diameter portion having a diameter that fits into the small diameter hole; an upper current collecting plate connected to a lower end of the electrode terminal, the upper current collecting plate including: a current collecting plate body arranged parallel to the upper cover; and a bent portion bent and extending vertically downward from a position of the current collecting plate body closer to the center of the battery than the electrode terminal; - the laminated cell, the tab lead being joined to the bent portion and suspended from the bent portion; - at least one convex portion provided on the rear surface of the upper cover at a position outside the electrode terminal, extending in a short direction of the upper cover, and in surface contact with the current collecting plate body to provide a fulcrum; Equipped with a zinc secondary battery in which, when the longitudinal direction of the top cover that is a direction from the center of the battery outward is defined as the X direction and the short side direction of the top cover is defined as the Y direction and the leakage suppression current collecting structure is viewed in cross section in the Y direction, with respect to a central axis A1 of the electrode terminal, a central axis A2 in the X direction of a joint portion between the bent portion and the tab lead, and a central axis A3 of the convex portion that is located at a position farthest from the electrode terminal in the X direction, the ratio b / a of the distance b between the central axis A1 and the central axis A3 to the distance a between the central axis A1 and the central axis A2 is 0.85 or more. [Aspect 2] 2. The zinc secondary battery according to aspect 1, wherein the ratio b / a is 0.90 to 1.50. [Aspect 3] 3. The zinc secondary battery according to aspect 1 or 2, wherein the distance a between the central axis A1 and the central axis A2 is 10 to 40 mm. [Aspect 4] The zinc secondary battery according to any one of aspects 1 to 3, wherein the distance b between the central axis A1 and the central axis A3 is 10 to 40 mm. [Aspect 5] 5. The zinc secondary battery according to any one of aspects 1 to 4, wherein the electrode terminal is a formed product having a three-stage structure composed of the large diameter portion, the medium diameter portion, and the small diameter portion. [Aspect 6] The zinc secondary battery according to any one of aspects 1 to 5, wherein the surfaces of the electrode terminal facing the first O-ring, the second O-ring, and the stepped hole have an arithmetic mean roughness Ra of 0.2 to 1.0 μm. [Aspect 7] The laminated cell is a plurality of positive electrode plates each including a positive electrode active material layer and a positive electrode current collector; a plurality of positive electrode tab leads extending from each end of the positive electrode plate; a plurality of negative electrode plates each including a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a negative electrode current collector; a plurality of negative electrode tab leads extending from each end of the negative electrode plate at positions that do not overlap with the positive electrode tab leads; a plurality of hydroxide ion conductive separators that separate the positive electrode plates and the negative electrode plates so as to be capable of conducting hydroxide ions; An electrolyte; The positive electrode plate and the negative electrode plate are alternately stacked with the hydroxide ion conductive separator sandwiched therebetween, The zinc secondary battery according to any one of aspects 1 to 6, wherein the zinc secondary battery has two of the leakage-suppressing current collecting structures positioned opposite each other, and the bent portion of one of the leakage-suppressing current collecting structures is joined to an assembly of the multiple positive electrode tab leads, and the bent portion of the remaining leakage-suppressing current collecting structure is joined to an assembly of the multiple negative electrode tab leads. [Aspect 8] 8. The zinc secondary battery of claim 7, wherein the positive electrode plate and / or the negative electrode plate are covered or encased in the hydroxide ion-conducting separator. [Aspect 9] A zinc secondary battery according to aspect 7 or 8, wherein not only the hydroxide ion conductive separator but also a liquid-retaining member is interposed between the positive electrode plate and the negative electrode plate. [Aspect 10] A zinc secondary battery according to aspect 9, wherein the positive electrode plate and / or the negative electrode plate is covered or enveloped in the liquid retaining member. [Aspect 11] A zinc secondary battery according to any one of aspects 7 to 10, wherein the hydroxide ion-conducting separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound. [Aspect 12] A zinc secondary battery according to aspect 11, wherein the LDH separator further comprises a porous substrate, and the LDH and / or LDH-like compound is composited with the porous substrate in a form where the LDH and / or LDH-like compound is filled in the pores of the porous substrate. [Aspect 13] 13. The zinc secondary battery according to any one of aspects 1 to 12, wherein the zinc secondary battery is a nickel-zinc secondary battery. [Aspect 14] 13. The zinc secondary battery according to any one of aspects 1 to 12, wherein the zinc secondary battery is an air-zinc secondary battery. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of a zinc secondary battery according to the present invention. [Figure 2] FIG. 2 is a diagram schematically showing a cross section of the zinc secondary battery shown in FIG. 1 taken along line AA'. [Figure 3] FIG. 1 is a schematic cross-sectional view showing an example of a leakage-suppressing current collecting structure in a zinc secondary battery according to the present invention. [Figure 4] 10A and 10B are schematic cross-sectional views for explaining the action of forces in an example of a leakage-suppressing current collecting structure. [Figure 5] 5 is a schematic cross-sectional view for explaining the action of force on the electrode terminal of the leakage-preventing current collecting structure shown in FIG. 4 and in the vicinity thereof. FIG. [Figure 6] 5 is a perspective view of the leakage-suppressing current collecting structure shown in FIG. 4, viewed from the rear surface side of the upper cover. [Figure 7] 3 is a schematic cross-sectional view illustrating the definitions of central axes A1, A2, and A3 and distances a and b in the leakage-suppressing current collecting structure. FIG. [Figure 8]FIG. 1 is a perspective view showing an example of a leakage-suppressing current collecting structure used in a zinc secondary battery of the present invention. [Figure 9] FIG. 9 is a perspective view of the leakage-suppressing current collecting structure shown in FIG. 8, viewed from the rear surface side of the top cover. [Figure 10] FIG. 9 is an exploded perspective view of the leakage-preventing current collecting structure shown in FIG. 8. [Figure 11] 9 is a cross-sectional view of the leakage-preventing current collecting structure shown in FIG. 8 taken along the line BB. [Figure 12] FIG. 2 is a perspective view schematically showing an example of a stacked cell of the zinc secondary battery shown in FIG. [Figure 13] FIG. 2 is a cross-sectional view schematically showing an example of a stacked cell of the zinc secondary battery shown in FIG. [Figure 14] FIG. 1 is a conceptual diagram for explaining the mechanism of a creep phenomenon. [Figure 15] FIG. 1 is a cross-sectional view conceptually showing how an electrolyte passes through a minute gap between an electrode terminal with small surface roughness and an O-ring. [Figure 16] 16 is a cross-sectional view conceptually showing how an electrolyte passes through a minute gap between an O-ring and an electrode terminal having a surface roughness greater than that of the electrode terminal shown in FIG. 15. FIG. [Figure 17] FIG. 1 is a schematic cross-sectional view showing an example of a conventional zinc secondary battery. [Figure 18] FIG. 18 is a schematic cross-sectional view showing a state in which the electrode terminal and the upper current collector plate in the conventional zinc secondary battery shown in FIG. 17 are tilted. [Figure 19] FIG. 19 is a schematic cross-sectional view showing an enlarged view of an electrode terminal and its vicinity in the conventional zinc secondary battery in the state shown in FIG. 18. DETAILED DESCRIPTION OF THE INVENTION

[0012] Zinc secondary battery The zinc secondary battery of the present invention is not particularly limited as long as it uses zinc as the negative electrode and an alkaline electrolyte (typically an aqueous alkali metal hydroxide solution). Therefore, it can be a nickel-zinc secondary battery, a silver oxide-zinc secondary battery, a manganese oxide-zinc secondary battery, an air-zinc secondary battery, or any other type of alkaline zinc secondary battery. For example, it is preferable that the positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, thereby forming the zinc secondary battery into a nickel-zinc secondary battery. Alternatively, the positive electrode active material layer may be an air cathode layer, thereby forming the zinc secondary battery into an air-zinc secondary battery.

[0013] 1 to 13 show a zinc secondary battery 10 according to one embodiment of the present invention and its components. As shown in FIGS. 1 and 2, the zinc secondary battery 10 includes a stacked cell 12, a battery case body 14, a top lid 16, electrode terminals 18, and a leakage-suppressing current collecting structure 20. The stacked cell 12 has battery components of a top tab current collecting zinc secondary battery with tab leads 22 extending from the top. The battery case body 14 is box-shaped, and the stacked cell 12 is housed therein with each battery component oriented vertically (i.e., perpendicular to the ground surface). The top lid 16 is a long, plate-like member that closes the top opening of the battery case body 14. As shown in FIGS. 3 and 7, the electrode terminals 18 (i.e., positive terminal 18p and / or negative terminal 18n) penetrate the top lid 16 and protrude to the outside. The leakage-suppressing current collecting structure 20 is a structure for suppressing leakage from the electrode terminal 18, and includes a stepped hole 24, a first O-ring 26, a second O-ring 28, the electrode terminal 18, an upper current collecting plate 30, the stacked cells 12, and at least one convex portion 32. The stepped hole 24 is formed as a through-hole with at least three stages, including a large-diameter hole 24a, a medium-diameter hole 24b, and a small-diameter hole 24c, in that order from the front surface (the outer surface of the battery) to the back surface (the inner surface of the battery) of the top lid 16. The first O-ring 26 is disposed in the step formed by the large-diameter hole 24a and the medium-diameter hole 24b, and the second O-ring 28 is disposed in the step formed by the medium-diameter hole 24b and the small-diameter hole 24c. The electrode terminal 18 includes an external terminal portion 18a protruding from the front surface of the top lid 16, a flange-shaped large-diameter portion 18b in surface contact with the front surface of the top lid 16, a medium-diameter portion 18c having a diameter that fits into the medium-diameter hole 24b, and a small-diameter portion 18d having a diameter that fits into the small-diameter hole 24c. The electrode terminal 18 is inserted into the stepped hole 24 and fits liquid-tightly with the stepped hole 24 via a first O-ring 26 and a second O-ring 28. As shown in FIGS. 6 to 11 , the upper current collector 30 is a current collector connected to the lower end of the electrode terminal 18 and includes a current collector body 30a and a bent portion 30b. The current collector body 30a is disposed parallel to the top lid 16, while the bent portion 30b bends vertically downward and extends from a position on the current collector body 28a closer to the center of the battery than the electrode terminal 18. As shown in FIG. 7, a tab lead 22 is joined to the bent portion 30b, and the stacked cell 12 is suspended from the bent portion 30b.As shown in Figures 6, 7, and 12, the convex portion 32 is provided on the back surface of the top lid 16 at a position outside the electrode terminal 18, extending in the short-side direction of the top lid 16, and is in surface contact with the current collector plate body 30a to provide a fulcrum. Here, as shown in Figures 7 and 11, the longitudinal direction of the top lid 16, which is the direction from the center of the battery toward the outside, is defined as the X direction, and the short-side direction of the top lid 16 is defined as the Y direction. When the leakage suppression current collecting structure 20 is viewed in cross section in the Y direction, with respect to the central axis A1 of the electrode terminal 18, the central axis A2 in the X direction of the joint portion between the bent portion 30b and the tab lead 22, and the central axis A3 of the convex portion 32 located at a position farthest from the electrode terminal 18 in the X direction, the ratio of the distance b between the central axis A1 and the central axis A3 to the distance a between the central axis A1 and the central axis A2 (i.e., b / a) is 0.85 or more. In this way, in the terminal sealing structure of a zinc secondary battery using an upper tab current collection method, which has two O-rings 26, 28 interposed therebetween, by arranging the joint between the electrode terminal 18 and the tab lead 22 of the upper current collecting plate 30, and the convex portion 32 that provides a fulcrum on the back surface of the upper cover 16 so as to satisfy a predetermined positional relationship, leakage due to creep from the terminal sealing structure can be effectively delayed while using a simple terminal that can be manufactured by pressing.

[0014] As mentioned above, creep is a phenomenon in which the electrolyte creeps up the surface of the electrode terminal and leaks out of the battery container. Figure 14 conceptually shows the mechanism of creep when a part of a metal member 19 (which is assumed to be an electrode terminal or an upper current collector plate) is immersed in electrolyte 34 (which is assumed to be a potassium hydroxide aqueous solution). As shown in Figure 14, creep occurs due to the following factors: 1) the interaction of H2O molecules from the surrounding environment with electrons e present in the metal member 19; - is bonded to OH - 2) this OH - in electrolyte 34 +This phenomenon develops as the electrolyte 34 is attracted to the metal member 19. Thus, a component of the electrolyte 34 (KOH) is generated in the area of ​​the metal member 19 where the electrolyte 34 is not present. As a result, this phenomenon is observed as the electrolyte 34 creeping up the metal member 19. Typically, electrolyte leakage due to creep occurs only on the negative electrode side. Therefore, it is desirable to suppress leakage due to creep. In this regard, Patent Document 2 (WO2021 / 193409) discloses a complex terminal structure using two O-rings to suppress leakage, but manufacturing such a terminal requires many steps, resulting in high manufacturing costs. Furthermore, in a zinc secondary battery 110 with a top tab current collection system, such as that shown in Patent Document 1 (WO2021 / 193436) and illustrated in FIG. 17, as shown in FIG. 18, the weight of the stacked cells 112 causes components such as the top cover 116 to deform, causing the positive electrode upper current collector plate 130p and the negative electrode upper current collector plate 130n to tilt downward toward the center of the battery. As a result, as shown in FIG. 19, the O-rings 126 and 128, which are sealing members, are insufficiently compressed in the outer portions (dotted lines in the figure) of the electrode terminals 118 (i.e., the positive electrode terminal 118p or the negative electrode terminal 118n), reducing the liquid-tightness in those areas. As a result, leakage is more likely to occur from the insufficiently compressed areas. These problems are advantageously solved by the zinc secondary battery of the present invention.

[0015] That is, while terminals with complex shapes including recesses, such as those disclosed in Patent Document 2, cannot be manufactured by forging, the electrode terminal 18 employed in the present invention has a simple stepped shape, consisting of an external terminal portion 18a, a large-diameter portion 18b, a medium-diameter portion 18c, and a small-diameter portion 18d, as shown in Figures 3 and 7. For example, a three-step structure without a recess, including the large-diameter portion 18b, the medium-diameter portion 18c, and the small-diameter portion 18d, that fits into the stepped hole 24 of the electrode terminal 18, is particularly suitable for forging. Forging is difficult for stepped structures with four or more steps. The ability to manufacture the electrode terminal 18 by forging reduces manufacturing costs by requiring fewer processes compared to other manufacturing methods, such as cutting and casting. Furthermore, the leakage-suppressing current collecting structure 20 of the present invention is less likely to suffer from a decrease in liquid-tightness due to the weight of stacked cells, as shown in Figures 18 and 19. This is because the leakage-suppressing current collecting structure 20 is designed to be less likely to deform due to the weight of the stacked cells 12. That is, as shown in FIG. 4, in the leakage-suppressing current collecting structure 20, a downward force (in the direction of arrow A) is applied to the bent portion 30b due to the weight of the stacked cells 12. This force is then transmitted to the current collecting plate main body 30a, the electrode terminal 18, and the top cover 16, resulting in a moment in the direction of arrow B centered on the electrode terminal 18. In this case, as shown in FIG. 5, a downward force (in the direction of arrow C) acts to sink the portion of the current collecting plate main body 30a close to the bent portion 30b, while an upward force (in the direction of arrow D) acts to float the portion of the electrode terminal 18 far from the bent portion 30b. At this time, point E, which is the contact point between the top cover 16 and the current collecting plate main body 30a and is located far from the bent portion 30b, functions as a fulcrum, while point F, which is the contact point between the electrode terminal 18 and the stepped hole 24 and is located near the bent portion 30b, also functions as a fulcrum. Thus, a force acts in the direction of increasing the gap between the electrode terminal 18 and the stepped hole 24. However, in the leakage prevention current collecting structure 20 according to the present invention, as shown in Figures 6 and 11, the convex portion 32 is provided on the back surface of the top cover 16 at a position outside the electrode terminal 18, extending in the short direction of the top cover 16, and is in surface contact with the current collecting plate body 30a to provide a fulcrum.The moment (see arrow B) can be minimized by adjusting the relative positional relationship between the electrode terminal 18, the bent portion 30b, the tab lead 22, and the convex portion 32 (located farthest from the electrode terminal 18 in the X direction) so that the ratio (b / a, see FIGS. 7 and 11 ) of the distance b between the central axis A1 and the central axis A3 to the distance a between the central axis A1 and the central axis A2 is 0.85 or greater. That is, by positioning the convex portion 32 located farthest from the electrode terminal 18 in the X direction at a certain distance or more from the bent portion 30b, to which a downward force (in the direction of arrow A) is applied due to the weight of the stacked cells 12, the convex portion 32 can function as a fulcrum for effectively absorbing the force applied to the current collector plate body 30a. In other words, by increasing the distance H shown in FIG. 6 , the entire top cover 16, including the convex portion 32, can absorb the force applied to the fulcrum, thereby minimizing the moment. 5 and the forces applied to fulcrums E and F, the gap between the electrode terminal 18 and the stepped hole 24 is prevented from widening in the lateral direction (the direction of arrow G), thereby preventing a decrease in liquid-tightness. This, combined with the electrode terminal 18 liquid-tightly fitting into the stepped hole 24 via the first O-ring 26 and the second O-ring 28, effectively delays leakage due to creep from the terminal sealing structure.

[0016] As described above, with respect to the central axis A1 of the electrode terminal 18, the central axis A2 in the X direction of the joint portion between the bent portion 30b and the tab lead 22, and the central axis A3 of the convex portion 32 located farthest from the electrode terminal 18 in the X direction, the ratio of the distance b between the central axis A1 and the central axis A3 to the distance a between the central axis A1 and the central axis A2 (i.e., b / a) is 0.85 or more, preferably 0.90 to 1.50, more preferably 1.00 to 1.50, and even more preferably 1.10 to 1.50. The distance a between the central axis A1 and the central axis A2 is preferably 10 to 40 mm, more preferably 10 to 30 mm, and even more preferably 10 to 20 mm. The distance b between the central axis A1 and the central axis A3 is preferably 10 to 40 mm, more preferably 15 to 35 mm, and even more preferably 20 to 30 mm. Within these ranges, leakage due to creep from the terminal sealing structure can be more effectively delayed.

[0017] As shown in FIGS. 1 and 2, a zinc secondary battery 10 includes a stacked cell 12, a battery case body 14, an upper cover 16, electrode terminals 18, and a leakage-suppressing current collecting structure 20.

[0018] The stacked cell 12 has battery components of an upper tab current collection type zinc secondary battery with a tab lead 22 extending from the top. Such a stacked cell 12 can be one in which positive and negative electrode plates are stacked with a separator and / or a liquid-retaining member interposed therebetween, as disclosed in Patent Document 1. Preferred embodiments of the stacked cell 12 will be described later.

[0019] The battery case body 14 is a box-shaped case with an opening at the top, and the stacked cells 12 are housed therein with each battery component oriented vertically (i.e., perpendicular to the ground surface). The top lid 16 is a long, plate-like member that closes the top opening of the battery case body 14. That is, by closing the top opening of the battery case body 14 with the top lid 16, the battery case 13 can be configured as a sealed container. The top lid 16 may have a pressure relief valve for releasing gas. The top lid 16 shown in FIGS. 8, 10, and 11 has a pressure relief valve hole 17 so that a pressure relief valve can be installed. Both the battery case body 14 and the top lid 16 are preferably made of resin. The resin constituting the battery case body 14 and the top lid 16 is preferably a resin resistant to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, ABS resin, or modified polyphenylene ether, and even more preferably an ABS resin or modified polyphenylene ether. The battery case body 14 preferably has inner dimensions of 150 to 200 mm in length, 10 to 50 mm in width, and 100 to 200 mm in height, more preferably 180 to 200 mm in length, 10 to 40 mm in width, and 120 to 180 mm in height. The battery case body 14 preferably has outer dimensions of 150 to 250 mm in length, 10 to 60 mm in width, and 100 to 250 mm in height, more preferably 180 to 220 mm in length, 20 to 40 mm in width, and 130 to 200 mm in height. The top lid 16 preferably has a length of 150 to 250 mm in length, 10 to 60 mm in width, more preferably 180 to 220 mm in length, and 20 to 40 mm in width.

[0020] The top cover 16 includes a stepped hole 24 and at least one convex portion 32 provided on the back surface of the top cover 16 as components that form part of the leakage-suppressing current collecting structure 20. The stepped hole 24 is formed as a through-hole with at least three stages, including a large-diameter hole 24a, a medium-diameter hole 24b, and a small-diameter hole 24c, in that order from the front surface of the top cover 16 (the outer surface of the battery) to the back surface (the inner surface of the battery). The inner diameter of the large-diameter hole 24a is preferably 10 to 30 mm, more preferably 10 to 20 mm. The inner diameter of the medium-diameter hole 24b is preferably 5 to 15 mm, more preferably 5 to 10 mm. The inner diameter of the small-diameter hole 24c is preferably 2 to 15 mm, more preferably 2 to 10 mm. The stepped hole 24 preferably has three stages. 6 and 11, the convex portion 32 is provided on the back surface of the top cover 16 at a position outside the electrode terminals 18, extending in the short direction of the top cover 16, and is in surface contact with the current collector plate body 30a to provide a fulcrum. The thickness of the convex portion 32 is preferably 2 to 15 mm, and more preferably 2 to 10 mm. With this thickness, the convex portion 32 can ensure sufficient strength to withstand the force applied to the fulcrum from the current collector plate body 30a due to the weight of the stacked cells 12.

[0021] The electrode terminal 18 penetrates the top cover 16 and protrudes to the outside. As shown in FIGS. 3 and 7 , the electrode terminal 18 is a component that forms part of the leakage suppression current collecting structure 20 and includes an external terminal portion 18a protruding from the front surface of the top cover 16, a flange-shaped large-diameter portion 18b that is in surface contact with the front surface of the top cover 16, a medium-diameter portion 18c having a diameter that fits into the medium-diameter hole 24b, and a small-diameter portion 18d having a diameter that fits into the small-diameter hole 24c. The electrode terminal 18 only needs to have a shape and size that allows it to be inserted into the stepped hole 24 and to fit liquid-tightly with the stepped hole 24 via the first O-ring 26 and the second O-ring 28. When the electrode terminal 18 is inserted into the stepped hole 24, the first O-ring 26 and the second O-ring 28 are compressed between the electrode terminal 18 and the stepped hole 24, sealing the gap. At the same time, the flange-shaped large diameter portion 18b comes into surface contact (preferably without any gaps) with the front surface of the top cover 16. This ensures the liquid-tightness of the leakage suppression current collecting structure 20. When viewed in a plan view along its central axis, the electrode terminal 18 is preferably configured so that the outer peripheries of the large diameter portion 18b, the medium diameter portion 18c, and the small diameter portion 18d are concentric. The diameter of the external terminal portion 18a is preferably 3 to 10 mm, more preferably 3 to 7 mm. The diameter of the large diameter portion 18b is preferably 10 to 30 mm, more preferably 10 to 20 mm. The diameter of the medium diameter portion 18c is preferably 5 to 15 mm, more preferably 5 to 10 mm. The diameter of the small diameter portion 18d is preferably 2 to 15 mm, more preferably 2 to 10 mm. The electrode terminal 18 may be made of any metal material commonly used for terminals, and is not particularly limited, but may be made of SWCH (cold heading carbon steel), for example. The electrode terminal 18 is preferably a forged product having a three-stage structure consisting of a large diameter portion 18b, a medium diameter portion 18c, and a small diameter portion 18d. As mentioned above, a three-stage structure without a recess, including the large diameter portion 18b, the medium diameter portion 18c, and the small diameter portion 18d, is particularly suitable for forging. This is because a stepped structure with four or more stages is difficult to fabricate by forging. Note that the three-stage structure without a recess refers to the basic structure of the electrode terminal 18, and the term "recess" does not refer to fine grooves or recesses, such as thread grooves, that may be added in an optional additional process.In fact, the electrode terminal 18 (specifically, the external terminal portion 18a) shown in FIGS. 3 and 8 to 11 is given a basic structure by heading, and then a thread groove is formed by rolling.

[0022] The arithmetic mean roughness Ra of the surface of the electrode terminal 18 (particularly the negative electrode terminal 18n) facing the first O-ring 26, the second O-ring 28, and the stepped hole 24 is preferably 0.2 to 1.0 μm, more preferably 0.4 to 1.0 μm, and even more preferably 0.6 to 1.0 μm. This further delays leakage due to creep from the terminal sealing structure. That is, as shown in FIG. 15 , due to the presence of minute irregularities on the surface of the electrode terminal 18, minute gaps inevitably form between the electrode terminal 18 and the O-ring 26 or 28, and electrolyte can pass through these minute gaps. In this regard, in this embodiment, by adjusting (making rougher) the surface roughness of the portion of the electrode terminal 18 (particularly the negative electrode terminal 18n) facing the O-rings 26 and 28 to satisfy the above-mentioned Ra range, the distance that the electrolyte 34 creeps up the surface of the electrode terminal 18 is extended, as shown in FIG. 16 , thereby delaying leakage due to creep. The method for adjusting the surface roughness of the electrode terminal 18 is not particularly limited, and the surface roughness can be changed appropriately by changing the manufacturing method of the electrode terminal 18. The surface roughness may also be increased by subjecting the manufactured electrode terminal 18 to a roughening treatment such as blasting. The surface roughness, i.e., the arithmetic mean roughness Ra, can be measured using a measuring device such as a laser microscope or a stylus-type surface roughness measuring instrument in accordance with JIS B0601 (2001).

[0023] The first O-ring 26 and the second O-ring 28 are sealing members for ensuring liquid-tightness between the electrode terminal 18 and the stepped hole 24. The first O-ring 26 is disposed in the step formed by the large-diameter hole 24a and the medium-diameter hole 24b (i.e., the bottom of the large-diameter hole 24a excluding the medium-diameter hole 24b), while the second O-ring 28 is disposed in the step formed by the medium-diameter hole 24b and the small-diameter hole 24c (i.e., the bottom of the medium-diameter hole 24b excluding the small-diameter hole 24c). As described above, when the electrode terminal 18 is inserted into the stepped hole 24, the first O-ring 26 and the second O-ring 28 are compressed between the electrode terminal 18 and the stepped hole 24, thereby closing the gap. Therefore, both the first O-ring 26 and the second O-ring 28 are disposed so as to contact the electrode terminal 18. The diameter of the first O-ring 26 is preferably 5 to 15 mm, more preferably 8 to 12 mm. The diameter of the second O-ring 28 is preferably 2 to 13 mm, and more preferably 5 to 10 mm. The material of the first O-ring 26 and the second O-ring 28 is not particularly limited, but is preferably made of EPDM (ethylene propylene diene rubber).

[0024] As shown in FIGS. 6 to 11 , the upper current collector plate 30 is a current collector plate connected to the lower end of the electrode terminal 18 and includes a current collector body 30a and a bent portion 30b. The current collector body 30a is disposed parallel to the top cover 16, while the bent portion 30b bends vertically downward from a position closer to the center of the battery than the electrode terminal 18 on the current collector body 28a. As shown in FIGS. 1, 2, and 7 , a tab lead 22 is joined to the bent portion 30b, and the stacked cell 12 is suspended from the bent portion 30b. As shown in FIGS. 6 and 11 , the convex portion 32 is provided on the back surface of the top cover 16 at a position outside the electrode terminal 18, extending in the lateral direction of the top cover 16, and is in surface contact with the current collector body 30a to provide a fulcrum. The thickness of the current collector body 30a is preferably 1 to 5 mm, more preferably 2 to 4 mm. The thickness of the bent portion 30b is preferably 1 to 5 mm, and more preferably 2 to 4 mm. The material of the upper current collector plate 30 is not particularly limited as long as it is a conductive member such as a metal, but is preferably made of SPCC (cold rolled steel plate).

[0025] Stacked Cell 12 and 13 show a preferred embodiment of a stacked cell 12. This stacked cell 12 includes a plurality of positive electrode plates 36, a plurality of positive electrode tab leads 22p extending from each end of the positive electrode plates 36, a plurality of negative electrode plates 38, a plurality of negative electrode tab leads 22n extending from each end of the negative electrode plates 38 at positions that do not overlap the positive electrode tab leads 22p, a plurality of hydroxide ion conductive separators 40, and an electrolyte 34. The positive electrode plates 36 and the negative electrode plates 38 are alternately stacked with the hydroxide ion conductive separators 40 sandwiched between them. That is, the zinc secondary battery 10 preferably includes a plurality of unit cells 11 each having a pair of positive electrode plates 36 and negative electrode plates 38 together with the hydroxide ion conductive separator 40, with the plurality of unit cells 11 forming a multi-layer cell as a whole. This is the configuration of a so-called assembled battery or stacked battery, and is advantageous in that it can provide high voltage and large current. As shown in Figures 1 and 8 to 10, a preferred zinc secondary battery 10 has two leakage-preventing current collecting structures 20 positioned opposite each other, with a group of multiple positive electrode tab leads 22p joined to the bent portion 30b of one leakage-preventing current collecting structure 20, and a group of multiple negative electrode tab leads 22n joined to the bent portion 30b of the other leakage-preventing current collecting structure 20.

[0026] The positive electrode plate 36 includes a positive electrode active material layer 36a. The positive electrode active material constituting the positive electrode active material layer 36a may be selected appropriately from known positive electrode materials depending on the type of zinc secondary battery, and is not particularly limited. For example, in the case of a nickel-zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode. The positive electrode plate 36 further includes a positive electrode current collector (not shown), and a metal positive electrode tab lead 22p is preferably provided extending upward from the positive electrode current collector. A preferred example of the positive electrode current collector is a nickel porous substrate such as a foamed nickel plate. In this case, a positive electrode plate consisting of a positive electrode and a positive electrode current collector can be preferably fabricated by, for example, uniformly applying a paste containing an electrode active material such as nickel hydroxide onto a nickel porous substrate and drying it. At this time, it is also preferable to press the dried positive electrode plate (i.e., the positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve electrode density. The positive electrode plate 36 shown in FIG. 13 includes a positive electrode current collector (e.g., foamed nickel), but this is not shown. This is because, in the case of a nickel-zinc secondary battery, the positive electrode current collector is integrally integrated with the positive electrode active material, making it impossible to depict the positive electrode current collector separately. The positive electrode tab lead 22p may be made of the same material as the positive electrode current collector, or may be made of a different material. If the positive electrode current collector is a porous nickel substrate such as a foamed nickel plate, it can be formed into a tab shape by pressing. Another tab lead may be added to such a tab to extend the positive electrode tab lead 22p. In either case, it is preferable that multiple positive electrode tab leads 22p be joined to the bent portion 30b of the upper current collector plate 30. The positive electrode tab lead 22p and the bent portion 30b may be joined by a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0027] The positive electrode plate 36 may contain at least one additive selected from the group consisting of a silver compound, a manganese compound, and a titanium compound, which can promote the positive electrode reaction of absorbing hydrogen gas generated by the self-discharge reaction. The positive electrode plate 36 may also contain cobalt. The cobalt is preferably contained in the positive electrode plate 36 in the form of cobalt oxyhydroxide. In the positive electrode plate 36, cobalt functions as a conductive additive, thereby contributing to improving the charge / discharge capacity.

[0028] The negative electrode plate 38 includes a negative electrode active material layer 38a. The negative electrode active material constituting the negative electrode active material layer 38a includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds. Zinc may be contained in any form, such as zinc metal, zinc compounds, or zinc alloys, as long as it has electrochemical activity suitable for a negative electrode. Preferred examples of negative electrode materials include zinc oxide, zinc metal, and calcium zincate, with a mixture of zinc metal and zinc oxide being more preferred. The negative electrode active material may be in a gel form or may be mixed with the electrolyte solution 34 to form a negative electrode composite. For example, a gelled negative electrode can be easily obtained by adding an electrolyte solution and a thickener to the negative electrode active material. Examples of thickeners include polyvinyl alcohol, polyacrylate, CMC, and alginic acid. Polyacrylic acid is preferred due to its excellent chemical resistance to strong alkalis.

[0029] The zinc alloy can be a mercury- and lead-free zinc alloy known as a mercury-free zinc alloy. For example, a zinc alloy containing 0.01 to 0.1 mass% indium, 0.005 to 0.02 mass% bismuth, and 0.0035 to 0.015 mass% aluminum is preferred because it suppresses hydrogen gas generation. In particular, indium and bismuth are advantageous in improving discharge performance. The use of a zinc alloy for the negative electrode can improve safety by slowing the rate of self-dissolution in alkaline electrolyte, thereby suppressing hydrogen gas generation.

[0030] The shape of the negative electrode material is not particularly limited, but it is preferably in powder form, which increases the surface area and enables it to withstand large current discharge. In the case of a zinc alloy, the average particle size of the negative electrode material is preferably in the range of 3 to 100 μm in minor axis. Within this range, the large surface area makes it suitable for withstanding large current discharge, and it is also easy to mix uniformly with the electrolyte and gelling agent, making it easy to handle during battery assembly.

[0031] The negative electrode plate 38 further includes a negative electrode current collector 38b. The negative electrode current collector 38b is provided inside and / or on the surface of the negative electrode active material layer 38a. That is, the negative electrode active material layer 38a may be provided on both sides of the negative electrode current collector 38b, or the negative electrode active material layer 38a may be provided on only one side of the negative electrode current collector 38b. The negative electrode current collector 38b preferably further includes a negative electrode tab lead 22n extending upward therefrom. The negative electrode tab lead 22n may be made of the same material as the negative electrode current collector 38b or a different material. The negative electrode tab lead 22n may be extended by connecting another tab lead to the tab. In either case, it is preferable that multiple negative electrode tab leads 22n are connected to the bent portion 30b of the upper current collector 30 (to which the positive electrode tab lead 22p is not connected). The negative electrode tab lead 22n and the bent portion 30b may be joined by a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0032] The negative electrode current collector 38b is preferably a metal plate with multiple (or many) openings from the viewpoint of active material adhesion. Preferred examples of such a negative electrode current collector 38b include expanded metal, punched metal, metal mesh, and combinations thereof. More preferred are copper expanded metal, copper punched metal, and combinations thereof, with copper expanded metal being particularly preferred. In this case, a negative electrode plate consisting of a negative electrode / negative electrode current collector can be preferably produced by, for example, applying a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (e.g., polytetrafluoroethylene particles), to the copper expanded metal. In this case, it is also preferable to press the dried negative electrode plate (i.e., the negative electrode / negative electrode current collector) to prevent the electrode active material from falling off and improve electrode density. The expanded metal is a mesh-like metal plate produced by expanding a metal plate while making staggered cuts using an expanding machine, and then shaping the cuts into a diamond or tortoiseshell pattern. Punched metal, also known as perforated metal, is a metal plate with holes punched into it. Metal mesh is a metal product with a wire mesh structure, and is different from expanded metal and perforated metal.

[0033] The hydroxide ion conductive separator 40 is provided to separate the positive electrode plate 36 and the negative electrode plate 38 in a manner that allows hydroxide ions to be conducted between them. For example, as shown in FIG. 13 , the positive electrode plate 36 and / or the negative electrode plate 38 (preferably the negative electrode plate 38) may be configured to be covered or wrapped with the hydroxide ion conductive separator 40. This eliminates the need for a complicated sealing joint between the hydroxide ion conductive separator 40 and the battery container, making it possible to produce a zinc secondary battery (particularly a stacked battery thereof) that is capable of preventing zinc dendrite extension extremely easily and with high productivity. However, a simple configuration in which the hydroxide ion conductive separator 40 is disposed on one side of the positive electrode plate 36 or the negative electrode plate 38 may also be used.

[0034] The hydroxide ion-conductive separator 40 is not particularly limited as long as it is a separator capable of separating the positive electrode plate 36 and the negative electrode plate 38 in a hydroxide ion-conductive manner. Typically, however, it is a separator containing a hydroxide ion-conductive solid electrolyte and selectively passing hydroxide ions solely by utilizing hydroxide ion conductivity. A preferred hydroxide ion-conductive solid electrolyte is a layered double hydroxide (LDH) and / or an LDH-like compound. Therefore, the hydroxide ion-conductive separator 40 is preferably an LDH separator. As used herein, an "LDH separator" is defined as a separator containing an LDH and / or an LDH-like compound and selectively passing hydroxide ions solely by utilizing the hydroxide ion conductivity of the LDH and / or LDH-like compound. As used herein, an "LDH-like compound" refers to a hydroxide and / or oxide with a layered crystal structure that has hydroxide ion conductivity and may not be considered an LDH, and may be considered an equivalent of an LDH. However, in a broader sense, "LDH" can be interpreted to encompass not only LDH but also LDH-like compounds. The LDH separator is preferably composited with a porous substrate. Therefore, the LDH separator preferably further comprises a porous substrate, and is composited with the porous substrate in a form in which the pores of the porous substrate are filled with LDH and / or LDH-like compounds. That is, in a preferred LDH separator, the pores of the porous substrate are filled with LDH and / or LDH-like compounds so as to exhibit hydroxide ion conductivity and gas impermeability (and therefore function as an LDH separator exhibiting hydroxide ion conductivity). The porous substrate is preferably made of a polymer material, and it is particularly preferred that the LDH and / or LDH-like compounds are incorporated throughout the entire thickness of the porous substrate made of a polymer material. For example, known LDH separators such as those disclosed in Patent Documents 3 to 9 can be used. The thickness of the LDH separator is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0035] The zinc secondary battery 10 may further include a liquid-retaining member 42 in contact with the positive electrode plate 36 and / or the negative electrode plate 38. For example, it is preferable that not only the hydroxide ion conductive separator 40 but also the liquid-retaining member 42 be interposed between the positive electrode plate 36 and the negative electrode plate 38. As shown in FIG. 13 , it is preferable that the positive electrode plate 36 and / or the negative electrode plate 38 be covered or enclosed by the liquid-retaining member 42. However, a simple configuration in which the liquid-retaining member 42 is disposed on one side of the positive electrode plate 36 or the negative electrode plate 38 may also be used. In either case, the interposition of the liquid-retaining member 42 allows the electrolyte 34 to be evenly distributed between the positive electrode plate 36 / negative electrode plate 38 and the hydroxide ion conductive separator 40, thereby enabling efficient exchange of hydroxide ions between the positive electrode plate 36 / negative electrode plate 38 and the hydroxide ion conductive separator 40. The liquid-retaining member 42 is not particularly limited as long as it is a member capable of retaining the electrolyte solution 34, but is preferably a sheet-like member. Preferred examples of the liquid-retaining member 42 include nonwoven fabric, water-absorbent resin, liquid-retaining resin, porous sheet, and various spacers. Nonwoven fabric is particularly preferred because it allows for the production of a high-performance negative electrode structure at low cost. The liquid-retaining member 42 or nonwoven fabric preferably has a thickness of 10 to 200 μm, more preferably 20 to 200 μm, even more preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. A thickness within the above range allows a sufficient amount of electrolyte solution 34 to be retained within the liquid-retaining member 42 while keeping the overall size of the positive electrode structure and / or negative electrode structure compact and efficient.

[0036] When the positive electrode plate 36 and / or the negative electrode plate 38 are covered or wrapped with the liquid retention member 42 and / or the hydroxide ion conductive separator 40, it is preferable that their outer edges are closed (except for the upper edges from which the positive electrode tab lead 22p and the negative electrode tab lead 22n extend). In this case, the closed outer edges of the liquid retention member 42 and / or the hydroxide ion conductive separator 40 are preferably realized by folding the liquid retention member 42 and / or the hydroxide ion conductive separator 40, or by sealing the liquid retention members 42 together and / or the hydroxide ion conductive separators 40 together. Preferred examples of sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tape, sealing tape, and combinations thereof. In particular, LDH separators including a porous substrate made of a polymer material have the advantage of being flexible and therefore easily bendable. Therefore, it is preferable to form the LDH separator into a long shape and then fold it to close one outer edge. Thermal welding and ultrasonic welding can be performed using a commercially available heat sealer, but when sealing LDH separators together, it is preferable to perform thermal welding and ultrasonic welding by sandwiching the outer periphery of the liquid-retaining member 42 between the LDH separators that make up the outer periphery, as this provides more effective sealing. Commercially available adhesives, adhesive tapes, and sealing tapes can be used, but those containing alkali-resistant resins are preferred to prevent deterioration in alkaline electrolyte. From this perspective, preferred examples of adhesives include epoxy resin-based adhesives, natural resin-based adhesives, modified olefin resin-based adhesives, and modified silicone resin-based adhesives. Of these, epoxy resin-based adhesives are particularly preferred due to their excellent alkali resistance. An example of a commercially available epoxy resin-based adhesive is the epoxy adhesive Hysol® (manufactured by Henkel).

[0037] The outer edge of one side of the hydroxide ion conductive separator 40, which is the upper end, is preferably open. This open-top configuration can address the problem of overcharging in nickel-zinc batteries and the like. Specifically, when a nickel-zinc battery or the like is overcharged, oxygen (O2) can be generated at the positive electrode plate 36. However, the LDH separator has a high density that allows only hydroxide ions to pass through, preventing O2 from passing through. In this regard, the open-top configuration allows O2 to escape above the positive electrode plate 36 and be transported to the negative electrode plate 38 through the open-top portion within the battery case 13. This allows O2 to oxidize the Zn in the negative electrode active material back to ZnO. By undergoing this oxygen reaction cycle, the use of the open-top stacked cell 12 in a sealed zinc secondary battery can improve overcharge resistance. Even if the outer edge of one side of the hydroxide ion conductive separator 40 or the liquid-retaining member 42, which is the upper end, is closed, providing a vent hole in part of the closed outer edge can be expected to achieve the same effect as the open-top configuration. For example, the vent hole may be opened after sealing the outer edge of one side that will be the upper end of the LDH separator, or during sealing, part of the outer edge may be left unsealed so that the vent hole is formed.

[0038] The electrolyte 34 preferably contains an aqueous solution of an alkali metal hydroxide. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being more preferred. A zinc compound, such as zinc oxide or zinc hydroxide, may be added to the electrolyte to suppress the self-dissolution of zinc and / or zinc oxide. As mentioned above, the electrolyte may be mixed with a positive electrode active material and / or a negative electrode active material to form a positive electrode composite and / or a negative electrode composite. The electrolyte may also be gelled to prevent leakage of the electrolyte. A polymer that absorbs the solvent in the electrolyte and swells is preferably used as the gelling agent. Examples of suitable gelling agents include polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, as well as starch. [Example]

[0039] The present invention is further illustrated by the following examples.

[0040] Examples A1~A6 (1) Fabrication of nickel-zinc secondary batteries The following positive electrode plate, positive electrode current collector, negative electrode plate, negative electrode current collector, LDH separator, nonwoven fabric, battery container, and electrolyte were prepared. Positive electrode plate: The pores of the foamed nickel are filled with a positive electrode paste containing nickel hydroxide and a binder, and then dried (there is an uncoated area near one edge of the foamed nickel where the positive electrode paste is not applied). Positive electrode current collecting material: The uncoated part of the foamed nickel that makes up the positive electrode plate is compressed using a roll press to form a tab, and a tab lead (made of pure nickel, thickness: 100 μm) is ultrasonically welded to this tab to extend it. Negative electrode plate: A negative electrode paste containing ZnO powder, metallic Zn powder, polytetrafluoroethylene (PTFE), and propylene glycol is pressed onto a current collector (copper expanded metal) (there is an uncoated area near one edge of the copper expanded metal where the negative electrode paste is not applied). Negative electrode current collecting material: A tab lead (copper, thickness: 100 μm) is connected to the uncoated part of the copper expanded metal by ultrasonic welding. LDH separator: Ni-Al-Ti-LDH (layered double hydroxide) is deposited on the surface and pores of a polyethylene microporous membrane by hydrothermal synthesis and then roll-pressed. Thickness: 20 μm Nonwoven fabric: Polypropylene, 100 μm thick Battery case body: Box-shaped case made of modified polyphenylene ether resin (equipped with a pressure relief valve to release gas generated inside the case); Internal dimensions: length 190 mm, width 24 mm, height 165 mm; External dimensions: length 200 mm, width 30 mm, height 170 mm (excluding the height of the positive and negative terminals) Top cover: a top cover (length 200 mm, width 30 mm, distance a between central axis A1 and central axis A2 and distance b between central axis A1 and central axis A3 are shown in Table 1) made of modified polyphenylene ether resin having stepped holes (three stages of through holes consisting of a large diameter hole (inner diameter: 11.3 mm), a medium diameter hole (inner diameter: 6.2 mm), and a small diameter hole (inner diameter: 4.2 mm)) as shown in Figures 8 to 11 and a convex portion (thickness: 5.0 mm). Positive and negative electrode terminals: terminals made by SWCH (made by forging) having an outer terminal portion (diameter: 5 mm), a large diameter portion (diameter: 15 mm), a medium diameter portion (diameter: 6 mm), and a small diameter portion (diameter: 4 mm) in the shapes shown in Figures 8 to 11 First O-ring: EPDM O-ring (diameter: 11.5 mm) Second O-ring: EPDM O-ring (diameter: 6.5 mm) Positive electrode upper current collector plate and negative electrode upper current collector plate: SPCC plate-shaped member having a current collector plate body (thickness: 3 mm) and a bent portion (thickness: 3 mm) in the shape shown in Figures 8 to 11 Electrolyte: 5.4 mol / L KOH aqueous solution with 0.4 mol / L ZnO dissolved

[0041] The positive electrode plate was wrapped in nonwoven fabric so that it covered both sides, with the nonwoven fabric slightly protruding from the remaining three sides except for the side from which the positive electrode current collector extended. The excess portions of the nonwoven fabric protruding from the three sides of the positive electrode plate were heat-sealed with a heat seal bar to obtain a positive electrode structure. The negative electrode plate was wrapped in nonwoven fabric and LDH separator in this order from both sides, with the nonwoven fabric and LDH separator slightly protruding from the remaining three sides except for the side from which the negative electrode current collector extended. The excess portions of the nonwoven fabric and LDH separator protruding from the three sides of the negative electrode plate were heat-sealed with a heat seal bar to obtain a negative electrode structure. In this manner, multiple positive electrode structures and multiple negative electrode structures were prepared.

[0042] An electrode stack was fabricated by alternately stacking 12 positive electrode structures and 13 negative electrode structures. Similar to the configuration shown in FIG. 12 , the positive electrode tab leads 22p and the negative electrode tab leads 22n were designed to extend from different positions from each other in a plan view. Therefore, the positive electrode tab leads 22p overlapped each other, while the negative electrode tab leads 22n overlapped each other at different positions. As shown in FIGS. 1 and 2 , the overlapping portions of the positive electrode tab leads 22p were laser-welded together to the bent portion 30b of the positive electrode upper current collector plate 30p. Similarly, the overlapping portions of the negative electrode tab leads 22n were laser-welded together to the bent portion 30b of the negative electrode upper current collector plate 30n. In this way, a stack of electrode structures including the positive electrode tab leads 22p and the negative electrode tab leads 22n was obtained as the laminated cell 12. The stacked cell 12 joined to the positive electrode upper current collector plate 30p and the negative electrode upper current collector plate 30n was placed in a box-shaped battery case body 14, and the electrolyte 34 was poured in to impregnate the stacked cell 12, and the top lid 16 was closed and sealed. In this way, a nickel-zinc secondary battery 10 was produced.

[0043] (3) Accelerated leakage resistance test The fabricated nickel-zinc secondary batteries were stored in a high-temperature, high-humidity (65°C / 80%) environment. The number of days from the start of storage until the first visual observation of carbonate derived from the electrolyte deposited on the top of the negative electrode terminal 18n was measured. The number of days until salt deposition was evaluated and rated according to the following criteria. The results are shown in Table 1. <Leak resistance evaluation criteria> - Rating A: Salt deposition occurs in 30 days or more - Rating B: The number of days until salt deposition is 29 days or less

[0044] [Table 1]

[0045] Examples B1~B4 (reference) The accelerated leakage resistance test was conducted in the same manner as in Examples A1 to A6, except that a conventional modified polyphenylene ether resin top cover (b / a less than 0.85) as shown in Figures 17 to 19 and a nickel-plated SWCH negative electrode terminal with a surface having an arithmetic mean roughness Ra shown in Table 2 were used. Four types of negative electrode terminals were fabricated, each with a different arithmetic mean roughness Ra of the surfaces facing the first O-ring, second O-ring, and stepped hole. The variation in Ra was achieved by appropriately changing the manufacturing method of the negative electrode terminal as shown in Table 2.

[0046] (Accelerated leakage resistance test) The fabricated nickel-zinc secondary battery was stored in a high-temperature, high-humidity (65°C / 80%) environment. The number of days from the start of storage until the first visual observation of carbonate derived from the electrolyte deposited on the top of the negative electrode terminal 18n was measured. The results are shown in Table 2.

[0047] [Table 2]

[0048] The results shown in Table 2 indicate that increasing the arithmetic mean roughness Ra of the surfaces of the negative electrode terminal facing the first O-ring, the second O-ring, and the stepped hole can increase the number of days until leakage is confirmed. Note that these Examples B1 to B4 are considered reference examples because they do not use top covers that satisfy the b / a ratio of 0.85 or greater, a requirement of the present invention. However, the finding that increasing the arithmetic mean roughness Ra can more effectively suppress leakage naturally applies to zinc secondary batteries of the present invention with improved top cover structures (b / a ratios of 0.85 or greater). In other words, increasing the arithmetic mean roughness Ra of the specific portions of the negative electrode terminal is effective in further enhancing the leakage suppression effect in zinc secondary batteries of the present invention.

Claims

1. a stacked cell having battery components of an upper tab current collection type zinc secondary battery with tab leads extending from the top; a box-shaped battery case body in which the stacked cells are housed so that each of the battery components is oriented vertically; a long plate-shaped top cover that closes an upper opening of the battery case body; an electrode terminal that penetrates the upper cover and protrudes to the outside; a leakage suppression current collecting structure that suppresses leakage from the electrode terminal; A zinc secondary battery comprising: The liquid leakage suppressing current collecting structure is - stepped holes as through holes having at least three stages, each having a large diameter hole, a medium diameter hole, and a small diameter hole in this order from the front surface to the back surface of the upper cover; a first O-ring placed in the step formed by the large diameter hole and the medium diameter hole; a second O-ring placed in the step formed by the medium diameter hole and the small diameter hole; - the electrode terminal is inserted into the stepped hole and fits liquid-tightly with the stepped hole via the first O-ring and the second O-ring, the electrode terminal comprising: an external terminal portion protruding from an upper surface of the top cover; a flange-shaped large diameter portion in surface contact with the upper surface of the top cover; a medium diameter portion having a diameter that fits into the medium diameter hole; and a small diameter portion having a diameter that fits into the small diameter hole; an upper current collecting plate connected to a lower end of the electrode terminal, the upper current collecting plate including: a current collecting plate body arranged parallel to the upper cover; and a bent portion bent and extending vertically downward from a position of the current collecting plate body closer to the center of the battery than the electrode terminal; - the laminated cell, the tab lead being joined to the bent portion and suspended from the bent portion; - at least one convex portion provided on the rear surface of the upper cover at a position outside the electrode terminal, extending in a short direction of the upper cover, and in surface contact with the current collecting plate body to provide a fulcrum; Equipped with The longitudinal direction of the upper lid, which is the direction from the center of the battery toward the outside, is defined as the X direction, and the lateral direction of the upper lid is defined as the Y direction. When the leakage suppressing current collecting structure is viewed in cross section in the Y direction, the central axis A of the electrode terminal １ , the central axis A in the X direction of the joint portion between the bent portion and the tab lead ２ and the central axis A of the convex portion located at the farthest position from the electrode terminal in the X direction. ３ With respect to the central axis A １ and central axis A ２ Center axis A with respect to distance a １ and central axis A ３ A zinc secondary battery, wherein the ratio of the distance b to the electrode, b / a, is 0.85 or more.

2. 2. The zinc secondary battery according to claim 1, wherein the ratio of b / a is 0.90 to 1.

50.

3. Central axis A １ and central axis A ２ The zinc secondary battery according to claim 1 or 2, wherein the distance a is 10 to 40 mm.

4. Central axis A １ and central axis A ３ The zinc secondary battery according to claim 1 or 2, wherein the distance b is 10 to 40 mm.

5. 3. The zinc secondary battery according to claim 1, wherein the electrode terminal is a pressed product having a three-stage structure composed of the large diameter portion, the medium diameter portion, and the small diameter portion.

6. The zinc secondary battery according to claim 1 or 2, wherein the surfaces of the portions of the electrode terminal facing the first O-ring, the second O-ring, and the stepped hole have an arithmetic mean roughness Ra of 0.2 to 1.0 μm.

7. The laminated cell is a plurality of positive electrode plates each including a positive electrode active material layer and a positive electrode current collector; a plurality of positive electrode tab leads extending from each end of the positive electrode plate; a plurality of negative electrode plates each including a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound, and a negative electrode current collector; a plurality of negative electrode tab leads extending from each end of the negative electrode plate at positions that do not overlap with the positive electrode tab leads; a plurality of hydroxide ion conductive separators that separate the positive electrode plates and the negative electrode plates so as to be capable of conducting hydroxide ions; An electrolyte; The positive electrode plate and the negative electrode plate are alternately stacked with the hydroxide ion conductive separator sandwiched therebetween, 3. The zinc secondary battery according to claim 1, wherein the zinc secondary battery has two of the leakage prevention current collecting structures positioned opposite each other, and the bent portion of one of the leakage prevention current collecting structures is joined to an assembly of the multiple positive electrode tab leads, and the bent portion of the remaining leakage prevention current collecting structure is joined to an assembly of the multiple negative electrode tab leads.

8. 8. The zinc secondary battery according to claim 7, wherein the positive electrode plate and / or the negative electrode plate is covered or enveloped with the hydroxide ion conducting separator.

9. 8. The zinc secondary battery according to claim 7, wherein not only the hydroxide ion conductive separator but also a liquid retaining member is interposed between the positive electrode plate and the negative electrode plate.

10. The zinc secondary battery according to claim 9 , wherein the positive electrode plate and / or the negative electrode plate is covered or wrapped with the liquid retaining member.

11. 8. The zinc secondary battery according to claim 7, wherein the hydroxide ion-conducting separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound.

12. The zinc secondary battery described in claim 11, wherein the LDH separator further comprises a porous substrate, and the LDH and / or LDH-like compound is composited with the porous substrate in a form filled in the pores of the porous substrate.

13. 3. The zinc secondary battery according to claim 1, wherein the zinc secondary battery is a nickel-zinc secondary battery.

14. 3. The zinc secondary battery according to claim 1, wherein the zinc secondary battery is an air-zinc secondary battery.

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