Alkaline secondary battery and manufacturing method therefor

Abstract

This alkaline secondary battery has a wound body in which a positive electrode and a negative electrode are wound in a state in which the positive electrode and negative electrode are layered upon one another with a separator therebetween. The separator includes a nonwoven fabric and a microporous film disposed on the nonwoven fabric, and the microporous film does not face the central space of the wound body.

Description

Alkaline secondary battery and its manufacturing method

[0001] The present invention relates to an alkaline secondary battery and a method for manufacturing the same.

[0002] Alkaline secondary batteries, such as nickel-metal hydride batteries and nickel-zinc batteries, are used in various electronic devices. Known alkaline secondary batteries have a structure in which a positive electrode and a negative electrode are wound together in a stacked state with a separator interposed therebetween, and the wound battery is enclosed in an outer can together with an alkaline electrolyte (see, for example, Patent Documents 1 and 2).

[0003] Among alkaline secondary batteries, nickel-zinc batteries have excellent input / output characteristics due to their high electromotive force. Furthermore, the zinc used as a material is less expensive than the hydrogen storage alloys used in nickel-metal hydride batteries. Therefore, nickel-zinc batteries are expected to be used in industrial and automotive applications.

[0004] On the other hand, in nickel-zinc batteries, zinc deposition occurs on the negative electrode during charging, resulting in the formation of dendrites (branched crystals). When dendrites grow due to repeated charge and discharge, they may penetrate the separator, causing a short circuit. To prevent short circuits caused by dendrites, a separator made by laminating a nonwoven fabric and a dendrite-resistant microporous film is used (see, for example, Patent Document 3).

[0005] JP 2002-42859 A JP 2014-216261 A JP 2023-144769 A

[0006] However, according to the investigations of the present inventors, when a separator in which a nonwoven fabric and a microporous film are laminated is used, there is a problem that poor winding is likely to occur when a wound body is produced.

[0007] FIG. 1A is a schematic enlarged view showing an example of a method for manufacturing a wound body 1, and FIG. 1B is a schematic enlarged cross-sectional view of the vicinity of a central space 1S of the wound body 1 obtained by the method of FIG. 1A.

[0008] 1A , wound body 1 is produced by placing negative electrode 2 on separator 4A formed by laminating nonwoven fabric 5A and microporous film 6A, placing positive electrode 3 on separator 4B formed by laminating nonwoven fabric 5B and microporous film 6B, and winding these layers around winding core 7 while stacking them, and then pulling out winding core 7. In the resulting wound body 1, microporous film 6A faces the central space 1S (see FIG. 1B ).

[0009] However, in the method of Figure 1A, when the winding core 7 is placed between the two separators 4A and 4B, at least the microporous film 6A of the separator 4A comes into contact with the winding core 7. Because the microporous film 6A does not slide easily on the surface of the winding core 7, the microporous film 6A is prone to cracking or breaking when the winding core 7 is pulled out after winding. This easily causes a short circuit between the positive electrode 2 and the negative electrode 3, resulting in a problem of a shortened cycle life of the battery. Such poor winding is particularly likely to occur when the microporous film is fixed to a nonwoven fabric.

[0010] The present invention has been made in view of the above circumstances, and has as its object to provide an alkaline secondary battery in which a decrease in cycle life due to poor winding is suppressed, and a method for manufacturing the same.

[0011] The present invention relates to the following alkaline secondary battery and method for producing the same.

[0012] [1] An alkaline secondary battery having a wound body in which a positive electrode and a negative electrode are stacked and wound with a separator interposed therebetween, the separator including a nonwoven fabric and a microporous film disposed on the nonwoven fabric, the microporous film not facing a central space of the wound body. [2] The alkaline secondary battery according to [1], wherein the microporous film is disposed at a position away from a position of the nonwoven fabric facing the central space. [3] The alkaline secondary battery according to [1], wherein a radially inner end of the microporous film protrudes from a radially inner end of the negative electrode, and the separator further includes a protective member covering a surface of the protruding microporous film. [4] The alkaline secondary battery according to any one of [1] to [3], wherein a radially inner end and a radially outer end of the microporous film are each fixed to the nonwoven fabric. [5] The alkaline secondary battery according to any one of [1] to [4], wherein the microporous film is disposed between the nonwoven fabric and the negative electrode. [6] The alkaline secondary battery according to any one of [1] to [5], wherein the separator further includes two other nonwoven fabrics disposed between the nonwoven fabric and the positive electrode, the two other nonwoven fabrics being disposed at positions corresponding to the radially inner end and the radially outer end of the positive electrode, respectively. [7] The alkaline secondary battery according to any one of [1] to [6], wherein the alkaline secondary battery is a nickel-zinc secondary battery. [8] A method for producing an alkaline secondary battery, comprising: a step of placing a winding core on a separator including a nonwoven fabric and a microporous film disposed on the nonwoven fabric so as not to contact the microporous film; a step of winding a laminate formed by stacking a positive electrode and a negative electrode with the separator interposed between them, around the winding core to obtain a wound body; and a step of pulling out the winding core from the wound body.[9] The method for producing an alkaline secondary battery according to [8], wherein the separators include a first separator on which the negative electrode is disposed and a second separator on which the positive electrode is disposed, the first separator includes a first nonwoven fabric and a first microporous film disposed on the first nonwoven fabric, and the second separator includes a second nonwoven fabric and a second microporous film disposed on the second nonwoven fabric; in the step of arranging a winding core, a negative electrode laminate in which the negative electrode is disposed on the first microporous film of the first separator and a positive electrode laminate in which the positive electrode is disposed on the second nonwoven fabric of the second separator are prepared, the winding core is disposed between the first separator and the second separator so that the winding core and the first microporous film do not come into contact with each other, and in the step of obtaining a wound body, the negative electrode laminate and the positive electrode laminate are wound around the winding core while being stacked.

[10] The method for producing an alkaline secondary battery according to [9], wherein, in the step of placing a winding core, the first microporous film is placed at a position away from one longitudinal end of the first nonwoven fabric by at least the outer circumferential length of the winding core.

[11] The method for producing an alkaline secondary battery according to [9] or

[10] , wherein, in the step of placing a winding core, one longitudinal end of the first microporous film protrudes beyond one longitudinal end of the negative electrode, and the protruding surface of the first microporous film is covered with a protective member.

[12] The method for producing an alkaline secondary battery according to [8], wherein the separator includes a first microporous film placed on the nonwoven fabric and a second microporous film placed on the nonwoven fabric with a gap between them, and the winding core has a holding part that holds the nonwoven fabric exposed in the gap, and in the step of placing the winding core, the nonwoven fabric exposed in the gap is held by the winding core, and in the step of obtaining a wound body, the negative electrode is placed on one surface of the first microporous film, and the positive electrode is placed on the back side of the nonwoven fabric surface on which the second microporous film is placed, and the separator is wound around the winding core.

[0013] According to the present invention, it is possible to provide an alkaline secondary battery in which a decrease in cycle life due to poor winding is suppressed, and a method for manufacturing the same.

[0014] FIG. 1A is a schematic cross-sectional view showing an example of a method for manufacturing a wound body, and FIG. 1B is a partially enlarged cross-sectional view of the vicinity of the center of the wound body obtained by the method of FIG. 1A. FIG. 2 is a partially cutaway perspective view of a nickel-zinc secondary battery according to embodiment 1. FIG. 3 is a schematic cross-sectional view of the battery of FIG. 1. FIG. 4 is a partially enlarged cross-sectional view of the vicinity of the center of the wound body of FIG. 3. FIG. 5A is a schematic plan view of a separator in an expanded state according to embodiment 1, FIG. 5B is a schematic bottom view, and FIG. 5C is a schematic cross-sectional view taken along line 5C-5C in FIG. 5A. FIG. 6 is a schematic cross-sectional view showing a method for manufacturing a wound body according to embodiment 1. FIG. 7 is a partially enlarged cross-sectional view of the vicinity of the center of a wound body according to embodiment 2. FIG. 8A is a schematic plan view of a separator in an expanded state according to embodiment 2, FIG. 8B is a schematic bottom view, and FIG. 8C is a schematic cross-sectional view taken along line 8C-8C in FIG. 8A. 9A to 9C are schematic cross-sectional views showing a method for manufacturing a wound body in embodiment 2. FIG. 10 is a schematic partially enlarged cross-sectional view showing a method for manufacturing a wound body in a modified example. FIG. 11 is a partially enlarged cross-sectional view of the vicinity of the center of a wound body in a modified example. FIG. 12 is a schematic partially enlarged cross-sectional view showing a method for manufacturing the wound body of FIG. 11.

[0015] First Embodiment (Configuration of Alkaline Secondary Battery) A nickel-zinc secondary battery will be described below as an example of an alkaline secondary battery according to one embodiment of the present invention.

[0016] Fig. 2 is a schematic perspective view showing a nickel-zinc secondary battery 10 according to embodiment 1, with parts cut away. Fig. 3 is a schematic cross-sectional view of the battery 10 of Fig. 2. Fig. 4 is an enlarged cross-sectional view of a part near the center of the wound body of Fig. 3. Note that in these figures, some of the constituent members of the wound body and the separator are omitted.

[0017] As shown in FIG. 2 , the nickel-zinc secondary battery 10 according to this embodiment is a so-called cylindrical battery, and includes an outer can 12, a sealing body 14, a wound body 16 (electrode group), an electrolyte (not shown), an upper insulating member 18, and a lower insulating member 20.

[0018] The outer can 12 is a container that houses the wound body 16, and in this embodiment, is a cylindrical container that is open at the top and has a bottom. The outer can 12 is electrically conductive, and its bottom wall 12A functions as a negative electrode terminal. The outer can 12 may be made of any material that is electrically conductive and corrosion-resistant to the electrolyte and the electrochemical reaction inside the battery, and is usually made of a metal material such as iron or steel.

[0019] The sealing body 14 is fixed to the opening of the outer can 12 via an insulating packing 22, and serves to seal the outer can 12 and also to form a positive electrode terminal. The sealing body 14 includes a cover plate 24, a valve body 26, and a positive electrode terminal 28.

[0020] The cover plate 24 is a conductive, disc-shaped member with a through-hole 24A in the center. The insulating gasket 22 is ring-shaped and surrounds the cover plate 24, and is interposed between the outer can 12 and the sealing body 14. The insulating gasket 22 is fixed to the opening edge 12C of the outer can 12 by crimping the opening edge 12C of the outer can 12. As a result, the opening of the outer can 12 is hermetically sealed by the cover plate 24 and the insulating gasket 22.

[0021] The valve body 26 is a rubber member and is disposed on the outer surface of the cover plate 24 so as to close the through-hole 24A.

[0022] The positive electrode terminal 28 is a metallic, flanged, cylindrical member that is electrically connected to the outer surface of the cover plate 24 so as to cover the valve body 26. The positive electrode terminal 28 presses the valve body 26 toward the cover plate 24. The positive electrode terminal 28 has a gas vent hole (not shown).

[0023] During normal operation, the through-hole 24A is airtightly closed by the valve body 26. On the other hand, when gas is generated inside the outer can 12 and the internal pressure increases, the valve body 26 is compressed by the internal pressure and opens the through-hole 24A. This allows gas to be released from inside the outer can 12 to the outside through the through-hole 24A and a gas vent hole (not shown) in the positive terminal 28. In other words, the through-hole 24A, the valve body 26, and the positive terminal 28 form a safety valve for the battery.

[0024] The wound body 16 is formed by winding a strip-shaped positive electrode 30 and a strip-shaped negative electrode 32 in a stacked state with a strip-shaped separator (in this embodiment, a first separator 34A or a second separator 34B) interposed therebetween (see FIG. 3).

[0025] A negative electrode 32 is disposed on the outermost peripheral surface of the wound body 16, and the negative electrode 32 is in contact with the inner wall surface of the outer can 12. That is, the negative electrode 32 and the outer can 12, which serves as a negative electrode terminal, are electrically connected to each other (see FIGS. 2 and 3).

[0026] On the other hand, a positive electrode lead 38 is connected to the positive electrode 30 of the wound body 16 (see FIG. 2 ). One end of the positive electrode lead 38 is connected to the positive electrode 30, and the other end is connected to the cover plate 24. As a result, the positive electrode 30 and the positive electrode terminal 28 are electrically connected to each other via the positive electrode lead 38 and the cover plate 24.

[0027] The upper insulating member 18 is disposed between the wound body 16 and the cover plate 24 so that the negative electrode 32 of the wound body 16 does not come into contact with the sealing body 14. The upper insulating member 18 also has a slit 18A for passing the positive electrode lead 36 therethrough.

[0028] The lower insulating member 20 is disposed between the wound body 16 and the bottom of the outer can 12. This prevents the positive electrode 30 of the wound body 16 from coming into contact with the inner wall surface of the outer can 12.

[0029] The electrolyte (not shown) is an alkaline electrolyte and is sealed in the outer can 12. The alkaline electrolyte is preferably an aqueous solution containing at least one of KOH, NaOH, and LiOH as a solute. The concentration (solute concentration) of the alkaline electrolyte is not particularly limited, but may be, for example, 5.0 N or more and 8.0 N or less (25 mass % or more and 45 mass % or less). In this embodiment, the alkaline electrolyte is preferably one in which zinc oxide is dissolved to a saturated concentration. This is to minimize the elution of zinc ions from the negative electrode into the electrolyte.

[0030] Next, the configuration of the wound body 16 will be described.

[0031] (Configuration of wound body 16) As described above, the wound body 16 is formed by winding a stack of the first separator 34A, the negative electrode 32, the second separator 34B, and the positive electrode 30 (see FIG. 3). Note that in the present embodiment, two separators (the first separator 34A and the second separator 34B) are used, but this is not limiting, and a single separator may be folded and used.

[0032] The first separator 34A includes a nonwoven fabric 35A (first nonwoven fabric) and a microporous film 36A (first microporous film) (see FIG. 4). The second separator 34B includes a nonwoven fabric 35B (second nonwoven fabric) and a microporous film 36B (second microporous film). Unlike the wound body shown in FIG. 1B, in the wound body 16 according to this embodiment, neither the microporous film 36A of the first separator 34A nor the microporous film 36B of the second separator 34B faces the central space 16S of the wound body 16 (see FIG. 4).

[0033] The central space 16S of the wound body 16 is a portion where the winding core was present when the wound body 16 was produced (see FIG. 4 ). In the present embodiment, the central space 16S is a space surrounded by the opposing nonwoven fabrics 35A and 35B at the radially innermost side, and is a space formed by pulling out the winding core after the first separator 34A, the negative electrode 32, the second separator 34B, and the positive electrode 30 are wound around the winding core.

[0034] For example, the microporous film 34A not facing the central space 16S means that the surface 36c of the microporous film 36A is not exposed to the central space 16S (see FIG. 4 and FIG. 5C described later). In this embodiment, the microporous film 36A is disposed at a position away from the position of the nonwoven fabric 35A facing the central space 16S (in FIG. 4, the end 35a of the nonwoven fabric 35A on the central space 16S side). As a result, the microporous film 36A does not face the central space 16S.

[0035] As described below, such a wound body 16 can be obtained by, when producing the wound body 16, placing the winding core 44 on the first separator 34A and the second separator 34B so that the winding core 44 does not come into contact with the microporous films 36A and 36B (see FIG. 6 described below).

[0036] Each member included in the wound body 16 will be described below.

[0037] (1) Positive Electrode 30 The positive electrode 30 includes a positive electrode current collector and a positive electrode mixture.

[0038] The positive electrode current collector can be, for example, a metal foil, a mesh-like, sponge-like, fibrous, or felt-like porous metal, a punched metal, or an expanded metal. The material of the positive electrode current collector may be any metal material that is stable even at the reaction potential of the positive electrode, such as nickel or stainless steel, and preferably nickel. That is, the positive electrode current collector can be, for example, nickel foam.

[0039] The positive electrode mixture is held by a positive electrode current collector and contains a positive electrode active material, such as nickel hydroxide, which may contain at least one of cobalt (Co), zinc (Zn), and cadmium (Cd) as a solid solution.

[0040] The positive electrode mixture may further contain a positive electrode additive and a binder.

[0041] Examples of positive electrode additives include yttrium oxide; cobalt compounds such as cobalt oxide, metallic cobalt, and cobalt hydroxide; zinc compounds such as metallic zinc, zinc oxide, and zinc hydroxide; rare earth compounds such as erbium oxide; and niobium oxide.

[0042] The binder may be any binder that is stable even at the reaction potential of the positive electrode, such as hydroxypropyl cellulose, carboxymethyl cellulose (CMC), sodium polyacrylate, or a fluorine-based polymer (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), etc.).

[0043] (2) Negative Electrode 32 The negative electrode 32 includes a negative electrode current collector and a negative electrode mixture.

[0044] The negative electrode current collector may be a non-porous current collector such as a metal foil, or may be a porous current collector such as a mesh-like, sponge-like, fibrous, or felt-like metal porous body, punched metal, or expanded metal. The material of the negative electrode current collector may be any metal material that is stable even at the reaction potential of the negative electrode, including copper, copper alloys (e.g., brass), and iron, and is preferably copper. That is, the negative electrode current collector is preferably copper foil.

[0045] The negative electrode mixture is held by the negative electrode current collector and contains a negative electrode active material. The negative electrode active material includes at least one of zinc, a zinc alloy, and a zinc-containing compound. Metals constituting the zinc alloy include zinc, bismuth, aluminum, indium, and the like. Examples of zinc-containing compounds include zinc oxide (type 1 / type 2 / type 3), zinc hydroxide, zinc sulfide, tetrahydroxyzinc ion salts, zinc halides, zinc carboxylate compounds such as zinc acetate, zinc tartrate, and zinc oxalate, magnesium zincate, calcium zincate, barium zincate, zinc borate, zinc silicate, zinc aluminate, zinc fluoride, zinc carbonate, zinc bicarbonate, zinc nitrate, and zinc sulfate. Among these, the negative electrode active material preferably contains zinc oxide as a primary component. "Containing zinc oxide as a primary component" refers to, for example, an amount of 50% by mass or more relative to the total mass of the negative electrode active material. The negative electrode active material preferably further contains zinc (metallic zinc). Zinc can serve as both a discharge reserve and a conductive material.

[0046] The negative electrode mixture may further contain a negative electrode additive and a binder.

[0047] The negative electrode additive may reduce the dissolution of the negative electrode active material into the electrolyte. Examples of such negative electrode additives include bismuth oxide, bismuth hydroxide, indium oxide, indium hydroxide, potassium oxalate, and hydrates thereof. For example, potassium oxalate and hydrates thereof dissociate into oxalate ions when dissolved in the electrolyte. As a result, zinc ions dissolved in the electrolyte form a poorly soluble salt with the oxalate ions, covering the surface of the negative electrode active material, thereby reducing contact between the metallic zinc of the negative electrode active material and the electrolyte. This may reduce the likelihood of self-discharge.

[0048] The binder may be any binder that is stable even at the reaction potential of the negative electrode. Examples of such binders include hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, sodium polyacrylate, polyimide, polyamideimide, polyamide, styrene-butadiene rubber, polyethylene oxide, etc. Among these, styrene-butadiene rubber is preferred from the viewpoints of high binding effect and alkali resistance.

[0049] (3) First Separator 34A, Second Separator 34B FIG. 5A is a schematic plan view of the first separator 34A in an expanded state, FIG. 5B is a schematic bottom view, and FIG. 5C is a schematic cross-sectional view taken along line 5C-5C in FIG. 5A.

[0050] (3.1) First Separator 34A As described above, the first separator 34A includes the nonwoven fabric 35A and the microporous film 36A. The first separator 34A may further include two other nonwoven fabrics 37A (see FIGS. 5A and 5C).

[0051] (3.1.1) Nonwoven Fabric 35A The material of the nonwoven fabric 35A is not particularly limited and may be a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate or polybutylene terephthalate, or a thermoplastic resin such as polyphenylene sulfide. Among these, polyolefin is preferred, and polypropylene is more preferred, from the viewpoints of strength and shutdown characteristics.

[0052] The nonwoven fabric 35A may be subjected to a hydrophilization treatment. The type of hydrophilization treatment is not particularly limited, and may be, for example, a sulfonation treatment using sulfuric acid or fuming sulfuric acid. The sulfonation treatment is a treatment in which the nonwoven fabric is immersed in concentrated sulfuric acid for a certain period of time to sulfonate the surface of the nonwoven fabric (to provide sulfonic acid groups), thereby making the nonwoven fabric more easily wettable.

[0053] The basis weight of the nonwoven fabric 35A is not particularly limited, but is, for example, 20 g / m ２ 70g / m or more ２ The basis weight can be 70 g / m or less. ２When the weight per unit area is 20 g / m or less, the ion conductivity can be more easily increased and the internal resistance can be more unlikely to increase. ２ When the ratio is equal to or greater than this, short circuits caused by dendrites can be further suppressed. The basis weight can be calculated by determining the weight per unit area.

[0054] The thickness of the nonwoven fabric 35A is not particularly limited, but is preferably, for example, 50 μm or more and 160 μm or less.

[0055] (3.1.2) Microporous film 36A The microporous film 36A is disposed on one surface of the nonwoven fabric 35A (in this embodiment, the surface on which the negative electrode 32 is disposed) (see FIG. 5C ). That is, the microporous film 36A is disposed between the nonwoven fabric 35A and the negative electrode 32.

[0056] In this embodiment, the microporous film 36A is disposed at a position away from one longitudinal end 35a of the nonwoven fabric 35 (the end 35a on the central space 16S side in FIG. 4) (see FIG. 5B). Specifically, the microporous film 36A is disposed at a position L away from the end 35a of the nonwoven fabric 35A (see FIG. 5B). L is preferably equal to or greater than the outer circumferential length of the winding core. This allows the winding core to be disposed on the first separator 34 so that the winding core and the microporous film 36A do not come into contact with each other in the winding core disposing step described below. For example, when the cross section of the winding core is a perfect circle, the outer circumferential length ρ of the winding core can be calculated using the following formula: ρ=πR (R: winding core diameter, π: circumference ratio).

[0057] The microporous film 36A may or may not be fixed to the nonwoven fabric 35A. From the viewpoint of preventing misalignment during winding, the microporous film 36A is preferably fixed to the nonwoven fabric 35A (see FIG. 5B ). The microporous film 36A may be fixed at any position, but from the viewpoint of preventing ion permeability from being impaired, it is preferably fixed at two longitudinal ends 36a and 36b of the microporous film 36A (see fixing portion H in FIGS. 5A and 5B ). The method for fixing the microporous film 36A is not particularly limited, and may be, for example, heat welding.

[0058] The material of the microporous film 36A is not particularly limited, and the same material as the nonwoven fabric 35A can be used. Among them, olefin resins such as polyethylene and polypropylene are preferable. The microporous film 36A may be hydrophilized as described above.

[0059] The thickness of the microporous film 36A is not particularly limited, but may generally be thinner than the nonwoven fabric 35A, and may be, for example, 5 μm or more and 80 μm or less.

[0060] (3.1.3) Other Nonwoven Fabrics 37A Two other nonwoven fabrics 37A are arranged on the other surface of nonwoven fabric 35A (in this embodiment, the surface on which positive electrode 30 is arranged) at positions corresponding to two longitudinal ends 30a and 30b of positive electrode 30 (see FIG. 5C ). That is, other nonwoven fabric 37A is arranged between nonwoven fabric 35A and positive electrode 30. This can further prevent damage to nonwoven fabric 35A due to burrs on the two ends 30a and 30b of positive electrode 30. Note that other nonwoven fabrics 37A may be used according to the purpose, and may not be used, and even if used, the number and arrangement of other nonwoven fabrics 37A are not limited to those described above.

[0061] The other nonwoven fabric 37A may or may not be fixed to the nonwoven fabric 35A. From the viewpoint of making it more difficult for the first separator 34A to be misaligned with respect to the positive electrode 30, the other nonwoven fabric 37A is preferably fixed to the nonwoven fabric 35A (see fixing portion H in FIGS. 5A and 5C ). The fixing method of the other nonwoven fabric 37A may also be thermal welding, as described above.

[0062] The material and physical properties of the other nonwoven fabric 37A can be the same as or similar to the material and physical properties of the nonwoven fabric 35A described above, and therefore detailed description thereof will be omitted. The material and physical properties of the other nonwoven fabric 37A may be the same as or different from the material and physical properties of the nonwoven fabric 35A. For example, the thickness of the other nonwoven fabric 37A may be thinner than the thickness of the nonwoven fabric 35A. Furthermore, the basis weight of the other nonwoven fabric 37A may be smaller than the basis weight of the nonwoven fabric 35A.

[0063] (3.2) Second Separator 34B The second separator 34B includes a nonwoven fabric 35B (second nonwoven fabric) and a microporous film 36B (second microporous film), and preferably further includes two other nonwoven fabrics 37B.

[0064] The nonwoven fabric 35B, the microporous film 36B, and the other nonwoven fabric 37B can be the same as or similar to the nonwoven fabric 35A, the microporous film 36A, and the other nonwoven fabric 37A of the first separator 34A described above, and detailed description thereof will be omitted.

[0065] (Method of Manufacturing Nickel-Zinc Secondary Battery 10) Hereinafter, a method of manufacturing the nickel-zinc secondary battery 10 will be described with reference to the drawings. Fig. 6 is a schematic cross-sectional view showing a method of manufacturing the wound body 16 in this embodiment.

[0066] The above-described nickel-zinc secondary battery can be manufactured, for example, through the steps of: 1) placing the winding core 44 on the separators (first separator 34A, second separator 34B) so that the winding core 44 does not come into contact with the microporous films (microporous films 36A and 36B); 2) winding the positive electrode 30 and the negative electrode 32, stacked with the separator interposed between them, around the winding core 44 to obtain a wound body; and 3) pulling out the winding core 44 from the wound body.

[0067] In this embodiment, first, the negative electrode 32 is placed on the microporous film 36A of the first separator 34A (see FIG. 6 ), thereby obtaining a negative electrode laminate 40 including the nonwoven fabric 35A, the microporous film 36A placed on the nonwoven fabric 35A, and the negative electrode 32 placed on the microporous film 36A.

[0068] Similarly, the positive electrode 30 is disposed on the nonwoven fabric 35B of the second separator 34B (see FIG. 6 ), thereby obtaining a positive electrode laminate 42 including the microporous film 36B, the nonwoven fabric 35B disposed on the microporous film 36B, and the positive electrode 30 disposed on the nonwoven fabric 35B.

[0069] Next, the winding core 44 is placed between the first separator 34A of the negative electrode laminate 40 and the second separator 34B of the positive electrode laminate 42 (see FIG. 6 ). Note that the winding core 44 may have grooves (or irregularities) formed on its surface to appropriately prevent slippage. For example, the cross-sectional shape of the winding core 44 perpendicular to the axial direction is not limited to a circle or an ellipse, and may also be a polygon (for example, a pointed star).

[0070] Specifically, the negative electrode stack 40 and the inverted positive electrode stack 42 are arranged alternately (see FIG. 6 ). That is, in plan view, the first separator 34A and the second separator 34B are arranged such that the ends near the winding start sides of the first separator 34A and the second separator 34B overlap each other.

[0071] Here, the microporous film 36A of the first separator 34A of the negative electrode laminate 40 is disposed on the winding core 44 side, but is disposed at a position away from the end 35a of the nonwoven fabric 35A by at least the outer circumferential length of the winding core 44 (see FIG. 6 ). Therefore, even when the winding core 44 is disposed on the first separator 34A, the winding core 44 does not come into contact with the microporous film 36A.

[0072] On the other hand, the microporous film 36B of the second separator 34B of the positive electrode laminate 42 is not disposed on the side of the winding core 44. Therefore, even if the winding core 44 is disposed on the second separator 34B, the winding core 48 does not come into contact with the microporous film 36B either.

[0073] This allows the winding core 44 to be positioned between the first separator 34A and the second separator 34B so that the winding core 44 does not come into contact with either the microporous films 36A or 36B (see FIG. 6).

[0074] 2) Step of Obtaining a Wound Body Next, the negative electrode laminate 40 and the positive electrode laminate 42 are wound around a winding core 44 while being stacked (see FIG. 6).

[0075] Specifically, as the winding core 44 rotates, the negative electrode laminate 40, which includes the first separator 34A and the negative electrode 32, is wound around the outer peripheral surface of the winding core 44 from one side (the right side in FIG. 6 ) of the winding core 44. Meanwhile, the positive electrode laminate 42, which includes the second separator 34B and the positive electrode 30, is wound around the outer peripheral surface of the winding core 44 from the other side (the left side in FIG. 6 ) of the winding core 44. As a result, the first separator 34A, the negative electrode 32, the second separator 34B, and the positive electrode 30 are wound around the winding core 44 in this stacked state, thereby obtaining a wound body.

[0076] 3) Step of Pulling Out the Winding Core Then, the winding core 44 is pulled out from the obtained wound body, whereby the wound body 16 can be obtained.

[0077] (Function) In the present embodiment, in step 1), the microporous film 36A of the first separator 34A is positioned away from the end 35a of the nonwoven fabric 35A, so that the winding core 44 does not come into contact with either the microporous films 36A or 36B (see FIG. 6 ). Therefore, when winding in step 2) or when pulling the winding core 44 out of the wound body in step 3), damage to the microporous films 36A and 36B by the winding core 44 can be prevented. This prevents winding defects and the resulting short circuits.

[0078] In FIG. 6, the end 36a of the microporous film 36A does not protrude from the end 32a of the negative electrode 32, but it may protrude slightly from the end 32a of the negative electrode 32 as long as the effects of the present invention are not impaired.

[0079] [Embodiment 2] Fig. 7 is a partially enlarged cross-sectional view of the vicinity of the center of a wound body in embodiment 2. Fig. 8A is a schematic plan view of a separator in an unfolded state in embodiment 2, Fig. 8B is a schematic bottom view, and Fig. 8C is a schematic cross-sectional view taken along line 8C-8C in Fig. 8A.

[0080] The battery 10 according to the second embodiment is configured similarly to the battery 10 according to the first embodiment, except that the battery 10 according to the second embodiment has a wound body 16 made using a single separator 34 with a different configuration instead of two separators (first separator 34A, second separator 34B). Therefore, the same components as those in the battery 10 according to the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0081] (Configuration of wound body 16) In the present embodiment, the separator 34 includes a nonwoven fabric 35, two microporous films 36A and 36B (a first microporous film and a second microporous film), and four other nonwoven fabrics 37 (see FIGS. 7 and 8C). As shown in FIG. 7, near the central space 16S of the wound body 16, both of the microporous films 36A and 36B are disposed at positions away from the position facing the central space 16S of the nonwoven fabric 35. As a result, neither of the microporous films 36A nor 36B faces the central space 16S of the wound body 16.

[0082] In this embodiment, the central space 16S is a space formed by pulling out the winding core having the holding portion. In Fig. 7, this is the space surrounded by the nonwoven fabric 35 at the radially innermost position, with the bent portion sandwiched therebetween.

[0083] The two microporous films 36A and 36B are arranged on one surface of the nonwoven fabric 35 (in this embodiment, the surface on which the negative electrode 32 is arranged) with a gap 46 interposed therebetween in the longitudinal direction of the nonwoven fabric 35 (see FIG. 8A ). The nonwoven fabric 35 is exposed in the gap 46. The longitudinal length of the gap 46 may be the same as or longer than L, which will be described later.

[0084] The longitudinal length of the gap 46 is preferably equal to or greater than the outer circumferential length of the winding core 44 .

[0085] Of the two microporous films 36A and 36B, at least the microporous film 36A on the side in contact with the winding core 44 is positioned at a distance L from the winding start position P of the nonwoven fabric 35A exposed in the gap 46 (see FIG. 8A ). L may be equal to or greater than (the length of the portion where the exposed nonwoven fabric 35 is in contact with the holding portion 44a of the winding core 44 + ½ the outer circumferential length of the winding core 44), and is more preferably equal to or greater than the outer circumferential length of the winding core 44.

[0086] The four other nonwoven fabrics 37 are arranged on the other surface of the nonwoven fabric 35 (in this embodiment, the surface on which the positive electrode 30 is arranged) at positions corresponding to the two ends 30a, 30b on one surface of the positive electrode 30 and the two ends (not shown) on the other surface (see Figure 9C).

[0087] The nonwoven fabric 35, the microporous films 36A and 36B, and the other nonwoven fabric 37 may be the same as the nonwoven fabric 35A, the microporous films 36A and 36B, and the other nonwoven fabric 37A in the first embodiment, respectively.

[0088] 9A to 9C are schematic cross-sectional views showing a method for manufacturing a wound body in embodiment 2. In this embodiment, a winding core having a holding portion 44a that holds the nonwoven fabric 35 exposed in the gap 46 is used as the winding core 44. The winding core 44 may have a split groove as the holding portion 44a (a so-called split pin), or may be sandwiched between two members.

[0089] Step 1) (Step of Placing the Winding Core) First, the nonwoven fabric 35 exposed in the gap 46 of the separator 34 is held by the holding portion 44a of the winding core 44 (see FIGS. 9A and 9B).

[0090] Step 2) (winding step) Next, the negative electrode 32 is placed on the microporous film 36A, and the winding core 44 is rotated to fold the separator 34 so that the microporous film 36B contacts the negative electrode 32 (so that the two microporous films 36A and 36B sandwich the negative electrode 32). The separator 34 is then wound around the winding core 44 with the positive electrode 30 placed on the back side of the surface of the folded nonwoven fabric 35 on which the microporous film 36B is placed (see FIG. 9C ).

[0091] Step 3) (Step of Pulling Out the Winding Core) Then, the winding core 44 is pulled out from the obtained wound body, thereby obtaining the wound body 16.

[0092] (Operation) In the present embodiment, when separator 34 is held by winding core 44 in step 1), winding core 44 does not come into contact with either microporous films 36A or 36B. Therefore, as in the first embodiment, when winding core 44 is pulled out from the wound body in step 3), damage to microporous films 36A and 36B by winding core 44 can be prevented. Therefore, poor winding and the resulting short circuit can be prevented.

[0093] [Modifications] The configuration of the battery according to the present invention and the manufacturing method thereof are not limited to those shown in the above embodiment.

[0094] Fig. 10 is a schematic, partially enlarged cross-sectional view showing a method for manufacturing a wound body according to a modified example. For example, as shown in Fig. 10, the microporous film 36B of the second separator 34B is not disposed on the side that contacts the winding core 44. Therefore, the microporous film 36B does not need to be disposed at a position away from the end 35a of the nonwoven fabric 35B, and may be disposed so that the end 35a of the nonwoven fabric 35B and the end 36a of the microporous film 36B overlap (see Fig. 10). Similarly, in the second embodiment, the microporous film 36B in Fig. 9B is not disposed on the side that contacts the winding core 44, and therefore the microporous film 36B may be disposed closer to the winding core 44 (Fig. 9B).

[0095] In addition, in the above-described first and second embodiments, the microporous films 36A and 36B are not disposed in the portions that come into contact with the winding core 44, but the present invention is not limited to this.

[0096] Fig. 11 is a partially enlarged cross-sectional view of the vicinity of the central space 16S of the wound body 16 according to a modified example. Fig. 12 is a schematic cross-sectional view showing a method for manufacturing the wound body 16 of Fig. 11. As shown in Fig. 11, a radially inner end 36a of the microporous film 36A may protrude beyond a radially inner end 32a of the negative electrode 32. In this case, the surface of the protruding portion of the microporous film 36A (hereinafter also referred to as "protruding portion 36d") may be covered with a folded nonwoven fabric 35A (protective member).

[0097] To manufacture such a wound body, in the step of placing the winding core 44, as shown in Fig. 12 , the end 35a of the nonwoven fabric 35A is folded back so as to cover the surface of the microporous film 36A, and the winding core 44 is placed on the folded back nonwoven fabric 35A. This prevents the winding core 44 from coming into contact with the protruding portion 36d of the microporous film 36A when the winding core 44 is placed on the separator 34.

[0098] 11 and 12, nonwoven fabric 35A is used as the protective member, but this is not limiting. The protective member may be any material that has low friction with the surface of the winding core 44, preferably nonwoven fabric. The nonwoven fabric used as the protective member may be the same as nonwoven fabric 35A. For example, a nonwoven fabric other than nonwoven fabric 35A may be used as the protective member. Similarly, in the second embodiment, a protective member may be disposed instead of providing gap 46.

[0099] In the above embodiment, the separator has one nonwoven fabric and one microporous film, but the present invention is not limited to this. Two or more nonwoven fabrics and two or more microporous films may be used.

[0100] Furthermore, in the above embodiment, an example of a cylindrical nickel-zinc secondary battery is shown, but the present invention is not limited to this, and a prismatic nickel-zinc secondary battery may also be used.

[0101] Furthermore, in the above embodiment, an example of a nickel-zinc secondary battery is shown, but the present invention is not limited to a secondary battery that uses an alkaline aqueous solution as the electrolyte, and may be a nickel-metal hydride secondary battery, a nickel-cadmium secondary battery, or the like.

[0102] 1. Preparation of separator 1-1. Components of separator (nonwoven fabric X) Polypropylene nonwoven fabric (thickness 140 μm, basis weight 62 g / m ２ )

[0103] (Microporous Film) A polypropylene microporous film (thickness: 25 μm, air permeability: 620 sec / 100 cc) was used. The air permeability of the microporous film is measured as the Gurley value in accordance with JIS L1096 (ISO 5636-5).

[0104] (Auxiliary nonwoven fabric Y) Polypropylene nonwoven fabric (thickness 110 μm, basis weight 45 g / m ２ ) was used.

[0105] 1-2. Preparation of Separator (Preparation of Separator 1) A microporous film was placed on one side of nonwoven fabric X at a distance equal to the outer diameter ρ of the winding core from one end (winding start position) of nonwoven fabric X in the longitudinal direction. The outer diameter ρ of the winding core was calculated using the following formula. R was measured using a vernier caliper. ρ = πR (R: winding core diameter, π: circumference constant). Then, the microporous film was heat-welded to nonwoven fabric X at two ends in the longitudinal direction (see FIG. 5B ).

[0106] Two auxiliary nonwoven fabrics Y were placed on the other surface of the nonwoven fabric X, covering the entire surface including the positions corresponding to the two longitudinal ends of the positive electrode, and were heat-welded (see FIG. 5A).

[0107] (Preparation of Separator 2) Separator 2 was prepared in the same manner as separator 1, except that a microporous film was placed on one surface of nonwoven fabric X at one end of nonwoven fabric X in the longitudinal direction (the winding start position).

[0108] (Preparation of Separator 3) Separator 3 was prepared in the same manner as Separator 1, except that a microporous film was not used.

[0109] 2. Battery Fabrication [Example 1] (Fabrication of Positive Electrode) 100 parts by weight of nickel hydroxide powder prepared as a positive electrode active material was mixed with 25 parts by weight of cobalt hydroxide powder, 0.5 parts by weight of yttrium oxide powder, 0.5 parts by weight of zinc oxide powder, 0.3 parts by weight of niobium oxide powder, and 50.0 parts by weight of water containing 0.2% by weight of hydroxypropyl cellulose powder as a thickener, and kneaded to prepare a positive electrode mixture slurry. This positive electrode active material slurry was filled into foamed nickel, dried, and then rolled with a rolling mill. This was cut to a predetermined size to prepare a positive electrode with a capacity of 2000 mAh per sheet.

[0110] (Preparation of Negative Electrode) 100 parts by weight of zinc oxide powder, 25 parts by weight of zinc powder, 3 parts by weight of bismuth oxide powder, 2 parts by weight of potassium oxalate monohydrate, 4 parts by weight of styrene-butadiene rubber powder as a binder, 1 part by weight of hydroxypropyl cellulose powder as a thickener, and 100 parts by weight of water were prepared. Then, these zinc oxide powder, zinc powder, bismuth oxide powder, potassium oxalate monohydrate, styrene-butadiene rubber powder, hydroxypropyl cellulose powder, and water were mixed in an environment of 25 ° C. to prepare a negative electrode active material slurry. This negative electrode active material slurry was coated on the entire surface of tin-plated non-porous copper foil, dried, and then rolled with a rolling mill. This was cut to a predetermined size to prepare a negative electrode with a capacity of 4500 mAh per sheet.

[0111] (Preparation of Electrolyte Solution) An aqueous solution containing 30 mass % of potassium hydroxide was saturated with zinc oxide to prepare an electrolyte solution.

[0112] (Fabrication of Battery) As shown in FIG. 6 , a wound body was fabricated using the above-fabricated positive electrode, negative electrode, and two separators 1. First, two separators 1 were prepared. A negative electrode was placed on one surface (the surface on which the microporous film was laminated) of the first separator 1 to form a negative electrode laminate. A positive electrode was placed on the other surface (the surface on which the auxiliary nonwoven fabric Y was laminated) of the second separator 1 to form a positive electrode laminate. Next, a winding core was placed between the separator of the negative electrode laminate and the separator of the positive electrode laminate as shown in FIG. 6 . A winding core with grooves on its surface was used. At this winding start position, the winding core was in contact with the nonwoven fabric X of the negative electrode laminate and the nonwoven fabric X of the positive electrode laminate, respectively, and neither was in contact with the microporous film. Then, the winding core was rotated to wind the negative electrode laminate and the positive electrode laminate while stacking them, and the winding core was removed to obtain a wound body.

[0113] The obtained wound body was inserted into an outer can, and a predetermined amount of electrolyte was poured into it to prepare a cylindrical nickel-zinc battery with a nominal capacity of 2000 mAh. Thereafter, the battery was activated by performing one cycle of charging to 100% of the nominal capacity and then discharging to 1.3 V.

[0114] Comparative Example 1 A battery was fabricated in the same manner as in Example 1, except that the separator 1 was replaced with separator 2. First, two separators 2 were prepared. A negative electrode was placed on one surface (the surface on which the microporous film was laminated) of the first separator 2 to form a negative electrode laminate. A positive electrode was placed on the other surface (the surface on which the auxiliary nonwoven fabric Y was laminated) of the second separator 2 to form a positive electrode laminate. Next, a winding core was placed between the separator of the negative electrode laminate and the separator of the positive electrode laminate. At this winding start position, the winding core was in contact with the microporous film of the negative electrode laminate and the nonwoven fabric X of the positive electrode laminate, respectively. The winding core was then rotated to stack and wind the negative electrode laminate and the positive electrode laminate, and the winding core was then removed to obtain a wound body.

[0115] Comparative Example 2 A battery was fabricated in the same manner as in Example 1, except that the separator 1 was replaced with separator 3. First, two of the separators 3 were prepared. A negative electrode was placed on one surface of the first separator 3 (the surface on which the auxiliary nonwoven fabric Y was not laminated) to form a negative electrode laminate. A positive electrode was placed on the other surface of the second separator 3 (the surface on which the auxiliary nonwoven fabric Y was laminated) to form a positive electrode laminate. Next, a winding core was placed between the separator of the negative electrode laminate and the separator of the positive electrode laminate. The winding core was then rotated to wind the negative electrode laminate and the positive electrode laminate while stacking them, and the winding core was then removed to obtain a wound body.

[0116] [Evaluation] (Winding Defects) For each of the Examples and Comparative Examples, 50 cells were wound to prepare wound bodies. The number of cells with winding defects among the 50 prepared cells was counted to calculate the incidence of winding defects. Incidence of Winding Defects (%) = (Number of Defective Cells / 50 Cells) x 100. The winding defects were visually judged as follows: when the winding core was pulled out from the wound body, the wound group became spiral, making it impossible to prepare a battery; or, even if the winding core was not spiraled, the separator broke before the winding core was pulled out (rupture of the microporous film).

[0117] (Cycle Test) Batteries were fabricated for those samples that did not form a spiral and for which the winding core could be removed to produce a wound body (n=3). In an environment of 35°C, the battery was charged at a constant current of 3.6 A until the voltage reached 1.90 V, followed by constant voltage charging at 1.9 V until the charge capacity reached 960 mAh, after which the battery was rested for 15 minutes. Subsequently, the battery was discharged at a constant current of 3.6 A until the battery voltage reached 1.3 V, followed by a rest period of 15 minutes. These steps constituted one cycle. This cycle was repeated until the battery life was reached. The ratio of the discharge capacity after each cycle to the discharge capacity at the first cycle was defined as the initial discharge capacity ratio. The number of cycles at which the initial discharge capacity ratio reached 90% was defined as the cycle life.

[0118] The evaluation results of Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

[0119]

[0120] (Discussion) As shown in Table 1, regarding winding defects, the microporous film was caught in the winding core during winding, causing winding defects such as breakage of the microporous film in Comparative Example 1. In contrast, in Example 1 and Comparative Example 2, the microporous film was not caught, and no winding defects such as breakage of the microporous film occurred.

[0121] Furthermore, the cycle life of Comparative Example 1 was 200 cycles, which was short. This is presumably because the microporous film got caught in the winding core, causing cracks in the microporous film when the winding core was pulled out, resulting in the early occurrence of a short circuit due to dendrites (i.e., a short circuit due to poor winding). On the other hand, Comparative Example 2, in which a microporous film was not used, also had a short cycle life of 200 cycles. This is presumably because a short circuit due to dendrites occurred early due to the absence of a microporous film, rather than a short circuit due to poor winding. In contrast, Example 1 had a long cycle life of 500 cycles. This is presumably because a microporous film was not placed in the portion in contact with the winding core, thereby suppressing short circuits due to poor winding.

[0122] This application claims priority from Japanese Patent Application No. 2024-060357, filed April 3, 2024. The contents of the specification and drawings of that application are incorporated herein by reference in their entirety.

[0123] According to the present invention, it is possible to provide an alkaline secondary battery in which a decrease in cycle life due to poor winding is suppressed, and a method for manufacturing the same.

[0124] REFERENCE SIGNS LIST 10 Nickel-zinc secondary battery 12 Outer can 12A Bottom wall 12C Opening edge 14 Sealing body 16 Winding body 16S Central space 18 Upper insulating member 20 Lower insulating member 22 Insulating packing 24 Cover plate 26 Valve body 28 Positive electrode terminal 30 Positive electrode 32 Negative electrode 34 Separator 34A First separator 34B Second separator 35, 35A, 35B Nonwoven fabric 36A, 36B Microporous film 37 Other nonwoven fabric 38 Positive electrode lead 40 Negative electrode laminate 42 Positive electrode laminate 44 Winding core

Claims

1. An alkaline secondary battery having a wound body in which a positive electrode and a negative electrode are stacked and wound with a separator interposed therebetween, the separator including a nonwoven fabric and a microporous film disposed on the nonwoven fabric, and the microporous film does not face a central space of the wound body.

2. The alkaline secondary battery according to claim 1, wherein the microporous film is disposed at a position away from a position facing the central space of the nonwoven fabric.

3. The alkaline secondary battery according to claim 1, wherein a radially inner end of the microporous film protrudes beyond a radially inner end of the negative electrode, and the separator further includes a protective member covering the protruding surface of the microporous film.

4. The alkaline secondary battery according to claim 1, wherein the microporous film has a radially inner end and a radially outer end fixed to the nonwoven fabric.

5. The alkaline secondary battery according to claim 1, wherein the microporous film is disposed between the nonwoven fabric and the negative electrode.

6. The alkaline secondary battery according to claim 1, wherein the separator further includes two other nonwoven fabrics disposed between the nonwoven fabric and the positive electrode, the two other nonwoven fabrics being disposed at positions corresponding to the radially inner end and the radially outer end of the positive electrode, respectively.

7. The alkaline secondary battery according to any one of claims 1 to 6, wherein the alkaline secondary battery is a nickel-zinc secondary battery.

8. A method for manufacturing an alkaline secondary battery, comprising: a step of placing a winding core on a separator comprising a nonwoven fabric and a microporous film disposed on the nonwoven fabric so as not to contact the microporous film; a step of winding a laminate formed by stacking a positive electrode and a negative electrode with the separator interposed between them around the winding core to obtain a wound body; and a step of pulling out the winding core from the wound body.

9. The method for producing an alkaline secondary battery according to claim 8, wherein the separators include a first separator on which the negative electrode is disposed and a second separator on which the positive electrode is disposed, the first separator includes a first nonwoven fabric and a first microporous film disposed on the first nonwoven fabric, and the second separator includes a second nonwoven fabric and a second microporous film disposed on the second nonwoven fabric, and the step of arranging the winding core includes preparing a negative electrode laminate in which the negative electrode is disposed on the first microporous film of the first separator and a positive electrode laminate in which the positive electrode is disposed on the second nonwoven fabric of the second separator, and arranging the winding core between the first separator and the second separator so that the winding core and the first microporous film do not come into contact, and the step of obtaining the wound body includes winding the negative electrode laminate and the positive electrode laminate while stacking them around the winding core.

10. A method for manufacturing an alkaline secondary battery as described in claim 9, wherein in the step of positioning the winding core, the first microporous film is positioned at a position at least the outer circumferential length of the winding core away from one end of the first nonwoven fabric in the longitudinal direction.

11. A method for manufacturing an alkaline secondary battery as described in claim 9 or 10, wherein in the step of positioning the winding core, one longitudinal end of the first microporous film protrudes beyond one longitudinal end of the negative electrode, and the protruding surface of the first microporous film is covered with a protective member.

12. The method for producing an alkaline secondary battery according to claim 8, wherein the separator comprises a first microporous film placed on the nonwoven fabric and a second microporous film placed on the nonwoven fabric with a gap between the first microporous film and the second microporous film, the winding core has a holding portion that holds the nonwoven fabric exposed in the gap, and in the step of placing the winding core, the nonwoven fabric exposed in the gap is held by the winding core, and in the step of obtaining the wound body, the negative electrode is placed on one surface of the first microporous film, and the positive electrode is placed on the back side of the surface of the nonwoven fabric on which the second microporous film is placed, and the separator is wound around the winding core.

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