Zinc secondary battery

Abstract

Provided is an upper tab-type zinc secondary battery that is not prone to short-circuiting. This zinc secondary battery comprises: a positive electrode plate including a positive electrode active material layer, and a positive electrode current collector; a positive electrode tab lead extending from an end portion of the positive electrode plate; a negative electrode plate including a negative electrode active material layer including zinc and the like, and a negative electrode current collector; a negative electrode tab lead extending from an end portion of the negative electrode plate; a hydroxide ion-conductive separator; and an electrolyte solution. The positive electrode plate, the positive electrode tab lead, the negative electrode plate, the negative electrode tab lead, and the hydroxide ion-conductive separator are all arranged oriented vertically. The positive electrode tab lead and the negative electrode tab lead extend upwards. Each electrode plate has a non-coated region where the electrode active material layer is not present along the upper edge of the electrode plate. The tab lead is welded to the current collector in said non-coated region, and an insulating tape is affixed to the non-coated region such that the welded portion is covered by the insulating tape.

Description

Technical Field

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

Background Art

[0002] In zinc secondary batteries such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc is deposited in a dendrite shape from the negative electrode during charging, penetrates the voids of a separator such as a non-woven fabric, and reaches the positive electrode. As a result, it is known that a short circuit is caused. Such a short circuit caused by zinc dendrites leads to a shortening of the repeated charge-discharge life.

[0003] To address the above problems, a battery equipped with a layered double hydroxide (LDH) separator that selectively permeates hydroxide ions while preventing the penetration of zinc dendrites has been proposed. For example, Patent Document 1 (WO2013 / 118561) discloses providing an LDH separator between the positive and negative electrodes in a nickel-zinc secondary battery. Further, Patent Document 2 (WO2016 / 076047) discloses a separator structure including an LDH separator fitted or joined to a resin outer frame, and it is disclosed that the LDH separator has a high degree of denseness such as gas impermeability and / or water impermeability. This document also discloses that the LDH separator can be composited with a porous substrate. Furthermore, Patent Document 3 (WO2016 / 067884) discloses various methods for obtaining a composite material by forming an LDH dense film on the surface of a porous substrate. This method includes a step of uniformly adhering a starting material capable of giving a starting point for crystal growth of LDH to the porous substrate and subjecting the porous substrate to hydrothermal treatment in an aqueous raw material solution to form an LDH dense film on the surface of the porous substrate. An LDH separator that achieves further densification by roll-pressing a composite material of LDH / porous substrate produced through hydrothermal treatment has also been proposed. For example, Patent Document 4 (WO2019 / 124270) discloses an LDH separator including a polymer porous substrate and LDH filled in the porous substrate, having a linear transmittance of 1% or more at a wavelength of 1000 nm.

[0004] In addition, LDH-like compounds are known as hydroxides and / or oxides having a layered crystal structure similar to but not called LDH, and exhibit hydroxide ion conduction characteristics similar enough to be collectively referred to as hydroxide ion conductive layered compounds together with LDH. For example, Patent Document 5 (WO2020 / 255856) discloses a hydroxide ion conductive separator including a porous substrate and a layered double hydroxide (LDH)-like compound that closes the pores of the porous substrate, wherein the LDH-like compound is a hydroxide and / or oxide having a layered crystal structure containing Mg and at least one element selected from the group consisting of Ti, Y, and Al, including at least Ti. This hydroxide ion conductive separator is said to be superior in alkali resistance to conventional LDH separators and to be able to more effectively suppress short circuits caused by zinc dendrites.

[0005] By the way, Patent Documents 6 (WO2019 / 069760) and 7 (WO2019 / 077953) propose a zinc secondary battery configured to cover or enclose the entire negative electrode active material layer with a liquid retention member and an LDH separator and to cover or enclose the positive electrode active material layer with a liquid retention member. A non-woven fabric is used as the liquid retention member. According to such a configuration, it is said that a zinc secondary battery (especially its laminated battery) capable of preventing the growth of zinc dendrites can be produced extremely simply and with high productivity without the need for complicated sealing and joining between the LDH separator and the battery container. In addition, Patent Document 8 (WO2021 / 193436) discloses a zinc secondary battery including a laminate alternately provided with 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, wherein the positive electrode current collector tab and the negative electrode current collector tab project upward from the laminate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] When manufacturing a zinc secondary battery of the type in which the current collecting tab extends upward from the electrode laminate (hereinafter referred to as the upper tab method) as disclosed in Patent Document 8, a tab lead (current collecting tab) is connected to the electrode current collector by welding, and this tab lead is connected to the electrode terminal. FIGS. 9A and 9B show an example of such an upper tab type zinc secondary battery 110. The zinc secondary battery 110 includes an electrode laminate 111 including a positive electrode plate 112 including a positive electrode active material layer 112a and a positive electrode current collector 112b, and a negative electrode plate 114 including a negative electrode active material layer 114a and a negative electrode current collector 114b. As shown in FIG. 10, an uncoated region U in which the positive electrode current collector 112b (or the negative electrode current collector 114b) is exposed without being covered by the positive electrode active material layer 112a (or the negative electrode active material layer 114a) exists above the positive electrode plate 112 (or the negative electrode plate 114), and a positive electrode tab lead 113 (or a negative electrode tab lead 115) is joined to this uncoated region U by welding. As shown in FIG. 11, the positive electrode plate 112 (or the negative electrode plate 114) is covered or wrapped with a hydroxide ion conductive separator 116 and / or a liquid retention member 117. Then, as shown in FIGS. 9A and 9B, the positive electrode tab leads 113 extending from the plurality of positive electrode plates 112 are joined together to the positive electrode terminal 126 at the positive electrode tab joint portion 130, while the negative electrode tab leads 115 extending from the plurality of negative electrode plates 114 are joined together to the negative electrode terminal 128 at the negative electrode tab joint portion 132.

[0008] However, if the welding between the tab leads 113 or 115 and the current collectors 112b or 114b is insufficient, the tab leads 113 or 115 may be peeled off (or partially detached) from the current collectors 112b or 114b due to the load generated when aggregating a plurality of tab leads 113 or 115. For example, such peeling may also be caused by the load resulting from the expansion and contraction of the positive electrode plate 112 and / or the negative electrode plate 114 during charge and discharge. In such a case, there is a concern that the sharp end of the tab lead 113 or 115 may pierce through the hydroxide ion conductive separator 116 and / or the liquid retention member 117 in the vicinity thereof, causing a short circuit S.

[0009] The inventors have now found that in the upper tab type zinc secondary battery, by attaching an insulating tape to the uncoated area of the electrode plate so as to cover the portion where the tab lead is welded and joined, it is possible to make it difficult to cause a short circuit.

[0010] Therefore, an object of the present invention is to provide an upper tab type zinc secondary battery in which a short circuit is less likely to occur.

[0011] According to the present invention, the following aspects are provided. [Aspect 1] A positive electrode plate including a positive electrode active material layer and a positive electrode current collector, A positive electrode tab lead extending from an end of the positive electrode plate, A negative electrode plate including a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compound, and a negative electrode current collector, A negative electrode tab lead extending from an end of the negative electrode plate at a position not overlapping with the positive electrode tab lead, A hydroxide ion conductive separator that ionically isolates the positive electrode plate and the negative electrode plate, An electrolytic solution, A zinc secondary battery comprising: Each of the positive electrode plate, the positive electrode tab lead, the negative electrode plate, the negative electrode tab lead, and the hydroxide ion conductive separator is arranged vertically, and the positive electrode tab lead and the negative electrode tab lead extend upward. The positive electrode plate has an uncoated region where the positive electrode active material layer does not exist along the upper end of the positive electrode plate, and in the uncoated region, the positive electrode tab lead is welded and joined to the positive electrode current collector, and an insulating tape is attached to the uncoated region so that the welded and joined portion is covered with the insulating tape, and / or The negative electrode plate has an uncoated region where the negative electrode active material layer does not exist along the upper end of the negative electrode plate, and in the uncoated region, the negative electrode tab lead is welded and joined to the negative electrode current collector, and an insulating tape is attached to the uncoated region so that the welded and joined portion is covered with the insulating tape. A zinc secondary battery. [Aspect 2] In the zinc secondary battery according to Aspect 1, 60% or more of the area of the uncoated region on both sides of the positive electrode plate is covered with the insulating tape, and / or 60% or more of the area of the uncoated region on both sides of the negative electrode plate is covered with the insulating tape. [Aspect 3] The lower end of the insulating tape on the positive electrode plate is located between the upper end of the positive electrode active material layer and the lower end of the positive electrode tab lead, and / or In the zinc secondary battery according to Aspect 1 or 2, the lower end of the insulating tape on the negative electrode plate is located between the upper end of the negative electrode active material layer and the lower end of the negative electrode tab lead. [Aspect 4] The insulating tape is attached to both sides of the uncoated region of the positive electrode plate so that the upper end of the insulating tape is located above the upper end of the positive electrode current collector, and the upper end portions of the insulating tape protruding from the upper end of the positive electrode current collector are bonded to each other, and / or In the zinc secondary battery according to any one of Aspects 1 to 3, the insulating tape is attached to both sides of the uncoated region of the negative electrode plate so that the upper end of the insulating tape is located above the upper end of the negative electrode current collector, and the upper end portions of the insulating tape protruding from the upper end of the negative electrode current collector are bonded to each other. [Aspect 5] The insulating tape is attached to both sides of the uncoated area of the positive electrode plate such that the left and right ends of the insulating tape are positioned outside the left and right ends of the positive current collector, and the left and right end portions of the insulating tape protruding from the left and right ends of the positive current collector are adhered to each other, and / or The insulating tape is attached to both sides of the uncoated area of the negative electrode plate such that the left and right ends of the insulating tape are positioned outside the left and right ends of the negative current collector, and the left and right end portions of the insulating tape protruding from the left and right ends of the negative current collector are adhered to each other. The zinc secondary battery according to Aspect 4. [Aspect 6] The zinc secondary battery according to any one of Aspects 1 to 5, wherein the positive electrode plate and / or the negative electrode plate is covered or wrapped with the hydroxide ion conductive separator. [Aspect 7] The zinc secondary battery according to any one of Aspects 1 to 6, wherein a liquid retention member is interposed between the positive electrode plate and the negative electrode plate in addition to the hydroxide ion conductive separator. [Aspect 8] The zinc secondary battery according to Aspect 7, wherein the positive electrode plate and / or the negative electrode plate is covered or wrapped with the liquid retention member. [Aspect 9] The zinc secondary battery according to any one of Aspects 1 to 8, wherein the hydroxide ion conductive separator is an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound. [Aspect 10] The zinc secondary battery according to Aspect 9, wherein the LDH separator further includes a porous substrate, and the LDH and / or the LDH-like compound is compounded with the porous substrate in a form filled in the pores of the porous substrate. [Aspect 11] The positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery forms a nickel-zinc secondary battery. The zinc secondary battery according to any one of Aspects 1 to 10. [Aspect 12] The zinc secondary battery according to any one of Aspects 1 to 10, wherein the positive electrode active material layer is an air electrode layer, and thereby the zinc secondary battery forms an air-zinc secondary battery. [Aspect 13] The zinc secondary battery according to any one of Aspects 1 to 12, comprising a plurality of unit cells each having a pair of the positive electrode plate and the negative electrode plate together with the hydroxide ion conductive separator, whereby the plurality of unit cells form a multilayer cell as a whole.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

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Figure 4A

Figure 4B

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Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0013] Zinc secondary battery The zinc secondary battery of the present invention is not particularly limited as long as it is a secondary battery using zinc as a negative electrode and an alkaline electrolyte (typically an aqueous solution of an alkali metal hydroxide). 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 various other alkaline zinc secondary batteries. For example, it is preferable that the positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery forms a nickel-zinc secondary battery. Alternatively, the positive electrode active material layer may be an air electrode layer, whereby the zinc secondary battery forms an air-zinc secondary battery.

[0014] FIGS. 1 to 6 show a zinc secondary battery 10 and its components according to an aspect of the present invention. The zinc secondary battery 10 includes an electrode laminate 11 and an electrolyte (not shown) in a battery case 20. The electrode laminate 11 includes a positive electrode plate 12, a positive electrode tab lead 13, a negative electrode plate 14, a negative electrode tab lead 15, and a hydroxide ion conductive separator 16. The positive electrode plate 12 includes a positive electrode active material layer 12a and a positive electrode current collector 12b. The positive electrode tab lead 13 extends from an end of the positive electrode plate 12 extendsIt is discharged. The negative electrode plate 14 includes a negative electrode active material layer 14a and a negative electrode current collector 14b, and a negative electrode tab lead 15 extends from an end portion of the negative electrode plate 14 at a position where it does not overlap with the positive electrode tab lead 13. The negative electrode active material layer 14a contains at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compound. The hydroxide ion conductive separator 16 separates the positive electrode plate 12 and the negative electrode plate 14 so that hydroxide ions can be conducted. Each of the positive electrode plate 12, the positive electrode tab lead 13, the negative electrode plate 14, the negative electrode tab lead 15, and the hydroxide ion conductive separator 16 is arranged vertically, and the positive electrode tab lead 13 and the negative electrode tab lead 15 extend upward. The positive electrode plate 12 has an uncoated region U where no positive electrode active material layer 12a exists along the upper end of the positive electrode plate 12. In this uncoated region U, the positive electrode tab lead 13 is welded and joined to the positive electrode current collector 12b, and an insulating tape 18 is attached to the uncoated region U so as to cover the welded and joined portion W. Also / Or, the negative electrode plate 14 has an uncoated region U where no negative electrode active material layer 14a exists along the upper end of the negative electrode plate 14. In this uncoated region U, the negative electrode tab lead 15 is welded and joined to the negative electrode current collector 14b, and an insulating tape 18 is attached to the uncoated region U so as to cover the welded and joined portion W. Thus, in the zinc secondary battery 10 of the upper tab type, by attaching the insulating tape 18 to the uncoated region U of the electrode plate 12 or 14 so as to cover the portion where the tab lead 13 or 15 is welded and joined, it is possible to make it difficult to cause a short circuit.

[0015] That is, as described above with reference to FIGS. 9A to 11, in the conventional upper tab type zinc secondary battery 110, the tab leads 113 or 115 are connected to the current collectors 112b or 114b by welding, and the tab leads 113 or 115 are connected to the electrode terminals 126 or 128. However, if the welding of the tab leads 113 or 115 to the current collectors 112b or 114b is insufficient, the tab leads 113 or 115 may be peeled off (or partially detached) from the current collectors 112b or 114b due to the load generated when aggregating the plurality of tab leads 113 or 115. For example, such peeling may also be caused by the load resulting from the expansion and contraction of the positive electrode plate 112 and / or the negative electrode plate 114 during charge and discharge. In such a case, there is a risk of the sharp end of the tab lead 113 or 115 piercing the hydroxide ion conductive separator 116 and / or the liquid retention member 117 in the vicinity, causing a short circuit S. On the other hand, in the zinc secondary battery 10 of the present invention, by attaching an insulating tape 18 to the uncoated region U of the electrode plate 12 or 14 so as to cover the portion where the tab lead 13 or 15 is welded, the occurrence of a short circuit can be made less likely. This is because by covering the welded portion of the tab lead 13 or 15 with the insulating tape 18, i) the welded portion W of the tab lead 13 or 15 is made less likely to be peeled off, and ii) even if the tab lead 13 or 15 is peeled off at the welded portion W and its tip contacts other components, as shown as peeling D in FIG. 4B, the tip of the tab lead 13 or 15 is protected by the insulating tape 18 and contacts other components (for example, the hydroxide ion conductive separator 16 or the liquid retention member 17). That is, the tip of the tab lead 13 or 15 becomes less likely to penetrate the hydroxide ion conductive separator 16 and the liquid retention member 17, and even if it penetrates them and contacts the electrode plate 12 or 14, the insulating tape 18 functions as an insulating material, so a short circuit is less likely to occur.

[0016] As shown in the figure example, it is preferable that the insulating tape 18 is applied to both the positive electrode plate 12 and the negative electrode plate 14, but it may be applied to only one of the positive electrode plate 12 and the negative electrode plate 14. Even in this case, it is possible to make it difficult to cause a short circuit due to the peeling of either the positive electrode tab lead 13 or the negative electrode tab lead 15. As the insulating tape 18, a commercially available insulating tape may be used and is not particularly limited. The insulating tape 18 typically includes a base material made of an insulating resin and an adhesive layer or an adhesive layer provided on the base material. Examples of the insulating resin include polypropylene. Insulating tape 18 The thickness of is preferably 30 to 70 μm, more preferably 40 to 60 μm. With such a thickness, it is possible to favorably fill the step between the positive electrode active material layer 12a and the positive electrode current collector 12b and the step between the negative electrode active material layer 14a and the negative electrode current collector 14b, and it becomes difficult for the upper end of the positive electrode active material layer 12a or the negative electrode active material layer 14a to be damaged. Therefore, it is preferable to use an insulating tape having a thickness that does not exceed the step between the positive electrode active material layer 12a and the positive electrode current collector 12b and the step between the negative electrode active material layer 14a and the negative electrode current collector 14b 18 .

[0017] 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 appropriately selected from known positive electrode materials according to 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. In this case, the positive electrode active material layer 12a may contain at least one additive selected from the group consisting of a silver compound, a manganese compound, and a titanium compound, thereby promoting a positive electrode reaction that absorbs hydrogen gas generated by a self-discharge reaction. Further, the positive electrode active material layer 12a may further contain cobalt. Cobalt is preferably contained in the positive electrode plate 12 in the form of cobalt oxyhydroxide. In the positive electrode active material layer 12a, cobalt functions as a conductive aid and contributes to an improvement in charge-discharge capacity. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode

[0018] The positive electrode plate 12 further includes a positive electrode current collector 12b. Preferred examples of the positive electrode current collector 12b include nickel porous substrates such as foamed nickel plates. In this case, for example, a positive electrode plate composed of a positive electrode / positive electrode current collector can be preferably produced by uniformly applying a paste containing an electrode active material such as nickel hydroxide on the nickel porous substrate and drying it. At that time, it is also preferable to perform a pressing process on the dried positive electrode plate (i.e., positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. When the positive electrode current collector 12b is a nickel porous substrate such as a foamed nickel plate, it may be processed into a tab shape by pressing the uncoated area of the positive electrode current collector 12b.

[0019] The positive electrode tab lead 13 is provided so as to extend from the end of the positive electrode plate 12. The positive electrode tab lead 13 may be made of a commercially available metal thin sheet and is not particularly limited. It is preferable that a plurality of positive electrode tab leads 13 are joined to one positive electrode terminal 26 or a member electrically connected thereto to form a positive electrode tab joint portion 30. By doing so, current collection can be performed with a simple configuration and high space efficiency, and it is also easy to connect to the positive electrode terminal 26. The joining of the positive electrode tab lead 13 to members such as the positive electrode current collector 12b and the positive electrode terminal 26 may be performed using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, and resistance welding.

[0020] As shown in FIG. 7, the positive electrode plate 12 has an uncoated region U where the positive electrode active material layer 12a does not exist along the upper end of the positive electrode plate 12. In the uncoated region U, the positive electrode tab lead 13 is welded and joined to the positive electrode current collector 12b. And an insulating tape 18 is attached to the uncoated region U so that the welded and joined portion W is covered with the insulating tape 18. With this configuration, as described above, it is possible to make it difficult to cause a short circuit due to peeling of the positive electrode tab lead 13. The insulating tape 18 is preferably attached to both surfaces of the positive electrode plate 12. In this case, the insulating tape 18 may be attached separately to one surface and the other surface of the positive electrode plate 12, or one insulating tape 18 may be folded back and attached to both surfaces of the positive electrode plate 12. In the latter case, it may be configured to wind one insulating tape 18 around at least one turn over both surfaces of the positive electrode plate 12. In this case, the insulating tape 18 and the positive electrode tab lead 13 are less likely to peel off. Preferably, 60% or more of the area of the uncoated region U (including the area of the holes if there are holes) on both surfaces of the positive electrode plate 12 is covered with the insulating tape, more preferably 70% or more, still more preferably 80% or more, and ideally 100%. By doing so, since the bonding area between the positive electrode current collector 12b and the insulating tape 18 increases, the insulating tape 18 is less likely to peel off.

[0021] Preferably, the lower end of the insulating tape 18 on the positive electrode plate 12 is located between the upper end P3 of the positive electrode active material layer and the lower end P2 of the positive electrode tab lead 13. In this case, since the lower end of the insulating tape 18 is located below the lower end P2 of the positive electrode tab lead 13, the tip of the positive electrode tab lead 13 is protected by the insulating tape 18, and the positive electrode tab lead 13 is less likely to peel off. Even if the positive electrode tab lead 13 is peeled off, it is difficult for a short circuit to occur. Also, since the lower end of the insulating tape 18 is located above the upper end P3 of the positive electrode active material layer 12a, it is possible to prevent a capacity loss. That is, when the insulating tape 18 covers the positive electrode active material layer 12a, a region that does not contribute to the reaction is formed and the battery capacity decreases. However, with the above configuration, the insulating tape 18 does not cover the positive electrode active material layer 12a, so such a problem can be avoided.

[0022] Insulating tapes 18 are attached to both sides of the uncoated area U of the positive electrode plate 12 such that the upper ends of the insulating tapes 18 are positioned above the upper end P1 of the positive electrode current collector 12b, and preferably, the upper end portions of the insulating tapes 18 protruding from the upper end P1 of the positive electrode current collector 12b are bonded to each other. By doing so, the end portion of the positive electrode current collector 12b can be protected, and thus, a short circuit caused by the end portion of the positive electrode current collector 12b can be prevented. More preferably, as shown in FIG. 8, insulating tapes 18 are attached to both sides of the uncoated area U of the positive electrode plate 12 such that the left and right ends of the insulating tapes 18 are positioned outside the left and right ends of the positive electrode current collector 12b, and the left and right end portions of the insulating tapes 18 protruding from the left and right ends of the positive electrode current collector 12b are bonded to each other. By doing so, even if the adhesive force between the positive electrode current collector 12b and the insulating tape 18 is low, the protruding portions of the insulating tape 18 over the three sides protruding from the upper end and the left and right ends of the positive electrode current collector 12b are joined to each other with a high adhesive force between the insulating tapes 18, so that peeling of the insulating tape 18 can be effectively prevented. Note that, since the contact area ratio of the positive electrode tab lead 13 and the insulating tape 18 is high (since the positive electrode tab lead 13 is typically made of a porous material), a high adhesive force can be inherently ensured.

[0023] The negative electrode plate 14 includes a negative electrode active material layer 14a. The negative electrode active material constituting the negative electrode active material layer 14a includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compound. Zinc may be contained in any form of zinc metal, zinc compound, and zinc alloy as long as it has suitable electrochemical activity for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate, etc., and a mixture of zinc metal and zinc oxide is more preferred. The negative electrode active material may be formed in a gel state or may be mixed with an electrolytic solution to form a negative electrode composite material. For example, a gelated negative electrode can be easily obtained by adding an electrolytic solution and a thickening agent to the negative electrode active material. Examples of the thickening agent include polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc., and polyacrylic acid is preferred because of its excellent chemical resistance to strong alkali.

[0024] 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% by mass of indium, 0.005 to 0.02% by mass of bismuth, and 0.0035 to 0.015% by mass of aluminum is preferable because it has an effect of suppressing hydrogen gas generation. In particular, indium and bismuth are advantageous in improving the discharge performance. The use of the zinc alloy as the negative electrode can suppress hydrogen gas generation and improve safety by reducing the self-dissolution rate in an alkaline electrolyte.

[0025] The shape of the negative electrode material is not particularly limited, but it is preferably in powder form, whereby the surface area is increased and high-current discharge can be accommodated. The average particle diameter of the preferable negative electrode material is in the range of 3 to 100 μm in the short diameter in the case of a zinc alloy. Within this range, since the surface area is large, it is suitable for high-current discharge, and it is easy to mix uniformly with the electrolyte and the gelling agent, and the handleability during battery assembly is also good.

[0026] The negative electrode plate 14 further includes a negative electrode current collector 14b. The negative electrode active material layer 14a may be disposed on both sides of the negative electrode current collector 14b, or may be disposed only on one side of the negative electrode current collector 14b. From the viewpoint of fixing the negative electrode active material to the current collector, it is preferable to use a metal plate having a plurality (or a large number) of openings as the negative electrode current collector 14b. Preferred examples of such a negative electrode current collector 14b include expanded metal, punched metal, and metal mesh, and combinations thereof. More preferably, copper expanded metal, copper punched metal, and combinations thereof, and particularly preferably copper expanded metal, may be mentioned. In this case, for example, a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (for example, polytetrafluoroethylene particles) is applied onto the copper expanded metal to preferably produce a negative electrode plate composed of a negative electrode / negative electrode current collector. At that time, it is also preferable to perform a pressing treatment on the dried negative electrode plate (that is, the negative electrode / negative electrode current collector) to prevent the electrode active material from falling off and to improve the electrode density. Note that expanded metal is a mesh-shaped metal plate obtained by expanding a metal plate while making slits in a staggered pattern using an expand manufacturing machine and forming the slits into a diamond shape or a tortoise shell shape. Punched metal, also called perforated metal, is a metal plate with holes made by punching. Metal mesh is a metal product having a wire mesh structure and is different from expanded metal and punched metal.

[0027] The negative electrode tab lead 15 is provided so as to extend from the end of the negative electrode plate 14 at a position that does not overlap with the positive electrode tab lead 13 (see FIG. 3). The negative electrode tab lead 15 is not particularly limited and may be a commercially available thin metal sheet. It is preferable that a plurality of negative electrode tab leads 15 are joined to one negative electrode terminal 28 or a member electrically connected thereto to form a negative electrode tab joint portion 32. By doing so, current collection can be performed with a simple configuration and high space efficiency, and it also becomes easier to connect to the negative electrode terminal 28. The joining of the negative electrode tab lead 15 to members such as the negative electrode current collector 14b and the negative electrode terminal 28 may be performed using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, and resistance welding.

[0028] As shown in FIG. 7, the negative electrode plate 14 has an uncoated region U where the negative electrode active material layer 14a does not exist along the upper end of the negative electrode plate 14, and the negative electrode tab lead 15 is welded and joined to the negative electrode current collector 14b in the uncoated region U. Then, an insulating tape 18 is attached to the uncoated region U so that the welded and joined portion W is covered with the insulating tape 18. With this configuration, as described above, it is possible to make it difficult to cause a short circuit due to peeling of the negative electrode tab lead 15. The insulating tape 18 is preferably attached to both surfaces of the negative electrode plate 14. In this case, the insulating tape 18 may be separately attached to one surface and the other surface of the negative electrode plate 14, or one insulating tape 18 may be folded back and attached to both surfaces of the negative electrode plate 14. In the latter case, it may be configured such that one insulating tape 18 is wound around at least one turn over both surfaces of the negative electrode plate 14. In this case, the insulating tape 18 and the negative electrode tab lead 15 are more difficult to peel off. It is preferable that 60% or more of the area of the uncoated region U (including the area of the holes if there are holes) on both surfaces of the negative electrode plate 14 is covered with the insulating tape, more preferably 70% or more, still more preferably 80% or more, and ideally 100%. By doing so, the bonding area between the negative electrode current collector 14b and the insulating tape 18 increases, so that the insulating tape 18 is less likely to peel off.

[0029] It is preferable that the lower end of the insulating tape 18 on the negative electrode plate 14 is located between the upper end P3 of the negative electrode active material layer 14a and the lower end P2 of the negative electrode tab lead 15. In this case, since the lower end of the insulating tape 18 is located below the lower end P2 of the negative electrode tab lead 15, the tip of the negative electrode tab lead 15 is protected by the insulating tape 18, and the negative electrode tab lead 15 is less likely to peel off. Even if the negative electrode tab lead 15 peels off, it is difficult to cause a short circuit. Also, the lower end of the insulating tape 18 is negative electrodeSince it will be located above the upper end P3 of the active material layer, capacity loss can be prevented. That is, when the insulating tape 18 covers the negative electrode active material layer 14a, a region that does not contribute to the reaction is formed and the battery capacity decreases. However, with the above configuration, the insulating tape 18 does not cover the negative electrode active material layer 14a, so such a problem can be avoided.

[0030] Insulating tapes 18 are attached to both sides of the uncoated region U of the negative electrode plate 14 such that the upper ends of the insulating tapes 18 are located above the upper end P1 of the negative electrode current collector 14b, and preferably, the upper end portions of the insulating tapes 18 protruding from the upper end P1 of the negative electrode current collector 14b are bonded to each other. By doing so, the end portion of the negative electrode current collector 14b can be protected, and thus a short circuit caused by the end portion of the negative electrode current collector 14b can be prevented. More preferably, as shown in FIG. 8, insulating tapes 18 are attached to both sides of the uncoated region U of the negative electrode plate 14 such that the left and right ends of the insulating tapes 18 are located outside the left and right ends of the negative electrode current collector 14b, and the left and right end portions of the insulating tapes 18 protruding from the left and right ends of the negative electrode current collector 14b are bonded to each other. By doing so, even if the adhesion force between the negative electrode current collector 14b and the insulating tape 18 is low, the protruding portions of the insulating tape 18 over the three sides protruding from the upper end and the left and right ends of the negative electrode current collector 14b are joined to each other with a high adhesion force between the insulating tapes 18, so that the peeling of the insulating tape 18 can be effectively prevented. For example, when the negative electrode current collector 14b is a porous material such as expanded metal, punched metal, and metal mesh, the adhesion area ratio with the insulating tape 18 is low, and thus the adhesion force between the negative electrode current collector 14b and the insulating tape 18 is low. However, even in such a case, the peeling of the insulating tape 18 can be effectively prevented by the high adhesion force in the protruding portions over the three sides. Note that, since the adhesion area ratio of the contact portion between the negative electrode tab lead 15 and the insulating tape 18 is high (because the negative electrode tab lead 15 is typically composed of a non-porous material), a high adhesion force can be inherently ensured.

[0031] The hydroxide ion conductive separator 16 is provided so as to isolate the positive electrode plate 12 and the negative electrode plate 14 in a hydroxide ion conductive manner. For example, as shown in FIGS. 4A, 4B, and 6, the positive electrode plate 12 and / or the negative electrode plate 14 (preferably the negative electrode plate 14) may be configured to be covered or wrapped by the hydroxide ion conductive separator 16. By doing so, it is possible to eliminate the complicated sealing joint between the hydroxide ion conductive separator 16 and the battery container, and to manufacture a nickel-zinc secondary battery (especially its laminated battery) capable of preventing the growth of zinc dendrites very simply and with high productivity. However, a simple configuration in which the hydroxide ion conductive separator 16 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may also be employed.

[0032] The hydroxide ion-conducting separator 16 is not particularly limited as long as it can isolate the positive electrode plate 12 and the negative electrode plate 14 so that hydroxide ions can conduct. Typically, it includes a hydroxide ion-conducting solid electrolyte and is a separator that selectively allows hydroxide ions to pass through by utilizing only the hydroxide ion conductivity. Preferred hydroxide ion-conducting solid electrolytes are layered double hydroxides (LDH) and / or LDH-like compounds. Therefore, the hydroxide ion-conducting separator 16 is preferably an LDH separator. As used herein, an "LDH separator" is defined as a separator containing LDH and / or LDH-like compounds that selectively allows hydroxide ions to pass through by utilizing only the hydroxide ion conductivity of LDH and / or LDH-like compounds. As used herein, an "LDH-like compound" is a hydroxide and / or oxide having a layered crystal structure similar to LDH, which may not be called LDH but is equivalent to LDH. However, in a broad sense, "LDH" can also be interpreted to include not only LDH but also LDH-like compounds. The LDH separator is preferably combined with a porous substrate. Therefore, the LDH separator preferably further includes a porous substrate, and LDH and / or LDH-like compounds are combined with the porous substrate in a form filled in the pores of the porous substrate. That is, a preferred LDH separator has LDH and / or LDH-like compounds blocking the pores of the porous substrate 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 LDH is incorporated throughout the thickness direction of the polymer material-made porous substrate. For example, known LDH separators as 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, still more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0033] It is preferable that not only the hydroxide ion conducting separator 16 but also the liquid retaining member 17 is interposed between the positive electrode plate 12 and the negative electrode plate 14. Then, as shown in FIGS. 4A, 4B, and 6, it is preferable that the positive electrode plate 12 and / or the negative electrode plate 14 is covered or wrapped by the liquid retaining member 17. However, a simple configuration in which the liquid retaining member 17 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may be used. In any case, by interposing the liquid retaining member 17, the electrolyte can be uniformly present between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conducting separator 16, and the transfer of hydroxide ions between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conducting separator 16 can be efficiently performed. The liquid retaining member 17 is not particularly limited as long as it can retain the electrolyte, but is preferably a sheet-like member. Preferred examples of the liquid retaining member 17 include non-woven fabric, water-absorbing resin, liquid-retaining resin, porous sheet, and various spacers. Particularly preferably, it is a non-woven fabric in terms of being able to produce a negative electrode structure with low cost and good performance. The liquid retaining member 17 or the non-woven fabric preferably has a thickness of 10 to 200 μm, more preferably 20 to 200 μm, still more preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. When the thickness is within the above range, a sufficient amount of electrolyte can be retained in the liquid retaining member 17 while suppressing the overall size of the positive electrode structure and / or the negative electrode structure in a compact and waste-free manner.

[0034] When the positive electrode plate 12 and / or the negative electrode plate 14 are covered or wrapped by the liquid retention member 17 and / or the separator 16, it is preferable that their outer edges are closed (excluding the sides where the positive electrode tab lead 13 and the negative electrode tab lead 15 extend). In this case, it is preferable that the closed sides of the outer edges of the liquid retention member 17 and / or the separator 16 are realized by bending the liquid retention member 17 and / or the separator 16, or by sealing the liquid retention members 17 and / or the separators 16 to each other. Preferable examples of the sealing method include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. In particular, since the LDH separator containing a porous substrate made of a polymer material has flexibility and is thus easy to bend, it is preferable to form the LDH separator in a long shape and bend it to form a state where one side of the outer edge is closed. Heat welding and ultrasonic welding may be performed using a commercially available heat sealer or the like. However, in the case of sealing the LDH separators to each other, it is preferable to perform heat welding and ultrasonic welding by sandwiching the outer peripheral portion of the liquid retention member 17 between the LDH separators constituting the outer peripheral portion, in terms of being able to perform more effective sealing. On the other hand, commercially available products may be used for adhesives, adhesive tapes, and sealing tapes. However, in order to prevent deterioration in the alkaline electrolyte, those containing an alkali-resistant resin are preferable. From this viewpoint, examples of preferable adhesives include epoxy resin-based adhesives, natural resin-based adhesives, modified olefin resin-based adhesives, and modified silicone resin-based adhesives. Among them, epoxy resin-based adhesives are more preferable in that they are particularly excellent in alkali resistance. Product examples of epoxy resin-based adhesives include epoxy adhesive Hysol (registered trademark) (manufactured by Henkel).

[0035] It is preferable that the outer edge of one side that becomes the upper end of the separator 16 is open. This upper open type configuration enables dealing with problems during overcharging in nickel-zinc batteries and the like. That is, when overcharged in a nickel-zinc battery or the like, oxygen (O2) can be generated at the positive electrode plate 12. However, since the LDH separator has a high degree of tightness such that it substantially allows only hydroxide ions to pass through, it does not allow O2 to pass through. In this regard, according to the upper open type configuration, in the battery case 20, O2 can be released above the positive electrode plate 12 and sent to the negative electrode plate 14 side through the upper open portion, whereby Zn of the negative electrode active material can be oxidized by O2 and returned to ZnO. By going through such an oxygen reaction cycle, the overcharge resistance can be improved by using the upper open type electrode laminate 11 in a sealed zinc secondary battery. Even when the outer edge of one side that becomes the upper end of the separator 16 or the liquid retention member 17 is closed, by providing air holes in a part of the closed outer edge, the same effect as the above open type configuration can be expected. For example, air holes may be opened after sealing the outer edge of one side that becomes the upper end of the LDH separator, or a part of the outer edge may not be sealed so that air holes are formed during sealing.

[0036] The electrolytic solution preferably contains an aqueous solution of an alkali metal hydroxide. Although the electrolytic solution is not shown in FIGS. 1 to 4B, this is because it spreads over the entire positive electrode plate 12 and negative electrode plate 14. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, etc., and potassium hydroxide is more preferable. In order to suppress the self-dissolution of zinc and / or zinc oxide, zinc compounds such as zinc oxide and zinc hydroxide may be added to the electrolytic solution. As described above, the electrolytic solution may be mixed with the positive electrode active material and / or the negative electrode active material and exist in the form of a positive electrode composite material and / or a negative electrode composite material. Also, the electrolytic solution may be gelled to prevent leakage of the electrolytic solution. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells, and polymers such as polyethylene oxide, polyvinyl alcohol, polyacrylamide, and starch are used.

[0037] The electrode laminate 11 is a laminate including a plurality of electrode layers. As shown in FIGS. 3, 4A, and 4B, the electrode laminate 11 includes a plurality of positive electrode plates 12, a plurality of negative electrode plates 14, and a plurality of separators 16, and is preferably in the form of a positive / negative electrode laminate in which the unit of positive electrode plate 12 / separator 16 / negative electrode plate 14 is repeated. That is, the zinc secondary battery 10 preferably includes a plurality of unit cells 10a each having a pair of positive electrode plate 12 and negative electrode plate 14 together with a hydroxide ion conductive separator 16, and thus a plurality of unit cells 10a form a multilayer cell as a whole. This is a configuration of a so-called assembled battery or laminated battery, which is advantageous in that a high voltage and a large current can be obtained.

[0038] The battery case 20 is preferably made of resin. The resin constituting the battery case 20 is preferably a resin having resistance to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, an ABS resin, or a modified polyphenylene ether, and even more preferably an ABS resin or a modified polyphenylene ether. The battery case 20 has an upper lid 20a. The battery case 20 (for example, the upper lid 20a) may have a pressure relief valve for discharging gas. Further, a case group in which two or more battery cases 20 are arranged may be housed in an outer frame to form a battery module.

[0039] LDH-like compound According to a preferred embodiment of the present invention, the LDH separator can contain an LDH-like compound. The definition of the LDH-like compound is as described above. Preferred LDH-like compounds are (a) a hydroxide and / or oxide having a layered crystal structure containing Mg and at least one element containing at least Ti selected from the group consisting of Ti, Y, and Al, or (b) (i) a hydroxide and / or oxide having a layered crystal structure containing Ti, Y, and optionally Al and / or Mg, and (ii) an additive element M which is at least one selected from the group consisting of In, Bi, Ca, Sr, and Ba, or (c) Hydroxides and / or oxides with a layered crystal structure containing Mg, Ti, Y, and optionally Al and / or In, and in (c) the LDH-like compound is present in the form of a mixture with In(OH)3.

[0040] According to a preferred embodiment (a) of the present invention, the LDH-like compound can be a hydroxide and / or oxide with a layered crystal structure containing Mg and at least one element selected from the group consisting of Ti, Y, and Al, including Ti. Therefore, a typical LDH-like compound is a double hydroxide and / or double oxide of Mg, Ti, optionally Y, and optionally Al. 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 the LDH-like compound preferably does not contain Ni. For example, the LDH-like compound may further contain Zn and / or K. By doing so, the ionic conductivity of the LDH separator can be further improved.

[0041] The LDH-like compound can be identified by X-ray diffraction. Specifically, when X-ray diffraction is performed on the surface of the LDH separator, peaks derived from the LDH-like compound are typically detected in the range of 5° ≤ 2θ ≤ 10°, more typically in the range of 7° ≤ 2θ ≤ 10°. As described above, LDH is a substance having an alternating layered structure in which exchangeable anions and H2O are present as an intermediate layer between stacked hydroxide basic layers. In this regard, when LDH is measured by X-ray diffraction method, a peak (i.e., the (003) peak of LDH) due to the crystal structure of LDH is originally detected at the position of 2θ = 11 - 12°. In contrast, when the LDH-like compound is measured by X-ray diffraction method, peaks are typically detected in the above range shifted to the low-angle side compared to the above peak position of LDH. Also, using 2θ corresponding to the peak derived from the LDH-like compound in X-ray diffraction, the interlayer distance of the layered crystal structure can be determined by Bragg's equation. The interlayer distance of the layered crystal structure constituting the LDH-like compound thus determined is typically 0.883 - 1.8 nm, more typically 0.883 - 1.3 nm.

[0042] The LDH separator according to the above aspect (a) preferably has an atomic ratio of Mg / (Mg + Ti + Y + Al) in the LDH-like compound determined by energy dispersive X-ray spectroscopy (EDS) of 0.03 to 0.25, more preferably 0.05 to 0.2. Further, 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. Furthermore, 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. And 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. When within the above range, the alkali resistance is further improved, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. By the way, the conventionally known LDH for the LDH separator has the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (wherein M 2+ is a divalent cation, M 3+ is a trivalent cation, 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 above atomic ratios in the LDH-like compound generally deviate from the above general formula of LDH. Therefore, it can be said that the LDH-like compound in this aspect generally has a different composition ratio (atomic ratio) from conventional LDH. Note that the EDS analysis is preferably performed by using an EDS analyzer (for example, X-act, manufactured by Oxford Instruments) to 1) capture an image at an acceleration voltage of 20 kV and a magnification of 5,000 times, 2) perform three-point analysis at intervals of about 5 μm in the point analysis mode, 3) repeat the above 1) and 2) once more, and 4) calculate the average value of a total of six points.

[0043] According to another preferred embodiment (b) of the present invention, the LDH-like compound can be a hydroxide and / or oxide having a layered crystal structure containing (i) Ti, Y, and optionally Al and / or Mg, and (ii) additive element M. Therefore, a typical LDH-like compound is a composite hydroxide and / or composite oxide of Ti, Y, additive element M, optionally Al, and optionally Mg. The additive element M is In, Bi, Ca, Sr, Ba, or a combination thereof. 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 the LDH-like compound preferably does not contain Ni.

[0044] For the LDH separator according to the above embodiment (b), the atomic ratio of Ti / (Mg + Al + Ti + Y + M) in the LDH-like compound 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. And 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 ranges, the alkaline resistance is further improved, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. By the way, the conventionally known LDH for the LDH separator has the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (wherein M 2+ is a divalent cation, M 3+ is a trivalent cation, and A n-It can be represented by a basic composition of an n-valent anion (where n is an integer of 1 or more, x is from 0.1 to 0.4, and m is 0 or more). In contrast, the atomic ratios in the LDH-like compound generally deviate from those in the above 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 performed using an EDS analyzer (for example, X-act, manufactured by Oxford Instruments) by: 1) capturing an image at an acceleration voltage of 20 kV and a magnification of 5,000 times, 2) performing point analysis at intervals of about 5 μm in point analysis mode and conducting three-point analysis, 3) repeating steps 1) and 2) one more time, and 4) calculating the average value of a total of six points.

[0045] According to yet another preferred embodiment (c) of the present invention, 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, and the LDH-like compound may exist in the form of a mixture with 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 In that can be contained in the LDH-like compound may not only be intentionally added to the LDH-like compound but also be unavoidably mixed into the LDH-like compound due to the formation of In(OH)3 or the like. 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 the LDH-like compound preferably does not contain Ni. By the way, a conventionally known LDH regarding the LDH separator has the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (wherein M 2+ is a divalent cation, M 3+ is a trivalent cation, and A n-It can be represented by a basic composition of (wherein 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 above 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.

[0046] The mixture according to the above aspect (c) contains not only the LDH-like compound but also In(OH)3 (typically composed of the LDH-like compound and In(OH)3). The inclusion of In(OH)3 can effectively improve the alkali resistance and dendrite resistance in the LDH separator. The content ratio of In(OH)3 in the mixture is preferably an amount that can improve the alkali resistance and dendrite resistance without substantially impairing the hydroxide ion conductivity of the LDH separator, and is not particularly limited. In(OH)3 may have a cubic crystal structure, or may have a structure in which the crystals of In(OH)3 are surrounded by the LDH-like compound. In(OH)3 can be identified by X-ray diffraction.

Claims

1. A positive electrode plate including a positive electrode active material layer and a positive electrode current collector, A positive electrode tab lead extending from an end of the positive electrode plate, A negative electrode plate including a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compound, and a negative electrode current collector, A negative electrode tab lead extending from an end of the negative electrode plate at a position not overlapping with the positive electrode tab lead, A hydroxide ion conductive separator that separates the positive electrode plate and the negative electrode plate so that hydroxide ions can be conducted, An electrolytic solution, A zinc secondary battery comprising: Each of the positive electrode plate, the positive electrode tab lead, the negative electrode plate, the negative electrode tab lead, and the hydroxide ion conductive separator is arranged vertically, and the positive electrode tab lead and the negative electrode tab lead extend upward, The positive electrode plate has an uncoated region where the positive electrode active material layer does not exist along the upper end of the positive electrode plate. In the uncoated region, the positive electrode tab lead is welded and joined to the positive electrode current collector, and an insulating tape is attached to the uncoated region so that the welded and joined portion is covered with the insulating tape. The insulating tape is attached to both surfaces of the uncoated region of the positive electrode plate such that the upper end of the insulating tape is positioned above the upper end of the positive electrode current collector, and the left and right ends of the insulating tape are positioned outside the left and right ends of the positive electrode current collector. Thereby, the upper end portions of the insulating tape protruding from the upper end of the positive electrode current collector are bonded to each other, and the left and right end portions of the insulating tape protruding from the left and right ends of the positive electrode current collector are bonded to each other, and / or The negative electrode plate has an uncoated region where the negative electrode active material layer does not exist along the upper end of the negative electrode plate. In the uncoated region, the negative electrode tab lead is welded and joined to the negative electrode current collector, and an insulating tape is attached to the uncoated region so that the welded and joined portion is covered with the insulating tape. The insulating tape is attached to both surfaces of the uncoated region of the negative electrode plate such that the upper end of the insulating tape is positioned above the upper end of the negative electrode current collector, and the left and right ends of the insulating tape are positioned outside the left and right ends of the negative electrode current collector. Thereby, the upper end portions of the insulating tape protruding from the upper end of the negative electrode current collector are bonded to each other, and the left and right end portions of the insulating tape protruding from the left and right ends of the negative electrode current collector are bonded to each other. A zinc secondary battery.

2. At least 60% of the area of the uncoated regions on both sides of the positive electrode plate is covered with the insulating tape, and / or at least 60% of the area of the uncoated regions on both sides of the negative electrode plate is covered with the insulating tape. The zinc secondary battery according to claim 1.

3. The lower end of the insulating tape on the positive electrode plate is located between the upper end of the positive electrode active material layer and the lower end of the positive electrode tab lead, and / or The lower end of the insulating tape on the negative electrode plate is located between the upper end of the negative electrode active material layer and the lower end of the negative electrode tab lead. The zinc secondary battery according to claim 1 or 2.

4. The positive electrode plate and / or the negative electrode plate is covered or wrapped by the hydroxide ion conductive separator. The zinc secondary battery according to claim 1 or 2.

5. Between the positive electrode plate and the negative electrode plate, not only the hydroxide ion conductive separator but also a liquid retention member is interposed. The zinc secondary battery according to claim 1 or 2.

6. The positive electrode plate and / or the negative electrode plate is covered or wrapped by the liquid retention member. The zinc secondary battery according to claim 5.

7. The hydroxide ion conductive separator is an LDH separator containing layered double hydroxide (LDH) and / or LDH-like compound. The zinc secondary battery according to claim 1 or 2.

8. The LDH separator further includes a porous substrate, and the LDH and / or LDH-like compound is compounded with the porous substrate in a form filled in the pores of the porous substrate. The zinc secondary battery according to claim 7.

9. The positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery forms a nickel-zinc secondary battery. The zinc secondary battery according to claim 1 or 2.

10. The positive electrode active material layer is an air electrode layer, whereby the zinc secondary battery forms an air-zinc secondary battery. The zinc secondary battery according to claim 1 or 2.

11. Including a plurality of unit cells each having a pair of the positive electrode plate and the negative electrode plate together with the hydroxide ion conductive separator, whereby the plurality of unit cells form a multilayer cell as a whole. The zinc secondary battery according to claim 1 or 2.

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