JP2019106351A - Zinc secondary battery - Google Patents

Abstract

To prevent the change in the shape of a negative electrode plate, accompanying the iteration of charge and discharge in a zinc secondary battery which can prevent zinc dendrite extention with LDH separator.SOLUTION: A zinc secondary battery comprises: a positive electrode plate including a positive electrode active material layer and a positive electrode current collector; a negative electrode plate including a negative electrode active material layer containing zinc and a negative electrode current collector; a layered double hydroxide (LDH) separator for isolating the positive and negative electrode plates in such a way that a hydroxyl ion can be conducted; and an electrolyte solution. The negative electrode active material layer has a surplus outer peripheral region, which is not opposed to the positive electrode active material layer, along its outer periphery. The zinc secondary battery has a positive electrode reaction-suppressing structure for suppressing an electrochemical reaction at an end of the positive electrode active material layer, and and/or a negative electrode reaction-suppressing structure for suppressing an electrochemical reaction in the surplus outer peripheral region of the negative electrode active material layer, whereby an electrochemical activity is locally decreased at the end of the positive electrode active material layer and/or in the surplus outer peripheral region of the negative electrode active material layer.SELECTED DRAWING: Figure 1

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, 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

  By forming a zinc secondary battery such as a nickel zinc battery using the above-described LDH separator, a short circuit or the like due to zinc dendrite can be prevented. In particular, by reliably separating the positive electrode and the negative electrode with the LDH separator, the above effects can be exhibited to the maximum. However, it was found that as the charge and discharge were repeated, the shape of the negative electrode changed to an undesirable shape and size. For example, as shown in FIG. 2, the negative electrode active material layer 17 (ZnO layer), which was initially square, shrinks non-uniformly toward the center as charge and discharge are repeated, that is, the negative electrode active material layer 17 (ZnO) The phenomenon that the outer part of the layer is eroded unevenly and lost is observed. Such a change in shape of the negative electrode active material layer 17 leads to a decrease in the effective region of the negative electrode facing the positive electrode plate, resulting in an increase in battery resistance and a decrease in battery capacity.

  The present inventors, in a zinc secondary battery provided with an LDH separator, a positive electrode reaction suppression structure for suppressing an electrochemical reaction at an end of the positive electrode active material layer, and / or a positive electrode active material layer of a negative electrode active material layer. By providing the negative electrode reaction suppression structure which suppresses the electrochemical reaction in the surplus outer periphery area which does not oppose, it acquired the knowledge that the shape change of the negative electrode plate accompanying repetition of charging / discharging could be prevented.

  Therefore, an object of the present invention is to prevent the shape change of the negative electrode plate accompanying repetition of charge and discharge in a zinc secondary battery capable of preventing zinc dendrite extension provided with an LDH separator.

According to one aspect of the invention:
A positive electrode plate including a positive electrode active material layer and a positive electrode current collector,
A negative electrode plate comprising a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy and a zinc compound, and a negative electrode current collector,
A layered double hydroxide (LDH) separator, which separates the positive electrode plate and the negative electrode plate so as to allow hydroxide ion conduction;
An electrolytic solution,
A zinc secondary battery provided with
The size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, whereby the negative electrode active material layer has an extra peripheral region along the outer periphery thereof not facing the positive electrode active material layer,
The zinc secondary battery has a positive electrode reaction suppression structure that suppresses an electrochemical reaction at an end of the positive electrode active material layer, and / or suppresses an electrochemical reaction in the surplus outer peripheral region of the negative electrode active material layer. A zinc secondary battery having a negative electrode reaction suppression structure, whereby the electrochemical activity at the end of the positive electrode active material layer and / or the surplus outer peripheral region of the negative electrode active material layer is locally reduced. Provided.

It is a schematic cross section which shows an example of the internal structure of the zinc secondary battery of this invention. It is a figure for demonstrating the mechanism of the shape change of the negative electrode plate in a zinc secondary battery, While the perspective view of a negative electrode plate is shown by the upper stage, sectional drawing of a negative electrode plate is shown with a LDH separator in the lower stage. It is a conceptual diagram for demonstrating the phenomenon considered to occur in the electrode end part in the zinc secondary battery which does not have an LDH separator, a positive electrode reaction suppression structure, and a negative electrode reaction suppression structure. It is a conceptual diagram for demonstrating the phenomenon considered to occur in an electrode edge part in the zinc secondary battery of this invention. It is a process flowchart which provides a positive electrode reaction suppression structure with a liquid retaining member in a positive electrode plate, and is a figure which shows the process of the first half. A top view is shown in the upper part, and its A-A 'line sectional view is shown in the lower part. It is a process flowchart which provides a positive electrode reaction suppression structure with a liquid retaining member in a positive electrode plate, and is a figure which shows the process of the second half following FIG. 5A. A top view is shown in the upper part, and a B-B 'line sectional view is shown in the lower part. 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. 8A, and its periphery structure. It is a SEM image which shows the cross-section microstructure of the LDH separator produced in Example 1. FIG.

Zinc Secondary Battery The zinc secondary battery of the present invention is not particularly limited as long as it is a secondary battery using zinc as a negative electrode and an alkaline electrolyte (typically, an aqueous solution of an alkali metal hydroxide). Therefore, a nickel zinc secondary battery, a silver oxide zinc secondary battery, a manganese zinc oxide secondary battery, an air zinc secondary battery, and various other alkaline zinc secondary batteries can be used. 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 an air zinc secondary battery.

  The zinc secondary battery of the present invention is schematically shown in FIG. The zinc secondary battery shown in FIG. 1 includes a battery element 11, which includes a positive electrode plate 12, a negative electrode plate 16, a layered double hydroxide (LDH) separator 22, and an electrolyte (not shown). ). The positive electrode plate 12 includes a positive electrode active material layer 13 and a positive electrode current collector 14. The negative electrode plate 16 includes a negative electrode active material layer 17 and a negative electrode current collector 18, and the negative electrode active material layer 17 includes at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. The LDH separator 22 separates the positive electrode plate 12 and the negative electrode plate 16 so as to allow hydroxide ion conduction. 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. The size of the negative electrode active material layer 17 is larger than the size of the positive electrode active material layer 13, so that the negative electrode active material layer 17 has an extra peripheral region along which the positive electrode active material layer 13 does not face. And a zinc secondary battery has the positive electrode reaction suppression structure 15 which suppresses the electrochemical reaction in the edge part of the positive electrode active material layer 13, and / or suppresses the electrochemical reaction in the excessive outer periphery area | region of the negative electrode active material layer 17. The negative electrode reaction suppression structure 19 is provided. Thus, the electrochemical activity at the end of the positive electrode active material layer 13 and / or the surplus outer peripheral region of the negative electrode active material layer 17 is locally reduced. By adopting such a reaction suppression structure, it is possible to prevent the shape change of the negative electrode plate 16 (in particular, the negative electrode active material layer 17) due to the repetition of charge and discharge, and as a result, the battery resistance caused by the shape change of the negative electrode plate Can be effectively prevented. In addition, the zinc secondary battery of the present invention can be provided with the LDH separator 22 to prevent zinc dendrite extension, thereby preventing a short circuit between positive and negative electrodes.

As described above, in the conventional zinc secondary battery, there is a problem that the shape of the negative electrode plate gradually changes as charge and discharge are repeated. Such a change in shape of the negative electrode plate leads to a decrease in the effective area of the negative electrode facing the positive electrode plate, resulting in an increase in battery resistance and a decrease in battery capacity. As one of the main causes of the change in shape of the negative electrode plate, the presence of excess electrolyte 21 at the end of the negative electrode plate 16 as shown in FIG. 2 is considered. That is, as shown in the “initial” of FIG. 2, a dead space DS is usually present around the end of the negative electrode active material layer 17 (ZnO layer) to allow the presence of the excess electrolyte 21. The negative electrode active material layer 17 may be covered with a liquid holding member 20 such as a non-woven fabric, but since the liquid holding member 20 passes the electrolyte solution 21, the space between the liquid holding member 20 and the negative electrode active material layer 17 It can be said that the space formed in the space also allows the presence of the excess electrolyte 21 and becomes a dead space DS. And, in such dead space DS, because of the extra electrolyte 21, as shown in the sectional view of the lower part of FIG. 2, zinc ion Zn is a component of the electrolyte solution 21 (OH) ₄ ^2- is It will be present in excess. And, as shown in “charging” (second from left) in FIG.
_{- ZnO + H 2 O + 2OH} - → Zn (OH) 4 2-
^{_{- Zn (OH) 4 2- +}} 2e - → Zn + 4OH -
Charging is performed according to. At this time, metal Zn is intensively deposited at the end of the negative electrode active material layer 17 (ZnO layer) due to the extra electrolyte solution 21 in the dead space DS, and the concentrated Zn is metal Zn (a metal. Electrons are further concentrated on the collector (which can function as a collector) to increase the nonuniformity of the charging reaction. In this respect, ideally, it is desirable that Zn be deposited inside while maintaining the skeleton of ZnO, but this is not the case at the negative electrode end. Then, as shown in “Discharge” of FIG.
_{^{- Zn + 4OH - → Zn (}} OH) 4 2- + 2e -
^{_{- Zn (OH) 4 2- →}} ZnO + H 2 O + 2OH -
Discharge is performed according to At this time, Zn (OH) ₄ ²⁻ derived from the concentrated Zn metal is supersaturated and precipitated as ZnO on the ZnO nucleus. Since this precipitation reaction is slow, Zn (OH) ₄ ²⁻ easily diffuses, and as a result, ZnO is deposited in the central portion of the anode active material layer 17 rich in ZnO nuclei. When such charging and discharging are repeated many times, as shown in “charging” on the right end of FIG. In the direction of the arrow in the photograph, the non-uniform contraction occurs, that is, the outer peripheral portion of the negative electrode active material layer 17 is non-uniformly eroded and lost. In short, the shape change of the negative electrode plate 16 due to the repetition of charge and discharge is concentrated of the metal Zn at the end of the negative electrode active material layer 17 (ZnO layer) due to the extra electrolyte 21 in the dead space DS at the time of charge reaction. It is believed that this is caused by the precipitation of Zn and the metal Zn diffuses as Zn (OH) ₄ ^2- at the time of discharge reaction and precipitates as ZnO at the central portion of the negative electrode.

Further, as shown in FIG. 3, as another factor for promoting the change in shape of the negative electrode plate 16 as described above, a gap at an end position between the positive electrode active material layer 13 and the negative electrode active material layer 17 is also considered. That is, in the zinc secondary battery, in order to suppress an increase in reaction precipitates at the end of the negative electrode active material layer 17 due to current concentration at the end of the positive electrode active material layer 13, the size of the negative electrode active material layer 17 is Although it is desirable to design the cathode active material layer 13 to be slightly larger than the size of the cathode active material layer 13, an extra peripheral region ER in which the anode active material layer 17 does not face the cathode active material layer 13 is formed along the periphery thereof. Become. Then, as shown in FIG. 3, a large amount of OH from the surplus outer peripheral region ER of the negative electrode active material layer 17 (including not only the layer surface of the negative electrode active material layer 17 but also the end surface) toward the end of the positive electrode active material layer 13 ^- is believed to be that the ions go around. Thus, locally promoting the reaction in the surplus outer peripheral region ER of the negative electrode active material layer 17 (including not only the layer surface of the negative electrode active material layer 17 but also the end face) promotes the shape change of the negative electrode plate It is considered to be the cause.

  Based on the above consideration, in order to prevent the shape change of the negative electrode plate 16 (particularly the negative electrode active material layer 17) due to the repetition of charge and discharge, the positive electrode which suppresses the electrochemical reaction at the end of the positive electrode active material layer 13 It can be said effective to provide the reaction suppression structure 15 or to provide the negative electrode reaction suppression structure 19 for suppressing the electrochemical reaction in the surplus outer peripheral region ER of the negative electrode active material layer 17. The positive electrode reaction suppression structure 15 is not particularly limited as long as it can selectively and locally suppress the electrochemical reaction at the end of the positive electrode active material layer 13, and any structure or material may be used. Similarly, the negative electrode reaction suppression structure 19 is not particularly limited as long as it can selectively and locally suppress the electrochemical reaction in the surplus outer peripheral region ER of the negative electrode active material layer 17, and any structure or material can be used. It is also good. As a result, the electrochemical activity in the end portion of the positive electrode active material layer 13 and / or the surplus outer peripheral region ER of the negative electrode active material layer 17 is locally reduced, so that the negative electrode plate 16 (in particular, the negative electrode active material layer 17 The above-mentioned factor causing the shape change of (i.e., excessive electrochemical reaction at or near the electrode end) can be suppressed, and as a result, the shape change of the negative electrode plate due to repeated charge and discharge can be prevented. . In order to realize this effect more effectively, the zinc secondary battery 10 has both the positive electrode reaction suppression structure 15 and the negative electrode reaction suppression structure 19, whereby the end of the positive electrode active material layer 13 and the negative electrode active It is more preferable that the electrochemical activity in both of the surplus outer peripheral region ER of the material layer 17 be locally reduced.

According to a preferred embodiment of the present invention, as shown in FIGS. 1 and 4, the zinc secondary battery has the positive electrode reaction suppression structure 15 adjacent to the end of the positive electrode active material layer 13. In this case, it is preferable that the positive electrode reaction suppression structure 15 includes an inactive member made of an electrochemically inactive material, and the inactive member covers the end of the positive electrode active material layer 13. The shape of the inactive member is not particularly limited, and may be film-like or bulk-like. For example, it is particularly preferable that the inactive member form a spacer that is adjacent to the end of the positive electrode plate 12 and closes the region facing the extra peripheral region ER of the negative electrode plate 16. By doing this, as shown in FIG. 4, the charge / discharge reaction at the end of the positive electrode active material layer 13 is eliminated (that is, inactivated), so the surplus outer peripheral region ER of the negative electrode active material layer 17 (negative electrode active It is possible to effectively prevent the phenomenon (see FIG. 3) that OH ⁻ ions wrap around from the end face of the material layer 17 toward the end of the positive electrode active material layer 13. As a result, it is possible to effectively prevent the shape change of the negative electrode plate 16 (particularly, the negative electrode active material layer 17) due to the repetition of charge and discharge. The electrochemically inactive material used for the positive electrode reaction suppression structure 15 is preferably a polymer material, and as a preferable example of such a polymer material, an alkaline solution such as polypropylene, polyolefin, polyethylene, epoxy, etc. Among them are resins exhibiting durability. An example of the method of providing the positive electrode reaction suppression structure 15 with the liquid retaining member 20 in the positive electrode plate 12 is shown by FIG. 5A and 5B. In this method, as shown in FIG. 5A, a liquid holding member 20 such as a non-woven fabric is placed in a rectangular recess of a tray-like mold 23, and a positive electrode plate 12 of a smaller size is placed on the liquid holding member 20. To place a margin along the three outer sides. Then, as shown in FIG. 5B, the hot melt adhesive is filled in the margin (exposed portion of the liquid retaining member 20) along the three outer sides of the positive electrode plate 12 to form a spacer as the positive electrode reaction suppression structure 15. A liquid holding member 20 such as a non-woven fabric is placed to cover the positive electrode reaction suppression structure 15 and the positive electrode plate 12. The pressure plate 25 is placed on the liquid holding member 20 and pressurized to adjust the entire shape of the positive electrode structure into a flat plate having a uniform thickness, and then the mold 23 and the pressure plate 25 are removed. A positive electrode structure provided with the liquid member 20 and the positive electrode reaction suppression structure 15 is obtained. Therefore, the mold 23 and the pressing plate 25 may be made of a material that can be easily removed from the hot melt adhesive, and is preferably made of Teflon (registered trademark). The adhesive is not limited to the hot melt adhesive, and a wide variety of adhesives can be used.

Alternatively, as another preferred embodiment of the present invention, zinc secondary battery 10 may have a negative electrode reaction suppression structure adjacent to surplus outer peripheral region ER of negative electrode active material layer 17. In this case, it is preferable that the negative electrode reaction suppression structure includes an inactive member made of an electrochemically inactive material, and the inactive member covers the surplus outer peripheral region ER of the negative electrode active material layer. The shape of the inactive member is not particularly limited, and may be film-like or bulk-like. By doing this, the place of charge / discharge reaction in the extra peripheral region ER of the negative electrode active material layer 17 is eliminated (that is, inactivated), the extra peripheral region ER of the negative electrode active material layer 17 (end face of the negative electrode active material layer 17 the included) from towards the end of the positive electrode active material layer 13 OH ^- see the phenomenon (Fig. 3 which ions go around) can be effectively prevented. As a result, it is possible to effectively prevent the shape change of the negative electrode plate 16 (particularly, the negative electrode active material layer 17) due to the repetition of charge and discharge. The electrochemically inactive material used for the negative electrode reaction suppression structure is preferably a polymer material, and preferable examples of such a polymer material include an alkaline solution such as polypropylene, polyolefin, polyethylene, epoxy, etc. And resins that exhibit durability.

  Hereinafter, the battery element 11 of the zinc secondary battery of the present invention will be described. As shown in FIG. 1, the battery element 11 includes a positive electrode plate 12, a negative electrode plate 16, an LDH separator 22, and an electrolyte (not shown).

  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 known positive electrode materials according to the type of zinc secondary battery, and is not particularly limited. For example, in the case of a nickel zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. Alternatively, in the case of an air zinc secondary battery, the air electrode may be used as the positive electrode. The positive electrode plate 12 further includes a positive electrode current collector (not shown). The positive electrode current collector preferably has a positive electrode current collecting tab 14 a extending from one side of the positive electrode active material layer 13. A preferable example of the positive electrode current collector is a porous substrate made of nickel such as a foamed nickel plate. In this case, for example, by uniformly applying and drying a paste containing an electrode active material such as nickel hydroxide on a nickel porous substrate, a positive electrode plate composed of a positive electrode / positive electrode current collector can be preferably produced. . At that time, it is also preferable to press-process the dried positive electrode plate (that is, the positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. The positive electrode plate 12 shown in FIG. 1 contains a positive electrode current collector (for example, foamed nickel), but is not shown. This is because the positive electrode current collector is integrated with the positive electrode active material layer 13 so that the positive electrode current collector can not be drawn separately. The zinc secondary battery 10 preferably further includes a positive electrode current collector plate connected to the tip of the positive electrode current collector tab 14a, and more preferably, a plurality of positive electrode current collector tabs 14a are connected to one positive electrode current collector plate . In this way, current collection can be performed space-efficiently with a simple configuration, and connection to the positive electrode terminal can be facilitated. Also, the positive electrode current collector itself may be used as a 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, 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 17 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 an effect of suppressing 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 coping with large current discharge. It is easy to mix uniformly with the agent, and the handling at the time of battery assembly is also good.

  The negative electrode plate 16 further includes a negative electrode current collector 18. The negative electrode current collector 18 preferably has a negative electrode current collection tab 18 a extending from one side of the negative electrode active material layer 17. As shown in FIG. 1, the negative electrode current collection tab 18a extends beyond the end of the LDH separator 22 from one side of the negative electrode active material layer 17 opposite to the positive electrode current collection tab 14a. In this case, the battery element 11 can collect current from opposite sides through the positive electrode current collecting tab 14a and the negative electrode current collecting tab 18a. Alternatively, the negative electrode current collection tab 18a may extend beyond the end of the LDH separator 22 from a different position on one side of the negative electrode active material layer 17 on the same side as the positive electrode current collection tab 14a. In the case, the battery element 11 can collect current from the same side via the positive electrode current collecting tab 14a and the negative electrode current collecting tab 18a. In any case, the zinc secondary battery 10 preferably further includes a negative electrode current collector plate connected to the tip of the negative electrode current collector tab 18a, and more preferably, a plurality of negative electrode current collector tabs 18a is one negative electrode current collector Connected to the board. In this way, current collection can be performed space-efficiently with a simple configuration, and connection to the negative electrode terminal can be facilitated. Also, the negative electrode current collector itself may be used as a negative electrode terminal. Typically, the tip end portion of the negative electrode current collection tab 18 a forms an exposed portion not covered by the LDH separator 22 and the liquid retaining member 20 (if present). Thereby, the negative electrode current collector 18 (particularly, the negative electrode current collection tab 18a) can be desirably connected to the negative electrode current collector plate and / or the negative electrode terminal through the exposed portion.

  Preferred examples of the negative electrode current collector 18 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.

  Preferably, the zinc secondary battery 10 further includes a liquid retaining member 20 between the LDH separator 22 and the negative electrode active material layer 17, and the liquid retaining member 20 is impregnated with an electrolytic solution. More preferably, a liquid retaining member 20 which covers the entire negative electrode active material layer 17 is provided. By this, the electrolytic solution can be uniformly present between the negative electrode active material layer 17 and the LDH separator 22, and the exchange of hydroxide ions between the negative electrode active material layer 17 and the LDH separator 22 can be realized. It can be done efficiently. The liquid holding member 20 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 fabrics, water absorbing resins, liquid retaining resins, porous sheets, and various spacers, and particularly preferred are nonwoven fabrics in that they can produce a negative electrode structure with good performance at low cost. . The liquid holding 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, particularly preferably It is 0.02 to 0.10 mm, and 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 20 while suppressing the entire size of the negative electrode structure compactly without waste.

  As described above, it is preferable that the entire negative electrode active material layer 17 be covered with the LDH separator 22. That is, 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. In this respect, when the entire negative electrode active material layer 17 is covered with the LDH separator 22, the negative electrode plate 16 itself covered with the LDH separator 22 has a function capable of preventing a short circuit or the like due to zinc dendrite. Therefore, separation of the positive electrode plate 12 and the negative electrode plate 16 by the LDH separator can be realized only by laminating the positive electrode plate 12 and the negative electrode plate 16 (which is covered with the LDH separator 22). As described above, by covering the entire negative electrode active material layer 17 with the LDH separator 22 (through the liquid holding member 20 as necessary), the complicated sealing and bonding between the LDH separator 22 and the battery container is eliminated. It is possible to produce a zinc secondary battery (particularly, a laminated battery thereof) capable of preventing the extension of zinc dendrite extremely easily and with high productivity.

When the whole of the negative electrode active material layer 17 is covered with the LDH separator 22, the negative electrode reaction suppression structure 19 can be configured by the LDH separator 22 itself. That is, the negative electrode reaction suppression structure 19 has a structure in which the LDH separator 22 and the end of the negative electrode active material layer 17 are in direct or indirect contact with each other, whereby the LDH separator 22 and the negative electrode active material layer 17 are It is preferable that there is no excess space between the end and the electrolyte solution. That is, as described with reference to FIG. 2, when the excess electrolyte 21 is present between the LDH separator 22 and the end portion of the negative electrode active material layer 17, the negative electrode active material layer 17 (ZnO layer) is The shape change of the negative electrode plate 16 can be achieved by the metal Zn being intensively deposited at the end and being diffused as Zn (OH) ₄ ²⁻ during the discharge reaction and being diffused as ZnO at the central portion of the negative electrode. It can cause. Therefore, by eliminating the excess space that allows electrolyte solution accumulation, it is possible to effectively prevent the shape change of the negative electrode plate 16 (particularly, the negative electrode active material layer 17) due to the repetition of charge and discharge. A liquid retaining member 30 may be present between the LDH separator 22 and the end of the negative electrode active material layer 17 so as not to provide an excess space for allowing electrolyte solution accumulation. In addition, the resin may be filled between the LDH separator 22 and the end of the negative electrode active material layer 17 to eliminate an excess space for allowing the electrolyte solution to be accumulated.

  The LDH separator 22 includes LDH and a porous substrate. As mentioned above, the pores of the porous substrate are such that the LDH separator 22 exhibits hydroxide ion conductivity and gas impermeability (so that it functions as an LDH separator exhibiting hydroxide ion conductivity) Blocking The porous substrate is preferably made of a polymeric material, and the LDH is particularly preferably incorporated throughout the thickness direction of the polymeric porous substrate. Various preferred embodiments of the LDH separator 22 will be described in detail later.

  When the whole of the negative electrode active material layer 17 is covered with the LDH separator 22, the LDH separator 22 has at least one side (preferably at least two sides) of its outer edge so as to wrap the negative electrode active material layer 17 as shown in FIG. It is a closed structure. In this case, it is preferable that the closed side C of the outer edge of the LDH separator 22 be realized by bending the LDH separator 22 and / or sealing the LDH separators 22 with each other. Preferred examples of sealing techniques include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. In particular, since the LDH separator 22 including a porous base material made of a polymer material has the advantage of flexibility and is therefore easily bendable, the outer edge is formed by forming the LDH separator 22 in a long shape and bending it. Preferably, one side C of the two forms a closed state. Although heat welding and ultrasonic welding may be performed using a commercially available heat sealer or the like, in the case of sealing the LDH separators 22 with each other, the outer peripheral portion of the liquid retaining member 20 is sandwiched between the LDH separators 22 forming the outer peripheral portion. It is preferable to perform heat welding and ultrasonic welding in this manner in that more effective sealing can be 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.

  As a modification, instead of covering the whole of the negative electrode active material layer 17 with the LDH separator 22, the whole of the positive electrode active material layer 13 may be covered with the LDH separator 22. In this modified embodiment, the positive electrode plate 12 itself covered with the LDH separator 22 can have a function capable of preventing a short circuit or the like due to zinc dendrite. In the case of this modification, the zinc secondary battery 10 preferably further includes a liquid retaining member 20 between the LDH separator 22 and the positive electrode active material layer 13, and the liquid retaining member 20 is impregnated with an electrolytic solution. Is preferred.

  The electrolyte preferably comprises an aqueous alkali metal hydroxide solution. Although the electrolytic solution is not shown, it is because it extends throughout the 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, with potassium hydroxide being more preferred. In order to suppress the self-dissolution of zinc and / or zinc oxide, a zinc compound such as zinc oxide or zinc hydroxide may be added to the electrolytic solution. As described above, the electrolytic solution may be mixed with the positive electrode active material and / or the negative electrode active material to be present in the form of a positive electrode mixture and / or a negative electrode mixture. In addition, in order to prevent leakage of the electrolytic solution, the electrolytic solution may be gelled. As the gelling agent, it is desirable to use a polymer which absorbs the solvent of the electrolytic solution to swell, and polymers such as polyethylene oxide, polyvinyl alcohol, polyacrylamide and starch are used.

  The zinc secondary battery 10 may further include a case (not shown) for housing the battery element 11. Also, the number of battery elements 11 may be two or more, and the two or more battery elements 11 may be housed together in a case. This is a configuration of a so-called assembled battery or laminated battery, and is advantageous in that high voltage and large current can be obtained. The case for housing the battery element 11 is preferably made of resin. The resin constituting the case 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, still more preferably an ABS resin or a modified resin It is polyphenylene ether. In addition, a case group in which two or more cases are arranged may be accommodated in the outer frame, and the battery module may be configured.

LDH Separator The LDH separator 22 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 22 exhibits a function as a hydroxide ion conductive separator. Preferred LDH separators 22 are gas impermeable and / or water impermeable. In other words, the LDH separator 22 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 22 has gas impermeability and / or water impermeability means that the LDH separator 22 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 doing this, the LDH separator 22 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 22 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 22 preferably has a He permeability of 10 cm / min · atm or less per unit area, 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 at the time of He gas permeation, and the membrane area S at 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, the anions in LDH comprise OH ^- and / or CO ₃ ^2- . 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, ^{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 + 2y) / n · mH 2 O ( ^{wherein, a n-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 22. In addition, since the porous base material can impart strength, the LDH separator 22 can be thinned to reduce resistance.

  As mentioned above, the LDH separator 22 comprises (and typically consists of) LDH and a porous substrate, and the LDH separator 22 exhibits hydroxide ion conductivity and gas impermeability (hence, The LDH blocks the pores of the porous substrate so as to function as an LDH separator exhibiting hydroxide ion conductivity. It is particularly preferable that LDH be incorporated throughout the thickness direction of the polymeric porous substrate. The thickness of the LDH separator 22 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 made 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. Also, by taking advantage of the flexibility derived from the above 1), 5) the LDH separator 22 including a porous base material made of a polymer material can be easily bent or sealed and joined as described above There is also the advantage that at least one side of the outer edge of the LDH separator 22 can be easily formed in a closed state (in the case of bending, it also offers the advantage of being 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 preferred 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, for example 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, 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 composed of a polymer material and the LDH is incorporated throughout the thickness direction of the porous substrate, the porosity of the porous substrate is preferably 30 to 60%, more preferably Is 40 to 60%.

The method for producing the LDH separator 22 is not particularly limited, and the LDH-containing functional layer and the composite material (that is, the LDH separator) are produced by appropriately changing various conditions of known methods (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.

  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 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 Co., Ltd.) The XRD profile was obtained. About the obtained XRD profile, JCPDS card NO. It identified 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-std-frequency response analyzer, model 1287A and 1255B made by Solartron) in a frequency range of 1 MHz to 0.1 Hz and an 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. 7A and 7B, 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. 8A and 8B 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. 9, 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.

DESCRIPTION OF SYMBOLS 10 zinc secondary battery 11 battery element 12 positive electrode plate 13 positive electrode active material layer 14a positive electrode current collection tab 15 positive electrode reaction suppression structure 16 negative electrode plate 17 negative electrode active material layer 18 negative electrode current collector 18a negative electrode current collection tab 19 negative electrode reaction suppression structure 20 Liquid holding member 21 Electrolyte 22 LDH separator 23 type 25 Push plate C Closed side DS Dead space

Claims (15)

A positive electrode plate including a positive electrode active material layer and a positive electrode current collector,
A negative electrode plate comprising a negative electrode active material layer comprising at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy and a zinc compound, and a negative electrode current collector,
A layered double hydroxide (LDH) separator, which separates the positive electrode plate and the negative electrode plate so as to allow hydroxide ion conduction;
An electrolytic solution,
A zinc secondary battery provided with
The size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, whereby the negative electrode active material layer has an extra peripheral region along the outer periphery thereof not facing the positive electrode active material layer,
The zinc secondary battery has a positive electrode reaction suppression structure that suppresses an electrochemical reaction at an end of the positive electrode active material layer, and / or suppresses an electrochemical reaction in the surplus outer peripheral region of the negative electrode active material layer. A zinc secondary battery having a negative electrode reaction suppression structure, whereby the electrochemical activity in the end portion of the positive electrode active material layer and / or the extra peripheral region of the negative electrode active material layer is locally reduced.   It has both the positive electrode reaction suppression structure and the negative electrode reaction suppression structure, thereby locally reducing the electrochemical activity in both the end of the positive electrode active material layer and the surplus outer peripheral region of the negative electrode active material layer The zinc secondary battery according to claim 1, which is   The zinc secondary battery has the positive electrode reaction suppression structure adjacent to an end of the positive electrode active material layer, and the positive electrode reaction suppression structure is formed of an electrochemically inactive material. The zinc secondary battery according to claim 2, comprising an active member, wherein the inactive member covers an end of the positive electrode active material layer.   The zinc secondary battery according to claim 3, wherein the inactive member is a spacer that is adjacent to an end of the positive electrode plate and closes a region facing the extra peripheral region of the negative electrode plate.   The zinc secondary battery according to claim 3, wherein the electrochemically inactive material is a polymer material.   The zinc secondary battery has the negative electrode reaction suppression structure adjacent to the surplus outer peripheral region of the negative electrode active material layer, and the negative electrode reaction suppression structure is made of an electrochemically inactive material. The zinc secondary battery according to any one of claims 2 to 5, further comprising an inactive member, wherein the inactive member covers the surplus outer peripheral region of the negative electrode active material layer.   The zinc secondary battery according to claim 6, wherein the electrochemically inactive material is a polymer material. The entire negative electrode active material layer is covered with the LDH separator,
The negative electrode reaction suppression structure has a structure in which the LDH separator and an end portion of the negative electrode active material layer are in direct or indirect contact with each other, thereby the ends of the LDH separator and the negative electrode active material layer The zinc secondary battery according to any one of claims 1 to 7, wherein there is no surplus space which allows an electrolytic solution pool between the part and the part.   9. The zinc secondary battery according to any one of claims 1 to 8, further comprising a liquid retaining member between the LDH separator and the negative electrode active material layer, wherein the liquid retaining member is impregnated with the electrolytic solution. The zinc secondary battery according to any one of the preceding claims.   The zinc secondary battery according to claim 9, wherein the liquid retaining member is a non-woven fabric.   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 zinc secondary battery as described in any one of 1-10.   The zinc secondary battery according to claim 11, wherein the porous substrate is made of a polymer material.   The zinc secondary battery according to any one of claims 10 to 12, wherein the LDH is incorporated throughout the thickness direction of the porous substrate.   The zinc positive electrode according to any one of claims 1 to 13, wherein the positive electrode active material layer comprises nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery constitutes a nickel zinc secondary battery. Next battery. The zinc secondary battery according to any one of claims 1 to 13, wherein the positive electrode active material layer is an air electrode layer, whereby the zinc secondary battery forms an air zinc secondary battery.