JP6993246B2 - Zinc secondary battery - Google Patents

Description

The present invention relates to a zinc secondary battery.

In zinc secondary batteries such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc precipitates in the form of dendrite from the negative electrode during charging and reaches the positive electrode through the voids of the separator such as non-woven fabric. It is known to cause short circuits. Such a short circuit caused by zinc dendrite shortens the repeated charge / discharge life.

To address the above problems, a battery provided with a layered double hydroxide (LDH) separator that selectively permeates hydroxide ions and blocks the penetration of zinc dendrites has been proposed. For example, Patent Document 1 (International Publication No. 2013/118561) discloses that an LDH separator is provided between a positive electrode and a negative electrode in a nickel-zinc secondary battery. Further, Patent Document 2 (International Publication No. 2016/076047) discloses a separator structure including an LDH separator fitted or bonded to a resin outer frame, and the LDH separator is gas impermeable and has a gas impermeable property. / Or it is disclosed that it has a high degree of density enough to have water impermeableness. The document also discloses that LDH separators can be composited with porous substrates. Further, Patent Document 3 (International Publication No. 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 substance that can give a starting point for LDH crystal growth is uniformly adhered to the porous substrate, and the porous substrate is subjected to hydrothermal treatment in an aqueous solution of the raw material to form an LDH dense film on the surface of the porous substrate. It includes a step of forming the above.

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 by using the LDH separator as described above, a short circuit or the like due to zinc dendrite can be prevented. Then, in order to maximize this effect, it is desired to surely isolate the positive electrode and the negative electrode with an LDH separator. In particular, it is extremely convenient if a laminated 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 ensuring such a configuration. However, in the conventional zinc secondary battery, the positive electrode and the negative electrode are separated by the LDH separator, and the LDH separator and the battery container are cleverly and carefully sealed and joined by using a resin frame or an adhesive so as to ensure liquidtightness. This was done by doing so, and the battery configuration and manufacturing process tended to be complicated. Such complexity of the battery configuration and the manufacturing process can be particularly remarkable when constructing a laminated battery. This is because it is necessary to perform sealing bonding for ensuring liquidtightness for each of the plurality of cells constituting the laminated battery.

The present inventors have recently made a long LDH separator into a zigzag structure, and by alternately accommodating a positive electrode plate and a negative electrode plate in a plurality of compartments formed by the folded structure, the LDH separator and the battery container can be obtained. It was found that it is possible to provide a laminated battery of a zinc secondary battery that can prevent the spread of zinc dendrites in a simple configuration that can be efficiently assembled in a shortened working time without the need for complicated sealing and joining. ..

Therefore, an object of the present invention is to provide a laminated battery of a zinc secondary battery capable of preventing zinc dendrite extension in a simple configuration that can be efficiently assembled with a shortened working time.

According to one aspect of the invention
With multiple positive electrode plates,
A plurality of negative electrode plates comprising a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloys and zinc compounds.
Elongated, including a porous substrate made of a polymer material and a layered double hydroxide (LDH) that closes the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeableness. LDH separator and
With the electrolyte
The long LDH separator has a zigzag structure, and the positive electrode plate and the negative electrode plate are alternately housed in a plurality of compartments formed by the zigzag structure, whereby the LDH separator is interposed therein. A zinc secondary battery is provided in which the positive electrode plate and the negative electrode plate are separated from each other.

It is a perspective view which shows an example of the internal structure of the zinc secondary battery of this invention. It is an exploded perspective view for demonstrating the zigzag structure of the zinc secondary battery shown in FIG. 1. FIG. 3 is a schematic cross-sectional view conceptually showing the layer structure of the zinc secondary battery shown in FIG. 1. The appearance and internal structure of the zinc secondary battery shown in FIG. 1 are shown. It is a perspective view which shows an example of the negative electrode plate which the negative electrode active material layer is covered with LDH separator used in the zinc secondary battery of this invention. It is a schematic cross-sectional view which shows the layer structure of the negative electrode plate shown in FIG. 5A. It is a schematic diagram for demonstrating the region covered with LDH separator in the negative electrode plate shown in FIG. 5A. It is a schematic cross-sectional view which shows the electrochemical measurement system used in Example 1. FIG. It is an exploded perspective view of the closed container for measurement used in the precision determination test of Example 1. FIG. It is a schematic cross-sectional view of the measurement system used in the precision determination test of Example 1. FIG. It is a conceptual diagram which shows an example of the He permeability measurement system used in Example 1. FIG. 9 is a schematic cross-sectional view of a sample holder used in the measurement system shown in FIG. 9A and its peripheral configuration. 6 is an SEM image showing a cross-sectional microstructure of the LDH separator produced in Example 1.

Zinc secondary battery The zinc secondary battery of the present invention is not particularly limited as long as it is a secondary battery using zinc as a negative electrode and using an alkaline electrolytic solution (typically, an alkaline metal hydroxide aqueous solution). Therefore, it can be a nickel-zinc secondary battery, a silver-zinc oxide secondary battery, a manganese zinc oxide secondary battery, an air-zinc secondary battery, and various other alkaline zinc secondary batteries. For example, it is preferable that the positive electrode contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery forms a nickel-zinc secondary battery. Alternatively, the positive electrode may be an air electrode, whereby the zinc secondary battery may be an air zinc secondary battery.

FIGS. 1 to 4 show an example of the zinc secondary battery of the present invention. The zinc secondary batteries 10 shown in FIGS. 1 to 4 include a battery element 11, wherein the battery element 11 includes a plurality of positive electrode plates 12, a plurality of negative electrode plates 16, and a layered double hydroxide (LDH) separator 22. And an electrolytic solution (not shown). The negative electrode plate 16 includes a negative electrode active material layer 17 containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloys and zinc compounds. The LDH separator 22 includes a porous substrate made of a polymer material and a layered double hydroxide (LDH) that closes the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeableness. In the present specification, the "LDH separator" is defined as a separator containing LDH, which selectively passes hydroxide ions by utilizing the hydroxide ion conductivity of LDH. The LDH separator 22 has a long shape (typically a rectangular shape), and the long separator 22 has a zigzag structure. In the present specification, the "spin-fold structure" (may be referred to as a zigzag-fold shape) means a laminated structure or its shape formed by a plurality of zigzag-shaped objects (here, LDH separator 22) folded back in a zigzag shape. It shall be. The positive electrode plate 12 and the negative electrode plate 16 are alternately housed in the plurality of compartments formed by the zigzag structure, whereby the positive electrode plate 12 and the negative electrode plate 16 are separated from each other via the LDH separator 22. In this way, the LDH separator 22 and the battery container are formed by forming the long LDH separator 22 into a zigzag structure and alternately accommodating the positive electrode plate 12 and the negative electrode plate 16 in a plurality of compartments formed therein. It is possible to provide a laminated battery of a zinc secondary battery capable of preventing the extension of zinc dendrites in a simple configuration that can be efficiently assembled in a shortened working time without the need for complicated sealing and joining.

That is, as described above, the separation of the positive electrode and the negative electrode by the LDH separator in the conventional zinc secondary battery is skillfully and carefully performed by using a resin frame, an adhesive or the like so as to secure the liquidtightness between the LDH separator and the battery container. This is done by sealing and joining to the battery, which tends to complicate the battery configuration and manufacturing process. Such complexity of the battery configuration and the manufacturing process can be particularly remarkable when constructing a laminated battery. In this respect, the LDH separator 22 containing a porous substrate made of a polymer material, which is adopted in the zinc secondary battery 10 of the present invention, has an advantage that it is easy to bend because it has flexibility. Therefore, as shown in FIG. 2, by forming the LDH separator 22 in a long shape and bending it in a zigzag shape, it is possible to easily form a state in which one side of the outer edge is closed. The positive electrode plate 12 and the negative electrode plate 16 are alternately housed in a plurality of compartments formed by the zigzag structure of the LDH separator 22, so that the negative electrode compartment partitioned by the LDH separator 22 is short-circuited by zinc dendrite or the like. Can be provided with a function that can prevent. Therefore, by simply inserting the positive electrode plate 12 and the negative electrode plate 16 into a predetermined section formed by the zigzag structure, the positive electrode plate 12 and the negative electrode plate 16 are separated by the LDH separator, and the stacking with a plurality of cells is provided. Batteries can be made. This is a so-called assembled battery or laminated battery configuration, which is advantageous in that a high voltage and a large current can be obtained. It is also extremely advantageous in that it can improve the efficiency of careful sealing and joining. Further, since the complicated process of wrapping the negative electrode plates 16 one by one with the LDH separator is not required, the working time can be shortened. Further, since the winding of one outer edge (the overlapping portion of the LDH separator 22 ends) of the zigzag-shaped LDH separator 22 can be collectively performed by an efficient sealing method such as heat welding or ultrasonic welding, the work can be performed. The time can be further reduced. Moreover, since the long LDH separator 22 can be used without the need to cut it to the size of one negative electrode plate, the separator cutting step can be streamlined or omitted. Therefore, it is possible to provide a laminated battery of a zinc secondary battery capable of preventing the extension of zinc dendrite in a simple configuration that can be efficiently assembled with a shortened working time.

Typically, as shown in FIG. 1, at least one side C of the end of the LDH separator 22 is sealed, and this at least one side C includes a side connecting to the crease F of the zigzag structure. By doing so, the negative electrode active material layer 17 can be reliably isolated from the positive electrode plate 12, and the extension of zinc dendrite can be prevented more effectively. In this case, the sealed at least one side C and the zigzag crease F separate the compartments accommodating the negative electrode plate 16, and / or the sealed at least one side C and the zigzag crease F are the positive electrodes. It is preferable to separate the compartments for accommodating the plates 12. Particularly preferably, the sealed at least one side C and the zigzag crease F separate both the compartment accommodating the negative electrode plate 16 and the compartment accommodating the positive electrode plate 12 and seal at least one side C. The overlapping portion of the end of the LDH separator 22 having a zigzag structure is integrally sealed. By doing so, since one side of the LDH separator 22 can be sealed at one time, the working time can be significantly shortened, and the sealing work can be further improved in efficiency. It is desirable that the crease F of the LDH separator 22 is bent into a curved surface as shown in FIG. 1 from the viewpoint of maintaining the performance of the LDH separator 22, but as long as the performance of the LDH separator 22 is not impaired, it is desirable. It may have a shape bent into an acute angle or a rectangular shape.

According to a preferred embodiment of the present invention, the battery element 11 is provided so that the positive electrode plate 12, the negative electrode plate 16, and the LDH separator 22 are oriented vertically, and the sealed side C of the LDH separator 22 is at the lower end. As a result, the positive electrode collector extending portion 14a and the negative electrode current collector extending portion 18a extend laterally from the opposite side ends of the battery element 11. By doing so, it becomes easier to collect current, and when one side of the upper end of the outer edge of the LDH separator 22 is opened (this will be described later), there are no obstacles in the upper opening portion, so that the positive electrode plate 12 and the positive electrode plate 12 are used. The inflow and outflow of gas to and from the negative electrode plate 16 becomes easier.

By the way, one or two sides of the outer edge of the zigzag LDH separator 22 may be open. For example, even if one upper end side of the outer edge of the LDH separator 22 is left open, if the liquid is injected so that the electrolytic solution does not reach the upper end one side at the time of manufacturing the zinc secondary battery, electrolysis is performed on the upper end one side. Since there is no liquid, problems of liquid leakage and zinc dendrite extension can be avoided. In this connection, the battery element 11 is housed together with the positive electrode plate 12 in a case 28 which can be a closed container, and is optionally closed with a lid 26 to function as a main component of the closed zinc secondary battery. sell. Therefore, since it is sufficient to secure the airtightness in the case 28 which will be finally accommodated, the battery element 11 itself can have a simple structure with an open top. Further, by opening one side of the outer edge of the LDH separator 22, the negative electrode current collector extending portion 18a can be extended from there.

It is preferable that the outer edge of one side, which is the upper end of the LDH separator 22, is open. This open-top configuration makes it possible to deal with the problem of overcharging in nickel-zinc batteries and the like. That is, when overcharged in a nickel-zinc battery or the like, oxygen (O ₂ ) may be generated in the positive electrode plate 12, but the LDH separator 22 has a high degree of density such that only hydroxide ions can substantially pass through. , O ₂ is not passed. In this respect, according to the upper open type configuration, in the case 28, O ₂ can be released above the positive electrode plate 12 and sent to the negative electrode plate 16 side through the upper open portion, whereby O ₂ can be used. Zn of the negative electrode active material layer 17 can be oxidized and returned to ZnO. By going through such an oxygen reaction cycle, the overcharge resistance can be improved by using the upper open type battery element 11 in the closed type zinc secondary battery. Even when the outer edge of one side, which is the upper end of the LDH separator 22, is closed, the same effect as the above-mentioned open type configuration can be expected by providing a ventilation hole in a part of the closed outer edge. .. For example, a vent may be opened after sealing the outer edge of one side which is the upper end of the LDH separator 22, or a part of the outer edge may be unsealed so that the vent may be formed at the time of sealing. May be good.

At least one side C of the LDH separator 22 may be sealed by any method. Preferred examples of the sealing method include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. Heat welding and ultrasonic welding may be performed using a commercially available heat sealer or the like, but in the case of sealing between LDH separators 22, the outer peripheral portion of the liquid retaining member 20 is sandwiched between the LDH separators 22 constituting the outer peripheral portion. It is preferable to perform heat welding and ultrasonic welding in this way because more effective sealing can be performed. On the other hand, as the adhesive, the adhesive tape and the sealing tape, commercially available products may be used, but those containing an alkali-resistant resin are preferable in order to prevent deterioration in the alkaline electrolytic solution. 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, and among them, epoxy resin adhesives are resistant. It is more preferable because it is particularly excellent in alkalinity. Examples of product examples of the epoxy resin adhesive include the epoxy adhesive Hysol (registered trademark) (manufactured by Henkel).

The positive electrode plate 12 includes a positive electrode active material layer 13. The positive electrode active material layer 13 may be appropriately selected from a known positive electrode material according to the type of the zinc secondary battery, and is not particularly limited. For example, in the case of a nickel-zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. Alternatively, in the case of a zinc-air secondary battery, the air electrode may be used as the positive electrode. It is preferable that the positive electrode plate 12 further includes a positive electrode current collector (not shown). Further, it is preferable that the positive electrode current collector has a positive electrode current collector extending portion 14a extending from a section accommodating the positive electrode plate 12. It is particularly preferable that the positive electrode current collector extending portion 14a extends in a direction away from the crease F of the zigzag structure in the section in which the positive electrode plate 12 is accommodated. By doing so, the positive electrode current collector extending portion 14a and the negative electrode current collector extending portion 18a can be extended in opposite directions, and careless contact between the positive electrode current collector and the negative electrode current collector 18 can be achieved. It is possible to realize a structure that can be reliably avoided and that is extremely easy to collect current. Preferred examples of the positive electrode current collector include a nickel porous substrate such as a foamed nickel plate. In this case, for example, a positive electrode plate made 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 on a porous nickel substrate and drying the paste. .. At that time, it is also preferable to press the positive electrode plate (that is, the positive electrode / positive electrode current collector) after drying to prevent the electrode active material from falling off and to improve the electrode density. The positive electrode plate 12 shown in FIG. 2 contains a positive electrode current collector (for example, nickel foam), but is not shown. This is because the positive electrode current collector is completely integrated with the positive electrode active material layer 13, so that the positive electrode current collector cannot be individually visualized. The zinc secondary battery 10 is preferably further provided with a positive electrode current collector plate 14b connected to the tip of the positive electrode current collector extending portion 14a, and more preferably a plurality of positive electrode current collector extending portions 14a are one positive electrode. It is connected to the current collector plate 14b. By doing so, it is possible to collect current efficiently in a space-efficient manner with a simple configuration, and it becomes easy to connect to the positive electrode terminal 14c. For example, a plurality of positive electrode current collector extending portions 14a can be bundled and connected to one positive electrode current collector plate 14b or positive electrode terminal 14c. Further, the positive electrode current collector plate 14b itself may be used as the positive electrode terminal.

The negative electrode plate 16 includes a negative electrode active material layer 17. The negative electrode active material layer 17 contains at least one selected from the group consisting of zinc, zinc oxide, zinc alloys and zinc compounds. That is, zinc may be contained in any form of zinc metal, zinc compound and zinc alloy as long as it has an electrochemical activity suitable for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate and the like, but a mixture of zinc metal and zinc oxide is more preferable. The negative electrode active material layer 17 may be formed in the form of a gel, 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, polyacrylic acid salt, CMC, alginic acid and the like, but polyacrylic acid is preferable because it has excellent chemical resistance to strong alkalis.

As the zinc alloy, a mercury- and lead-free zinc alloy known as a non-mercury zinc alloy can be used. For example, a zinc alloy containing 0.01 to 0.06% by mass of indium, 0.005 to 0.02% by mass of bismuth, and 0.0035 to 0.015% by mass of aluminum has an effect of suppressing hydrogen gas generation. Therefore, it is preferable. In particular, indium and bismuth are advantageous in improving discharge performance. When the zinc alloy is used for the negative electrode, the self-dissolution rate in the alkaline electrolytic solution is slowed down, so that the generation of hydrogen gas can be suppressed and the safety can be improved.

The shape of the negative electrode material is not particularly limited, but it is preferably in the form of powder, which increases the surface area and makes it possible to cope with a large current discharge. In the case of a zinc alloy, the average particle size of the preferred negative electrode material is in the range of 90 to 210 μm, and if it is within this range, the surface area is large, so that it is suitable for dealing with a large current discharge, and also with an electrolytic solution and a gelling agent. It is easy to mix evenly and is easy to handle when assembling the battery.

It is preferable that the negative electrode plate 16 further includes a negative electrode current collector 18. Further, the negative electrode current collector 18 has a negative electrode current collector extending portion 18a extending from a section accommodating the negative electrode plate 16. It is particularly preferable that the negative electrode current collector extending portion 18a extends in a direction away from the crease F of the zigzag structure in the section in which the negative electrode plate 16 is accommodated. By doing so, the positive electrode current collector extending portion 14a and the negative electrode current collector extending portion 18a can be extended in opposite directions, and careless contact between the positive electrode current collector and the negative electrode current collector 18 can be achieved. It is possible to realize a structure that can be reliably avoided and that is extremely easy to collect current. The zinc secondary battery 10 preferably further includes a negative electrode current collector plate 18b connected to the tip of the negative electrode current collector extending portion 18a, and more preferably a plurality of negative electrode current collector extending portions 18a are one negative electrode. It is connected to the current collector plate 18b. By doing so, it is possible to collect current efficiently in a space-efficient manner with a simple configuration, and it becomes easy to connect to the negative electrode terminal 18c. For example, a plurality of negative electrode current collector extending portions 18a can be bundled and connected to one negative electrode current collector plate 18b or negative electrode terminal 18c. Further, the negative electrode current collector plate 18b itself may be used as the negative electrode terminal. Typically, the tip portion of the negative electrode current collector extending portion 18a forms an exposed portion that is not covered by the LDH separator 22 and the liquid retaining member 20 (if any). As a result, the negative electrode current collector 18 (particularly the negative electrode current collector extending portion 18a) can be preferably connected to the negative electrode current collector plate 18b and / or the negative electrode terminal 18c via the exposed portion. In this case, as shown in FIG. 6, a predetermined margin M (for example, an interval of 1 to 5 mm) is set so that the LDH separator 22 sufficiently hides the end portion of the negative electrode active material layer 17 on the negative electrode current collector extending portion 18a side. ) Is preferably covered or wrapped. By doing so, it is possible to more effectively prevent the spread of zinc dendrite from the end portion of the negative electrode active material layer 17 on the extending portion 18a side of the negative electrode current collector or the vicinity thereof.

Preferred examples of the negative electrode current collector 18 include a copper foil, a copper expanded metal, and a copper punching metal, and a copper expanded metal is more preferable. In this case, for example, a mixture containing zinc oxide powder and / or zinc powder and, if desired, a binder (for example, polytetrafluoroethylene particles) is applied onto the copper expanded metal, and the negative electrode is composed of a negative electrode / negative electrode current collector. The plate can be preferably manufactured. At that time, it is also preferable to press the negative electrode plate (that is, the negative electrode / negative electrode current collector) after drying to prevent the electrode active material from falling off and to improve the electrode density.

Preferably, the negative electrode plate 16 is covered with the liquid-retaining member 20, and the liquid-retaining member 20 is impregnated with the electrolytic solution. By doing so, the electrolytic solution can be evenly present between the negative electrode active material layer 17 and the LDH separator 22, and hydroxide ions can be exchanged between the negative electrode active material layer 17 and the LDH separator 22. It can be done efficiently. The liquid-retaining member 20 is not particularly limited as long as it is a member capable of holding the electrolytic solution, but is preferably a sheet-shaped member. Preferred examples of the liquid-retaining member include a non-woven fabric, a water-absorbent resin, a liquid-retaining resin, a porous sheet, and various spacers, but a non-woven fabric is particularly preferable in that a negative electrode structure having good performance can be produced at low cost. .. The liquid-retaining member 20 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, and particularly preferably 0.02 to 0.15 mm. 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 retaining member 20 while keeping the overall size of the negative electrode structure compact without waste.

The entire negative electrode active material layer 17 is covered or wrapped with the LDH separator 22. 5A and 5B show a preferred embodiment of the negative electrode plate 16 in which the negative electrode active material layer 17 is covered or wrapped with the LDH separator 22. The negative electrode structure shown in FIGS. 5A and 5B includes a negative electrode active material layer 17, a negative electrode current collector 18, and a liquid retaining member 20 if desired, and the entire negative electrode active material layer 17 is retained (if necessary). Covered or wrapped with LDH separator 22 (via liquid member 20). In this way, by covering or wrapping the entire negative electrode active material layer 17 with the LDH separator 22 (via the liquid retaining member 20 as necessary), as described above, the LDH separator 22 and the battery container are complicated. It is possible to manufacture a laminated battery of a zinc secondary battery capable of preventing the spread of zinc dendrites extremely easily and with high productivity by eliminating the need for sealing and joining.

In FIGS. 5A and 5B, the liquid-retaining member 20 is drawn as having a size smaller than that of the zigzag-shaped LDH separator 22, but the liquid-retaining member 20 may have the same size as the zigzag-shaped LDH separator 22. The outer edge of 20 can reach the outer edge of the LDH separator 22. That is, the outer peripheral portion of the liquid retaining member 20 may be sandwiched between the LDH separators 22 constituting the outer peripheral portion. By doing so, the outer edge sealing of the LDH separator 22, which will be described later, can be effectively performed by heat welding or ultrasonic welding. That is, rather than directly heat-welding or ultrasonic welding the LDH separators 22 to each other, the LDH separators 22 are indirectly heat-welded or ultrasonically welded by interposing a heat-welding liquid-retaining member 20 between them. As a result of being able to utilize the heat welding property of the liquid retaining member 20 itself, more effective sealing can be performed. For example, the end portion of the liquid retaining member 20 to be sealed can be used as if it were a hot melt adhesive. Preferred examples of the liquid-retaining member 20 in this case include a non-woven fabric, particularly a non-woven fabric made of a thermoplastic resin (for example, polyethylene or polypropylene).

The LDH separator 22 contains LDH and a porous substrate. As mentioned above, the LDH is a pore in the porous substrate so that the LDH separator 22 exhibits hydroxide ion conductivity and gas impermeability (hence to function as an LDH separator exhibiting hydroxide ion conductivity). Is blocking. The porous substrate is made of a polymer material, and LDH is particularly preferably incorporated over the entire thickness direction of the porous substrate made of a polymer material. Various preferred embodiments of the LDH separator 22 will be described in detail later.

The number of LDH separators 22 is typically 1, but may be 2 or more. For example, a plurality of LDH separators 22 may be bent in a zigzag shape to accommodate the positive electrode plate 12 and the negative electrode plate 16 in a predetermined section.

The electrolytic solution preferably contains an aqueous alkali metal hydroxide solution. Although the electrolytic solution is not shown, this is because it is spread over the entire positive electrode plate 12 (particularly the positive electrode active material layer 13) and the negative electrode plate 16 (particularly the negative electrode active material layer 17). Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide and the like, but potassium hydroxide is more preferable. Zinc compounds such as zinc oxide and zinc hydroxide may be added to the electrolytic solution in order to suppress the self-dissolution of zinc and / or zinc oxide. As described above, the electrolytic solution may be mixed with the positive electrode active material and / or the negative electrode active material and exist in the form of a positive electrode mixture and / or a negative electrode mixture. Further, the electrolytic solution may be gelled in order to prevent leakage of the electrolytic solution. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells, and polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, and starch are used.

As shown in FIG. 4, the zinc secondary battery 10 may further include a case 28 accommodating a plurality of battery elements 11. The case 28 accommodating the battery element 11 is preferably made of resin. The resin constituting the case 28 is preferably a resin having resistance to an alkali metal hydroxide such as potassium hydroxide, more preferably a polyolefin resin, an ABS resin, or a modified polyphenylene ether, and further preferably an ABS resin or. It is a modified polyphenylene ether. Further, a case group in which two or more cases 28 are arranged may be housed in an outer frame to form a battery module.

LDH Separator The LDH separator 22 is a separator containing a layered double hydroxide (LDH), and when incorporated in a zinc secondary battery, separates a positive electrode plate and a negative electrode plate so that hydroxide ions can be conducted. .. That is, the LDH separator 22 functions as a hydroxide ion conduction separator. The preferred LDH separator 22 has gas impermeable and / or water impermeable. In other words, the LDH separator 22 is preferably densified to have gas impermeableness and / or water impermeableness. As described in Patent Documents 2 and 3, "having gas impermeable" in the present specification means that helium gas is brought into contact with one side of an object to be measured in water with a differential pressure of 0.5 atm. However, it means that no bubbles are generated due to helium gas from the other side. Further, in the present specification, "having water impermeable" 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 22 has gas impermeableness and / or water impermeability means that the LDH separator 22 has a high degree of porosity to the extent that gas or water does not pass through, and is water permeable or gas. It means that it is not a permeable porous film or other porous material. By doing so, the LDH separator 22 selectively passes only hydroxide ions due to its hydroxide ion conductivity, and can exhibit a function as a battery separator. Therefore, the configuration is extremely effective in physically preventing the penetration of the separator by the zinc dendrite generated during charging to prevent a short circuit between the positive and negative electrodes. Since the LDH separator 22 has hydroxide ion conductivity, it is possible to efficiently move the required hydroxide ion between the positive electrode plate and the negative electrode plate, and to realize the charge / discharge reaction in the positive electrode plate and the negative electrode plate. Can be done.

The LDH separator 22 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 further 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 ion or zinc acid ion) in the electrolytic solution. As described above, it is considered in principle that the separator of this embodiment can effectively suppress the growth of zinc dendrite when used in a zinc secondary battery by significantly suppressing Zn permeation. The He permeability is determined through a step of supplying He gas to one surface of the separator and allowing the He gas to permeate through the separator, and a step of calculating the He permeability and evaluating the denseness of the hydroxide ion conduction separator. Be measured. The He permeability is determined by the formula of F / (P × S) using the permeation amount F of the He gas per unit time, the differential pressure P applied to the separator when the He gas permeates, and the membrane area S through which the He gas permeates. calculate. By evaluating the gas permeability using He gas in this way, it is possible to evaluate the presence or absence of denseness at an extremely high level, and as a result, substances other than hydroxide ions (particularly zinc dendrite growth) can be evaluated. It is possible to effectively evaluate a high degree of fineness such that the causing Zn) is not permeated as much as possible (only a very small amount is permeated). This is because He gas has the smallest structural unit among the various atoms or molecules that can compose the gas, and its reactivity is extremely low. That is, He constitutes He gas by a single He atom without forming a molecule. In this respect, since hydrogen gas is composed of H ₂ molecules, the single He atom is smaller as a gas constituent unit. In the first place, H ₂ gas is dangerous because it is a flammable gas. Then, by adopting the index of He gas permeability defined by the above formula, it is possible to easily perform an objective evaluation of the fineness regardless of the difference in various sample sizes and measurement conditions. In this way, it is possible to easily, safely and effectively evaluate whether or not the separator has sufficiently high density suitable for a separator for a zinc secondary battery. The measurement of He permeability can be preferably performed according to the procedure shown in Evaluation 7 of Example 1 described later.

As is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. The middle layer of LDH is composed of anions and _H2O . The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in ^LDH contain OH ^- and / or CO _3-2- . LDH also has excellent ionic conductivity due to its unique properties.

In general, LDH is M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _{x / n} · mH ₂ O (in the formula, M ²⁺ is a divalent cation and M ³⁺ is a trivalent cation. It is a cation, ^An- 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 a representative. In the above basic composition formula, M ²⁺ can be any divalent cation, but preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ can be any trivalent cation, with preferred examples being Al ³⁺ or Cr ³⁺ , more preferably Al ³⁺ . An _- can be any anion, but preferred examples include ^{OH- and} CO ^32- . Therefore, in the above basic composition formula, it is preferable that M ²⁺ contains ^{Mg 2+} , M ³⁺ contains Al ³⁺ , and An − contains OH ⁻ and / or CO ₃ ^2- . n is an integer of 1 or more, but is preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. m is any number that means the number of moles of water and is a real number greater than or equal to 0, typically greater than or equal to 0 or greater than or equal to 1. However, the above-mentioned basic composition formula is merely a formula of the "basic composition" generally exemplified with respect to LDH, and the constituent ions can be appropriately replaced. For example, in the above basic composition formula, a part or all of M ³⁺ may be replaced with a cation having a valence of 4 or more, and in that case, the coefficient x / ⁿ of the anion An − in the above general formula may be replaced. May be changed as appropriate.

For example, the hydroxide basic layer of LDH may be composed of Ni, Ti, OH groups and optionally unavoidable impurities. The intermediate layer of LDH is composed of anions and _H2O as described above. The alternating laminated structure of the hydroxide basic layer and the intermediate layer itself is basically the same as the generally known LDH alternating laminated structure, but the LDH of this embodiment mainly contains the hydroxide basic layer of LDH as Ni. By being composed of Ti and OH groups, excellent alkali resistance can be exhibited. The reason is not necessarily clear, but it is considered that LDH of this embodiment does not intentionally or positively add an element (for example, Al) that is considered to be easily eluted in an alkaline solution. Nevertheless, LDH of this embodiment can also exhibit high ionic conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can take the form of nickel ions. Nickel ions in LDH are typically considered to be Ni ²⁺ , but are not particularly limited as other valences such as Ni ³⁺ are possible. Ti in LDH can take the form of titanium ions. Titanium ions in LDH are typically considered to be Ti ⁴⁺ , but are not particularly limited as other valences such as Ti ³⁺ are possible. The unavoidable impurity is an arbitrary element that can be unavoidably mixed in the production method, and can be mixed in LDH, for example, derived from a raw material or a base material. As mentioned above, since the valences of Ni and Ti are not always fixed, it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the basic hydroxide layer is mainly composed of Ni ²⁺ , Ti ⁴⁺ and OH groups, the corresponding LDH can be expressed as the general formula: Ni ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ^An . ⁻ _{2x / n} · mH ₂ O (in the formula, An − 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, m is a real number greater than or equal to 0, typically greater than or equal to 0 or greater than or equal to 1). However, the above general formula should be understood as "basic composition" to the extent that elements such as Ni ²⁺ and Ti ⁴⁺ do not impair the basic characteristics of LDH, and other elements or ions (other values of the same element). It should be understood as replaceable with a number of elements or ions or elements or ions that are unavoidably mixed in the process.

Alternatively, the hydroxide basic layer of LDH may contain Ni, Al, Ti and OH groups. The intermediate layer is composed of anions and _H2O as described above. The alternating laminated structure of the hydroxide basic layer and the intermediate layer itself is basically the same as the generally known LDH alternating laminated structure, but in the LDH of this embodiment, the hydroxide basic layer of LDH is made of Ni, Al. By being composed of a predetermined element or ion containing Ti and OH groups, excellent alkali resistance can be exhibited. The reason is not necessarily clear, but LDH in this embodiment is thought to be because Al, which was conventionally thought to be easily eluted in an alkaline solution, becomes difficult to elute in an alkaline solution due to some interaction with Ni and Ti. Be done. Nevertheless, LDH of this embodiment can also exhibit high ionic conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can take the form of nickel ions. Nickel ions in LDH are typically considered to be Ni ²⁺ , but are not particularly limited as other valences such as Ni ³⁺ are possible. Al in LDH can take the form of aluminum ions. Aluminum ions in LDH are typically considered to be Al ³⁺ , but are not particularly limited as other valences are possible. Ti in LDH can take the form of titanium ions. Titanium ions in LDH are typically considered to be Ti ⁴⁺ , but are not particularly limited as other valences such as Ti ³⁺ are possible. The hydroxide basic layer may contain other elements or ions as long as it contains Ni, Al, Ti and OH groups. However, the hydroxide basic layer preferably contains Ni, Al, Ti and OH groups as main components. That is, it is preferable that the hydroxide basic layer is mainly composed of Ni, Al, Ti and OH groups. Therefore, the hydroxide basic layer is typically composed of Ni, Al, Ti, OH groups and, in some cases, unavoidable impurities. The unavoidable impurity is an arbitrary element that can be unavoidably mixed in the production method, and can be mixed in LDH, for example, derived from a raw material or a base material. As mentioned above, since the valences of Ni, Al and Ti are not always fixed, it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the basic hydroxide layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ and OH groups, the corresponding LDH can be expressed as the general formula: Ni ²⁺ _1-xy Al ³⁺ _x Ti. ^{4 +} _y (OH) ₂ A ^n- _{(x + 2y) / n} · mH ₂ O (In the formula, An- 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, 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 (which is a real number greater than or equal to 1). However, the above general formula should be understood as "basic composition" to the extent that elements such as Ni ²⁺ , Al ³⁺ , and Ti ⁴⁺ do not impair the basic characteristics of LDH, and other elements or ions (of the same element). It should be understood as replaceable with elements or ions of other valences or elements or ions that can be unavoidably mixed in the process.

It goes without saying that the porous substrate has water permeability and gas permeability, and therefore, when incorporated into a zinc secondary battery, the electrolytic solution can reach LDH, but the porous substrate is This makes it possible for the LDH separator 22 to stably retain hydroxide ions. Further, since the strength can be imparted by the porous substrate, the LDH separator 22 can be thinned to reduce the resistance.

As mentioned above, the LDH separator 22 contains LDH and a porous substrate (typically composed of them) so that the LDH separator 22 exhibits hydroxide ion conductivity and gas impermeable (hence). LDH closes the pores of the porous substrate (so that it functions as an LDH separator exhibiting hydroxide ion conductivity). It is particularly preferable that LDH is incorporated over the entire thickness direction of the porous substrate made of a polymer material. The thickness of the LDH separator 22 is preferably 5 to 200 μm, more preferably 5 to 100 μm, and even more preferably 5 to 30 μm.

The porous substrate is preferably made of a polymer material. The polymer porous substrate has 1) flexibility (hence, it is hard to break even if it is thin), 2) easy to increase the porosity, and 3) easy to increase the conductivity (thickness while increasing the porosity). It has the advantages of being easy to manufacture and handle) (because it can be made thinner). Further, taking advantage of the flexibility of 1) above, the LDH separator 22 containing a porous substrate made of a polymer material can be easily bent or sealed and bonded, thereby as described above. In addition, there is an advantage that at least one side of the outer edge of the LDH separator 22 can be easily closed (in the case of bending, there is also an advantage that the sealing step of one outer edge can be reduced). Preferred examples of the polymer material are polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrophilized fluororesin (tetrafluororesin: PTFE, etc.), cellulose, nylon, polyethylene and any combination thereof. Can be mentioned. All of the various preferable materials described above have alkali resistance as resistance to the electrolytic solution of the battery. Particularly preferable polymer materials are polyolefins such as polypropylene and polyethylene, and most preferably polypropylene, because they are excellent in heat resistance, acid resistance and alkali resistance, and are low in cost. When the porous substrate is composed of a polymer material, the LDH layer is incorporated over the entire thickness direction of the porous substrate (for example, most or almost all the pores inside the porous substrate are filled with LDH). ) Is particularly preferable. In this case, the thickness of the polymer porous substrate is preferably 5 to 200 μm, more preferably 5 to 100 μm, and even more preferably 5 to 30 μm. As such a polymer porous substrate, a microporous membrane as commercially available as a separator for a lithium battery can be preferably used, or commercially available cellophane can also be used.

The porous substrate preferably has an average pore diameter of 100 μm or less, more preferably 50 μm or less, typically 0.001 to 1.5 μm, and more typically 0.001. It is 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. Within these ranges, it is possible to form an LDH separator that is dense enough to exhibit gas impermeableness while ensuring the desired water permeability and strength as a support for the porous substrate. In the present invention, the average pore diameter can be measured by measuring the longest distance of the 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 obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points are arranged in order from the average value, for a total of 30 points per field of view. The average pore diameter can be obtained by calculating the average value for two fields of view. For the length measurement, the length measurement function of SEM software, image analysis software (for example, Photoshop, manufactured by Adobe) and 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%. Within these ranges, it is possible to form an LDH separator that is dense enough to exhibit gas impermeableness while ensuring the desired water permeability and strength as a support for the porous substrate. The porosity of the porous substrate can be preferably measured by the Archimedes method. However, when the porous substrate is composed of a polymer material and LDH is incorporated over the entire thickness direction of the porous substrate, the porosity of the porous substrate is preferably 30 to 60%, which is more preferable. Is 40-60%.

The method for producing the LDH separator 22 is not particularly limited, and the LDH separator 22 is produced by appropriately changing the conditions of the already known LDH-containing functional layer and the method for producing a composite material (that is, 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 an alumina / titania layer is formed by applying a titanium oxide sol or a mixed sol of alumina and titania to the porous substrate and heat-treating the mixture. (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 heat-treated in the raw material aqueous solution to make the LDH-containing functional layer a porous base material. LDH-containing functional layers and composite materials (ie, LDH separators) can be produced by forming them in 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 for LDH is provided, but also the porous substrate is made to function as a starting point for LDH crystal growth. The LDH-containing functional layer highly densified on the surface can be uniformly and uniformly formed. Further, in the presence of urea in the above step (3), the pH value rises due to the generation of ammonia in the solution by utilizing the hydrolysis of urea, and the coexisting metal ions form a hydroxide. Can obtain LDH. In addition, since hydrolysis is accompanied by the generation of carbon dioxide, LDH in which anions are carbonate ion can be obtained.

In particular, when a composite material (that is, an LDH separator) in which the porous base material is composed of a polymer material and the functional layer is incorporated over the entire thickness direction of the porous base material is produced, the alumina in the above (2) And, it is preferable to apply the mixed sol of titania to the substrate by a method in which the mixed sol permeates the whole or most of the inside of the substrate. By doing so, most or almost all the pores inside the porous substrate can be finally filled with LDH. Examples of the preferred coating method include a dip coat, a filtration coat and the like, and a dip coat is particularly preferable. By adjusting the number of times of application of the dip coat or the like, the amount of the mixed sol adhered can be adjusted. The base material coated with the mixed sol by a dip coat or the like may be dried and then the above steps (3) and (4) may be carried out.

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

Example 1
An LDH separator containing Ni, Al and Ti-containing LDH was prepared and evaluated by the following procedure using a polymer porous substrate.

(1) Preparation of Polymer 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 is adjusted to a size of 2.0 cm × 2.0 cm. Cut out to.

(2) Alumina-titania sol coating on polymer porous substrate Atypical alumina solution (Al-ML15, manufactured by Taki Chemical Co., Ltd.) and titanium oxide sol solution (M6, manufactured by Taki Chemical Co., Ltd.) are mixed with Ti / Al (M6, manufactured by Taki Chemical Co., Ltd.). A mixed sol was prepared by mixing so that the molar ratio) = 2. The mixed sol was applied to the substrate prepared in (1) above by dip coating. Dip coating was performed by immersing the substrate in 100 ml of the mixed sol, pulling it up vertically, and drying it in a dryer at 90 ° C. for 5 minutes.

(3) Preparation of raw material aqueous solution 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)) are prepared as raw materials. Nickel nitrate hexahydrate was weighed to 0.015 mol / L and placed in a beaker, and ion-exchanged water was added thereto to make the total volume 75 ml. After stirring the obtained solution, the solution was added. Urea weighed at a ratio of urea / NO _3- ⁽ molar ratio) = 16 was added thereto, and the mixture was further stirred to obtain an aqueous raw material solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) closed container (autoclave container, content 100 ml, jacket made of stainless steel on the outside) was filled with the raw material aqueous solution and the dip-coated base material. At this time, the base material was floated and fixed from the bottom of a closed container made of Teflon (registered trademark), and placed horizontally so that the solution was in contact with both sides of the base material. Then, LDH was formed on the surface and the inside of the substrate by subjecting it to hydrothermal treatment at a hydrothermal temperature of 120 ° C. for 24 hours. After a lapse of a predetermined time, the substrate was taken out of the closed container, washed with ion-exchanged water, and dried at 70 ° C. for 10 hours to obtain LDH incorporated in the porous substrate. In this way, an LDH separator was obtained.

(5) Evaluation The obtained LDH separators were evaluated in various ways as shown below.

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

Evaluation 2 : Observation of microstructure The surface microstructure of the LDH separator was observed with an acceleration voltage of 10 to 20 kV using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL Ltd.). Further, after obtaining the cross-section polished surface of the LDH separator by an ion milling apparatus (IM4000 manufactured by Hitachi High-Technologies Corporation), the microstructure of the cross-section polished surface was observed by SEM under the same conditions as the observation of the surface microstructure.

Evaluation 3 : Elemental analysis evaluation (EDS)
The LDH separator was polished with a cross-section polisher (CP) so that the cross-section polished surface could be observed. By FE-SEM (ULTRA55, manufactured by Carl Zeiss), a cross-sectional image of an LDH separator was acquired in one field of view at a magnification of 10000 times. Elemental analysis of the LDH film on the surface of the substrate and the LDH portion (point analysis) inside the substrate in this cross-sectional image was performed using an EDS analyzer (NORAN System SIX, manufactured by Thermo Fisher Scientific) under the condition of an acceleration voltage of 15 kV. went.

Evaluation 4 : Evaluation of alkali resistance Zinc oxide was dissolved in a 6 mol / L potassium hydroxide aqueous solution to obtain a 5 mol / L potassium hydroxide aqueous 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 closed container made of Teflon (registered trademark). An LDH separator having a size of 1 cm × 0.6 cm was installed at the bottom of the closed container, and the lid was closed. Then, after holding at 70 ° C. for 3 weeks (ie, 504 hours) or 7 weeks (ie, 1176 hours), the LDH separator was taken out from the closed container. The LDH separator removed 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 between the silicone packings 40 having a thickness of 1 mm from both sides and incorporated into a PTFE flange type cell 42 having an inner diameter of 6 mm. As the electrodes 46, a nickel wire mesh of # 100 mesh was incorporated into the cell 42 in a cylindrical shape having a diameter of 6 mm so that the distance between the electrodes was 2.2 mm. As the electrolytic solution 44, a 6M KOH aqueous solution was filled in the cell 42. Using an electrochemical measurement system (potential / galvanostad-frequency response analyzer, Solartron 1287A and 1255B types), the measurement was performed under the conditions of a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV, and a section of the real number axis. Was taken as the resistance of the LDH separator sample S. The same measurement as above was performed only on the porous substrate without the LDH film, and the resistance of only the porous substrate was determined. The difference between the resistance of the LDH separator sample S and the resistance of the base material alone was taken as the resistance of the LDH film. The conductivity was determined using the resistance of the LDH film and the film thickness and area of the LDH.

Evaluation 6 : Denseness determination test In order to confirm that the LDH separator has a denseness enough to exhibit gas impermeableness, a density determination test was conducted as follows. First, as shown in FIGS. 8A and 8B, an acrylic container 130 without a lid and an alumina jig 132 having a shape and size capable of functioning as a lid of the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying gas. Further, the alumina jig 132 is formed with an opening 132a having a diameter of 5 mm, and a recess 132b for mounting a sample is formed along the outer periphery of the opening 132a. The epoxy adhesive 134 was applied to the recess 132b of the alumina jig 132, and the LDH separator sample 136 was placed in the recess 132b 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 airtightly and liquid-tightly adhered to the upper end of the acrylic container 130 using a silicone adhesive 138 so as to completely close the open portion of the acrylic container 130. A closed container 140 for measurement was obtained. The closed container 140 for measurement 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 the helium gas could be supplied into the acrylic container 130. Water 143 was placed in the water tank 142, and the airtight container 140 for measurement was completely submerged. At this time, the inside of the airtight container 140 for measurement is sufficiently airtight and liquidtight, and one side of the LDH separator sample 136 is exposed to the internal space of the airtight container 140 for measurement, while the LDH separator sample 136. The other side of the water tank 142 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 130a into the airtight container 140 for measurement. The pressure gauge 144 and the flow meter 146 are controlled so that the differential pressure inside and outside 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 or not helium gas bubbles were generated in the water from the LDH separator sample 136. As a result, when the generation of bubbles due to helium gas was not observed, it was determined that the LDH separator sample 136 had high density enough to exhibit gas impermeableness.

Evaluation 7 : He Permeation Measurement A He permeation test was conducted as follows in order to evaluate the denseness of the LDH separator from the viewpoint of He permeability. First, the He permeability measuring system 310 shown in FIGS. 9A and 9B was constructed. In the He permeability measuring system 310, He gas from a gas cylinder filled with He gas is supplied to the sample holder 316 via a pressure gauge 312 and a flow meter 314 (digital flow meter), and the LDH held in the sample holder 316. The separator 318 was configured to be permeated from one surface to the other surface and discharged.

The sample holder 316 has a structure including a gas supply port 316a, a closed space 316b, and a gas discharge port 316c, and was assembled as follows. First, the adhesive 322 was applied along the outer circumference of the LDH separator 318 and attached to a jig 324 (made of ABS resin) having an opening in the center. Packing made of butyl rubber is arranged as sealing members 326a and 326b at the upper and lower ends of the jig 324, and support members 328a and 328b (manufactured by PTFE) having openings made of flanges from the outside of the sealing members 326a and 326b. ). In this way, the sealed space 316b was partitioned by the LDH separator 318, the jig 324, the sealing member 326a, and the support member 328a. The support members 328a and 328b were firmly fastened to each other by the fastening means 330 using screws so that the He gas did not leak from the portion other than the gas discharge port 316c. A gas supply pipe 334 was connected to the gas supply port 316a of the sample holder 316 thus assembled via a joint 332.

Next, He gas was supplied to the He permeability measuring system 310 via the gas supply pipe 334, and was permeated through the LDH separator 318 held in the sample holder 316. At this time, the gas supply pressure and the flow rate were monitored by the pressure gauge 312 and the flow meter 314. After permeating the He gas for 1 to 30 minutes, the He permeation was calculated. The He permeability is calculated by the permeation amount F (cm ³ / min) of the He gas per unit time, the differential pressure P (atm) applied to the LDH separator when the He gas permeates, and the film area S (cm) through which the He gas permeates. It was calculated by the formula of F / (P × S) 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, the gauge pressure read from the pressure gauge 312 was used. The He gas was supplied so 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. 10, it was observed that LDH was incorporated over the entire area of the porous substrate in the thickness direction, that is, the pores of the porous substrate were evenly filled with 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 basic hydroxide layer, while C corresponds to ^{CO 32-2} _, 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 being immersed in a potassium hydroxide aqueous solution at 70 ° C. 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 density so as to exhibit gas impermeableness.
-Evaluation 7: The He permeability of the LDH separator was 0.0 cm / min · atm.

10 Zinc secondary battery 11 Battery element 12 Positive electrode plate 13 Positive electrode active material layer 14a Positive electrode current collector extension 14b Positive electrode collector plate 14c Positive electrode terminal 16 Negative electrode plate 17 Negative electrode active material layer 18 Negative electrode current collector 18a Negative electrode current collector Extension 18b Negative electrode current collector 18c Negative electrode terminal 20 Liquid retention member 22 LDH separator 26 Lid 28 Case F Fold C Sealed side

Claims (9)

With multiple positive electrode plates,
A plurality of negative electrode plates comprising a negative electrode active material layer containing at least one selected from the group consisting of zinc, zinc oxide, zinc alloys and zinc compounds.
Elongated, including a porous substrate made of a polymer material and a layered double hydroxide (LDH) that closes the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeableness. LDH separator and
With the electrolyte
The long LDH separator has a zigzag structure, and the positive electrode plate and the negative electrode plate are alternately housed in a plurality of compartments formed by the zigzag structure, whereby the LDH separator is interposed therein. The positive electrode plate and the negative electrode plate are separated from each other .
An air zinc secondary battery in which the positive electrode plate is an air electrode . The zinc- air secondary battery according to claim 1, wherein the LDH is incorporated over the entire area of the porous substrate in the thickness direction. The zinc- air secondary battery according to claim 1 or 2, wherein the negative electrode plate is covered with a liquid-retaining member, and the liquid-retaining member is impregnated with the electrolytic solution. The zinc- air secondary battery according to claim 3, wherein the liquid-retaining member is a non-woven fabric. The zinc- air battery according to any one of claims 1 to 4, wherein at least one side of the end portion of the LDH separator is sealed, and the at least one side includes a side connected to a crease of the zigzag structure. Next battery. The sealed at least one side and the zigzag creases separate the compartments that house the negative electrode plate, and / or the sealed at least one side and the zigzag creases form the positive electrode plate. The zinc- air secondary battery according to claim 5, which separates the compartments to be accommodated. The sealed at least one side and the crease of the zigzag structure separate both the section accommodating the negative electrode plate and the section accommodating the positive electrode plate, and the sealed at least one side has the zigzag structure. The zinc- air secondary battery according to claim 5 or 6, wherein the overlapping portion of the LDH separator end portion is integrally sealed. The negative electrode plate further includes a negative electrode current collector, the negative electrode current collector has a negative electrode current collector extending portion extending from a section accommodating the negative electrode plate, and the positive electrode plate is a positive electrode current collector. The air -zinc secondary battery according to any one of claims 1 to 7, further comprising: The negative electrode current collector extending portion extends in a direction away from the crease of the zigzag structure in the section in which the negative electrode plate is accommodated, and the positive electrode current collector extending portion accommodates the positive electrode plate. The zinc-air battery according to claim 8, wherein the zinc- air battery extends in a direction away from the fold of the zigzag structure in the section to be formed.

Images