JP6864758B2 - Functional layers and composite materials containing layered double hydroxides - Google Patents

Description

The present invention relates to functional layers and composite materials containing layered double hydroxides.

Layered double hydroxides (hereinafter, also referred to as LDH), while the stacked hydroxide base layer is a substance having exchangeable anions and H _{2 O} as an intermediate layer, a catalyst Ya taking advantage of its features It is used as an adsorbent, a dispersant in a polymer for improving heat resistance, and the like.

LDH is also attracting attention as a material that conducts hydroxide ions, and its addition to the electrolyte of alkaline fuel cells and the catalyst layer of zinc-air batteries is also being studied. In particular, in recent years, the use of LDH as a solid electrolyte separator for alkaline secondary batteries such as nickel-zinc secondary batteries and zinc-air secondary batteries has been proposed, and an LDH-containing functional layer suitable for such separator applications is provided. Composite materials are known. For example, in Patent Document 1 (International Publication No. 2015/0986010), a composite comprising a porous base material and an LDH-containing functional layer having no water permeability formed on and / or in the porous base material. The material is disclosed, and the LDH-containing functional layer has a general formula: M ²⁺ _1-x M ³⁺ _x (OH) _{2 An} ^- _{x / n} · mH ₂ O (in the formula, M ²⁺ is Mg ^2+, etc. 2). valent ^{cation, M 3+} is a trivalent cation ^{Al 3+, etc., a n-is OH} -, _CO ^{3 2-} or the like of an n-valent anion, n represents an integer of 1 or more, x is 0. It is described that it contains LDH represented by (1 to 0.4, and m is 0 or more). Since the LDH-containing functional layer disclosed in Patent Document 1 is so dense that it does not have water permeability, zinc dendrite is a barrier to practical use of an alkaline zinc secondary battery when used as a separator. It can prevent the progress and the invasion of carbon dioxide from the air electrode in the zinc-air battery.

However, the electrolytic solution of an alkaline secondary battery (for example, a metal-air battery or a nickel-zinc battery) to which LDH is applied is required to have high hydroxide ion conductivity, and therefore, a strongly alkaline KOH having a pH of about 14 is required. It is desirable that an aqueous solution be used. Therefore, LDH is desired to have a high degree of alkali resistance such that it hardly deteriorates even in such a strongly alkaline electrolytic solution. In this regard, in Patent Document 2 (International Publication No. 2016/051934), a metal compound containing a metal element (for example, Al) corresponding to ^{the above-mentioned general formula M 2+} and / or M ^{3+ is dissolved in an electrolytic solution.} An LDH-containing battery has been proposed, which is configured to suppress erosion of LDH by an electrolytic solution.

International Publication No. 2015/098610 International Publication No. 2016/05/1934

The present inventors have previously composed the hydroxide basic layer of LDH with a predetermined element or ion containing Ni, Al, Ti and OH groups, thereby exhibiting not only ionic conductivity but also good alkali resistance. It has been found that a functional layer containing −Al—Ti—LDH can be provided. At that time, in the evaluation of alkali resistance, a potassium hydroxide aqueous solution to which a predetermined amount of zinc oxide was added was used as an electrolytic solution composition assuming practical use in a zinc secondary battery. However, it has been found that when an attempt is made to eliminate zinc oxide from the electrolytic solution or reduce the zinc oxide concentration in order to improve the battery characteristics, the alkali resistance of Ni-Al-Ti-LDH having the above composition can be lowered. Therefore, LDH that exhibits alkali resistance to a high-performance battery electrolytic solution such as an aqueous solution of potassium hydroxide that does not contain zinc oxide or has a reduced zinc oxide content, that is, LDH that is more excellent in alkali resistance is desired.

The present inventors have recently obtained a finding that an LDH-containing functional layer having excellent alkali resistance can be provided by incorporating Y in a Ni-Al-Ti-LDH-containing functional layer at a predetermined atomic ratio.

Therefore, an object of the present invention is to provide an LDH-containing functional layer having excellent alkali resistance and a composite material provided with the LDH-containing functional layer.

According to the present invention, the following aspects are provided.
[Item 1]
A functional layer containing a layered double hydroxide, wherein the layered double hydroxide contains Ni, Ti and Al, and the functional layer further contains Y, and the atomic ratio of Y / Al is 0.5 or more. Is a functional layer.
[Item 2]
(I) The layered double hydroxide contains Ni, Ti, Al and Y, and / or (ii) The layered double hydroxide contains Ni, Ti and Al, and the functional layer is the layered double hydroxide. Item 2. The functional layer according to Item 1, which contains a Y compound different from hydroxide.
[Item 3]
Item 2. The functional layer according to Item 1 or 2, wherein the Y / Al atomic ratio is 1 or more.
[Item 4]
Item 2. The functional layer according to Item 1 or 2, wherein the Atomic ratio of Y / Al is 2 to 8.
[Item 5]
Item 2. The functional layer according to any one of Items 1 to 4, wherein the functional layer has an atomic ratio of Ti / (Y + Al) of 0.1 to 8.
[Item 6]
Item 2. The functional layer according to any one of Items 1 to 5, wherein the layered double hydroxide contains Ni, Ti, Al and Y.
[Item 7]
Any one of Items 1 to 6, wherein the layered double hydroxide does not change its crystal structure when immersed in a 6 mol / L potassium hydroxide aqueous solution containing no zinc oxide at 90 ° C. for 1 week. The functional layer described in the section.
[Item 8]
Item 2. The functional layer according to any one of Items 1 to 7, wherein the functional layer has a thickness of 100 μm or less.
[Item 9]
Item 2. The functional layer according to any one of Items 1 to 8, wherein the functional layer further contains titania.
[Item 10]
A functional layer containing a layered double hydroxide, wherein the layered double hydroxide contains Ni and Al, and the functional layer further contains Y and titania, and the atomic ratio of Y / Al is 0.5 or more. The functional layer.
[Item 11]
(I) The layered double hydroxide contains Ni, Al and Y, and / or (ii) The layered double hydroxide contains Ni and Al, and the functional layer is the layered double hydroxide. Item 10. The functional layer according to Item 10, wherein the functional layer contains different Y compounds.
[Item 12]
Item 2. The functional layer according to Item 10 or 11, wherein the Y / Al atomic ratio is 1 or more.
[Item 13]
Item 2. The functional layer according to Item 10 or 11, wherein the Atomic ratio of Y / Al is 2 to 8.
[Item 14]
Item 2. The functional layer according to any one of Items 10 to 13, wherein the functional layer has an atomic ratio of Ti / (Y + Al) of 0.1 to 8.
[Item 15]
Item 2. The functional layer according to any one of Items 10 to 14, wherein the layered double hydroxide contains Ni, Al and Y.
[Item 16]
Item 1 of Item 10 to 15, wherein the layered double hydroxide does not change its crystal structure when immersed in a 6 mol / L potassium hydroxide aqueous solution containing no zinc oxide at 90 ° C. for 1 week. The functional layer described in the section.
[Item 17]
Item 2. The functional layer according to any one of Items 10 to 16, wherein the functional layer has a thickness of 100 μm or less.
[Item 18]
Porous substrate and
Item 2. The functional layer according to any one of Items 1 to 17, which is provided on the porous substrate and / or is incorporated in the porous substrate.
Including composite materials.
[Item 19]
Item 18. The composite material according to Item 18, wherein the porous base material is made of a polymer material, and the functional layer is incorporated over the entire area of the porous base material in the thickness direction.
[Item 20]
A battery comprising the functional layer according to any one of Items 1 to 17 or the composite material according to Item 18 or 19 as a separator.

It is a schematic cross-sectional view which shows one aspect of the LDH-containing composite material of this invention. It is a schematic cross-sectional view which shows the other aspect of the LDH-containing composite material of this invention. It is a schematic cross-sectional view which shows still another aspect of the LDH-containing composite material of this invention. It is a schematic cross-sectional view which shows still another aspect of the LDH-containing composite material of this invention. It is a schematic cross-sectional view which shows the electrochemical measurement system used in Examples B1 to B6. It is an exploded perspective view of the closed container for measurement used in the density determination test of Examples B1 to B6. It is a schematic cross-sectional view of the measurement system used in the density determination test of Examples B1 to B6. It is a conceptual diagram which shows an example of the He permeability measurement system used in Examples B1 to B6. It is a schematic cross-sectional view of the sample holder used for the measurement system shown in FIG. 7A and the peripheral structure thereof. It is an X-ray diffraction result of the functional layer prepared in Example B1 (reference). 6 is an SEM image showing the surface microstructure of the functional layer produced in Example B1 (reference). 6 is an SEM image showing a cross-sectional microstructure of the functional layer produced in Example B1 (reference). 6 is an SEM image showing the surface microstructure of the functional layer prepared in Example B1 (reference) before and after being immersed in the KOH aqueous solution for 1 week and 3 weeks. It is the X-ray diffraction result of the functional layer prepared in Example B1 (reference) before the immersion in the KOH aqueous solution, after the immersion for 1 week, and after the immersion for 3 weeks. It is an SEM image which shows the cross-sectional microstructure of the functional layer prepared in Example B2 (reference) before the immersion in the KOH aqueous solution, after the immersion for 3 weeks and after the immersion for 7 weeks. 6 is an SEM image showing the cross-sectional microstructure of the functional layer prepared in Example B4 (reference) before and after being immersed in the KOH aqueous solution for 3 weeks and 7 weeks. 6 is an SEM image showing the surface microstructure of the functional layer prepared in Example B4 (reference) before and after immersion in KOH aqueous solution for 3 weeks and after immersion for 7 weeks. It is an electron analysis simulation result of the BF-STEM image, the FFT analysis pattern, and anatase type titanium oxide obtained about the functional layer prepared in Example B4 (reference). 6 is an SEM image showing the surface microstructure of the functional layer produced in Example B6 (comparison). 6 is an SEM image showing a cross-sectional microstructure of the functional layer produced in Example B6 (comparison). 6 is an SEM image showing the surface microstructure of the functional layer prepared in Example B6 (comparison) before and after immersion in the KOH aqueous solution for 1 week. It is the X-ray diffraction result before the immersion in the KOH aqueous solution and after the immersion in the KOH aqueous solution of the functional layer prepared in Example B6 (comparison). 6 is an SEM image showing a cross-sectional microstructure of the functional layer and composite material produced in Example B7.

LDH-Containing Functional Layer and Composite Material The functional layer of the present invention is a layer containing layered double hydroxides (LDH). This LDH contains Ni, Ti and Al. The functional layer further contains Y, and the atomic ratio of Y / Al is 0.5 or more. Typically, (i) LDH contains Ni, Ti, Al and Y, or (ii) LDH contains Ni, Ti and Al and the functional layer contains a Y compound different from LDH. .. It may satisfy both (i) and (ii) above. In any case, the functional layer contains Y as part of the constituent elements of LDH and / or in the form of a compound different from LDH. In other words, the functional layer may include Y in some form. The functional layer has a Y / Al atomic ratio of 0.5 or more. In this way, by incorporating Y in the Ni-Al-Ti-LDH-containing functional layer at a predetermined atomic ratio (for example, by substituting a part of trivalent Al with trivalent Y), alkali resistance is achieved. An excellent LDH-containing functional layer can be provided.

That is, as described above, LDH for alkaline secondary batteries is desired to have high alkali resistance such that it hardly deteriorates even in a strongly alkaline electrolytic solution. In this respect, the present inventors have previously found that the Ni-Al-Ti-LDH-containing functional layer exhibits not only ionic conductivity but also good alkali resistance. At that time, in the evaluation of alkali resistance, a potassium hydroxide aqueous solution to which a predetermined amount of zinc oxide was added was used as an electrolytic solution composition assuming practical use in a zinc secondary battery. However, it has been found that when an attempt is made to eliminate zinc oxide from the electrolytic solution or reduce the zinc oxide concentration in order to improve the battery characteristics, the alkali resistance of Ni-Al-Ti-LDH having the above composition can be lowered. It is considered that this is because in the zinc oxide-free aqueous solution of potassium hydroxide, Al of Ni-Al-Ti-LDH is eluted and easily converted to β-nickel hydroxide. On the other hand, in the functional layer of the present invention, Y is further contained (for example, in the form of (i) and / or (ii) above) in the functional layer containing Ni-Al-Ti-LDH. It can also exhibit excellent alkali resistance to an electrolytic solution for a high-performance battery such as an aqueous solution of potassium hydroxide that does not contain zinc oxide or has a reduced zinc oxide content.

Specifically, LDH contained in the functional layer undergoes a change in crystal structure when immersed in a 6 mol / L potassium hydroxide aqueous solution containing no zinc oxide at 90 ° C. for 1 week (that is, 168 hours). It is preferable that there is no such thing because it is particularly excellent in alkali resistance. The presence or absence of a change in the crystal structure can be preferably performed by crystal structure analysis using XRD (X-ray diffraction) (for example, the presence or absence of a shift of the (003) peak derived from LDH). Potassium hydroxide is a typical strong alkaline substance, and the composition of the aqueous potassium hydroxide solution corresponds to a typical strong alkaline electrolyte of an alkaline secondary battery. Therefore, it can be said that the above-mentioned evaluation method of immersing the strong alkaline electrolyte at a high temperature of 90 ° C. for a long period of one week is a harsh alkali resistance test. LDH for alkaline secondary batteries is desired to have high alkali resistance such that it hardly deteriorates even in a strongly alkaline electrolytic solution. Further, as described above, even a Ni-Al-Ti-LDH functional layer that is judged to have excellent alkali resistance when immersed in an aqueous potassium hydroxide solution to which zinc oxide is added contains zinc oxide. Alkali resistance is reduced with an aqueous solution of potassium hydroxide that is absent or has a reduced zinc oxide content. In this respect, the functional layer of this embodiment has particularly excellent alkali resistance that the crystal structure does not change even by the above-mentioned harsh alkali resistance test using such an aqueous potassium hydroxide solution. .. Nevertheless, the functional layer of this embodiment can also exhibit high ionic conductivity suitable for use as a separator for an alkaline secondary battery due to the unique properties of LDH. That is, according to this aspect, it is possible to provide an LDH-containing functional layer having excellent not only ionic conductivity but also alkali resistance.

By the way, as is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. An intermediate layer of LDH contained in the functional layer is composed of an anion and H _{2 O.} The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in LDH contain OH ⁻ and / or CO ₃ ^2- . By the way, the electrolytic solution of an alkaline secondary battery (for example, a metal-air battery or a nickel-zinc battery) to which LDH is applied is required to have high hydroxide ion conductivity, and therefore, a strongly alkaline KOH having a pH of about 14 is required. It is desirable that an aqueous solution be used. Therefore, LDH is desired to have a high degree of alkali resistance such that it hardly deteriorates even in such a strongly alkaline electrolytic solution. Therefore, it is preferable that LDH in the present invention does not change the crystal structure by the alkali resistance evaluation as described above. Further, as described above, LDH has excellent ionic conductivity due to its unique properties and the composition described above.

According to a typical aspect of the present invention, the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups. Y may be contained in the basic hydroxide layer, may be contained between the basic layers of hydroxide, and may be present at any place in LDH. Alternatively, Y may be contained in the functional layer as a Y compound different from LDH (for example, yttrium hydroxide) without being contained in LDH. Of course, Y may be contained in LDH and also contained as the Y compound in the functional layer. In any case, the intermediate layer, as described above, composed of an anion and H _{2 O.} The alternating laminated structure of the basic hydroxide layer and the intermediate layer itself is basically the same as the generally known alternating laminated structure of LDH, but in the functional layer of this embodiment, the basic hydroxide layer of LDH is made of Ni. By being composed of a predetermined element or ion containing Al, Ti and OH groups and further containing the above Y compound in the LDH and / or the functional layer, excellent alkali resistance can be exhibited. The reason is not always clear, but in the LDH of this embodiment, Al, which was conventionally thought to be easily eluted in an alkaline solution, becomes difficult to elute in an alkaline solution due to some interaction with Ni, Ti and Y. it is conceivable that. Nevertheless, the functional layer of this embodiment can also exhibit high ionic conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can take the form of nickel ions. Nickel ions in LDH are typically considered to be Ni ²⁺ , but are not particularly limited as other valences such as ^{Ni 3+ are possible.} Al in LDH can take the form of aluminum ions. Aluminum ions in LDH are typically considered to be Al ³⁺ , but are not particularly limited as other valences are possible. Ti in LDH can take the form of titanium ions. Titanium ions in LDH are typically considered to be Ti ⁴⁺ , but are not particularly limited as other valences such as ^{Ti 3+ are possible.} Y in LDH can take the form of yttrium ions. The yttrium ion in LDH is typically considered to be Y ³⁺ , but is not particularly limited as other valences are possible. The hydroxide basic layer may contain other elements or ions as long as it contains Ni, Al, Ti and OH groups. For example, the hydroxide base layer may further contain ^{Zn (typically Zn 2+} ) and / or K (typically K ^+). However, the hydroxide basic layer preferably contains Ni, Al, Ti, OH groups and, in some cases, Y as main components. That is, the hydroxide basic layer is preferably composed mainly of Ni, Al, Ti, OH groups, and in some cases Y. Therefore, the hydroxide basic layer is typically composed of Ni, Al, Ti, OH groups and, in some cases, Y, Zn, K and / or unavoidable impurities. Inevitable impurities are arbitrary elements that can be unavoidably mixed in the production method, and can be mixed in LDH, for example, derived from raw materials and base materials. As described above, since the valences of Ni, Al, Ti and Y are not always fixed, it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the hydroxide basic layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ , Y ³⁺ and OH groups, the corresponding LDH is expressed by the general formula: Ni ²⁺ _1-xy ( Al ³⁺ _1-α Y ^{3 +} _α ) _x Ti ⁴⁺ _y (OH) ₂ A ^n- _{(x + 2y) / n} · mH ₂ O (In the formula, A ^n- is an anion of n valence, n is an integer of 1 or more, It is preferably 1 or 2, 0 <x <1, preferably 0.01 ≦ x ≦ 0.5, 0 <y <1, preferably 0.01 ≦ y ≦ 0.5, 0 <x + y <1, 0 <α <1, preferably 0.3 ≤ α ≤ 0.9, more preferably 0.6 ≤ α ≤ 0.9, preferably m is 0 or more, typically greater than 0 or greater than 1 real number It can be expressed by the basic composition. However, the above general formula should be understood as "basic composition" to the ^{extent that elements such as Ni 2+} , Al ³⁺ , Ti ⁴⁺ , and Y ³⁺ do not impair the basic characteristics of LDH, and other elements or ions ( It should be understood as replaceable with other valence elements or ions of the same element or elements or ions that can be unavoidably mixed in the process.

The functional layer has a Y / Al atomic ratio of 0.5 or more, preferably 1 or more, more preferably 1 to 9, still more preferably 2 to 8, and particularly preferably 3 to 8. Within the above range, the crystal phase change of LDH is suppressed more effectively, and as a result, the alkali resistance is significantly improved. The atomic ratio of Y / Al is preferably determined by energy dispersive X-ray analysis (EDS).

The functional layer preferably has an atomic ratio of Ti / (Y + Al) of 0.1 to 8, more preferably 0.2 to 7, and even more preferably 0.2 to 5. Within the above range, both alkali resistance and ionic conductivity can be improved. The atomic ratio of Y / Al is preferably determined by energy dispersive X-ray analysis (EDS).

The functional layer preferably has an atomic ratio of Ti / (Ni + Ti + Al + Y) of 0.10 to 0.90, more preferably 0.25 to 0.80, still more preferably 0.25 to 0.70, and particularly. It is preferably 0.30 to 0.61. Within the above range, both alkali resistance and ionic conductivity can be improved. The atomic ratio of Ti / (Ni + Ti + Al + Y) is preferably determined by energy dispersive X-ray analysis (EDS).

The functional layer may further include titania. It can be expected that the content of titania increases the hydrophilicity and the wettability with the electrolytic solution (that is, the conductivity is improved). When the functional layer contains titania, LDH contained in the functional layer does not have to contain Ti.

The functional layer (particularly LDH contained in the functional layer) preferably has hydroxide ion conductivity. In particular, the functional layer preferably has an ionic conductivity of 0.1 mS / cm or more, more preferably 0.5 mS / cm or more, and more preferably 1.0 mS / cm or more. The higher the ionic conductivity, the better, and the upper limit thereof is not particularly limited, but is, for example, 10 mS / cm. Such high ionic conductivity is particularly suitable for battery applications. For example, in order to put LDH into practical use, it is desired to reduce the resistance by thinning the film. However, according to this embodiment, an LDH-containing functional layer having a desirable low resistance can be provided. It is particularly advantageous in applying LDH as a solid electrolyte separator to the next battery.

Preferably, the functional layer is provided on and / or incorporated into the porous substrate. That is, according to a preferred embodiment of the present invention, there is provided a composite material comprising a porous substrate and a functional layer provided on and / or incorporated into the porous substrate. For example, as in the composite material 10 shown in FIG. 1, a part of the functional layer 14 may be incorporated in the porous base material 12, and the remaining part may be provided on the porous base material 12. At this time, the portion of the functional layer 14 on the porous substrate 12 is a film-like portion made of LDH film, and the portion of the functional layer 14 incorporated into the porous substrate 12 is composed of the porous substrate and LDH. It can be said that it is a complex part to be used. The composite portion typically has a form in which the pores of the porous base material 12 are filled with LDH. Further, when the entire functional layer 14'is incorporated into the porous base material 12 as in the composite material 10'shown in FIG. 2, the functional layer 14' is mainly composed of the porous base material 12 and LDH. It can be said that it will be done. The composite material 10'and the functional layer 14'shown in FIG. 2 are obtained by removing the film-like portion (LDH film) in the functional layer 14 from the composite material 10 shown in FIG. 1 by a known method such as polishing or cutting. Obtainable. In FIGS. 1 and 2, the functional layers 14 and 14'are incorporated only in a part near the surface of the porous substrates 12 and 12', but the functional layers may be incorporated in any part of the porous substrate. Often, as in the composite material 10 ″ shown in FIG. 3, the functional layer 14 ′ may be incorporated over the entire or total thickness of the porous substrate 12. That is, the LDH may block the pores of the porous base material 12 over the entire or the entire thickness of the porous base material 12 to form the functional layer 14 ″ as a whole.

By the way, the functional layer of the present invention does not necessarily require support by a porous base material, but is a self-supporting functional layer 14'''' in a form without a porous base material as shown in FIG. Needless to say, it is good. Such a self-supporting functional layer 14'''is removed by a known method such as (i) polishing, cutting, or the like, after (i) preparing the composite material 10 as shown in FIG. It can be produced by leaving a film-like portion (LDH film).

The porous base material in the composite material of the present invention is preferably one capable of forming an LDH-containing functional layer on and / or in the composite material, and the material and the porous structure are not particularly limited. Although it is typical to form an LDH-containing functional layer on and / or in a porous substrate, an LDH-containing functional layer is formed on a non-porous substrate and then pore-free by various known methods. The quality substrate may be made porous. In any case, it is preferable that the porous substrate has a porous structure having water permeability because the electrolytic solution can be configured to reach the functional layer when incorporated into the battery as a battery separator.

The porous substrate is preferably composed of at least one selected from the group consisting of ceramic materials, metal materials, and polymer materials, and more preferably selected from the group consisting of ceramic materials and polymer materials. It is composed of at least one type. The porous substrate is more preferably composed of a ceramic material. In this case, preferred examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordylite, zeolite, mulite, ferrite, zinc oxide, silicon carbide, and any combination thereof, which is more preferable. Is alumina, zirconia, titania, and any combination thereof, particularly preferably alumina, zirconia (eg yttria-stabilized zirconia (YSZ)), and combinations thereof. When these porous ceramics are used, it is easy to form an LDH-containing functional layer having excellent density. Preferred examples of metallic materials include aluminum, zinc, and nickel. Preferred examples of the polymer material are polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrophilized fluororesin (tetrafluororesin: PTFE, etc.), cellulose, nylon, polyethylene and any combination thereof. Can be mentioned. All of the various preferred materials described above have alkali resistance as resistance to the electrolytic solution of the battery.

It is particularly preferable that the porous substrate is composed of a polymer material. The polymer porous substrate has 1) flexibility (hence, it is hard to break even if it is thinned), 2) easy to increase the porosity, and 3) easy to increase the conductivity (thickness while increasing the porosity). It has the advantages of being easy to manufacture and handle. Particularly preferable polymer materials are polyolefins such as polypropylene and polyethylene, and most preferably polypropylene, because they are excellent in heat resistance, acid resistance and alkali resistance, and are low in cost. When the porous substrate is composed of a polymer material, the functional layer is incorporated over the entire thickness direction of the porous substrate (for example, most or almost all the pores inside the porous substrate are filled with LDH. ) Is particularly preferable. In this case, the preferable thickness of the polymer porous substrate is 5 to 200 μm, more preferably 5 to 100 μm, and further preferably 5 to 30 μm. As such a polymer porous substrate, a microporous membrane as commercially available as a separator for a lithium battery can be preferably used.

The porous substrate preferably has an average pore diameter of up to 100 μm or less, more preferably up to 50 μm or less, typically 0.001 to 1.5 μm, more typically 0.001. It is ~ 1.25 μm, more typically 0.001 to 1.0 μm, particularly typically 0.001 to 0.75 μm, and most typically 0.001 to 0.5 μm. Within these ranges, it is possible to form an LDH-containing functional layer that is so dense that it does not have water permeability while ensuring the desired water permeability and strength as a support in the porous substrate. In the present invention, the average pore diameter can be measured by measuring the longest distance of the pores based on an electron microscope image of the surface of the porous substrate. The magnification of the electron microscope image used for this measurement is 20000 times or more, and all the obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points are arranged in order from the average value, for a total of 30 points per field of view. The average pore diameter can be obtained by calculating the average value for two fields of view. For the length measurement, a length measurement function of SEM software, image analysis software (for example, Photoshop, manufactured by Adobe), or the like can be used.

The porous substrate preferably has a porosity of 10 to 60%, more preferably 15 to 55%, still more preferably 20 to 50%. Within these ranges, it is possible to form an LDH-containing functional layer that is so dense that it does not have water permeability while ensuring the desired water permeability and strength as a support in the porous substrate. The porosity of the porous substrate can be preferably measured by the Archimedes method. However, when the porous base material is composed of a polymer material and the functional layer is incorporated over the entire area in the thickness direction of the porous base material, the porosity of the porous base material is preferably 30 to 60%, more preferably. It is preferably 40 to 60%.

The functional layer is preferably non-breathable. That is, it is preferable that the functional layer is densified with LDH to the extent that it does not have air permeability. In addition, in this specification, "not having air permeability" means an object to be measured in water when the air permeability is evaluated by the "denseness determination test" adopted in the examples described later or a method or configuration similar thereto. It means that even if helium gas is brought into contact with one surface side (that is, the functional layer and / or the porous substrate) at a differential pressure of 0.5 atm, no bubbles are generated due to helium gas from the other surface side. .. By doing so, the functional layer or the composite material can selectively pass only hydroxide ions due to its hydroxide ion conductivity as a whole, and can exhibit a function as a battery separator. .. When considering the application of LDH as a solid electrolyte separator for batteries, there is a problem that LDH dense bodies in bulk form have high resistance, but in a preferred embodiment of the present invention, strength can be imparted by a porous substrate. Therefore, the LDH-containing functional layer can be made thin to reduce the resistance. Moreover, since the porous substrate can have water permeability and breathability, the electrolyte solution can reach the LDH-containing functional layer when used as a solid electrolyte separator for a battery. That is, the LDH-containing functional layer and composite material of the present invention can be used as a solid electrolyte separator applicable to various battery applications such as metal-air batteries (for example, zinc-air batteries) and other various zinc secondary batteries (for example, nickel-zinc batteries). It can be a very useful material.

The functional layer or the composite material provided with the functional layer preferably has a He transmittance of 10 cm / min · atm or less, more preferably 5.0 cm / min · atm or less, and further preferably 1.0 cm / atm per unit area. It is less than or equal to min · atm. It can be said that the functional layer having He transmittance within such a range has extremely high density. Therefore, a functional layer having a He permeability of 10 cm / min · atm or less can block a high level of passage of substances other than hydroxide ions when applied as a separator in an alkaline secondary battery. For example, in the case of a zinc secondary battery, the permeation of Zn (typically the permeation of zinc ions or zincate ions) in the electrolytic solution can be suppressed extremely effectively. By significantly suppressing Zn permeation in this way, it is considered in principle that the growth of zinc dendrite can be effectively suppressed when used in a zinc secondary battery. The He permeability is measured through a step of supplying He gas to one surface of the functional layer to allow the He gas to permeate through the functional layer, and a step of calculating the He permeability and evaluating the density of the functional layer. To. The He permeability is determined by the formula F / (P × S) using the permeation amount F of the He gas per unit time, the differential pressure P applied to the functional layer when the He gas permeates, and the membrane area S through which the He gas permeates. Calculated by By evaluating the gas permeability using He gas in this way, it is possible to evaluate the presence or absence of denseness at an extremely high level, and as a result, substances other than hydroxide ions (particularly zinc dendrite growth) can be evaluated. It is possible to effectively evaluate a high degree of denseness such that the causing Zn) is not transmitted as much as possible (only a very small amount is transmitted). This is because He gas has the smallest structural unit among a wide variety of atoms or molecules that can form a gas, and has extremely low reactivity. That is, He constitutes He gas by a single He atom without forming a molecule. In this respect, since hydrogen gas is _{composed of H 2} molecules, the He atom alone is smaller as a gas constituent unit. In the first place, H ₂ gas is dangerous because it is a flammable gas. Then, by adopting the index of He gas permeability defined by the above formula, it is possible to easily objectively evaluate the density regardless of the difference in various sample sizes and measurement conditions. In this way, it is possible to easily, safely and effectively evaluate whether or not the functional layer has sufficiently high density suitable for a separator for a zinc secondary battery. The measurement of He permeability can be preferably performed according to the procedure shown in Evaluation 8 of Examples described later.

The functional layer preferably has a thickness of 100 μm or less, more preferably 75 μm or less, further preferably 50 μm or less, particularly preferably 25 μm or less, and most preferably 5 μm or less. By being thin in this way, it is possible to realize a low resistance of the functional layer. When the functional layer is formed as an LDH film on a porous substrate, the thickness of the functional layer corresponds to the thickness of the film-like portion made of the LDH film. When the functional layer is formed by being incorporated into the porous substrate, the thickness of the functional layer corresponds to the thickness of the composite portion composed of the porous substrate and LDH. When the functional layer is formed on and across the porous substrate, it corresponds to the total thickness of the film-like portion (LDH film) and the composite portion (porous substrate and LDH). In any case, if the thickness is as described above, a desired low resistance suitable for practical use in battery applications and the like can be realized. The lower limit of the thickness of the LDH film is not particularly limited because it varies depending on the application, but it is preferably 1 μm or more, more preferably 1 μm or more, in order to secure a certain degree of hardness desired for a functional film such as a separator. Is 2 μm or more.

The method for producing the LDH-containing functional layer and the composite material is not particularly limited, and the LDH-containing functional layer and the composite material are produced by appropriately changing the conditions of the already known methods for producing the LDH-containing functional layer and the composite material (see, for example, Patent Documents 1 and 2). be able to. For example, (1) a porous base material is prepared, (2) a mixed sol of alumina, titania, and itria is applied to the porous base material and heat-treated to form an alumina-titania-itria layer, and (3) The porous base material is immersed in an aqueous solution of a raw material containing nickel ions (Ni ²⁺ ) and urea, and (4) the porous base material is hydrothermally heat-treated in the aqueous solution of the raw material to put an LDH-containing functional layer on the porous base material and / Alternatively, the LDH-containing functional layer and the composite material can be produced by forming the LDH-containing functional layer in the porous substrate. In particular, by forming the alumina titania yttria layer on the porous substrate in the above step (2), not only the raw material for LDH is provided, but also the surface of the porous substrate is made to function as a starting point for LDH crystal growth. A highly densified LDH-containing functional layer can be uniformly and uniformly formed. Further, in the presence of urea in the above step (3), the pH value rises due to the generation of ammonia in the solution by utilizing the hydrolysis of urea, and the coexisting metal ions form a hydroxide. LDH can be obtained by. In addition, since hydrolysis involves the generation of carbon dioxide, anions can obtain carbonate ion-type LDH.

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

As a modification of the present invention, a mode in which LDH does not contain Ti and the functional layer contains titania can be adopted instead. That is, in the functional layer according to this modification, the layered double hydroxide contains Ni and Al, the functional layer further contains Y and titania, and the atomic ratio of Y / Al is 0.5 or more. .. In this case, (i) LDH may contain Ni, Al and Y. Alternatively, (ii) LDH may contain Ni and Al, and the functional layer may contain a Y compound different from the layered double hydroxide. It may satisfy both (i) and (ii) above. Therefore, the above description of the functional layer and the composite material also applies to this modification, except that the functional layer contains titania instead of the LDH containing Ti.

The functional layer or composite material of the present invention can be used not only for alkaline secondary batteries such as zinc-air batteries and nickel-zinc batteries, but also for nickel-metal hydride batteries, for example. In this case, the functional layer or the composite material functions to block the nitride shuttle (movement of nitric acid groups between electrodes), which is a factor of self-discharge of the battery. Further, the functional layer or composite material of the present invention can also be used for a lithium battery (a battery having a negative electrode of lithium metal as a negative electrode), a lithium ion battery (a battery having a negative electrode of carbon or the like), a lithium air battery or the like.

The present invention will be described in more detail with reference to the following examples.

Examples A1 to A5
Functional layers containing LDH of various compositions were prepared and evaluated by the following procedure.

(1) Preparation of Porous Substrate: 70 parts by weight of dispersion medium (xylene: butanol = 1: 1) and binder (Polyvinyl butyral: Sekisui Chemical Co., Ltd.) with respect to 100 parts by weight of zirconia powder (TZ-8YS manufactured by Tosoh Corporation). BM-2 manufactured by BM-2 Co., Ltd.) 11.1 parts by weight, plasticizer (DOP: manufactured by Kurokin Kasei Co., Ltd.) 5.5 parts by weight, and dispersant (Leodor SP-O30 manufactured by Kao Co., Ltd.) 2.9 parts by weight. The mixture was mixed, and the mixture was stirred under reduced pressure to defoam to obtain a slurry. This slurry was molded into a sheet on a PET film using a tape molding machine so that the film thickness would be 220 μm after drying to obtain a sheet molded body. The obtained molded product was cut into a size of 2.0 cm × 2.0 cm × thickness 0.022 cm and fired at 1100 ° C. for 2 hours to obtain a porous base material made of zirconia.

With respect to the obtained porous base material, the porosity of the porous base material was measured by the Archimedes method and found to be 40%.

Moreover, when the average pore diameter of the porous base material was measured, it was 0.2 μm. In the present invention, the average pore diameter was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement was 20000 times, and all the obtained pore diameters were arranged in order of size, and the top 15 points and the bottom 15 points were arranged in order from the average value, for a total of 1 field of view. The average value for two fields of view was calculated at 30 points to obtain the average pore diameter. For the length measurement, the length measurement function of the SEM software was used.

(2) Alumina-titania-itria sol coat on a porous substrate A commercially available amorphous alumina solution, a commercially available titanium oxide sol solution, and a commercially available yttrium oxide sol have a Y / Al atomic ratio and a Ti / (Y + Al) atomic ratio. A mixed sol was prepared by mixing them so as to have the atomic ratios shown in Table 1. 0.2 ml of the mixed sol was applied onto the zirconia-made porous substrate obtained in (1) above by spin coating. In the spin coating, the mixed sol was dropped onto the base material rotated at a rotation speed of 8000 rpm, the rotation was stopped 5 seconds later, and the base material was allowed to stand on a hot plate heated to 100 ° C. and dried for 1 minute. The thickness of the layer thus formed was about 1 μm.

(3) As the manufacturing raw material of the raw aqueous solution, prepared nickel nitrate hexahydrate _{(Ni (NO 3) 2 ·} 6H 2 O, manufactured by Kanto Chemical Co., Inc. and urea _{((NH 2)} 2 CO, manufactured by Sigma-Aldrich) Nickel nitrate hexahydrate was weighed to 0.015 mol / L and placed in a beaker, and ion-exchanged water was added thereto to make the total volume 75 ml. After stirring the obtained solution, the solution was added. Urea weighed at a ratio of urea / NO ₃ ⁻ = 16 was added thereto, and the mixture was further stirred to obtain an aqueous raw material solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) closed container (autoclave container, content 100 ml, outer stainless steel jacket) is filled with the raw material aqueous solution prepared in (3) above and the base material prepared in (2) above. Was enclosed together. At this time, the base material was floated and fixed from the bottom of a closed container made of Teflon (registered trademark), and placed horizontally so that the solution was in contact with both sides of the base material. Then, LDH was formed on the surface and the inside of the base material by subjecting it to hydrothermal treatment at a hydrothermal temperature of 120 ° C. for 24 hours. After a lapse of a predetermined time, the base material is taken out from the closed container, washed with ion-exchanged water, left at 70 ° C. for 10 hours, dried, and a functional layer containing LDH is partially contained in the porous base material. Obtained in a built-in form. The thickness of the obtained functional layer was about 5 μm (including the thickness of the portion incorporated in the porous substrate).
(5) Evaluation The following evaluation was performed on the obtained functional layer or composite material.

Evaluation 1 : Identification of the functional layer The crystal phase of the functional layer is measured with an X-ray diffractometer (RINT TTR III manufactured by Rigaku Co., Ltd.) under the measurement conditions of voltage: 50 kV, current value: 300 mA, and measurement range: 10 to 70 °. The XRD profile was obtained. Regarding the obtained XRD profile, JCPDS card No. Using the diffraction peaks of LDH (hydrotalcite compounds) described in 35-0964, TiO ₂ described in 01-071-1169, and β-Ni (OH) _{2 described in 00-014-1117.} Identification was performed. As a result, it was identified that all the functional layers of Examples A1 to A5 were LDH (hydrotalcite compounds) (before the alkali resistance test described later).

Evaluation 2 : Alkali resistance evaluation 1.5 ml of a 6 mol / L potassium hydroxide aqueous solution containing no zinc oxide and a sample having a size of 2 cm × 2 cm were placed in a closed container made of Teflon (registered trademark) and placed at 90 ° C. for 1 week (that is, that is). After holding (168 hours), the sample was taken out of the closed container. The removed sample was dried overnight at room temperature. The crystal structure of the obtained sample was observed by XRD in the same manner as described above, and the presence or absence of a change in the crystal phase before and after immersion was confirmed.

As shown in Table 1, when the Y / Al ratio is 0.5 or more, the change in the crystal phase is significantly reduced and the alkali resistance is improved, and when it is 2 or more, the change in the crystal phase disappears and the alkali resistance is further improved. You can see that. The Y / Al ratio and the Ti (Y + Al) ratio shown in Table 1 above are atomic ratios in the mixed sol, but it is considered that the same atomic ratio is also obtained in the finally obtained functional layer. Further, in these examples, LDH is considered to contain Ni, Ti, Al and Y. On the other hand, it cannot be denied that LDH contains Ni, Ti and Al, and the functional layer further contains a Y compound different from LDH. In any case, the functional layer still contains Y.

Examples B1 to B7 (reference)
It is not the functional layer composition of the present invention containing Y, but is common to the functional layer composition of the present invention except that it does not contain Y, in order to help demonstrate the basic performance of the functional layer and the composite material of the present invention. Alternatively, an example of preparation and evaluation of a functional layer having a similar composition is shown below. Specifically, a reference example relating to a functional layer containing Ni, Al and Ti-containing LDH (but not including Y) and a composite material, and a function containing Mg and Al-containing LDH (but not including Y) as a comparative example. Shown below with comparative examples of layers and composites. The evaluation method of the functional layer and the composite material produced in the following example was as follows.

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

Evaluation 2 : Observation of microstructure The surface microstructure of the functional layer was observed with an acceleration voltage of 10 to 20 kV using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL Ltd.). Further, after obtaining a cross-section polished surface of a functional layer (a film-like part made of an LDH film and a composite part made of an LDH and a base material) by an ion milling device (IM4000 manufactured by Hitachi High-Technologies Corporation), the fineness of the cross-section polished surface The structure was observed by SEM under the same conditions as the observation of the surface microstructure.

Evaluation 3 : Elemental Analysis Evaluation (EDS) I
The cross-section polisher (CP) was used to polish the functional layer (a film-like portion made of LDH film and a composite portion made of LDH and a base material) so that the cross-sectional polished surface could be observed. By FE-SEM (ULTRA55, manufactured by Carl Zeiss), a cross-sectional image of a functional layer (a film-like part made of LDH film and a composite part made of LDH and a base material) was acquired in one visual field at a magnification of 10000 times. Elemental analysis of the LDH film on the surface of the substrate and the LDH portion (point analysis) inside the substrate in this cross-sectional image was performed using an EDS analyzer (NORAN System SIX, manufactured by Thermo Fisher Scientific) under the condition of an acceleration voltage of 15 kV. went.

Evaluation 4 : Elemental Analysis Evaluation (EDS) II
In order to calculate the atomic ratio of Ti / (Ni + Ti + Al), composition analysis was performed on the surface of the functional layer using an EDS analyzer (device name: X-act, manufactured by Oxford Instruments). In this analysis, 1) an image is captured at an acceleration voltage of 20 kV and a magnification of 5,000 times, 2) three-point analysis is performed at intervals of about 5 μm in the point analysis mode, and 3) 1) and 2) above are repeated twice. It was repeated, and 4) the average value of a total of 9 points was calculated.

Evaluation 5 : Alkali resistance evaluation Zinc oxide was dissolved in a 6 mol / L potassium hydroxide aqueous solution to obtain a 5 mol / L potassium hydroxide aqueous solution containing zinc oxide at a concentration of 0.4 mol / L. 15 ml of the potassium hydroxide aqueous solution thus obtained was placed in a closed container made of Teflon (registered trademark). A 1 cm x 0.6 cm size composite was placed on the bottom of the closed container with the functional layer facing up and the lid closed. Then, after holding at 70 ° C. (eg B1 to B5) or 30 ° C. (eg B6) for 1 week (ie, 168 hours), 3 weeks (ie, 504 hours) or 7 weeks (1176 hours), the composite material is removed from the closed container. I took it out. The removed composite was dried overnight at room temperature. The obtained sample was subjected to microstructure observation by SEM and crystal structure observation by XRD. In the crystal structure observation by XRD, the crystal structure was significantly changed when the peak position (2θ) was shifted by more than 0.25 ° with respect to the (003) peak of LDH before and after immersion in the potassium hydroxide aqueous solution. It was judged that it had changed.

Evaluation 6 : Measurement of ionic conductivity The conductivity of the functional layer in the electrolytic solution was measured as follows using the electrochemical measurement system shown in FIG. The composite material sample S (porous base material with LDH film) was sandwiched between both sides with a 1 mm thick silicone packing 40 and incorporated into a PTFE flange type cell 42 having an inner diameter of 6 mm. As the electrodes 46, a nickel wire mesh of # 100 mesh was incorporated into the cell 42 in a cylindrical shape with a diameter of 6 mm so that the distance between the electrodes was 2.2 mm. As the electrolytic solution 44, a 6M KOH aqueous solution was filled in the cell 42. Using an electrochemical measurement system (potential / galvanostad-frequency response analyzer, Solartron 1287A and 1255B), the measurement was performed under the conditions of a frequency range of 1 MHz to 0.1 Hz and an applied voltage of 10 mV, and a section of the real number axis. Was used as the resistance of the composite material sample S (porous base material with LDH film). The same measurement as described above was performed only on the porous substrate without the LDH film, and the resistance of only the porous substrate was determined. The difference between the resistance of the composite material sample S (porous base material with LDH film) and the resistance of the base material alone was defined as the resistance of the LDH film. The conductivity was determined using the resistance of the LDH film and the film thickness and area of LDH.

Evaluation 7 : Denseness judgment test In order to confirm that the functional layer has a density that does not have air permeability, a density judgment test was conducted as follows. First, as shown in FIGS. 6A and 6B, an acrylic container 130 without a lid and an alumina jig 132 having a shape and size capable of functioning as a lid of the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying gas. Further, the alumina jig 132 is formed with an opening 132a having a diameter of 5 mm, and a recess 132b for placing a sample is formed along the outer circumference of the opening 132a. The epoxy adhesive 134 was applied to the recess 132b of the alumina jig 132, and the functional layer 136b side of the composite material sample 136 was placed in the recess 132b and adhered to the alumina jig 132 in an airtight and liquid-tight manner. Then, the alumina jig 132 to which the composite material sample 136 is bonded is adhered to the upper end of the acrylic container 130 in an airtight and liquid-tight manner using a silicone adhesive 138 so as to completely close the open portion of the acrylic container 130. A closed container 140 for measurement was obtained. The airtight container 140 for measurement was placed in the water tank 142, and the gas supply port 130a of the acrylic container 130 was connected to the pressure gauge 144 and the flow meter 146 so that helium gas could be supplied into the acrylic container 130. Water 143 was put into the water tank 142, and the airtight container 140 for measurement was completely submerged. At this time, the inside of the airtight container 140 for measurement is sufficiently airtight and liquidtight, and the functional layer 136b side of the composite material sample 136 is exposed in the internal space of the airtight container 140 for measurement, while the composite material sample. The 136a side of the porous base material 136a is in contact with the water in the water tank 142. In this state, helium gas was introduced into the acrylic container 130 through the gas supply port 130a into the airtight container 140 for measurement. The pressure gauge 144 and the flow gauge 146 are controlled so that the differential pressure inside and outside the functional layer 136a is 0.5 atm (that is, the pressure applied to the side in contact with helium gas is 0.5 atm higher than the water pressure applied to the opposite side). Then, it was observed whether or not helium gas bubbles were generated in the water from the composite material sample 136. As a result, when the generation of bubbles due to helium gas was not observed, it was determined that the functional layer 136b had a high density so as not to have air permeability.

Evaluation 8 : He Permeation Measurement A He permeation test was conducted as follows in order to evaluate the denseness of the functional layer from the viewpoint of He permeability. First, the He permeability measuring system 310 shown in FIGS. 7A and 7B was constructed. The He permeability measuring system 310 has a function in which He gas from a gas cylinder filled with He gas is supplied to the sample holder 316 via a pressure gauge 312 and a flow meter 314 (digital flow meter) and held in the sample holder 316. The layer 318 was configured to be permeated from one surface to the other surface and discharged.

The sample holder 316 has a structure including a gas supply port 316a, a closed space 316b, and a gas discharge port 316c, and was assembled as follows. First, an adhesive 322 was applied along the outer circumference of the functional layer 318 and attached to a jig 324 (made of ABS resin) having an opening in the center. Packing made of butyl rubber is arranged as sealing members 326a and 326b at the upper and lower ends of the jig 324, and support members 328a and 328b (manufactured by PTFE) provided with openings made of flanges from the outside of the sealing members 326a and 326b. ). In this way, the sealed space 316b was partitioned by the functional layer 318, the jig 324, the sealing member 326a, and the supporting member 328a. The functional layer 318 is in the form of a composite material formed on the porous base material 320, and is arranged so that the functional layer 318 side faces the gas supply port 316a. The support members 328a and 328b were tightened tightly to each other by a fastening means 330 using screws so that He gas did not leak from a portion other than the gas discharge port 316c. A gas supply pipe 334 was connected to the gas supply port 316a of the sample holder 316 thus assembled via a joint 332.

Next, He gas was supplied to the He permeability measuring system 310 via the gas supply pipe 334, and was permeated through the functional layer 318 held in the sample holder 316. At this time, the gas supply pressure and the flow rate were monitored by the pressure gauge 312 and the flow meter 314. After permeating the He gas for 1 to 30 minutes, the He permeation was calculated. The He permeability is calculated by the permeation amount F (cm ³ / min) of the He gas per unit time, the differential pressure P (atm) applied to the functional layer when the He gas permeates, and the film area S (cm) through which the He gas permeates. ^It was calculated by the formula of F / (P × S) using 2). The permeation amount F (cm ³ / min) of He gas was read directly from the flow meter 314. Further, as the differential pressure P, the gauge pressure read from the pressure gauge 312 was used. The He gas was supplied so that the differential pressure P was in the range of 0.05 to 0.90 atm.

Evaluation 9 : Identification of titania A BF-STEM image of the functional layer was obtained using a scanning transmission electron microscope (STEM) (product name: JEM-ARM200F, manufactured by JEOL Ltd.). The obtained BF-STEM image was analyzed by Fast Fourier Transform (FFT) to obtain an FFT analysis pattern. The obtained FFT analysis pattern was compared with the electronic analysis simulation result of anatase-type titanium oxide, and it was confirmed whether or not the lattice constant that can be read from the FFT analysis pattern was substantially the same as that of anatase-type titanium oxide.

Examples B1 to B5 (reference)
Functional layers and composite materials containing LDH containing Ni, Al and Ti were prepared and evaluated by the following procedure.

(1) Preparation of Porous Substrate: 70 parts by weight of dispersion medium (xylene: butanol = 1: 1) and binder (polyvinyl butyral: Sekisui Chemical Co., Ltd.) with respect to 100 parts by weight of zirconia powder (TZ-8YS manufactured by Tosoh Corporation). BM-2 manufactured by BM-2 Co., Ltd.) 11.1 parts by weight, plasticizer (DOP: manufactured by Kurokin Kasei Co., Ltd.) 5.5 parts by weight, and dispersant (Leodor SP-O30 manufactured by Kao Co., Ltd.) 2.9 parts by weight. The mixture was mixed, and the mixture was stirred under reduced pressure to defoam to obtain a slurry. This slurry was molded into a sheet on a PET film using a tape molding machine so that the film thickness would be 220 μm after drying to obtain a sheet molded body. The obtained molded product was cut into a size of 2.0 cm × 2.0 cm × thickness 0.022 cm and fired at 1100 ° C. for 2 hours to obtain a porous base material made of zirconia.

With respect to the obtained porous base material, the porosity of the porous base material was measured by the Archimedes method and found to be 40%.

Moreover, when the average pore diameter of the porous base material was measured, it was 0.2 μm. In the present invention, the average pore diameter was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement was 20000 times, and all the obtained pore diameters were arranged in order of size, and the top 15 points and the bottom 15 points were arranged in order from the average value, for a total of 1 field of view. The average value for two fields of view was calculated at 30 points to obtain the average pore diameter. For the length measurement, the length measurement function of the SEM software was used.

(2) Alumina-titania sol coating on a porous base material Atypical alumina solution (Al-ML15, manufactured by Taki Chemical Co., Ltd.) and titanium oxide sol solution (M6 manufactured by Taki Chemical Co., Ltd.) are shown in Table 2. A mixed sol was prepared by mixing so as to have an Al atomic ratio. 0.2 ml of the mixed sol was applied onto the zirconia-made porous substrate obtained in (1) above by spin coating. In the spin coating, the mixed sol was dropped onto the base material rotated at a rotation speed of 8000 rpm, the rotation was stopped 5 seconds later, and the base material was allowed to stand on a hot plate heated to 100 ° C. and dried for 1 minute. Then, the heat treatment was performed at 300 ° C. in an electric furnace. The thickness of the layer thus formed was about 1 μm.

(3) As the manufacturing raw material of the raw aqueous solution, prepared nickel nitrate hexahydrate _{(Ni (NO 3) 2 ·} 6H 2 O, manufactured by Kanto Chemical Co., Inc. and urea _{((NH 2)} 2 CO, manufactured by Sigma-Aldrich) Nickel nitrate hexahydrate was weighed to 0.015 mol / L and placed in a beaker, and ion-exchanged water was added thereto to make the total volume 75 ml. After stirring the obtained solution, the solution was added. urea / NO 3 in _- urea weighed at a ratio ^(molar ratio) = 16 was added and further stirred to obtain a raw material solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) closed container (autoclave container, content 100 ml, outer stainless steel jacket) is filled with the raw material aqueous solution prepared in (3) above and the base material prepared in (2) above. Was enclosed together. At this time, the base material was floated and fixed from the bottom of a closed container made of Teflon (registered trademark), and placed horizontally so that the solution was in contact with both sides of the base material. Then, LDH was formed on the surface and the inside of the base material by subjecting it to hydrothermal treatment at a hydrothermal temperature of 150 ° C. for 72 hours (Example B1) or a hydrothermal temperature of 120 ° C. for 24 hours (Examples B2 to B5). After a lapse of a predetermined time, the substrate was taken out of the closed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a functional layer containing LDH was partially incorporated into the porous substrate. Got in shape. The thickness of the obtained functional layer was about 5 μm (including the thickness of the portion incorporated in the porous substrate).

(5) Evaluation Results Evaluations 1 to 8 were performed on the obtained functional layer or composite material. In addition, evaluation 9 was also performed only for Example B4. The results were as follows.

-Evaluation 1: From the obtained XRD profile, it was identified that the functional layer obtained in Examples B1 to B5 is LDH (hydrotalcite compound). FIG. 8 shows the XRD profile obtained in Example B1. Note that FIG. 8 also shows a peak derived from zirconia that constitutes the porous substrate.
-Evaluation 2: SEM images of the surface microstructure and cross-sectional microstructure of the functional layer obtained in Example B1 were as shown in FIGS. 9A and 9B, respectively. As shown in FIG. 9B, it was found that the functional layer was composed of a film-like portion made of an LDH film and a composite part made of an LDH and a porous substrate located below the film-like portion. LDH, which constitutes a film-like portion, is composed of an aggregate of a plurality of plate-like particles, and these plurality of plate-like particles have a surface of a porous base material (fine irregularities due to a porous structure). It was oriented so as to intersect vertically or diagonally with the surface of the porous substrate when observed macroscopically to a negligible degree. On the other hand, in the composite portion, LDH was filled in the pores of the porous base material to form a dense layer. The surface microstructure and cross-sectional microstructure of the functional layer obtained in Examples B2 to B5 were also substantially the same as in Example B1.
-Evaluation 3: As a result of EDS elemental analysis, LDH constituent elements C, Al, Ti and Ni were detected in both the LDH film contained in the functional layer, that is, the LDH film on the surface of the base material and the LDH portion in the base material. Was done. That, Al, while Ti and Ni as an element of a hydroxide base layer, C is corresponding to the _CO ^{3 2-} is an anion constituting the intermediate layer of the LDH.
-Evaluation 4: The atomic ratio of Ti / (Ni + Ti + Al) on the surface of each functional layer calculated by EDS elemental analysis was as shown in Table 2.

-Evaluation 5: The SEM observation results obtained for Examples B1 to B5 were as shown in Table 2. Further, SEM images of the surface microstructure of the functional layer of Example B1 before, 1 week, and 3 weeks of immersion in the KOH aqueous solution were as shown in FIG. Further, SEM images of the cross-sectional microstructures of the functional layers of Examples B2 and B4 before, 3 weeks, and 7 weeks of immersion in the KOH aqueous solution are as shown in FIGS. 12 and 13A, and are as shown in Examples B4. The SEM image of the surface microstructure of the functional layer was as shown in FIG. 13B. As can be seen from Table 2 and FIGS. 10, 12, 13A and 13B, no change was observed in the microstructure of the functional layers of Examples B1 to B5 even after being immersed in a potassium hydroxide aqueous solution at 70 ° C. for 3 weeks. .. In particular, as can be seen from Table 2 and FIGS. 13A and 13B, in the samples of Examples B3 to B5 having a high Ti / (Ni + Ti + Al) ratio, the functional layer was even after being immersed in a potassium hydroxide aqueous solution at 70 ° C. for 7 weeks. No change was observed in the microstructure of. It can be said that the immersion in the potassium hydroxide aqueous solution having a high temperature of 70 ° C. is a considerably harsher alkali resistance acceleration test as compared with the case of a low temperature of 30 ° C. Therefore, it can be evaluated that it has sufficient alkali resistance to withstand the immersion time of 3 weeks, but it can be evaluated that it has particularly excellent alkali resistance to withstand the immersion time of 7 weeks. By the way, although the microstructure of the LDH film of Example B2 shown in FIG. 12 has changed remarkably after being immersed in the KOH aqueous solution for 7 weeks, LDH is also filled in the pores of the porous substrate that is the base of the LDH film. Therefore, it is understood that the denseness of the composite material as a whole is still ensured.

The XRD results obtained for Examples B1 to B5 were as shown in Table 2. The X-ray diffraction results of the functional layer of Example B1 before, 1 week, and 3 weeks of immersion in the KOH aqueous solution were as shown in FIG. As can be seen from Table 2 and FIG. 11, no significant change was observed in the crystal structure in any of Examples B1 to B5 even after being immersed in the potassium hydroxide aqueous solution at 70 ° C. for 3 weeks. In particular, as can be seen from Table 2, in the samples of Examples B2 to B5 having a high Ti / (Ni + Ti + Al) ratio, there was no significant change in the crystal structure even after being immersed in a potassium hydroxide aqueous solution at 70 ° C. for 7 weeks. I couldn't see it. In fact, the position of the (003) peak of LDH contained in the functional layer of Example B1 is 2θ = 11.36 in any of the functional layers before, 1 week, and 3 weeks of immersion in the KOH aqueous solution. there were.

-Evaluation 6: The ionic conductivity of the functional layers of Examples B1 to B5 was 2.0 to 2.5 mS / cm, which was the same level as that of Example B6, which is a comparative example described later.
-Evaluation 7: It was confirmed that the functional layers and composite materials of Examples B1 to B5 have high density so as not to have air permeability.
-Evaluation 8: The He permeability of the functional layers and composite materials of Examples B1 to B5 was 0.0 cm / min · atm.
-Evaluation 9: For the functional layer of Example B4, the BF-STEM image and FFT analysis pattern shown in FIG. 14 were obtained. The lattice constant that can be read from this FFT analysis pattern is almost the same as the electronic analysis simulation result of anatase-type titanium oxide shown in FIG. 14, and it was confirmed that it contains titania.

Example B6 (comparison)
A functional layer and a composite material containing Mg and Al-containing LDH were prepared and evaluated by the following procedure.

(1) Preparation of Porous Substrate: 70 parts by weight of dispersion medium (xylene: butanol = 1: 1) and binder (polyvinyl butyral: Sekisui Kagaku) with respect to 100 parts by weight of alumina powder (AES-12 manufactured by Sumitomo Chemical Co., Ltd.) BM-2) 11.1 parts by weight, plasticizer (DOP: Kurokin Kasei Co., Ltd.) 5.5 parts by weight, and dispersant (Kao Corporation Leodor SP-O30) 2.9 parts by weight Was mixed, and the mixture was stirred under reduced pressure to defoam to obtain a slurry. This slurry was molded into a sheet on a PET film using a tape molding machine so that the film thickness would be 220 μm after drying to obtain a sheet molded body. The obtained molded product was cut into a size of 2.0 cm × 2.0 cm × thickness 0.022 cm and fired at 1300 ° C. for 2 hours to obtain a porous alumina base material.

With respect to the obtained porous base material, the porosity of the porous base material was measured by the Archimedes method and found to be 40%.

The average pore diameter of the porous substrate was measured and found to be 0.3 μm. In the present invention, the average pore diameter was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement was 20000 times, and all the obtained pore diameters were arranged in order of size, and the top 15 points and the bottom 15 points were arranged in order from the average value, for a total of 1 field of view. The average value for two fields of view was calculated at 30 points to obtain the average pore diameter. For the length measurement, the length measurement function of the SEM software was used.

(2) Polystyrene spin coating and sulfonated A spin coating solution having a polystyrene concentration of 0.06 g / ml was prepared by dissolving 0.6 g of a polystyrene substrate in 10 ml of a xylene solution. 0.1 ml of the obtained spin coating solution was dropped onto an 8YSZ porous substrate and applied by spin coating at a rotation speed of 8000 rpm. This spin coating was performed for 200 seconds including dropping and drying. The porous substrate coated with the spin coating solution was immersed in 95% sulfuric acid at 25 ° C. for 4 days to sulfonate.

(3) As the manufacturing raw material of the raw aqueous solution, magnesium nitrate hexahydrate _{(Mg (NO 3) 2 ·} 6H 2 O, manufactured by Kanto Chemical Co., Inc.), aluminum nitrate nonahydrate (Al _{(NO 3)} 3 · 9H ₂ O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH ₂ ) ₂ CO, manufactured by Sigma Aldrich) were prepared. Weigh magnesium nitrate hexahydrate and aluminum nitrate hexahydrate so that the cation ratio (Mg ²⁺ / Al ³⁺ ) is 2 and the total metal ion molar concentration (Mg ²⁺ + Al ^{3+) is 0.320 mol / L.} The mixture was placed in a beaker, and ion-exchanged water was added thereto to make a total volume of 70 ml. The resulting solution was stirred and urea in the solution / NO 3 _- urea weighed at a ratio ^(molar ratio) = 4 was added and further stirred to obtain a raw material solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) airtight container (content 100 ml, outer stainless steel jacket) is filled with the raw material aqueous solution prepared in (3) above and the porous substrate sulfonated in (2) above. Was enclosed together. At this time, the base material was floated and fixed from the bottom of a closed container made of Teflon (registered trademark), and placed horizontally so that the solution was in contact with both sides of the base material. Then, an LDH alignment film was formed on the surface of the base material by subjecting it to hydrothermal treatment at a hydrothermal temperature of 70 ° C. for 168 hours (7 days). After a lapse of a predetermined time, the substrate was taken out of the closed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a functional layer containing LDH was partially incorporated into the porous substrate. Got in shape. The thickness of the obtained functional layer was about 3 μm (including the thickness of the portion incorporated in the porous substrate).

(5) Evaluation Results Evaluations 1 to 3 and 5 to 8 were performed on the obtained functional layer or composite material. The results were as follows.
-Evaluation 1: From the obtained XRD profile, it was identified that the functional layer was LDH (hydrotalcite compound).
-Evaluation 2: SEM images of the surface microstructure and cross-sectional microstructure of the functional layer were as shown in FIGS. 15A and 15B, respectively. Similar to the functional layer obtained in Example B1, a functional layer composed of a film-like portion composed of an LDH film and a composite portion composed of LDH and a porous substrate located below the film-like portion was observed. It was.
-Evaluation 3: As a result of EDS elemental analysis, LDH constituent elements C, Mg and Al were detected in both the LDH film contained in the functional layer, that is, the LDH film on the surface of the base material and the LDH portion in the base material. .. That, Mg and Al whereas a constituent element of a hydroxide base layer, C is corresponding to the _CO ^{3 2-} is an anion constituting the intermediate layer of the LDH.
-Evaluation 5: SEM images of the surface microstructure of the functional layer before and after immersion in the KOH aqueous solution were as shown in FIG. As can be seen from FIG. 16, even after a week of immersion in an aqueous potassium hydroxide solution at 30 ° C., which is lower than 70 ° C. in Examples B1 to B5 (ie, even under milder alkaline conditions than Example B1), the functional layer Changes were seen in the microstructure. The X-ray diffraction results of the functional layer before and after immersion in the KOH aqueous solution were as shown in FIG. As can be seen from FIG. 17, crystals even after being immersed in an aqueous potassium hydroxide solution at 30 ° C., which is lower than 70 ° C. in Examples B1 to B5, for one week (that is, even in milder alkaline conditions than Examples B1 to B5). There was a change in the structure. In particular, the position of the (003) peak of LDH contained in the functional layer was 2θ = 11.70 before immersion in the KOH aqueous solution, but shifted to 2θ = 11.44 after immersion for one week. It was. This shift of the (003) peak can suggest that Al contained in LDH was eluted in the KOH aqueous solution and deteriorated LDH. From these results, the functional layer of Example B6 is inferior in alkali resistance to the functional layer of Example B1, that is, the functional layer of Example B1 which is a reference example is superior to the functional layer of Example B6 which is a comparative example. I found out.
-Evaluation 6: The conductivity of the functional layer was 2.0 mS / cm.
-Evaluation 7: It was confirmed that the functional layer and the composite material have high density so as not to have air permeability.
-Evaluation 8: The He permeability of the functional layer and the composite material was 0.0 cm / min · atm.

Example B7 (reference)
Using the polymer porous substrate, a functional layer and a composite material containing LDH containing Ni, Al and Ti were prepared and evaluated by the following procedure.

(1) Preparation of Polymer Porous Substrate A commercially available polypropylene porous substrate having a porosity of 50%, an average pore diameter of 0.1 μm and a thickness of 20 μm is adjusted to have a size of 2.0 cm × 2.0 cm. Cut out to.

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

(3) Preparation of Raw Material Aqueous Solution A raw material aqueous solution was prepared in the same manner as in Example B1 (3).

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

(5) Evaluation Results Evaluations 1 to 8 were performed on the obtained functional layer or composite material. The results were as follows.
-Evaluation 1: From the obtained XRD profile, it was identified that the functional layer was LDH (hydrotalcite compound).
-Evaluation 2: The SEM image of the cross-sectional microstructure of the functional layer or composite material was as shown in FIG. As can be seen from FIG. 18, it was observed that the functional layer was incorporated over the entire area of the porous substrate in the thickness direction, that is, the pores of the porous substrate were evenly filled with LDH.
-Evaluation 3: As a result of EDS elemental analysis, LDH constituent elements C, Al, Ti and Ni were detected in both the LDH film contained in the functional layer, that is, the LDH film on the surface of the base material and the LDH portion in the base material. Was done. That, Al, while Ti and Ni as an element of a hydroxide base layer, C is corresponding to the _CO ^{3 2-} is an anion constituting the intermediate layer of the LDH.
-Evaluation 4: The atomic ratio of Ti / (Ni + Ti + Al) on the surface of each functional layer calculated by EDS elemental analysis was 0.38.
-Evaluation 5: No change was observed in the microstructure of the functional layers of Examples B1 to B5 even after being immersed in a potassium hydroxide aqueous solution at 70 ° C. for 3 to 7 weeks.
-Evaluation 6: The conductivity of the functional layer was 2.0 mS / cm, which was equivalent to that of Examples B1 to B6 described above.
-Evaluation 7: It was confirmed that the functional layer and the composite material have high density so as not to have air permeability.
-Evaluation 8: The He permeability of the functional layer and the composite material was 0.0 cm / min · atm.

Claims (12)

A functional layer containing a layered double hydroxide, wherein the layered double hydroxide contains Ni, Ti and Al, and the functional layer further contains Y, and the atomic ratio of Y / Al is 0.5 or more. Is a functional layer. (I) The layered double hydroxide contains Ni, Ti, Al and Y, and / or (ii) The layered double hydroxide contains Ni, Ti and Al, and the functional layer is the layered double hydroxide. The functional layer according to claim 1, which contains a Y compound different from hydroxide. The functional layer according to claim 1 or 2, wherein the atomic ratio of Y / Al is 1 or more. The functional layer according to claim 1 or 2, wherein the atomic ratio of Y / Al is 2 to 8. The functional layer according to any one of claims 1 to 4, wherein the functional layer has an atomic ratio of Ti / (Y + Al) of 0.1 to 8. The functional layer according to any one of claims 1 to 5, wherein the layered double hydroxide contains Ni, Ti, Al and Y. Any of claims 1 to 6, wherein the layered double hydroxide does not change its crystal structure when immersed in a 6 mol / L potassium hydroxide aqueous solution containing no zinc oxide at 90 ° C. for 1 week. The functional layer described in item 1. The functional layer according to any one of claims 1 to 7, wherein the functional layer has a thickness of 100 μm or less. The functional layer according to any one of claims 1 to 8, wherein the functional layer further comprises titania. Porous substrate and
The functional layer according to any one of claims 1 to 9, which is provided on the porous substrate and / or is incorporated in the porous substrate.
Including composite materials. The composite material according to claim 10, wherein the porous base material is made of a polymer material, and the functional layer is incorporated over the entire area of the porous base material in the thickness direction. A battery comprising the functional layer according to any one of claims 1 to 9 or the composite material according to claim 10 or 11 as a separator.

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