Zinc secondary battery

Abstract

The invention provides a zinc secondary battery which has good battery resistance and is capable of effectively suppressing electrolyte leakage caused by a creep phenomenon. This zinc secondary battery is provided with: 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 including at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds, and a negative electrode current collector; a hydroxide ion conduction separator which separates the positive electrode plate and the negative electrode plate in a hydroxide ion conduction manner; and an electrolyte solution. The electrolyte solution is an aqueous solution containing an alkali metal hydroxide, the alkali metal hydroxide containing at least sodium hydroxide, the total concentration of the alkali metal hydroxide in the electrolyte solution being 5.0-6.0 mol / L, and the concentration of sodium hydroxide in the electrolyte solution being 0.5-6.0 mol / L.

Description

Technical Field

[0001] The present invention relates to a zinc secondary battery. Background Art

[0002] In alkaline batteries, a phenomenon called creep (Japanese: クリープ) (hereinafter referred to as the creep phenomenon) is known. The creep phenomenon refers to a phenomenon in which the alkali component in the electrolyte diffuses over the surface of the electrode terminal and leaks to the outside of the battery container. Here, several batteries for coping with the creep phenomenon have been proposed. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 7-254396), in a button-type alkaline battery using mercury-free zinc as a negative electrode active material, the inner surface of the negative electrode terminal plate is coated with tin or a tin alloy by 10 to 100 μm and its surface is polished, whereby the amount of tin oxide on the surface is controlled to a given amount. Further, in Patent Document 2 (Japanese Patent No. 6561915), a nickel-hydrogen battery is disclosed, which forms a non-conductive layer on the surface of the electrode terminal and a metal layer containing nickel and / or a nickel-iron alloy is laminated on the non-conductive layer.

[0003] However, in zinc secondary batteries such as nickel-zinc secondary batteries and zinc-air secondary batteries, it is known that during charging, metallic zinc precipitates in a dendritic shape from the negative electrode, penetrates through the gaps of a separator such as non-woven fabric and reaches the positive electrode, and as a result, a short circuit occurs. Such a short circuit caused by zinc dendrites leads to a shortening of the repeated charge-discharge life. In order to cope with this problem, a battery having a layered double hydroxide (LDH) separator has been proposed, which selectively allows hydroxide ions to pass through but prevents zinc dendrites from penetrating (for example, refer to Patent Document 3 (International Publication No. 2016 / 076047), Patent Document 4 (International Publication No. 2019 / 124270)). Further, in Patent Document 5 (International Publication No. 2019 / 069760) and Patent Document 6 (International Publication No. 2019 / 077953), a zinc secondary battery having the following structure has been proposed: the entire negative electrode active material layer is covered or wrapped with a liquid retention member and an LDH separator, and the positive electrode active material layer is covered or wrapped with a liquid retention member. As the liquid retention member, non-woven fabric is used. According to this structure, a complicated sealing joint between the LDH separator and the battery container is not required, and a zinc secondary battery (especially its laminated battery) capable of preventing the extension of zinc dendrites can be produced extremely simply and with high productivity.

[0004] Further, as hydroxides and / or oxides having a layered crystal structure similar to, although not necessarily called, LDH, LDH-like compounds are known to exhibit similar hydroxide ion conduction characteristics, such that they can be collectively referred to as hydroxide ion-conducting layered compounds together with LDH. For example, in Patent Document 7 (International Publication No. 2020 / 255856), a hydroxide ion-conducting separator is disclosed, which includes a porous substrate and a layered double hydroxide (LDH)-like compound filling the pores of the porous substrate. The LDH-like compound is a hydroxide and / or oxide having a layered crystal structure, and the hydroxide and / or oxide having the layered crystal structure includes: Mg; and at least one element containing Ti selected from Ti, Y, and Al. Further, in Patent Document 8 (International Publication No. 2021 / 229916), an LDH separator using an LDH-like compound is disclosed, and the LDH-like compound includes (i) Ti, Y, and optionally Al and / or Mg, and (ii) an additive element M selected from at least one of In, Bi, Ca, Sr, and Ba. Further, in Patent Document 9 (International Publication No. 2021 / 229917), regarding an LDH separator including a mixture of an LDH-like compound and In(OH)3, the LDH-like compound is a hydroxide and / or oxide having a layered crystal structure including Mg, Ti, Y, and optionally Al and / or In. According to the separators disclosed in Patent Documents 7 to 9, compared with conventional LDH separators, they have excellent alkali resistance and can further effectively suppress short circuits caused by zinc dendrites.

[0005] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Laid-Open No. 7-254396 Patent Document 2: Japanese Patent No. 6561915 Patent Document 3: International Publication No. 2016 / 076047 Patent Document 4: International Publication No. 2019 / 124270 Patent Document 5: International Publication No. 2019 / 069760 Patent Document 6: International Publication No. 2019 / 077953 Patent Document 7: International Publication No. 2020 / 255856 Patent Document 8: International Publication No. 2021 / 229916 Patent Document 9: International Publication No. 2021 / 229917 Summary of the Invention

[0006] As disclosed in Patent Documents 1 and 2, various attempts have been made regarding the creep phenomenon of alkaline batteries, but a method that can more effectively suppress the leakage of the electrolyte is required.

[0007] The present inventors have obtained the following insight: In a zinc secondary battery, by setting the total concentration of alkali metal hydroxide in the electrolyte to 5.0 to 6.0 mol / L and the concentration of sodium hydroxide to 0.5 to 6.0 mol / L, the battery resistance is good, and the leakage of the electrolyte caused by the creep phenomenon can be effectively suppressed.

[0008] Therefore, an object of the present invention is to provide a zinc secondary battery having good battery resistance and capable of effectively suppressing the leakage of the electrolyte caused by the creep phenomenon.

[0009] According to the present invention, the following solutions are provided.

[0010] [Solution 1] A zinc secondary battery, comprising: 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 and a negative electrode current collector, the negative electrode active material layer including at least one selected from zinc, zinc oxide, zinc alloy, and zinc compound; A hydroxide ion-conducting separator that separates the positive electrode plate and the negative electrode plate in a manner capable of hydroxide ion conduction; and An electrolyte, The electrolyte is an aqueous solution containing an alkali metal hydroxide, and the alkali metal hydroxide includes at least sodium hydroxide, The total concentration of the alkali metal hydroxide in the electrolyte is 5.0 to 6.0 mol / L, and the concentration of sodium hydroxide in the electrolyte is 0.5 to 6.0 mol / L.

[0011] [Solution 2] The zinc secondary battery according to Solution 1, wherein the concentration of sodium hydroxide in the electrolyte is 2.5 to 6.0 mol / L.

[0012] [Solution 3] The zinc secondary battery according to Solution 1 or 2, wherein the ratio of the concentration of sodium hydroxide to the total concentration of the alkali metal hydroxide is 0.4 to 1.0.

[0013] [Solution 4] The zinc secondary battery according to any one of Solutions 1 to 3, wherein the alkali metal hydroxide includes only the sodium hydroxide.

[0014] [Solution 5] The zinc secondary battery according to any one of Schemes 1 to 3, wherein the alkali metal hydroxide further contains potassium hydroxide.

[0015] [Scheme 6] The zinc secondary battery according to Scheme 5, wherein the concentration of potassium hydroxide in the electrolyte is 3.0 mol / L or less.

[0016] [Scheme 7] The zinc secondary battery according to any one of Schemes 1 to 3, 5 or 6, wherein the alkali metal hydroxide further contains lithium hydroxide.

[0017] [Scheme 8] The zinc secondary battery according to Scheme 7, wherein the concentration of lithium hydroxide in the electrolyte is 1.5 mol / L or less.

[0018] [Scheme 9] The zinc secondary battery according to any one of Schemes 1 to 8, wherein the hydroxide ion conductive separator is an LDH separator containing layered double hydroxide (LDH) and / or LDH-like compound.

[0019] [Scheme 10] The zinc secondary battery according to Scheme 9, wherein the LDH separator further contains a porous substrate, and the LDH and / or LDH-like compound is compounded with the porous substrate in a form filling the pores of the porous substrate.

[0020] [Scheme 11] The zinc secondary battery according to Scheme 10, wherein the porous substrate is made of a polymer material.

[0021] [Scheme 12] The zinc secondary battery according to any one of Schemes 1 to 11, wherein the positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery constitutes a nickel-zinc secondary battery.

[0022] [Scheme 13] The zinc secondary battery according to any one of Schemes 1 to 11, wherein the positive electrode active material layer is an air electrode layer, whereby the zinc secondary battery constitutes a zinc-air secondary battery. Description of the Drawings

[0023] Figure 1 is a schematic cross-sectional view showing an example of the zinc secondary battery according to the present invention.

[0024] Figure 2 is schematically showing Figure 1 a view of the cross-section taken along line A-A' of the zinc secondary battery shown.

[0025] Figure 3 is a schematic representation of Figure 1 a perspective view of the electrode laminate of the zinc secondary battery shown.

[0026] Figure 4 is a schematic representation of Figure 1 a cross-sectional view of the electrode laminate of the zinc secondary battery shown.

[0027] Figure 5 is a cross-sectional view schematically showing an example of the mechanism for preventing the creep phenomenon in the zinc secondary battery of the present invention.

[0028] Figure 6 is a conceptual diagram for explaining the mechanism of the creep phenomenon in the case where an aqueous potassium hydroxide solution is used as the electrolyte.

[0029] Figure 7 is a schematic representation of Figure 6 the mechanism of the electrolyte passing through the minute gap between the metal member and the sealing member. Detailed Embodiments

[0030] 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 the negative electrode and an aqueous alkali metal hydroxide solution having the composition described below as the electrolyte. Therefore, it can be a nickel-zinc secondary battery, a silver-zinc oxide secondary battery, a manganese-zinc oxide secondary battery, a zinc-air secondary battery, or various other alkaline zinc secondary batteries. For example, it is preferable that the positive electrode active material layer contains nickel hydroxide and / or nickel oxyhydroxide, whereby the zinc secondary battery constitutes a nickel-zinc secondary battery. Alternatively, when the positive electrode active material layer is an air electrode layer, the zinc secondary battery can constitute a zinc-air secondary battery.

[0031] Figures 1 to 4 shows one mode of the zinc secondary battery and its internal structure according to the present invention. The zinc secondary battery 10 shown in these figures includes a positive electrode plate 12, a negative electrode plate 14, a hydroxide ion-conducting separator 16, and an electrolyte 18. It should be noted that in Figure 4In [the figure], the electrolyte 18 is only partially illustrated because it permeates the entire positive electrode plate 12 and negative electrode plate 14. The positive electrode plate 12 includes a positive electrode active material layer 12a and a positive electrode current collector (not illustrated). The negative electrode plate 14 includes a negative electrode active material layer 14a and a negative electrode current collector 14b. The negative electrode active material layer 14a contains at least one selected from zinc, zinc oxide, zinc alloys, and zinc compounds. The hydroxide ion-conducting separator 16 separates the positive electrode plate 12 and the negative electrode plate 14 in a manner that allows hydroxide ion conduction. The electrolyte 18 is an aqueous solution containing an alkali metal hydroxide. The alkali metal hydroxide contains at least sodium hydroxide. The total concentration of the alkali metal hydroxide in the electrolyte 18 is 5.0 to 6.0 mol / L. Additionally, the concentration of sodium hydroxide in the electrolyte 18 is 0.5 to 6.0 mol / L. Thus, in the zinc secondary battery, by using the electrolyte 18 in which the total concentration of the alkali metal hydroxide and the concentration of sodium hydroxide are respectively within a given range, the battery resistance is good, and leakage of the electrolyte caused by the creep phenomenon can be effectively suppressed.

[0032] As described above, the creep phenomenon refers to the phenomenon in which the electrolyte spreads over the surface of the electrode terminal, causing the electrolyte to leak out of the battery container. Figure 6 Conceptually represents the mechanism of the creep phenomenon when a part of the metal member 30 (assuming an electrode terminal or a current collector member) is immersed in the electrolyte 118 (assuming an aqueous potassium hydroxide solution). As Figure 6 shown, the creep phenomenon progresses due to the following reasons: 1) H2O molecules from the surrounding environment combine with the electrons e - present in the metal member 30 to generate OH - ; 2) K + in the electrolyte 118 is attracted by the OH - . Thus, the components (KOH) of the electrolyte 118 are generated in the region of the metal member 30 where the electrolyte 118 is absent. As a result, this phenomenon is observed as the electrolyte 118 spreading over the metal member 30. It should be noted that typically, leakage of the electrolyte caused by the creep phenomenon occurs only on the negative electrode side.

[0033] To prevent leakage of the electrolyte, the terminal inside the container and the terminal outside the container are connected via a sealing member such as an O-ring or a gasket. However, as Figure 7 shown, there are minute irregularities on the surface of the metal member 30 such as the electrode terminal, so minute gaps are generated between the metal member 30 and the sealing member 32, and the electrolyte 118 can pass through these minute gaps. In the present invention, by using the electrolyte 18 containing sodium hydroxide at a given concentration as described above, leakage of the electrolyte caused by the creep phenomenon is effectively suppressed. That is, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide are in the form of K + 、Na+ The state after the cations are hydrated exists in the electrolyte. Regarding this, contrary to the ionic radius, Na + has a hydrated ionic radius (about ) that is larger than that of K + (about ). Therefore, it is considered that, as shown in Figure 5 , for the electrolyte 18 containing sodium hydroxide, compared with the aqueous potassium hydroxide solution commonly used as an electrolyte, it is difficult to pass through the minute gap between the metal member 30 and the sealing member 32. In addition, the electrolyte 18 containing a given concentration of sodium hydroxide has a higher viscosity than the aqueous potassium hydroxide solution. As a result, the slower speed at which the electrolyte 18 overflows the metal member 30 is also considered to be one of the factors capable of suppressing the leakage of the electrolyte caused by the creep phenomenon.

[0034] The electrolyte 18 is an aqueous solution containing an alkali metal hydroxide. The total concentration C A of the alkali metal hydroxide in the electrolyte 18 is 5.0 to 6.0 mol / L, preferably 5.0 to 5.8 mol / L, more preferably 5.0 to 5.6 mol / L, and particularly preferably 5.2 to 5.6 mol / L. When within such a range, the resistance of the electrolyte can be ideally reduced, and the performance of the zinc secondary battery can be improved. Examples of the alkali metal hydroxide include potassium hydroxide, lithium hydroxide, etc. in addition to sodium hydroxide.

[0035] The alkali metal hydroxide contained in the electrolyte 18 includes sodium hydroxide. The concentration C B of sodium hydroxide in the electrolyte 18 is 0.5 to 6.0 mol / L, preferably 2.5 to 6.0 mol / L, more preferably 3.0 to 6.0 mol / L, further preferably 4.0 to 6.0 mol / L, further more preferably 5.0 to 6.0 mol / L, particularly preferably 5.0 to 5.8 mol / L, and most preferably 5.2 to 5.6 mol / L. When within such a range, the leakage of the electrolyte caused by the creep phenomenon can be effectively prevented. It should be noted that, needless to say, the concentration C B of this sodium hydroxide is less than or equal to the total concentration C A of the above alkali metal hydroxide (i.e., C B ≤C A ).

[0036] In the electrolyte 18, the ratio of the concentration C B of sodium hydroxide to the total concentration C A of the alkali metal hydroxide (= C B / C A)(Preferably, it is 0.4 to 1.0, more preferably 0.6 to 1.0, still more preferably 0.8 to 1.0, and particularly preferably 0.9 to 1.0. By increasing the proportion of sodium hydroxide in the alkali metal hydroxide in this way, it is possible to more effectively suppress the leakage of the electrolyte caused by the creep phenomenon.)

[0037] )(The alkali metal hydroxide contained in the electrolyte 18 may contain only sodium hydroxide. That is, in the electrolyte 18, the total concentration C of the alkali metal hydroxide) A and the concentration C of sodium hydroxide) B may be the same (C A = C B ). Thus, it is possible to extremely effectively prevent the leakage of the electrolyte. However, due to raw materials, manufacturing processes, etc., it is allowed for alkali metals other than Na to be mixed into the electrolyte 18 as inevitable impurities. That is, even when the alkali metal hydroxide contains only sodium hydroxide, the electrolyte 18 may contain an alkali metal hydroxide other than sodium hydroxide as an inevitable impurity (for example, at a concentration of less than 0.1 mol / L).)

[0038] Alternatively, an alkali metal hydroxide other than sodium hydroxide may be intentionally added to the electrolyte 18. For example, the electrolyte 18 may further contain the aforementioned potassium hydroxide and / or lithium hydroxide as the alkali metal hydroxide.)

[0039] )(By making the alkali metal hydroxide in the electrolyte 18 also contain potassium hydroxide, it is possible to further reduce the battery resistance. On the other hand, from the viewpoint of effectively suppressing the leakage of the electrolyte, it is preferable to limit the addition amount of potassium hydroxide. From these viewpoints, when the alkali metal hydroxide also contains potassium hydroxide, the concentration C of potassium hydroxide in the electrolyte 18) C is preferably 4.0 mol / L or less, more preferably 3.0 mol / L or less, still more preferably 2.0 mol / L or less, particularly preferably 1.5 mol / L or less, and most preferably 1.0 mol / L or less. In addition, the concentration C of potassium hydroxide) C relative to the total concentration C of the alkali metal hydroxide) A )(= C C / C A ) is preferably 0.8 or less, more preferably 0.6 or less, still more preferably 0.4 or less, and particularly preferably 0.3 or less.)

[0040] )(By making the alkali metal hydroxide in the electrolyte 18 also contain lithium hydroxide, it is possible to further suppress the leakage of the electrolyte. That is, Li + and K + as well as Na + compared, the hydrated ion radius is large (about ). In addition, the viscosity of an aqueous lithium hydroxide solution is higher than that of an aqueous sodium hydroxide solution at the same concentration. Therefore, by adding lithium hydroxide to the electrolyte 18, the creep phenomenon can be more effectively prevented. On the other hand, from the viewpoint of effectively reducing the battery resistance, it is preferable to limit the addition amount of lithium hydroxide. From these viewpoints, when the alkali metal hydroxide also contains lithium hydroxide, the concentration C of lithium hydroxide in the electrolyte 18 D is preferably 1.5 mol / L or less, more preferably 1.0 mol / L or less, further preferably 0.1 to 0.8 mol / L or less, and particularly preferably 0.2 to 0.5 mol / L or less. In addition, the concentration C of lithium hydroxide D relative to the total concentration C of the alkali metal hydroxide A ratio (= C D / C A ) is preferably 0.3 or less, more preferably 0 to 0.2, further preferably 0 to 0.15, and particularly preferably 0 to 0.1. When lithium hydroxide is added to the electrolyte 18, from the viewpoint of achieving a good balance between reducing the battery resistance and suppressing the leakage of the electrolyte, it is preferable to add potassium hydroxide to the electrolyte 18 as well. That is, when the alkali metal hydroxide contains sodium hydroxide and lithium hydroxide, it is preferably further contains potassium hydroxide.

[0041] In order to inhibit the self-dissolution of zinc and / or zinc oxide, zinc compounds such as zinc oxide and zinc hydroxide can be added to the electrolyte. In order to more effectively prevent the leakage of the electrolyte, the electrolyte 18 can also be gelled. As the gelling agent, a polymer that swells by absorbing the solvent of the electrolyte is preferably used, and polymers such as polyethylene oxide, polyvinyl alcohol, polyacrylamide, and starch can be used.

[0042] The zinc secondary battery 10 preferably includes an electrode laminate 11 and an electrolyte 18 in a battery container 20. As Figure 3 and Figure 4 shown, the electrode laminate 11 includes a plurality of positive electrode plates 12, a plurality of negative electrode plates 14, and a plurality of hydroxide ion-conducting separators 16, and is formed in a form of a positive-negative electrode laminate laminated in a unit of positive electrode plate 12 / hydroxide ion-conducting separator 16 / negative electrode plate 14. That is, preferably, the zinc secondary battery 10 has a plurality of unit cells 10a, and each unit cell 10a includes a positive electrode plate 12, a positive electrode current collector member 13, a negative electrode plate 14, a negative electrode current collector member 15, a hydroxide ion-conducting separator 16, and an electrolyte 18. Thus, the plurality of unit cells 10a constitute a multilayer battery as a whole. This is a structure of a so-called battery pack or laminated battery, which is advantageous in obtaining a high voltage and a large current.

[0043] The positive electrode plate 12 includes a positive electrode active material layer 12a. The positive electrode active material constituting the positive electrode active material layer 12a may be appropriately selected from known positive electrode materials according to the type of zinc secondary battery, and there is no particular limitation. For example, in the case of a nickel-zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. Or, in the case of a zinc-air secondary battery, an air electrode may be used as the positive electrode. The positive electrode plate 12 further includes a positive electrode current collector (not shown), and preferably, a metallic positive electrode current collecting member 13 extending from or connected to the positive electrode current collector (e.g., in the upward direction) is also provided. As a preferred example of the positive electrode current collector, a nickel-made porous substrate such as a foamed nickel plate can be cited. In this case, for example, by uniformly coating a paste containing an electrode active material such as nickel hydroxide on the nickel-made porous substrate and drying it, the positive electrode plate composed of the positive electrode / positive electrode current collector can be preferably manufactured. At this time, it is also preferable to perform a pressing treatment on the dried positive electrode plate (i.e., the positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. It should be noted that, Figure 4 The positive electrode plate 12 shown includes a positive electrode current collector (e.g., foamed nickel), but it is not shown. This is because, in the case of a nickel-zinc secondary battery, the positive electrode current collector is integrated with the positive electrode active material, and therefore, the positive electrode current collector cannot be separately depicted. The positive electrode current collecting member 13 may be made of the same material as the positive electrode current collector or a different material from it. In the case where the positive electrode current collector is a nickel-made porous substrate such as a foamed nickel plate, it can be processed into an ear-like shape by pressing it. In short, other current collecting members such as an ear lead can be connected to the ear-like part as described above to extend the positive electrode current collecting member 13. In short, it is preferable that a plurality of positive electrode current collecting members 13 are joined to one positive electrode terminal 26 or another positive electrode current collecting member 13 electrically connected to it. Typically, the positive electrode terminal 26 is connected to the positive electrode current collecting member 13 and protrudes from the battery container 20.

[0044] The positive electrode plate 12 may include an additive selected from at least one of a silver compound, a manganese compound, and a titanium compound, thereby promoting the positive electrode reaction that absorbs hydrogen generated by the self-discharge reaction. In addition, the positive electrode plate 12 may further include cobalt. Cobalt is preferably included in the positive electrode plate 12 in the form of cobalt oxyhydroxide. In the positive electrode plate 12, cobalt functions as a conductive aid, thereby contributing to the improvement of the charge-discharge capacity.

[0045] The negative electrode plate 14 includes a negative electrode active material layer 14a. The negative electrode active material constituting the negative electrode active material layer 14a includes at least one selected from zinc, zinc oxide, zinc alloy, and zinc compound. Regarding zinc, as long as it has electrochemically active properties suitable for the negative electrode, it can be included in any form of zinc metal, zinc compound, and zinc alloy. As a preferred example of the negative electrode material, zinc oxide, zinc metal, calcium zincate, etc. can be cited, but a mixture of zinc metal and zinc oxide is more preferred. The negative electrode active material can be configured in a gel form or mixed with the electrolyte 18 to form a negative electrode mixture. For example, by adding an electrolyte and a thickening agent to the negative electrode active material, a gelled negative electrode can be easily obtained. As an example of the thickening agent, polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc. can be cited, but polyacrylic acid is preferred because of its excellent chemical resistance to strong alkalis.

[0046] As the zinc alloy, a mercury-free and lead-free zinc alloy known as a mercury-free zinc alloy can be used. For example, a zinc alloy containing 0.01 to 0.1 mass% of indium, 0.005 to 0.02 mass% of bismuth, and 0.0035 to 0.015 mass% of aluminum has an effect of suppressing hydrogen generation, so it is preferred. In particular, indium and bismuth are advantageous in improving the discharge performance. The use of the zinc alloy in the negative electrode can suppress hydrogen generation and improve safety by slowing down the self-dissolution rate in the alkaline electrolyte.

[0047] The shape of the negative electrode material is not particularly limited, and it is preferably made into a powder form. Thus, the surface area is increased, and it can cope with high-current discharge. Regarding the average particle diameter of the preferred negative electrode material, in the case of a zinc alloy, it is in the range of 3 to 100 μm in the short diameter. If it is within this range, the surface area is large, so it is suitable for coping with high-current discharge, and it is easy to be uniformly mixed with the electrolyte and the gelling agent, and the processability during battery assembly is also good.

[0048] The negative electrode plate 14 further includes a negative electrode current collector 14b. Regarding the negative electrode current collector 14b, except for the portion extending as the negative electrode current collecting member 15, it is disposed inside and / or on the surface of the negative electrode active material layer 14a. That is, it may be a structure in which the negative electrode active material layer 14a is disposed on both sides of the negative electrode current collector 14b, or a structure in which the negative electrode active material layer 14a is disposed only on one side of the negative electrode current collector 14b. Further, it is preferable to provide a metal negative electrode current collecting member 15 extending from or connected to the negative electrode current collector 14b (e.g., in the upward direction). The negative electrode current collecting member 15 is preferably disposed at a position not overlapping with the positive electrode current collecting member 13. The negative electrode current collecting member 15 may be made of the same material as the negative electrode current collector 14b or a different material therefrom. In short, other current collecting members such as an ear lead may be connected to the above-mentioned tab to extend the negative electrode current collecting member 15. In short, it is preferable that a plurality of negative electrode current collecting members 15 are joined to one negative terminal 28 or another negative electrode current collecting member 15 electrically connected thereto. Typically, the negative terminal 28 is connected to the negative electrode current collecting member 15 and protrudes from the battery container 20.

[0049] From the viewpoint of the adhesion of the active material, it is preferable that the negative electrode current collector 14b uses a metal plate having a plurality (or a large number) of openings. As a preferable example of such a negative electrode current collector 14b, expanded metal, perforated metal, and wire mesh, and combinations thereof can be cited. More preferably, expanded copper, perforated copper, and combinations thereof can be cited, and particularly preferably expanded copper can be cited. In this case, for example, a mixture containing zinc oxide powder and / or zinc powder and, if necessary, a binder (e.g., polytetrafluoroethylene particles) can be coated on the expanded copper to preferably produce a negative electrode plate composed of a negative electrode / negative electrode current collector. At this time, it is also preferable to perform a pressing treatment on the dried negative electrode plate (i.e., negative electrode / negative electrode current collector) to prevent the electrode active material from falling off and to increase the electrode density. It should be noted that expanded metal refers to a mesh-like metal plate obtained by expanding a metal plate while forming slits in a staggered manner using an expansion manufacturing machine and forming the slits into a diamond shape or a tortoise shell shape. Perforated metal is also called perforated metal mesh and is obtained by punching holes in a metal plate. Wire mesh is a metal product having a wire mesh structure and is different from expanded metal and perforated metal.

[0050] The hydroxide ion conductive separator 16 is provided to isolate the positive electrode plate 12 and the negative electrode plate 14 in a manner that allows hydroxide ion conduction. For example, as Figure 4As shown, the negative electrode plate 14 can also be configured to be covered or wrapped by a hydroxide ion-conducting separator 16. Thus, it is not necessary to perform a complicated sealing joint between the hydroxide ion-conducting separator 16 and the battery container, and a zinc secondary battery (especially its laminated battery) capable of preventing the growth of zinc dendrites can be produced extremely simply and with high productivity. However, it may also be a simple structure in which the hydroxide ion-conducting separator 16 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14.

[0051] The hydroxide ion-conducting separator 16 is not particularly limited as long as it can isolate the positive electrode plate 12 and the negative electrode plate 14 in a manner that allows hydroxide ion conduction. Typically, it is a separator that contains a hydroxide ion-conducting solid electrolyte and selectively allows hydroxide ions to pass through by specifically utilizing the hydroxide ion conductivity. Preferred hydroxide ion-conducting solid electrolytes are layered double hydroxides (LDHs) and / or LDH-like compounds. Therefore, the hydroxide ion-conducting separator 16 is preferably an LDH separator. In this specification, an "LDH separator" is defined as a separator that contains LDH and / or LDH-like compounds and selectively allows hydroxide ions to pass through by specifically utilizing the hydroxide ion conductivity of the LDH and / or LDH-like compounds. In this specification, an "LDH-like compound" is a hydroxide and / or oxide having a layered crystal structure that may not be called an LDH but has hydroxide ion conductivity, and can be said to be equivalent to an LDH. However, as a broad definition, "LDH" can also be interpreted to include not only LDH but also LDH-like compounds. The LDH separator is preferably compounded with a porous substrate. Therefore, the LDH separator preferably further includes a porous substrate, and the LDH and / or LDH-like compounds are compounded with the porous substrate in a form filling the pores of the porous substrate. That is, the LDH and / or LDH-like compounds of the preferred LDH separator block the pores of the porous substrate in a manner that exhibits hydroxide ion conductivity and airtightness (and thus functions as an LDH separator exhibiting hydroxide ion conductivity). The porous substrate is preferably made of a polymer material, and the LDH and / or LDH-like compounds are particularly preferably introduced throughout the thickness direction of the polymer material porous substrate. For example, known LDH separators disclosed in Patent Documents 3 to 9 can be used. The thickness of the LDH separator is preferably 5 to 100 μm, more preferably 5 to 80 μm, further preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0052] As Figure 1 , Figure 2 and Figure 4As shown, preferably, the positive electrode plate 12, the positive electrode current collector member 13, the negative electrode plate 14, the negative electrode current collector member 15, and the hydroxide ion conductive separator 16 are arranged longitudinally, and the positive terminal 26 and the negative terminal 28 are provided on the upper lid 20a of the battery container 20. Therefore, in the case of a multi-layer battery, it is preferable that the batteries are multi-layered in the lateral direction. In addition, it is preferable that the positive electrode current collector member 13 and the negative electrode current collector member 15 extend upward.

[0053] The zinc secondary battery 10 may further include a liquid retention member 17 in contact with the positive electrode plate 12 and / or the negative electrode plate 14. For example, preferably, not only the hydroxide ion conductive separator 16 is interposed between the positive electrode plate 12 and the negative electrode plate 14, but also the liquid retention member 17 is interposed. And, as Figure 4 shown, it is preferable that the positive electrode plate 12 and / or the negative electrode plate 14 is covered or wrapped by the liquid retention member 17. However, it may also be a simple structure in which the liquid retention member 17 is arranged on one side of the positive electrode plate 12 or the negative electrode plate 14. In short, by interposing the liquid retention member 17, the electrolyte 18 can be made to exist throughout the space between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conductive separator 16, and the transfer of hydroxide ions between the positive electrode plate 12 and / or the negative electrode plate 14 and the hydroxide ion conductive separator 16 can be carried out efficiently. The liquid retention member 17 may be any member that can retain the electrolyte 18, and is not particularly limited. A sheet-like member is preferred. As a preferred example of the liquid retention member 17, non-woven fabric, water-absorbing resin, liquid-retaining resin, porous sheet, and various spacers can be cited. Considering the aspect of being able to produce a negative electrode structure with good performance at low cost, non-woven fabric is particularly preferred. The liquid retention member 17 or the non-woven fabric preferably has a thickness of 10 to 200 μm, more preferably 20 to 200 μm, further preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. If the thickness is within the above range, the overall size of the positive electrode structure and / or the negative electrode structure can be suppressed without waste and compactly, and a sufficient amount of the electrolyte 18 can be retained in the liquid retention member 17.

[0054] When the positive electrode plate 12 and / or the negative electrode plate 14 is covered or wrapped by the liquid retention member 17 and / or the hydroxide ion conductive separator 16, it is preferable that their outer edges (except for the sides where the positive electrode current collector member 13 and the negative electrode current collector member 15 extend) are closed. In this case, the closed edges of the outer edges of the liquid retention member 17 and / or the hydroxide ion conductive separator 16 are preferably achieved by bending the liquid retention member 17 and / or the hydroxide ion conductive separator 16 and by sealing the liquid retention members 17 with each other and / or the hydroxide ion conductive separators 16 with each other. As a preferred example of the sealing method, adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof can be cited. In particular, the LDH separator containing a porous substrate made of a polymer material has flexibility, and thus has the advantage of being easily bent. Therefore, it is preferable to form the LDH separator into a long strip shape and bend it to form a state where one side of the outer edge is closed. Heat welding and ultrasonic welding can be performed using commercially available heat sealers, etc. In the case of sealing the LDH separators with each other, from the aspect of being able to perform more effective sealing, it is preferable to perform heat welding and ultrasonic welding in such a way that the outer peripheral portion of the liquid retention member 17 is sandwiched between the LDH separators constituting the outer peripheral portion. On the other hand, adhesives, adhesive tapes, and sealing tapes can use commercially available products, but in order to prevent deterioration in the alkaline electrolyte, it is preferable to contain a resin having alkali resistance. From this viewpoint, as an example of a preferred adhesive, epoxy resin-based adhesives, natural resin-based adhesives, modified olefin resin-based adhesives, and modified silicone resin-based adhesives can be cited. Among them, from the aspect of particularly excellent alkali resistance, epoxy resin-based adhesives are more preferable. As a product example of the epoxy resin-based adhesive, epoxy adhesive Hysol (registered trademark) (manufactured by Henkel) can be cited.

[0055] Preferably, the outer edge of one side that is the upper end of the hydroxide ion-conducting separator 16 is open. This upper-open structure can address the problems during overcharging of nickel-zinc batteries and the like. That is, in nickel-zinc batteries and the like, if overcharged, oxygen (O2) may be generated at the positive electrode plate 12. However, the LDH separator has such a high density that it substantially allows only hydroxide ions to pass through, so O2 cannot pass through. In this regard, according to the upper-open structure, in the battery container 20, O2 can escape above the positive electrode plate 12 and be sent to the negative electrode plate 14 side via the upper open portion, whereby the Zn of the negative electrode active material can be oxidized by O2 and restored to ZnO. By going through such an oxygen reaction cycle, using the upper-open type electrode laminate 11 for a sealed zinc secondary battery can improve the overcharge resistance. It should be noted that even when the outer edge of one side that is the upper end of the hydroxide ion-conducting separator 16 and the liquid retention member 17 is closed, by providing vent holes in a part of the closed outer edge, the same effect as the above open structure can be expected. For example, vent holes can be opened after sealing the outer edge of one side that is the upper end of the LDH separator, or a part of the above outer edge can be unsealed in a way that forms vent holes during sealing.

[0056] The battery container 20 is preferably made of resin. The resin constituting the battery container 20 is preferably a resin resistant to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, an ABS resin, or a modified polyphenylene ether, and further preferably an ABS resin or a modified polyphenylene ether. The battery container 20 has an upper lid 20a. The battery container 20 (for example, the upper lid 20a) can have a pressure relief valve for releasing gas. In addition, a container group in which two or more battery containers 20 are arranged can be housed in an outer frame as a battery module structure.

[0057] Examples The present invention will be further specifically described by the following examples.

[0058] Examples 1 to 9 (1) Fabrication of nickel-zinc secondary battery Prepare the following positive electrode plate, positive electrode current collector member, negative electrode plate, negative electrode current collector member, LDH separator, non-woven fabric, battery container, and electrolyte. At this time, prepare various electrolytes with different types and concentrations of alkali metal hydroxides.

[0059] · Positive electrode plate: Prepared by filling a positive electrode paste containing nickel hydroxide and a binder into the pores of foamed nickel and drying it (there is an uncoated portion near one end of the foamed nickel where the positive electrode paste is not coated).

[0060] · Positive current collector member: The uncoated portion of the foamed nickel constituting the positive electrode plate is compressed by a roll press to process it into a tab, and a tab lead wire (made of pure nickel, thickness: 100 μm) is ultrasonically welded to the tab to extend it.

[0061] · Negative electrode plate: A negative electrode paste containing ZnO powder, metallic Zn powder, polytetrafluoroethylene (PTFE), and propylene glycol is pressed onto a current collector (copper expanded metal) (an uncoated portion where the negative electrode paste is not coated exists near one end of the copper expanded metal).

[0062] · Negative current collector member: A tab lead wire (made of copper, thickness: 100 μm) is connected by ultrasonic welding to the uncoated portion of the copper expanded metal.

[0063] · LDH separator: Ni - Al - Ti - LDH (layered double hydroxide) is precipitated in the pores and on the surface of a polyethylene microporous membrane by hydrothermal synthesis and then roll - pressed, thickness: 20 μm · Non - woven fabric: Made of polypropylene, thickness 100 μm · Battery container: A box - shaped housing made of modified polyphenylene ether resin (equipped with a pressure - relief valve capable of releasing the gas generated inside the housing), internal dimensions: length 190 mm, width 24 mm, height 165 mm, external dimensions: length 200 mm, width 30 mm, height 170 mm (excluding the height of the positive terminal and the negative terminal) · Electrolyte: 0.4 mol / L of ZnO is dissolved in an aqueous solution of alkali metal hydroxide with the composition shown in Table 1.

[0064] The positive electrode plate is wrapped with non - woven fabric in a manner that covers it from both sides, and the non - woven fabric slightly protrudes from the remaining three sides except for the side extending from the positive current collector member. The remaining portion of the non - woven fabric protruding from the three sides of the positive electrode plate is heat - sealed and melted by a heat - sealing bar to obtain a positive electrode structure. In addition, the negative electrode plate is sequentially wrapped with non - woven fabric and an LDH separator from both sides, and the non - woven fabric and the LDH separator slightly protrude from the remaining three sides except for the side extending from the negative current collector member. The remaining portion of the non - woven fabric and the LDH separator protruding from the three sides of the negative electrode plate is heat - sealed and melted by a heat - sealing bar to obtain a negative electrode structure. In this way, multiple positive electrode structures and multiple negative electrode structures are prepared.

[0065] Twelve positive electrode structures and thirteen negative electrode structures are alternately stacked to fabricate an electrode laminate. Figure 3Similarly, in the structure shown, the multiple positive current collector members 13 and the multiple negative current collector members 15 are designed to extend from different positions with respect to the electrode current collector in a plan view. Therefore, the multiple positive current collector members 13 overlap each other, while on the other hand, the multiple negative current collector members 15 overlap each other at different positions. As Figure 1 and Figure 2 shown, the overlapping portions of the multiple positive current collector members 13 are gathered and joined to the positive terminal 26 by laser welding. Similarly, the overlapping portions of the multiple negative current collector members 15 are gathered and joined to the negative terminal 28 by laser welding. In this way, a stack of electrode structures including the positive current collector member 13 and the negative current collector member 15 is obtained as the electrode laminate 11. The electrode laminate 11 is placed in a box-shaped battery container 20, the electrolyte 18 is injected and impregnated into the electrode laminate 11, and the upper lid 20a is closed for sealing. Thus, a nickel-zinc secondary battery is fabricated.

[0066] (2) Evaluation of battery resistance Using a charge-discharge device (manufactured by TOYO SYSTEM Co., Ltd., TOSCAT3100), chemical conversion was performed on the fabricated nickel-zinc secondary battery with 0.1C charge and 0.2C discharge. Then, one 0.5C charge-discharge cycle was performed, and the value obtained by dividing the discharge capacity by the charge capacity and multiplying by 100 (= (discharge capacity / charge capacity) × 100) was used to calculate the Coulomb efficiency value. The obtained Coulomb efficiency value was evaluated and classified according to the following criteria. The results are shown in Table 1. It should be noted that it is speculated that for the sample with an evaluated battery resistance of C, the discharge reaction was not completed due to the high resistance of the electrolyte, resulting in a deterioration of the Coulomb efficiency.

[0067] <Battery resistance evaluation criteria> - Evaluation A: The Coulomb efficiency value is 99% or more - Evaluation B: The Coulomb efficiency value exceeds 95% and is less than 99% - Evaluation C: The Coulomb efficiency value is 95% or less (failed) (3) Evaluation of leakage resistance The fabricated nickel-zinc secondary battery was stored in a high-temperature and high-humidity (65°C / 80%) environment. The number of days from the start of storage until carbonate from the electrolyte was visually observed for the first time on the upper part of the negative terminal 28 was measured. The number of days until salt precipitation was evaluated and classified according to the following criteria. The results are shown in Table 1.

[0068] <Leakage resistance evaluation criteria> - Evaluation A: The number of days until salt precipitation is 50 days or more - Evaluation B: The number of days until salt precipitation is 11 - 49 days - Evaluation C: The number of days until salt precipitation is 10 days or less (failed) [Table 1]

[0069] * indicates a comparative example.

Claims

1. A secondary zinc battery, comprising: A positive electrode plate, which includes a positive electrode active material layer and a positive electrode current collector; A negative electrode plate, which includes a negative electrode active material layer and a negative electrode current collector, and the negative electrode active material layer includes at least one selected from zinc, zinc oxide, zinc alloy, and zinc compound; A hydroxide ion conductive separator, which separates the positive electrode plate and the negative electrode plate in a manner capable of hydroxide ion conduction; and An electrolyte solution, The electrolyte solution is an aqueous solution containing an alkali metal hydroxide, and the alkali metal hydroxide at least includes sodium hydroxide, The total concentration of the alkali metal hydroxide in the electrolyte solution is 5.0 to 6.0 mol / L, and the concentration of sodium hydroxide in the electrolyte solution is 0.5 to 6.0 mol / L.

2. The zinc secondary battery according to claim 1, wherein, The concentration of sodium hydroxide in the electrolyte solution is 2.5 to 6.0 mol / L.

3. The zinc secondary battery according to claim 1 or 2, wherein, The ratio of the concentration of sodium hydroxide to the total concentration of the alkali metal hydroxide is 0.4 to 1.

0.

4. The zinc secondary battery according to claim 1 or 2, wherein The alkali metal hydroxide only includes the sodium hydroxide.

5. The zinc secondary battery according to claim 1 or 2, wherein The alkali metal hydroxide further includes potassium hydroxide.

6. The zinc secondary battery according to claim 5, wherein, The concentration of potassium hydroxide in the electrolyte solution is 3.0 mol / L or less.

7. The zinc secondary battery according to claim 5, wherein, The alkali metal hydroxide further includes lithium hydroxide.

8. The zinc secondary battery according to claim 7, wherein, The concentration of lithium hydroxide in the electrolyte solution is 1.5 mol / L or less.

9. The zinc secondary battery according to claim 1 or 2, wherein The hydroxide ion conductive separator is an LDH separator, and the LDH separator includes a layered double hydroxide, i.e., LDH, and / or a LDH-like compound.

10. The zinc secondary battery according to claim 9, wherein, The LDH separator further includes a porous substrate, and the LDH and / or the LDH-like compound is compounded with the porous substrate in a form of filling the pores of the porous substrate.

11. The zinc secondary battery according to claim 10, wherein, The porous substrate is made of a polymer material.

12. The zinc secondary battery according to claim 1 or 2, wherein, The positive electrode active material layer includes nickel hydroxide and / or nickel oxyhydroxide, whereby the secondary zinc battery constitutes a nickel-zinc secondary battery.

13. The zinc secondary battery according to claim 1 or 2, wherein The positive electrode active material layer is an air electrode layer, whereby the secondary zinc battery constitutes a zinc-air secondary battery.

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