Negative electrode plate and zinc secondary battery comprising same

Abstract

Provided is a negative electrode plate that suppresses in-plane diffusion of zinc acid ions and makes it possible to delay a shape change. The negative electrode plate comprises: a negative electrode current collector; a partition wall that is provided to at least one surface of the negative electrode current collector and defines a plurality of segments that are separated from one another; and a negative electrode active material that is filled into each of the segments, the negative electrode active material containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds.

Description

Negative electrode plate and zinc secondary battery equipped with same

[0001] The present invention relates to a negative electrode plate and a zinc secondary battery including the same.

[0002] In zinc secondary batteries, such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc precipitates in the form of dendrites from the negative electrode during charging, penetrates the pores of the separator (e.g., nonwoven fabric) and reaches the positive electrode, resulting in a short circuit. Such short circuits caused by zinc dendrites shorten the battery's life after repeated charging and discharging.

[0003] To address the above-mentioned problems, batteries have been proposed that include a layered double hydroxide (LDH) separator that selectively allows hydroxide ions to pass through while preventing zinc dendrites from penetrating. For example, Patent Document 1 (WO 2013 / 118561) discloses a nickel-zinc secondary battery in which an LDH separator is provided between the positive and negative electrodes. Patent Document 2 (WO 2016 / 076047) also discloses a separator structure that includes an LDH separator fitted or bonded to a resin outer frame, and that the LDH separator has such high density that it is gas- and / or water-impermeable. This document also discloses that the LDH separator can be composited with a porous substrate. Patent Document 3 (WO 2016 / 067884) also discloses various methods for forming a dense LDH membrane on the surface of a porous substrate to obtain a composite material. This method includes a step of uniformly attaching a starting substance capable of providing a starting point for LDH crystal growth to a porous substrate, and then subjecting the porous substrate to hydrothermal treatment in a raw material aqueous solution to form a dense LDH membrane on the surface of the porous substrate. LDH separators have also been proposed in which the LDH / porous substrate composite material produced through hydrothermal treatment is roll-pressed to achieve further densification. For example, Patent Document 4 (WO 2019 / 124270) discloses an LDH separator comprising a polymeric porous substrate and LDH loaded into the porous substrate, and having a linear transmittance of 1% or more at a wavelength of 1000 nm.

[0004] 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 conductive layered compounds together with LDHs. For example, Patent Document 5 (WO 2020 / 255856) discloses a hydroxide ion conductive 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 containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al. This hydroxide ion conductive separator is 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.

[0005] Incidentally, Patent Document 6 (WO2019 / 069760) and Patent Document 7 (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 a zinc secondary battery (particularly a stacked battery thereof) capable of preventing zinc dendrite extension. Furthermore, Patent Document 8 (WO2021 / 193436) discloses a zinc secondary battery that includes a stack of alternating positive and negative electrode plates, a positive electrode current collector tab connected to a positive electrode current collector in the positive electrode plate, and a negative electrode current collector tab connected to a negative electrode current collector in the negative electrode plate, oriented vertically, with the positive electrode current collector tab and the negative electrode current collector tab protruding upward from the stack.

[0006] WO2013 / 118561WO2016 / 076047WO2016 / 067884WO2019 / 124270WO2020 / 255856WO2019 / 069760WO2019 / 077953WO2021 / 193436

[0007] Zinc secondary batteries are known to suffer from a problem known as negative electrode shape change, in which the negative electrode changes to an undesirable shape and size with repeated charge and discharge cycles. Specifically, an initially square negative electrode shrinks unevenly from the edges toward the center with repeated charge and discharge cycles, i.e., the outer periphery of the negative electrode is unevenly eroded and lost. This phenomenon is caused by the negative electrode active material (ZnO) that constitutes the negative electrode moving from the edges toward the center through repeated dissolution and precipitation associated with charge and discharge. In other words, the diffusion of zincate ions due to the dissolution of ZnO gradually deforms the negative electrode toward the center. This shape change of the negative electrode plate leads to a reduction in the effective area of ​​the negative electrode plate facing the positive electrode plate, resulting in increased battery resistance, reduced battery capacity, and ultimately a shortened lifespan of the zinc secondary battery.

[0008] The present inventors have now discovered that it is possible to provide a negative electrode plate that can suppress in-plane diffusion of zincate ions and delay shape change by providing partitions on the surface of the negative electrode current collector plate to separate the plate into a plurality of individual segments and filling each of the segments with a negative electrode active material.

[0009] Therefore, an object of the present invention is to provide a negative electrode plate capable of suppressing the in-plane diffusion of zincate ions and delaying the shape change.

[0010] The present invention provides the following aspects. [Aspect 1] A negative electrode plate comprising: a negative electrode current collector plate; a partition wall provided on at least one surface of the negative electrode current collector plate, separating a plurality of individualized segments; and a negative electrode active material filled in each of the segments, the negative electrode active material including at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds. [Aspect 2] The negative electrode plate according to Aspect 1, in which the negative electrode active material filled in adjacent segments is spaced apart from each other. [Aspect 3] The negative electrode plate according to Aspect 1 or 2, in which the partition wall and the negative electrode active material are provided on both surfaces of the negative electrode current collector plate. [Aspect 4] The negative electrode plate according to any one of Aspects 1 to 3, in which the partition wall has a vent structure that allows gas to pass between adjacent segments. [Aspect 5] The negative electrode plate according to Aspect 4, in which the vent structure includes at least one selected from the group consisting of a groove, a notch, and a hole. [Aspect 6] The negative electrode plate according to Aspect 4 or 5, wherein the negative electrode plate is intended for use in a vertical orientation, and the gas vent structure is provided at a position that would be the uppermost part of each of the segments when the negative electrode plate is arranged in a vertical orientation. [Aspect 7] The negative electrode plate according to any one of Aspects 1 to 6, wherein the partition wall is provided in a lattice pattern. [Aspect 8] The negative electrode plate according to Aspect 7, wherein the negative electrode plate has a rectangular shape, and the lattice-shaped partition wall is provided so as to be parallel or perpendicular to sides that form an outer periphery of the rectangular shape when the negative electrode plate is viewed in a plan view. [Aspect 9] The negative electrode plate according to Aspect 7, wherein the negative electrode plate has a rectangular shape, and the lattice-shaped partition wall is provided so as to form an angle of 30 to 60 degrees with one of the sides that form the outer periphery of the rectangular shape when the negative electrode plate is viewed in a plan view. [Aspect 10] The negative electrode plate according to any one of Aspects 1 to 9, wherein the partition wall is made of insulating resin. [Aspect 11] A zinc secondary battery comprising: a positive electrode, the negative electrode plate according to any one of Aspects 1 to 10, a separator separating the positive electrode and the negative electrode plate in a manner allowing hydroxide ion conductivity, and an electrolyte. [Aspect 12] The zinc secondary battery according to Aspect 11, wherein the separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound.[Aspect 13] The zinc secondary battery according to Aspect 12, 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 14] The zinc secondary battery according to any one of Aspects 11 to 13, wherein the positive electrode comprises nickel hydroxide and / or nickel oxyhydroxide, thereby forming the zinc secondary battery as a nickel-zinc secondary battery. [Aspect 15] The zinc secondary battery according to any one of Aspects 11 to 13, wherein the positive electrode is an air electrode, thereby forming the zinc secondary battery as a zinc-air secondary battery.

[0011] 5 is a schematic plan view showing an example of a negative electrode according to the present invention. FIG. 6 is a diagram schematically showing a cross section of the line AA' of the negative electrode shown in FIG. 1. FIG. 7 is a diagram schematically showing states before and after shape change in a negative electrode according to the present invention. FIG. 8 is a schematic top view showing an example of a lattice-shaped partition wall in a negative electrode according to the present invention. FIG. 9 is a schematic top view showing another example of a lattice-shaped partition wall in a negative electrode according to the present invention. FIG. 10 is a schematic top view showing an example of a configuration in which a vent structure is provided in the lattice-shaped partition wall shown in FIG. 4. FIG. 11 is a schematic top view showing an example of a configuration in which a vent structure is provided in the lattice-shaped partition wall shown in FIG. 5. FIG. 12 is a schematic cross-sectional view showing another example of a negative electrode according to the present invention. FIG. 13 is a schematic cross-sectional view showing an example of the internal structure of a secondary battery according to the present invention. FIG. 14 is a diagram schematically showing a cross section of the line BB' of the secondary battery shown in FIG. 15. FIG. 16 is a perspective view schematically showing a battery element of the secondary battery shown in FIG. 16. FIG. 17 is a cross-sectional view schematically showing a battery element of the secondary battery shown in FIG. 17.

[0012] 1 and 2 show a negative electrode plate 14 according to one embodiment of the present invention. The negative electrode plate 14 includes a negative electrode current collector 16, a partition wall 18, and a negative electrode active material 20. The partition wall 18 is provided on at least one surface of the negative electrode current collector 16 and partitions the negative electrode plate 14 into a plurality of individual segments S. The negative electrode active material 20 includes at least one material selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. The negative electrode active material 20 is filled into each of the segments S. By providing the partition wall 18 on the surface of the negative electrode current collector 16 to partition the plurality of individual segments S and filling each of the segments S with the negative electrode active material 20, a negative electrode plate 14 can be provided that can suppress in-plane diffusion of zincate ions and delay shape change.

[0013] As mentioned above, zinc secondary batteries are known to suffer from the problem of negative electrode shape change. Specifically, an initially square negative electrode plate shrinks unevenly from the edges toward the center as it undergoes repeated charge and discharge cycles. That is, the outer periphery of the negative electrode plate is unevenly eroded and lost. This phenomenon is caused by the negative electrode active material (ZnO) constituting the negative electrode plate migrating from the edges toward the center as it undergoes repeated dissolution and precipitation during charge and discharge. In other words, the negative electrode plate gradually deforms toward the center due to the diffusion of zincate ions caused by the dissolution of ZnO. The configuration of the present invention effectively suppresses this diffusion of zincate ions. Specifically, because the negative electrode active material 20 filled in each segment S is separated by partition walls 18, the movement of zincate ions Z between the segments S is prevented by the partition walls 18, as indicated by the arrows and crosses in Figure 2. As a result, the in-plane diffusion of zincate ions is suppressed, delaying shape change. 3, although the shape change itself occurs, the erosion of each segment S distributed within the surface of the negative electrode plate 14 from its outer periphery significantly delays the decrease in the effective area of ​​the negative electrode plate 14 facing the positive electrode plate. As a result, the timing at which an increase in battery resistance and a decrease in battery capacity occur can be significantly delayed, thereby realizing a longer life for the zinc secondary battery.

[0014] The negative electrode current collector 16 may be a non-perforated metal plate, but a metal plate with multiple (or many) openings is preferred from the viewpoint of fixing the negative electrode active material to the current collector. Preferred examples of such a negative electrode current collector 16 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, for example, a negative electrode plate consisting of a negative electrode / negative electrode current collector can be preferably produced by 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 expansion machine, and then shaping the cuts into a diamond or tortoiseshell shape. 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 punched metal.

[0015] The partition walls 18 are provided on at least one surface of the negative electrode current collector plate 16 and separate a plurality of individual segments S from one another. The partition walls 18 are preferably made of at least one material selected from the group consisting of metals, insulating resins, and ceramics, from the viewpoint of preventing the passage of zincate ions. The metal, insulating resin, or ceramic constituting the partition walls 18 is not particularly limited as long as it can prevent the passage of zincate ions, but insulating resins are preferred. Preferred examples of metals constituting the partition walls 18 include alkali-resistant metals such as nickel, titanium, zirconium, and tantalum, and metals coated with alkali-resistant resins. Preferred examples of ceramics constituting the partition walls 18 include alkali-resistant ceramics such as aluminum oxide, silicon carbide, zirconia, and silicon nitride. Preferred examples of insulating resins constituting the partition walls 18 include alkali-resistant resins such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVDF), polypropylene (PP), and polyethylene (PE).

[0016] The height of the partition walls 18 is not particularly limited, but the difference between the height of the partition walls 18 and the height of the active material (specifically, the value obtained by subtracting the height of the partition walls from the height of the active material) is preferably −0.3 to +0.2 mm, more preferably −0.1 to 0 mm. The thickness of the partition walls 18 is not particularly limited, but is preferably 0.1 to 5.0 mm, more preferably 0.2 to 3.0 mm, and even more preferably 0.5 to 2.0 mm.

[0017] The partition walls 18 are preferably arranged in a grid pattern. The grid pitch is preferably 0.05 to 50 mm, more preferably 0.1 to 20 mm, and even more preferably 0.2 to 5 mm. The grid-shaped partition walls 18 can be eroded in a uniform grid pattern within the surface of the negative electrode plate 14, as shown in FIG. 3, and can more effectively delay the reduction in the effective area of ​​the negative electrode plate 14 facing the positive electrode plate. In this case, it is preferable that the negative electrode plate 14 has a rectangular shape, and when the negative electrode plate 14 is viewed in plan, the grid-shaped partition walls 18 are arranged so as to be parallel or perpendicular to the sides that form the outer periphery of the rectangular shape of the negative electrode plate 14, as shown in FIG. 4. Alternatively, it is preferable that the negative electrode plate 14 has a rectangular shape, and when the negative electrode plate 14 is viewed in plan, the grid-shaped partition walls 18 are arranged so as to form an angle of 30 to 60 degrees (preferably 40 to 50 degrees, for example, 45 degrees) with respect to one of the sides that form the outer periphery of the rectangular shape of the negative electrode plate 14, as shown in FIG. 5.

[0018] As shown in FIGS. 6 and 7 , the partition wall 18 preferably has a vent structure 18 a that allows gas G to pass between adjacent segments S. It is known that hydrogen gas is generated from zinc in the negative electrode of a zinc secondary battery. The vent structure 18 a promotes the escape of hydrogen gas G from each segment S, thereby improving charge / discharge efficiency. The vent structure 18 a preferably includes at least one selected from the group consisting of a groove, a notch, and a hole, and more preferably a groove or a notch. The negative electrode plate 14 is preferably intended for use in a vertical orientation. In this case, by providing the vent structure 18 a at the position that would be the top of each segment S when the negative electrode plate 14 is arranged vertically, gas G in each segment S directly below can be efficiently vented upward through the vent structure 18 a, as shown by the arrows in FIGS. 6 and 7 . In other words, the gas G in the segment S directly below repeatedly moves through the gas vent structure 18a to the segment S directly above, so that the gas G is efficiently released from the upper end of the negative electrode plate 14 without accumulating in each segment S.

[0019] Each segment S is filled with a negative electrode active material 20. It is preferable that the negative electrode active materials 20 filled in adjacent segments S are spaced apart from each other. This reliably prevents the movement of zincate ions between the segments S (as indicated by the arrows and x in FIG. 2 ) by the partition walls 18. However, as long as the desired shape change delay effect is obtained, the negative electrode active materials 20 filled in adjacent segments S above the partition walls 18 may be somewhat connected to each other.

[0020] The partition wall 18 and the negative electrode active material 20 may be provided on only one surface of the negative electrode current collector 16. However, from the viewpoint of increasing energy density, it is preferable to provide them on both surfaces of the negative electrode current collector 16. In this case, as shown in Fig. 2, it is preferable to provide the partition wall 18 on one surface of the negative electrode current collector 16 and the partition wall 18 on the other surface of the negative electrode current collector 16 symmetrically to each other from the viewpoint of uniform reaction during electrode stacking. Alternatively, as shown in Fig. 8, the partition wall 18 on one surface of the negative electrode current collector 16 and the partition wall 18 on the other surface of the negative electrode current collector 16 may be provided so as to be offset from each other, which has the advantage of absorbing expansion and contraction of the electrodes and preventing battery expansion.

[0021] The negative electrode active material 20 includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds. The 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 an electrolyte solution 28 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, with polyacrylic acid being preferred due to its excellent chemical resistance to strong alkalis.

[0022] As the zinc alloy, a mercury- and lead-free zinc alloy known as a mercury-free zinc alloy can be used. 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 has the effect of suppressing hydrogen gas generation. In particular, indium and bismuth are advantageous in terms of improving discharge performance. The use of a zinc alloy for the negative electrode can suppress hydrogen gas generation and improve safety by slowing the rate of self-dissolution in alkaline electrolyte.

[0023] The shape of the negative electrode material is not particularly limited, but 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.

[0024] There is no particular limitation on the method for manufacturing the negative electrode plate 14. Preferably, the negative electrode plate 14 can be manufactured by providing a frame as the partition wall 18 on the surface of the negative electrode current collector 16 (for example, a copper plate such as a Sn-plated copper plate) and filling each segment S separated by the partition wall 18 with the negative electrode active material 20. Examples of the method for providing the partition wall 18 include a method of bonding the partition wall 18 onto the negative electrode current collector 16, a method of forming the partition wall 18 by screen-printing a resin on the negative electrode current collector 16, and a method of applying a resin onto the negative electrode current collector 16 with a dispenser to form the partition wall 18.

[0025] Zinc Secondary Battery The zinc secondary battery according to this embodiment is not particularly limited as long as it uses the negative electrode plate of the present invention 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.

[0026] 9 to 12 show a zinc secondary battery 10 according to one embodiment of the present invention. The zinc secondary battery 10 includes a battery element 11 in a battery case 30. The battery element 11 includes a positive electrode plate 12, the above-mentioned negative electrode plate 14, a separator 26 that separates the positive electrode plate 12 and the negative electrode plate 14 so as to be conductive to hydroxide ions, and an electrolyte 28.

[0027] The positive electrode plate 12 includes a positive electrode active material layer 12a. The positive electrode active material constituting the positive electrode active material layer 12a may be selected 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 12 further includes a positive electrode current collector (not shown), which preferably has a positive electrode current collector tab 12b extending from an end (e.g., the upper end) of the positive electrode plate 12. A preferred example of a 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 / 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 12 shown in FIG. 12 includes a positive electrode current collector (e.g., nickel foam), 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 current collector tab 12b 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 nickel foam plate, it can be processed into a tab shape by pressing. In either case, the positive electrode current collector tab 12b may be extended by attaching another current collecting member such as a tab lead to the tab. In either case, it is preferable that multiple positive electrode current collector tabs 12b be joined to a single positive electrode terminal 36 or a member electrically connected thereto to form a positive electrode tab joint (not shown). This allows current collection to be performed with a simple configuration and in a space-efficient manner, and also facilitates connection to the positive electrode terminal 36. The positive electrode current collecting tab 12b can be joined to a member such as a terminal using a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0028] The positive electrode plate 12 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 12 may also contain cobalt. The cobalt is preferably contained in the positive electrode plate 12 in the form of cobalt oxyhydroxide. In the positive electrode plate 12, cobalt functions as a conductive additive, thereby contributing to improving the charge / discharge capacity.

[0029] The negative electrode plate 14 has the configuration described above. In the zinc secondary battery 10 of this embodiment, a negative electrode current collector tab 22 extending from an end (e.g., the upper end) of the negative electrode plate 14 is preferably connected to the negative electrode current collector plate 16. The negative electrode current collector tab 22 preferably extends from the end (e.g., the upper end) of the negative electrode plate 14 in a predetermined direction (e.g., upward) at a position that does not overlap with the positive electrode current collector tab 12b. The negative electrode current collector tab 22 may be made of the same material as the negative electrode current collector plate 16, or may be made of a different material. In either case, the negative electrode current collector tab 22 may be extended by adding another current collecting member such as a tab lead to the tab. In either case, it is preferable that multiple negative electrode current collector tabs 22 be joined to one negative electrode terminal 38 or a member electrically connected thereto to form a negative electrode tab joint 40. This allows for space-efficient current collection with a simple configuration and facilitates connection to the negative electrode terminal 38. The negative electrode current collecting tab 22 may be joined to a member such as a terminal using a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0030] The separator 26 is provided to separate the positive electrode plate 12 and the negative electrode plate 14 so as to allow hydroxide ion conductivity. Therefore, the separator 26 is preferably a hydroxide ion conductive separator. For example, as shown in FIG. 12 , the hydroxide ion conductive separator 26 may be configured so that the negative electrode plate 14 is covered or wrapped with the hydroxide ion conductive separator 26. This eliminates the need for a complicated sealing joint between the hydroxide ion conductive separator 26 and the battery container, making it possible to manufacture a nickel-zinc secondary battery (particularly a stacked battery thereof) capable of preventing zinc dendrite extension extremely easily and with high productivity. However, a simple configuration in which the hydroxide ion conductive separator 26 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may also be used.

[0031] The hydroxide ion-conductive separator 26 is not particularly limited as long as it is a separator capable of separating the positive electrode plate 12 and the negative electrode plate 14 in a manner that allows hydroxide ions to be conductively separated. Typically, however, the separator includes a hydroxide ion-conductive solid electrolyte and selectively transmits 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 26 is preferably an LDH separator. As used herein, an "LDH separator" is defined as a separator that includes an LDH and / or an LDH-like compound and selectively transmits 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 similar to LDH, even if it may not be called an LDH, and can be considered an equivalent of LDH. However, in a broad definition, "LDH" can be interpreted as encompassing 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 thus 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 is 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 1 to 7 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.

[0032] It is preferable that not only the hydroxide ion conductive separator 26 but also a liquid retention member 27 be interposed between the positive electrode plate 12 and the negative electrode plate 14. It is also preferable that the positive electrode plate 12 and / or the negative electrode plate 14 be covered or wrapped with the liquid retention member 27. However, a simple configuration in which the liquid retention member 27 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may also be used. In either case, the interposition of the liquid retention member 27 allows the electrolyte 28 to be evenly distributed between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conductive separator 26, thereby enabling efficient exchange of hydroxide ions between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conductive separator 26. The liquid retention member 27 is not particularly limited as long as it is a material capable of retaining the electrolyte 28, but is preferably a sheet-like material. Preferred examples of the liquid-retaining member 27 include nonwoven fabric, water-absorbent resin, liquid-retaining resin, porous sheet, and various spacers, but 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 27 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 28 to be retained within the liquid-retaining member 27 while keeping the overall size of the positive electrode structure and / or negative electrode structure compact and efficient.

[0033] When the positive electrode plate 12 and / or the negative electrode plate 14 are covered or wrapped with the liquid retention member 27 and / or the separator 26, it is preferable that their outer edges are closed (except for the edges from which the positive electrode current collector tab 12b and the negative electrode current collector tab 22 extend). In this case, the closed edges of the outer edges of the liquid retention member 27 and / or the separator 26 are preferably realized by folding the liquid retention member 27 and / or the separator 26, or by sealing the liquid retention members 27 together and / or the separators 26 together. Preferred examples of sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tape, sealing tape, and combinations thereof. In particular, since an LDH separator including a porous substrate made of a polymer material has the advantage of being flexible and therefore easily bendable, it is preferable to form the LDH separator into a long shape and then fold it to close one edge of the outer edge. Thermal welding and ultrasonic welding can be performed using a commercially available heat sealer, etc., 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 27 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 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).

[0034] It is preferable that the outer edge of one side of the separator 26, which is the upper end, is open. This open-top structure makes it possible to deal with the problem of overcharging in nickel-zinc batteries and the like. That is, when a nickel-zinc battery or the like is overcharged, oxygen (O ２ ) may occur, but the LDH separator has such a high density that it allows only hydroxide ions to pass through, so O ２ In this respect, the open-top structure allows O２ can escape above the positive electrode plate 12 and be sent to the negative electrode plate 14 side through the upper open portion, thereby ２ The Zn in the negative electrode active material can be oxidized and returned to ZnO by this oxygen reaction cycle. By using the open-top battery element 11 in a sealed zinc secondary battery, overcharge resistance can be improved. Even when the outer edge of one side of the separator 26 or the liquid-retaining member 27, which is the upper end, is closed, the same effect as the open-top configuration can be expected by providing a vent hole in part of the closed outer edge. For example, the vent hole may be opened after sealing the outer edge of one side of the upper end of the LDH separator, or a part of the outer edge may be left unsealed during sealing so that the vent hole is formed.

[0035] The electrolyte 28 preferably contains an aqueous solution of an alkali metal hydroxide. Although the electrolyte 28 is only shown locally in FIG. 12 , this is because it is distributed throughout the positive and negative electrode plates 12 and 14. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being preferred. To suppress the self-dissolution of zinc and / or zinc oxide, a zinc compound such as zinc oxide or zinc hydroxide may be added to the electrolyte. As mentioned above, the electrolyte may be mixed with the positive electrode active material and / or the 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.

[0036] 11 and 12, the battery element 11 preferably has a positive and negative electrode laminate configuration, in which a plurality of positive electrode plates 12, a plurality of negative electrode plates 14, and a plurality of separators 26 are stacked in a repeated manner, with the positive electrode plates 12 / separators 26 / negative electrode plates 14. That is, the zinc secondary battery 10 preferably includes a plurality of unit cells 10a, which together form a multi-layer cell. This is the configuration of a so-called assembled battery or stacked battery, and is advantageous in that it can provide a high voltage and a large current.

[0037] The battery case 30 is preferably made of resin. The resin constituting the battery case 30 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 ABS resin or modified polyphenylene ether. The battery case 30 has a top lid 30a. The battery case 30 (e.g., the top lid 30a) may have a pressure relief valve for releasing gas. Furthermore, a group of cases in which two or more battery cases 30 are arranged may be housed within an outer frame to form a battery module.

[0038] LDH-Like Compound According to a preferred embodiment of the present invention, the LDH separator may contain an LDH-like compound. The definition of the LDH-like compound is as described above. Preferred LDH-like compounds are: (a) hydroxides and / or oxides having a layered crystal structure containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al; or (b) hydroxides and / or oxides having a layered crystal structure containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) at least one additional element M selected from the group consisting of In, Bi, Ca, Sr, and Ba; or (c) hydroxides and / or oxides having a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In, wherein the LDH-like compound in (c) is In(OH). ３ It exists in the form of a mixture with

[0039] According to a preferred aspect (a) of the present invention, the LDH-like compound may be a hydroxide and / or oxide having a layered crystal structure containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al. Therefore, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Mg, Ti, optionally Y, and optionally Al. While the above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, it is preferable that the LDH-like compound does not contain Ni. For example, the LDH-like compound may further contain Zn and / or K. This can further improve the ionic conductivity of the LDH separator.

[0040] LDH-like compounds can be identified by X-ray diffraction. Specifically, when X-ray diffraction is performed on the surface of an LDH separator, peaks attributable to LDH-like compounds are typically detected in the range of 5°≦2θ≦10°, more typically in the range of 7°≦2θ≦10°. As described above, LDHs are formed by stacking hydroxide base layers, with exchangeable anions and H as intermediate layers. ２ O is present. In this regard, when LDH is measured by X-ray diffraction, a peak due to the crystalline structure of LDH (i.e., the (003) peak of LDH) is inherently detected at 2θ = 11 to 12°. In contrast, when an LDH-like compound is measured by X-ray diffraction, a peak is typically detected in the above-mentioned range, which is shifted to a lower angle than the peak position of LDH. Furthermore, the interlayer distance of the layered crystalline structure can be determined by the Bragg equation using 2θ corresponding to the peak due to the LDH-like compound in X-ray diffraction. The interlayer distance of the layered crystalline structure constituting the LDH-like compound determined in this manner is typically 0.883 to 1.8 nm, more typically 0.883 to 1.3 nm.

[0041] In the LDH separator according to the above aspect (a), the atomic ratio of Mg / (Mg + Ti + Y + Al) in the LDH-like compound, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.03 to 0.25, more preferably 0.05 to 0.2. The atomic ratio of Ti / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0.40 to 0.97, more preferably 0.47 to 0.94. The atomic ratio of Y / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0 to 0.45, more preferably 0 to 0.37. The atomic ratio of Al / (Mg + Ti + Y + Al) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.03. Within the above range, the alkali resistance is more excellent, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－ is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the atomic ratio in the LDH-like compound generally deviates from the general formula of LDH. Therefore, it can be said that the LDH-like compound in this embodiment generally has a composition ratio (atomic ratio) different from that of conventional LDH. Note that EDS analysis is preferably performed using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000x, 2) performing three-point analysis in point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of a total of six points.

[0042] According to another preferred aspect (b) of the present invention, the LDH-like compound may be a hydroxide and / or oxide having a layered crystal structure containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) an additional element M. Thus, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Ti, Y, the additional element M, optionally Al, and optionally Mg. The additional element M is In, Bi, Ca, Sr, Ba, or a combination thereof. While the above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, it is preferred that the LDH-like compound does not contain Ni.

[0043] In the LDH separator according to the above aspect (b), the atomic ratio of Ti / (Mg+Al+Ti+Y+M) in the LDH-like compound, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.50 to 0.85, more preferably 0.56 to 0.81. The atomic ratio of Y / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.20, more preferably 0.07 to 0.15. The atomic ratio of M / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.35, more preferably 0.03 to 0.32. The atomic ratio of Mg / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.10, more preferably 0 to 0.02. The atomic ratio of Al / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.04. Within the above range, the alkali resistance is more excellent, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. Incidentally, LDHs conventionally known for LDH separators have the general formula: M ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the atomic ratio in the LDH-like compound generally deviates from the general formula of LDH. Therefore, it can be said that the LDH-like compound in this embodiment generally has a composition ratio (atomic ratio) different from that of conventional LDH. Note that EDS analysis is preferably performed using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000x, 2) performing three-point analysis in point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of a total of six points.

[0044] According to yet another preferred embodiment (c) of the present invention, the LDH-like compound is a hydroxide and / or oxide of a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In, and the LDH-like compound is In(OH) ３ The LDH-like compound of this embodiment is a hydroxide and / or oxide having a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In. Therefore, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Mg, Ti, Y, optionally Al, and optionally In. Note that the In that can be contained in the LDH-like compound is not only that which is intentionally added to the LDH-like compound, but also In(OH) ３ The above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, but it is preferable that the LDH-like compound does not contain Ni. Incidentally, LDHs conventionally known for LDH separators are represented by the general formula: M ２＋ １－ｘ M ３＋ ｘ (OH) ２ A ｎ－ ｘ／ｎ ・mH ２ O (in the formula, M ２＋ is a divalent cation, M ３＋ is a trivalent cation, and A ｎ－is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. In contrast, the atomic ratios in LDH-like compounds generally deviate from the above general formula of LDH. Therefore, it can be said that the LDH-like compounds in this embodiment generally have composition ratios (atomic ratios) different from those of conventional LDHs.

[0045] The mixture according to the above embodiment (c) contains not only LDH-like compounds but also In(OH) ３ (typically LDH-like compounds and In(OH) ３ It is composed of In(OH) ３ The inclusion of In(OH) in the mixture can effectively improve the alkali resistance and dendrite resistance of the LDH separator. ３ The content of In(OH) is preferably an amount that can improve the alkali resistance and dendrite resistance of the LDH separator without substantially impairing the hydroxide ion conductivity, and is not particularly limited. ３ may have a cubic crystal structure, and In(OH) ３ The crystal may be surrounded by an LDH-like compound. ３ can be identified by X-ray diffraction.

Claims

1. A negative electrode current collector; A partition wall is provided on at least one surface of the negative electrode current collector plate, and partitions a plurality of individual segments from each other. a negative electrode active material filled in each of the segments, the negative electrode active material including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound; wherein the partition wall has a vent structure that allows gas to pass between adjacent segments, and the vent structure includes at least one selected from the group consisting of a groove, a notch, and a hole.

2. The negative electrode plate according to claim 1 , wherein the negative electrode active materials packed in adjacent segments are spaced apart from each other.

3. The negative electrode plate according to claim 1 , wherein the partition wall and the negative electrode active material are provided on both sides of the negative electrode current collector plate.

4. The negative electrode plate according to claim 1 or 2, wherein the negative electrode plate is intended for use in a vertical orientation, and the gas venting structure is provided at a position that would be the topmost part of each of the segments when the negative electrode plate is placed in a vertical orientation.

5. The negative electrode plate according to claim 1 or 2, wherein the partition walls are provided in a lattice pattern.

6. The negative electrode plate according to claim 5 , wherein the negative electrode plate has a rectangular shape, and when the negative electrode plate is viewed in a plan view, the lattice-shaped partition wall is provided so as to be parallel or perpendicular to a side that constitutes an outer periphery of the rectangular shape.

7. The negative electrode plate has a rectangular shape, and when the negative electrode plate is viewed in a plan view, the lattice-shaped partition wall is provided in a direction that forms an angle of 30 to 60 degrees with respect to one of the sides that constitute the outer periphery of the rectangular shape. The negative electrode plate according to claim 5.

8. The negative electrode plate according to claim 1 , wherein the partition wall is made of an insulating resin.

9. A positive electrode and The negative electrode plate according to claim 1 or 2, a separator that separates the positive electrode and the negative electrode plate so as to be capable of conducting hydroxide ions; An electrolyte; A zinc secondary battery comprising:

10. 10. The zinc secondary battery according to claim 9, wherein the separator is an LDH separator comprising a layered double hydroxide (LDH) and / or an LDH-like compound.

11. The zinc secondary battery described in claim 10, 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.

12. 10. The zinc secondary battery according to claim 9, wherein the positive electrode comprises nickel hydroxide and / or nickel oxyhydroxide, thereby making the zinc secondary battery a nickel-zinc secondary battery.

13. 10. The zinc secondary battery according to claim 9, wherein the positive electrode is an air electrode, thereby making the zinc secondary battery a zinc-air secondary battery.