Ldh-like compound separator and zinc secondary battery

Abstract

Provided is a hydroxide ion-conducting separator excellent in alkali resistance and capable of further effectively suppressing short circuiting caused by zinc dendrites. The LDH compound separator includes a porous substrate made of a high molecular material and a layered double hydroxide (LDH) compound that seals the pores of the porous substrate. The average porosity of the central portion in the thickness direction of the LDH compound separator is lower than the average porosity of the portion near the surface of the LDH compound separator.

Description

TECHNICAL FIELD

[0001] The present application relates to a LDH-like compound separator and a zinc secondary battery. BACKGROUND

[0002] It is known that in a zinc secondary battery such as a nickel-zinc secondary battery, an air zinc secondary battery, and the like, during charging, metallic zinc is precipitated in dendritic form from the negative electrode, penetrates the interstices of a separator such as a nonwoven fabric, and reaches the positive electrode, as a result of which a short circuit is caused. Repeated occurrence of the short circuit caused by zinc dendrites can lead to a reduction in the charge-discharge life.

[0003] In order to address the above-described problems, a battery provided with a layered double hydroxide (LDH) separator that selectively permeates hydroxide ions and prevents penetration of zinc dendrites has been proposed. For example, Patent Literature 1 (International Publication No. 2013 / 118561) discloses that an LDH separator is provided between the positive electrode and the negative electrode in a nickel-zinc secondary battery. In addition, Patent Literature 2 (International Publication No. 2016 / 076047) discloses a separator structure provided with an LDH separator that is fitted or joined to a resin-made outer frame, and discloses that the LDH separator is provided with a high degree of compactness having a degree of impermeability to air and / or water. In addition, it is disclosed in this document that the LDH separator can be complexed with a porous substrate. Furthermore, Patent Literature 3 (International Publication No. 2016 / 067884) discloses various methods for forming an LDH compact film on the surface of a porous substrate to obtain a complex material (LDH separator). The method includes a process of uniformly adhering a starting point substance that can provide a starting point for the growth of crystals of LDH to the porous substrate, and performing hydrothermal treatment on the porous substrate in a raw material aqueous solution to form an LDH compact film on the surface of the porous substrate.

[0004] However, Patent Literature 4 (International Publication No. 2019 / 124214) discloses an LDH separator that includes a porous substrate made of a high molecular material, and a layered double hydroxide (LDH) that plugs the pores of the porous substrate, and the average porosity of the central portion in the thickness direction of the LDH separator is smaller than the average porosity of the portion near the surface of the LDH separator.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: International Publication No. 2013 / 118561

[0008] Patent Literature 2: International Publication No. 2016 / 076047

[0009] Patent Literature 3: International Publication No. 2016 / 067884

[0010] Patent Literature 4: International Publication No. 2019 / 124214 SUMMARY

[0011] In the case where a zinc secondary battery such as a nickel-zinc battery is configured using the LDH separator as described above, short circuit and the like caused by zinc dendrites can be prevented to some extent. However, it is desired that the effect of preventing dendrite short circuit be further improved.

[0012] The inventors of the present application have recently obtained the insight that, by employing a later-described LDH-like compound instead of the conventional LDH as a hydroxide ion conductor, it is possible to provide a hydroxide ion conductor separator (LDH-like compound separator) that is excellent in alkali resistance and can further effectively suppress short circuit caused by zinc dendrites. In addition, the inventors have obtained the insight that, by plugging the pores of a high-molecular porous base material with an LDH-like compound in a manner such that the average porosity of the central portion in the thickness direction is smaller than the average porosity of the surface vicinity portion, it is possible to provide an LDH-like compound separator that can further effectively suppress short circuit caused by zinc dendrites.

[0013] Accordingly, an object of the present application is to provide a hydroxide ion conductor separator that is superior to an LDH separator and is excellent in alkali resistance and can further effectively suppress short circuit caused by zinc dendrites.

[0014] According to one aspect of the present application, there is provided an LDH-like compound separator including a porous base material made of a high-molecular material, and an LDH-like compound that plugs the pores of the porous base material, wherein the average porosity of the central portion in the thickness direction of the LDH-like compound separator is smaller than the average porosity of the surface vicinity portion of the LDH-like compound separator.

[0015] According to another aspect of the present application, there is provided a zinc secondary battery that includes the LDH-like compound separator.

[0016] According to another aspect of the present application, there is provided a solid alkaline fuel cell that includes the LDH-like compound separator. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a cross-sectional diagram schematically showing the LDH-like compound separator of the present application.

[0018] Figure 2 is a cross-sectional diagram of a measurement device used in the dendrite short circuit confirmation test of Examples Al to A4.

[0019] Figure 3A is a conceptual diagram showing an example of a He permeation rate measurement system used in Examples Al to D2.

[0020] Figure 3B isFigure 3A A cross-sectional view of a sample holder and its periphery used in the measurement system shown.

[0021] Figure 4 A cross-sectional view of an electrochemical measurement system used in Examples Al to D2.

[0022] Figure 5A A cross-sectional FE-SEM image of the surface vicinity (a region 1 to 4 μm in depth from the surface) of the LDH separator produced in Example A3. In the figure, the gray region corresponds to the polymeric porous base material, the white region corresponds to the LDH, and the black region corresponds to the residual pores.

[0023] Figure 5B A cross-sectional FE-SEM image of the central portion of the LDH separator produced in Example A3. In the figure, the gray region corresponds to the polymeric porous base material, the white region corresponds to the LDH, and the black region corresponds to the residual pores.

[0024] Figure 6A A surface SEM image of the LDH compound separator produced in Example Bl.

[0025] Figure 6B X-ray diffraction results of the LDH compound separator produced in Example Bl.

[0026] Figure 7A A surface SEM image of the LDH compound separator produced in Example B2.

[0027] Figure 7B X-ray diffraction results of the LDH compound separator produced in Example B2.

[0028] Figure 8A A surface SEM image of the LDH compound separator produced in Example B3.

[0029] Figure 8B X-ray diffraction results of the LDH compound separator produced in Example B3.

[0030] Figure 9A A surface SEM image of the LDH compound separator produced in Example B4.

[0031] Figure 9B X-ray diffraction results of the LDH compound separator produced in Example B4.

[0032] Figure 10A A surface SEM image of the LDH compound separator produced in Example B5.

[0033] Figure 10B X-ray diffraction results of the LDH compound separator produced in Example B5.

[0034] Figure 11A This is a surface SEM image of the LDH-like compound separator fabricated in Example B6.

[0035] Figure 11B The X-ray diffraction results are for the LDH-like compound separator fabricated in Example B6.

[0036] Figure 12 This is a surface SEM image of the LDH-like compound separator fabricated in Example B7.

[0037] Figure 13A This is a surface SEM image of the LDH partition fabricated in Example B8 (Comparison).

[0038] Figure 13B The X-ray diffraction results are for the LDH partition fabricated in Example B8 (Comparison).

[0039] Figure 14 This is a surface SEM image of the LDH-like compound separator fabricated in Example C1.

[0040] Figure 15 This is a surface SEM image of the LDH-like compound separator fabricated in Example D1.

[0041] Figure 16 This is a surface SEM image of the LDH-like compound separator fabricated in Example D2. Detailed Implementation

[0042] LDH-like compound separator

[0043] like Figure 1 As shown in the schematic cross-sectional diagram, the LDH-like compound separator 10 of the present invention includes: a porous substrate 12 and a layered double hydroxide (LDH) compound 14. It should be noted that, in this specification, "LDH-like compound separator" refers to a separator containing an LDH-like compound and is defined as a component that selectively allows hydroxide ions to pass through by utilizing the hydroxide ion conductivity of the LDH-like compound. Furthermore, "LDH-like compound" refers to hydroxides and / or oxides that cannot be called LDH but have a layered crystalline structure similar to LDH, and is defined as a compound from which no peaks originating from LDH can be detected by X-ray diffraction. It should be noted that... Figure 1The region of the LDH-like compound 14 is not connected between the upper surface and the lower surface of the LDH-like compound separator 10, but this is because the two-dimensional depiction is in the form of a cross section, and in the case of considering three dimensions with depth, the region of the LDH-like compound 14 is connected between the upper surface and the lower surface of the LDH-like compound separator 10, whereby the hydroxide ion conductivity of the LDH-like compound separator 10 can be ensured. The porous base material 12 is made of a high molecular material, and the LDH-like compound 14 plugs the pores of the porous base material 12. However, the pores of the porous base material 12 are not completely plugged, and there are residual pores P (pores that are not plugged by the LDH-like compound). Due to the presence of the residual pores P, the LDH-like compound separator 10 can be evaluated using the average porosity. Also, the average porosity of the central portion 10a in the thickness direction of the LDH-like compound separator 10 is less than the average porosity of the surface vicinity portion 10b of the LDH-like compound separator 10. That is, the distribution of the residual pores P in the thickness direction of the LDH-like compound separator 10 of the present application has a density that is dense in the central portion 10a and sparse in the surface vicinity portion 10b. By plugging the pores of the high molecular porous base material 12 in such a way that the average porosity of the central portion 10a in the thickness direction is less than the average porosity of the surface vicinity portion 10b with the LDH-like compound 14, it is possible to provide an LDH-like compound separator 10 that can further effectively suppress short-circuiting due to zinc dendrites. That is, it is presumed that the penetration of zinc dendrites in conventional separators occurs in the following mechanism: (i) the zinc dendrites invade into the voids or defects contained in the separator, (ii) the dendrites grow and develop while expanding in the separator, (iii) finally, the dendrites penetrate the separator. In contrast, in the LDH-like compound separator 10 of the present application, the central portion 10a is dense and the surface vicinity portion 10b is sparse, and therefore the surface vicinity portion 10b, which has a higher average porosity than the central portion 10a, can function as a buffer layer for the invasion of dendrites, thereby restricting the growth and extension of zinc dendrites within the surface vicinity portion 10b. As a result, the extension of zinc dendrites in the thickness direction of the LDH-like compound separator 10 (particularly, the penetration of the central portion 10a) can be significantly suppressed, and therefore short-circuiting due to zinc dendrites can be further effectively suppressed. In particular, by using the LDH-like compound described later instead of the conventional LDH as the hydroxide ion conducting substance, it is possible to provide a hydroxide ion conducting separator (LDH-like compound separator) that is excellent in alkali resistance and can further effectively suppress short-circuiting due to zinc dendrites.

[0044] In addition, the LDH-like compound separator 10 of the present application has the desired ion conductivity required as a separator, based on the hydroxide ion conductivity of the LDH-like compound, and is also excellent in flexibility and strength. This is due to the flexibility and strength of the polymer porous base material 12 itself included in the LDH-like compound separator 10. That is, the LDH-like compound separator 10 is densified in a form in which the pores of the polymer porous base material 12 are sufficiently plugged with the LDH-like compound, and thus the polymer porous base material 12 and the LDH-like compound 14 are integrated as a highly composite material, so it can be said that the rigidity and brittleness due to the LDH-like compound 14 as a ceramic material are offset or mitigated by the flexibility and strength of the polymer porous base material 12.

[0045] As described above, in the LDH-like compound separator 10, the average porosity of the central portion 10a in the thickness direction is smaller than the average porosity of the surface vicinity portion 10b. Note that, in the present specification, the central portion 10a refers to a portion located at the center when the LDH-like compound separator 10 is divided into three in the thickness direction, and the surface vicinity portion 10b refers to a portion located on the surface side (i.e., a portion more outward than the central portion 10a) when the LDH-like compound separator 10 is divided into three in the thickness direction. It is preferable that the average porosity of the surface vicinity portion 10b be 3% or more and the average porosity of the central portion 10a be 2% or less, more preferable that the average porosity of the surface vicinity portion 10b be 3 to 15% and the average porosity of the central portion 10a be 1% or less, and further preferable that the average porosity of the surface vicinity portion 10b be 5 to 10% and the average porosity of the central portion 10a be 0.01 to 1%. If the average porosities of the central portion 10a and the surface vicinity portion 10b are within the above ranges, the growth of zinc dendrites can be further suppressed within the surface vicinity portion 10b, and thus the short circuit caused by zinc dendrites can be further effectively suppressed. In addition, a significantly high ion conductivity can be achieved, and the LDH-like compound separator 10 can exhibit sufficient functions as a hydroxide ion conductive separator. The average porosity can be measured as follows: a) cross-section polishing of the LDH-like compound separator is performed using a cross-section polisher (CP); b) cross-sectional images of the functional layer are obtained at two fields of view at a magnification of 50,000 times using an FE-SEM (field emission type scanning electron microscope); c) based on the image data of the obtained cross-sectional images, the porosities of the two fields of view are calculated using image inspection software (e.g., HDevelop, MVTec Software); and d) the average of the obtained porosities is calculated.

[0046] The ion conductivity of the LDH-like compound separator 10 is preferably 0.1 mS / cm or more, more preferably 1.0 mS / cm or more, further preferably 1.5 mS / cm or more, and particularly preferably 2.0 mS / cm or more. If it is within the above range, the LDH-like compound separator can exhibit sufficient function as a hydroxide ion-conducting separator. Since the higher the ion conductivity is, the more preferable it is, the upper limit value thereof is not particularly limited, and for example, it is 10 mS / cm. The ion conductivity is calculated based on the resistance of the LDH-like compound separator, the thickness of the LDH-like compound separator, and the area. The resistance of the LDH-like compound separator 10 can be determined by, for example, using an electrochemical measurement system (constant voltage / constant current-frequence response analyzer) to measure the LDH-like compound separator 10 immersed in a KOH aqueous solution of a prescribed concentration (for example, 5.4 M) at a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV, and taking the intercept on the real axis as the resistance of the LDH-like compound separator.

[0047] The LDH-like compound separator 10 is a separator containing a layered double hydroxide (LDH)-like compound 14, and separates a positive electrode plate and a negative electrode plate in a manner that enables conduction of hydroxide ions when assembled in a zinc secondary battery. That is, the LDH-like compound separator 10 exhibits a function as a hydroxide ion-conducting separator. The preferable LDH-like compound separator 10 has gas impermeability and / or water impermeability. In other words, the LDH-like compound separator 10 is preferably densified to the extent that it has gas impermeability and / or water impermeability. Note that, in the present specification, "having gas impermeability" means that, as described in Patent Documents 2 and 3, even if helium gas is brought into contact with one side of the measurement target in water at a differential pressure of 0.5 atm, no bubbles due to the helium gas are observed from the other side. Also, in the present specification, "having water impermeability" means that, as described in Patent Documents 2 and 3, water brought into contact with one side of the measurement target does not permeate to the other side. That is, the LDH-like compound separator 10 having gas impermeability and / or water impermeability means that the LDH-like compound separator 10 has high densification to the extent that it does not allow gas or water to permeate, and means that it is not a porous film having water permeability or gas permeability, or other porous materials. Thus, the LDH-like compound separator 10, due to its hydroxide ion conductivity, allows only hydroxide ions to selectively permeate, and can exhibit a function as a battery separator. Therefore, it is extremely effective to form a configuration that prevents short-circuiting between the positive and negative electrodes in a situation in which zinc dendrites generated during charging physically block the penetration of the separator. Since the LDH-like compound separator 10 has hydroxide ion conductivity, it can achieve efficient movement of hydroxide ions required between the positive electrode plate and the negative electrode plate, and can achieve charge and discharge reactions of the positive electrode plate and the negative electrode plate.

[0048] The He permeability per unit area of the LDH compound separator 10 is preferably 3.0 cm / min-atm or less, more preferably 2.0 cm / min-atm or less, and further preferably 1.0 cm / min-atm or less. A separator having a He permeability of 3.0 cm / min-atm or less can extremely effectively suppress the permeation of Zn (typically, the permeation of zinc ions or zincate ions) in an electrolyte solution. It is believed that, in principle, the separator of the present embodiment significantly suppresses the permeation of Zn in the above-described manner, and thus, in the case of being used in a zinc secondary battery, can effectively suppress the growth of zinc dendrites. The He permeability is measured by a procedure in which He gas is supplied to one face of the separator and allowed to permeate through the separator, and a procedure in which the He permeability is calculated and the density of the hydroxide ion-conducting separator is evaluated. The He permeability is calculated from the amount of permeated He gas F per unit time, the differential pressure P applied to the separator when the He gas permeates, and the membrane area S through which the He gas permeates, according to the formula F / (P x S). By thus evaluating the gas permeability using He gas, it is possible to evaluate whether or not a very high level of density is possessed, and as a result, it is possible to effectively evaluate a high density such that substances other than hydroxide ions (particularly, Zn that causes the growth of zinc dendrites) are not permeated (only permeated in an extremely small amount) as much as possible. This is because He gas has the smallest constituent unit among a wide variety of atoms or molecules that can constitute a gas, and has extremely low reactivity. That is, He does not form molecules, but constitutes He gas as He atom monomers. In this regard, since hydrogen gas is constituted by H2 molecules, the He atom monomer is smaller as a gas constituent unit. Since H2 gas is a flammable gas after all, it is relatively dangerous. Furthermore, by using the index of He gas permeability defined by the above formula, objective evaluation of the density can be easily performed regardless of differences in sample size and measurement conditions. Thus, it is possible to easily, safely, and effectively evaluate whether or not the separator has sufficiently high density that is suitable for a zinc secondary battery separator. The He permeability can be preferably measured in the order shown in Evaluation 5 of the following Examples.

[0049] In the LDH compound separator 10, the LDH compound 14 plugs the pores of the porous base material 12. Preferably, the LDH compound is (a), (b), or (c),

[0050] (a) a hydroxide and / or oxide having a layered crystal structure, which contains Mg, and at least one element containing Ti selected from the group consisting of Ti, Y, and Al,

[0051] (b) a hydroxide and / or oxide of a layered crystal structure comprising (i) Ti, Y, and Al and / or Mg as desired, and (ii) at least one additive element M selected from the group consisting of In, Bi, Ca, Sr, and Ba,

[0052] (c) a hydroxide and / or oxide of a layered crystal structure comprising Mg, Ti, Y, and Al and / or In as desired,

[0053] In the (c), the LDH-like compound is present in the form of a mixture with In(OH)3.

[0054] According to a preferred aspect (a) of the present application, the LDH-like compound 14 can be a hydroxide and / or oxide of a layered crystal structure comprising Mg, and at least one element containing Ti selected from the group consisting of Ti, Y, and Al. Thus, a typical LDH-like compound 14 is a composite hydroxide and / or composite oxide of Mg, Ti, Y as desired, and Al as desired. The above elements can be substituted by other elements or ions to the extent that the basic properties of the LDH-like compound 14 are not impaired, but the LDH-like compound 14 preferably does not contain Ni. For example, the LDH-like compound 14 can further contain Zn and / or K. According to this, the ion conductivity of the LDH-like compound separator 10 can be further improved.

[0055] The LDH-like compound 14 can be identified by X-ray diffraction. Specifically, when the surface of the LDH-like compound separator 10 is subjected to X-ray diffraction, a peak originating from the LDH-like compound is typically detected in the range of 5°≤ 2θ ≤ 10°, more typically in the range of 7°≤ 2θ ≤ 10°. As described above, an LDH is a substance having an alternating layered structure in which exchangeable anions and H2O as an intermediate layer exist between stacked hydroxide elementary layers. In this regard, when an LDH is measured by X-ray diffraction, a peak originating from the crystal structure of the LDH (i.e., the (003) peak of the LDH) is detected at a position of 2θ = 11-12°. In contrast, when the LDH-like compound 14 is measured by X-ray diffraction, a peak is typically detected in the above range shifted to the low-angle side from the above peak position of the LDH. In addition, using the 2θ corresponding to the peak originating from the LDH-like compound in X-ray diffraction, the interlayer distance of the layered crystal structure can be determined according to the Bragg formula. The interlayer distance of the layered crystal structure constituting the LDH-like compound 14 thus determined is typically 0.883-1.8 nm, more typically 0.883-1.3 nm.

[0056] The atomic ratio of Mg / (Mg+Ti+Y+Al) in the LDH-like compound 14, determined by energy dispersive X-ray analysis (EDS), is preferably 0.03 to 0.25, more preferably 0.05 to 0.2, with respect to the above-mentioned scheme (a) for the LDH-like compound separator 10. In addition, the atomic ratio of Ti / (Mg+Ti+Y+Al) in the LDH-like compound 14 is preferably 0.40 to 0.97, more preferably 0.47 to 0.94. Furthermore, the atomic ratio of Y / (Mg+Ti+Y+Al) in the LDH-like compound 14 is preferably 0 to 0.45, more preferably 0 to 0.37. Also, the atomic ratio of Al / (Mg+Ti+Y+Al) in the LDH-like compound 14 is preferably 0 to 0.05, more preferably 0 to 0.03. If within the above-mentioned ranges, the alkali resistance is more excellent, and the effect of suppressing short-circuiting due to zinc dendrites (i.e., dendrite resistance) can be more effectively achieved. However, with respect to the LDH separator, the basic composition of the LDH known heretofore can be represented by the general formula: M 2+ 1－x M 3+ x (OH)2A n－ x / n • mH2O (in the formula, M 2+ is a cation having a valence of 2, M 3+ is a cation having a valence of 3, A n－ is an anion having a valence of n, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the above-mentioned atomic ratios in the LDH-like compound 14 generally deviate from the above-mentioned general formula of the LDH. Therefore, it can be said that the LDH-like compound 14 in the present scheme generally has a composition ratio (atomic ratio) different from the LDH known heretofore. It should be noted that the EDS analysis is preferably performed as follows, i.e., using an EDS analysis device (e.g., X-act, manufactured by Oxford Instruments Co.), 1) an image is obtained at an acceleration voltage of 20 kV and a magnification of 5,000 times; 2) 3-point analysis is performed at intervals of about 5 μm in a point analysis mode; 3) the above-mentioned 1) and 2) are repeated once more; and 4) the average value of a total of 6 points is calculated.

[0057] According to another preferred aspect (b) of the present application, the LDH-like compound 14 can be a hydroxide and / or oxide of a layered crystal structure comprising (i) Ti, Y, and Al and / or Mg, as desired, and (ii) an additive element M. Thus, a typical LDH-like compound 14 is a complex hydroxide and / or complex oxide of Ti, Y, the additive element M, Al, as desired, and Mg, as desired. The additive element M is In, Bi, Ca, Sr, Ba, or a combination thereof. The above-mentioned elements can be substituted by other elements or ions to the extent that the essential properties of the LDH-like compound 14 are not impaired, however, the LDH-like compound 14 preferably does not contain Ni.

[0058] With respect to the LDH-like compound separator 10 according to the above aspect (b), the atomic ratio of Ti / (Mg+Al+Ti+Y+M) in the LDH-like compound 14 determined by energy dispersive X-ray analysis (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 14 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 14 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 14 is preferably 0 to 0.10, more preferably 0 to 0.02. Also, the atomic ratio of Al / (Mg+Al+Ti+Y+M) in the LDH-like compound 14 is preferably 0 to 0.05, more preferably 0 to 0.04. If within the above ranges, the alkali resistance is more excellent, and the effect of suppressing short-circuiting due to zinc dendrites (i.e., dendrite resistance) can be more effectively achieved. However, with respect to the LDH separator, the basic composition of the LDH known in the art can be expressed by the general formula: M 2+ 1－x M 3 + x (OH)2A n－ x / n • mH2O (in the formula, M 2+ is a cation having a valence of 2, M 3+ is a cation having a valence of 3, A 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 compound 14 generally deviate from the general formula for LDH described above. Therefore, it can be said that LDH-like compound 14 in this scheme generally has a different compositional ratio (atomic ratio) than conventional LDH. It should be noted that the EDS analysis is preferably performed as follows: using an EDS analysis apparatus (e.g., X-act, manufactured by Oxford Instruments), 1) an image is acquired at an accelerating voltage of 20 kV and a magnification of 5,000x; 2) in point analysis mode, with an interval of approximately 5 μm, a 3-point analysis is performed; 3) steps 1) and 2) are repeated once more; 4) the average value of the 6 points is calculated.

[0059] According to another preferred embodiment (c) of the invention, the LDH-like compound 14 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 14 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 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 properties of the LDH-like compound; however, the LDH-like compound preferably does not contain Ni. However, regarding the LDH separator, the basic composition of the 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－ (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 above general formula for LDH. Therefore, it can be said that the LDH-like compounds in this scheme generally have different compositional ratios (atomic ratios) than conventional LDHs.

[0060] The mixture of the above-described (c) contains not only the LDH-like compound but also In(OH)3(typically, the LDH-like compound and In(OH)3). By containing In(OH)3, the alkali resistance and dendrite resistance of the LDH-like compound separator 10 can be effectively improved. The proportion of In(OH)3in the mixture is preferably an amount that can improve the alkali resistance and dendrite resistance of the LDH-like compound separator 10 without impairing the hydroxide ion conductivity of the LDH-like compound separator 10, and is not particularly limited. In(OH)3may have a cubic crystal structure, or the crystal of In(OH)3may be surrounded by the LDH-like compound. In(OH)3can be identified by X-ray diffraction. The X-ray diffraction measurement can be preferably performed in the order given in the Examples described later.

[0061] As described above, the LDH-like compound separator 10 contains the LDH-like compound 14 and the porous base material 12 (typically, the porous base material 12 and the LDH-like compound 14), and the LDH-like compound plugs the pores of the porous base material, so that the LDH-like compound separator 10 exhibits hydroxide ion conductivity and gas impermeability (therefore, functions as an LDH-like compound separator that exhibits hydroxide ion conductivity). It is particularly preferable that the LDH-like compound 14 be embedded in the entire region in the thickness direction of the polymer porous base material 12. The thickness of the LDH-like compound separator is preferably 3 to 80 μm, more preferably 3 to 60 μm, and further preferably 3 to 40 μm.

[0062] The porous base material 12 is made of a high molecular material. The high molecular porous base material 12 has the following advantages: 1) flexibility (hence, it is difficult to crack even if it is thinned); 2) easy increase in porosity; 3) easy increase in conductivity (the reason is that the porosity can be increased and the thickness can be thinned); 4) easy manufacture and handling. In addition, the advantage brought by the flexibility of 1) above is flexibly used, and the following advantages are also obtained: 5) it is possible to easily bend or seal-join the LDH compound separator including the porous base material made of a high molecular material. As the high molecular material, polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE or the like), cellulose, nylon, polyethylene, and any combination of the above can be given. More preferably, from the viewpoint of being suitable for hot-pressing, polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE or the like), nylon, polyethylene, and any combination of the above can be given. Each of the above preferable materials has alkali resistance as resistance to the electrolyte of the battery. From the viewpoint of being excellent in hot water resistance, acid resistance, and alkali resistance, and being low in cost, a particularly preferable high molecular material is polyolefin such as polypropylene or polyethylene, and most preferably polypropylene or polyethylene. In the case where the porous base material is made of a high molecular material, it is particularly preferable that the LDH compound be embedded in the entire region in the thickness direction of the porous base material (for example, most of the pores inside the porous base material or almost all of the pores be filled with the LDH compound). As such a high molecular porous base material, a commercially available high molecular microporous film can be preferably used.

[0063] Manufacturing method

[0064] The method of producing the LDH compound separator 10 is not particularly limited, and can be produced by appropriately changing each condition (particularly, the LDH raw material composition) of the known production method of the LDH-containing functional layer and the composite material (for example, see Patent Documents 1 to 4). For example, (1) a porous base material is prepared; (2) a solution containing a titanium dioxide sol (or, further, a yttrium sol and / or an aluminum oxide sol) is applied to the porous base material and dried, thereby forming a titanium dioxide-containing layer; (3) the porous base material is immersed in a solution containing magnesium ions (Mg 2+ ) and urea (or, further, yttrium ions (Y 3+(3) adding urea to the raw material aqueous solution of (2) above; (4) subjecting the porous substrate to hydrothermal treatment in the raw material aqueous solution, so that the functional layer containing the LDH-like compound is formed on and / or in the porous substrate, whereby a functional layer containing the LDH-like compound and a composite material (i.e., an LDH-like compound separator) can be produced. In addition, it is considered that, due to the presence of urea in the above procedure (3), ammonia is generated in the solution by hydrolysis of urea, so that the pH value is increased, and the coexisting metal ions form hydroxides and / or oxides, whereby the LDH-like compound can be obtained.

[0065] In particular, in the case of producing a composite material (i.e., an LDH-like compound separator) in which the porous substrate 12 is composed of a polymer material and the LDH-like compound 14 is embedded in the entire region in the thickness direction of the porous substrate, it is preferable to perform the coating of the mixed sol solution on the substrate in the above (2) by a method that allows the mixed sol solution to penetrate into the entire or a large part of the inside of the substrate. Thereby, it is finally possible to fill most or almost all of the pores in the inside of the porous substrate with the LDH-like compound. As examples of the preferable coating method, there can be mentioned dip coating, filtration coating, etc., and dip coating is particularly preferable. By adjusting the number of times of coating by dip coating or the like, it is possible to adjust the amount of adhesion of the mixed sol solution. After the substrate on which the mixed sol solution has been coated by dip coating or the like is dried, the procedures of the above (3) and (4) are performed.

[0066] In the case where the porous substrate 12 is composed of a polymer material, it is preferable to perform a press treatment on the LDH-like compound separator obtained by the above method or the like. Thereby, it is possible to obtain an LDH-like compound separator having more excellent denseness. The press method can be, for example, roll pressing, uniaxial press, CIP (cold isostatic press), etc., and is not particularly limited, and roll pressing is preferable. By softening the polymer porous substrate, it is possible to sufficiently seal the pores of the porous substrate with the LDH-like compound, and in this regard, it is preferable to perform the press while heating. As the temperature at which the softening is sufficient, for example, in the case of polypropylene or polyethylene, it is preferable to perform the heating at 60 to 200°C. By performing the press such as roll pressing in this temperature range, it is possible to greatly reduce the residual pores of the LDH-like compound separator. As a result, it is possible to extremely highly densify the LDH-like compound separator, and thus it is possible to further effectively suppress the short circuiting caused by zinc dendrites. In the case of performing the roll pressing, by appropriately adjusting the roll gap and the roll temperature, it is possible to control the form of the residual pores, and thereby it is possible to obtain an LDH-like compound separator having a desired denseness.

[0067] Zinc secondary battery

[0068] The LDH compound separator of the present application is preferably used for a zinc secondary battery. Therefore, according to a preferred embodiment of the present application, there is provided a zinc secondary battery provided with the LDH compound separator. The typical zinc secondary battery is provided with a positive electrode, a negative electrode, and an electrolyte, and the positive electrode and the negative electrode are isolated from each other by the LDH compound separator. The zinc secondary battery of the present application is a secondary battery using zinc as the negative electrode and using an electrolyte (typically, an aqueous alkali metal hydroxide solution) without any particular limitation. Therefore, it can be a nickel-zinc secondary battery, a silver oxide-zinc secondary battery, a manganese oxide-zinc secondary battery, a zinc-air secondary battery, or other various alkaline zinc secondary batteries. For example, preferably, the positive electrode contains nickel hydroxide and / or nickel oxyhydroxide, so that the zinc secondary battery is formed as a nickel-zinc secondary battery. Alternatively, the positive electrode can be an air electrode, so that the zinc secondary battery is formed as a zinc-air secondary battery.

[0069] Solid alkaline fuel cell

[0070] The LDH compound separator of the present application can also be used for a solid alkaline fuel cell. That is, by using the LDH compound separator in which the pores of the high-molecular porous substrate are blocked with the LDH compound in such a manner that the average porosity of the central portion in the thickness direction is smaller than that of the surface vicinity, it is possible to provide a solid alkaline fuel cell capable of effectively suppressing the decrease in electromotive force caused by the permeation of fuel (e.g., methanol) to the air electrode side. This is because it is possible to utilize the hydroxide ion conductivity possessed by the LDH compound separator, and the permeation of fuel such as methanol through the LDH compound separator is effectively suppressed. Therefore, according to another preferred embodiment of the present application, there is provided a solid alkaline fuel cell provided with the LDH compound separator. The typical solid alkaline fuel cell according to this embodiment is provided with an air electrode supplied with oxygen, a fuel electrode supplied with liquid fuel and / or gaseous fuel, and an LDH compound separator interposed between the fuel electrode and the air electrode.

[0071] Other batteries

[0072] In addition to the nickel-zinc battery and the solid alkaline fuel cell, the LDH compound separator of the present application can also be used for, for example, a nickel-hydrogen battery. In this case, the LDH compound separator functions to impede the nitride shuttle (movement of nitric acid radicals between electrodes) which is the main cause of self-discharge of the battery. In addition, the LDH compound separator of the present application can also be used for a lithium battery (a battery in which metallic lithium is used as the negative electrode), a lithium ion battery (a battery in which carbon or the like is used as the negative electrode), or a lithium-air battery, etc.

[0073] Examples

[0074] The present application will be described more specifically using the following examples.

[0075] [Examples Al to A6]

[0076] Examples Al to A6 given below are reference examples or comparative examples related to LDH separators, however, the order of experiments and results in these examples are also roughly the same as for LDH compound separators. Note that the evaluation method of the LDH separator produced in the following examples is as follows.

[0077] Evaluation 1 : Identification of LDH Separator

[0078] The crystalline phase of the LDH separator was measured under measurement conditions of 50 kV in voltage, 300 mA in current value, and 10° to 70° in measurement range, using an X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation), to obtain an XRD pattern. The obtained XRD pattern was identified using the diffraction peaks of LDH (hydrotalcite compound) described in JCPDS Card No. 35-0964.

[0079] Evaluation 2 : Measurement of Thickness

[0080] The thickness of the LDH separator was measured using a micrometer. The thickness was measured at three points, and the average value thereof was used as the thickness of the LDH separator.

[0081] Evaluation 3 : Measurement of Average Porosity

[0082] The LDH separator was subjected to cross-section polishing using a cross-section polisher (CP), and cross-sectional images of the LDH separator were obtained at two fields of view at a magnification of 50,000 times by FE-SEM (ULTRA55 manufactured by Carl Zeiss). Based on the image data, the porosities of the two fields of view were calculated using image inspection software (HDevelop manufactured by MVTec Software), and the average value thereof was set as the average porosity of the LDH separator. Note that the measurement of the average porosity was performed for the surface vicinity of the LDH separator (a region of 1 to 4 μm in depth from the surface) and the central portion of the LDH separator, respectively.

[0083] Evaluation 4 : Continuous Charge Test

[0084] A continuous charge test was performed on the LDH separator produced in Example Al, and the results are shown in Table 1. Figure 2The measurement device 210 shown was subjected to an accelerated test in which zinc dendrites were continuously grown. Specifically, a rectangular container 212 of ABS resin was prepared, and a zinc electrode 214a and a copper electrode 214b were disposed in the container 212 at a distance of 0.5 cm from each other and in opposition. The zinc electrode 214a was a metal zinc plate, and the copper electrode 214b was a metal copper plate. On the other hand, an LDH separator 216 was mounted to a jig of ABS resin having an opening in the center by coating an epoxy resin-based adhesive along the outer periphery of the LDH separator, thereby forming an LDH separator structure including the LDH separator 216. At this time, the joint between the jig and the LDH separator was sufficiently sealed with the adhesive to ensure liquid tightness. Then, the LDH separator structure was disposed in the container 212 so that a first region 215a including the zinc electrode 214a and a second region 215b including the copper electrode 214b were separated in a manner that did not allow liquid to communicate with each other except at the LDH separator 216. At this time, the three edges of the outer periphery of the LDH separator structure (i.e., the three edges of the outer periphery of the jig of ABS resin) were adhered to the inner wall of the container 212 in a manner that ensured liquid tightness using the epoxy resin-based adhesive. That is, the joint between the separator structure including the LDH separator 216 and the container 212 was sealed in a manner that did not allow liquid to communicate. A 5.4 mol / L aqueous KOH solution was added to the first region 215a and the second region 215b as an alkaline aqueous solution 218 along with ZnO powder corresponding to the saturation solubility. The zinc electrode 214a and the copper electrode 214b were connected to the negative and positive electrodes of a constant current power supply, respectively, and a voltmeter was connected in parallel to the constant current power supply. In the first region 215a and the second region 215b, the water level of the alkaline aqueous solution 218 reached a level at which the entire region of the LDH separator 216 was immersed in the alkaline aqueous solution 218, and did not exceed the height of the LDH separator structure (including the jig). In the measurement device 210 thus constructed, a constant current of 20 mA / cm 2 was caused to flow continuously between the zinc electrode 214a and the copper electrode 214b for a maximum of 200 hours. During this period, the value of the voltage flowing between the zinc electrode 214a and the copper electrode 214b was monitored using the voltmeter, and it was confirmed whether or not a short circuit of zinc dendrites (a sharp drop in voltage) had occurred between the zinc electrode 214a and the copper electrode 214b. At this time, a case in which a short circuit did not occur for a period of 100 hours or more (or 200 hours or more) was determined to be "no short circuit", and a case in which a short circuit occurred for a period of less than 100 hours (or less than 200 hours) was determined to be "short circuit".

[0085] Evaluation 5 : He permeation test

[0086] In order to evaluate the compactness of the LDH separator from the viewpoint of He permeation, a He permeation test was performed as follows. First, a measurement device 210 was constructed as shown in FIG. 1. The measurement device 210 shown was subjected to an accelerated test in which zinc dendrites were continuously grown. Specifically, a rectangular container 212 of ABS resin was prepared, and a zinc electrode 214a and a copper electrode 214b were disposed in the container 212 at a distance of 0.5 cm from each other and in opposition. The zinc electrode 214a was a metal zinc plate, and the copper electrode 214b was a metal copper plate. On the other hand, an LDH separator 216 was mounted to a jig of ABS resin having an opening in the center by coating an epoxy resin-based adhesive along the outer periphery of the LDH separator, thereby forming an LDH separator structure including the LDH separator 216. At this time, the joint between the jig and the LDH separator was sufficiently sealed with the adhesive to ensure liquid tightness. Then, the LDH separator structure was disposed in the container 212 so that a first region 215a including the zinc electrode 214a and a second region 215b including the copper electrode 214b were separated in a manner that did not allow liquid to communicate with each other except at the LDH separator 216. At this time, the three edges of the outer periphery of the LDH separator structure (i.e., the three edges of the outer periphery of the jig of ABS resin) were adhered to the inner wall of the container 212 in a manner that ensured liquid tightness using the epoxy resin-based adhesive. That is, the joint between the separator structure including the LDH separator 216 and the container 212 was sealed in a manner that did not allow liquid to communicate. A 5.4 mol / L aqueous KOH solution was added to the first region 215a and the second region 215b as an alkaline aqueous solution 218 along with ZnO powder corresponding to the saturation solubility. The zinc electrode 214a and the copper electrode 214b were connected to the negative and positive electrodes of a constant current power supply, respectively, and a voltmeter was connected in parallel to the constant current power supply. In the first region 215a and the second region 215b, the water level of the alkaline aqueous solution 218 reached a level at which the entire region of the LDH separator 216 was immersed in the alkaline aqueous solution 218, and did not exceed the height of the LDH separator structure (including the jig). In the measurement device 210 thus constructed, a constant current of 20 mA / cm Figure 3Aand Figure 3B The He permeation rate measuring system 310 is shown. The He permeation rate 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 to the other side of an LDH separator 318 held on the sample holder 316.

[0087] The sample holder 316 has a structure including a gas supply port 316a, a sealed space 316b, and a gas discharge port 316c, and is assembled as follows. First, an adhesive 322 is applied along the outer periphery of the LDH separator 318, and is mounted to a jig 324 (ABS resin) having an opening portion in the center. At the upper end and the lower end of the jig 324, sealing members made of butyl rubber are provided as sealing members 326a, 326b, and further, support members 328a, 328b (PTFE) having an opening portion formed by a flange are clamped from the outside of the sealing members 326a, 326b. In this way, the sealed space 316b is divided by the LDH separator 318, the jig 324, the sealing members 326a, and the support members 328a. The support members 328a, 328b are fastened to each other by a fastening mechanism 330 using screws, so that He gas does not leak from portions other than the gas discharge port 316c. The gas supply tube 334 is connected to the gas supply port 316a of the sample holder 316 thus assembled by means of a connector 332.

[0088] Next, He gas is supplied into the He permeation rate measuring system 310 via the gas supply tube 334, and is made to permeate the LDH separator 318 held in the sample holder 316. At this time, the gas supply pressure and the flow rate are monitored by the pressure gauge 312 and the flow meter 314. After the permeation of He gas is performed for 1 to 30 minutes, the He permeation rate is calculated. With respect to the calculation of the He permeation rate, the permeation amount F (cm 3 / min) of He gas per unit time, the differential pressure P (atm) applied to the LDH separator at the time of permeation of He gas, and the membrane area S (cm 2 ) of the permeation of He gas, the He permeation rate is calculated according to the formula F / (P x S). The permeation amount F (cm 3 / min) of He gas is directly read from the flow meter 314. In addition, the differential pressure P is read from the pressure gauge 312 as the gage pressure. It should be noted that the He gas is supplied at a differential pressure P in the range of 0.05 to 0.90 atm.

[0089] Evaluation 6 Measurement of ion conductivity

[0090] Use Figure 4The electrochemical measurement system shown was used to measure the ion conductivity of the LDH separator in an electrolyte as follows. The LDH separator sample S was sandwiched with silicone sealants 440 of 1 mm in thickness on both sides and mounted in a flange-type electrolytic cell 442 made of PTFE with an inner diameter of 6 mm. As the electrodes 446, a nickel mesh of #100 mesh was installed in the electrolytic cell 442 in the form of a cylinder with a diameter of 6 mm, with an inter-electrode distance of 2.2 mm. As the electrolyte 444, a 5.4 M aqueous KOH solution was filled into the electrolytic cell 442. Using an electrochemical measurement system (constant voltage / constant current - frequency response analyzer, Solartron Model 1287A and Model 1255B), measurement was performed at a frequency range of 1 MHz to 0.1 Hz with an applied voltage of 10 mV, and the intercept on the real axis was taken as the resistance of the LDH separator sample S. Using the resistance of the LDH separator obtained, the thickness of the LDH separator, and the area, the conductivity was calculated.

[0091] Example Al (Comparative)

[0092] (1) Preparation of the polymeric porous substrate

[0093] A commercially available polyethylene microporous film having a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as the polymeric porous substrate, and cut to a size of 2.0 cm x 2.0 cm.

[0094] (2) Application of alumina / titania sol to the polymeric porous substrate

[0095] An amorphous alumina solution (Al-ML15, manufactured by Mito Chemical Co., Ltd.) and a titania sol solution (M6, manufactured by Mito Chemical Co., Ltd.) were mixed at Ti / Al (molar ratio) = 2 to prepare a mixed sol. The mixed sol was impregnated into the substrate prepared in (1) above by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the mixed sol, then lifting it vertically, and performing drying in a drying machine at 90°C for 5 minutes.

[0096] (3) Preparation of the raw material aqueous solution

[0097] As the raw materials, nickel nitrate hexahydrate (Ni(NO3)2-6H2O, manufactured by Kanto Chemical Co., Inc.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The nickel nitrate hexahydrate was weighed at 0.015 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. After the resulting solution was stirred, urea weighed at a urea / NO3 － (molar ratio) = 16 was added to the solution, and further stirred to obtain the raw material aqueous solution.

[0098] (4) Film formation based on hydrothermal treatment

[0099] The raw material aqueous solution and the substrate after dip coating were enclosed in a Teflon (registered trademark) -made airtight container (autoclave container, 100 ml in content volume, and the outside was a jacket made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made airtight container and fixed so as to be horizontally set in a manner that the solution contacted both sides of the substrate. Then, hydrothermal treatment was performed at a hydrothermal temperature of 120°C for 24 hours, whereby LDH was formed on the surface and inside of the substrate. After the prescribed time had elapsed, the substrate was taken out of the airtight container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby LDH was formed in the pores of the porous substrate. A composite material containing LDH was thus obtained.

[0100] (5) Densification based on rolling

[0101] The above composite material containing LDH was clamped with 1 pair of PET films (Lumirror (registered trademark), manufactured by Toray Corporation, thickness 40 μm), and rolling was performed at a roll rotation speed of 3 mm / s, a roll temperature of 110°C, and a roll gap of 60 μm, whereby an LDH separator was obtained.

[0102] (6) Evaluation results

[0103] The obtained LDH separator was subjected to evaluations 1 to 6. The result of evaluation 1: the LDH separator of this example was identified as LDH (hydrotalcite-like compound). The results of evaluations 2 to 6 are shown in Table 1. As shown in Table 1, no zinc dendrite short circuit occurred in the continuous charging time of 100 hours or less, but zinc dendrite short circuit occurred in the continuous charging time of less than 200 hours.

[0104] Examples A2 and A3 (Reference)

[0105] An LDH separator was produced in the same manner as in Example Al except that the drying temperature after the alumina / titania sol was impregnated was changed to the value given in Table 1, and was evaluated in the same manner. The result of evaluation 1: the LDH separator of this example was identified as LDH (hydrotalcite-like compound). The results of evaluations 2 to 6 are shown in Table 1. As shown in Table 1, no zinc dendrite short circuit occurred in the continuous charging time of 200 hours or more in both of Examples A2 and A3. In addition, Figure 5A and Figure 5B The cross-sectional FE-SEM images of the vicinity of the surface and the center of the LDH separator obtained in evaluation 3 of Example A3 are shown in Figs. 1 and 2, respectively.

[0106] Example A4 (Comparison)

[0107] Example A5 except that the above (5) roll-based densification was not performed. The LDH separator was produced and evaluated in the same manner as in Example Al. The result of Evaluation 1: The LDH separator of this example was identified as LDH (hydrotalcite-like compound). The results of Evaluations 2 to 6 are shown in Table 1. As shown in Table 1, in Evaluation 4, zinc dendrite short-circuiting occurred in less than 100 hours of continuous charging time.

[0108] Examples A5 and A6 (Reference)

[0109] The LDH separator was produced and evaluated in the same manner as in Example Al except for the following a) to c).

[0110] a) The drying temperature after the alumina / titania sol of the above (2) was impregnated was changed to the value given in Table 1.

[0111] b) As the raw material of the above (3), magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.) was used instead of nickel nitrate hexahydrate, and the magnesium nitrate hexahydrate was weighed at 0.03 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml, and after the obtained solution was stirred, urea weighed in a ratio of urea / NO3 － (molar ratio) = 8 was added to the solution, and further stirred to obtain the raw material aqueous solution.

[0112] c) The hydrothermal temperature of the above (4) was set to 90°C.

[0113] The result of Evaluation 1: The LDH separator of this example was identified as LDH (hydrotalcite-like compound). The results of Evaluations 2 to 6 are shown in Table 1. As shown in Table 1, in Example A5 and A6, zinc dendrite short-circuiting did not occur in more than 200 hours of continuous charging time.

[0114] [Table 1]

[0115]

[0116] [Examples B1 to B8]

[0117] Examples B1 to B7 given below are reference examples related to LDH-like compound separators, and on the other hand, Example B8 is a comparative example related to LDH separators. The LDH-like compound separator and the LDH separator are collectively referred to as hydroxide ion-conducting separators. Note that the evaluation method of the hydroxide ion-conducting separators produced in the following examples is as follows.

[0118] Evaluation 1 : Observation of surface microstructure

[0119] The surface microstructure of the hydroxide ion-conducting separator was observed using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL Ltd.) at an acceleration voltage of 10 to 20 kV.

[0120] Evaluation 2 STEM analysis of the layered structure

[0121] The layered structure of the hydroxide ion-conducting separator was observed using a scanning transmission electron microscope (STEM) (product name: JEM-ARM200F, manufactured by JEOL Ltd.) at an acceleration voltage of 200 kV.

[0122] Evaluation 3 Elemental analysis evaluation (EDS)

[0123] The composition of the surface of the hydroxide ion-conducting separator was analyzed using an EDS analysis device (device name: X-act, manufactured by Oxford Instruments Ltd.), and the composition ratio (atomic ratio) of Mg:Ti:Y:Al was calculated. The analysis was performed as follows, i.e., 1) an image was obtained at an acceleration voltage of 20 kV and a magnification of 5,000 times; 2) three-point analysis was performed at intervals of about 5 μm in a point analysis mode; 3) the above 1) and 2) were repeated once more; and 4) the average value of a total of six points was calculated.

[0124] Evaluation 4 X-ray diffraction measurement

[0125] The crystalline phase of the hydroxide ion-conducting separator was measured using an X-ray diffraction device (RINT TTR III, manufactured by Rigaku Corporation) under measurement conditions of a voltage of 50 kV, a current value of 300 mA, and a measurement range of 5 to 40°, and an XRD pattern was obtained. In addition, the interlayer distance of the layered crystalline structure was determined from the Bragg equation using 2θ corresponding to the peak derived from the LDH-like compound.

[0126] Evaluation 5 He permeation measurement

[0127] In order to evaluate the compactness of the hydroxide ion-conducting separator from the viewpoint of He permeability, a He permeation test was performed in the same order as in Evaluation 5 of Examples Al to A6.

[0128] Evaluation 6 Measurement of ion conductivity

[0129] Use Figure 4The electrochemical measurement system shown was used to measure the conductivity of the hydroxide ion-conducting separator in the electrolyte as follows. A hydroxide ion-conducting separator sample S was sandwiched with silicone sealants 440 of 1 mm in thickness on both sides and mounted in a flange-type electrolytic cell 442 made of PTFE having an inner diameter of 6 mm. As the electrodes 446, a nickel mesh of #100 mesh was installed in the electrolytic cell 442 in the form of a cylinder having a diameter of 6 mm, with an inter-electrode distance of 2.2 mm. As the electrolyte 444, a 5.4 M aqueous KOH solution was filled into the electrolytic cell 442. Using an electrochemical measurement system (constant voltage / constant current - frequency response analyzer, Model 1287A and Model 1255B, both manufactured by Solartron), the measurement was performed at a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV, and the intercept on the real axis was taken as the resistance of the hydroxide ion-conducting separator sample S. The same measurement was performed without the hydroxide ion-conducting separator sample S, and the blank resistance was determined. The difference between the resistance of the hydroxide ion-conducting separator sample S and the blank resistance was taken as the resistance of the hydroxide ion-conducting separator. Using the resistance of the hydroxide ion-conducting separator thus obtained, the thickness of the hydroxide ion-conducting separator, and the area, the conductivity was determined.

[0130] Evaluation 7 : Alkali resistance evaluation

[0131] An aqueous KOH solution of 5.4 M containing zinc oxide at a concentration of 0.4 M was prepared. The prepared aqueous KOH solution 0.5 mL and a hydroxide ion-conducting separator sample of 2 cm square in size were put in a Teflon (registered trademark) -made closed container. Then, after keeping at 90°C for 1 week (i.e., 168 hours), the hydroxide ion-conducting separator sample was taken out of the closed container. The taken-out hydroxide ion-conducting separator sample was dried at room temperature for 1 night. For the obtained sample, the He permeation rate was calculated using the same method as in Evaluation 5, and it was determined whether or not the He permeation rate changed before and after the alkali impregnation.

[0132] Evaluation 8 : Evaluation of dendrite resistance (cycling test)

[0133] To evaluate the effect of the hydroxide ion-conducting separator on the suppression of short-circuiting caused by zinc dendrites (dendrite resistance), a cycle test was performed as follows. First, the positive electrode (containing nickel hydroxide and / or nickel oxyhydroxide) and the negative electrode (containing zinc and / or zinc oxide) were each wrapped with a nonwoven fabric, and a current extraction terminal was welded. The thus-prepared positive electrode and negative electrode were opposed with the hydroxide ion-conducting separator interposed therebetween, clamped to a laminated film provided with a current extraction port, and the three edges of the laminated film were heat-sealed. An electrolyte solution (a liquid obtained by dissolving 0.4 M zinc oxide in a 5.4 M aqueous KOH solution) was added to the thus-obtained single cell container open at the top, and the electrolyte solution was allowed to sufficiently permeate the positive electrode and the negative electrode by vacuum suction or the like. Then, the remaining one edge of the laminated film was also heat-sealed, and a simple sealed single cell was produced. Using a charge-discharge device (TOSCAT 3100 manufactured by Toyo System Co., Ltd.), formation was performed on the simple sealed single cell by charging at 0.1 C and discharging at 0.2 C. Then, 1 C charge-discharge cycles were performed. While repeating the charge-discharge cycles under the same conditions, the voltage between the positive electrode and the negative electrode was monitored with a voltmeter, and the presence or absence of a sharp voltage decrease (specifically, a voltage decrease of 5 mV or more with respect to the previously plotted voltage) accompanying short-circuiting caused by zinc dendrites between the positive electrode and the negative electrode was investigated, and the evaluation was performed based on the following criteria.

[0134] • No short-circuit: no sharp voltage decrease as described above was observed in charging even after 300 cycles.

[0135] • Short-circuit: the sharp voltage decrease as described above was observed in charging less than 300 cycles.

[0136] Example Bl (Reference)

[0137] (1) Preparation of a polymeric porous substrate

[0138] A commercially available polyethylene microporous film having a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as a polymeric porous substrate, and cut into a size of 2.0 cm x 2.0 cm.

[0139] (2) Application of titanium dioxide sol to the polymeric porous substrate

[0140] The substrate prepared in the above (1) was coated with a titanium oxide sol solution (M6, manufactured by Muto Pure Chemicals Co., Ltd.) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the sol solution, and then lifted vertically, and dried at room temperature for 3 hours.

[0141] (3) Preparation of a raw aqueous solution

[0142] As a raw material, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.015 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. After the resulting solution was stirred, urea weighed at a ratio of urea / NO3 － (molar ratio) = 48 was added to the solution, and further stirring was performed to obtain a raw material aqueous solution.

[0143] (4) Film formation based on hydrothermal treatment

[0144] The raw material aqueous solution and the substrate after dip coating were enclosed in a Teflon (registered trademark) -made airtight container (autoclave container, inner volume 100 ml, outer side was a sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made airtight container and fixed so as to be vertically arranged in a manner that the solution contacted both surfaces of the substrate. Then, hydrothermal treatment was performed at a hydrothermal temperature of 120°C for 24 hours, whereby a LDH-like compound was formed on the surface and inside of the substrate. After the prescribed time, the substrate was taken out of the airtight container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby a LDH-like compound was formed in the pores of the porous substrate. A LDH-like compound separator was thus obtained.

[0145] (5) Densification based on rolling

[0146] A PET film (Lumirror (registered trademark), manufactured by Toray Co., Ltd., thickness 40 μm) was used to sandwich the above LDH-like compound separator, and rolling was performed at a roll rotation speed of 3 mm / s, a roll heating temperature of 70°C, and a roll gap of 70 μm, whereby a further densified LDH-like compound separator was obtained.

[0147] (6) Evaluation results

[0148] The obtained LDH-like compound separator was subjected to evaluations 1 to 8. The results are as follows.

[0149] - Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example Bl is shown in Fig. 1. Figure 6A

[0150] - Evaluation 2: It was confirmed that the part of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure from the result that a lattice stripe of a layer could be confirmed.

[0151] ​Evaluation 3: As a result of EDS elemental analysis, Mg and Ti, which are constituent elements of the LDH-like compound, were detected at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg and Ti at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0152] Evaluation 4: Figure 6B The XRD pattern obtained in Example B1 is shown in FIG. 2. In the obtained XRD pattern, a peak was observed near 2Θ = 9.4°. Generally, the (003) peak position of LDH is observed at 2Θ = 11 to 12°, and thus, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound similar to LDH (i.e., LDH-like compound) although it cannot be called LDH. Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from polyethylene constituting the porous base material. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound was 0.94 nm.

[0153] Evaluation 5: As shown in Table 2, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0154] Evaluation 6: As shown in Table 2, it was confirmed that the ion conductivity was high.

[0155] Evaluation 7: The He permeability after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for one week, which is excellent alkali resistance.

[0156] Evaluation 8: As shown in Table 2, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0157] Example B2 (Reference)

[0158] The production of the LDH-like compound separator and the evaluation were performed in the same manner as in Example B1 except that the production of the raw aqueous solution in the above (3) was performed as follows and the temperature of the hydrothermal treatment in the above (4) was set to 90°C.

[0159] (Production of the raw aqueous solution)

[0160] As raw materials, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.03 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml, and after the resulting solution was stirred, urea was added to the solution at a ratio of urea / NO3 － (molar ratio) = 8, and further stirring was performed to obtain a raw material aqueous solution.

[0161] - Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B2 is shown in FIG. 1. Figure 7A

[0162] - Evaluation 2: As a result of being able to confirm the lattice-like striations of the layers, it was confirmed that the part of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure.

[0163] - Evaluation 3: As a result of EDS elemental analysis, Mg and Ti, which are constituent elements of the LDH-like compound, were detected at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg and Ti at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0164] - Evaluation 4: Figure 7B The XRD pattern obtained in Example B2 is shown in FIG. 2. In the obtained XRD pattern, a peak was observed near 2Θ = 7.2°. Generally, the (003) peak position of LDH is observed at 2Θ = 11 to 12°, and therefore, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound that is not LDH but is similar to LDH (i.e., an LDH-like compound). Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from polyethylene constituting the porous substrate. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound was 1.2 nm.

[0165] - Evaluation 5: As shown in Table 2, a very high tightness of 0.0 cm / min-atm was confirmed.

[0166] - Evaluation 6: As shown in Table 2, a high ion conductivity was confirmed.

[0167] - Evaluation 7: The He permeation rate after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and an excellent alkali resistance was confirmed in that the He permeation rate did not change even if the alkali impregnation was performed at a high temperature of 90°C for one week. ​

[0168] Evaluation 8: As shown in Table 2, it was confirmed that excellent dendrite resistance was achieved in that no short circuit due to zinc dendrite was confirmed even after 300 cycles.

[0169] Example B3 (Reference)

[0170] Example B3 was produced in the same manner as in Example Bl except that the porous polymeric substrate was coated with a titanium oxide-yttrium oxide sol instead of (2) above. Evaluation

[0171] (Coating of a titanium oxide-yttrium oxide sol to a porous polymeric substrate)

[0172] The titanium oxide sol solution (M6, manufactured by Mitsuiki Chemical Co., Ltd.) and the yttrium sol were mixed at Ti / Y (mole ratio) = 4. The resulting mixed solution was coated onto the substrate prepared in (1) above by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, then it was lifted vertically, and dried at room temperature for 3 hours.

[0173] Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B3 is shown in FIG. 1. Figure 8A

[0174] Evaluation 2: It was confirmed from the result that the lattice fringes were observed that the portion of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure.

[0175] Evaluation 3: As a result of EDS elemental analysis, Mg, Ti, and Y, which are constituent elements of the LDH-like compound, were detected at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg, Ti, and Y at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0176] Evaluation 4: Figure 8B The XRD pattern obtained in Example B3 is shown in FIG. 2. In the obtained XRD pattern, a peak was observed near 20 = 8.0°. Generally, the (003) peak of LDH is observed at 20 = 11-12°, and therefore, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound that is not LDH but is similar to LDH (i.e., an LDH-like compound). Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from the polyethylene constituting the porous substrate. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound was 1.1 nm.

[0177] ​- Evaluation 5: As shown in Table 2, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0178] - Evaluation 6: As shown in Table 2, it was confirmed that the high ion conductivity.

[0179] - Evaluation 7: The He permeability after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, which is excellent alkali resistance.

[0180] - Evaluation 8: As shown in Table 2, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0181] Example B4 (Reference)

[0182] Example B4 was performed in the same manner as in Example Bl except that the titania-yttria-alumina sol was applied to the polymer porous substrate instead of the above (2).

[0183] (Application of titania-yttria-alumina sol to polymer porous substrate)

[0184] The titania sol solution (M6, manufactured by MTC Co., Ltd.), yttria sol, and amorphous alumina solution (Al-ML15, manufactured by MTC Co., Ltd.) were mixed at Ti / (Y+Al) (molar ratio) = 2 and Y / Al (molar ratio) = 8. The mixed solution was applied to the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, and then it was lifted vertically, and dried at room temperature for 3 hours.

[0185] - Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B4 is shown in Figure 9A .

[0186] - Evaluation 2: It was confirmed that the part of the LDH-like compound separator other than the polymer porous substrate was a compound having a layered crystal structure from the result that the lattice stripe of the layer could be confirmed.

[0187] - 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 at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, and Y at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0188] - Evaluation 4:Figure 9B The XRD pattern obtained in Example B4 is shown in FIG. 3. In the obtained XRD pattern, a peak was observed near 2Θ = 7.8°. Generally, the (003) peak position of LDH is observed at 2Θ = 11 to 12°, and therefore, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound similar to LDH (i.e., a LDH-like compound) although it cannot be called LDH. Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from polyethylene constituting the porous substrate. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound is 1.1 nm.

[0189] Evaluation 5: As shown in Table 2, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0190] Evaluation 6: As shown in Table 2, it was confirmed that the ion conductivity was high.

[0191] Evaluation 7: The He permeability after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for one week, which is excellent alkali resistance.

[0192] Evaluation 8: As shown in Table 2, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0193] Example B5 (Reference)

[0194] The production of the LDH-like compound separator and the evaluation were performed in the same manner as in Example Bl except that the following was performed instead of the above (2) in which the porous polymeric substrate was coated with the titanium dioxide-yttrium trioxide sol, and the following was performed for the production of the raw aqueous solution of the above (3).

[0195] (Coating of the porous polymeric substrate with the titanium dioxide-yttrium trioxide sol)

[0196] The titanium oxide sol solution (M6, manufactured by Mitsuwa Chemical Co., Ltd.) and the yttrium sol were mixed at Ti / Y (molar ratio) = 18. The obtained mixed solution was coated on the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, and then it was lifted vertically, and dried at room temperature for 3 hours.

[0197] (Production of the raw aqueous solution)

[0198] As raw materials, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.0075 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml, and the resulting solution was stirred. Urea weighed at a ratio of urea / NO3 － (molar ratio) = 96 was added to the solution, and further stirring was performed to obtain a raw material aqueous solution.

[0199] - Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B5 is shown in FIG. 1. Figure 10A

[0200] - Evaluation 2: As a result of being able to confirm the lattice-like striations of the layers, it was confirmed that the part of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure.

[0201] - Evaluation 3: As a result of EDS elemental analysis, Mg, Ti, and Y, which are constituent elements of the LDH-like compound, were detected at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg, Ti, and Y at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0202] - Evaluation 4: Figure 10B The XRD pattern obtained in Example B5 is shown in FIG. 2. In the obtained XRD pattern, a peak was observed near 2Θ = 8.9°. Generally, the (003) peak position of LDH is observed at 2Θ = 11 to 12°, and therefore, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound that is not LDH but is similar to LDH (i.e., an LDH-like compound). Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from polyethylene constituting the porous substrate. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound was 0.99 nm.

[0203] - Evaluation 5: As shown in Table 2, a very high tightness of 0.0 cm / min-atm was confirmed.

[0204] - Evaluation 6: As shown in Table 2, a high ion conductivity was confirmed.

[0205] - Evaluation 7: The He permeation rate after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and an excellent alkali resistance was confirmed in that the He permeation rate did not change even if the alkali impregnation was performed at a high temperature of 90°C for one week. ​

[0206] Evaluation 8: As shown in Table 2, it was confirmed that there was no short circuit due to zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0207] Example B6 (Reference)

[0208] The production of the LDH-like compound separator and the evaluation were performed in the same manner as in Example Bl, except that the coating of the titanium oxide-aluminum oxide sol onto the polymer porous substrate was performed instead of the above (2) and the production of the raw aqueous solution was performed as follows.

[0209] (Coating of titanium oxide-aluminum oxide sol onto polymer porous substrate)

[0210] The titanium oxide sol solution (M6, manufactured by Mitsuiki Chemical Co., Ltd.) and the amorphous aluminum oxide solution (Al-ML15, manufactured by Mitsuiki Chemical Co., Ltd.) were mixed at Ti / Al (molar ratio) = 18. The mixed solution was coated onto the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped into 100 ml of the mixed solution, and then it was lifted vertically, and dried at room temperature for 3 hours.

[0211] (Production of raw aqueous solution)

[0212] As raw materials, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.), yttrium nitrate n-hydrate (Y(N03)3-nH20, manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.), and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.0015 mol / L and put into a beaker. Further, the yttrium nitrate n-hydrate was weighed at 0.0075 mol / L and put into the above beaker, and ion exchange water was added thereto so that the total amount reached 75 ml, and the resulting solution was stirred. The urea weighed at a ratio of urea / NO3 － (molar ratio) = 9.8 was added to the solution, and further stirred to obtain the raw aqueous solution.

[0213] Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example B6 is shown in FIG. 6. Figure 11A

[0214] Evaluation 2: It was confirmed from the result that the lattice stripe of the layer could be confirmed that the part of the LDH-like compound separator other than the porous substrate was a compound of a layer crystal structure.

[0215] ​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 at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, and Y at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 2.

[0216] Evaluation 4: Figure 11B The XRD pattern obtained in Example B6 is shown in the middle. In the obtained XRD pattern, a peak was observed near 2Θ = 7.2°. Generally, the (003) peak position of LDH is observed at 2Θ = 11 to 12°, and thus, it is considered that the above peak is obtained by shifting the (003) peak of LDH to the low angle side. Therefore, it is suggested that the above peak is a peak derived from a compound similar to LDH (i.e., LDH-like compound) although it cannot be called LDH. Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from polyethylene constituting the porous base material. In addition, the interlayer distance of the layered crystal structure in the LDH-like compound was 1.2 nm.

[0217] Evaluation 5: As shown in Table 2, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0218] Evaluation 6: As shown in Table 2, it was confirmed that the ion conductivity was high.

[0219] Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that even if the alkali impregnation was performed at a high temperature of 90°C for one week, the He permeability did not change, which is excellent alkali resistance.

[0220] Evaluation 8: As shown in Table 2, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0221] Example B7 (Reference)

[0222] The production of the LDH-like compound separator and the evaluation were performed in the same manner as in Example B6 except that the production of the raw aqueous solution was performed as follows.

[0223] (Production of the raw aqueous solution)

[0224] As raw materials, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Kanto Chemical Co., Inc.), yttrium nitrate n hydrate (Y(N03)3-nH20, manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.), and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.0075 mol / L and put into a beaker. Further, the yttrium nitrate n hydrate was weighed at 0.0075 mol / L and put into the above beaker, and ion exchange water was added thereto so that the total amount reached 75 ml, and the resulting solution was stirred. Urea weighed at a ratio of urea / NO3 － (mole ratio) = 25.6 was added to the solution, and further stirring was performed to obtain a raw material aqueous solution.

[0225] Evaluation 1: The SEM image of the surface microstructure of the LDH compound separator (before rolling) obtained in Example B7 is shown in FIG. 1. Figure 12

[0226] Evaluation 2: As a result of being able to confirm the layered lattice fringes, it was confirmed that the portion of the LDH compound separator other than the porous substrate was a compound having a layered crystal structure.

[0227] Evaluation 3: As a result of EDS elemental analysis, at the surface of the LDH compound separator, Mg, Al, Ti, and Y, which are constituent elements of the LDH compound, were detected. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, and Y at the surface of the LDH compound separator calculated by EDS elemental analysis is shown in Table 2.

[0228] Evaluation 5: As shown in Table 2, an extremely high tightness of 0.0 cm / min-atm in He permeability was confirmed.

[0229] Evaluation 6: As shown in Table 2, a high ion conductivity was confirmed.

[0230] Evaluation 7: After alkali impregnation, the He permeability was also 0.0 cm / min-atm as in Evaluation 5, and an excellent alkali resistance in which the He permeability did not change even after alkali impregnation at a high temperature of 90°C for one week was confirmed.

[0231] Evaluation 8: As shown in Table 2, an excellent dendrite resistance in which no short circuit due to zinc dendrites occurred even after 300 cycles was confirmed.

[0232] Example B8 (Comparison)

[0233] Except that alumina sol was coated instead of the above (2), the production of the LDH separator and the evaluation were performed in the same manner as in Example B1. ​

[0234] (Alumina sol coating on a porous polymeric substrate)

[0235] The substrate prepared in (1) above was coated with amorphous alumina sol (Al-ML15, manufactured by Polypore Corporation) by dip coating. The dip coating was performed by immersing the substrate in 100 ml of the amorphous alumina sol, then lifting it vertically, and drying it at room temperature for 3 hours.

[0236] Evaluation 1: The SEM image of the surface microstructure of the LDH separator (before rolling) obtained in Example B8 is shown in FIG. 1. Figure 13A

[0237] Evaluation 2: From the result that the lattice fringes of the layer were confirmed, it was confirmed that the portion of the LDH separator other than the porous substrate was a compound having a layered crystal structure.

[0238] Evaluation 3: As a result of EDS elemental analysis, Mg and Al, which are the constituent elements of LDH, were detected at the surface of the LDH separator. In addition, the composition ratio (atomic ratio) of Mg and Al at the surface of the LDH separator calculated by EDS elemental analysis is shown in Table 2.

[0239] Evaluation 4: Figure 13B The XRD pattern obtained in Example B8 is shown in FIG. 2. From the peak around 2Θ = 11.5° in the obtained XRD pattern, the LDH separator obtained in Example B8 was identified as LDH (hydrotalcite-like compound). The identification was performed using the diffraction peaks of LDH (hydrotalcite-like compound) described in JCPDS Card No. 35-0964. Note that the two peaks observed at 20 < 2Θ° < 25 in the XRD pattern are peaks derived from the polyethylene constituting the porous substrate.

[0240] Evaluation 5: As shown in Table 2, a very high tightness of 0.0 cm / min-atm was confirmed for the He permeability.

[0241] Evaluation 6: As shown in Table 2, a high ion conductivity was confirmed.

[0242] Evaluation 7: As a result of alkali immersion at a high temperature of up to 90°C for one week, the He permeability of 0.0 cm / min-atm in Evaluation 5 exceeded 10 cm / min-atm, and thus it was determined that the alkali resistance was poor.

[0243] Evaluation 8: As shown in Table 2, short-circuiting due to zinc dendrites occurred in less than 300 cycles, and thus it was determined that the dendrite resistance was poor.

[0244] [Table 2]

[0245] ​

[0246] [Examples C1 to C9]

[0247] Examples C1 to C9 given below are reference examples related to the LDH compound separator. Note that the evaluation method of the LDH compound separator produced in the following examples is the same as that of Examples B1 to B8, except that the composition ratio (atomic ratio) of Mg:Al:Ti:Y:the added element M was calculated in Evaluation 3.

[0248] Example Cl (Reference)

[0249] (1) Preparation of the polymer porous substrate

[0250] A commercially available polyethylene microporous film having a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as the polymer porous substrate, and cut into a size of 2.0 cm x 2.0 cm.

[0251] (2) Application of titanium dioxide·yttrium trioxide·alumina sol to the polymer porous substrate

[0252] A titanium oxide sol solution (M6, manufactured by Mitsu Bishi Kasei Co., Ltd.), a yttrium sol, and an amorphous alumina solution (Al-ML15, manufactured by Mitsu Bishi Kasei Co., Ltd.) were mixed so as to have Ti / (Y+Al) (molar ratio) = 2 and Y / Al (molar ratio) = 8. The mixed solution was applied to the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, and then lifted vertically, and dried at room temperature for 3 hours.

[0253] (3) Production of the raw material aqueous solution (I)

[0254] As the raw materials, magnesium nitrate hexahydrate (Mg(NO3)2-6H2O, manufactured by Kanto Chemical Co., Inc.) and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed so as to have a concentration of 0.015 mol / L, and put into a beaker, and ion exchange water was added thereto so as to have a total amount of 75 ml. After the resulting solution was stirred, urea weighed so as to have a ratio of urea / NO3 － (molar ratio) = 48 was added to the solution, and further stirred to obtain the raw material aqueous solution (I).

[0255] (4) Film formation based on hydrothermal treatment

[0256] The raw material aqueous solution (I) and the impregnation-coated substrate were enclosed in a Teflon (registered trademark) -made airtight container (an autoclave container with a content volume of 100 ml, and a sheath made of stainless steel on the outside). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made airtight container and fixed so as to be vertically arranged in a manner that the solution contacted both sides of the substrate. Then, hydrothermal treatment was performed at a hydrothermal temperature of 120°C for 22 hours, whereby the LDH-like compound was formed on the surface and inside of the substrate. After the prescribed time had elapsed, the substrate was taken out of the airtight container, washed with ion-exchange water, and dried at a temperature of 70°C for 10 hours, whereby the LDH-like compound was formed inside the pores of the porous substrate.

[0257] (5) Preparation of the raw material aqueous solution (II)

[0258] As the raw material, indium sulfate n hydrate (In2(SO4)3-nH2O, manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.) was prepared. The indium sulfate n hydrate was weighed at 0.0075 mol / L and put into a beaker, and ion-exchange water was added thereto so that the total amount reached 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0259] (6) Addition of indium based on impregnation treatment

[0260] The raw material aqueous solution (II) and the LDH-like compound separator obtained in the above (4) were enclosed in a Teflon (registered trademark) -made airtight container (an autoclave container with a content volume of 100 ml, and a sheath made of stainless steel on the outside). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made airtight container and fixed so as to be vertically arranged in a manner that the solution contacted both sides of the substrate. Then, impregnation treatment was performed at 30°C for 1 hour, whereby indium was added. After the prescribed time had elapsed, the substrate was taken out of the airtight container, washed with ion-exchange water, and dried at a temperature of 70°C for 10 hours, whereby the LDH-like compound separator to which indium was added was obtained.

[0261] (7) Densification based on rolling

[0262] The LDH-like compound separator was sandwiched with a pair of PET films (Lumirror (registered trademark) manufactured by Toray Co., Ltd., thickness 40 μm), and rolled at a roll rotation speed of 3 mm / s, a roll heating temperature of 70°C, and a roll gap of 70 μm, whereby the LDH-like compound separator further densified was obtained.

[0263] (8) Evaluation results

[0264] The obtained LDH-like compound separator was subjected to various evaluations. The results were as follows.

[0265] Evaluation 1: The SEM image of the surface microstructure of the LDH-like compound separator (before rolling) obtained in Example C1 is shown in FIG. 1. Figure 14

[0266] Evaluation 2: The part other than the porous base material of the LDH-like compound separator was confirmed to be a compound having a layered crystal structure from the result that the lattice fringes of the layer could be confirmed.

[0267] 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 at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Al, Ti, Y, and In at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 3.

[0268] Evaluation 5: As shown in Table 3, a very high tightness of 0.0 cm / min atm in He permeability was confirmed.

[0269] Evaluation 6: As shown in Table 3, a high ion conductivity was confirmed.

[0270] Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min atm as in Evaluation 5, and an excellent alkali resistance was confirmed in that the He permeability did not change even with alkali impregnation at a high temperature of 90°C for 1 week.

[0271] Evaluation 8: As shown in Table 3, an excellent dendrite resistance was confirmed in that no short circuit due to zinc dendrites occurred even after 300 cycles.

[0272] Example C2 (Reference)

[0273] The production and evaluation of the LDH-like compound separator were carried out in the same manner as in Example C1 except that the time of the impregnation treatment in the addition of indium based on the impregnation treatment in the above (6) was changed to 24 hours.

[0274] Evaluation 2: The part other than the porous base material of the LDH-like compound separator was confirmed to be a compound having a layered crystal structure from the result that the lattice fringes of the layer could be confirmed.

[0275] 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 at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Al, Ti, Y, and In at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 3.

[0276] ​- Evaluation 5: As shown in Table 3, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0277] - Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0278] - Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, which is excellent alkali resistance.

[0279] - Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0280] Example C3 (Reference)

[0281] The production of the LDH compound separator and the evaluation were performed in the same manner as in Example Cl except that the titanium oxide-yttrium oxide sol was applied instead of the above (2).

[0282] (Application of titanium oxide-yttrium oxide sol to the porous polymer substrate)

[0283] The titanium oxide sol solution (M6, manufactured by Mitsu Boshu Co., Ltd.) and the yttrium sol were mixed at Ti / Y (molar ratio) = 2. The resulting mixed solution was applied to the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, and then it was lifted vertically, and dried at room temperature for 3 hours.

[0284] - Evaluation 2: It was confirmed that the part of the LDH compound separator other than the porous substrate was a compound having a layered crystal structure from the result that the layered lattice fringes could be confirmed.

[0285] - Evaluation 3: As a result of EDS elemental analysis, Ti, Y, and In, which are constituent elements of the LDH compound, were detected at the surface of the LDH compound separator. In addition, the composition ratio (atomic ratio) of Ti, Y, and In at the surface of the LDH compound separator calculated by EDS elemental analysis is shown in Table 3.

[0286] - Evaluation 5: As shown in Table 3, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0287] - Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0288] - Evaluation 7: The He permeability after alkali impregnation was 0.0 cm / min atm, the same as Evaluation 5, and it was confirmed that even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, the He permeability did not change, which is an excellent alkali resistance.

[0289] - Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is an excellent dendrite resistance.

[0290] Example C4 (Reference)

[0291] The production of the raw aqueous solution (II) of the above (5) was performed as follows and bismuth was added based on the impregnation treatment instead of the above (6) as follows, and the production of the LDH compound separator and the evaluation were performed as in Example Cl.

[0292] (Production of the raw aqueous solution (II))

[0293] As a raw material, bismuth nitrate pentahydrate (Bi (NO3)3·5H2O) was prepared. The bismuth nitrate pentahydrate was weighed at 0.00075 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. The resulting solution was stirred to obtain the raw aqueous solution (II).

[0294] (Addition of bismuth based on the impregnation treatment)

[0295] The raw aqueous solution (II) and the LDH compound separator obtained in the above (4) were sealed in a Teflon (registered trademark) airtight container (autoclave container, 100 ml in content volume, and a sheath made of stainless steel on the outside). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) airtight container and fixed so as to be vertically arranged in a manner that the solution and both surfaces of the substrate were in contact. Then, the impregnation treatment was performed for 1 hour at 30°C, whereby bismuth was added. After the prescribed time, the substrate was taken out of the airtight container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby the LDH compound separator to which bismuth was added was obtained.

[0296] - Evaluation 2: It was confirmed from the result that the lattice stripe of the layer could be confirmed that the part of the LDH compound separator other than the porous substrate was a compound of a layered crystal structure.

[0297] - Evaluation 3: As a result of EDS elemental analysis, at the surface of the LDH compound separator, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH compound, were detected. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, Y, and Bi at the surface of the LDH compound separator calculated by EDS elemental analysis is shown in Table 3.

[0298] - Evaluation 5: As shown in Table 3, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0299] - Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0300] - Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, which is excellent alkali resistance.

[0301] - Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0302] Example C5 (Reference)

[0303] The production of the LDH compound separator and the evaluation were performed as in Example C4 except that the time of the impregnation treatment was changed to 12 hours in addition to the addition of bismuth based on the above impregnation treatment.

[0304] - Evaluation 2: It was confirmed that the part of the LDH compound separator other than the porous substrate was a compound having a layered crystal structure from the result that the layered lattice stripe could be confirmed.

[0305] - Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH compound, were detected at the surface of the LDH compound separator. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, Y, and Bi at the surface of the LDH compound separator calculated by EDS elemental analysis is shown in Table 3.

[0306] - Evaluation 5: As shown in Table 3, it was confirmed that the He permeability was 0.0 cm / min-atm, which is extremely high densification.

[0307] - Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0308] - Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, which is excellent alkali resistance.

[0309] - Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0310] Example C6 (Reference)

[0311] Example C4 was repeated except that the time of the impregnation treatment was changed to 24 hours in the addition of bismuth based on the impregnation treatment described above.

[0312] Evaluation 2: The compound other than the porous base material of the LDH-like compound separator was confirmed to be a compound of a layered crystal structure from the result that the layered lattice fringes could be confirmed.

[0313] Evaluation 3: As a result of the EDS elemental analysis, Mg, Al, Ti, Y, and Bi, which are constituent elements of the LDH-like compound, were detected at the surface of the LDH-like compound separator. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, Y, and Bi at the surface of the LDH-like compound separator calculated by the EDS elemental analysis is shown in Table 3.

[0314] Evaluation 5: As shown in Table 3, the extremely high denseness of the He permeation rate of 0.0 cm / min-atm was confirmed.

[0315] Evaluation 6: As shown in Table 3, the high ion conductivity was confirmed.

[0316] Evaluation 7: The He permeation rate after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and the excellent alkali resistance that the He permeation rate did not change even with the alkali impregnation at a high temperature of 90°C for 1 week was confirmed.

[0317] Evaluation 8: As shown in Table 3, the excellent dendrite resistance that there was no short circuiting due to zinc dendrites even after 300 cycles was confirmed.

[0318] Example C7 (Reference)

[0319] Example C1 was repeated except that the production of the raw aqueous solution (II) of the above (5) was performed as follows and the addition of calcium based on the impregnation treatment instead of the above (6) was performed as follows.

[0320] (Production of raw aqueous solution (II))

[0321] As the raw material, calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) was prepared. The calcium nitrate tetrahydrate was weighed at 0.015 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. The obtained solution was stirred to obtain the raw aqueous solution (II).

[0322] (Addition of calcium based on impregnation treatment)

[0323] The raw material aqueous solution (II) and the LDH-like compound obtained in the above (4) were enclosed in a Teflon (registered trademark) -made closed container (an autoclave container with a content volume of 100 ml, and an outer side made of a stainless steel sleeve) with a separator. At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made closed container and fixed so as to be vertically arranged in a manner that the solution contacted both sides of the substrate. Then, immersion treatment was performed at 30°C for 6 hours, whereby calcium was added. After the prescribed time had elapsed, the substrate was taken out of the closed container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby a calcium-added LDH-like compound separator was obtained.

[0324] Evaluation 2: The result of being able to confirm the layered lattice fringes confirmed that the portion of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure.

[0325] Evaluation 3: As a result of EDS elemental analysis, at the surface of the LDH-like compound separator, Mg, Al, Ti, Y, and Ca, which are constituent elements of the LDH-like compound, were detected. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, Y, and Ca at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 3.

[0326] Evaluation 5: As shown in Table 3, a very high tightness of a He permeation rate of 0.0 cm / min-atm was confirmed.

[0327] Evaluation 6: As shown in Table 3, a high ion conductivity was confirmed.

[0328] Evaluation 7: The He permeation rate after alkali immersion was also 0.0 cm / min-atm as in Evaluation 5, and an excellent alkali resistance in which the He permeation rate did not change even with alkali immersion at a high temperature of 90°C for 1 week was confirmed.

[0329] Evaluation 8: As shown in Table 3, an excellent dendrite resistance in which short-circuiting due to zinc dendrites did not occur even after 300 cycles was confirmed.

[0330] Example C8 (Reference)

[0331] The production of the LDH-like compound separator and the evaluations were performed in the same manner as in Example C1, except that the production of the raw material aqueous solution (II) of the above (5) was performed as follows and strontium was added instead of the above (6) based on immersion treatment.

[0332] (Production of the raw material aqueous solution (II))

[0333] As a raw material, strontium nitrate (Sr(N03)2) was prepared. The strontium nitrate was weighed at 0.015 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. The resulting solution was stirred to obtain a raw material aqueous solution (II).

[0334] (Addition of strontium based on immersion treatment)

[0335] The raw material aqueous solution (II) and the LDH-like compound separator obtained in the above (4) were enclosed in a Teflon (registered trademark) -made closed container (autoclave container, 100 ml in content volume, and a jacket made of stainless steel on the outside). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made closed container and fixed so as to be vertically arranged in a manner such that the solution contacted both sides of the substrate. Then, immersion treatment was performed at 30°C for 6 hours, whereby strontium was added. After the prescribed time had elapsed, the substrate was taken out of the closed container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby a strontium-added LDH-like compound separator was obtained.

[0336] Evaluation 2: As a result of being able to confirm the layered lattice fringes, it was confirmed that the portion of the LDH-like compound separator other than the porous substrate was a compound having a layered crystal structure.

[0337] Evaluation 3: As a result of EDS elemental analysis, at the surface of the LDH-like compound separator, Mg, Al, Ti, Y, and Sr, which are constituent elements of the LDH-like compound, were detected. In addition, the composition ratio (atomic ratio) of Mg, Al, Ti, Y, and Sr at the surface of the LDH-like compound separator calculated by EDS elemental analysis is shown in Table 3.

[0338] Evaluation 5: As shown in Table 3, it was confirmed that the He permeation rate was as high as 0.0 cm / min-atm.

[0339] Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0340] Evaluation 7: The He permeation rate after alkali immersion was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that even if alkali immersion was performed at a high temperature of 90°C for 1 week, the He permeation rate did not change, which is excellent alkali resistance.

[0341] Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuiting due to zinc dendrites even after 300 cycles, which is excellent dendrite resistance.

[0342] Example C9 (Reference)

[0343] Example C2 The production of the layered LDH compound separator and the evaluation were carried out in the same manner as in Example C1, except that the production of the raw material aqueous solution (II) was carried out as follows and barium was added based on the impregnation treatment instead of (6) as follows.

[0344] (Production of the raw material aqueous solution (II))

[0345] As the raw material, barium nitrate (Ba(N03)2) was prepared. Barium nitrate was weighed at 0.015 mol / L and put into a beaker, and ion exchange water was added thereto so that the total amount reached 75 ml. The resulting solution was stirred to obtain the raw material aqueous solution (II).

[0346] (Addition of barium based on the impregnation treatment)

[0347] The raw material aqueous solution (II) and the layered LDH compound separator obtained in (4) above were enclosed in a Teflon (registered trademark) -made closed container (autoclave container, 100 ml in content volume, and the outside was a sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made closed container and fixed so as to be vertically arranged in a manner that the solution and both sides of the substrate were in contact. Then, the impregnation treatment was carried out at 30°C for 6 hours, whereby barium was added. After the prescribed time had elapsed, the substrate was taken out of the closed container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby the layered LDH compound separator to which barium was added was obtained.

[0348] Evaluation 2: As a result of being able to confirm the layered lattice fringes, it was confirmed that the portion of the layered LDH compound separator other than the porous substrate was a compound having a layered crystal structure.

[0349] Evaluation 3: As a result of EDS elemental analysis, at the surface of the layered LDH compound separator, Al, Ti, Y, and Ba, which are constituent elements of the layered LDH compound, were detected. In addition, the composition ratio (atomic ratio) of Al, Ti, Y, and Ba at the surface of the layered LDH compound separator calculated by EDS elemental analysis is shown in Table 3.

[0350] Evaluation 5: As shown in Table 3, it was confirmed that the He permeation rate was 0.0 cm / min-atm, which is extremely high denseness.

[0351] Evaluation 6: As shown in Table 3, it was confirmed that the ion conductivity was high.

[0352] Evaluation 7: The He permeation rate after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that even if the alkali impregnation was carried out at a high temperature of 90°C for 1 week, the He permeation rate did not change, which is excellent alkali resistance.

[0353] - Evaluation 8: As shown in Table 3, it was confirmed that there was no short circuit due to zinc dendrites even after 300 cycles, and this is excellent dendrite resistance.

[0354] [Table 3]

[0355]

[0356] [Examples D1 and D2]

[0357] Examples D1 and D2 given below are reference examples related to the LDH compound separator. Note that the evaluation method of the LDH compound separator produced in the following examples is the same as in Examples B1 to B8, except that the composition ratio (atomic ratio) of Mg:Al:Ti:Y:In is calculated in Evaluation 3.

[0358] Example Dl (Reference)

[0359] (1) Preparation of the polymer porous substrate

[0360] A commercially available polyethylene microporous film having a porosity of 50%, an average pore diameter of 0.1 μm, and a thickness of 20 μm was prepared as the polymer porous substrate, and cut into a size of 2.0 cm x 2.0 cm.

[0361] (2) Application of titanium dioxide · yttrium sesquioxide · alumina sol to the polymer porous substrate

[0362] A titanium oxide sol solution (M6, manufactured by Muto Pure Chemicals Co., Ltd.), a yttrium sol, and an amorphous alumina solution (Al-ML15, manufactured by Muto Pure Chemicals Co., Ltd.) were mixed at Ti / (Y+Al) (molar ratio) = 2 and Y / Al (molar ratio) = 8. The mixed solution was applied to the substrate prepared in the above (1) by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, and then lifted vertically, and dried at room temperature for 3 hours.

[0363] (3) Production of the raw material aqueous solution

[0364] As the raw materials, magnesium nitrate hexahydrate (Mg(N03)2-6H20, manufactured by Showa Denko K.K.), indium sulfate n hydrate (In2(S04)3-nH20, manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.), and urea ((NH2)2CO, manufactured by Sigma Aldrich) were prepared. The magnesium nitrate hexahydrate was weighed at 0.0075 mol / L, the indium sulfate n hydrate was weighed at 0.0075 mol / L, and the urea was weighed at 1.44 mol / L, and they were put into a beaker, and ion exchange water was added so that the total amount reached 75 ml. The obtained solution was stirred to obtain the raw material aqueous solution.

[0365] (4) Film formation based on hydrothermal treatment

[0366] The raw material aqueous solution and the substrate after dip coating were enclosed in a Teflon (registered trademark) -made airtight container (autoclave container, inner volume 100 ml, outer side is a sleeve made of stainless steel). At this time, the substrate was floated from the bottom of the Teflon (registered trademark) -made airtight container and fixed so as to be vertically set in a manner that the solution contacted both sides of the substrate. Then, hydrothermal treatment was performed at a hydrothermal temperature of 120°C for 22 hours, whereby a LDH-like compound was formed on the surface and inside of the substrate. After the prescribed time, the substrate was taken out of the airtight container, washed with ion exchange water, and dried at a temperature of 70°C for 10 hours, whereby a functional layer containing a LDH-like compound and In(OH)3was formed in the pores of the porous substrate. In this way, a LDH-like compound separator was obtained.

[0367] (5) Densification based on rolling

[0368] A PET film (Lumirror (registered trademark), manufactured by Toray Corporation, thickness 40 μm) was used to sandwich the above LDH-like compound separator, and rolling was performed at a roller rotation speed of 3 mm / s, a roller heating temperature of 70°C, and a roll gap of 70 μm, whereby a further densified LDH-like compound separator was obtained.

[0369] (6) Evaluation results

[0370] The obtained LDH-like compound separator was subjected to evaluations 1 to 8. The results are as follows.

[0371] - Evaluation 1 : The SEM image of the surface microstructure of the LDH-like compound separator obtained in Example D1 (before rolling) is shown in FIG. 1. As shown in FIG. 1, a cubic crystal was confirmed to exist on the surface of the LDH-like compound separator. From the results of the EDS elemental analysis and X-ray diffraction measurement described later, it was inferred that the cubic crystal was In(OH)3. Figure 15 Figure 15 - Evaluation 2 : From the result that a layered lattice stripe could be confirmed, it was confirmed that the LDH-like compound separator contained a compound having a layered crystal structure.

[0372] - Evaluation 2 : From the result that a layered lattice stripe could be confirmed, it was confirmed that the LDH-like compound separator contained a compound having a layered crystal structure.

[0373] ​- Evaluation 3: As a result of EDS elemental analysis, Mg, Al, Ti, Y, and In, which are constituent elements of the pseudo-LDH compound and In(OH)3, were detected at the surface of the pseudo-LDH compound separator. In addition, In, which is a constituent element of In(OH)3, was detected in the cubic crystals present on the surface of the pseudo-LDH compound separator. Note that the composition ratios (atomic ratios) of Mg, Al, Ti, Y, and In on the surface of the pseudo-LDH compound separator calculated by EDS elemental analysis are shown in Table 4.

[0374] - Evaluation 4: In(OH)3was identified as being present in the pseudo-LDH compound separator from the peaks of the obtained XRD pattern. This identification was performed using the diffraction peaks of In(OH)3described in JCPDS Card No. 01-085-1338.

[0375] - Evaluation 5: As shown in Table 4, a very high tightness of 0.0 cm / min-atm was confirmed for the He permeability.

[0376] - Evaluation 6: As shown in Table 4, a high ion conductivity was confirmed.

[0377] - Evaluation 7: The He permeability after alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and an excellent alkali resistance was confirmed in that the He permeability did not change even after 1 week of alkali impregnation at a high temperature of 90°C.

[0378] - Evaluation 8: As shown in Table 4, an excellent dendrite resistance was confirmed in that no short circuiting due to zinc dendrites occurred even after 300 cycles.

[0379] Example D2 (Reference)

[0380] Example D2 was produced and evaluated in the same manner as in Example Dl, except that the titanium dioxide-yttrium sesquioxide sol was applied to the high polymer porous substrate instead of (2) above.

[0381] (Application of titanium dioxide-yttrium sesquioxide sol to high polymer porous substrate)

[0382] The titanium oxide sol solution (M6, manufactured by Mitsuwa Chemical Co., Ltd.) and yttrium sol were mixed at Ti / Y (mole ratio) = 2. The resulting mixed solution was applied to the substrate prepared in (1) above by dip coating. The dip coating was performed in such a manner that the substrate was dipped in 100 ml of the mixed solution, then lifted vertically, and dried at room temperature for 3 hours.

[0383] - Evaluation 1: The SEM image of the surface microstructure of the pseudo-LDH compound separator (before rolling) obtained in Example D2 is shown in Fig. 2. As shown in Fig. 2, the surface of the pseudo-LDH compound separator was covered with a large number of cubic crystals. Figure 16 - Evaluation 2: The SEM image of the surface microstructure of the pseudo-LDH compound separator (after rolling) obtained in Example D2 is shown in Fig. 3. As shown in Fig. 3, the cubic crystals were crushed and the surface of the pseudo-LDH compound separator was covered with a large number of crushed crystals.Figure 16 As shown, it was confirmed that cubic crystals existed on the surface of the LDH compound separator. According to the results of the EDS elemental analysis and the X-ray diffraction measurement described later, it was presumed that the cubic crystals were In(OH)3.

[0384] Evaluation 2: It was confirmed that the LDH compound separator contained a compound having a layered crystal structure, based on the result that layered lattice fringes could be confirmed.

[0385] Evaluation 3: As a result of the EDS elemental analysis, Mg, Ti, Y, and In, which are constituent elements of the LDH compound and In(OH)3, were detected at the surface of the LDH compound separator. In addition, In, which is a constituent element of In(OH)3, was detected in the cubic crystals existing on the surface of the LDH compound separator. Note that the composition ratios (atomic ratios) of Mg, Ti, Y, and In at the surface of the LDH compound separator calculated by the EDS elemental analysis are shown in Table 4.

[0386] Evaluation 4: In(OH)3was identified to exist in the LDH compound separator based on the peaks of the obtained XRD pattern. The identification was performed using the diffraction peaks of In(OH)3described in JCPDS Card No. 01-085-1338.

[0387] Evaluation 5: As shown in Table 4, it was confirmed that the He permeability was as high as 0.0 cm / min-atm.

[0388] Evaluation 6: As shown in Table 4, it was confirmed that the ion conductivity was high.

[0389] Evaluation 7: The He permeability after the alkali impregnation was also 0.0 cm / min-atm as in Evaluation 5, and it was confirmed that the He permeability did not change even if the alkali impregnation was performed at a high temperature of 90°C for 1 week, which is an excellent alkali resistance.

[0390] Evaluation 8: As shown in Table 4, it was confirmed that there was no short circuit caused by zinc dendrites even after 300 cycles, which is an excellent dendrite resistance.

[0391] [Table 4]

[0392]

Claims

1. A LDH-like compound separator comprising: A porous substrate made of a high molecular material, and a layered double hydroxide compound, i.e., an LDH compound, which seals the pores of the porous substrate, The LDH compound separator is characterized in that The average porosity of the central portion in the thickness direction of the LDH compound separator is less than the average porosity of the surface vicinity portion of the LDH compound separator.

2. The LDH compound separator according to claim 1, characterized in that The LDH compound is (a), (b), or (c) below, (a) a hydroxide and / or oxide of a layered crystal structure containing Mg, and at least one element containing Ti selected from the group consisting of Ti, Y, and Al, (b) a hydroxide and / or oxide of a layered crystal structure containing (i) Ti, Y, and Al and / or Mg as desired, and (ii) at least one element M selected from the group consisting of In, Bi, Ca, Sr, and Ba, (c) a hydroxide and / or oxide of a layered crystal structure containing Mg, Ti, Y, and Al and / or In as desired, In the (c), the LDH compound is present in the form of a mixture with In(OH)3.

3. The LDH compound separator according to claim 1, characterized in that The average porosity of the surface vicinity portion is 3% or more, and the average porosity of the central portion is 2% or less.

4. The LDH compound separator according to any one of claims 1 to 3, characterized in that The average porosity of the surface vicinity portion is 3 to 15%, and the average porosity of the central portion is 1% or less.

5. The LDH compound separator according to any one of claims 1 to 3, characterized in that The LDH compound is embedded in the entire region in the thickness direction of the porous substrate.

6. The LDH compound separator according to any one of claims 1 to 3, characterized in that The He permeability per unit area of the LDH compound separator is 3.0 cm / atm min or less.

7. The LDH compound separator according to any one of claims 1 to 3, characterized in that The ion conductivity of the LDH compound separator is 2.0 mS / cm or more.

8. The LDH compound separator according to any one of claims 1 to 3, characterized in that The high molecular material is selected from the group consisting of polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin, cellulose, nylon, and polyethylene.

9. The LDH compound separator according to any one of claims 1 to 3, characterized in that The LDH compound separator is composed of the porous substrate and the LDH compound.

10. A zinc secondary battery, characterized by comprising the LDH compound separator according to any one of claims 1 to 9.

11. A solid alkaline fuel cell, characterized by comprising the LDH compound separator according to any one of claims 1 to 9. ​ ​

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