Batteries using a layered double hydroxide compound

Abstract

Provided is a battery that is excellent in alkali resistance and high in reliability, and in which deterioration of a layered double hydroxide-like (LDH-like) compound contained in the battery is significantly reduced. The battery includes a positive electrode, a negative electrode, an aqueous alkali metal hydroxide solution, i.e., an electrolyte, and an LDH-like compound disposed so as to be in contact with the electrolyte. The battery is configured so that a metal compound containing at least one metal element that constitutes the LDH-like compound is dissolved in the electrolyte, thereby suppressing corrosion of the LDH-like compound by the electrolyte.

Description

Technical Field

[0001] This invention relates to batteries that use layered double hydroxide (LDH) compounds. Background Technology

[0002] It is known that in zinc secondary batteries such as nickel-zinc batteries and zinc-air batteries, during charging, metallic zinc precipitates out in a dendritic form from the negative electrode, penetrating the gaps in the non-woven fabric separator and reaching the positive electrode, resulting in a short circuit. Repeated occurrences of such short circuits caused by zinc dendrites lead to a shortened charge-discharge lifespan.

[0003] To address the aforementioned problems, batteries incorporating layered double hydroxide (LDH) separators have been proposed, which selectively allow hydroxide ions to permeate while preventing zinc dendrites from penetrating. For example, Patent Document 1 (International Publication No. 2013 / 118561) discloses the placement of an LDH separator between the positive and negative electrodes in a nickel-zinc secondary battery. Furthermore, Patent Document 2 (International Publication No. 2016 / 076047) discloses a separator structure comprising an LDH separator fitted or bonded to a resin frame, and discloses that the LDH separator possesses high density, exhibiting a degree of air and / or water impermeability. This document also discloses that the LDH separator can be composited with a porous substrate. Additionally, Patent Document 3 (International Publication No. 2016 / 067884) discloses various methods for forming a dense LDH film on the surface of a porous substrate to obtain a composite material (LDH separator). The method includes the following steps: uniformly attaching a starting material that can provide the crystal growth starting point for LDH to a porous substrate; and performing hydrothermal treatment on the porous substrate in a raw material aqueous solution to form a dense LDH film on the surface of the porous substrate.

[0004] As an example of an application other than zinc secondary batteries with hydroxide ion-conducting ceramic separators, Patent Document 4 (International Publication No. 2013 / 161516) discloses a lithium-air secondary battery using an LDH-containing solid electrolyte as an anion exchanger, which is composed of LDH with the same basic composition as described above. This anion exchanger can prevent carbon dioxide from entering the battery. In addition, Patent Document 5 (International Publication No. 2014 / 119665) reports the following insight: if a film containing LDH such as hydrotalcite and polymers such as polytetrafluoroethylene is formed on an electrode containing a zinc compound and current flows through it, the morphological changes of the active material of the zinc electrode are suppressed, and it describes the use of anion-conducting materials that may contain LDH and polymers in battery components such as separators, electrolytes, and electrode protectants.

[0005] However, in the numerous alkaline secondary batteries mentioned above, potassium hydroxide (KOH) aqueous solution is used as the electrolyte, and improvements have been proposed. For example, Patent Document 6 (Japanese Patent Publication No. 2001-500661) discloses an alkaline battery in which the electrolyte in contact with the zinc negative electrode is composed of a KOH aqueous solution with 70-100g of dissolved aluminum at an initial concentration of 4-8M, thereby limiting the solubility of zinc in the electrolyte by adding aluminum. It should be noted that the ion exchange membrane used in the embodiments of this document is a hydrocarbon-based ion exchange membrane, rather than a ceramic separator.

[0006] On the other hand, Patent Document 7 (International Publication No. 2016 / 051934) discloses a battery that includes a positive electrode, a negative electrode, an aqueous solution of an alkali metal hydroxide, i.e., an electrolyte, and a device configured to contact the electrolyte and having an M... 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (where M) 2+ M is a divalent cation. 3+ A is a trivalent cation. n- LDH is a basic building block of anions with an n-valent charge (where n is an integer greater than or equal to 1, x is between 0.1 and 0.4, and m is any real number), which consists of anions with an n-valent charge (where n is an integer greater than or equal to 1, x is between 0.1 and 0.4, and m is any real number). 2+ and / or M 3+ The corresponding metal compound dissolves in the electrolyte, thereby inhibiting the corrosion of the layered hydroxide by the electrolyte.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2013 / 118561

[0010] Patent Document 2: International Publication No. 2016 / 076047

[0011] Patent Document 3: International Publication No. 2016 / 067884

[0012] Patent Document 4: International Publication No. 2013 / 161516

[0013] Patent Document 5: International Publication No. 2014 / 119665

[0014] Patent Document 6: Japanese Patent Publication No. 2001-500661

[0015] Patent Document 7: International Publication No. 2016 / 051934 Summary of the Invention

[0016] The applicant has pioneered the development of a highly densified LDH separator (layered double hydroxide separator) that exhibits hydroxide ion conductivity but lacks water permeability and aeration. When using such a separator (or a separator with a porous substrate) in secondary batteries such as zinc-nickel batteries and zinc-air batteries, it is possible to prevent short circuits caused by zinc dendrites and the ingress of carbon dioxide (a problem particularly prevalent in metal-air batteries). Furthermore, to maintain this effect over a long period, it is desirable to suppress the degradation of the LDH separator. In addition, not limited to LDH separators, it is also desirable to suppress the degradation of LDH when incorporating separators that combine LDH with other materials (e.g., polymers) or other LDH-containing components other than LDH into the battery. However, for electrolytes used in batteries employing LDH (e.g., metal-air batteries, nickel-zinc batteries), high hydroxide ion conductivity is required; therefore, a strongly alkaline KOH aqueous solution with a pH of approximately 14 is desirable. Therefore, for LDH, a high degree of alkali resistance, with minimal degradation in such a strongly alkaline electrolyte, is desirable.

[0017] The inventors have obtained the following insights: Instead of conventional LDH, using hydroxides and / or oxides with a specified layered crystalline structure, i.e., layered double hydroxide (LDH-like) compounds, as hydroxide ion-conducting materials enables excellent alkali resistance. Furthermore, they have obtained the following insights: By intentionally dissolving a specified metal compound in an alkaline electrolyte beforehand, the degradation of LDH-like compounds contained in the battery caused by the alkaline electrolyte can be significantly reduced. Moreover, they have obtained the following insights: Using this electrolyte significantly reduces the degradation of LDH-like compounds caused by the alkaline electrolyte, providing a highly reliable battery.

[0018] Therefore, the purpose of this invention is to provide a battery with excellent alkali resistance and high reliability, which can significantly reduce the degradation of LDH-like compounds contained in the battery.

[0019] According to one aspect of the present invention, a battery is provided that uses a layered double hydroxide (LDH)-like compound, comprising a positive electrode, a negative electrode, an aqueous solution of an alkali metal hydroxide, i.e., an electrolyte, and an LDH-like compound configured to contact the electrolyte.

[0020] The configuration is as follows: a metal compound containing at least one metal element constituting the LDH-like compound is dissolved in the electrolyte, thereby inhibiting the LDH-like compound from being eroded by the electrolyte.

[0021] According to a preferred embodiment of the invention, the battery includes the LDH-like compound as a separator with hydroxide ion conductivity, which can separate the positive electrode and the negative electrode.

[0022] According to a more preferred embodiment of the invention, the positive electrode comprises nickel hydroxide and / or nickel hydroxyl oxide.

[0023] The electrolyte is composed of a positive electrode electrolyte impregnating the positive electrode and a negative electrode electrolyte impregnating the negative electrode.

[0024] The battery includes a container for containing the positive electrode, the positive electrode electrolyte, the negative electrode, and the negative electrode electrolyte.

[0025] The separator is configured to divide the container into a positive electrode chamber for containing the positive electrode and the positive electrode electrolyte, and a negative electrode chamber for containing the negative electrode and the negative electrode electrolyte, thereby making the battery a nickel-zinc secondary battery.

[0026] According to a more preferred embodiment of the invention, the positive electrode is the air electrode.

[0027] The negative electrode is immersed in the electrolyte.

[0028] The battery includes a container for containing the negative electrode and the electrolyte, the container having an opening.

[0029] The separator seals the opening in a manner that allows it to contact the electrolyte, thus forming a closed space on the negative electrode side with the container. This separates the air electrode from the electrolyte in a manner that allows hydroxide ion conduction, thereby making the battery a zinc-air secondary battery. Attached Figure Description

[0030] Figure 1 This is a conceptual diagram illustrating an example of a nickel-zinc battery according to one aspect of the present invention, showing the end-of-discharge state.

[0031] Figure 2 It is shown Figure 1 The diagram shows a nickel-zinc battery in its fully charged state.

[0032] Figure 3A This is a conceptual diagram illustrating an example of a zinc-air secondary battery according to one aspect of the present invention.

[0033] Figure 3B yes Figure 3A The diagram shows a three-dimensional representation of a zinc-air secondary battery.

[0034] Figure 4 The image is a SEM image obtained by observing the microstructure of the LDH compact body in Example A2 before it was immersed in KOH aqueous solution.

[0035] Figure 5 The image is a SEM image obtained by observing the microstructure of the LDH compact body in Example A2 after being immersed in a KOH aqueous solution with an Al concentration of 0.7 mol / L at 30°C for one week.

[0036] Figure 6 The image is a SEM image obtained by observing the microstructure of the LDH compact body in Example A2 after being immersed in a KOH aqueous solution with an Al concentration of 0.7 mol / L at 70°C for one week.

[0037] Figure 7 The image is a SEM image obtained by observing the microstructure of the LDH compact body in Example A2 after being immersed in a KOH aqueous solution with an Al concentration of 0 mol / L at 30°C for one week.

[0038] Figure 8 This is a SEM image of the surface of the porous alumina substrate fabricated in Example A3.

[0039] Figure 9 The XRD pattern obtained for the crystal phase of the sample in Example A3 is shown below.

[0040] Figure 10 This is a SEM image of the surface microstructure of the membrane sample observed in Example A3.

[0041] Figure 11 This is a SEM image of the microstructure of the ground cross section of the composite material specimen observed in Example A3.

[0042] Figure 12A This is an exploded stereo diagram of the compactness discrimination test system used in Example A3.

[0043] Figure 12B This is a schematic cross-sectional view of the compactness discrimination test system used in Example A3.

[0044] Figure 13A This is an exploded perspective view of the sealed container used in the tightness determination test II of Example A3.

[0045] Figure 13B This is a schematic cross-sectional view of the test system used in the compactness determination test II of Example A3.

[0046] Figure 14A This is a conceptual diagram illustrating one example of the He transmittance measurement system used in Examples B1 to D2.

[0047] Figure 14B yes Figure 14A The diagram shows a schematic cross-sectional view of the sample holder and its surrounding area used in the measurement system.

[0048] Figure 15This is a schematic cross-sectional view showing the electrochemical measurement system used in Examples B1 to B5.

[0049] Figure 16A This is a surface SEM image of the LDH-like compound separator fabricated in Example B1.

[0050] Figure 16B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B1.

[0051] Figure 17A This is a surface SEM image of the LDH-like compound separator fabricated in Example B2.

[0052] Figure 17B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B2.

[0053] Figure 18A This is a surface SEM image of the LDH-like compound separator fabricated in Example B3.

[0054] Figure 18B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B3.

[0055] Figure 19A This is a surface SEM image of the LDH-like compound separator fabricated in Example B4.

[0056] Figure 19B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B4.

[0057] Figure 20A This is a surface SEM image of the LDH-like compound separator fabricated in Example B5.

[0058] Figure 20B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B5.

[0059] Figure 21A This is a surface SEM image of the LDH-like compound separator fabricated in Example B6.

[0060] Figure 21B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B6.

[0061] Figure 22 This is a surface SEM image of the LDH-like compound separator fabricated in Example B7.

[0062] Figure 23A This is a surface SEM image of the LDH partition fabricated in Example B8 (Comparison).

[0063] Figure 23BThe X-ray diffraction results are for the LDH partition fabricated in Example B8 (Comparison).

[0064] Figure 24 This is a surface SEM image of the LDH-like compound separator fabricated in Example C1.

[0065] Figure 25 This is a surface SEM image of the LDH-like compound separator fabricated in Example D1.

[0066] Figure 26 This is a surface SEM image of the LDH-like compound separator fabricated in Example D2. Detailed Implementation

[0067] Battery

[0068] The battery of the present invention utilizes a layered double hydroxide (LDH-like) compound. It should be noted that, in this specification, "LDH-like compound" refers to hydroxides and / or oxides with a similar layered crystalline structure to LDH, and is defined as a compound from which no peaks originating from LDH can be detected by X-ray diffraction. As long as the LDH-like compound is included as a component of the battery, its location and form are not limited, as long as it is disposed in a position that can contact the electrolyte. Preferred examples of components containing the LDH-like compound include separators, electrolytes, and electrode protectants (e.g., negative electrode protectants). These components can utilize the desired properties of the LDH-like compound, such as hydroxide ion conductivity, thereby improving battery performance. Separators are particularly preferred. In this case, the separator can be composed of an elemental LDH-like compound or a composite separator containing the LDH-like compound and other materials (e.g., polymers). Furthermore, it is preferable that the electrode, such as the negative electrode (e.g., a negative electrode containing zinc and / or zinc oxide), is coated with an LDH-like compound. In summary, LDH-like compounds can be used in various battery components, where they can be used in elemental form or in combination with other materials (e.g., polymers). It should be noted that the battery can be either a primary battery or a secondary battery, but is preferably a secondary battery, such as a nickel-zinc secondary battery, a silver-zinc oxide secondary battery, a manganese-zinc oxide secondary battery, a zinc-air secondary battery, and various other alkaline zinc secondary batteries, as well as a lithium-air secondary battery, etc., all of which are suitable for LDH-like compounds. In particular, nickel-zinc secondary batteries and zinc-air secondary batteries are preferred. Therefore, in the following general description, references to nickel-zinc secondary batteries are sometimes made. Figure 1 Figure 3 and related zinc-air secondary batteries Figure 3BHowever, the batteries of the present invention should not be limited to nickel-zinc secondary batteries and zinc-air secondary batteries, but conceptually include the various batteries described above that can employ LDH-like compounds.

[0069] One aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a layered double hydroxide (LDH-like) compound. The separator is configured to contact the electrolyte and separate the positive and negative electrodes, as needed. The LDH-like compound is configured to contact the electrolyte and, as described above, can be a separator or other battery component. Furthermore, the electrolyte is an aqueous solution of an alkali metal hydroxide (KOH). That is, as described above, for the electrolyte of batteries using LDH-like compounds (e.g., metal-air batteries, nickel-zinc batteries), high hydroxide ion conductivity is required, therefore a strongly alkaline KOH aqueous solution with a pH of approximately 14 is desirable. Therefore, for LDH-like compounds, it is desirable that such high alkali resistance is hardly degraded in such a strongly alkaline electrolyte. Regarding this, the inventors have realized that by using a hydroxide and / or oxide with a defined layered crystalline structure, i.e., a layered double hydroxide (LDH-like) compound, as the hydroxide ion conductor instead of conventional LDH, excellent alkali resistance can be achieved. Furthermore, it has been observed that intentionally dissolving a specified metal compound in an alkaline electrolyte beforehand can significantly reduce the degradation of LDH-like compounds caused by the alkaline electrolyte. Specifically, the battery of the present invention is constructed by dissolving a metal compound containing at least one metal element constituting the LDH-like compound in the electrolyte, thereby inhibiting the corrosion of the LDH-like compound by the electrolyte. In particular, by inhibiting the corrosion of the LDH-like compound by the electrolyte, the excellent hydroxide ion conductivity inherent in the LDH-like compound and the excellent compactness of the LDH-like compound-containing components can be maintained as desired for a long period. In other words, according to the present invention, a secondary battery that significantly reduces the degradation of the LDH-like compound contained in the battery caused by the alkaline electrolyte, exhibits excellent alkali resistance, and high reliability can be provided.

[0070] Preferably, the LDH-like compound is one of (a), (b), or (c) below.

[0071] (a) A layered crystalline hydroxide and / or oxide containing Mg and at least one element selected from the group consisting of Ti, Y and Al, that contains at least Ti.

[0072] (b) comprising (i) Ti, Y, and Al and / or Mg as desired, and (ii) at least one hydroxide and / or oxide of a layered crystalline structure selected from the group consisting of In, Bi, Ca, Sr and Ba, i.e., with added element M.

[0073] (c) A layered crystalline hydroxide and / or oxide comprising Mg, Ti, Y, and Al and / or In as desired, wherein the LDH-like compound exists in the form of a mixture with In(OH)3.

[0074] According to a preferred embodiment (a) of the invention, the LDH-like compound can be a layered crystalline hydroxide and / or oxide containing Mg and at least one element selected from the group consisting of Ti, Y, and Al. Therefore, a typical LDH-like compound is a complex hydroxide and / or complex oxide of Mg, Ti, Y (if desired), and Al (if desired). The aforementioned elements can be replaced by other elements or ions to the extent that they do not impair the fundamental properties of the LDH-like compound; however, the LDH-like compound preferably does not contain Ni. For example, the LDH-like compound may further contain Zn and / or K. Accordingly, the ionic conductivity of the LDH-like compound can be further improved.

[0075] LDH-like compounds can be identified using X-ray diffraction. Specifically, when the surface of an LDH-like compound is subjected to X-ray diffraction, peaks originating from the LDH-like compound are typically detected in the range of 5° ≤ 2θ ≤ 10°, and more typically in the range of 7° ≤ 2θ ≤ 10°. It is well known that LDH is a substance having an alternating layered structure with exchangeable anions and H2O as intermediate layers between stacked hydroxide base layers. In this regard, when LDH is determined by X-ray diffraction, peaks originating from the crystalline structure of LDH (i.e., the (003) peak of LDH) are typically detected at a position of 2θ = 11° to 12°. In contrast, when LDH-like compounds are determined by X-ray diffraction, peaks are typically detected in the range of the aforementioned range, which is shifted to a lower angle than the aforementioned peak position of LDH. Furthermore, using 2θ corresponding to the peaks originating from the LDH-like compound in X-ray diffraction, the interlayer distance of the layered crystalline structure can be determined according to the Bragg formula. The interlayer distances of the layered crystal structures that constitute LDH-like compounds are typically 0.883–1.8 nm, and more typically 0.883–1.3 nm.

[0076] Regarding the LDH-like compound of method (a) above, the atomic ratio of Mg / (Mg+Ti+Y+Al) in the LDH-like compound, determined by energy dispersive X-ray diffraction (EDS), is preferably 0.03 to 0.25, more preferably 0.05 to 0.2. Furthermore, the atomic ratio of Ti / (Mg+Ti+Y+Al) in the LDH-like compound is preferably 0.40 to 0.97, more preferably 0.47 to 0.94. Additionally, the atomic ratio of Y / (Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.45, more preferably 0 to 0.37. Moreover, the atomic ratio of Al / (Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.03. Within these ranges, the alkali resistance is superior, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite tolerance) can be achieved more effectively. However, the basic composition of conventionally known LDH can be expressed by the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (where M) 2+ M is a divalent cation. 3+ A is a trivalent cation. n- The term "anion with an n-valence, where n is an integer greater than or equal to 1, x is 0.1 to 0.4, and m is 0 or greater" is used. In contrast, the atomic ratios in LDH-like compounds generally deviate from the general formula for LDH. Therefore, it can be said that LDH-like compounds in this method generally have different compositional ratios (atomic ratios) than conventional LDH. It should be noted that the EDS analysis is preferably performed as follows: using an EDS analysis device (e.g., X-act, manufactured by Oxford Instruments), 1) images are acquired at an accelerating voltage of 20 kV and a magnification of 5,000x; 2) in point analysis mode, with intervals of approximately 5 μm, three-point analysis is performed; 3) steps 1) and 2) are repeated once more; 4) the average value of the six points is calculated.

[0077] According to another preferred embodiment (b) of the invention, the LDH-like compound can be a layered crystalline hydroxide and / or oxide comprising (i) Ti, Y, and, depending on the desired inclusion of Al and / or Mg, and (ii) an additive element M. Thus, a typical LDH-like compound is a complex hydroxide and / or complex oxide comprising Ti, Y, an additive element M, and, depending on the desired inclusion of Al and Mg. The additive element M is In, Bi, Ca, Sr, Ba, or a combination thereof. The aforementioned elements can be substituted by other elements or ions to the extent that they do not impair the essential properties of the LDH-like compound; however, the LDH-like compound preferably does not contain Ni.

[0078] Regarding the LDH-like compound of method (b) above, the atomic ratio of Ti / (Mg+Al+Ti+Y+M) in the LDH-like compound, as determined by energy dispersive X-ray diffraction (EDS), is preferably 0.50 to 0.85, more preferably 0.56 to 0.81. The atomic ratio of Y / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.20, more preferably 0.07 to 0.15. The atomic ratio of M / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0.03 to 0.35, more preferably 0.03 to 0.32. The atomic ratio of Mg / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.10, more preferably 0 to 0.02. Furthermore, the atomic ratio of Al / (Mg+Al+Ti+Y+M) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.04. Within the aforementioned range, alkali resistance is even better, and it can more effectively suppress short circuits caused by zinc dendrites (i.e., dendrite tolerance). However, the basic composition of previously known LDH can be expressed by the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (where M) 2+ M is a divalent cation. 3+ A is a trivalent cation. n- The term "anion with an n-valence, where n is an integer greater than or equal to 1, x is 0.1 to 0.4, and m is 0 or greater" is used. In contrast, the atomic ratios in LDH-like compounds generally deviate from the general formula for LDH. Therefore, it can be said that LDH-like compounds in this method generally have different compositional ratios (atomic ratios) than conventional LDH. It should be noted that the EDS analysis is preferably performed as follows: using an EDS analysis device (e.g., X-act, manufactured by Oxford Instruments), 1) images are acquired at an accelerating voltage of 20 kV and a magnification of 5,000x; 2) in point analysis mode, with intervals of approximately 5 μm, three-point analysis is performed; 3) steps 1) and 2) are repeated once more; 4) the average value of the six points is calculated.

[0079] According to another preferred embodiment (c) of the invention, the LDH-like compound can be a layered crystalline hydroxide and / or oxide containing Mg, Ti, Y, and, as desired, Al and / or In, and the LDH-like compound exists in the form of a mixture with In(OH)3. The LDH-like compound of this embodiment is a layered crystalline hydroxide and / or oxide containing Mg, Ti, Y, and, as desired, Al and / or In. Therefore, a typical LDH-like compound is a complex hydroxide and / or complex oxide of Mg, Ti, Y, and, as desired, Al, and, as desired, In. It should be noted that the In that may be contained in the LDH-like compound can be intentionally added to the LDH-like compound, or it can be unavoidably mixed into the LDH-like compound due to the formation of In(OH)3, etc. The above-mentioned elements can be replaced by other elements or ions to the extent that they do not impair the basic characteristics of the LDH-like compound; however, the LDH-like compound preferably does not contain Ni. However, the basic composition of LDH known in the past can be expressed by the general formula: M 2+ 1-x M 3+ x (OH)2A n- x / n ·mH2O (where M) 2+ M is a divalent cation. 3+ A is a trivalent cation. n- (where n is an n-valent anion, n is an integer greater than or equal to 1, x is 0.1 to 0.4, and m is 0 or greater). In contrast, the atomic ratios in LDH-like compounds generally deviate from the general formula for LDH described above. Therefore, it can be said that LDH-like compounds in this manner generally have different compositional ratios (atomic ratios) than conventional LDHs.

[0080] The mixture in method (c) above contains not only an LDH-like compound but also In(OH)3 (typically composed of an LDH-like compound and In(OH)3). The presence of In(OH)3 effectively improves the alkali resistance and dendrite resistance of the LDH-like compound and the separator using it. The preferred proportion of In(OH)3 in the mixture is one that improves the alkali resistance and dendrite resistance with minimal impairment of the hydroxide ion conductivity of the LDH-like compound and the separator using it, but this is not particularly limited. In(OH)3 can have a cubic crystalline structure or be composed of In(OH)3 crystals surrounded by an LDH-like compound. In(OH)3 can be identified using X-ray diffraction. X-ray diffraction measurements can preferably be performed in the order given in the examples described later.

[0081] As described above, LDH-like compounds can be combined with other materials for use in battery components. Examples of such other materials include polymers, zinc-containing compounds, alumina, silicon dioxide, conductive carbon, and conductive ceramics, with polymers being particularly preferred. In addition, examples of polymers include polymers containing hydrocarbon groups such as polyethylene and polypropylene; polymers containing aromatic groups such as polystyrene; ether-containing polymers such as alkylene glycols; hydroxyl-containing polymers such as polyvinyl alcohol and poly(α-hydroxymethyl acrylate); polymers containing amide bonds such as polyamide, nylon, polyacrylamide, polyvinylpyrrolidone, and N-substituted polyacrylamide; polymers containing imide bonds such as polymaleimide; carboxyl-containing polymers such as poly(meth)acrylic acid, polymaleic acid, polyitacrylic acid, and polymethylglutaric acid; carboxyl-containing polymers such as poly(meth)acrylate, polymaleate, polyitacrylic acid, and polymethylglutaric acid; and polyvinyl chloride, polyvinylidene fluoride, etc. Halogen-containing polymers such as polytetrafluoroethylene; polymers bonded by ring-opening of epoxy groups such as epoxy resins; polymers containing sulfonate sites; polymers containing quaternary ammonium salts and quaternary phosphonium salts; ion-exchange polymers used in cation / anion exchange membranes; natural rubber; synthetic rubbers such as styrene-butadiene rubber (SBR); sugars such as cellulose, cellulose acetate, hydroxyalkyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, chitin, chitosan, and alginate (salt); amino-containing polymers such as polyethyleneimine; polymers containing urethane groups; polymers containing urea groups; polymers containing epoxy groups; polymers containing heterocyclic and / or ionized heterocyclic sites; polymer alloys; polymers containing heteroatoms; low molecular weight surfactants, etc.

[0082] The electrolyte can be any aqueous solution of an alkali metal hydroxide; any alkaline electrolyte suitable for use in batteries can be used. For example... Figure 1 As shown, when a positive electrode electrolyte 14 and a negative electrode electrolyte 18 are present, an aqueous solution of an alkali metal hydroxide is preferably used as both the positive electrode electrolyte 14 and the negative electrode electrolyte 18. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being more preferred. In the case of a zinc secondary battery, zinc compounds such as zinc oxide and zinc hydroxide can be added to the electrolyte to suppress the self-dissolution of the zinc alloy. As described above, the alkaline electrolyte can be mixed with the positive and / or negative electrodes to exist as a positive electrode mixture and / or a negative electrode mixture. In addition, to prevent electrolyte leakage, the electrolyte can be gelled. As a gelling agent, a polymer that swells by absorbing the solvent of the electrolyte is preferred, such as polymers like polyethylene oxide, polyvinyl alcohol, and polyacrylamide, or starch.

[0083] As described above, a metal compound comprising at least one metal element constituting an LDH-like compound is dissolved in the electrolyte. The metal compound is intentionally dissolved in the electrolyte, preferably pre-dissolved, for example, during battery manufacturing or before battery use. However, the metal compound can also be configured to dissolve in the electrolyte afterward (e.g., during battery use), in which case it can be configured to dissolve slowly as the battery is used. The metal element only needs to be dissolved in the electrolyte in some form; typically, it can be dissolved in the electrolyte as a metal ion, hydroxide, and / or hydroxyl complex. For example, Al can be cited as a form in which Al is dissolved. 3+ Al(OH) 2+ Al(OH)2 + Al(OH)3 0 Al(OH)4 - Al(OH)5 2- In the case of LDH-like compounds containing Al, the metal compounds preferably contain Al.

[0084] Preferred examples of metal compounds containing Al include aluminum hydroxide, γ-alumina, α-alumina, boehmite, diaspore, hydrotalcite, and any combination thereof, more preferably aluminum hydroxide and / or γ-alumina, and most preferably aluminum hydroxide. The concentration of Al in the electrolyte is preferably 0.001 mol / L or more, more preferably 0.01 mol / L or more, even more preferably 0.1 mol / L or more, further preferably 1.0 mol / L or more, particularly preferably 2.0 mol / L or more, particularly preferably more than 3.0 mol / L, and most preferably 3.3 mol / L or more. It is preferable to intentionally dissolve a large amount of Al, for example, more preferably an amount greater than that contained in the LDH-like compound. Therefore, the upper limit of the concentration of Al in the electrolyte is not particularly limited, and the saturation solubility of the Al compound can be achieved, but for example, it is 20 mol / L or less or 10 mol / L or less.

[0085] The positive electrode can be selected appropriately according to the type of battery, and can also be an air electrode. The negative electrode can also be selected appropriately according to the type of battery; for example, in the case of various zinc secondary batteries, it can contain zinc, zinc alloys, and / or zinc compounds. In the above-described battery components, at least the negative electrode and the alkaline electrolyte can be contained in a container (preferably a resin container). Figure 1 As shown in the nickel-zinc battery 10, the container 22 can also hold the positive electrode 12 and the positive electrolyte 14, but as Figure 3AIn the case of the zinc-air secondary battery 30 shown, where the positive electrode is configured as an air electrode 32, the air electrode 32 (positive electrode) does not necessarily need to be completely contained within the container 46. It can be installed simply by sealing the opening 46a of the container 46 (e.g., in the form of a cap). It should be noted that the positive electrode and the alkaline electrolyte do not necessarily need to be separated; they can be configured as a positive electrode mixture, where the positive electrode is an air electrode and therefore no electrolyte is needed on the positive electrode side. Similarly, the negative electrode and the alkaline electrolyte do not necessarily need to be separated; they can be configured as a negative electrode mixture. The positive current collector can be positioned in contact with the positive electrode as needed. Conversely, the negative current collector can be positioned in contact with the negative electrode as needed.

[0086] According to a preferred embodiment of the invention, the battery comprises an LDH-like compound as a separator with hydroxide ion conductivity (i.e., an LDH-like compound separator), preferably separating the positive and negative electrodes. For example, it can be as follows: Figure 1 As shown in the nickel-zinc battery 10, the separator 20 is configured to divide the container 22 into a positive electrode chamber 24 containing the positive electrode 12 and the positive electrolyte 14, and a negative electrode chamber 26 containing the negative electrode 16 and the negative electrolyte 18. Alternatively, it can be configured as follows: Figure 3AAs shown in the zinc-air secondary battery 30, the separator 40 is configured to seal the opening 46a of the container 46 in a manner that allows it to contact the electrolyte 36, forming a sealed space on the negative electrode side with the container 46. The separator is preferably densified to have hydroxide ion conductivity but no water permeability or air permeability. That is, the separator's lack of water permeability and air permeability means that it has a high degree of density that prevents water and gas from passing through, and that it is not a porous membrane or other porous material that is water-permeable or air-permeable. Therefore, in the case of a zinc secondary battery, this configuration is extremely effective in preventing short circuits between the positive and negative electrodes caused by the physical prevention of zinc dendrite formation during charging. Furthermore, in the case of a metal-air secondary battery, this configuration is extremely effective in preventing the intrusion of carbon dioxide from the air, thereby preventing the precipitation of basic carbonates (caused by carbon dioxide) in the electrolyte. In summary, because the separator has hydroxide ion conductivity, the required hydroxide ions can move efficiently between the positive electrode side (e.g., alkaline electrolyte or air electrode) and the negative electrode side (e.g., alkaline electrolyte), thereby enabling charge-discharge reactions at both the positive and negative electrodes. As described above, when using such a separator to construct secondary batteries such as zinc-nickel batteries and zinc-air secondary batteries, short circuits caused by zinc dendrites and carbon dioxide contamination (which is particularly problematic in the case of metal-air secondary batteries) can be prevented. Furthermore, to ensure this effect persists over a long period, it is desirable to suppress separator degradation. In this regard, according to this method, the degradation of hydroxide ion conductivity separators containing LDH-like compounds (hereinafter referred to as LDH-like compound separators) caused by alkaline electrolytes can be significantly reduced. It should be noted that in this specification, "LDH-like compound separator" refers to a separator containing LDH-like compounds, defined as a separator that selectively allows hydroxide ions to pass through by utilizing the hydroxide ion conductivity of LDH-like compounds. Preferred embodiments of LDH-like compound separators are described below.

[0087] The LDH-like compound separator can be composed of an LDH-like compound, or it can contain other materials (e.g., polymers) besides the LDH-like compound. It should be noted that other materials that can be used with the LDH-like compound can be materials that are themselves conductive to hydroxide ions, or materials that are not conductive to hydroxide ions. In short, by using an LDH-like compound with hydroxide ion conductivity as a separator, the electrolyte between the positive and negative electrodes can be separated, and hydroxide ion conductivity can be ensured. The LDH-like compound separator is preferably densified to a degree that it is impermeable to water and air. For example, the relative density of the LDH-like compound separator calculated by the Archimedes method is preferably 90% or more, more preferably 92% or more, and even more preferably 95% or more, but it is not limited to being dense and hard enough to prevent zinc dendrite penetration. Such a dense and hard LDH-like compound separator can be manufactured by hydrothermal treatment. Therefore, simple pressed powder without hydrothermal treatment is not ideal as the LDH-like compound separator of the present invention because it is not dense and is brittle in solution. However, hydrothermal treatment can be avoided; any method can be used as long as a dense and hard LDH-like compound separator can be obtained.

[0088] The container must at least contain the negative electrode and the alkaline electrolyte. As described above, such as Figure 1 As shown in the nickel-zinc battery 10, the container 22 can also hold the positive electrode 12 and the positive electrolyte 14. However, in cases such as Figure 3A In the case of a zinc-air secondary battery 30 as shown, where the positive electrode is configured as the air electrode 32, it is not necessary to completely contain the air electrode 32 (positive electrode) within the container 46; it can be installed simply by sealing the opening 46a of the container 46 (e.g., in the form of a cap). In summary, the container preferably has a structure that is both liquid-tight and airtight. The container is preferably a resin container, and the resin constituting the resin container is preferably a resin resistant to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, ABS resin, or modified polyphenylene ether, and even more preferably ABS resin or modified polyphenylene ether. It is preferable to use commercially available adhesives or to fix the separator and / or porous components in the container by heat bonding.

[0089] Nickel-zinc batteries

[0090] According to a preferred embodiment of the present invention, a nickel-zinc secondary battery is provided. Figure 1 An example of a nickel-zinc battery according to this method is illustrated schematically. Figure 1 The nickel-zinc battery shown depicts its initial state before charging, equivalent to the final state of discharge. However, this nickel-zinc battery can also be configured in a fully charged state. Figure 1As shown, the nickel-zinc battery 10 of this embodiment includes a positive electrode 12, a positive electrolyte 14, a negative electrode 16, a negative electrolyte 18, and a separator 20 within a container 22. The positive electrode 12 comprises nickel hydroxide and / or nickel hydroxide. The positive electrolyte 14 is an alkaline electrolyte containing an alkali metal hydroxide, impregnating the positive electrode 12. The negative electrode 16 comprises zinc and / or zinc oxide. The negative electrolyte 18 is an alkaline electrolyte containing an alkali metal hydroxide, impregnating the negative electrode 16. The container 22 contains the positive electrode 12, the positive electrolyte 14, the negative electrode 16, and the negative electrolyte 18. The positive electrode 12 and the positive electrolyte 14 do not necessarily need to be separated; they can be configured as a positive electrode mixture. Similarly, the negative electrode 16 and the negative electrolyte 18 do not necessarily need to be separated; they can also be configured as a negative electrode mixture. As needed, the positive current collector 13 is configured to contact the positive electrode 12. Additionally, as needed, the negative current collector 17 is configured to contact the negative electrode 16.

[0091] The separator 20 is configured to divide the container 22 into a positive electrode chamber 24 containing the positive electrode 12 and the positive electrolyte 14, and a negative electrode chamber 26 containing the negative electrode 16 and the negative electrolyte 18. The separator 20 is hydroxide ion conductive but not water-permeable. That is, the non-water-permeable nature of the separator 20 means that it has a high degree of density to the extent that water is impermeable, implying that it is not a water-permeable porous membrane or other porous material. Therefore, it is a highly effective configuration to prevent short circuits between the positive and negative electrodes caused by the physical prevention of zinc dendrite formation during charging. In summary, because the separator 20 is hydroxide ion conductive, the required hydroxide ions can move efficiently between the positive electrolyte 14 and the negative electrolyte 18, thereby realizing the charge-discharge reactions in the positive electrode chamber 24 and the negative electrode chamber 26. The charging reactions in the positive electrode chamber 24 and the negative electrode chamber 26 are shown below, and the discharging reactions are the reverse.

[0092] - Positive electrode: Ni(OH)₂ + OH⁻ - →NiOOH+H2O+e -

[0093] - Negative electrode: ZnO + H₂O + 2e - →Zn+2OH -

[0094] The above-mentioned negative electrode reaction consists of the following two reactions.

[0095] The dissolution reaction of ZnO: ZnO + H₂O + 2OH⁻ - →Zn(OH)4 2-

[0096] -Zn precipitation reaction: Zn(OH)4 2- +2e- →Zn+4OH -

[0097] The nickel-zinc battery 10 preferably has a positive electrode-side residual space 25 in the positive electrode chamber 24, the volume of which allows for changes in the amount of water during the positive electrode reaction, and a negative electrode-side residual space 27 in the negative electrode chamber 26, the volume of which allows for changes in the amount of water during the negative electrode reaction,. This effectively prevents adverse conditions (such as leakage, container deformation due to pressure changes) caused by changes in the amount of water in the positive electrode chamber 24 and negative electrode chamber 26, further improving the reliability of the nickel-zinc battery. Specifically, as shown in the above reaction formula, water increases in the positive electrode chamber 24 and decreases in the negative electrode chamber 26 during charging. Conversely, water decreases in the positive electrode chamber 24 and increases in the negative electrode chamber 26 during discharging. In this respect, existing separators are almost all permeable, allowing water to freely enter and exit through them. However, because the separator 20 used in this method has a highly dense, impermeable structure, water cannot freely enter or exit through it. During charging and discharging, the electrolyte volume in the positive electrode chamber 24 and / or the negative electrode chamber 26 increases unilaterally, potentially leading to leakage and other problems. Therefore, by having a positive electrode-side residual space 25 within the positive electrode chamber 24, the volume of this residual space 25 allows for changes in the amount of water generated during the positive electrode reaction, such as… Figure 2 As shown, it can act as a buffer to cope with the increase in positive electrolyte 14 during charging. That is, as Figure 2 As shown, the remaining space 25 on the positive electrode side after full charging also acts as a buffer, thereby reliably keeping the increased positive electrolyte 14 within the positive electrode chamber 24 without overflowing. Similarly, by having a remaining space 27 on the negative electrode side within the negative electrode chamber 26, the volume of which allows for a decrease or increase in water content accompanying the negative electrode reaction during charging and discharging, can act as a buffer to cope with the increase in negative electrolyte 18 during discharging.

[0098] The increase or decrease in moisture in the positive electrode chamber 24 and the negative electrode chamber 26 can be calculated based on the aforementioned reaction formula. As shown in the aforementioned reaction formula, the amount of H2O generated at the positive electrode 12 during charging is equivalent to twice the amount of H2O consumed at the negative electrode 16. Therefore, the volume of the remaining space 25 on the positive electrode side can be larger than that on the negative electrode side. In summary, it is preferable to have a volume that is somewhat or fully surplus on the positive electrode side, so as to not only accommodate the estimated increase in moisture in the positive electrode chamber 24, but also to accommodate gases such as air pre-existing in the positive electrode chamber 24, and oxygen generated by the positive electrode 12 during overcharging, at an appropriate internal pressure. In this respect, although it can be said that the remaining space 27 on the negative electrode side is larger than that on the negative electrode side... Figure 1The volume shown can be the same as that of the remaining space 25 on the positive electrode side. However, when the battery is configured in the final discharged state, it is preferable to provide a remaining space that exceeds the amount of water reduction that occurs during charging. In short, the remaining space 27 on the negative electrode side can be smaller than the remaining space 25 on the positive electrode side because the amount of water increase or decrease is only half that in the positive electrode chamber 24.

[0099] When the nickel-zinc battery 10 is constructed in the final discharged state, it is preferable that: the remaining space 25 on the positive electrode side has a volume exceeding the estimated increase in moisture due to the positive electrode reaction during charging, and the remaining space 25 on the positive electrode side is not pre-filled with positive electrolyte 14; and the remaining space 27 on the negative electrode side has a volume exceeding the estimated decrease in moisture due to the negative electrode reaction during charging, and the remaining space 27 on the negative electrode side is pre-filled with an estimated decrease in negative electrolyte 18. On the other hand, when the nickel-zinc battery 10 is constructed in the fully charged state, it is preferable that: the remaining space 25 on the positive electrode side has a volume exceeding the estimated decrease in moisture due to the positive electrode reaction during discharge, and the remaining space 25 on the positive electrode side is pre-filled with an estimated decrease in positive electrolyte 14; and the remaining space 27 on the negative electrode side has a volume exceeding the estimated increase in moisture due to the negative electrode reaction during discharge, and the remaining space 27 on the negative electrode side is not pre-filled with negative electrolyte 18.

[0100] Preferably, the positive electrode 12 is not filled in the remaining space 25 on the positive electrode side and / or the negative electrode 16 is not filled in the remaining space 27 on the negative electrode side. More preferably, the positive electrode 12 and the negative electrode 16 are not filled in the remaining spaces 25 on the positive electrode side and 27 on the negative electrode side, respectively. In these remaining spaces, electrolyte depletion occurs due to the reduction of water content during charging and discharging. That is, even if the positive electrode 12 and the negative electrode 16 are filled in these remaining spaces, they cannot fully participate in the charging and discharging reaction, so there is no efficiency. Therefore, by not filling the positive electrode 12 and the negative electrode 16 in the remaining spaces 25 on the positive electrode side and 27 on the negative electrode side, respectively, the positive electrode 12 and the negative electrode 16 can participate in the battery reaction more efficiently and stably without waste.

[0101] The separator 20 is a component that has hydroxide ion conductivity but is not permeable to water, typically in the form of a plate, film, or layer. The separator 20 is disposed within the container 22 to divide the container into a positive electrode chamber 24 containing the positive electrode 12 and the positive electrolyte 14, and a negative electrode chamber 26 containing the negative electrode 16 and the negative electrolyte 18. Furthermore, as described above, a second separator (resin separator) made of a water-absorbing resin or a liquid-retaining resin, such as non-woven fabric, can be disposed between the positive electrode 12 and the separator 20 and / or between the negative electrode 16 and the separator 20, thus creating a configuration that can retain the electrolyte in the reaction portions of the positive and / or negative electrodes even when the electrolyte level decreases. Preferred examples of water-absorbing or liquid-retaining resins include polyolefin resins.

[0102] Positive electrode 12 contains nickel hydroxide and / or nickel hydroxyl oxide. For example, in... Figure 1 In the case of a nickel-zinc battery where the discharge state is shown, it is sufficient to use nickel hydroxide as the positive electrode 12. Figure 2 In the case of a nickel-zinc battery in its fully charged state, nickel hydroxide can be used as the positive electrode 12. Nickel hydroxide and nickel hydroxide (hereinafter referred to as nickel hydroxide, etc.) are commonly used positive electrode active materials in nickel-zinc batteries, typically in particle form. In nickel hydroxide, other elements besides nickel can be dissolved in its crystal lattice, thereby improving charging efficiency at high temperatures. Examples of such other elements include zinc and cobalt. In addition, nickel hydroxide, etc., can be mixed with cobalt-based components, examples of such cobalt-based components include metallic cobalt, cobalt oxide (e.g., cobalt monoxide) granules. Furthermore, the surface of nickel hydroxide particles (which may contain other elements dissolved in their crystals) can be coated with a cobalt compound, examples of such cobalt compounds include cobalt monoxide, divalent α-type cobalt hydroxide, divalent β-type cobalt hydroxide, compounds of higher-order cobalt with valences greater than divalent, and any combination thereof.

[0103] In addition to nickel hydroxide compounds and dissimilar elements that can be dissolved in nickel hydroxide compounds, cathode 12 may further include additional elements. Examples of such additional elements include scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and mercury (Hg), and any combination thereof. The form in which the additional elements are included is not particularly limited; they may be included in the form of elemental metals or metal compounds (e.g., oxides, hydroxides, halides, and carbonates). When a metal monomer or metal compound containing the additional element is added, the amount added is preferably 0.5 to 20 parts by weight, more preferably 2 to 5 parts by weight, relative to 100 parts by weight of the nickel hydroxide compound.

[0104] The positive electrode 12 can also be configured as a positive electrode mixture by further including an electrolyte, etc. The positive electrode mixture may include nickel hydroxide compound particles, electrolyte, and conductive materials such as carbon particles, binders, etc., as needed.

[0105] Preferably, the positive current collector 13 is configured to contact the positive electrode 12. The positive current collector 13 can be configured as follows: Figure 1The positive electrode 13 extends through the container 22 and outwards, constituting the positive terminal itself. It can also be configured to connect to a separately provided positive terminal, either inside or outside the container 22. A preferred example of the positive current collector 13 is a porous nickel substrate, such as a foamed nickel plate. In this case, it is preferable, for example, to fabricate the positive electrode plate formed by the positive electrode 12 / positive current collector 13 by uniformly coating a paste containing an electrode active material such as nickel hydroxide onto the porous nickel substrate and then drying it. At this time, it is also preferable to perform a pressing process on the dried positive electrode plate (i.e., the positive electrode 12 / positive current collector 13) to prevent the electrode active material from falling off and to increase the electrode density.

[0106] The negative electrode 16 comprises zinc and / or zinc oxide. Zinc may be contained in any form, such as zinc metal, zinc compounds, or zinc alloys, as long as it possesses suitable electrochemical activity for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, and calcium zincate; more preferably, a mixture of zinc metal and zinc oxide is preferred. The negative electrode 16 may be configured as a gel or mixed with an electrolyte to form a negative electrode mixture. For example, by adding an electrolyte and a thickener to the negative electrode active material, a negative electrode that is easily gelled can be obtained. Examples of thickeners include polyvinyl alcohol, polyacrylate, CMC, and alginic acid; polyacrylic acid is preferred because of its excellent resistance to chemical corrosion by strong alkalis.

[0107] As the zinc alloy, zinc alloys known as mercury-free and lead-free zinc alloys can be used. For example, zinc alloys containing 0.01–0.06% by mass of indium, 0.005–0.02% by mass of bismuth, and 0.0035–0.015% by mass of aluminum are preferred because they have the effect of suppressing hydrogen production. In particular, indium and bismuth are advantageous in improving discharge performance. Using a zinc alloy as the negative electrode can slow down the self-dissolution rate in alkaline electrolytes, thereby suppressing hydrogen production and improving safety.

[0108] The shape of the negative electrode material is not particularly limited, but it is preferred to be made into a powder form, which increases the surface area and enables it to withstand high-current discharge. The preferred average particle size of the negative electrode material, in the case of zinc alloy, is in the range of 90 to 210 μm. If it is within this range, the surface area is large, so it is suitable for handling high-current discharge, and it is easy to mix uniformly with electrolyte and gelling agent, and the handling properties during battery assembly are also good.

[0109] Preferably, the negative current collector 17 is configured to contact the negative electrode 16. The negative current collector 17 can be configured as follows: Figure 1The negative electrode 16 extends through the container 22 and outwards, constituting the negative terminal itself. It can also be configured to connect to a separately provided negative terminal, either inside or outside the container 22. A preferred example of the negative current collector 17 is perforated copper metal. In this case, for example, by coating the perforated copper metal with a mixture containing zinc oxide powder and / or zinc powder, and a binder (e.g., polytetrafluoroethylene particles) as needed, a negative electrode plate formed from the negative electrode 16 / negative current collector 17 can be suitably fabricated. At this time, it is also preferable to perform a pressing process on the dried negative electrode plate (i.e., the negative electrode 16 / negative current collector 17) to prevent the electrode active material from falling off and to increase the electrode density.

[0110] Zinc-air secondary batteries

[0111] According to another preferred embodiment of the present invention, a zinc-air secondary battery is provided. Figure 3A and 3B An example of a zinc-air secondary battery according to this method is schematically shown. For example... Figure 3A and 3B As shown, the zinc-air secondary battery 30 of this embodiment includes an air electrode 32, a negative electrode 34, an alkaline electrolyte 36, a separator 40, a container 46, and a third electrode 38 for use as needed. The air electrode 32 functions as the positive electrode. The negative electrode 34 contains zinc, a zinc alloy, and / or a zinc compound. The electrolyte 36 is an aqueous electrolyte impregnating the negative electrode 34. The container 46 has an opening 46a that accommodates the negative electrode 34, the electrolyte 36, and the third electrode 38. The separator 40 seals the opening 46a in a manner that allows it to contact the electrolyte 36, forming a closed space on the negative electrode side with the container 46, thereby separating the air electrode 32 and the electrolyte 36 in a manner that allows the conduction of hydroxide ions. The positive electrode current collector 42 can be configured to contact the air electrode 32 as needed. Alternatively, the negative electrode current collector 44 can be configured to contact the negative electrode 34 as needed, in which case the negative electrode current collector 44 can also be accommodated within the container 46.

[0112] As described above, the separator 40 is preferably a component that has hydroxide ion conductivity but not water permeability or air permeability, typically in the form of a plate, film, or layer. The separator 40 seals the opening 46a in a manner that allows it to contact the electrolyte 36, forming a sealed space on the negative electrode side with the container 46, separating the air electrode 32 and the electrolyte 36 in a manner that allows hydroxide ion conduction. The separator 40 may have a porous substrate. In addition, a water-retaining material such as non-woven fabric or a liquid-retaining resin can be disposed between the negative electrode 34 and the separator 40, so that the electrolyte 36 is kept in a state where it can always contact the negative electrode 34 and the separator 40 even when the electrolyte 36 decreases. This water-retaining component can also serve as a water-retaining component for the aforementioned third electrode 38, or a separate water-retaining component for the separator 40 can be used. As a water-retaining component, commercially available battery separators can also be used. As a preferred example of a water-absorbing resin or a liquid-retaining resin, a polyolefin resin can be cited.

[0113] The air electrode 32 can be a known air electrode used in metal-air batteries such as zinc-air batteries, and is not particularly limited. A typical example of the air electrode 32 includes an air electrode catalyst, an electronically conductive material, and a hydroxide ion-conducting material used as needed. However, when using an air electrode catalyst that also functions as an electronically conductive material, the air electrode 32 may include such an electronically conductive material as both an air electrode catalyst and a hydroxide ion-conducting material used as needed.

[0114] The air electrode catalyst is not particularly limited to any material that functions as the positive electrode in a metal-air battery; various air electrode catalysts capable of using oxygen as the positive electrode active material can be used. Preferred examples of air electrode catalysts include carbon-based materials with redox catalytic activity such as graphite, metals with redox catalytic activity such as platinum and nickel, and inorganic oxides with redox catalytic activity such as perovskite oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel oxides. The shape of the air electrode catalyst is not particularly limited, but particle shape is preferred. The content of the air electrode catalyst in the air electrode 32 is not particularly limited, but is preferably 5 to 70% by volume, more preferably 5 to 60% by volume, and even more preferably 5 to 50% by volume, relative to the total amount of the air electrode 32.

[0115] The electronically conductive material is not particularly limited to any material that is conductive and capable of conducting electrons between the air electrode catalyst and the separator 40 (or, where appropriate, the intermediate layer described later). Preferred examples of electronically conductive materials include: carbon blacks such as Ketjen black, acetylene black, channel black, furnace black, lampblack, and pyrolysis black; graphite such as flake graphite, natural graphite, artificial graphite, and expanded graphite; conductive fibers such as carbon fibers and metal fibers; metal powders such as copper, silver, nickel, and aluminum; organic electronically conductive materials such as polyphenylene derivatives; and any mixtures thereof. The shape of the electronically conductive material can be particle-shaped or other shapes, but it is preferred to use it in the form of a phase (i.e., an electronically conductive phase) that is continuous in the thickness direction in the air electrode 32. For example, the electronically conductive material can be a porous material. In addition, the electronically conductive material can be in the form of a mixture or composite with the air electrode catalyst (e.g., carbon loaded with platinum), and as mentioned above, it can be an air electrode catalyst that also functions as an electronically conductive material (e.g., a perovskite-type compound containing a transition metal). The content of the electronically conductive material in the air electrode 32 is not particularly limited, but is preferably 10 to 80% by volume relative to the total amount of the air electrode 32, more preferably 15 to 80% by volume, and even more preferably 20 to 80% by volume.

[0116] The air electrode 32 can further include a hydroxide ion-conducting material as an arbitrary component. In particular, when the separator 40 is formed of a hydroxide ion-conducting inorganic solid electrolyte as a dense ceramic, an air electrode 32 containing not only the conventionally used air electrode catalyst and electronically conductive material, but also the hydroxide ion-conducting material, is formed on such a separator 40 (with an intermediate layer having hydroxide ion conductivity as needed). This ensures the desired characteristics obtained from the dense ceramic separator 40 and reduces the reaction resistance of the air electrode in the metal-air battery. That is, by including not only the air electrode catalyst and electronically conductive material, but also the hydroxide ion-conducting material in the air electrode 32, the three-phase interface formed by the electronically conductive phase (electronically conductive material) and the gas phase (air) exists not only at the interface between the separator 40 (or, where appropriate, the intermediate layer) and the air electrode 32, but also within the air electrode 32 itself. This allows for more efficient acceptance and donation of hydroxide ions that contribute to the battery reaction with a larger surface area, resulting in a reduced reaction resistance of the air electrode in the metal-air battery. The hydroxide ion-conducting material can be any material that allows hydroxide ions to pass through; there are no particular limitations. It can be either inorganic or organic, and materials of various materials and forms can be used, including the aforementioned LDH-like compounds. The hydroxide ion-conducting material is not limited to particle form; it can also be a coating film partially or substantially entirely coated with the air electrode catalyst and the electron-conducting material. However, even in the form of this coating film, it is preferable that the ion-conducting material is not dense but has open pores, allowing O2 and H2O to diffuse from the outer surface of the air electrode 32 to the interface with the separator 40 (or, where appropriate, the intermediate layer). The content of the hydroxide ion-conducting material in the air electrode 32 is not particularly limited, but is preferably 0–95% by volume, more preferably 5–85% by volume, and even more preferably 10–80% by volume, relative to the total amount of the air electrode 32.

[0117] The air electrode 32 can be formed by any method without particular limitation. For example, the air electrode catalyst, electronically conductive material, and hydroxide ion-conducting material as needed can be wet-mixed with a solvent such as ethanol, dried and crushed, mixed with a binder, fibrillated, and the resulting fibrillate mixture can be pressed onto a current collector to form the air electrode 32. The air electrode 32 side of the laminated sheet of air electrode 32 / current collector can be pressed onto the separator 40 (or, where appropriate, the intermediate layer). Alternatively, the air electrode catalyst, electronically conductive material, and hydroxide ion-conducting material as needed can be wet-mixed with a solvent such as ethanol to form a slurry, the slurry can be coated onto the intermediate layer and dried to form the air electrode 32. Therefore, the air electrode 32 can also contain a binder. The binder can be a thermoplastic resin or a thermosetting resin, without particular limitation.

[0118] The air electrode 32 is preferably a layered structure with a thickness of 5 to 200 μm, more preferably 5 to 100 μm, even more preferably 5 to 50 μm, and particularly preferably 5 to 30 μm. For example, when a hydroxide ion-conducting material is included, a thickness within the above range can suppress the increase in gas diffusion resistance and ensure a relatively large area of ​​the three-phase interface, thereby achieving a more ideal reduction in the reaction resistance of the air electrode.

[0119] Preferably, a ventilated positive current collector 42 is provided on the side of the air electrode 32 opposite to the partition 40. In this case, the positive current collector 42 preferably has ventilation to supply air to the air electrode 32. Preferred examples of the positive current collector 42 include metal plates or meshes such as stainless steel, copper, and nickel, carbon paper, carbon cloth, and electronically conductive oxides. Considering corrosion resistance and ventilation, stainless steel mesh is particularly preferred.

[0120] An intermediate layer can be provided between the separator 40 and the air electrode 32. The intermediate layer only needs to improve the adhesion between the separator 40 and the air electrode 32 and have hydroxide ion conductivity; it is not particularly limited and can be made of either organic or inorganic materials, and can be a layer of various known compositions and structures. The intermediate layer preferably comprises a polymer material and / or a ceramic material. In this case, at least either the polymer material or the ceramic material contained in the intermediate layer needs to have hydroxide ion conductivity. Multiple intermediate layers can be provided, and these multiple intermediate layers can be layers of the same type and / or different layers. That is, the intermediate layer can be a single layer or a combination of two or more layers. The intermediate layer preferably has a thickness of 1–200 μm, more preferably 1–100 μm, further preferably 1–50 μm, and particularly preferably 1–30 μm. Such a thickness easily improves the adhesion between the separator 40 and the air electrode 32, and can more effectively reduce the battery resistance (especially the interface resistance between the air electrode and the separator) in the zinc-air secondary battery.

[0121] The negative electrode 34 contains zinc, zinc alloys, and / or zinc compounds that function as the negative electrode active material. The negative electrode 34 can be of any shape or form, such as particulate, plate-like, or gel-like; from the perspective of reaction rate, it is preferred to be particulate or gel-like. As a particulate negative electrode, particles with a particle size of 30–350 μm are preferably used. As a gel-like negative electrode, a product formed by mixing and stirring mercury-free zinc alloy powder with a particle size of 100–300 μm, an alkaline electrolyte, and a thickener (gelling agent) is preferably used. The zinc alloy can be a mercury-containing or mercury-free alloy such as magnesium, aluminum, lithium, bismuth, indium, or lead, as long as the desired performance as the negative electrode active material is ensured; its content is not particularly limited. A mercury-free zinc alloy without added lead is preferred; a combination of aluminum, bismuth, indium, or the like is more preferred. Further preferred are mercury-free zinc alloys containing 50–1000 ppm bismuth, 100–1000 ppm indium, 10–100 ppm aluminum and / or calcium, and particularly preferred are those containing 100–500 ppm bismuth, 300–700 ppm indium, 20–50 ppm aluminum and / or calcium. Zinc oxide is an example of a preferred zinc compound.

[0122] Preferably, the negative current collector 44 is positioned in contact with the negative electrode 34. For example... Figure 3A and 3B As shown, the negative current collector 44 can penetrate the container 46 and extend to its outer side, constituting the negative terminal itself, or it can be configured to be connected to another negative terminal inside or outside the container 46. Preferred examples of the negative current collector include metal plates or meshes such as stainless steel, copper (e.g., perforated copper), and nickel, as well as carbon paper and oxide conductors. For example, by coating a mixture containing zinc oxide powder and / or zinc powder and a binder (e.g., polytetrafluoroethylene particles) used as needed onto perforated copper metal, a negative electrode plate formed from the negative electrode 34 / negative current collector 44 can be appropriately fabricated. In this case, it is also preferable to perform a pressing treatment on the dried negative electrode plate (i.e., negative electrode 34 / negative current collector 44) to prevent the electrode active material from falling off and to increase the electrode density.

[0123] The third electrode 38 can be configured to contact the electrolyte 36 but not the negative electrode 34, in which case it is connected to the air electrode 32 via an external circuit. With this configuration, hydrogen gas generated from the negative electrode 34 due to a side reaction can come into contact with the third electrode 38 and be converted back into water through the following reaction.

[0124] Third electrode: H2 + 2OH - →2H₂O + 2e -

[0125] Positive electrode discharge: O2 + 2H2O + 4e - →4OH -

[0126] In other words, the hydrogen gas generated at the negative electrode 34 is absorbed by the third electrode 38 and undergoes self-discharge. This suppresses or avoids the increase in internal pressure in the sealed space on the negative electrode side caused by hydrogen gas generation and the resulting adverse conditions, and also allows the generation of water (which decreases with the discharge reaction according to the above reaction formula), suppressing or avoiding insufficient water in the sealed space on the negative electrode side. That is, the hydrogen gas generated from the negative electrode can be converted back into water in the sealed space on the negative electrode side for reuse. As a result, a highly reliable zinc-air secondary battery can be provided, which has a structure that is highly effective in preventing short circuits caused by zinc dendrites and carbon dioxide contamination, and also addresses the problem of hydrogen gas generation.

[0127] The third electrode 38 is any electrode that can be connected to the air electrode 32 via an external circuit, thereby converting hydrogen (H2) into water (H2O) through the aforementioned reaction. There are no particular limitations, but it is preferable that the oxygen overvoltage is greater than that of the air electrode 32. Furthermore, it is also preferable that the third electrode 38 does not participate in the usual charge-discharge reaction. The third electrode 38 preferably contains platinum and / or carbon materials, more preferably carbon materials. Preferred examples of carbon materials include: natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, carbon nanotubes, graphene, activated carbon, and any combination thereof. The shape of the third electrode 38 is not particularly limited, but a shape with a larger specific surface area (e.g., mesh, particle shape) is preferred. The third electrode 38 (preferably a third electrode with a large specific surface area) is more preferably coated and / or disposed on a current collector. The current collector for the third electrode 38 can be of any shape; preferred examples include: wire (e.g., metal wire), perforated metal, mesh, foamed metal, and any combination thereof. The material used as the current collector for the third electrode 38 can be the same as the material of the third electrode 38, or it can be a metal (e.g., nickel), an alloy, or other conductive material.

[0128] The third electrode 38 is preferably positioned in contact with the electrolyte 36, but not directly related to the normal charge-discharge reaction. In this case, a water-retaining component made of a non-woven fabric or other absorbent resin or liquid-retaining resin can be arranged in a sealed space on the negative electrode side in a manner that allows contact with the third electrode 38, thus creating a configuration in which the electrolyte 36 is always kept in contact with the third electrode 38 even when the electrolyte level decreases. Commercially available battery separators can also be used as the water-retaining component. Polyolefin resins are preferred examples of absorbent or liquid-retaining resins. The third electrode 38 does not necessarily need to be impregnated with a large amount of electrolyte 36; a small or trace amount of electrolyte 36 is sufficient to perform the desired function, so the water-retaining component only needs to have this level of water-retaining performance.

[0129] LDH-like compound separator

[0130] The LDH-like compound separator is a separator containing a layered double hydroxide (LDH-like) compound. When installed in a zinc secondary battery, it separates the positive and negative plates in a manner that enables the conduction of hydroxide ions. That is, the LDH-like compound separator functions as a hydroxide ion conducting separator. Preferably, the LDH-like compound separator is airtight and / or watertight. In other words, the LDH-like compound separator is preferably densified to a degree that it is airtight and / or watertight. It should be noted that, in this specification, "airtight" means, as described in Patent Documents 2 and 3, that even when helium gas is brought into contact with one side of the test object in water at a differential pressure of 0.5 atm, no bubbles generated by the helium gas are observed from the other side. Furthermore, in this specification, "watertight" means, as described in Patent Documents 2 and 3, that water in contact with one side of the test object does not permeate to the other side. In other words, the impermeability of LDH-like compound separators to air and / or water means that they possess a high degree of density that prevents gas or water from passing through, and that they are not porous films or other porous materials that are permeable to water or air. Therefore, due to their hydroxide ion conductivity, LDH-like compound separators allow only selective permeation of hydroxide ions, thus fulfilling their function as battery separators. This configuration is therefore extremely effective in preventing short circuits between the positive and negative electrodes by physically preventing separator penetration caused by zinc dendrites generated during charging. Because of the hydroxide ion conductivity of the LDH-like compound separator, efficient movement of the required hydroxide ions between the positive and negative electrodes can be achieved, thereby enabling the charge and discharge reactions of both electrodes.

[0131] The He permeability per unit area of ​​the LDH-like compound separator is preferably 3.0 cm / min·atm or less, more preferably 2.0 cm / min·atm or less, and even more preferably 1.0 cm / min·atm or less. A separator with a He permeability of 3.0 cm / min·atm or less can extremely effectively suppress the permeation of Zn (typically zinc ions or zincate ions) in the electrolyte. Based on the principle, it can be considered that the separator of this type significantly suppresses Zn permeation in the above manner, thereby effectively suppressing the growth of zinc dendrites when used in zinc secondary batteries. The He permeability is measured by the following steps: supplying He gas to one side of the separator and allowing the He gas to pass through the separator; and calculating the He permeability and evaluating the compactness of the hydroxide ion-conducting separator. The He permeability is calculated using the He gas permeation rate F per unit time, the differential pressure P applied to the separator during He gas permeation, and the membrane area S through which the He gas passes, according to the formula F / (P×S). By evaluating the permeability using He gas, it is possible to assess whether a very high level of tightness is achieved. Consequently, it is possible to effectively evaluate high tightness that minimizes the permeability of substances other than hydroxide ions (especially Zn, which causes zinc dendrite growth) (permeating only in extremely small amounts). This is because He gas has the smallest constituent unit among the diverse atoms or molecules that can constitute a gas, and its reactivity is extremely low. That is, He does not form molecules but constitutes He gas as elemental He atoms. In this respect, since hydrogen gas is composed of H2 molecules, the elemental He atom is relatively small as a gaseous constituent unit. Since H2 gas is a flammable gas, it is more dangerous. Furthermore, by using an index such as the He gas permeability defined by the above formula, an objective evaluation of tightness can be easily performed regardless of the sample size or measurement conditions. Therefore, it is possible to easily, safely, and effectively evaluate whether a separator has sufficiently high tightness suitable for zinc secondary batteries. It is preferable to measure the He permeability in the order shown in Evaluation 5 of the following embodiment.

[0132] In the preferred LDH-like compound separator, the LDH-like compound seals the pores of the porous substrate; more preferably, the pores of the porous substrate are completely sealed by the LDH-like compound. The preferred manner and composition of the LDH-like compound are as described above. Preferably, the porous substrate is composed of at least one material selected from the group consisting of ceramic materials, metallic materials, and polymeric materials.

[0133] That is, the LDH-like compound separator comprises an LDH-like compound and a porous substrate (typically composed of a porous substrate and an LDH-like compound). Preferably, the LDH-like compound seals the pores of the porous substrate, thereby enabling the LDH-like compound separator to exhibit hydroxide ion conductivity and air impermeability (thus functioning as an LDH-like compound separator exhibiting hydroxide ion conductivity). Particularly preferred is that the LDH-like compound is embedded throughout the thickness direction of the porous substrate. The thickness of the LDH-like compound separator is preferably 5–80 μm, more preferably 5–60 μm, and even more preferably 5–40 μm.

[0134] The porous substrate is preferably composed of at least one material selected from the group consisting of ceramic materials, metallic materials, and polymeric materials. Preferred examples of ceramic materials include alumina, zirconium oxide, titanium dioxide, magnesium oxide, spinel, calcium oxide, cordierite, zeolite, andalusite, ferrite, zinc oxide, silicon carbide, aluminum nitride, silicon nitride, and any combination thereof; more preferably, alumina, zirconium oxide, titanium dioxide, and any combination thereof; particularly preferably, alumina and zirconium oxide; and most preferably, alumina. Especially when using an alumina-based porous substrate with an electrolyte containing dissolved Al, it is expected to suppress the dissolution of Al from the alumina-based porous substrate and also suppress the deterioration of the porous substrate. Using these porous ceramics facilitates the formation of a dense, LDH-containing separator layer. Preferred examples of metallic materials include aluminum and zinc.

[0135] In particular, the porous substrate is preferably made of a polymer material. Polymer porous substrates have the following advantages: 1) flexibility (therefore, even with thinning, cracking is difficult); 2) easy improvement of porosity; 3) easy improvement of conductivity (due to the ability to improve porosity and reduce thickness); 4) ease of manufacturing and processing. Furthermore, the flexible advantage resulting from 1) above also provides the following advantage: 5) it allows for easy bending or sealing of LDH-like compound separators containing a porous substrate made of polymer materials. Preferred examples of polymer materials include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluoropolymers (tetrafluoroethylene resins: PTFE, etc.), cellulose, nylon, polyethylene, and any combination thereof. More preferably, based on the viewpoint of thermoplastic resins suitable for heat pressing, examples include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluoropolymers (tetrafluoroethylene resins: PTFE, etc.), nylon, polyethylene, and any combination thereof. All of the aforementioned preferred materials possess alkali resistance, making them suitable for use as electrolytes in batteries. From the viewpoint of excellent resistance to hot water, acids, and alkalis, and low cost, polyolefins such as polypropylene and polyethylene are particularly preferred polymeric materials, with polypropylene or polyethylene being the most preferred. When the porous substrate is composed of a polymeric material, it is particularly preferable that the LDH-like compound layer is embedded throughout the entire thickness direction of the porous substrate (e.g., most or almost all of the pores inside the porous substrate are filled with the LDH-like compound). Commercially available polymeric microporous membranes can be preferably used as such polymeric porous substrates.

[0136] Manufacturing method

[0137] There is no particular limitation on the manufacturing method of LDH-like compound separators. They can be manufactured by appropriately modifying the conditions (especially the composition of LDH raw materials) of known manufacturing methods of LDH-containing functional layers and composite materials (for example, see Patent Documents 1-3). For example, (1) a porous substrate is prepared; (2) a solution containing titanium dioxide sol (or, also containing yttrium sol and / or alumina sol) is coated onto the porous substrate and dried to form a titanium dioxide layer; (3) the porous substrate is impregnated with a solution containing magnesium ions (Mg... 2+ ) and urea (or, also contains yttrium ions (Y) 3+(3) In the raw material aqueous solution; (4) The porous substrate is subjected to hydrothermal treatment in the raw material aqueous solution, so that the functional layer containing LDH-like compounds is formed on and / or in the porous substrate, thereby enabling the manufacture of the functional layer containing LDH-like compounds and composite material (i.e., LDH-like compound separator). In addition, it is believed that because urea is present in the above process (3), ammonia is generated in the solution by the hydrolysis of urea, thereby increasing the pH value, and the coexisting metal ions form hydroxides and / or oxides, thereby obtaining LDH-like compounds.

[0138] Especially in the case of manufacturing a composite material with a porous substrate made of polymeric material and an LDH-like compound embedded in the entire thickness direction of the porous substrate (i.e., an LDH-like compound partition), it is preferable to apply the mixed sol solution described in (2) to the substrate by a method that allows the mixed sol solution to penetrate into the entire or most of the interior of the substrate. This allows most or almost all of the pores inside the porous substrate to be filled with the LDH-like compound. Examples of preferred coating methods include dip coating and filter coating, with dip coating being particularly preferred. The amount of mixed sol solution adhering can be adjusted by changing the number of coats applied in dip coating or similar methods. After the substrate coated with the mixed sol solution by dip coating or similar methods is dried, the steps (3) and (4) described above can be performed.

[0139] When the porous substrate is made of a polymer material, it is preferable to perform a pressing process on the LDH-like compound separator obtained by the above-described methods. This results in an LDH-like compound separator with superior density. The pressing method can be, for example, roll pressing, single-screw pressing, CIP (cold isostatic pressing), etc., without particular limitation, but roll pressing is preferred. By softening the porous polymer substrate, the pores of the porous substrate can be fully sealed using the LDH-like compound; in this regard, it is preferable to perform the pressing while heating. For example, in the case of polypropylene or polyethylene, heating to 60°C to 200°C is preferred as the temperature for sufficient softening. By performing pressing such as roll pressing within this temperature range, the residual pores in the LDH-like compound separator can be significantly reduced. As a result, the LDH-like compound separator can be made extremely highly dense, thus further effectively suppressing short circuits caused by zinc dendrites. By adjusting the roll gap and roll temperature appropriately during the rolling process, the morphology of residual pores can be controlled, thereby obtaining the desired dense LDH-like compound separator.

[0140] Example

[0141] The invention will be described in more detail using the following examples.

[0142] [Example A1~A5]

[0143] Examples A1 to A5 shown below are reference examples related to LDH compacts (LDH separators) or comparative examples, but the experimental order and results in these examples are also applicable to LDH-like compacts (LDH-like separators).

[0144] Example A1 (Reference): Preparation and Evaluation of LDH Compact Materials

[0145] (1) Preparation of LDH compact body

[0146] As the raw material powder, commercially available layered double hydroxide, i.e., hydrotalcite powder (DHT-4H, manufactured by Kyowa Chemical Industry Co., Ltd.) was prepared. The composition of this raw material powder is Mg. 2+ 0.68 Al 3+ 0.32 (OH)2CO3 2- 0.16 ·mH2O. The raw material powder is filled into a mold with a diameter of 16 mm, and then heated at 500 kgf·cm⁻¹. 2 The molding pressure was applied using a single-screw press to obtain a molded body with a relative density of 53% and a thickness of approximately 2 mm. It should be noted that this relative density was measured on the molded body stored at room temperature and relative humidity below 20% for 24 hours. The obtained molded body was then fired in an alumina crucible. The firing process was as follows: the temperature was increased at a rate of less than 100°C / h, held at a maximum temperature of 750°C for 5 hours, and then cooled to prevent cracking caused by the release of moisture and carbon dioxide due to rapid heating. The total firing time from heating to cooling (below 100°C) was 62 hours. The weight, volume, and relative density of the obtained sintered body were 59% by weight, 72% by volume, and 23%, respectively. It should be noted that the above "weight" and "volume" are relative values ​​(%) calculated with the molded body before firing as 100%, and the "relative density" is a relative density converted to oxides using the theoretical density calculated based on the oxides of the constituent metal elements Mg and Al of hydrotalcite. The sintered body obtained in this way was sealed in an airtight Teflon (registered trademark) container with an outer stainless steel sleeve, along with ion-exchanged water, and subjected to hydrothermal treatment under regeneration conditions (temperature and holding time at 100°C) for 5 hours to obtain a sample. Since the sample cooled to room temperature contained excess moisture, the surface moisture was gently wiped away with filter paper or similar materials. The resulting sample was then naturally dehydrated (dried) indoors at approximately 25°C and a relative humidity of about 50% to obtain a dense LDH sample.

[0147] (2) Determination of relative density

[0148] The density was calculated based on the dimensions and weight of the LDH dense sample. This density was then divided by the theoretical density to determine the relative density, which was 91%. It should be noted that the theoretical density of hydrotalcite with an Mg / Al ratio of 2, 2.09 g / cm³, as described in JCPDS Card No. 70-2151, was used in the theoretical density calculation. 3 .

[0149] (3) Crack identification

[0150] Visual inspection of the LDH dense sample revealed no cracks.

[0151] (4) Identification of crystal phase

[0152] The crystal phase of the LDH compact sample was determined using an X-ray diffraction apparatus (D8 ADVANCE, Bulker AXS) under the following conditions: voltage: 40 kV, current: 40 mA, and measurement range: 5–70°. The phase was identified using the diffraction peaks of hydrotalcite described in JCPDS Card No. 35-0965. The results showed that only peaks originating from hydrotalcite were observed.

[0153] Example A2 (Reference): Alkali resistance test of LDH compact in various electrolytes

[0154] LDH compacts were immersed in electrolytes (KOH aqueous solution) of various Al concentrations, and their alkali resistance (especially the presence and extent of Al dissolution) was investigated as follows. It should be noted that before immersion in the electrolyte, the surface microstructure of the LDH compact sample prepared in Example A1 was observed using a scanning electron microscope (SEM, JSM-6610LV, JEOL) at an accelerating voltage of 10–20 kV. The SEM images of the surface microstructure of the obtained LDH compact sample are shown below. Figure 4 As shown. In addition, before immersion in the electrolyte, the composition of the LDH dense sample prepared in Example A1 was analyzed by energy dispersive X-ray diffraction, and the Al / Mg ratios shown in Table 1 were obtained.

[0155] Electrolyte samples 1-7 were prepared by adding KOH powder and Al(OH)3 powder to ion-exchanged water and stirring at 40°C-80°C for 48 hours-30 days. For comparison, electrolyte sample 8 was prepared without adding Al(OH)3 powder, but otherwise, in the same manner as above. ICP analysis results of the obtained KOH aqueous solutions with added Al were shown in Table 1, with KOH concentration of 9 M and Al concentration. The LDH compact prepared in Example A1 was immersed in these electrolyte samples 1-8 at 30°C for one week. The LDH compact after one week of immersion was then analyzed using energy-dispersive X-ray diffraction (EDXD). Electrolyte samples 1-4 were also evaluated as an accelerated test at an immersion temperature of 70°C, in the same manner as above. The Al / Mg ratios of the immersed LDH compact are shown in Table 1. As shown in Table 1, by intentionally dissolving Al in the electrolyte (KOH aqueous solution) beforehand, the change in the Al / Mg ratio of the LDH compact body was significantly suppressed (i.e., the dissolution of Al from the LDH compact body was significantly suppressed), resulting in a significant improvement in the alkali resistance of LDH.

[0156] [Table 1]

[0157]

[0158] ★ indicates a reference sample, and * indicates a comparison sample.

[0159] The surface microstructure of LDH dense samples immersed in electrolyte sample 3 at 30℃ or 70℃ for one week was observed using a scanning electron microscope (SEM, JSM-6610LV, JEOL) with an accelerating voltage of 10–20 kV. The obtained SEM images (secondary electron images) of the surface microstructure of the LDH dense samples are shown below. Figure 5 (30℃) and Figure 6 (70℃) is shown. Additionally, the surface microstructure of the LDH dense sample, after being immersed in electrolyte sample 8 (without dissolved Al) at 30℃ for one week, was observed in the same manner as above, and the results are as follows. Figure 7 As shown.

[0160] Example A3 (Reference): Fabrication and Evaluation of LDH Separators with Porous Substrates

[0161] (1) Fabrication of porous substrate

[0162] Boehmite (Sasol, DISPAL 18N4-80), methylcellulose, and ion-exchanged water were weighed at a mass ratio of (boehmite):(methylcellulose):(ion-exchanged water) of 10:1:5, and then mixed. The resulting mixture was extruded using a manual press to form a plate with dimensions exceeding 5cm × 8cm and a thickness of 0.5cm. The resulting plate was dried at 80°C for 12 hours and then fired at 1150°C for 3 hours to obtain a porous alumina substrate. The resulting porous substrate was then cut into 5cm × 8cm pieces.

[0163] For the obtained porous substrate, the porosity of the surface was measured using image processing methods, and the result was 24.6%. The porosity was measured as follows: 1) A scanning electron microscope (SEM, JSM-6610LV, JEOL) was used to observe the surface microstructure with an accelerating voltage of 10–20 kV, obtaining SEM images of the porous substrate surface (magnification 10,000x or higher); 2) Image processing software such as Photoshop (Adobe) was used to read the grayscale SEM images; 3) A black and white binary image was created by following the steps [Image] → [Tone Correction] → [Binarization]; 4) The porosity (%) was obtained by dividing the number of pixels occupied by the black portion by the total number of pixels in the image. This porosity measurement was performed on a 6 μm × 6 μm area of ​​the porous substrate surface. It should be noted that the SEM image of the porous substrate surface is shown below. Figure 8 .

[0164] In addition, the average pore diameter of the porous substrate was measured, and the result was approximately 0.1 μm. In this invention, the average pore diameter was determined by measuring the longest distance between pores based on electron microscope (SEM) images of the porous substrate surface. The SEM images used in this measurement were magnified 20,000 times. All obtained pore diameters were arranged in dimensional order, and 15 values ​​above the average and 15 values ​​below the average were taken, totaling 30 values ​​per field of view. The average of the two fields of view was calculated to obtain the average pore diameter. The length measurement function of the SEM software was used for the length measurement.

[0165] (2) Cleaning of porous substrates

[0166] The obtained porous substrate was ultrasonically cleaned in acetone for 5 minutes, ultrasonically cleaned in ethanol for 2 minutes, and then ultrasonically cleaned in ion-exchanged water for 1 minute.

[0167] (3) Preparation of raw material aqueous solution

[0168] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.), aluminum nitrate nonahydrate (Al(NO3)3·9H2O, manufactured by Kanto Chemical Co., Ltd.), and urea ((NH2)2CO, manufactured by Sigma-Aldrich) were prepared as raw materials. According to the cation ratio (Mg... 2+ / Al 3+ The total metal ion molar concentration (Mg) is 2 and the total metal ion molar concentration (Mg) is 2. 2+ +Al 3+ The concentration of urea is 0.320 mol / L. Weigh magnesium nitrate hexahydrate and aluminum nitrate nonahydrate and place them in a beaker. Add deionized water to make a total volume of 600 ml. After stirring, the resulting solution is then dissolved in urea / NO3. - Urea, weighed in a ratio of 4, is added to the solution and stirred further to obtain a raw material aqueous solution.

[0169] (4) Film formation using hydrothermal treatment

[0170] The raw material aqueous solution prepared in (3) and the porous substrate cleaned in (2) were sealed together in a Teflon (registered trademark) sealed container (internal volume 800 ml, outer sleeve made of stainless steel). At this time, the substrate was floated and fixed from the bottom of the Teflon (registered trademark) sealed container, and placed horizontally with the solution in contact with both sides of the substrate. Then, a layered double hydroxide oriented film (partition layer) was formed on the surface of the substrate by performing hydrothermal treatment at a hydrothermal temperature of 70°C for 168 hours (7 days). After the specified time, the substrate was taken out of the sealed container, washed with ion-exchanged water, and dried at 70°C for 10 hours to obtain a dense film of layered double hydroxide (hereinafter referred to as LDH) on the substrate (hereinafter referred to as the membrane sample). The thickness of the obtained membrane sample was about 1.5 μm. Thus, a composite material sample containing layered double hydroxide (hereinafter referred to as the composite material sample) was obtained. It should be noted that the LDH membrane is formed on both sides of the porous substrate. However, in order to make the composite material have the shape of a separator, the LDH membrane on one side of the porous substrate is mechanically ground.

[0171] (5) Various evaluations

[0172] (5a) Identification of membrane samples

[0173] The crystal phase of the film sample was determined using an X-ray diffraction apparatus (RINT TTR III, Rigaku Corporation) under the following conditions: voltage: 50 kV, current: 300 mA, and measurement range: 10–70°. Figure 9The XRD pattern is shown. The obtained XRD pattern was identified using the diffraction peaks of layered double hydroxides (hydrotalcite compounds) described in JCPDS Card NO. 35-0964. The results confirmed that the membrane sample was a layered double hydroxide (LDH, hydrotalcite compound). It should be noted that... Figure 9 In the XRD pattern shown, peaks originating from alumina, which constitutes the porous substrate of the film-forming sample, were also observed (peaks marked with ○ in the figure).

[0174] (5b) Observation of microstructure

[0175] The surface microstructure of the membrane samples was observed using a scanning electron microscope (SEM, JSM-6610LV, JEOL) with an accelerating voltage of 10–20 kV. The obtained SEM images (secondary electron images) of the surface microstructure of the membrane samples are shown below. Figure 10 .

[0176] In addition, the cross-section of the composite material sample was ground using CP grinding to form a ground cross-section. The microstructure of this ground cross-section was observed using a scanning electron microscope (SEM) with an accelerating voltage of 10–20 kV. The SEM images of the microstructure of the ground cross-section of the composite material sample obtained in this way are shown below. Figure 11 .

[0177] (5c) Determination of porosity

[0178] For the membrane sample, the porosity of the membrane surface was determined using image processing methods. The porosity determination was performed as follows: 1) A scanning electron microscope (SEM, JSM-6610LV, JEOL) was used to observe the surface microstructure at an accelerating voltage of 10–20 kV, obtaining an electron microscope (SEM) image of the membrane surface (magnification ≥ 10,000x); 2) Image processing software such as Photoshop (Adobe) was used to read the grayscale SEM image; 3) A black and white binary image was created by following the steps [Image] → [Tone Correction] → [Binarization]; 4) The porosity (%) was calculated by dividing the number of pixels occupied by the black portion by the total number of pixels in the image. The porosity was measured on a 6 μm × 6 μm area of ​​the oriented membrane surface. The result showed that the surface porosity of the membrane was 19.0%. In addition, using the porosity of the membrane surface, the density D (hereinafter referred to as the surface film density) observed from the membrane surface was calculated according to D = 100% - (porosity of the membrane surface), and the result was 81.0%.

[0179] In addition, the porosity of the polished cross section was also measured for the membrane sample. Regarding the measurement of the porosity of this polished cross section, in addition to obtaining electron microscope (SEM) images (magnification of 10,000x or higher) of the polished cross section in the thickness direction of the membrane as shown in (5b) above, the procedure was the same as for the porosity of the membrane surface. This porosity measurement was performed on the membrane portion of the oriented membrane cross section. The average porosity calculated from the polished cross section of the membrane sample was 3.5% (average of the three polished cross sections), confirming that a very high-density membrane was formed despite being on a porous substrate.

[0180] (5d) Tightness test I

[0181] To confirm that the membrane sample possesses a degree of density that prevents water permeability, a density determination test was performed as described below. First, as... Figure 12A As shown, a silicone rubber 122 with a central opening 122a of 0.5 cm × 0.5 cm is bonded to the film sample side of the composite material sample 120 (cut into 1 cm × 1 cm square) obtained in (1) above. The resulting laminate is clamped and bonded using two acrylic containers 124 and 126. The acrylic container 124 on the silicone rubber 122 side is bottomless, so the silicone rubber 122 is bonded to the acrylic container 124 with its opening 122a open. On the other hand, the acrylic container 126 on the porous substrate side of the composite material sample 120 has a bottom, and ion-exchanged water 128 is injected into the container 126. At this time, Al and / or Mg can also be dissolved in the ion-exchanged water. That is, each component is arranged such that the ion-exchanged water 128 contacts the porous substrate side of the composite material sample 120 by inverting it after assembly. After assembling these components, the total weight is measured. It should be noted that a closed vent (not shown) is naturally formed on container 126, which is opened when the container is inverted. For example... Figure 12B As shown, the assembly was arranged upside down and kept at 25°C for one week, after which the total weight was measured again. At this time, water droplets adhered to the inner side of the acrylic container 124, and these droplets were wiped away. The difference in total weight before and after the test was then calculated to determine the density. The results showed that even after being kept at 25°C for one week, no change in the weight of the ion-exchanged water was observed. This confirmed that the membrane sample (i.e., the functional membrane) possesses high density to a degree of water impermeability.

[0182] (5e) Tightness Test II

[0183] To confirm that the membrane sample possesses a degree of tightness that does not allow for air permeability, a tightness determination test was performed as described below. First, as... Figure 13A and 13BAs shown, an open acrylic container 130 and an alumina clamp 132 of the shape and size that can function as a lid for the acrylic container 130 are prepared. A gas supply port 130a for supplying gas into the acrylic container 130 is formed therein. In addition, an opening 132a with a diameter of 5 mm is formed on the alumina clamp 132, and a film sample placement recess 132b is formed along the outer periphery of the opening 132a. An epoxy adhesive 134 is applied into the recess 132b of the alumina clamp 132, and the film sample 136b side of the composite material sample 136 is placed in the recess 132b, so that it is airtight and liquidtightly bonded to the alumina clamp 132. Using silicone adhesive 138, an alumina clamp 132, to which the composite material sample 136 is attached, is airtightly and liquidtightly bonded to the upper end of the acrylic container 130 to completely seal the open portion of the acrylic container 130, thus obtaining a sealed container 140 for testing. This sealed container 140 is placed in a water tank 142, and the gas supply port 130a of the acrylic container 130 is connected to a pressure gauge 144 and a flow meter 146, enabling the supply of helium gas into the acrylic container 130. Water 143 is placed in the water tank 142, completely submerging the sealed container 140. At this point, the airtightness and liquidtightness of the interior of the sealed container 140 are sufficiently ensured, the membrane sample 136b side of the composite material sample 136 is exposed within the interior space of the sealed container 140, while the porous substrate 136a side of the composite material sample 136 is in contact with the water in the water tank 142. In this state, helium gas is introduced into the sealed measuring container 140 through the gas supply port 130a within the acrylic container 130. The pressure gauge 144 and flow meter 146 are controlled to maintain a pressure difference of 0.5 atm between the inside and outside of the membrane sample 136b (i.e., the pressure applied to the side in contact with helium is 0.5 atm higher than the water pressure applied to the opposite side), and it is observed whether helium bubbles are generated from the composite material sample 136b into the water. No helium bubbles were observed. This confirms that the membrane sample 136b has a high degree of density, making it non-permeable.

[0184] Example A4 (Reference): Manufacturing and Evaluation of Nickel-Zinc Batteries

[0185] (1) Preparation of partitions with porous substrate

[0186] Following the same sequence as in Example A1, a hydrotalcite film (size: 5cm × 8cm) was prepared on an alumina substrate as a separator with a porous substrate.

[0187] (2) Fabrication of the positive electrode plate

[0188] Nickel hydroxide particles with added zinc and cobalt were prepared as a solid solution. These nickel hydroxide particles were coated with cobalt hydroxide to obtain a positive electrode active material. The obtained positive electrode active material was mixed with a 2% aqueous solution of carboxymethyl cellulose to prepare a paste. The prepared paste was uniformly coated onto a current collector formed from a nickel metal porous substrate with a porosity of approximately 95%, with a porosity of 50% for the positive electrode active material. The paste was then dried to obtain a positive electrode plate with the active material coated in a 5cm × 5cm area. At this point, the coating amount was adjusted so that the active material contained the equivalent of 4Ah of nickel hydroxide particles.

[0189] (3) Fabrication of the negative electrode plate

[0190] A mixture comprising 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder, and 3 parts by weight of polytetrafluoroethylene particles is coated onto a current collector formed of perforated copper metal to obtain a negative electrode plate with a porosity of approximately 50% and an active material portion coated in a 5 cm × 5 cm area. The coating amount is then adjusted so that the active material contains 4 Ah of zinc oxide powder equivalent to the capacity of the positive electrode plate.

[0191] (4) Battery assembly

[0192] Using the positive electrode plate, negative electrode plate, and separator with porous substrate obtained above, assemble them in the following order. Figure 1 The nickel-zinc battery shown.

[0193] First, prepare to remove the ABS resin cuboid outer casing. Insert a partition with a porous substrate (alumina substrate with a hydrotalcite film) near the center of the outer casing and fix its three sides to the inner wall of the outer casing using commercially available adhesive. Insert the positive and negative electrode plates into the positive and negative electrode chambers, respectively. At this time, position the positive and negative electrode plates so that they are in contact with the inner wall of the outer casing. Inject a 6 mol / L KOH aqueous solution, sufficient to completely submerge the positive electrode active material coating, into the positive electrode chamber as the electrolyte. The liquid level in the positive electrode chamber should be approximately 5.2 cm from the bottom of the outer casing. On the other hand, inject a 6 mol / L KOH aqueous solution, sufficient not only to completely submerge the negative electrode active material coating but also taking into account the excess amount of water expected to decrease during charging, into the negative electrode chamber as the electrolyte. The liquid level in the negative electrode chamber should be approximately 6.5 cm from the bottom of the outer casing. Connect the terminals of the positive and negative electrode current collectors to the external terminals on the upper part of the outer casing, respectively. The outer casing is fixed to the main casing using thermal bonding, thus sealing the battery casing. This yields a nickel-zinc battery. It should be noted that because the separator in this battery measures 5cm wide x 8cm high, and the active material coating portions of the positive and negative electrodes are also 5cm wide x 5cm high, the upper 3cm space of the positive and negative electrode chambers can be referred to as the remaining space on the positive and negative sides, respectively.

[0194] (5) Evaluation

[0195] The fabricated nickel-zinc battery was subjected to a constant current charge for 10 hours at a current of 0.4mA (equivalent to 0.1C for a design capacity of 4Ah). No casing deformation or electrolyte leakage was observed after charging. Observation of the electrolyte level after charging revealed that the electrolyte level in the positive electrode chamber was approximately 7.5cm from the bottom of the casing, and the electrolyte level in the negative electrode chamber was approximately 5.2cm from the bottom of the casing. During charging, the electrolyte level in the positive electrode chamber increased, while the electrolyte level in the negative electrode chamber decreased. However, there was sufficient electrolyte in the negative electrode active material coating area to retain the electrolyte within the casing, ensuring a sufficient charge-discharge reaction for both the positive and negative electrode active materials.

[0196] Example A5 (Reference): Construction of Zinc-Air Secondary Batteries

[0197] (1) Preparation of partitions with porous substrate

[0198] Following the same sequence as in Example A1, a hydrotalcite film was prepared on an alumina substrate as a separator (hereinafter referred to as the separator) with a porous substrate.

[0199] (2) Fabrication of the air polar layer

[0200] α-MnO2 particles, used as an air electrode catalyst, were prepared as follows. First, Mn(SO4)·5H2O and KMnO4 were dissolved in deionized water at a molar ratio of 5:13 and mixed. The resulting mixture was placed in a sealed stainless steel container lined with Teflon (registered trademark) and subjected to hydrothermal synthesis at 140°C for 2 hours. The precipitate obtained by hydrothermal synthesis was filtered, washed with distilled water, and dried at 80°C for 6 hours. This yielded α-MnO2 powder.

[0201] Layered double hydroxide particles (hereinafter referred to as LDH particles) were prepared as a hydroxide ion-conducting material as described below. First, Ni(NO3)2·6H2O and Fe(NO3)3·9H2O were dissolved in deionized water at a molar ratio of Ni:Fe = 3:1 and mixed. The resulting mixture was then added dropwise to a 0.3M Na2CO3 solution at 70°C with stirring. Simultaneously, 2M NaOH solution was added to adjust the pH of the mixture to 10, and the mixture was maintained at 70°C for 24 hours. The precipitate formed in the mixture was filtered, washed with distilled water, and dried at 80°C to obtain LDH powder.

[0202] The previously obtained α-MnO2 particles and LDH particles, along with carbon black (Cabot, model VXC72) as an electronically conductive material, were weighed according to the specified mixing ratio and wet-mixed in the presence of ethanol solvent. The resulting mixture was dried at 70°C and then crushed. The crushed powder was mixed with a binder (PTFE, ElectroChem, model EC-TEF-500ML) and water, and fibrillated. At this point, the amount of water added was 1% by mass relative to the air electrode. The resulting fibrillated mixture was pressed into sheets with a thickness of 50 μm onto a current collector (carbon cloth (ElectroChem, model EC-CC1-060T)) to obtain an air electrode / current collector laminate. The resulting air electrode layer comprises: 20% by volume of the electronically conductive phase (carbon black), 5% by volume of the catalyst layer (α-MnO2 particles), 70% by volume of the hydroxide ion-conducting phase (LDH particles), and 5% by volume of the binder phase (PTFE).

[0203] (3) Fabrication of an air electrode with a partition

[0204] An anion exchange membrane (ASTOM, NEOSEPTA AHA) was immersed in a 1M NaOH aqueous solution overnight. This anion exchange membrane was then laminated as an interlayer onto the hydrotalcite membrane of the separator to obtain a separator / interlayer laminate. The thickness of the interlayer was 30 μm. The previously fabricated air electrode / current collector laminate was then pressed onto the obtained separator / interlayer laminate with the air electrode layer side connected to the interlayer side, resulting in an air electrode sample with a separator.

[0205] (4) Fabrication of the negative electrode plate

[0206] A mixture comprising 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder and 3 parts by weight of polytetrafluoroethylene particles is coated onto a current collector formed of perforated copper metal to obtain a negative electrode plate with an active material portion having a porosity of approximately 50%.

[0207] (5) Fabrication of the third electrode

[0208] A platinum paste is coated onto a current collector formed of nickel mesh to obtain the third electrode.

[0209] (6) Battery assembly

[0210] Using the air electrode with separator, negative electrode plate, and third electrode obtained above, fabricate in the following order. Figure 3AThe zinc-air secondary battery shown is a horizontal structure. First, prepare an open-top container (hereinafter referred to as the resin container) made of ABS resin with a cuboid shape. Place the negative electrode plate at the bottom of the resin container with the side coated with the negative electrode active material facing upwards. At this time, the negative electrode current collector is in contact with the bottom of the resin container, and the end of the negative electrode current collector is connected to an external terminal provided through the side of the resin container. Next, place the third electrode on the inner wall of the resin container at a position higher than the upper surface of the negative electrode plate (i.e., a position that does not contact the negative electrode plate and does not participate in the charge-discharge reaction), and place the non-woven fabric separator in contact with the third electrode. Seal the opening of the resin container with the air electrode with the separator on the outside. At this time, apply a commercially available adhesive to the outer periphery of the opening to seal it in a way that provides airtightness and liquid tightness. Inject a 6 mol / L KOH aqueous solution as the electrolyte into the resin container through a small injection port provided near the top of the resin container. Thus, the separator comes into contact with the electrolyte, and due to the liquid-retaining properties of the non-woven fabric separator, the electrolyte remains in a state where it can always contact the third electrode, regardless of changes in electrolyte levels. At this point, to fabricate the battery in its final discharged state, the amount of electrolyte injected must not only fully submerge the negative electrode active material coating within the resin container but also account for any excess amount of water lost during charging. Therefore, the resin container is designed to accommodate this excess electrolyte. Finally, the injection port of the resin container is sealed. This creates an airtight and liquid-tight internal space divided by the resin container and the separator. Finally, the third electrode and the current collector layer of the air electrode are connected via an external circuit. This yields a zinc-air secondary battery.

[0211] Based on this configuration, because the separator is highly dense to the point that it is impermeable to water and gas, it can physically prevent the separator from being penetrated by zinc dendrites generated during charging, thus preventing short circuits between the positive and negative electrodes. Furthermore, it prevents the intrusion of carbon dioxide from the air, preventing the precipitation of basic carbonates (caused by carbon dioxide) in the electrolyte. Moreover, it allows hydrogen gas generated by a side reaction at the negative electrode 34 to come into contact with the third electrode 38, and through the aforementioned reaction, it is converted back into water. In other words, a highly reliable zinc-air secondary battery can be provided, which has a configuration suitable for simultaneously preventing short circuits caused by zinc dendrites and carbon dioxide intrusion, and can also address the problem of hydrogen gas generation.

[0212] [Examples B1-B8]

[0213] Examples B1 to B7 shown below are reference examples related to LDH-like compound separators, while example B8 is a comparative example related to LDH separators. Both LDH-like compound separators and LDH separators are collectively referred to as hydroxide ion-conducting separators. It should be noted that the evaluation method for the hydroxide ion-conducting separators fabricated in the following examples is as follows.

[0214] Rating 1 Observation of surface microstructure

[0215] The surface microstructure of the hydroxide ion-conducting septum was observed using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an accelerating voltage of 10–20 kV.

[0216] Rating 2 STEM analysis of layered structures

[0217] The layered structure of the hydroxide ion-conducting septum was observed using a scanning transmission electron microscope (STEM) (product name: JEM-ARM200F, manufactured by JEOL) at an accelerating voltage of 200 kV.

[0218] Rating 3 Elemental Analysis and Evaluation (EDS)

[0219] Compositional analysis of the surface of the hydroxide ion-conducting separator was performed using an EDS analyzer (X-act, Oxford Instruments) to calculate the atomic ratio of Mg:Ti:Y:Al. The analysis was conducted as follows: 1) Images were acquired at an accelerating voltage of 20 kV and a magnification of 5,000x; 2) Three-point analysis was performed in point analysis mode with approximately 5 μm intervals; 3) Steps 1) and 2) were repeated once more; 4) The average value of the six points was calculated.

[0220] Rating 4 X-ray diffraction measurement

[0221] The crystal phase of the hydroxide ion-conducting separator was determined using an X-ray diffractometer (RINT TTR III, Rigaku Corporation) under the following conditions: voltage: 50 kV, current: 300 mA, and measurement range: 5–40°. The resulting XRD pattern was obtained. Furthermore, the interlayer distance of the layered crystal structure was determined using the 2θ peak corresponding to the peak derived from LDH-like compounds, according to the Bragg formula.

[0222] Rating 5 He measured

[0223] To evaluate the compactness of the hydroxide ion-conducting separator from the perspective of He permeability, a He permeability test was conducted as follows. First, a... Figure 14A and Figure 14BThe He transmittance measuring system 310 is shown. The He transmittance measuring system 310 is configured such that He gas from a gas cylinder filled with He gas is supplied to a sample holder 316 via a pressure gauge 312 and a flow meter 314 (digital flow meter), and is discharged from one side of a hydroxide ion conduction partition 318 held on the sample holder 316 to the other side.

[0224] The sample holder 316 has a structure including a gas supply port 316a, a sealed space 316b, and a gas outlet 316c, and is assembled as follows. First, an adhesive 322 is applied along the outer periphery of the hydroxide ion conducting separator 318, and it is mounted on a clamp 324 (made of ABS resin) with a central opening. Butyl rubber seals are provided at the upper and lower ends of the clamp 324 as sealing members 326a and 326b. Then, support members 328a and 328b (made of PTFE) with openings formed by flanges are used to clamp the sample holder from the outside of the sealing members 326a and 326b. In this way, the sealed space 316b is divided by the hydroxide ion conducting separator 318, the clamp 324, the sealing member 326a, and the support member 328a. The support members 328a and 328b are fastened to each other by using a screw fastening mechanism 330, so that He gas will not leak from any part other than the gas outlet 316c. The gas supply port 316a of the sample holder 316 assembled in this way is connected to a gas supply pipe 334 by means of a connector 332.

[0225] Next, He gas is supplied to the He transmittance measuring system 310 via gas supply pipe 334, allowing it to pass through the hydroxide ion conduction partition 318 held within the sample holder 316. During this time, the gas supply pressure and flow rate are monitored using pressure gauge 312 and flow meter 314. After He gas permeation for 1–30 minutes, the He transmittance is calculated. The He transmittance is calculated using the He gas permeation rate F (cm³) per unit time. 3 The parameters are: (r / min), the differential pressure P (atm) applied to the hydroxide ion-conducting separator during He gas permeation, and the membrane area S (cm²) during He gas permeation. 2 The permeation rate of He gas, F (cm³), is calculated using the formula F / (P×S). 3 The flow rate ( / min) is read directly from flow meter 314. Additionally, the differential pressure P is measured using gauge pressure from pressure gauge 312. It should be noted that He gas is supplied with a differential pressure P ranging from 0.05 to 0.90 atm.

[0226] Rating 6 Determination of ionic conductivity

[0227] use Figure 15The electrochemical measurement system shown is used to determine the conductivity of the hydroxide ion-conducting separator in the electrolyte as follows. The hydroxide ion-conducting separator sample S is clamped from both sides by silicone sealants 440 with a thickness of 1 mm and installed in a PTFE flanged electrolytic cell 442 with an inner diameter of 6 mm. As electrodes 446, a #100 mesh nickel mesh is installed in the electrolytic cell 442 in a cylindrical shape with a diameter of 6 mm, with a distance of 2.2 mm between electrodes. As the electrolyte 444, a 5.4 M KOH aqueous solution is filled into the electrolytic cell 442. The measurement is performed using an electrochemical measurement system (constant voltage / constant current-frequency response analyzer, Solartron 1287A and 1255B models) under conditions of a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV. The intercept of the real number axis is taken as the resistance of the hydroxide ion-conducting separator sample S. The same measurement is performed with a sample S without a hydroxide ion-conducting separator to determine the blank resistance. The difference between the resistance of the hydroxide ion-conducting separator sample S and the blank resistance is taken as the resistance of the hydroxide ion-conducting separator. The conductivity is then calculated using the resistance, thickness, and area of ​​the obtained hydroxide ion-conducting separator.

[0228] Rating 7 Alkali resistance evaluation

[0229] Prepare a 5.4M KOH aqueous solution containing zinc oxide at a concentration of 0.4M. Place 0.5 mL of the prepared KOH aqueous solution and a 2 cm square hydroxide ion-conducting separator sample into a sealed Teflon (registered trademark) container. Then, after maintaining the temperature at 90°C for one week (168 hours), remove the hydroxide ion-conducting separator sample from the sealed container. Dry the removed hydroxide ion-conducting separator sample at room temperature overnight. For the obtained sample, calculate the He transmittance using the same method as in Evaluation 5 to determine whether there is a change in He transmittance before and after alkali impregnation.

[0230] Rating 8 Evaluation of dendrite tolerance (cyclic testing)

[0231] To evaluate the effectiveness of the hydroxide ion-conducting separator in suppressing short circuits caused by zinc dendrites (dendrite tolerance), a cyclic test was conducted as follows. First, the positive electrode (containing nickel hydroxide and / or nickel hydroxide) and the negative electrode (containing zinc and / or zinc oxide) were each wrapped with non-woven fabric, and current extraction terminals were soldered onto them. The prepared positive and negative electrodes were then placed opposite each other, separated by the hydroxide ion-conducting separator, and sandwiched between a laminated film with a current extraction port. Three sides of the laminated film were heat-sealed. An electrolyte (a liquid obtained by dissolving 0.4 M zinc oxide in a 5.4 M KOH aqueous solution) was added to the resulting open-top single-cell container. The electrolyte was then fully permeated into the positive and negative electrodes using methods such as vacuuming. Finally, the remaining side of the laminated film was heat-sealed to create a simple, sealed single-cell battery. Using a charge-discharge apparatus (TOSCAT3100 manufactured by Toyo Systems, Ltd.), formation was performed on a simple, sealed single-cell battery at 0.1C charge and 0.2C discharge. Then, a 1C charge-discharge cycle was performed. While repeatedly performing charge-discharge cycles under the same conditions, the voltage between the positive and negative terminals was monitored using a voltmeter. The presence of a sharp voltage drop (specifically, a voltage drop of 5mV or more relative to the previously plotted voltage) caused by a short circuit between the positive and negative terminals was investigated, and the evaluation was performed according to the following criteria.

[0232] • No short circuit: No sharp voltage drop was observed during charging after 300 cycles.

[0233] • Short circuit: The sharp voltage drop mentioned above was observed during charging in less than 300 cycles.

[0234] Example B1 (refer to)

[0235] (1) Preparation of porous polymer substrate

[0236] A commercially available polyethylene microporous membrane with a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as a polymer porous substrate and cut into 2.0 cm × 2.0 cm pieces.

[0237] (2) Coating titanium dioxide sol onto a porous polymer substrate

[0238] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.) was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed as follows: the substrate was immersed in 100 ml of sol solution, then lifted vertically and dried at room temperature for 3 hours.

[0239] (3) Preparation of raw material aqueous solution

[0240] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at a concentration of 0.015 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. After stirring the resulting solution, urea / NO3 was added... - Urea, weighed at a ratio of 48 (molar ratio), is added to the solution, and further stirring is performed to obtain a raw material aqueous solution.

[0241] (4) Film formation using hydrothermal treatment

[0242] The raw material aqueous solution and the impregnated substrate are sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100ml, outer sleeve made of stainless steel). The substrate is then floated from the bottom of the Teflon (registered trademark) sealed container and fixed in place, vertically positioned so that the solution is in contact with both sides of the substrate. A hydrothermal treatment is then performed at 120°C for 24 hours, thereby forming an LDH-like compound on the surface and inside the substrate. After a specified time, the substrate is removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby forming an LDH-like compound within the pores of the porous substrate. This yields an LDH-like compound separator.

[0243] (5) Densification by roller pressing

[0244] The LDH-like compound separator described above was clamped using a pair of PET films (Lumirror manufactured by Toray Corporation, registered trademark, 40 μm thick) and rolled at a roller rotation speed of 3 mm / s, a roller heating temperature of 70°C, and a roller gap of 70 μm to obtain a further densified LDH-like compound separator.

[0245] (6) Evaluation Results

[0246] The obtained LDH-like compound separators were evaluated 1–8. The results are as follows.

[0247] - Evaluation 1: SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B1 is as follows: Figure 16A As shown.

[0248] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0249] - Evaluation 3: As a result of EDS elemental analysis, Mg and Ti, as constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg and Ti on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 2.

[0250] - Rating 4: Figure 16B The XRD pattern obtained in Example B1 is shown. A peak was observed near 2θ = 9.4° in the obtained XRD pattern. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is a shift of the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not officially called LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from polyethylene, which constitutes the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 0.94 nm.

[0251] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0252] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0253] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0254] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0255] Example B2 (refer to)

[0256] Except for the preparation of the raw material aqueous solution as described in (3) above and the setting of the hydrothermal treatment temperature in (4) above to 90°C, the LDH-like compound separator was prepared and evaluated in the same manner as in Example B1.

[0257] (Preparation of the raw material aqueous solution)

[0258] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at a concentration of 0.03 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. After stirring the resulting solution, urea / NO3 was added... - Urea, weighed in a ratio of 8 (molar ratio), is added to the solution and further stirred to obtain a raw material aqueous solution.

[0259] - Evaluation 1: SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B2 is as follows: Figure 17A As shown.

[0260] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0261] - Evaluation 3: As a result of EDS elemental analysis, Mg and Ti, as constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg and Ti on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 2.

[0262] - Rating 4: Figure 17B The XRD pattern obtained in Example B2 is shown. A peak was observed near 2θ = 7.2° in the obtained XRD pattern. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is a shift of the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not technically LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from polyethylene, which constitutes the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 1.2 nm.

[0263] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0264] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0265] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0266] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0267] Example B3 (refer to)

[0268] In addition to replacing (2) above by coating a porous polymer substrate with titanium dioxide-yttrium oxide sol, the LDH-like compound separator was fabricated and evaluated in the same manner as in Example B1.

[0269] (Coating titanium dioxide-yttrium oxide sol onto a porous polymer substrate)

[0270] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.) and yttrium sol were mixed at a Ti / Y (molar ratio) of 4. The mixed solution was then applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0271] - Evaluation 1: SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B3 is as follows: Figure 18A As shown.

[0272] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0273] - Evaluation 3: As a result of EDS elemental analysis, Mg, Ti, and Y, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Ti, and Y on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 2.

[0274] - Rating 4: Figure 18B The XRD pattern obtained in Example B3 is shown. A peak was observed near 2θ = 8.0° in the obtained XRD pattern. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is a shift of the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not technically LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from polyethylene, which constitutes the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 1.1 nm.

[0275] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0276] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0277] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0278] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0279] Example B4 (refer to)

[0280] In addition to replacing (2) above by coating a titanium dioxide-yttrium oxide-alumina sol onto a polymer porous substrate, the LDH-like compound separator was fabricated and evaluated in the same manner as in Example B1.

[0281] (Coating titanium dioxide-yttrium oxide-alumina sol onto a porous polymer substrate)

[0282] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.), yttrium sol, and amorphous alumina solution (Al-ML15, manufactured by Tagi Chemical Co., Ltd.) were mixed at a molar ratio of Ti / (Y+Al) = 2 and a molar ratio of Y / Al = 8. The mixed solution was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0283] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B4 are as follows: Figure 19A As shown.

[0284] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0285] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, and Y, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, and Y on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 2.

[0286] - Rating 4: Figure 19B The XRD pattern obtained in Example B4 is shown. In the obtained XRD pattern, a peak was observed near 2θ = 7.8°. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is obtained by shifting the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not officially called LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from the polyethylene constituting the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 1.1 nm.

[0287] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0288] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0289] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0290] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0291] Example B5 (refer to)

[0292] In addition to replacing (2) with coating titanium dioxide-yttrium oxide sol on a porous polymer substrate and preparing the raw material aqueous solution as described in (3) above, the LDH-like compound separator was prepared and evaluated in the same manner as in Example B1.

[0293] (Coating titanium dioxide-yttrium oxide sol onto a porous polymer substrate)

[0294] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.) and yttrium sol were mixed at a Ti / Y (molar ratio) of 18. The mixed solution was then applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0295] (Preparation of raw material aqueous solution)

[0296] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at a concentration of 0.0075 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml, and the resulting solution was stirred. The solution was then mixed with urea / NO3... - Urea, weighed at a ratio of 96 (molar ratio), is added to the solution, and further stirring is performed to obtain a raw material aqueous solution.

[0297] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B5 are as follows: Figure 20A As shown.

[0298] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0299] - Evaluation 3: As a result of EDS elemental analysis, Mg, Ti, and Y, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Ti, and Y on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 2.

[0300] - Rating 4: Figure 20B The XRD pattern obtained in Example B5 is shown. A peak was observed near 2θ = 8.9° in the obtained XRD pattern. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is a shift of the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not officially called LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from polyethylene, which constitutes the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 0.99 nm.

[0301] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0302] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0303] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0304] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0305] Example B6 (refer to)

[0306] Except for replacing (2) with coating titanium dioxide-alumina sol on a polymer porous substrate and preparing the raw material aqueous solution as described in (3) above, the LDH-like compound separator was prepared and evaluated in the same manner as in Example B1.

[0307] (Coating titanium dioxide-alumina sol onto a porous polymer substrate)

[0308] Titanium oxide sol solution (M6, manufactured by Tamaki Chemical Co., Ltd.) and amorphous alumina solution (Al-ML15, manufactured by Tamaki Chemical Co., Ltd.) were mixed at a Ti / Al (molar ratio) of 18. The mixed solution was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0309] (Preparation of raw material aqueous solution)

[0310] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.), yttrium nitrate n hydrate (Y(NO3)3·nH2O, manufactured by Fuji Thin Film & Television Co., Ltd.), and urea ((NH2)2CO, manufactured by Sigma-Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at 0.0015 mol / L and placed into a beaker. Then, yttrium nitrate n hydrate was weighed at 0.0075 mol / L and placed into the same beaker. Ion-exchanged water was added to bring the total volume to 75 ml, and the resulting solution was stirred. The solution was then mixed with urea / NO3... - Urea weighed in a ratio of 9.8 (molar ratio) is added to the solution, and further stirring is carried out to obtain a raw material aqueous solution.

[0311] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B6 are as follows: Figure 21A As shown.

[0312] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0313] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, and Y, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, and Y on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 2.

[0314] - Rating 4: Figure 21B The XRD pattern obtained in Example B6 is shown. A peak was observed near 2θ = 7.2° in the obtained XRD pattern. Typically, the (003) peak of LDH is observed at 2θ = 11–12°; therefore, it is assumed that the above peak is a shift of the (003) peak of LDH to a lower angle. This suggests that the above peak originates from a compound that, while not officially called LDH, is similar to LDH (i.e., an LDH-like compound). It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from polyethylene, which constitutes the porous substrate. Furthermore, the interlayer distance of the layered crystalline structure in the LDH-like compound is 1.2 nm.

[0315] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0316] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0317] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0318] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0319] Example B7 (refer to)

[0320] In addition to preparing the raw material aqueous solution as described in (3) above, the LDH-like compound separator was prepared and evaluated in the same manner as in Example B6.

[0321] (Preparation of raw material aqueous solution)

[0322] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.), yttrium nitrate n hydrate (Y(NO3)3·nH2O, manufactured by Fuji Thin Film & Television Co., Ltd.), and urea ((NH2)2CO, manufactured by Sigma-Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at 0.0075 mol / L and placed into a beaker. Then, yttrium nitrate n hydrate was weighed at 0.0075 mol / L and placed into the same beaker. Ion-exchanged water was added to bring the total volume to 75 ml, and the resulting solution was stirred. The solution was then mixed with urea / NO3... - Urea weighed in a ratio of 25.6 (molar ratio) is added to the solution, and further stirring is carried out to obtain a raw material aqueous solution.

[0323] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B7 are as follows: Figure 22 As shown.

[0324] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0325] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, and Y, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, and Y on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 2.

[0326] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0327] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0328] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0329] - Evaluation 8: As shown in Table 2, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0330] Example B8 (Compare)

[0331] Except for the following method of coating alumina sol instead of (2) above, the LDH partition was fabricated and evaluated in the same manner as in Example B1.

[0332] (Alumina sol is coated on a porous polymer substrate)

[0333] Amorphous alumina sol (Al-ML15, manufactured by Tagi Chemical Co., Ltd.) was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of amorphous alumina sol, then lifting it vertically and drying it at room temperature for 3 hours.

[0334] - Evaluation 1: The SEM image of the surface microstructure of the LDH partition (before rolling) obtained in Example B8 is as follows: Figure 23A As shown.

[0335] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the part of the LDH separator, excluding the porous substrate, is a compound with a layered crystalline structure.

[0336] - Evaluation 3: As a result of EDS elemental analysis, Mg and Al, which are constituent elements of LDH, were detected on the surface of the LDH separator. Furthermore, the atomic ratios of Mg and Al on the LDH separator surface calculated by EDS elemental analysis are shown in Table 2.

[0337] - Rating 4: Figure 23B The XRD pattern obtained in Example B8 is shown. Based on the peak near 2θ = 11.5° in the obtained XRD pattern, the LDH separator obtained in Example B8 was identified as LDH (hydrotalcite compound). This identification was performed using the diffraction peaks of LDH (hydrotalcite compound) described in JCPDS Card NO. 35-0964. It should be noted that the two peaks observed at 20 < 2θ° < 25° in the XRD pattern originate from the polyethylene constituting the porous substrate.

[0338] - Evaluation 5: As shown in Table 2, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0339] - Evaluation 6: As shown in Table 2, high ionic conductivity was confirmed.

[0340] - Evaluation 7: As a result of alkali impregnation at a high temperature of up to 90°C for one week, the He transmittance of 0.0 cm / min·atm in Evaluation 5 exceeded 10 cm / min·atm, thus indicating poor alkali resistance.

[0341] - Evaluation 8: As shown in Table 2, short circuits caused by zinc dendrites occurred in less than 300 cycles, indicating poor dendrite tolerance.

[0342] [Table 2]

[0343]

[0344] [Examples C1-C9]

[0345] Examples C1 to C9 shown below are reference examples related to LDH-like compound separators. It should be noted that the evaluation method for the LDH-like compound separators fabricated in the following examples is the same as that for Examples B1 to B8, except that the composition ratio (atomic ratio) of Mg:Al:Ti:Y:addition element M calculated in Evaluation 3 is used.

[0346] Example Cl (refer to)

[0347] (1) Preparation of porous polymer substrate

[0348] A commercially available polyethylene microporous membrane with a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as a polymer porous substrate and cut into 2.0 cm × 2.0 cm pieces.

[0349] (2) Coating titanium dioxide-yttrium oxide-alumina sol onto a polymer porous substrate

[0350] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.), yttrium sol, and amorphous alumina solution (Al-ML15, manufactured by Tagi Chemical Co., Ltd.) were mixed at a molar ratio of Ti / (Y+Al) = 2 and a molar ratio of Y / Al = 8. The mixed solution was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0351] (3) Preparation of raw material aqueous solution (I)

[0352] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate was weighed at a concentration of 0.015 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. After stirring the resulting solution, urea / NO3 was added... - Urea weighed at a ratio of 48 (molar ratio) is added to the solution, and further stirring is carried out to obtain the raw material aqueous solution (I).

[0353] (4) Film formation using hydrothermal treatment

[0354] The raw material aqueous solution (I) and the impregnated substrate are sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100ml, outer sleeve made of stainless steel). The substrate is then floated from the bottom of the Teflon (registered trademark) sealed container and fixed in a vertical position so that the solution is in contact with both sides of the substrate. A hydrothermal treatment is then performed at 120°C for 22 hours, thereby forming an LDH-like compound on the surface and inside the substrate. After the specified time, the substrate is removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby forming an LDH-like compound within the pores of the porous substrate.

[0355] (5) Preparation of raw material aqueous solution (II)

[0356] Indium sulfate n hydrate (In2(SO4)3·nH2O, manufactured by Fuji Thin Film and Kohden Chemical Co., Ltd.) was prepared as a raw material. Indium sulfate n hydrate was weighed at a concentration of 0.0075 mol / L and placed into a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0357] (6) Adding indium by impregnation treatment

[0358] The raw material aqueous solution (II) and the LDH-like compound separator obtained in (4) above were sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100 ml, outer sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) sealed container and fixed so that the solution was in contact with both sides of the substrate in a vertical position. Then, an immersion treatment was performed at 30°C for 1 hour, thereby adding indium. After a specified time, the substrate was removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby obtaining the LDH-like compound separator with added indium.

[0359] (7) Densification by roller pressing

[0360] The LDH-like compound separator described above was clamped using a pair of PET films (Lumirror manufactured by Toray Corporation, registered trademark, 40 μm thick) and rolled at a roller rotation speed of 3 mm / s, a roller heating temperature of 70°C, and a roller gap of 70 μm to obtain a further densified LDH-like compound separator.

[0361] (8) Evaluation Results

[0362] The obtained LDH-like compound separators were evaluated in various ways. The results are as follows.

[0363] - Evaluation 1: SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example C1 is as follows: Figure 24 As shown.

[0364] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0365] - Evaluation 3: As a result of EDS elemental analysis, Al, Ti, Y, and In, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the compositional ratios (atomic ratios) of Al, Ti, Y, and In on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 3.

[0366] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0367] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0368] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0369] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0370] Example C2 (refer to)

[0371] Except for changing the impregnation time to 24 hours in the above (6) method of adding indium by impregnation, the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0372] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0373] - Evaluation 3: As a result of EDS elemental analysis, Al, Ti, Y, and In, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the compositional ratios (atomic ratios) of Al, Ti, Y, and In on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 3.

[0374] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0375] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0376] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0377] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0378] Example C3 (refer to)

[0379] Except for replacing (2) above with coating titanium dioxide-yttrium oxide sol as described below, the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0380] (Coating titanium dioxide-yttrium oxide sol onto a porous polymer substrate)

[0381] Titanium oxide sol solution (M6, manufactured by Tamaki Chemical Co., Ltd.) and yttrium sol were mixed at a Ti / Y (molar ratio) of 2. The mixed solution was then applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0382] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0383] - Evaluation 3: As a result of EDS elemental analysis, Ti, Y, and In, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Ti, Y, and In on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 3.

[0384] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0385] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0386] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0387] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0388] Example C4 (refer to)

[0389] Except for the preparation of the raw material aqueous solution (II) as described in (5) and the addition of bismuth by impregnation treatment to replace (6) as described in (6), the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0390] (Preparation of raw material aqueous solution (II))

[0391] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was prepared as a raw material. Bismuth nitrate pentahydrate was weighed at a concentration of 0.00075 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0392] (Bismuth added through impregnation treatment)

[0393] The raw material aqueous solution (II) and the LDH-like compound separator obtained in (4) above were sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100 ml, outer sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) sealed container and fixed so that the solution was in contact with both sides of the substrate in a vertical position. Then, an impregnation treatment was performed at 30°C for 1 hour, thereby adding bismuth. After the specified time, the substrate was removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby obtaining the LDH-like compound separator with added bismuth.

[0394] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0395] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, Y, and Bi on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0396] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0397] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0398] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0399] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0400] Example C5 (refer to)

[0401] Except that the impregnation time was changed to 12 hours in the above-mentioned case of adding bismuth by impregnation treatment, the LDH-like compound separator was prepared and evaluated in the same manner as in Example C4.

[0402] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0403] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, Y, and Bi on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0404] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0405] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0406] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0407] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0408] Example C6 (refer to)

[0409] Except that the impregnation time was changed to 24 hours in the above-mentioned case of adding bismuth by impregnation treatment, the LDH-like compound separator was prepared and evaluated in the same manner as in Example C4.

[0410] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0411] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, Y, and Bi on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0412] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0413] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0414] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0415] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0416] Example C7 (refer to)

[0417] Except for the preparation of the raw material aqueous solution (II) as described in (5) and the addition of calcium by impregnation treatment to replace (6) as described in (6), the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0418] (Preparation of raw material aqueous solution (II))

[0419] Calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) was prepared as a raw material. 0.015 mol / L calcium nitrate tetrahydrate was weighed and placed in a beaker, and ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0420] (Calcium is added through impregnation treatment)

[0421] The raw material aqueous solution (II) and the LDH-like compound separator obtained in (4) above were sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100 ml, outer sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) sealed container and fixed so that the solution was in contact with both sides of the substrate in a vertical position. Then, an impregnation treatment was performed at 30°C for 6 hours, thereby adding calcium. After the specified time, the substrate was removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby obtaining the LDH-like compound separator with added calcium.

[0422] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0423] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Ca, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, Y, and Ca on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0424] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0425] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0426] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0427] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0428] Example C8 (refer to)

[0429] Except for the preparation of the raw material aqueous solution (II) as described in (5) and the addition of strontium by impregnation treatment to replace (6) as described in (6), the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0430] (Preparation of raw material aqueous solution (II))

[0431] Strontium nitrate (Sr(NO3)2) was prepared as a raw material. Strontium nitrate was weighed at a concentration of 0.015 mol / L and placed into a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0432] (Strontium added through impregnation treatment)

[0433] The raw material aqueous solution (II) and the LDH-like compound separator obtained in (4) above were sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100 ml, outer sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) sealed container and fixed so that the solution was in contact with both sides of the substrate in a vertical position. Then, an immersion treatment was performed at 30°C for 6 hours, thereby adding strontium. After the specified time, the substrate was removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby obtaining the LDH-like compound separator with added strontium.

[0434] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0435] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Sr, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Mg, Al, Ti, Y, and Sr on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0436] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0437] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0438] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0439] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0440] Example C9 (refer to)

[0441] Except for the preparation of the raw material aqueous solution (II) as described in (5) and the addition of barium by impregnation treatment to replace (6) as described in (6), the LDH-like compound separator was prepared and evaluated in the same manner as in Example C1.

[0442] (Preparation of raw material aqueous solution (II))

[0443] Barium nitrate (Ba(NO3)2) was prepared as a raw material. Barium nitrate was weighed at a concentration of 0.015 mol / L and placed in a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain an aqueous solution of the raw material (II).

[0444] (Barium is added through impregnation treatment)

[0445] The raw material aqueous solution (II) and the LDH-like compound separator obtained in (4) above were sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100 ml, outer sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) sealed container and fixed so that the solution was in contact with both sides of the substrate in a vertical position. Then, a immersion treatment was performed at 30°C for 6 hours, thereby adding barium. After the specified time, the substrate was removed from the sealed container, washed with ion-exchanged water, and dried at 70°C for 10 hours, thereby obtaining the LDH-like compound separator with added barium.

[0446] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator, except for the porous substrate, is a compound with a layered crystalline structure.

[0447] - Evaluation 3: As a result of EDS elemental analysis, Al, Ti, Y, and Ba, which are constituent elements of the LDH-like compound, were detected on the surface of the LDH-like compound separator. Furthermore, the atomic ratios of Al, Ti, Y, and Ba on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 3.

[0448] - Evaluation 5: As shown in Table 3, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0449] - Evaluation 6: As shown in Table 3, high ionic conductivity was confirmed.

[0450] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0451] - Evaluation 8: As shown in Table 3, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0452] [Table 3]

[0453]

[0454] [Examples D1 and D2]

[0455] Examples D1 and D2 shown below are reference examples related to LDH-like compound separators. It should be noted that the evaluation method for the LDH-like compound separators fabricated in the following examples is the same as that for Examples B1 to B8, except that the composition ratio (atomic ratio) of Mg:Al:Ti:Y:In calculated in Evaluation 3 is used.

[0456] Example D1 (refer to)

[0457] (1) Preparation of porous polymer substrate

[0458] A commercially available polyethylene microporous membrane with a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as a polymer porous substrate and cut into 2.0 cm × 2.0 cm pieces.

[0459] (2) Coating titanium dioxide-yttrium oxide-alumina sol onto a polymer porous substrate

[0460] Titanium oxide sol solution (M6, manufactured by Tagi Chemical Co., Ltd.), yttrium sol, and amorphous alumina solution (Al-ML15, manufactured by Tagi Chemical Co., Ltd.) were mixed at a molar ratio of Ti / (Y+Al) = 2 and a molar ratio of Y / Al = 8. The mixed solution was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0461] (3) Preparation of raw material aqueous solution

[0462] Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, manufactured by Kanto Chemical Co., Ltd.), indium sulfate n-hydrate (In2(SO4)3·nH2O, manufactured by Fuji Thin Film & Television Co., Ltd.), and urea ((NH2)2CO, manufactured by Sigma-Aldrich) were prepared as raw materials. Magnesium nitrate hexahydrate (0.0075 mol / L), indium sulfate n-hydrate (0.0075 mol / L), and urea (1.44 mol / L) were weighed and placed into a beaker. Ion-exchanged water was added to bring the total volume to 75 ml. The resulting solution was stirred to obtain an aqueous solution of the raw materials.

[0463] (4) Film formation using hydrothermal treatment

[0464] The raw material aqueous solution and the impregnated substrate are sealed together in a Teflon (registered trademark) sealed container (autoclave container, internal volume 100ml, outer sleeve made of stainless steel). The substrate is then floated from the bottom of the Teflon (registered trademark) sealed container and fixed in place, vertically positioned so that the solution is in contact with both sides of the substrate. Then, a hydrothermal treatment is performed at 120°C for 22 hours, thereby forming an LDH-like compound on the surface and inside the substrate. After a specified time, the substrate is removed from the sealed container, washed with deionized water, and dried at 70°C for 10 hours, thereby forming a functional layer containing an LDH-like compound and In(OH)3 within the pores of the porous substrate. This yields an LDH-like compound separator.

[0465] (5) Densification by roller pressing

[0466] The LDH-like compound separator described above was clamped using a pair of PET films (Lumirror manufactured by Toray Corporation, registered trademark, 40 μm thick) and rolled at a roller rotation speed of 3 mm / s, a roller heating temperature of 70°C, and a roller gap of 70 μm to obtain a further densified LDH-like compound separator.

[0467] (6) Evaluation Results

[0468] The obtained LDH-like compound separators were evaluated 1–8. The results are as follows.

[0469] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example D1 are as follows: Figure 25 As shown. Figure 25 As shown, cubic crystals were confirmed to exist on the surface of the LDH-like compound separator. Based on the EDS elemental analysis and X-ray diffraction results described later, the cubic crystals were presumed to be In(OH)3.

[0470] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator contains a compound with a layered crystalline structure.

[0471] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and In, which are constituent elements of the LDH-like compound and In(OH)3, were detected on the surface of the LDH-like compound separator. Furthermore, In, a constituent element of In(OH)3, was detected in the cubic crystals present on the surface of the LDH-like compound separator. It should be noted that the composition ratios (atomic ratios) of Mg, Al, Ti, Y, and In on the surface of the LDH-like compound separator calculated by EDS elemental analysis are shown in Table 4.

[0472] - Evaluation 4: Based on the peaks in the obtained XRD pattern, In(OH)3 was identified in the LDH-like compound separator. This identification was performed using the diffraction peaks of In(OH)3 recorded in JCPDS Card No. 01-085-1338.

[0473] - Evaluation 5: As shown in Table 4, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0474] - Evaluation 6: As shown in Table 4, high ionic conductivity was confirmed.

[0475] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0476] - Evaluation 8: As shown in Table 4, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0477] Example D2 (refer to)

[0478] Except for coating titanium dioxide-yttrium oxide sol as described above (2), the LDH-like compound separator was fabricated and evaluated in the same manner as in Example D1.

[0479] (Coating titanium dioxide-yttrium oxide sol onto a porous polymer substrate)

[0480] Titanium oxide sol solution (M6, manufactured by Tamaki Chemical Co., Ltd.) and yttrium sol were mixed at a Ti / Y (molar ratio) of 2. The mixed solution was then applied to the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed solution, then lifting it vertically and drying it at room temperature for 3 hours.

[0481] - Evaluation 1: SEM images of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example D2 are as follows: Figure 26As shown. Figure 26 As shown, cubic crystals were confirmed to exist on the surface of the LDH-like compound separator. Based on the EDS elemental analysis and X-ray diffraction results described later, the cubic crystals were presumed to be In(OH)3.

[0482] - Evaluation 2: Based on the results that the layered lattice stripes can be identified, it is confirmed that the LDH-like compound separator contains a compound with a layered crystalline structure.

[0483] - Evaluation 3: As a result of EDS elemental analysis, Mg, Ti, Y, and In, which are constituent elements of the LDH-like compound and In(OH)3, were detected on the surface of the LDH-like compound separator. Furthermore, In, a constituent element of In(OH)3, was detected in the cubic crystals present on the surface of the LDH-like compound separator. It should be noted that the atomic ratios of Mg, Ti, Y, and In on the surface of the LDH-like compound separator, calculated by EDS elemental analysis, are shown in Table 4.

[0484] - Evaluation 4: Based on the peaks in the obtained XRD pattern, In(OH)3 was identified in the LDH-like compound separator. This identification was performed using the diffraction peaks of In(OH)3 recorded in JCPDS Card No. 01-085-1338.

[0485] - Evaluation 5: As shown in Table 4, the extremely high density of He with a transmittance of 0.0 cm / min·atm was confirmed.

[0486] - Evaluation 6: As shown in Table 4, high ionic conductivity was confirmed.

[0487] - Evaluation 7: The He transmission rate after alkali impregnation was 0.0 cm / min·atm, the same as in Evaluation 5, confirming the excellent alkali resistance that the He transmission rate did not change even after alkali impregnation at a high temperature of up to 90°C for 1 week.

[0488] - Evaluation 8: As shown in Table 4, excellent dendrite tolerance was confirmed, with no short circuits caused by zinc dendrites even after 300 cycles.

[0489] [Table 4]

[0490]

Claims

1. A battery that utilizes a layered double hydroxide-like compound, i.e., an LDH-like compound, wherein, The battery comprises: a positive electrode, a negative electrode, an aqueous solution of an alkali metal hydroxide (i.e., an electrolyte), and an LDH-like compound configured to contact the electrolyte. The configuration involves dissolving a metal compound containing at least one metal element constituting the LDH-like compound in the electrolyte, thereby inhibiting the corrosion of the LDH-like compound by the electrolyte. The LDH-like compound is one of the following (a), (b), or (c). (a) A layered crystalline hydroxide and / or oxide containing Mg and at least one element selected from the group consisting of Ti, Y and Al, that contains at least Ti. (b) A layered crystalline hydroxide and / or oxide comprising (i) Ti, Y, and, as desired, Al and / or Mg, and (ii) at least one selected from the group consisting of In, Bi, Ca, Sr, and Ba, i.e., with added element M. (c) Hydroxides and / or oxides comprising Mg, Ti, Y, and, as desired, Al and / or In, having a layered crystalline structure. In (c), the LDH-like compound exists in the form of a mixture with In(OH)3.

2. The battery according to claim 1, wherein, The alkali metal hydroxide aqueous solution is a potassium hydroxide aqueous solution.

3. The battery according to claim 1, wherein, The metal element is dissolved in the electrolyte in the form of metal ions, hydroxides, and / or hydroxyl complexes.

4. The battery according to claim 1, wherein, The metal compound is pre-dissolved in the electrolyte.

5. The battery according to claim 1, wherein, The LDH-like compound contains Al, and the metal compound contains Al.

6. The battery according to claim 1, wherein, The metal compound is aluminum hydroxide and / or γ-alumina.

7. The battery according to claim 5, wherein, The concentration of Al in the electrolyte is above 0.1 mol / L.

8. The battery according to claim 5, wherein, The concentration of Al in the electrolyte is above 2.0 mol / L.

9. The battery according to claim 1, wherein, The battery has the LDH-like compound as a separator with hydroxide ion conductivity, which separates the positive electrode and the negative electrode.

10. The battery according to claim 9, wherein, In addition to the LDH-like compound, the separator also contains other materials.

11. The battery according to claim 10, wherein, The other materials are polymers.

12. The battery according to claim 10, wherein, The partition is densified to a degree that makes it impermeable to water and air.

13. The battery according to claim 9, wherein, The partition also has a porous substrate, and the LDH-like compound seals the pores of the porous substrate.

14. The battery according to claim 13, wherein, The porous substrate is composed of polymer materials.

15. The battery according to any one of claims 1 to 14, wherein, The negative electrode is coated with the LDH-like compound.

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