Manufacturing method of secondary batteries

Abstract

To manufacture a secondary battery which has an electrode laminate and yet inhibits increase of battery resistance.SOLUTION: A manufacturing method of a secondary battery includes: a step in which an electrode laminate having a thickness exceeding an inner width of a box shaped case is forcibly pushed into the resin box shaped case with the box shaped case deflected to house the electrode laminate in the box shaped case; and a step in which an electrolytic solution is placed into the box shaped case in which the electrode laminate is housed.SELECTED DRAWING: Figure 1

Description

【Technical Field】 , , 【0001】 The present invention relates to a method for manufacturing a 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 through the gaps 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 prevents the penetration of zinc dendrites while selectively permeating hydroxide ions has been proposed. For example, Patent Document 1 (WO2019 / 124270) discloses an LDH separator including a polymer porous substrate and LDH filled in the porous substrate. Patent Document 2 (WO2019 / 077953) proposes 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 cover or enclose the positive electrode active material layer with a liquid retention member. Patent Document 3 (WO2021 / 024681) discloses an alkaline secondary battery in which a plurality of single cell elements having the configuration of an alkaline secondary battery such as a zinc secondary battery are vertically accommodated in a resin box-shaped case, and the single cell element is said to include a positive electrode plate, a negative electrode plate containing zinc, and an LDH separator containing a layered double hydroxide (LDH) and / or an LDH-like compound. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 WO2019 / 124270 【Patent Document 2】 WO2019 / 077953 【Patent Document 3】 WO2021 / 024681 [Overview of the project] 【0005】 Secondary batteries, such as those disclosed in Patent Documents 2 and 3, are manufactured by placing an electrode stack and an electrolyte into a resin box-shaped case that serves as the battery case and sealing it. However, when a secondary battery is constructed by placing an electrode stack and an electrolyte into a resin box-shaped case, the battery resistance tends to increase from the initial stage. Since an increase in battery resistance leads to a decrease in battery characteristics (e.g., battery output), improvement is desired. 【0006】 The inventors have now discovered that an increase in battery resistance can be suppressed by forcibly pushing an electrode stack with a thickness exceeding the inner width of a box-shaped case into the box-shaped case while bending the box-shaped case. 【0007】 Therefore, the object of the present invention is to manufacture a secondary battery that has an electrode stack while suppressing an increase in battery resistance. 【0008】 According to one aspect of the present invention, A step of housing an electrode laminate having a thickness exceeding the inner width of a box-shaped resin case by forcibly pushing the box-shaped case into the box-shaped resin case while bending the box-shaped case, A step of putting an electrolyte into the box-shaped case in which the electrode stack is housed, A method for manufacturing a secondary battery is provided, which includes [the following]. [Brief explanation of the drawing] 【0009】 [Figure 1] This is a schematic cross-sectional view illustrating the method for manufacturing a secondary battery according to the present invention. [Figure 2] This is a schematic cross-sectional view showing the pressurized state of a conventional secondary battery, where the electrode stack is thinner than the inner width of the box-shaped case. [Figure 3] This is a schematic cross-sectional view showing the pressurized state of the secondary battery according to the present invention, in which the electrode stack is thicker than the inner width of the box-shaped case. [Figure 4]This is a schematic cross-sectional view showing an example of a zinc secondary battery according to the present invention. [Figure 5] Figure 4 schematically shows a cross-section of the zinc secondary battery along the line A-A'. [Figure 6] Figure 4 is a schematic perspective view showing the electrode stack of a zinc secondary battery. [Figure 7] Figure 4 is a schematic cross-sectional view showing the electrode stack of a zinc secondary battery. [Figure 8] This graph shows the discharge resistance measured for nickel-zinc secondary batteries fabricated in Examples 1-42. [Modes for carrying out the invention] 【0010】 Manufacturing method of secondary batteries This invention relates to a method for manufacturing a secondary battery. The secondary battery manufactured in this invention is preferably a nickel-metal hydride secondary battery, a nickel-zinc secondary battery, or an air-zinc secondary battery, more preferably a nickel-zinc secondary battery or an air-zinc secondary battery, and even more preferably a nickel-zinc secondary battery. Therefore, although the following description may refer to the configuration of zinc secondary batteries such as nickel-zinc secondary batteries and air-zinc secondary batteries, this invention is not limited to zinc secondary batteries. 【0011】 The method for manufacturing a secondary battery according to the present invention includes the steps of housing an electrode stack 11 in a resin box-shaped case 20 as shown in Figure 1, and filling the box-shaped case 20 containing the electrode stack 11 with an electrolyte 18. In the step of housing the electrode stack 11 in the box-shaped case 20, the electrode stack 11, having a thickness T exceeding the inner width W (distance between inner walls in the short direction) of the box-shaped case 20, is forcibly pushed into the box-shaped case 20 while bending the box-shaped case 20, thereby housing the electrode stack 11 inside the box-shaped case 20. This makes it possible to suppress an increase in battery resistance. 【0012】 In other words, as mentioned above, conventional secondary batteries, such as those disclosed in Patent Documents 2 and 3, are manufactured by placing an electrode stack and an electrolyte into a resin box-shaped case that serves as the battery case and sealing it. However, when a secondary battery is constructed by placing an electrode stack and an electrolyte into a resin box-shaped case, the battery resistance tends to increase from the initial stage. This problem is successfully resolved according to the present invention. The mechanism is thought to be as follows. Figure 2 shows a configuration of a conventional secondary battery 100 in which an electrode stack 11 with a thickness thinner than the inner width of a box-shaped case 20 is placed. In this case, the box-shaped case 20 housing the electrode stack 11 has excess internal space on both sides of the electrode stack 11. In this case, when pressure is applied to both sides of the box-shaped case 20 with the pressure jig 8, the area near the upper and lower ends of the box-shaped case 20 is difficult to deform (because it is firmly supported by the lid and bottom which are arranged in a direction opposite to the direction of pressure), and therefore cannot fit well to the electrode stack 11. As a result, only localized pressure can be applied to the electrode stack 11, and sufficient (or uniform) pressure cannot be applied to the entire electrode stack 11. This is thought to lead to an increase in battery resistance. In contrast, in the configuration of the secondary battery 10 according to the present invention, as shown in Figure 3, in which an electrode stack 11 with a thickness greater than the inner width of the box-shaped case 20 is placed inside the box-shaped case 20, sufficient (or uniform) pressure can be applied to the entire electrode stack 11. That is, in the configuration of Figure 3, when pressure is applied to both sides of the box-shaped case 20 with the pressure jig 8, the entire inner wall surface from the upper end to the lower end of the box-shaped case 20 can fit the electrode stack 11 well, so sufficient (or uniform) pressure can be applied to the electrode stack 11. As a result, it is thought that the increase in battery resistance is suppressed according to the present invention. 【0013】 The following describes each step of the present invention in detail. 【0014】 (1) Housing of the electrode stack inside a box-shaped case First, the electrode stack 11, which has a thickness exceeding the inner width of the box-shaped case 20, is forcibly pushed into the box-shaped case 20 while bending it, thereby housing the electrode stack 11 inside the box-shaped case 20. That is, since the thickness T of the electrode stack 11 exceeds the inner width W of the box-shaped case 20, it cannot be inserted into the box-shaped case 20 smoothly. However, contrary to the inner dimensions (especially the inner width) of the box-shaped case 20, the electrode stack 11 can be forcibly pushed in while bending the box-shaped case 20 (i.e., by applying a strong force to insert the electrode stack 11 against the rigidity of the box-shaped case 20), thereby housing the electrode stack 11 inside the box-shaped case 20. This is because the box-shaped case 20, being made of resin, has some flexibility, and can be bent to the extent that the electrode stack 11 can be pushed in when force is applied. Pushing the electrode stack 11 into the box-shaped case 20 may be done manually or mechanically using a device. 【0015】 The box-shaped case 20 is made of resin. The resin constituting the box-shaped case 20 is preferably a resin that has resistance to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, ABS resin, or modified polyphenylene ether, and even more preferably ABS resin or modified polyphenylene ether. The box-shaped case 20 has a top lid 20a. The box-shaped case 20 (for example, the top lid 20a) may have a pressure relief valve for releasing gas. Alternatively, a group of cases in which two or more box-shaped cases 20 are arranged may be housed in an outer frame to form a battery module. 【0016】 The dimensions of the box-shaped case 20 are not particularly limited as long as the inner width W is slightly smaller than the thickness T of the electrode laminate 11 but can still barely accommodate the electrode laminate 11. For example, the inner width (the distance between the inner walls in the short side direction) of the box-shaped case 20 is preferably 20-35 mm, more preferably 20-30 mm, and even more preferably 20-25 mm. The inner length (the distance between the inner walls in the long side direction) of the box-shaped case 20 is preferably 170-230 mm, more preferably 180-220 mm, and even more preferably 190-210 mm. The inner height (the distance from the bottom to the upper lid 20a) of the box-shaped case 20 is preferably 140-200 mm, more preferably 150-190 mm, and even more preferably 160-180 mm. 【0017】 Figures 4 to 7 show preferred forms of the electrode laminate 11 and the secondary battery 10 including the same. The electrode laminate 11 is a laminate including a plurality of electrode layers. The thickness of the electrode laminate 11 is preferably 0.1 mm or more thicker than the inner width of the box-shaped case 20, more preferably 0.2-3.0 mm, even more preferably 0.2-2.5 mm, particularly preferably 0.2-2.0 mm, particularly more preferably 0.3-1.5 mm, particularly even more preferably 0.3-1.1 mm, and most preferably 0.3-1.0 mm thicker than the inner width W of the box-shaped case 20. In this specification, the thickness T of the electrode laminate 11 is defined as the thickness (i.e., the distance between the plates) measured after being pressed at 0.03 MPa for 30 seconds in the thickness direction with a pair of plates sandwiching it. The thickness of the electrode laminate 11 can vary depending on whether the electrode layers are densely laminated or loosely laminated. However, by sandwiching the electrode laminate 11 with a pair of plates and pressing it under the above conditions, factors causing thickness variation such as voids between the electrode layers can be eliminated, and the thickness can be measured. Therefore, the thickness can be uniquely specified regardless of the state of the electrode laminate 11. 【0018】 Typically, the electrode laminate 11 includes a positive electrode layer 12, a negative electrode layer 14, and a separator 16 that separates the positive electrode layer 12 and the negative electrode layer 14 from each other. Therefore, the electrode laminate 11 can be said to be a battery element that exhibits the function as the secondary battery 10 when the electrolytic solution 18 penetrates therein. In particular, as shown in FIGS. 6 and 7, the electrode laminate 11 preferably has a form of a positive / negative electrode laminate in which a plurality of positive electrode layers 12, a plurality of negative electrode layers 14, and a plurality of separators 16 are provided and the unit of the positive electrode layer 12 / separator 16 / negative electrode layer 14 is repeated and laminated. That is, the electrode laminate 11 preferably has a plurality of unit cells 10a each including a positive electrode layer 12, a separator 16, and a negative electrode layer 14, and a plurality of unit cells 10a thereby 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. 【0019】 The positive electrode layer 12 may include a positive electrode active material layer. The positive electrode active material constituting the positive electrode active material layer is not particularly limited and can be appropriately selected from known positive electrode materials depending on the type of secondary battery. For example, in the case of a nickel-zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode. The positive electrode layer 12 may further include a positive electrode current collector (not shown). The positive electrode current collector preferably has a positive electrode current collector tab 12b extending in a predetermined direction (for example, upward) from the end (e.g., upper end) of the positive electrode layer 12. A preferred example of a positive electrode current collector is a nickel porous substrate such as a foamed nickel plate. In this case, for example, a positive electrode plate consisting of a positive electrode / positive electrode current collector can be preferably manufactured by uniformly applying a paste containing an electrode active material such as nickel hydroxide onto the nickel porous substrate and drying it. At that time, it is also preferable to press the dried positive electrode plate (i.e., positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and to improve the electrode density. Note that the positive electrode layer 12 shown in Figure 7 contains a positive electrode current collector (e.g., foamed nickel), but it is not shown. This is because, in the case of nickel-zinc secondary batteries, the positive electrode current collector is integrated with the positive electrode active material, so the positive electrode current collector cannot be depicted individually. The positive electrode current collector tab 12b may be made of the same material as the positive electrode current collector, or it may be made of a different material. If the positive electrode current collector is a porous nickel substrate such as a foamed nickel plate, it can be processed into a tab shape by pressing it. In any case, the positive electrode current collector tab 12b may be extended by adding another current collector member such as a tab lead to such a tab. In any case, it is preferable that multiple positive electrode current collector tabs 12b are joined to a single positive electrode terminal 26 or a member electrically connected to it to form a positive electrode tab joint (not shown). This allows for space-efficient power collection with a simple configuration, and also facilitates connection to the positive terminal 26. The positive current collection tab 12b and components such as terminals can be joined using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, or resistance welding. 【0020】 The positive electrode layer 12 may contain an additive, which is at least one selected from the group consisting of silver compounds, manganese compounds, and titanium compounds, thereby promoting the positive electrode reaction that absorbs hydrogen gas generated by the self-discharge reaction. The positive electrode layer 12 may also further contain cobalt. It is preferable that the cobalt is included in the positive electrode layer 12 in the form of cobalt oxyhydroxide. In the positive electrode layer 12, the cobalt functions as a conductive additive, thereby contributing to an improvement in charge-discharge capacity. 【0021】 The negative electrode layer 14 may include a negative electrode active material layer 14a. For example, in the case of a zinc secondary battery, 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 alloys, and zinc compounds. Zinc may be included in any form of zinc metal, zinc compounds, or zinc alloys, as long as it has electrochemical activity suitable for the negative electrode. Preferred examples of negative electrode materials include zinc oxide, zinc metal, calcium zincate, etc., but a mixture of zinc metal and zinc oxide is more preferred. The negative electrode active material may be configured in a gel state, or it may be mixed with the electrolyte 18 to form a negative electrode composite material. For example, a gelled negative electrode can be easily obtained by adding an electrolyte and a thickener to the negative electrode active material. Examples of thickeners include polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc., but polyacrylic acid is preferred because it has excellent chemical resistance to strong alkalis. 【0022】 As the zinc alloy, a mercury- and lead-free zinc alloy known as mercury-free zinc alloy can be used. For example, a zinc alloy containing 0.01 to 0.1 mass% indium, 0.005 to 0.02 mass% bismuth, and 0.0035 to 0.015 mass% aluminum is preferred because it has a hydrogen gas generation suppression effect. In particular, indium and bismuth are advantageous in that they improve discharge performance. Using a zinc alloy as the negative electrode can improve safety by suppressing hydrogen gas generation through a slower self-dissolution rate in an alkaline electrolyte. 【0023】 The shape of the negative electrode material is not particularly limited, but it is preferably in powder form, as this increases the surface area and allows it to handle high-current discharge. The preferred average particle size of the negative electrode material is in the range of 3 to 100 μm in the short diameter for zinc alloys. Within this range, the surface area is large, making it suitable for handling high-current discharge, and it is also easy to uniformly mix with the electrolyte and gelling agent, resulting in good handling during battery assembly. 【0024】 The negative electrode layer 14 may further include a negative electrode current collector 14b. The negative electrode current collector 14b is preferably provided inside and / or on the surface of the negative electrode active material layer 14a, except for the portion that extends as a negative electrode current collector tab 14c. That is, the negative electrode active material layer 14a may be arranged on both sides of the negative electrode current collector 14b, or the negative electrode active material layer 14a may be arranged on only one side of the negative electrode current collector 14b. The negative electrode current collector tab 14c extends from the end (e.g., upper end) of the negative electrode layer 14 in a predetermined direction (e.g., upward) at a position that does not overlap with the positive electrode current collector tab 12b. The negative electrode current collector tab 14c is preferably provided at a position that does not overlap with the positive electrode current collector tab 12b. The negative electrode current collector tab 14c may be made of the same material as the negative electrode current collector 14b, or it may be made of a different material. In any case, the negative electrode current collector tab 14c may be extended by adding another current collector member, such as a tab lead, to such a tab. In any case, it is preferable that multiple negative electrode current collector tabs 14c are joined to a single negative electrode terminal 28 or a member electrically connected to it to form a negative electrode tab joint 30. This allows for current collection with a simple configuration and space efficiency, and also facilitates connection to the negative electrode terminal 28. The joining of the negative electrode current collector tab 14c to the terminal or other member can be performed using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, or resistance welding. 【0025】 From the viewpoint of fixing the negative electrode active material to the current collector, it is preferable to use a metal plate having multiple (or many) openings for the negative electrode current collector 14b. Preferred examples of such negative electrode current collectors 14b include expanded metal, perforated metal, metal mesh, and combinations thereof, more preferably copper expanded metal, copper perforated metal, and combinations thereof, and particularly preferably copper expanded metal. In this case, for example, a negative electrode plate consisting of a negative electrode / negative electrode current collector can be preferably manufactured by coating a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (e.g., polytetrafluoroethylene particles), onto copper expanded metal. At that time, it is also preferable to press the negative electrode plate (i.e., negative electrode / negative electrode current collector) after drying to prevent the electrode active material from falling off and to improve the electrode density. Expanded metal is a mesh-like metal plate made by pressing a metal plate with an expandable manufacturing machine while making staggered cuts, and shaping the cuts into a diamond or tortoise shell pattern. Perforated metal, also known as punched metal mesh, is a metal sheet with holes punched into it. Metal mesh is a metal product with a wire mesh structure and is different from expanded metal or perforated metal. 【0026】 The separator 16 is preferably a hydroxide ion conductive separator. The hydroxide ion conductive separator 16 is provided to isolate the positive electrode layer 12 and the negative electrode layer 14 in a manner that allows hydroxide ions to conduct. For example, as shown in Figure 7, the negative electrode layer 14 may be covered or enclosed by the hydroxide ion conductive separator 16. This eliminates the need for complicated sealing and bonding between the hydroxide ion conductive separator 16 and the battery container, making it possible to manufacture nickel-zinc secondary batteries (especially their stacked batteries) that can prevent zinc dendrite extension very simply and with high productivity. However, a simpler configuration in which the hydroxide ion conductive separator 16 is arranged on one side of the positive electrode layer 12 or the negative electrode layer 14 is also acceptable. 【0027】 The hydroxide ion conductive separator 16 is not particularly limited as long as it is a separator capable of separating the positive electrode layer 12 and the negative electrode layer 14 in a way that allows hydroxide ions to conduct, but typically it is a separator that contains a hydroxide ion conductive solid electrolyte and selectively passes hydroxide ions by exclusively utilizing its hydroxide ion conductivity. Preferred hydroxide ion conductive solid electrolytes are layered double hydroxides (LDH) and / or LDH-like compounds. Therefore, it is preferable that the hydroxide ion conductive separator 16 is an LDH separator. In this specification, "LDH separator" is defined as a separator containing LDH and / or an LDH-like compound that selectively passes hydroxide ions by exclusively utilizing the hydroxide ion conductivity of LDH and / or an LDH-like compound. In this specification, "LDH-like compound" is a hydroxide and / or oxide with a layered crystalline structure similar to LDH, which may not be called LDH, and can be considered an equivalent of LDH. However, in a broader definition, "LDH" can also be interpreted to include not only LDH but also LDH-like compounds. The LDH separator is preferably compounded with a porous substrate. Therefore, the LDH separator is preferably compounded with the porous substrate in a form in which LDH and / or an LDH-like compound fills the pores of the porous substrate. That is, in a preferred LDH separator, the LDH and / or LDH-like compound fills 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 preferable that the LDH is incorporated throughout the entire thickness of the polymer porous substrate. For example, known LDH separators such as those disclosed in Patent Documents 1 to 7 can be used. The thickness of the LDH separator is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm. 【0028】 As shown in Figures 1-7, it is preferable that the positive electrode layer 12, the negative electrode layer 14, and the separator 16 are arranged vertically, thereby creating a multilayer cell that is layered horizontally. It is also preferable that the positive electrode current collector tab 12b and the negative electrode current collector tab 14c extend upward. 【0029】 The electrode laminate 11 may further include a liquid-retaining member 17. The liquid-retaining member 17 is preferably provided at a position that contacts the positive electrode layer 12 and / or the negative electrode layer 14. For example, not only the hydroxide ion conductive separator 16 but also the liquid-retaining member 17 may be interposed between the positive electrode layer 12 and the negative electrode layer 14. And, as shown in Figure 7, it is preferable that the positive electrode layer 12 and / or the negative electrode layer 14 are covered or wrapped by the liquid-retaining member 17. However, a simpler configuration in which the liquid-retaining member 17 is arranged on one side of the positive electrode layer 12 or the negative electrode layer 14 is also acceptable. In any case, by interposing the liquid-retaining member 17, the electrolyte 18 can be evenly distributed between the positive electrode layer 12 and / or the negative electrode layer 14 and the hydroxide ion conductive separator 16, and the exchange of hydroxide ions between the positive electrode layer 12 and / or the negative electrode layer 14 and the hydroxide ion conductive separator 16 can be efficiently carried out. The liquid-retaining member 17 is not particularly limited as long as it is a member capable of holding the electrolyte 18, but it is preferably a sheet-like member. Preferred examples of the liquid-retaining member 17 include nonwoven fabric, superabsorbent resin, liquid-retaining resin, porous sheet, and various spacers, but nonwoven fabric is particularly preferred because it allows for the production of a low-cost, high-performance electrode structure. The liquid-retaining member 17 or nonwoven fabric is preferably 10 to 200 μm thick, more preferably 20 to 200 μm, even more preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. With a thickness within the above range, a sufficient amount of electrolyte 18 can be held within the liquid-retaining member 17 while keeping the overall size of the positive electrode structure and / or negative electrode structure compact and without waste. 【0030】 When the positive electrode layer 12 and / or the negative electrode layer 14 are covered or enclosed by the fluid-retaining member 17 and / or separator 16, it is preferable that their outer edges are closed (except for the edges from which the positive electrode current collector tab 12b and the negative electrode current collector tab 14c extend). In this case, it is preferable that the closed edges of the outer edges of the fluid-retaining member 17 and / or separator 16 are achieved by bending the fluid-retaining member 17 and / or separator 16, or by sealing the fluid-retaining members 17 with each other and / or the separators 16 with each other. Preferred sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. In particular, LDH separators containing a porous substrate made of polymer material have the advantage of being flexible and therefore easy to bend, so it is preferable to form the LDH separator in a long shape and bend it to form a closed state on one side of the outer edge. Heat welding and ultrasonic welding can be performed using commercially available heat sealers, but in the case of sealing LDH separators together, it is preferable to perform heat welding and ultrasonic welding by sandwiching the outer periphery of the liquid-retaining member 17 between the LDH separators that constitute the outer periphery, as this allows for more effective sealing. On the other hand, commercially available adhesives, adhesive tapes, and sealing tapes can be used, but it is preferable to use those containing alkali-resistant resins to prevent deterioration in alkaline electrolytes. From this viewpoint, examples of preferred adhesives include epoxy resin adhesives, natural resin adhesives, modified olefin resin adhesives, and modified silicone resin adhesives, among which epoxy resin adhesives are more preferred due to their particularly excellent alkali resistance. An example of an epoxy resin adhesive product is the epoxy adhesive Hysol® (manufactured by Henkel). 【0031】 Preferably, the outer edge of one side that forms the upper end of the separator 16 is open. This open-top configuration allows for addressing the problem of overcharging in nickel-zinc batteries and the like. Specifically, when nickel-zinc batteries and the like are overcharged, oxygen (O2) may be generated in the positive electrode layer 12, but the LDH separator has a high degree of density that substantially only allows hydroxide ions to pass through, and therefore does not allow O2 to pass through. In this respect, with the open-top configuration, within the box-shaped case 20, O2 can escape to the upper part of the positive electrode layer 12 and be sent to the negative electrode layer 14 side through the open top part, thereby oxidizing the Zn of the negative electrode active material with O2 and returning it to ZnO. By going through such an oxygen reaction cycle, the overcharge resistance can be improved by using the open-top electrode stack 11 in a sealed zinc secondary battery. Even if the outer edge of one side that forms the upper end of the separator 16 or the liquid retention member 17 is closed, the same effect as the open-top configuration can be expected by providing a ventilation hole in a part of the closed outer edge. For example, the outer edge of one side that forms the upper end of the LDH separator may be sealed before creating a ventilation hole, or a portion of the outer edge may be left unsealed during sealing so that a ventilation hole is formed. 【0032】 (2) Injection of electrolyte An electrolyte 18 is placed in a box-shaped case 20 containing the electrode stack 11. The electrolyte 18 preferably contains an aqueous alkali metal hydroxide solution. In Figure 7, the electrolyte 18 is only shown locally because it is distributed throughout the entire positive electrode layer 12 and negative electrode layer 14. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, but potassium hydroxide is more preferred. 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 electrolyte. As mentioned above, the electrolyte may be mixed with the positive electrode active material and / or negative electrode active material to exist in the form of a positive electrode composite and / or negative electrode composite. Furthermore, the electrolyte may be gelled to prevent leakage of the electrolyte. As a gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolyte and swells, and polymers such as polyethylene oxide, polyvinyl alcohol, polyacrylamide, and starch are used. The method for pouring the electrolyte 18 into the box-shaped case 20 is not particularly limited. The electrolyte 18 may be poured from the open upper portion of the box-shaped case 20 containing the electrode stack 11, or the open upper portion of the box-shaped case 20 containing the electrode stack 11 may be closed with a lid 20a, and the electrolyte may be poured from an injection port provided on the lid 20a. In any case, it is preferable to seal the box-shaped case 20, or the lid 20a or the injection port after pouring the electrolyte 18. [Examples] 【0033】 The present invention will be further explained by the following examples. 【0034】 Examples 1-42 (1) Manufacturing of nickel-zinc secondary batteries The following components were prepared: a positive electrode plate, a positive electrode current collector tab, a negative electrode plate, a negative electrode current collector tab, an LDH separator, a nonwoven fabric, a battery case, and an electrolyte. To create electrode stacks of various thicknesses, negative electrode plates of various thicknesses were prepared. • Positive electrode plate: A positive electrode paste containing nickel hydroxide and binder is filled into the pores of foamed nickel and dried (an uncoated area exists near one edge of the foamed nickel where the positive electrode paste is not applied). • Positive electrode current collector tab: The uncoated portion of the foamed nickel that makes up the positive electrode plate is compressed into a tab using a roll press, and a tab lead (made of pure nickel, thickness: 100 μm) is ultrasonically welded to this tab to extend it. • Negative electrode plate: A negative electrode paste containing ZnO powder, metallic Zn powder, polytetrafluoroethylene (PTFE), and propylene glycol is pressed onto a current collector (copper expanded metal) (an uncoated area exists near one end of the copper expanded metal where the negative electrode paste is not applied). • Negative electrode current collector tab: A tab lead (made of copper, thickness: 100 μm) is connected to the unpainted portion of copper expanded metal by ultrasonic welding. • LDH separator: A polyethylene microporous membrane on which Ni-Al-Ti-LDH (layered double hydroxide) is deposited by hydrothermal synthesis in the pores and on the surface, then roll-pressed; thickness: 20 μm Nonwoven fabric: Made of polypropylene, 100 μm thick • Battery case: Box-shaped case made of modified polyphenylene ether resin (equipped with a pressure relief valve to release gas generated inside the case), internal dimensions: length 190mm, width 24mm, height 165mm, external dimensions: length 200mm, width 30mm, height 170mm (excluding the height of the positive and negative terminals) • Electrolyte: 5.4 mol / L KOH aqueous solution with 0.4 mol / L ZnO dissolved in it. 【0035】 The positive electrode plate was wrapped in nonwoven fabric from both sides, so that the nonwoven fabric slightly protruded from the three sides excluding the side from which the positive electrode current collector tab extended. The excess portions of the nonwoven fabric protruding from the three sides of the positive electrode plate were heat-sealed using a heat-sealing bar to obtain a positive electrode structure. Similarly, the negative electrode plate was wrapped in nonwoven fabric and LDH separator from both sides in sequence, so that the nonwoven fabric and LDH separator slightly protruded from the three sides excluding the side from which the negative electrode current collector tab extended. The excess portions of the nonwoven fabric and LDH separator protruding from the three sides of the negative electrode plate were heat-sealed using a heat-sealing bar to obtain a negative electrode structure. In this way, multiple positive electrode structures and multiple negative electrode structures were prepared. 【0036】 Twelve positive electrode structures and thirteen negative electrode structures were alternately stacked to create 42 electrode stacks of varying thicknesses. The thickness of the electrode stacks was adjusted as needed by changing the thickness of the negative electrode plates. Similar to the configuration shown in Figure 6, the multiple positive electrode current collector tabs 12b and multiple negative electrode current collector tabs 14c are designed to extend from different positions on the electrode current collector when viewed from above. Therefore, multiple positive electrode current collector tabs 12b overlap each other, while multiple negative electrode current collector tabs 14c overlap each other at a different position. As shown in Figures 4 and 5, the overlapping portions of the multiple positive electrode current collector tabs 12b were joined to the positive electrode terminal 26 by laser welding to form a positive electrode tab joint (not shown). Similarly, the overlapping portions of the multiple negative electrode current collector tabs 14c were joined to the negative electrode terminal 28 by laser welding to form a negative electrode tab joint 30. Thus, a stack of electrode structures equipped with positive electrode current collector tabs 12b and negative electrode current collector tabs 14c was obtained as an electrode stack 11. The electrode stack 11 was sandwiched between a pair of plates (made of stainless steel) and pressurized at 0.03 MPa in the thickness direction for 30 seconds, after which the thickness T of the electrode stack 11 was measured. As shown in Figures 1 to 5, this electrode stack 11 was placed in a box-shaped case 20, electrolyte 18 was injected to impregnate the electrode stack 11, and the lid 20a was closed to seal it. At this time, if the thickness T of the electrode stack 11 exceeded the inner width W (24 mm) of the box-shaped case 20 (i.e., TW > 0), the electrode stack 11 was forcibly pushed into the box-shaped case 20 while bending the box-shaped case 20. Forty-two nickel-zinc secondary batteries were measured in this way. 【0037】 (2) Initial single cell characteristics (discharge resistance) The discharge resistance, which is the initial single-cell characteristic of the fabricated nickel-zinc secondary battery, was measured as follows. Using a charge / discharge device (TOSCAT3100, manufactured by Toyo System Co., Ltd.), the fabricated nickel-zinc secondary battery was subjected to chemical conversion by charging at 0.1C and discharging at 0.2C. Subsequently, one 0.5C charge / discharge cycle was performed, and the average voltage during discharge was calculated from the obtained discharge capacity and discharge energy. The discharge resistance was defined as the value obtained by dividing the difference between the theoretical voltage and the average discharge voltage of the nickel-zinc battery by the discharge current. 【0038】 Figure 8 shows a graph of the discharge resistance measured for the fabricated nickel-zinc secondary battery. In this graph, the vertical axis corresponds to the resistance (relative value), while the horizontal axis corresponds to the value TW, which is obtained by subtracting the inner width W (24 mm) of the box-shaped case 20 from the thickness T of the electrode stack 11. Therefore, a positive value for TW means that the electrode stack 11 is thicker than the inner width W of the box-shaped case 20, and a negative value for TW means that the electrode stack 11 is thinner than the inner width W of the box-shaped case 20. As is clear from the results shown in Figure 8, when the electrode stack 11 is thicker than the inner width W of the box-shaped case 20 (i.e., TW > 0), the resistance is significantly reduced compared to when the electrode stack 11 is thinner than the inner width W of the box-shaped case 20 (i.e., TW ≤ 0). [Explanation of symbols] 【0039】 8. Pressurizing jig 10,100 Secondary batteries 10a unit cell 11 Electrode Stack 12 Positive electrode layer 12b Positive electrode current collector tab 14. Negative electrode layer 14a Negative electrode active material layer 14b Negative electrode current collector 14c Negative electrode current collector tab 16. Hydroxide ion conductive separator 17 Liquid retention member 18 Electrolyte 20 Box-type cases 20a Top lid 26 Positive terminal 28 Negative terminal 30 Negative electrode tab joint

Claims

[Claim 1] A step of housing an electrode laminate having a thickness exceeding the inner width of a box-shaped resin case by forcibly pushing the box-shaped case into the box-shaped resin case while bending the box-shaped case, A step of putting an electrolyte into the box-shaped case in which the electrode stack is housed, A method for manufacturing a secondary battery selected from the group consisting of nickel-metal hydride secondary batteries, nickel-zinc secondary batteries, and zinc-air secondary batteries, including the above. [Claim 2] The method for manufacturing a secondary battery according to claim 1, wherein the thickness of the electrode stack is measured after being sandwiched between a pair of plates and pressurized at 0.03 MPa in the thickness direction for 30 seconds, and is 0.1 mm or more thicker than the inner width of the box-shaped case. [Claim 3] The method for manufacturing a secondary battery according to claim 2, wherein the thickness of the electrode stack is 0.2 to 3.0 mm thicker than the inner width of the box-shaped case. [Claim 4] A method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein the electrode stack comprises a positive electrode layer, a negative electrode layer, and a separator that separates the positive electrode layer and the negative electrode layer from each other. [Claim 5] The method for manufacturing a secondary battery according to claim 4, wherein the electrode stack has a plurality of unit cells, each including the positive electrode layer, the separator, and the negative electrode layer, and the plurality of unit cells as a whole form a multilayer cell. [Claim 6] The method for manufacturing a secondary battery according to claim 4 or 5, wherein the electrode stack further includes a liquid-retaining member. [Claim 7] A step of housing an electrode laminate having a thickness exceeding the inner width of a box-shaped resin case by forcibly pushing the electrode laminate into the box-shaped resin case while bending the box-shaped case, A step of putting an electrolyte into the box-shaped case in which the electrode stack is housed, Includes, A method for manufacturing a secondary battery, wherein the thickness of the electrode stack is measured after being sandwiched between a pair of plates and pressurized at 0.03 MPa in the thickness direction for 30 seconds, and is at least 0.1 mm thicker than the inner width of the box-shaped case. [Claim 8] The method for manufacturing a secondary battery according to claim 7, wherein the thickness of the electrode stack is 0.2 to 3.0 mm thicker than the inner width of the box-shaped case. [Claim 9] The method for manufacturing a secondary battery according to claim 7 or 8, wherein the electrode stack comprises a positive electrode layer, a negative electrode layer, and a separator that separates the positive electrode layer and the negative electrode layer from each other. [Claim 10] The method for manufacturing a secondary battery according to claim 9, wherein the electrode stack has a plurality of unit cells, each including the positive electrode layer, the separator, and the negative electrode layer, and the plurality of unit cells as a whole form a multilayer cell. [Claim 11] The method for manufacturing a secondary battery according to claim 9 or 10, wherein the electrode stack further comprises a liquid-retaining member.

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