WO2019069762A1

WO2019069762A1 - Method of manufacturing negative electrode structure for zinc secondary battery

Info

Publication number: WO2019069762A1
Application number: PCT/JP2018/035659
Authority: WO
Inventors: 淳宣松矢; 裕一権田; 鬼頭　賢信; 毅八木
Original assignee: 日本碍子株式会社
Priority date: 2017-10-03
Filing date: 2018-09-26
Publication date: 2019-04-11
Also published as: JP6677860B2; JPWO2019069762A1

Abstract

Provided is a method of efficiently manufacturing a negative electrode structure with which it is possible to fabricate, in a very simple and highly productive manner, a zinc secondary battery (particularly, a laminated battery thereof) in which zinc dendrite extension can be prevented. The method comprises: (a) a step of obtaining a first laminated body by entirely covering or enclosing a rectangular negative electrode active material layer including at least one selected from zinc and the like, with a rectangular liquid-retention member of a greater size; (b) a step of obtaining a second laminated body by entirely sandwiching the first laminated body with a once-folded single rectangular sheet of layered double hydroxide (LDH) separator in such a way that overlapping portions extending beyond the outer edges of the negative electrode active material layer are formed along the entire outer edges; and (c) a step of sealing the overlapping portion of the outer edge of at least one of the sides adjacent to the side along the fold of the second laminated body.

Description

Method of manufacturing negative electrode structure for zinc secondary battery

The present invention relates to a method of manufacturing a negative electrode structure for a zinc secondary battery.

In zinc secondary batteries such as nickel zinc secondary batteries and air zinc secondary batteries, metal zinc precipitates in a dendritic form from the negative electrode at the time of charge, penetrates the gaps of the separator such as non-woven fabric, and reaches the positive electrode. It is known to cause a short circuit. The short circuit resulting from such zinc dendrite repeatedly leads to shortening of the charge and discharge life.

To address the above problems, batteries have been proposed that include layered double hydroxide (LDH) separators that block penetration of zinc dendrite while selectively transmitting hydroxide ions. For example, Patent Document 1 (WO 2013/118561) discloses that an LDH separator is provided between a positive electrode and a negative electrode in a nickel zinc secondary battery. In addition, Patent Document 2 (International Publication No. 2016/076047) discloses a separator structure including an LDH separator fitted or joined to a resin outer frame, and the LDH separator is gas impermeable and It is disclosed that it has high compactness so as to have water impermeability. This document also discloses that the LDH separator can be complexed with a porous substrate. Furthermore, Patent Document 3 (WO 2016/067884) discloses various methods for forming an LDH dense film on the surface of a porous substrate to obtain a composite material (LDH separator). In this method, a starting material capable of giving an origin of crystal growth of LDH is uniformly attached to the porous substrate, and the porous substrate is subjected to a hydrothermal treatment in a raw material aqueous solution to form an LDH dense film on the surface of the porous substrate. And the process of forming it.

International Publication No. 2013/118561 International Publication No. 2016/076047 International Publication No. 2016/067884

When a zinc secondary battery such as a nickel zinc battery is configured using the LDH separator as described above, a short circuit or the like due to zinc dendrite can be prevented. And, in order to maximize this effect, it is desirable that the positive electrode and the negative electrode be reliably separated by the LDH separator. In particular, it is extremely advantageous if the stacked battery can be easily assembled by combining a plurality of positive electrodes and a plurality of negative electrodes in order to obtain a high voltage and a large current while securing such a configuration. However, the separation of the positive electrode and the negative electrode by the LDH separator in the conventional zinc secondary battery is cleverly and carefully sealed and joined using a resin frame, an adhesive and the like so as to ensure liquid tightness between the LDH separator and the battery container. It was easy to make the battery configuration and the manufacturing process complicated. Such complication of the battery configuration and the manufacturing process can be particularly remarkable in the case of constructing a laminated battery. This is because it is necessary to perform sealing and bonding for securing liquid tightness to each of the plurality of unit cells constituting the laminated battery.

The present inventors now have a negative electrode structure suitable for a zinc secondary battery (in particular, a laminated battery thereof) capable of preventing zinc dendrite extension by covering or encasing the entire negative electrode active material layer with a liquid retaining member and an LDH separator. We have found that we can produce our body efficiently. Moreover, by using the thus-produced negative electrode structure, it is possible to eliminate the need for complicated sealing and bonding between the LDH separator and the battery container, and to prevent zinc dendrite extension (in particular, the laminated battery thereof). We have also found that it can be produced very easily and with high productivity.

Therefore, an object of the present invention is to efficiently produce a negative electrode structure capable of producing a zinc secondary battery (in particular, a laminated battery thereof) capable of preventing extension of zinc dendrite extremely easily and with high productivity. It is in.

According to one aspect of the present invention, there is provided a method of manufacturing a negative electrode structure for a zinc secondary battery, comprising:
(A) Covering the whole of a quadrilateral-shaped negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy and a zinc compound with a quadrilateral-shaped liquid holding member of a larger size Or encasing to obtain a first laminate;
(B) The entire first laminate is formed of one quadrilateral layered double hydroxide (LDH) separator folded at one side or at least two quadrilateral LDH separators not folded. Sandwiching an overlap portion protruding from the outer edge of the negative electrode active material layer so as to form the entire area of the outer edge to obtain a second laminate;
(C) When using the one folded LDH separator, the overlapping portion belonging to the outer edge of at least one side adjacent to the folded side of the second laminate is sealed or not folded In the case of using two LDH separators, a negative electrode structure in which overlapping portions belonging to the outer edges of at least two adjacent sides of the second laminate are sealed, and as a result, the outer edges of at least two adjacent sides are closed. The process of gaining a body,
Methods are provided.

It is a perspective view which shows an example of the negative electrode structure manufactured by the manufacturing method of this invention. It is a schematic cross section which shows the laminated constitution of the negative electrode structure shown by FIG. 1A. It is a process flowchart explaining an example of the manufacturing method of the negative electrode structure by this invention. It is a process flowchart explaining another example of the manufacturing method of the negative electrode structure by this invention. It is a schematic diagram for demonstrating the area | region covered with the LDH separator in an example of the negative electrode structure manufactured by the manufacturing method of this invention. FIG. 2 is a schematic cross-sectional view showing the electrochemical measurement system used in Example 1. FIG. 6 is an exploded perspective view of the measurement sealed container used in the denseness determination test of Example 1; 5 is a schematic cross-sectional view of a measurement system used in the denseness determination test of Example 1. FIG. FIG. 6 is a conceptual diagram showing an example of a He permeability measurement system used in Example 1. It is a schematic cross section of the sample holder used for the measurement system shown by FIG. 7A, and its periphery structure. It is a SEM image which shows the cross-section microstructure of the LDH separator produced in Example 1. FIG.

Method of Manufacturing Negative Electrode Structure The method of the present invention relates to a method of manufacturing a negative electrode structure for a zinc secondary battery. An example of the negative electrode structure is shown in FIGS. 1A and 1B. The negative electrode structure 10 shown in FIGS. 1A and 1B includes the negative electrode active material layer 12, the liquid retaining member 14 which covers or wraps the whole of the negative electrode active material layer 12, the entire negative electrode active material layer 12 and the liquid retaining member 14. And a covering or encasing LDH separator 16. The negative electrode active material layer 12 contains at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. In the present specification, “LDH separator” is a separator containing LDH and is defined as selectively passing hydroxide ions utilizing exclusively hydroxide ion conductivity of LDH. As described above, by covering or encasing the whole of the negative electrode active material layer 12 with the liquid retaining member 14 and the LDH separator 16, complicated sealing and bonding between the LDH separator and the battery container can be eliminated and zinc dendrite extension can be prevented. It is possible to provide a negative electrode structure capable of producing a zinc secondary battery (in particular, a laminated battery thereof) very simply and with high productivity.

That is, as described above, in the conventional zinc secondary battery, the separation of the positive electrode and the negative electrode by the LDH separator is accomplished carefully and carefully using a resin frame, an adhesive, etc. so as to ensure liquid tightness between the LDH separator and the battery container. The battery configuration and the manufacturing process are likely to be complicated. Such complication of the battery configuration and the manufacturing process can be particularly remarkable in the case of constructing a laminated battery. In this respect, in the negative electrode structure 10 manufactured by the method of the present invention, the whole of the negative electrode active material layer 12 is covered or encased with the liquid retaining member 14 and the LDH separator 16, so zinc can be formed by the negative electrode structure 10 itself. It has a function that can prevent a short circuit due to dendrite. Moreover, since the negative electrode structure 10 includes the liquid retaining member 14 between the negative electrode active material layer 12 and the LDH separator 16, if the electrolyte solution is injected into the negative electrode structure 10, the negative electrode chamber of the zinc secondary battery is zinc It can be simply configured in a form that can prevent dendrite extension. Therefore, when employing the negative electrode structure 10 manufactured by the method of the present invention for the preparation of a zinc secondary battery, separation of the positive electrode and the negative electrode by the LDH separator can be realized simply by laminating the positive electrode plate and the negative electrode structure. it can. In particular, when producing a laminated battery provided with a plurality of unit cells, it can be said to be extremely advantageous in that a desired configuration can be realized simply by alternately laminating the positive electrode plate and the negative electrode structure. This is because the LDH separator eliminates the need for the elaborate and careful sealing junction conventionally used to separate the positive and negative electrodes.

In the method of manufacturing a negative electrode structure according to the present invention, as shown in FIGS. 2 and 3, (a) covering the whole of the negative electrode active material layer 12 with the liquid retaining member 14 or encasing to obtain the first laminate 11; (B) sandwiching the entire first laminate 11 with the LDH separator 16 to obtain a second laminate 18; (c) sealing a predetermined outer edge S of the second laminate 18 to form a negative electrode structure Including the steps of The manufacturing method shown in FIG. 2 uses a single folded LDH separator 16 while the manufacturing method shown in FIG. 3 uses at least two unfolded LDH separators 16. In any case, as shown in these figures, a zinc secondary battery capable of preventing zinc dendrite extension (in particular, by covering or enclosing the whole of the negative electrode active material layer 12 with the liquid retaining member 14 and the LDH separator 16) The negative electrode structure 10 suitable for the laminated battery) can be manufactured efficiently. Each step will be specifically described below.

(A) Preparation of First Laminate by Lamination of Liquid Retaining Member In the step (a), as shown in FIGS. 2 and 3, the whole of the negative electrode active material layer 12 is covered or wrapped with the liquid retaining member 14. One laminate 11 is obtained (see (a) in the figure). The negative electrode active material layer 12 has a quadrilateral shape (typically, a square shape), but the liquid holding member 14 has a quadrilateral shape (typically, a square shape) larger than the negative electrode active material layer 12. Therefore, the whole of the negative electrode active material layer 12 can be covered or encased by the liquid retaining member 14. As described above, the liquid retaining member 14 surrounds the whole of the negative electrode active material layer 12 so that the electrolytic solution is always desirably kept around the negative electrode active material layer 12 when the electrolytic solution is injected into the negative electrode structure 10. It is possible to That is, the electrolytic solution can be uniformly present between the negative electrode active material layer 12 and the LDH separator 16, and the hydroxide ions are efficiently transferred between the negative electrode active material layer 12 and the LDH separator 16 be able to.

The negative electrode active material layer 12 contains at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. That is, zinc may be contained in any form of zinc metal, zinc compound and zinc alloy as long as it has electrochemical activity suitable for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate and the like, and a mixture of zinc metal and zinc oxide is more preferable. The negative electrode active material layer 12 may be formed in a gel form, or may be mixed with an electrolytic solution to form a negative electrode mixture. For example, a gelled negative electrode can be easily obtained by adding an electrolytic solution and a thickener to the negative electrode active material. Examples of the thickener include polyvinyl alcohol, polyacrylate, CMC, alginic acid and the like, and polyacrylic acid is preferable because it is excellent in chemical resistance to strong alkali.

As a zinc alloy, it is possible to use a mercury-free and lead-free zinc alloy known as a zinc-free zinc alloy. For example, a zinc alloy containing 0.01 to 0.1% by mass of indium, 0.005 to 0.02% by mass of bismuth, and 0.0035 to 0.015% by mass of aluminum has the effect of suppressing the generation of hydrogen gas So preferred. Indium and bismuth are particularly advantageous in improving the discharge performance. The use of the zinc alloy for the negative electrode can improve the safety by suppressing the generation of hydrogen gas by reducing the self-dissolution rate in the alkaline electrolyte.

The shape of the negative electrode material is not particularly limited, but is preferably in the form of powder, whereby the surface area is increased and it becomes possible to cope with high current discharge. In the case of a zinc alloy, the average particle diameter of the preferred negative electrode material is in the range of 3 to 100 μm in the short diameter, and within this range, the surface area is large, so that it is suitable for high current discharge It is easy to mix uniformly with the agent, and the handling at the time of battery assembly is also good.

Preferably, the negative electrode active material layer 12 is accompanied by the current collector 13. That is, it is preferable that the current collector 13 in contact with the negative electrode active material layer 12 be provided. In particular, the current collector 13 preferably has a current collector extension 13 a extending from one side of the negative electrode active material layer 12. In this case, it is desirable that the step (a) be performed so as not to cover or wrap the end portion of the current collector extension 13 a with the liquid retaining member 14. The tip of the current collector extension 13a is an exposed portion not covered by the liquid holding member 14 and the LDH separator 16, and the current collector 13 (especially, the current collector extension 13a) is exposed through this exposed portion. Is desirably connectable to the negative electrode terminal.

Preferred examples of the negative electrode current collector 13 include copper foil, copper expanded metal and copper punching metal, and more preferably copper expanded metal. In this case, for example, a negative electrode comprising a negative electrode / negative electrode current collector by applying a mixture comprising zinc oxide powder and / or zinc powder, and optionally a binder (for example, polytetrafluoroethylene particles) on copper expanded metal. The plate can be made preferably. At that time, it is also preferable to press-process the dried negative electrode plate (that is, the negative electrode / negative electrode current collector) to prevent the electrode active material from falling off and improve the electrode density.

The liquid holding member 14 is not particularly limited as long as it can hold the electrolytic solution, but is preferably a sheet-like member. Preferred examples of the liquid retaining member include nonwoven fabric, water absorbing resin, liquid retaining resin, porous sheet, and various spacers, and particularly preferably nonwoven fabric in that the negative electrode structure 10 with good performance can be produced at low cost. is there. The liquid holding member 14 preferably has a thickness of 0.01 to 0.20 mm, more preferably 0.02 to 0.20 mm, still more preferably 0.02 to 0.15 mm, particularly preferably It is 0.02 to 0.10 mm, most preferably 0.02 to 0.06 mm. When the thickness is within the above range, a sufficient amount of electrolytic solution can be held in the liquid holding member 14 while suppressing the entire size of the negative electrode structure 10 in a compact manner without waste. The liquid holding member 14 may have a quadrangular shape (typically, a rectangular shape) larger than the negative electrode active material layer 12 and may have the same size as the LDH separator 16 (or the folded LDH separator 16). .

When the liquid retaining member 14 is a sheet-like member, the number of sheets on one side is typically 1 (two sheets facing each other on both sides or one sheet folded), but may be two or more. For example, the whole of the negative electrode active material layer 12 may be covered or wrapped with a plurality of liquid retaining members 14 stacked.

(B) Preparation of Second Laminate by Lamination of LDH Separator In the step (b), as shown in FIGS. 2 and 3, the entire first laminate 11 is sandwiched by the LDH separator 16 to form a second laminate 18. Get At this time, the sandwiching of the first laminate 11 in the LDH separator 16 may be performed using one LDH separator 16 bent at one side, as shown in FIG. It may be performed using at least two LDH separators 16 which are not bent as shown in FIG. Similarly to the negative electrode active material layer 12 and the liquid holding member 14, the LDH separator 16 also has a quadrilateral shape (typically, a square shape). In either method, the sandwiching of the first laminate 11 in the LDH separator 16 is performed so as to form an overlapping portion of the LDH separator 16 protruding from the outer edge of the negative electrode active material layer 12 over the entire outer edge. By doing this, an extra portion for sealing the LDH separators 16 (which may have the liquid retaining member 14 therebetween) in the subsequent sealing step (c) is secured.

According to a preferred embodiment of the present invention, as shown in FIGS. 2 (b) and 2 (c), the whole of the first laminate 11 is subjected to negative electrode active with one LDH separator 16 folded along one side F. The second stacked body 18 is obtained by sandwiching an overlapping portion protruding from the outer edge of the material layer 12 so as to form the entire area of the outer edge. In this case, in the step (b), (i) folding one LDH separator 16 and (ii) folding the entire negative electrode active material layer 12 and the liquid retaining member 14 with the one folded LDH separator 16 And step. This can improve the manufacturing efficiency in that the number of sides to be sealed can be reduced in the subsequent step (c). In this respect, the LDH separator 16 including a porous substrate made of a polymeric material is particularly advantageous because it is flexible and can be easily bent. Although the LDH separator 16 has a quadrilateral shape (typically, a square shape), the LDH separator 16 is configured in a long shape so as to have a size suitable for the coating of the first laminate 11 when folded in half. Is preferred. In order to reduce the possibility of breakage due to bending of the LDH contained in the LDH separator 16, the above-mentioned bending is preferably performed so that the bent cross section of the LDH separator 16 is rounded.

According to another preferred embodiment of the present invention, as shown in FIGS. 3 (b) and 3 (c), the entire first laminated body 11 is formed of at least two quadrilateral-shaped LDH separators 16 which are not bent. The second stacked body 18 may be obtained by sandwiching an overlapping portion protruding from the outer edge of the negative electrode active material layer 12 so as to form the entire area of the outer edge. In this case, the step (b) may include sandwiching the whole of the negative electrode active material layer 12 and the liquid retaining member 14 with the two unfolded LDH separators 16. In this case, the manufacturing can be easily performed in that a simple planar LDH separator 16 may be used. The LDH separator 16 has a quadrilateral shape (typically, a quadrangular shape), but is not bent. Therefore, the LDH separator 16 may be configured to have a size suitable for covering the first stacked body 11 as it is.

In any of the embodiments, the step (b) may be performed so as to sandwich the outer peripheral portion of the liquid retaining member 14 between the LDH separators 16 forming the overlapping portion. In this way, sealing of the predetermined outer edge of the second stacked body 18 in the subsequent step (c) can be effectively performed by heat welding or ultrasonic welding. That is, rather than directly heat welding or ultrasonic welding LDH separators 16 with each other, heat welding or ultrasonic welding may be indirectly performed by interposing a heat-welding liquid retaining member 14 between them. As a result, since the heat welding property of the liquid retaining member 14 itself can be used, sealing can be performed more effectively. That is, the end portion of the liquid retaining member 14 to be sealed can be used as if it is a hot melt adhesive. As a preferable example of the liquid retaining member 11 in this case, a nonwoven fabric, in particular, a nonwoven fabric made of a thermoplastic resin (for example, polyethylene, polypropylene) can be mentioned. In this aspect, the size of the liquid retaining member 14 can be the same size as the LDH separator 16 (or the folded LDH separator 16), and the outer edge of the LDH separator 16 and the outer edge of the liquid retaining member 14 coincide with each other. It can be.

When the distal end portion of the current collector extension 13 a is not covered or enclosed by the liquid holding member 14, the step (b) is performed such that the distal end of the current collector extension 13 a is not sandwiched by the LDH separator 16. As a result, the tip end portion of the current collector extension 13a forms an exposed portion not covered by the liquid retaining member 14 and the LDH separator 16. Thus, the current collector 13 (particularly, the current collector extension 13a) can be desirably connected to the negative electrode terminal (not shown) through the exposed portion. In this case, as shown in FIG. 4, a predetermined margin M (for example, a distance of 1 to 5 mm) so that the LDH separator 16 sufficiently hides the end of the negative electrode active material layer 12 on the current collector extension 13a side. It is preferable to cover or wrap around. By so doing, extension of zinc dendrite from the end of the negative electrode active material layer 12 on the current collector extension 13a side or in the vicinity thereof can be prevented more effectively.

Preferably, the LDH separator 16 comprises (and is typically composed of) LDH and a porous substrate, such that the LDH separator 16 exhibits hydroxide ion conductivity and gas impermeability (hence, Preferably, the LDH blocks the pores of the porous substrate so as to function as an LDH separator exhibiting hydroxide ion conductivity. The porous substrate is preferably made of a polymeric material, and it is particularly preferred that the LDH be incorporated throughout the thickness direction of the polymeric porous substrate. Various preferred embodiments of the LDH separator 16 will be described in detail later.

The number of LDH separators 16 is typically one per side (two sheets facing each other or two folded ones), but may be two or more. For example, the entire first laminate 11 may be covered or wrapped with a plurality of stacked LDH separators 16.

(C) Sealing of the predetermined outer edge of the second laminate In the step (c), as shown in FIGS. 2 and 3, the overlapping portion belonging to the outer edge of the predetermined side of the second laminate 18 is sealed. Thus, the negative electrode structure 10 is obtained in which the outer edges of at least two sides adjacent to each other are closed. Here, "at least two sides adjacent to each other" means that one end of one side is in contact with one end of the other side. In addition, "the outer edge is closed" may be in a form in which the outer edge is folded or in a form in which the outer edge is sealed. In any case, the negative electrode active material is mounted on the zinc secondary battery by closing the outer edges (which are also the outer edges of the LDH separator 16) of at least two adjacent sides of the second stacked body 18 Layer 12 can be reliably isolated from the positive electrode, and the extension of zinc dendrite from the outer edge can be effectively prevented. For example, in the case of using a single folded LDH separator 16, as shown in FIG. 2C, the outer edge S (or S) of at least one side adjacent to the folded side F of the second laminated body 18 And S ′) are sealed. Note that the outer edge S ′ in the figure means a side that may or may not be closed. On the other hand, when using two unfolded LDH separators 16, as shown in FIG. 3C, the outer edges of at least two adjacent sides S (or S and S ') of the second stacked body 18 are provided. Seal the overlapping part belonging to However, in the case where the current collector extension 13a is provided, the side S (or S and S ') on which sealing is performed is extended from the current collector in order to allow extension of the current collector extension 13a. It is desirable that the side does not overlap with the protrusion 13a. In either method, as a result, the negative electrode structure 10 in which the outer edges of at least two sides adjacent to each other are closed is obtained.

As shown in FIG. 2, the step (b) includes the steps of (i) bending one LDH separator 16 and (ii) bending the one negative electrode active material layer 12 and the liquid retaining member 14 with the one LDH separator 16. In the embodiment including the step of sandwiching the whole, the step (c) seals the overlapping portion belonging to the outer edge of at least one side S (or S and S ') adjacent to the bent side F of the second laminate 18 It is preferable to include stopping. As necessary, the step (c) may be performed to seal the overlapping portion belonging to the outer edges S and S ′ of the two sides adjacent to the bent side F of the second stacked body 18, In this case, it is possible to obtain a negative electrode structure in which the outer edges of the three sides are closed (so that extension of zinc dendrite can be prevented more effectively).

On the other hand, as shown in FIG. 3, in the embodiment in which the step (b) includes sandwiching the whole of the negative electrode active material layer 12 and the liquid retaining member 14 between two unfolded LDH separators 16, the step (c Preferably includes the step of sealing the overlapping portion belonging to the outer edge of at least two sides S, S (or S, S and S ′) adjacent to each other of the second laminate 18. If necessary, the step (c) may seal the overlapping portion belonging to the outer edge of the three sides S, S and S ′ of the second stacked body 18, in which case the outer edges of the three sides are It is possible to obtain a negative electrode structure that can be closed (hence the zinc dendrite extension can be prevented more effectively).

In any form, sealing may be performed by any method and is not particularly limited. Preferred examples of sealing techniques include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. Although heat welding and ultrasonic welding may be performed using a commercially available heat sealer or the like, in this case, as described above, the outer peripheral portion of the liquid holding member 14 is sandwiched between the LDH separators 16 forming the overlapping portion. Thermal welding and ultrasonic welding are preferable in that sealing can be more effectively performed. On the other hand, although a commercial item may be used for an adhesive agent, an adhesive tape, and a sealing tape, in order to prevent deterioration in an alkaline electrolyte solution, what contains the resin which has alkali resistance is preferable. From this point of view, examples of preferable adhesives include epoxy resin adhesives, natural resin adhesives, modified olefin resin adhesives, and modified silicone resin adhesives, among which epoxy resin adhesives are resistant It is more preferable in that it is particularly excellent in alkalinity. As a product example of the epoxy resin-based adhesive, an epoxy adhesive Hysol (registered trademark) (manufactured by Henkel) may be mentioned.

The negative electrode structure 10 thus obtained is such that the outer edges of at least two sides adjacent to each other are closed, but conversely speaking, even if one or two sides of the outer edge of the negative electrode structure 10 are open. It means good. For example, even if the upper edge one side of the outer edge of the negative electrode structure 10 is opened, if a solution is injected so that the electrolyte does not reach the upper edge one side during the preparation of the zinc secondary battery, the upper edge one side Since there is no electrolytic solution, it is possible to avoid the problems of liquid leakage and zinc dendrite extension. In this regard, the negative electrode structure 10 can function as a main component of the sealed zinc secondary battery by being accommodated together with the positive electrode in the sealed container with the electrolytic solution also contained therein. For this reason, since it is sufficient if the hermeticity is secured in the sealed container to be finally accommodated, the negative electrode structure 10 itself can be a simple configuration of the upper open type. Also, by opening one side of the outer edge of the negative electrode structure 10, the current collector extension 13a can be extended therefrom. The open outer edge 1 side for extending the current collector extension 13a may be an upper end 1 side providing an upper open portion, or may be another outer edge 1 side.

LDH Separator The LDH separator 16 is a separator containing layered double hydroxide (LDH), and when incorporated in a zinc secondary battery, separates the positive electrode plate and the negative electrode plate so that they can conduct hydroxide ions. . That is, the LDH separator 16 exhibits a function as a hydroxide ion conductive separator. Preferred LDH separators 16 are gas impermeable and / or water impermeable. In other words, the LDH separator 16 is preferably densified so as to be gas impermeable and / or water impermeable. In the present specification, "having gas impermeability" refers to one side of the object to be measured being contacted with helium gas at a differential pressure of 0.5 atm, as described in Patent Documents 2 and 3. This also means that no bubbles due to helium gas are observed from the other side. Further, in the present specification, "having water impermeability" means that water in contact with one side of the object to be measured does not permeate to the other side as described in Patent Documents 2 and 3. . That is, the fact that the LDH separator 16 has gas impermeability and / or water impermeability means that the LDH separator 16 has a high degree of compactness that is impervious to gas or water, and water permeability or gas It means that it is not a porous film or other porous material having permeability. By so doing, the LDH separator 16 can selectively pass only hydroxide ions due to its hydroxide ion conductivity, and can exhibit a function as a battery separator. Therefore, the configuration is extremely effective for physically preventing penetration of the separator due to zinc dendrite generated during charging to prevent short circuit between positive and negative electrodes. Since the LDH separator 16 has hydroxide ion conductivity, it enables efficient movement of hydroxide ions required between the positive electrode plate and the negative electrode plate to realize charge / discharge reactions in the positive electrode plate and the negative electrode plate. Can.

The LDH separator 16 preferably has a He permeability per unit area of 10 cm / min · atm or less, more preferably 5.0 cm / min · atm or less, and still more preferably 1.0 cm / min · atm or less . A separator having a He permeability of 10 cm / min · atm or less can extremely effectively suppress the permeation of Zn (typically, the permeation of zinc ions or zincate ions) in the electrolytic solution. Thus, the separator of the present embodiment is considered to be capable of effectively suppressing the growth of zinc dendrite when used in a zinc secondary battery because Zn permeation is significantly suppressed. The He permeability is through the steps of supplying He gas to one side of the separator and allowing the separator to permeate He gas, and calculating the He permeability to evaluate the compactness of the hydroxide ion conductive separator. It is measured. The He permeability is expressed by the formula of F / (P × S) using the permeation amount F of He gas per unit time, the differential pressure P applied to the separator during He gas permeation, and the membrane area S through which He gas permeates. calculate. Thus, by evaluating the gas permeability using He gas, it is possible to evaluate the presence or absence of compactness at an extremely high level, and as a result, substances other than hydroxide ions (especially zinc dendrite growth) It is possible to effectively evaluate a high degree of compactness such as not transmitting as much as possible Zn (permeating only a very small amount). This is because He gas has the smallest structural unit among a wide variety of atoms or molecules that can constitute the gas, and the reactivity is extremely low. That is, He forms He gas with He atoms alone without forming molecules. In this respect, since hydrogen gas is composed of H ₂ molecules, a single He atom is smaller as a gas constituent unit. First of all, H ₂ gas is dangerous because of flammable gas. And, by adopting the indicator of He gas permeability defined by the above-mentioned equation, objective evaluation regarding compactness can be simply performed regardless of various sample sizes and differences in measurement conditions. Thus, it can be evaluated simply, safely and effectively whether the separator has a sufficiently high compactness suitable for a zinc secondary battery separator. The measurement of the He permeability can be preferably performed according to the procedure shown in Evaluation 7 of Example 1 described later.

As generally known, the LDH is composed of a plurality of hydroxide base layers and an intermediate layer interposed between the plurality of hydroxide base layers. The hydroxide base layer is mainly composed of metal elements (typically metal ions) and OH groups. The interlayer of LDH is composed of anions and H ₂ O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, anions in the LDH is OH ^- containing and / or _CO ^{3 2-} and. Also, LDH has excellent ion conductivity due to its inherent properties.

Typically, LDH ^is, 2 O (wherein _{^{_{_{^{M 2+ 1-x M 3+ x}}}}} (OH) 2 A n- x / n · mH, M 2+ is a divalent ^{cation, M 3+} is a trivalent A ^{n −} is a cation, ⁿ is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. It is known as being represented. In the above basic composition formula, M ²⁺ may be any divalent cation, but preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , more preferably Mg ²⁺ . M ^{3 +} may be any trivalent cation, but preferred examples include Al ^{3 +} or Cr ^{3 +} , and more preferably Al ^{3 +} . An ^- can be any anion but preferred examples include OH ^- and CO ₃ ^2- . Accordingly, in the above basic ^{formula, M 2+} comprises ^{Mg ^2+,} ^{M 3+} comprises ^{Al ^3+,} ^{A n-is} OH ^- and / or _CO preferably contains ^{3 2-.} n is an integer of 1 or more, preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. m is an arbitrary number meaning the number of moles of water, and is a real number of 0 or more, typically more than 0 or 1 or more. However, the above-mentioned basic composition formula is only a formula of "basic composition" typically illustrated typically regarding LDH, and can substitute a component ion suitably. For example, in the above basic composition formula, part or all of M ³⁺ may be replaced by a tetravalent or higher valence cation, in which case the coefficient x / n of the anion A ⁿ⁻ in the above general formula May be changed as appropriate.

For example, the hydroxide base layer of LDH may be composed of Ni, Ti, OH groups, and optionally unavoidable impurities. The interlayer of LDH is composed of anions and H ₂ O as described above. The alternate layered structure itself of the hydroxide basic layer and the intermediate layer is basically the same as the generally known alternate layered structure of LDH, but the LDH of this embodiment is mainly composed of Ni, the hydroxide basic layer of the LDH. By comprising Ti and OH groups, excellent alkali resistance can be exhibited. The reason is not necessarily clear, but it is considered that an element (for example, Al) considered to be easily eluted in an alkaline solution is not intentionally or positively added to the LDH of this embodiment. Even so, the LDH of this embodiment can also exhibit high ion conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can take the form of nickel ion. The nickel ion in LDH is typically considered to be Ni ²⁺ but is not particularly limited as it may have other valences such as Ni ³⁺ . Ti in LDH can take the form of titanium ions. The titanium ion in LDH is typically considered to be Ti ⁴⁺ , but is not particularly limited as other valences such as Ti ³⁺ may also be present. Unavoidable impurities are optional elements that can be inevitably mixed in the manufacturing method, and may be mixed into LDH derived from, for example, a raw material or a base material. As described above, since the valences of Ni and Ti are not necessarily known, it is impractical or impossible to exactly specify LDH by a general formula. Assuming that the hydroxide base layer is mainly composed of Ni ²⁺ , Ti ⁴⁺ and OH groups, the corresponding LDH has the general formula: Ni ²⁺ _1−x Ti ⁴⁺ _x (OH) ₂ ^{An −} _{2x / n} · mH ₂ O (wherein, A ⁿ⁻ is an n-valent anion, n is an integer of 1 or more, preferably 1 or 2, and 0 <x <1 preferably 0.01 ≦ x ≦ 0.5, m is 0 or more, and is typically a real number greater than 0 or 1 or more. However, the above general formula should be understood as "basic composition" to the last, and other elements or ions (other valences of the same element to the extent that elements such as Ni ²⁺ and Ti ⁴⁺ do not impair the basic characteristics of LDH) It should be understood as being replaceable with a number of elements or ions or elements or ions which may be inevitably mixed in the preparation process.

Alternatively, the hydroxide base layer of LDH may contain Ni, Al, Ti and OH groups. The middle layer is composed of anions and H ₂ O as described above. The alternate layered structure itself of the hydroxide basic layer and the intermediate layer is basically the same as the generally known alternate layered structure of LDH, but in the LDH of this embodiment, the hydroxide basic layer of LDH is made of Ni, Al Excellent alkali resistance can be exhibited by using predetermined elements or ions containing Ti, and OH groups. The reason is not necessarily clear, but the LDH of this embodiment is considered to be because Al, which was conventionally considered to be easily eluted in an alkaline solution, becomes difficult to be eluted in an alkaline solution due to any interaction with Ni and Ti. Be Even so, the LDH of this embodiment can also exhibit high ion conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can take the form of nickel ion. The nickel ion in LDH is typically considered to be Ni ²⁺ but is not particularly limited as it may have other valences such as Ni ³⁺ . Al in LDH can take the form of aluminum ion. The aluminum ion in LDH is typically considered to be Al ³⁺ , but is not particularly limited as it may have other valences. Ti in LDH can take the form of titanium ions. The titanium ion in LDH is typically considered to be Ti ⁴⁺ , but is not particularly limited as other valences such as Ti ³⁺ may also be present. The hydroxide base layer may contain other elements or ions as long as it contains Ni, Al, Ti and OH groups. However, it is preferable that the hydroxide base layer contains Ni, Al, Ti and OH groups as main components. That is, the hydroxide base layer preferably consists mainly of Ni, Al, Ti and OH groups. Thus, the hydroxide base layer is typically composed of Ni, Al, Ti, OH groups and optionally unavoidable impurities. Unavoidable impurities are optional elements that can be inevitably mixed in the manufacturing method, and may be mixed into LDH derived from, for example, a raw material or a base material. As described above, since the valences of Ni, Al and Ti are not necessarily determined, it is impractical or impossible to specify LDH strictly by the general formula. Assuming that the hydroxide base layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ and OH groups, the corresponding LDH has the general formula: Ni ²⁺ _1−x−y Al ³⁺ _x Ti ^{4 +} _y (OH) ₂ A ^n- _{(x + 2 y) / n m} H ₂ O (wherein, ⁿ is an n-valent anion, n is an integer of 1 or more, preferably 1 or 2, 0 <x <1, preferably 0.01 ≦ x ≦ 0.5, 0 <y <1, preferably 0.01 ≦ y ≦ 0.5, 0 <x + y <1, m is 0 or more, typically 0 It can be represented by a basic composition of “more than one or more real numbers”. However, the above general formula should be understood as "basic composition" to the last, and other elements or ions (the same element as the elements such as Ni ²⁺ , Al ³⁺ , Ti ^4+, etc. do not impair the basic properties of LDH) It should be understood that it can be replaced by other valence elements or ions, and elements or ions which can be inevitably mixed in the preparation method.

It is needless to say that the porous substrate has water permeability and gas permeability so that when it is incorporated into a zinc secondary battery, the electrolyte can reach the LDH, but the porous substrate is It is also possible to hold hydroxide ions more stably by the LDH separator 16 due to the presence. In addition, since the porous base material can impart strength, the LDH separator 16 can be thinned to reduce resistance.

As described above, the LDH separator 16 preferably includes (typically consists of) LDH and a porous substrate, and the LDH separator 16 exhibits hydroxide ion conductivity and gas impermeability. Preferably, the LDH blocks the pores of the porous substrate (so that it functions as an LDH separator exhibiting hydroxide ion conductivity). The porous substrate is preferably made of a polymeric material, and it is particularly preferred that the LDH be incorporated throughout the thickness direction of the polymeric porous substrate. The thickness of the LDH separator 16 is preferably 5 to 200 μm, more preferably 5 to 100 μm, and still more preferably 5 to 30 μm.

The porous substrate is preferably composed of a polymeric material. The porous polymer substrate has 1) flexibility (therefore, it is difficult to be broken even if it is thin), 2) it is easy to increase the porosity, 3) it is easy to increase the conductivity (the thickness is increased while the porosity is increased) To be thin) and 4) easy to manufacture and handle. In addition, taking advantage of the flexibility derived from the above 1), 5) the LDH separator 16 including a porous base material made of a polymer material can be easily bent or sealed and joined as described above There is another advantage that at least one side of the outer edge of the negative electrode structure 10 can be easily formed in a closed state (in the case of bending, it is also advantageous to be able to reduce the sealing process of one outer edge). Preferred examples of the polymer material include polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrophilized fluorocarbon resin (tetrafluorinated resin: such as PTFE), cellulose, nylon, polyethylene and any combination thereof Can be mentioned. All the various preferable materials mentioned above have alkali resistance as resistance with respect to the electrolyte solution of a battery. Particularly preferable polymer materials are polyolefins such as polypropylene and polyethylene in that they are excellent in hot water resistance, acid resistance and alkali resistance and are low in cost, and most preferably polypropylene. When the porous substrate is composed of a polymeric material, the LDH layer is incorporated throughout the thickness direction of the porous substrate (for example, most or almost all pores inside the porous substrate are filled with LDH) Is particularly preferred. The preferable thickness of the porous polymer substrate in this case is 5 to 200 μm, more preferably 5 to 100 μm, and still more preferably 5 to 30 μm. As such a polymeric porous substrate, a microporous film commercially available as a separator for lithium batteries can be preferably used, or commercially available cellophane can also be used.

The porous substrate preferably has an average pore size of at most 100 μm or less, more preferably at most 50 μm or less, eg typically 0.001 to 1.5 μm, more typically 0.001典型 1.25 μm, more typically 0.001 to 1.0 μm, particularly typically 0.001 to 0.75 μm, and most typically 0.001 to 0.5 μm. By setting the content within these ranges, it is possible to form a dense LDH separator so as to exhibit gas impermeability while securing desired permeability and strength as a support on the porous substrate. In the present invention, the measurement of the average pore diameter can be performed by measuring the longest distance of pores based on the electron microscope image of the surface of the porous substrate. The magnification of the electron microscope image used for this measurement is 20000 times or more, and all the pore diameters obtained are arranged in order of size, and the upper 15 points and lower 15 points in order of closeness from the average value An average pore diameter can be obtained by calculating an average value for two fields of view. For length measurement, a length measurement function of software of SEM, image analysis software (for example, Photoshop, manufactured by Adobe), or the like can be used.

The porous substrate preferably has a porosity of 10 to 60%, more preferably 15 to 55%, still more preferably 20 to 50%. By setting the content within these ranges, it is possible to form a dense LDH separator so as to exhibit gas impermeability while securing desired permeability and strength as a support on the porous substrate. The porosity of the porous substrate can be preferably measured by the Archimedes method. However, when the porous substrate is made of a polymer material and LDH is incorporated throughout the thickness direction of the porous substrate, the porosity of the porous substrate is preferably 30 to 60%, and more preferably Is 40 to 60%.

The method for producing the LDH separator 16 is not particularly limited, and the LDH separator 16 may be produced by appropriately changing various conditions of a known method for producing an LDH-containing functional layer and a composite material (ie, LDH separator) (see, for example, patent documents 1 to 3). can do. For example, (1) a porous substrate is prepared, and (2) a titanium oxide sol or a mixed sol of alumina and titania is applied to the porous substrate and heat treated to form a titanium oxide layer or an alumina-titania layer. (3) The porous base material is immersed in a raw material aqueous solution containing nickel ions (Ni ²⁺ ) and urea, and (4) the porous base material is hydrothermally treated in the raw material aqueous solution to make the LDH-containing functional layer a porous base material The LDH-containing functional layer and the composite material (i.e., LDH separator) can be manufactured by forming on the top and / or the porous substrate. In particular, by forming the titanium oxide layer or the alumina-titania layer on the porous substrate in the above step (2), not only the raw material of LDH is provided, but the porous substrate is made to function as a starting point of LDH crystal growth. The highly densified LDH-containing functional layer can be uniformly formed uniformly on the surface. Further, due to the presence of urea in the step (3), the pH value is raised by the generation of ammonia in the solution by utilizing the hydrolysis of urea, and the coexisting metal ions form a hydroxide. LDH can be obtained by In addition, since the hydrolysis involves the generation of carbon dioxide, it is possible to obtain a carbonate ion LDH as the anion.

In particular, when producing a composite material (i.e., LDH separator) in which the porous substrate is composed of a polymer material and the functional layer is incorporated throughout the thickness direction of the porous substrate, the alumina in the above (2) The application of the mixed sol of titania and titania to the substrate is preferably carried out in such a manner that the mixed sol penetrates the whole or most of the interior of the substrate. In this way, most or almost all pores inside the porous substrate can be finally filled with LDH. Examples of preferred coating techniques include dip coating, filtration coating and the like, with dip coating being particularly preferred. The adhesion amount of the mixed sol can be adjusted by adjusting the number of times of application such as dip coating. The base on which the mixed sol is applied by dip coating or the like may be dried, and then the steps (3) and (4) may be performed.

Zinc Secondary Battery The negative electrode structure produced by the method of the present invention is preferably applied to a zinc secondary battery. Therefore, according to a preferred embodiment of the present invention, there is provided a zinc secondary battery comprising a positive electrode, a negative electrode structure and an electrolytic solution, wherein the positive electrode and the negative electrode active material layer are separated from each other via the LDH separator. . The zinc secondary battery of the present invention is not particularly limited as long as it is a secondary battery using zinc as a negative electrode and an electrolytic solution (typically, an aqueous alkali metal hydroxide solution). Therefore, a nickel zinc secondary battery, a silver oxide zinc secondary battery, a manganese zinc oxide secondary battery, a zinc air secondary battery, and various other alkaline zinc secondary batteries can be used. In particular, nickel zinc secondary batteries and zinc air secondary batteries are preferable. For example, it is preferable that the positive electrode contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery constitutes a nickel zinc secondary battery. Alternatively, the positive electrode may be an air electrode, whereby the zinc secondary battery may form a zinc-air secondary battery.

The LDH separator that can be used in the present invention will be more specifically described by the following example.

Example 1
Using a polymeric porous substrate, an LDH separator containing Ni, Al and Ti-containing LDH was prepared and evaluated according to the following procedure.

(1) Preparation of Polymeric Porous Substrate A commercially available polypropylene porous substrate having a porosity of 50%, an average pore diameter of 0.1 μm and a thickness of 20 μm should be 2.0 cm × 2.0 cm in size. Cut out.

(2) Alumina-titania sol coating on polymeric porous substrate Amorphous alumina solution (Al-ML15, manufactured by Taki Chemical Co., Ltd.) and titanium oxide sol solution (M6, manufactured by Taki Chemical Co., Ltd.) It mixed so that it might be set to molar ratio = 2, and prepared mixed sol. The mixed sol was applied by dip coating to the substrate prepared in (1) above. The dip coating was performed by immersing the substrate in 100 ml of the mixed sol, pulling it vertically, and drying it in a dryer at 90 ° C. for 5 minutes.

(3) As the manufacturing raw material of the raw aqueous solution, prepared nickel nitrate hexahydrate _{_{(Ni (NO 3) 2 ·}} 6H 2 O, manufactured by Kanto Chemical Co., Inc. and urea _((NH ₂₎ 2 CO, manufactured by Sigma-Aldrich) Nickel nitrate hexahydrate was weighed into a beaker so as to be 0.015 mol / L, and ion-exchanged water was added there to make the total amount 75 ml. urea / NO 3 in _- urea weighed at a ratio ^(molar ratio) = 16 was added and further stirred to obtain a raw material solution.

(4) Film Formation by Hydrothermal Treatment Both a raw material aqueous solution and a dip-coated substrate were enclosed in a Teflon (registered trademark) closed vessel (autoclave vessel, inner volume 100 ml, outer jacket made of stainless steel). At this time, the substrate was floated and fixed from the bottom of a Teflon (registered trademark) closed container, and was horizontally placed so that the solution was in contact with both surfaces of the substrate. Thereafter, hydrothermal treatment was performed at a hydrothermal temperature of 120 ° C. for 24 hours to form LDH on the surface of the substrate and the inside. After an elapse of a predetermined time, the substrate was removed from the closed vessel, washed with ion-exchanged water, and dried at 70 ° C. for 10 hours to obtain LDH incorporated in a porous substrate. Thus, an LDH separator was obtained.

(5) Evaluation The following evaluations were performed on the obtained LDH separator.

Evaluation 1 : Identification of the LDH Separator The crystal phase of the LDH separator is measured under the measurement conditions of voltage: 50 kV, current value: 300 mA, measurement range: 10 to 70 ° with an X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation) The XRD profile was obtained. About the obtained XRD profile, JCPDS card NO. Identification was performed using the diffraction peak of LDH (hydrotalcite-like compound) described in 35-0964.

Evaluation 2 : Observation of Microstructure The surface microstructure of the LDH separator was observed using a scanning electron microscope (SEM, JSM-6610 LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV. In addition, after obtaining a cross-sectional polished surface of the LDH separator with an ion milling apparatus (manufactured by Hitachi High-Technologies Corporation, IM 4000), the microstructure of the cross-sectional polished surface was observed by SEM under the same conditions as the surface microstructure.

Evaluation 3 : Elemental Analysis Evaluation (EDS)
The cross section polisher (CP) was polished so that the cross-section polished surface of the LDH separator could be observed. A cross-sectional image of the LDH separator was acquired for one field of view at a magnification of 10000 by FE-SEM (ULTRA 55, manufactured by Carl Zeiss). Elemental analysis of the LDH film on the substrate surface and the LDH part inside the substrate (point analysis) of this cross-sectional image was carried out using an EDS analyzer (NORAN System SIX, manufactured by Thermo Fisher Scientific) under conditions of an acceleration voltage of 15 kV. went.

Evaluation 4 : Evaluation of alkali resistance Zinc oxide was dissolved in a 6 mol / L aqueous potassium hydroxide solution to obtain a 5 mol / L aqueous potassium hydroxide solution containing zinc oxide at a concentration of 0.4 mol / L. 15 ml of the potassium hydroxide aqueous solution thus obtained was placed in a Teflon (registered trademark) closed container. A 1 cm × 0.6 cm size LDH separator was placed at the bottom of the closed container and the lid closed. Then, after holding at 70 ° C. for 3 weeks (ie, 504 hours) or 7 weeks (ie, 1176 hours), the LDH separator was removed from the closed vessel. The removed LDH separator was dried overnight at room temperature. The obtained sample was subjected to microstructure observation by SEM and crystal structure observation by XRD.

Evaluation 5 : Measurement of ionic conductivity The conductivity of the LDH separator in the electrolytic solution was measured as follows using the electrochemical measurement system shown in FIG. The LDH separator sample S was sandwiched by 1 mm thick silicone packing 40 from both sides and incorporated into a PTFE flange type cell 42 with an inner diameter of 6 mm. As the electrode 46, a # 100 mesh nickel wire mesh was incorporated into the cell 42 in a cylindrical shape with a diameter of 6 mm so that the distance between the electrodes was 2.2 mm. As the electrolyte solution 44, 6 M KOH aqueous solution was filled in the cell 42. Measured using an electrochemical measurement system (potentio / galvano stud-frequency response analyzer, model 1287A and 1255B made by Solartron) in the frequency range of 1 MHz to 0.1 Hz and the applied voltage of 10 mV, and intercepting the real axis The resistance of the LDH separator sample S was taken as The same measurement as above was performed only on the porous substrate without the LDH film, and the resistance of the porous substrate alone was also determined. The difference between the resistance of the LDH separator sample S and the resistance of only the substrate was taken as the resistance of the LDH film. The conductivity was determined using the resistance of the LDH film and the thickness and area of the LDH.

Evaluation 6 : Fineness determination test In order to confirm that the LDH separator is dense enough to exhibit gas impermeability, a fineness determination test was conducted as follows. First, as shown in FIGS. 6A and 6B, an acrylic container 130 without a lid, and an alumina jig 132 having a shape and a size that can function as a lid of the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying a gas therein. Further, an opening 132a having a diameter of 5 mm is formed in the alumina jig 132, and a recess 132b for placing a sample is formed along the outer periphery of the opening 132a. The epoxy adhesive 134 was applied to the depression 132 b of the alumina jig 132, and the LDH separator sample 136 was placed on the depression 132 b and adhered to the alumina jig 132 in an airtight and liquid tight manner. Then, the alumina jig 132 to which the LDH separator sample 136 is bonded is adhered to the upper end of the acrylic container 130 in an airtight and liquid tight manner using the silicone adhesive 138 so as to completely close the opening of the acrylic container 130. The measurement sealed container 140 was obtained. The measurement airtight container 140 was placed in the water tank 142, and the gas supply port 130a of the acrylic container 130 was connected to the pressure gauge 144 and the flow meter 146 so that helium gas could be supplied into the acrylic container 130. The water 143 was put in the water tank 142, and the measurement sealed container 140 was completely submerged. At this time, the inside of the sealed container for measurement 140 is sufficiently airtight and liquid-tight, and one side of the LDH separator sample 136 is exposed to the internal space of the sealed container for measurement 140 while the LDH separator sample 136 is exposed. The other side of the water is in contact with the water in the water tank 142. In this state, helium gas was introduced into the acrylic container 130 through the gas supply port 130 a into the measurement sealed container 140. By controlling the pressure gauge 144 and the flow meter 146, the pressure difference between the inside and the outside of the LDH separator sample 136 is 0.5 atm (that is, the pressure applied to the side in contact with the helium gas is 0.5 atm higher than the water pressure applied to the opposite side) Then, it was observed whether bubbles of helium gas were generated from the LDH separator sample 136 in water. As a result, when generation of bubbles due to helium gas was not observed, it was determined that the LDH separator sample 136 had high density so as to exhibit gas impermeability.

Evaluation 7 : He Permeation Measurement In order to evaluate the compactness of the LDH separator from the viewpoint of He permeability, a He permeation test was performed as follows. First, the He permeability measurement system 310 shown in FIGS. 7A and 7B was constructed. In the He permeability measurement system 310, the He gas from the gas cylinder filled with the He gas is supplied to the sample holder 316 via the pressure gauge 312 and the flow meter 314 (digital flow meter), and the LDH held by the sample holder 316 It was configured to permeate from one side of the separator 318 to the other side to be discharged.

The sample holder 316 has a structure provided with a gas supply port 316a, a sealed space 316b and a gas discharge port 316c, and was assembled as follows. First, the adhesive 322 was applied along the outer periphery of the LDH separator 318 and attached to a jig 324 (made of ABS resin) having an opening at the center. Packing made of butyl rubber is disposed as sealing

members

326a and 326b at the upper and lower ends of the jig 324, and

support members

328a and 328b (made of PTFE are provided with openings made of flanges from the outside of the sealing

members

326a and 326b) It was pinched by). Thus, the sealed space 316b is defined by the LDH separator 318, the jig 324, the sealing member 326a, and the support member 328a. The

support members

328a and 328b were tightly tightened with each other by means of fastening means 330 using a screw so that no He gas leaked from portions other than the gas outlet 316c. The gas supply pipe 334 was connected to the gas supply port 316 a of the sample holder 316 thus assembled via the joint 332.

Then, He gas was supplied to the He permeability measurement system 310 through the gas supply pipe 334, and permeated to the LDH separator 318 held in the sample holder 316. At this time, the gas supply pressure and flow rate were monitored by the pressure gauge 312 and the flow meter 314. After penetrating He gas for 1 to 30 minutes, the He permeability was calculated. The He permeability is calculated by the amount of He gas permeation F (cm ³ / min) per unit time, the differential pressure P (atm) applied to the LDH separator during He gas permeation, and the membrane area S (cm) through which He gas permeates. ^It calculated by the formula of F / (PxS) using ² ). The permeation amount F (cm ³ / min) of He gas was read directly from the flow meter 314. Further, as the differential pressure P, a gauge pressure read from the pressure gauge 312 was used. The He gas was supplied such that the differential pressure P was in the range of 0.05 to 0.90 atm.

(6) Evaluation results The evaluation results were as follows.
-Evaluation 1: From the obtained XRD profile, it was identified that the crystal phase contained in the LDH separator is LDH (hydrotalcite compound).
-Evaluation 2: The SEM image of the cross-sectional microstructure of the LDH separator was as shown in FIG. As can be seen from FIG. 8, it was observed that the LDH was incorporated throughout the thickness direction of the porous substrate, that is, the pores of the porous substrate were uniformly filled with the LDH.
Evaluation 3: As a result of EDS elemental analysis, LDH constituent elements C, Al, Ti and Ni were detected from the LDH separator. That is, Al, Ti and Ni are constituent elements of the hydroxide base layer, while C corresponds to CO ₃ ^2- which is an anion constituting the intermediate layer of LDH.
Evaluation 4: No change was observed in the microstructure of the LDH separator even after immersion in a 70 ° C. aqueous potassium hydroxide solution for 3 to 7 weeks.
-Evaluation 5: The conductivity of the LDH separator was 2.0 mS / cm.
-Evaluation 6: It was confirmed that the LDH separator has high compactness so as to exhibit gas impermeability.
Evaluation 7: The He permeability of the LDH separator was 0.0 cm / min · atm.

Claims

A method of manufacturing a negative electrode structure for a zinc secondary battery, comprising:
(A) Covering the whole of a quadrilateral-shaped negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy and a zinc compound with a quadrilateral-shaped liquid holding member of a larger size Or encasing to obtain a first laminate;
(B) The entire first laminate is formed of one quadrilateral layered double hydroxide (LDH) separator folded at one side or at least two quadrilateral LDH separators not folded. Sandwiching an overlap portion protruding from the outer edge of the negative electrode active material layer so as to form the entire area of the outer edge to obtain a second laminate;
(C) When using the one folded LDH separator, the overlapping portion belonging to the outer edge of at least one side adjacent to the folded side of the second laminate is sealed or not folded In the case of using two LDH separators, a negative electrode structure in which overlapping portions belonging to the outer edges of at least two adjacent sides of the second laminate are sealed, and as a result, the outer edges of at least two adjacent sides are closed. The process of gaining a body,
Method, including.
The method according to claim 1, wherein the liquid retaining member is a non-woven fabric.
The step (b) includes the steps of: bending one sheet of the LDH separator; and inserting the whole of the negative electrode active material layer and the liquid retaining member with the bent sheet of the LDH separator, and The method according to claim 1, wherein c) includes sealing an overlapping portion belonging to an outer edge of at least one side adjacent to the folded side of the second laminate.
The method according to claim 3, wherein the folding in step (b) is performed such that the folded cross section of the LDH separator is rounded.
The method according to claim 3, wherein the step (c) is performed to seal an overlapping portion belonging to outer edges of two sides adjacent to the bent side of the second laminate.
The step (b) includes sandwiching the whole of the negative electrode active material layer and the liquid retaining member with two unfolded LDH separators, and the step (c) includes the steps of: The method according to claim 1, further comprising the step of sealing the overlapping portion belonging to the outer edge of at least two adjacent sides.
The method according to claim 6, wherein step (c) seals the overlapping portion belonging to the outer edge of the three sides of the second laminate.
The method according to any one of claims 1 to 7, wherein the sealing is performed by at least one selected from the group consisting of an adhesive, heat welding, ultrasonic welding, an adhesive tape and a sealing tape.
The step (b) is performed so as to sandwich the outer peripheral portion of the liquid retaining member between the LDH separators constituting the overlapping portion, and the sealing in the step (c) is performed by heat welding or ultrasonic welding. A method according to any one of the preceding claims, which is performed by
The LDH separator blocks the pores of the porous substrate such that the LDH separator includes the LDH and the porous substrate, and the LDH separator exhibits hydroxide ion conductivity and gas impermeability. The method according to any one of 1 to 9.
11. The method of claim 10, wherein the porous substrate is made of a polymeric material.
The method according to claim 11, wherein the LDH is incorporated throughout the thickness direction of the porous substrate.
The negative electrode active material layer has a current collector, and the current collector has a current collector extension part extending from one side of the negative electrode active material layer,
Step (a) is performed so as not to cover or wrap the tip portion of the current collector extension portion with the liquid retaining member, and step (b) includes the tip portion of the current collector extension portion 13. The method according to any one of claims 1 to 12, wherein the end portion of the current collector extension portion forms an exposed portion not covered by the liquid retaining member and the LDH separator. Or the method described in one item.
The method according to claim 13, wherein the side on which the sealing is performed is a side that does not overlap with the current collector extension.