WO2017221531A1

WO2017221531A1 - Functional layer including layered double hydroxide, and composite material

Info

Publication number: WO2017221531A1
Application number: PCT/JP2017/015402
Authority: WO
Inventors: 翔山本; 昌平横山
Original assignee: 日本碍子株式会社
Priority date: 2016-06-24
Filing date: 2017-04-14
Publication date: 2017-12-28

Abstract

Provided are: a functional layer including a layered double hydroxide (LDH), said functional layer exhibiting not only excellent ion conductivity, but also excellent alkali resistance; and a composite material provided with said functional layer. This functional layer includes a LDH. The LDH is formed from: a plurality of hydroxide base layers which are formed from Ni, Ti, and OH groups, or from Ni, Ti, OH groups, and unavoidable impurities; and intermediate layers which are intercalated between the plurality of hydroxide base layers, and which are formed from anions and H₂O.

Description

Functional layer and composite material containing layered double hydroxide

The present invention relates to a functional layer and a composite material containing a layered double hydroxide.

Layered double hydroxide (hereinafter also referred to as LDH) is a substance having exchangeable anions and H ₂ O as an intermediate layer between stacked hydroxide basic layers. 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 cells 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, Patent Document 1 (International Publication No. 2015/098610) discloses a composite including a porous substrate and an LDH-containing functional layer that does not have water permeability and is formed on and / or in the porous substrate. The material is disclosed, and the LDH-containing functional layer has a general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (where M ²⁺ is 2 such as Mg ²⁺⁾ A valent cation, M ³⁺ is a trivalent cation such as Al ³⁺ , A ⁿ⁻ is an n-valent anion such as OH ⁻ , CO ₃ ²⁻ , n is an integer of 1 or more, and x is 0. 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, when used as a separator, a zinc dendrite that has become a barrier to practical use of alkaline zinc secondary batteries Progress and carbon dioxide intrusion from the air electrode in the zinc-air battery can be prevented.

However, an alkaline secondary battery (for example, a metal-air battery or a nickel-zinc battery) to which LDH is applied requires a high hydroxide ion conductivity, and therefore has a pH of about 14 and a strong alkaline KOH. It is desirable to use an aqueous solution. For this reason, LDH is desired to have a high alkali resistance that hardly deteriorates even in such a strong alkaline electrolyte. In this regard, in Patent Document 2 (International Publication No. 2016/51934), a metal compound containing a metal element (for example, Al) corresponding to the above-described general formula M ²⁺ and / or M ³⁺ is dissolved in an electrolytic solution. There has been proposed an LDH-containing battery that is configured so that erosion of the LDH by the electrolyte is suppressed.

International Publication No. 2015/098610 International Publication No. 2016/051934

The inventors of the present invention can provide an LDH-containing functional layer that is excellent not only in ion conductivity but also in alkali resistance by constituting the LDH hydroxide basic layer mainly with Ni, Ti and OH groups. Obtained knowledge.

Therefore, an object of the present invention is to provide an LDH-containing functional layer that is excellent not only in ion conductivity but also in alkali resistance, and a composite material including the same.

According to one aspect of the present invention, a functional layer comprising a layered double hydroxide,
The layered double hydroxide is composed of Ni, Ti and OH groups, or a plurality of hydroxide basic layers composed of Ni, Ti, OH groups and inevitable impurities, and the plurality of hydroxide basic layers There is provided a functional layer composed of an intermediate layer composed of an anion and H ₂ O intervening.

According to another aspect of the invention, a porous substrate;
The functional layer provided on the porous substrate and / or incorporated into the porous substrate;
A composite material is provided comprising:

According to another aspect of the present invention, a battery including the functional layer or the composite material as a separator is provided.

It is a schematic cross section which shows one aspect | mode of the LDH containing composite material of this invention. It is a schematic cross section which shows the other one aspect | mode of the LDH containing composite material of this invention. It is a schematic diagram which shows a layered double hydroxide (LDH) plate-like particle. 2 is a schematic cross-sectional view showing an electrochemical measurement system used in Examples 1 and 2. FIG. It is a disassembled perspective view of the airtight container for measurement used in the denseness determination test of Examples 1 and 2. It is a schematic cross section of the measurement system used in the denseness determination test of Examples 1 and 2. It is a conceptual diagram which shows an example of the He permeability measurement system used in Examples 1 and 2. FIG. 6B is a schematic cross-sectional view of a sample holder used in the measurement system shown in FIG. 6A and its peripheral configuration. 2 is an X-ray diffraction result of a functional layer manufactured in Example 1. FIG. 2 is an SEM image showing a surface microstructure of a functional layer produced in Example 1. 3 is a SEM image showing a cross-sectional microstructure of a functional layer manufactured in Example 1. It is a SEM image which shows the surface microstructure of the functional layer produced in Example 1 before immersion in KOH aqueous solution, after 1 week immersion, and after 3 weeks immersion. It is the X-ray-diffraction result of the functional layer produced in Example 1 before immersion in KOH aqueous solution, after 1 week immersion, and after 3 week immersion. It is a SEM image which shows the surface microstructure of the functional layer produced in Example 2 (comparison). It is a SEM image which shows the cross-sectional microstructure of the functional layer produced in Example 2 (comparison). It is a SEM image which shows the surface microstructure of the functional layer of the functional layer produced in Example 2 (comparative) before immersion in KOH aqueous solution and after 1 week immersion. It is the X-ray-diffraction result of the functional layer produced in Example 2 (comparison) before immersion in KOH aqueous solution and after 1 week immersion.

LDH-containing functional layer and composite material The functional layer of the present invention is a layer containing a layered double hydroxide (LDH), and this LDH is formed between a plurality of hydroxide basic layers and the plurality of hydroxide basic layers. It consists of an intervening intermediate layer. The hydroxide base layer is composed of Ni, Ti, OH groups and possibly inevitable impurities. The intermediate layer is composed of an intermediate layer composed of an anion and H ₂ O. The alternately laminated structure of the hydroxide basic layer and the intermediate layer itself is basically the same as the generally known laminated structure of LDH. However, in the present invention, the hydroxide basic layer of LDH is mainly composed of Ni, Ti. By constituting with OH groups, it is possible to provide an LDH-containing functional layer excellent not only in ion conductivity but also in alkali resistance.

As described above, the alkali secondary battery LDH is desired to have a high alkali resistance that hardly deteriorates even in a strong alkaline electrolyte. In this respect, the functional layer of the present invention can exhibit excellent alkali resistance by constituting the hydroxide basic layer of LDH mainly with Ni, Ti and OH groups. Although the reason is not necessarily clear, it is considered that an element (for example, Al) that is considered to be easily eluted in an alkaline solution is not intentionally or actively added to the LDH of the present invention. Nevertheless, the functional layer of the present invention can also exhibit high ionic conductivity suitable for use as a separator for an alkaline secondary battery.

As described above, the hydroxide basic layer of LDH in the present invention is composed of Ni, Ti, OH groups, and possibly inevitable impurities. Ni in LDH can take the form of nickel ions. The nickel ions in LDH are typically considered to be Ni ²⁺ , but are not particularly limited because other valences such as Ni ³⁺ may also exist. Ti in LDH can take the form of titanium ions. The titanium ion in LDH is typically considered to be Ti ⁴⁺ , but is not particularly limited because other valences such as Ti ³⁺ may also exist. Inevitable impurities are optional elements that can be inevitably mixed in the manufacturing process, and can be mixed in LDH, for example, derived from raw materials and base materials. The intermediate layer of LDH included 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 anion in LDH comprises OH ^- and / or CO ₃ ^2- . As described above, since the valences of Ni and Ti are not necessarily certain, it is impractical or impossible to specify LDH strictly by a general formula. If it is assumed that the hydroxide base layer is mainly composed of Ni ²⁺ , Ti ⁴⁺ and OH groups, the corresponding LDH has the general formula: Ni ²⁺ _1-x Ti ⁴⁺ _x (OH) ₂ ^{An _{_{- 2x / n · mH 2 O}}} ( ^{wherein, a n-n-valent} anion, n is an integer of 1 or more, preferably 1 or 2, 0 <x <1, preferably 0.01 ≦ x ≦ 0.5, m is 0 or more, typically greater than 0 or 1 or more real number). However, the above general formula should be construed as “basic composition” only, and other elements or ions (other valences of the same element) to the extent that elements such as Ni ²⁺ and Ti ⁴⁺ do not impair the basic characteristics of LDH. It should be understood that it can be replaced by a number of elements or ions, or elements or ions that may be inevitably mixed in the manufacturing process.

When LDH contained in the functional layer is immersed in a 6 mol / L aqueous potassium hydroxide solution containing zinc oxide at a concentration of 0.4 mol / L at 70 ° C. for 3 weeks (ie, 504 hours), the surface microstructure and It is preferable that the crystal structure does not change because the alkali resistance is particularly excellent. The presence or absence of changes in the surface microstructure depends on the surface microstructure using an SEM (scanning electron microscope), and the presence or absence of changes in the crystal structure depends on crystal structure analysis using XRD (X-ray diffraction) (for example, (003) derived from LDH) This can be preferably performed depending on whether or not there is a peak shift.

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. The upper limit is not particularly limited, but is, for example, 10 mS / cm. Such high ionic conductivity is particularly suitable for battery applications. For example, for the practical application of LDH, it is desired to reduce the resistance by thinning the film. However, according to this embodiment, an LDH-containing functional layer having a low resistance can be provided. It is particularly advantageous in the application of LDH as a solid electrolyte separator for secondary batteries.

Preferably, the functional layer is provided on the porous substrate and / or is incorporated into the porous substrate. That is, according to a preferred aspect of the present invention, there is provided a composite material comprising a porous substrate and a functional layer provided on the porous substrate and / or incorporated into the porous substrate. For example, like the composite material 10 shown in FIG. 1, a part of the functional layer 14 may be incorporated in the porous substrate 12 and the remaining part may be provided on the porous substrate 12. At this time, the portion of the functional layer 14 on the porous substrate 12 is a film-shaped portion made of an 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 composite part. The composite part typically has a form in which the pores of the porous substrate 12 are filled with LDH. When the entire functional layer 14 ′ is incorporated in the porous substrate 12 as in the composite material 10 ′ shown in FIG. 2, the functional layer 14 ′ is mainly composed of the porous substrate 12 and LDH. It can be said that. 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. 1 and 2, the

functional layers

14 and 14 ′ are incorporated only in a part near the surface of the

porous base material

12 and 12 ′. However, the functional layer is incorporated in any part of the porous base material. In addition, the functional layer may be incorporated over the whole or the entire thickness of the porous substrate.

The porous base material in the composite material of the present invention is preferably capable of forming an LDH-containing functional layer on and / or in it, and the material and the porous structure are not particularly limited. Typically, the LDH-containing functional layer is formed on and / or in the porous substrate, but the LDH-containing functional layer is formed on the nonporous substrate, and then nonporous by various known methods. The porous substrate may be made porous. In any case, it is preferable that the porous base material has a porous structure having water permeability in that the electrolyte solution can reach the functional layer when incorporated in 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 kind. More preferably, the porous substrate is made of a ceramic material. In this case, preferable examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof, and 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 denseness. Preferred examples of the metal material include aluminum, zinc, and nickel. Preferred examples of the polymer material include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrophilic fluororesin (tetrafluorinated resin: PTFE, etc.), cellulose, nylon, polyethylene, and any combination thereof. Is mentioned. Any of the various preferred materials described above has alkali resistance as resistance to the electrolyte of the battery.

The porous substrate preferably has an average pore size of at most 100 μm or less, more preferably at most 50 μm, for example, typically 0.001 to 1.5 μm, more typically 0.001. 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. By being 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 for the porous substrate. In the present invention, the average pore diameter can be measured by measuring the longest distance of the pores based on the electron microscope image of the surface of the porous substrate. The magnification of the electron microscope image used for this measurement is 20000 times or more. 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, and 30 points per visual field are combined. The average pore diameter can be obtained by calculating an average value for two visual fields. 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%. By being 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 for the porous substrate. The porosity of the porous substrate can be preferably measured by the Archimedes method.

It is preferable that the functional layer does not have air permeability. That is, the functional layer is preferably densified with LDH to such an extent that it does not have air permeability. In the present specification, “non-breathable” refers to an object to be measured in water when the breathability is evaluated by a “denseness determination test” employed in the examples described later or a method or configuration equivalent thereto. This means that even if helium gas is brought into contact with one surface side (that is, the functional layer and / or the porous substrate) with a differential pressure of 0.5 atm, generation of bubbles due to helium gas is not observed from the other surface side. . By doing so, the functional layer or the composite material as a whole can selectively pass only hydroxide ions due to its hydroxide ion conductivity, and can exhibit a function as a battery separator. . When considering application of LDH as a solid electrolyte separator for a battery, there was a problem that a bulk LDH dense body had 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 thinned to reduce the resistance. Moreover, since the porous substrate can have water permeability and air permeability, the electrolyte can reach the LDH-containing functional layer when used as a battery solid electrolyte separator. That is, the LDH-containing functional layer and composite material of the present invention are used as solid electrolyte separators 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 including the functional layer preferably has a He permeability per unit area of 10 cm / min · atm or less, more preferably 5.0 cm / min · atm or less, and even more preferably 1.0 cm / min. It is below min · atm. It can be said that the functional layer having the He transmittance within such a range has extremely high density. Therefore, the functional layer having a He permeability of 10 cm / min · atm or less can prevent 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, permeation of zinc ions or zincate ions in the electrolytic solution can be extremely effectively suppressed. In this way, it is considered in principle that Zn permeation is remarkably suppressed, so that growth of zinc dendrites can be effectively suppressed when used in a zinc secondary battery. The He permeability is measured through a process of supplying He gas to one surface of the functional layer and allowing the He gas to pass through the functional layer, and a process of calculating the He permeability and evaluating the density of the functional layer. The The He permeability is expressed by the following formula: F / (P × S), using the He gas permeation amount F per unit time, the differential pressure P applied to the functional layer when He gas permeates, and the membrane area S through which He gas permeates. Calculated by Thus, by evaluating the gas permeability using He gas, it is possible to evaluate the presence or absence of denseness at a very high level, and as a result, substances other than hydroxide ions (especially zinc dendrite growth can be performed). It is possible to effectively evaluate a high degree of compactness such that Zn that is caused is not transmitted as much as possible (only a very small amount is transmitted). This is because the He gas has the smallest structural unit among a wide variety of atoms or molecules that can constitute the gas, and the reactivity is extremely low. That is, He forms He gas by a single He atom without forming a molecule. In this respect, since hydrogen gas is composed of H ₂ molecules, a single He atom is smaller as a gas constituent unit. In the first place, H ₂ gas is dangerous because it is a combustible gas. Then, by adopting the He gas permeability index defined by the above-described formula, objective evaluation regarding the denseness can be easily performed regardless of differences in various sample sizes and measurement conditions. In this way, it is possible to simply, safely and effectively evaluate whether or not the functional layer has a sufficiently high density suitable for a zinc secondary battery separator. The measurement of the He permeability can be preferably performed according to the procedure shown in Evaluation 5 of Examples described later.

LDH includes an aggregate of a plurality of plate-like particles (that is, LDH plate-like particles), and the plurality of plate-like particles are macroscopically such that the plate surface is a layer surface of the functional layer (the fine irregularities of the functional layer can be ignored). It is preferably oriented in a direction perpendicular to or obliquely intersecting the layer surface when observed. In addition, when a functional layer is provided on a porous base material, a functional layer has a film-like part provided on a porous base material. In this case, the LDH constituting the film-like portion includes an aggregate of a plurality of plate-like particles (that is, LDH plate-like particles), and the plate-like particles have a plate surface whose surface is porous (porous). It is preferably oriented in a direction that intersects perpendicularly or obliquely with the surface of the porous base material when the microscopic unevenness due to the structure is macroscopically observed to a negligible extent. In addition, when a functional layer has the composite part integrated in a porous base material, LDH plate-like particle | grains can exist also in the hole of a porous base material. Moreover, the film-like part may further contain ceramic particles such as alumina particles as a filler, whereby the adhesion strength between the LDH of the film-like part and the substrate can be increased.

The LDH crystal is known to have the form of a plate-like particle having a layered structure as shown in FIG. 3, but the above vertical or oblique orientation is extremely important for an LDH-containing functional layer (for example, an LDH dense film). This is an advantageous property. This is because an oriented LDH-containing functional layer (eg, an oriented LDH dense film) has a hydroxide ion conductivity perpendicular to this in the direction in which the LDH plate-like particles are oriented (ie, in a direction parallel to the LDH layer). This is because there is a conductivity anisotropy that is much higher than the conductivity in the direction. In fact, it is already known that in an oriented bulk body of LDH, the conductivity (S / cm) in the orientation direction is one digit higher than the conductivity (S / cm) in the direction perpendicular to the orientation direction. That is, the vertical or oblique orientation in the LDH-containing functional layer of the present invention indicates the conductivity anisotropy that the LDH oriented body can have in the layer thickness direction (that is, the direction perpendicular to the surface of the functional layer or porous substrate). As a result, the conductivity in the layer thickness direction can be maximized or significantly increased. In addition, since the LDH-containing functional layer has a layer form, lower resistance than that of the bulk form LDH can be realized. The LDH-containing functional layer having such an orientation is easy to conduct hydroxide ions in the layer thickness direction. In addition, since it is densified, it is extremely suitable for use in functional membranes such as battery separators (eg, hydroxide ion conductive separators for zinc-air batteries) where high conductivity in the layer thickness direction and denseness are desired. Suitable.

The functional layer preferably has a thickness of 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, particularly preferably 25 μm or less, and most preferably 5 μm or less. Such thinness can reduce the resistance of the functional layer. When the functional layer is formed as an LDH film on the porous substrate, the thickness of the functional layer corresponds to the thickness of the film-like portion made of the LDH film. Further, when the functional layer is formed by being incorporated in the porous substrate, the thickness of the functional layer corresponds to the thickness of the composite portion composed of the porous substrate and LDH. In addition, when a functional layer is formed over and in a porous base material, it corresponds to the total thickness of a film-like part (LDH film) and a composite part (porous base material and LDH). In any case, when 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 alignment film is not particularly limited because it varies depending on the application, but in order to ensure a certain degree of hardness desired as a functional film such as a separator, the thickness is preferably 1 μm or more. Preferably it is 2 micrometers or more.

The manufacturing method of the LDH-containing functional layer and the composite material is not particularly limited, and the LDH-containing functional layer and the composite material are manufactured by appropriately changing various conditions of the known LDH-containing functional layer and composite material manufacturing method (see, for example, Patent Documents 1 and 2). be able to. For example, (1) a porous substrate is prepared, (2) a titanium oxide sol is applied to the porous substrate and heat-treated to form a titanium oxide layer, and (3) nickel ions (Ni ²⁺ ) and urea are added. (4) Hydrothermal treatment of the porous substrate in the raw material aqueous solution to form an LDH-containing functional layer on the porous substrate and / or in the porous substrate. As a result, an LDH-containing functional layer and a composite material can be produced. In particular, by forming a titanium oxide layer on the porous substrate in the above step (2), it not only gives an LDH raw material, but also functions as a starting point for LDH crystal growth and is highly dense on the surface of the porous substrate. The formed LDH-containing functional layer can be uniformly formed without unevenness. In addition, the presence of urea in the above step (3) raises the pH value due to the generation of ammonia in the solution utilizing the hydrolysis of urea, and the coexisting metal ions form hydroxides. LDH can be obtained. Further, since carbon dioxide is generated in the hydrolysis, LDH in which the anion is carbonate ion type can be obtained.

The present invention will be described more specifically with reference to the following examples. In addition, the evaluation method of the functional layer and composite material produced in the following examples was as follows.

Evaluation 1 : Identification of functional layer The crystal phase of the functional layer was measured with an X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation) under the measurement conditions of voltage: 50 kV, current value: 300 mA, measurement range: 10 to 70 °. As a result, an XRD profile was obtained. About the obtained XRD profile, JCPDS card NO. Identification was performed using a 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 a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV. Further, after obtaining a cross-sectional polished surface of a functional layer (a film-shaped portion made of an LDH film and a composite portion made of LDH and a base material) with an ion milling device (manufactured by Hitachi High-Technologies Corporation, IM4000) The structure was observed by SEM under the same conditions as the observation of the surface microstructure.

Evaluation 3 : Elemental analysis evaluation (EDS)
Polishing was performed with a cross section polisher (CP) so that the cross-section polished surface of the functional layer (a film-like portion made of an LDH film and a composite portion made of LDH and a substrate) could be observed. With FE-SEM (ULTRA55, manufactured by Carl Zeiss), a cross-sectional image of the functional layer (a film-like portion made of an LDH film and a composite portion made of LDH and a base material) was obtained in one field of view at a magnification of 10,000 times. The elemental analysis of the LDH film on the substrate surface of this cross-sectional image and the LDH portion (point analysis) inside the substrate was performed with an EDS analyzer (NORAN System SIX, manufactured by Thermo Fisher Scientific) under the condition of an acceleration voltage of 15 kV. went.

Evaluation 4 : Evaluation of alkali resistance Zinc oxide was dissolved in a 6 mol / L potassium hydroxide aqueous solution to obtain a 6 mol / L potassium hydroxide aqueous solution containing zinc oxide at a concentration of 0.4 mol / L. 15 ml of the aqueous potassium hydroxide solution thus obtained was placed in a Teflon (registered trademark) sealed container. A composite material having a size of 1 cm × 0.6 cm was placed on the bottom of the sealed container so that the functional layer faced upward, and the lid was closed. Thereafter, after holding at 70 ° C. (Example 1) or 30 ° C. (Example 2) for 1 week (ie, 168 hours) or 3 weeks (ie, 504 hours), the composite material was removed from the sealed container. The removed composite material was dried overnight at room temperature. About the obtained sample, the microstructure observation by SEM and the crystal structure observation by XRD were performed.

Evaluation 5 : Measurement of ion conductivity The conductivity of the functional layer in the electrolytic solution was measured as follows using an electrochemical measurement system shown in FIG. The composite material sample S (porous substrate with LDH film) was sandwiched from both sides by 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 electrode 46, a # 100 mesh nickel wire mesh was incorporated into the cell 42 in a cylindrical shape having a diameter of 6 mm so that the distance between the electrodes was 2.2 mm. As the electrolytic solution 44, a 6 M KOH aqueous solution was filled in the cell 42. Using an electrochemical measurement system (potentiometer / galvano stud-frequency response analyzer, Solartron 1287A type and 1255B type), the frequency range is 1MHz to 0.1Hz, the applied voltage is 10mV, and the real axis intercept Was defined as the resistance of the composite material sample S (porous substrate 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 also obtained. The difference between the resistance of the composite material sample S (porous substrate with LDH film) and the resistance of only the substrate 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 the LDH.

Evaluation 6 : Denseness determination test A denseness determination test was performed as follows in order to confirm that the functional layer does not have air permeability. First, as shown in FIGS. 5A and 5B, an acrylic container 130 without a lid and an alumina jig 132 having a shape and size that can function as a lid for the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying gas therein. The alumina jig 132 is formed with an opening 132a having a diameter of 5 mm, and a sample placement recess 132b is formed along the outer periphery of the opening 132a. An epoxy adhesive 134 was applied to the depression 132b of the alumina jig 132, and the functional layer 136b side of the composite material sample 136 was placed on the depression 132b to adhere 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 a gas-tight and liquid-tight manner using a silicone adhesive 138 so as to completely close the open portion of the acrylic container 130. A measurement sealed container 140 was obtained. The measurement sealed container 140 was placed in a water tank 142, and the gas supply port 130 a of the acrylic container 130 was connected to a pressure gauge 144 and a 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 measurement sealed container 140 was completely submerged. At this time, the inside of the measurement sealed container 140 is sufficiently airtight and liquid tight, and the functional layer 136b side of the composite material sample 136 is exposed to the internal space of the measurement sealed container 140, while the composite material sample The porous substrate 136 a side of 136 is in contact with the water in the water tank 142. In this state, helium gas was introduced into the measurement sealed container 140 into the acrylic container 130 via the gas supply port 130a. The pressure gauge 144 and the flow meter 146 are controlled so that the differential pressure inside and outside the functional layer 136a becomes 0.5 atm (that is, the pressure applied to the side in contact with the helium gas is 0.5 atm higher than the water pressure applied to the opposite side). Whether or not helium gas bubbles were generated in the water from the composite material sample 136 was observed. As a result, when generation | occurrence | production of the bubble resulting from helium gas was not observed, it determined with the functional layer 136b having a high density so as not to have air permeability.

Evaluation 7 : He permeation measurement A He permeation test was performed as follows to evaluate the denseness of the functional layer from the viewpoint of He permeation. First, the He transmittance measurement system 310 shown in FIGS. 6A and 6B was constructed. The He permeability measurement system 310 is a function in which He gas from a gas cylinder filled with He gas is supplied to the sample holder 316 via the pressure gauge 312 and the flow meter 314 (digital flow meter), and is held in the sample holder 316. The layer 318 was configured to be transmitted from one surface to the other surface and discharged.

The sample holder 316 has a structure including a gas supply port 316a, a sealed space 316b, and a gas discharge port 316c, and was assembled as follows. First, an adhesive 322 was applied along the outer periphery of the functional layer 318 and attached to a jig 324 (made of ABS resin) having an opening at the center.

Support members

328a and 328b (made of PTFE) provided with gaskets made of butyl rubber as sealing

members

326a and 326b at the upper and lower ends of the jig 324 and further provided with openings formed from flanges from the outside of the sealing

members

326a and 326b. ). Thus, the sealed space 316b was partitioned by the functional layer 318, the jig 324, the sealing member 326a, and the support member 328a. The functional layer 318 is in the form of a composite material formed on the porous substrate 320, but the functional layer 318 is disposed so that the functional layer 318 side faces the gas supply port 316a. The

support members

328a and 328b were firmly fastened to each other by fastening means 330 using screws so that He gas leakage did not occur from a portion other than the gas discharge port 316c. The gas supply pipe 34 was connected to the gas supply port 316a of the sample holder 316 assembled in this way via a joint 332.

Next, He gas was supplied to the He permeability measurement system 310 via the gas supply pipe 334 and 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 permeation of He gas for 1 to 30 minutes, the He permeability was calculated. The calculation of the He permeability is based on the permeation amount of He gas per unit time F (cm ³ / min), the differential pressure P (atm) applied to the functional layer during He gas permeation, and the membrane area S (cm ² ) and calculated by the formula of F / (P × S). The permeation amount F (cm ³ / min) of He gas was directly read 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.

Example 1
A functional layer and a composite material containing Ni and Ti-containing LDH were prepared and evaluated by the following procedure.

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

For the obtained porous substrate, the porosity of the porous substrate was measured by the Archimedes method and found to be 40%.

Further, when the average pore diameter of the porous substrate was measured, it was 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 is 20000 times. All 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. An average value for two visual fields was calculated at 30 points to obtain an average pore diameter. For length measurement, the length measurement function of SEM software was used.

(2) Titanium oxide sol coat on porous substrate 0.2 ml of titanium oxide sol (M-6, manufactured by Taki Chemical Co., Ltd.) was applied onto the alumina porous substrate obtained in (1) above by spin coating. did. In spin coating, the titanium oxide sol was dropped onto the substrate rotated at 8000 rpm, and after 5 seconds, the rotation was stopped. The substrate was allowed to stand on a hot plate heated to 100 ° C. and dried for 1 minute. Thereafter, heat treatment was performed at 200 ° C. in an electric furnace. The titanium oxide layer thus formed had a thickness of about 100 nm.

(3) Preparation of raw material aqueous solution As raw materials, 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) are prepared. Nickel nitrate hexahydrate was weighed so as to be 0.015 mol / L, put into a beaker, and ion-exchanged water was added thereto to make a total volume of 75 ml. Urea weighed in a ratio of urea / NO ₃ ⁻ (molar ratio) = 16 was added thereto, and further stirred to obtain a raw material aqueous solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) sealed container (autoclave container, content of 100 ml, outer side is a stainless steel jacket) and the raw material aqueous solution prepared in (3) above and the substrate prepared in (2) above Was enclosed together. At this time, the base material was fixed by being floated from the bottom of a Teflon (registered trademark) sealed container, and placed horizontally so that the solution was in contact with both surfaces of the base material. Thereafter, hydrothermal treatment was performed at a hydrothermal temperature of 150 ° C. for 72 hours (3 days) to form LDH on the substrate surface and inside. After a lapse of a predetermined time, the substrate was taken out from the sealed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a part of the functional layer containing LDH was 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 7 were performed on the obtained functional layers or composite materials. The results were as follows.
-Evaluation 1: The XRD profile shown in FIG. 7 was obtained. From this XRD profile, it was identified that the functional layer was LDH (hydrotalcite compound). FIG. 7 also shows a peak derived from alumina constituting the porous substrate.
-Evaluation 2: The SEM images of the surface microstructure and the cross-sectional microstructure of the functional layer were as shown in FIGS. 8A and 8B, respectively. As shown in FIG. 8B, it was found that the functional layer was composed of a film-shaped portion made of an LDH film and a composite portion made of LDH and a porous substrate located under the film-shaped portion. The LDH constituting the film-like portion is composed of an aggregate of a plurality of plate-like particles, and the plurality of plate-like particles have their plate surfaces on the surface of the porous substrate (fine irregularities due to the porous structure). It was oriented in a direction perpendicular to or obliquely intersecting the surface of the porous substrate when observed macroscopically to a negligible extent. On the other hand, the composite part constituted a dense layer by filling the pores of the porous substrate with LDH.
-Evaluation 3: As a result of EDS elemental analysis, LDH constituent elements C, Ti, and Ni were detected in both LDH contained in the functional layer, that is, the LDH film on the substrate surface and the LDH portion in the substrate. . That is, Ti and Ni are constituent elements of the hydroxide basic layer, while C corresponds to CO ₃ ²⁻ which is an anion constituting the intermediate layer of LDH.
-Evaluation 4: The SEM image which image | photographed the surface microstructure of the functional layer before being immersed in KOH aqueous solution, after being immersed for 1 week, and after being immersed for 3 weeks was as shown in FIG. As can be seen from FIG. 9, the microstructure of the functional layer was not changed even after being immersed in an aqueous potassium hydroxide solution at 70 ° C. for 3 weeks. Further, the results of X-ray diffraction of the functional layer before immersion in an aqueous KOH solution, after immersion for 1 week, and after immersion for 3 weeks were as shown in FIG. As can be seen from FIG. 10, no change was observed in the crystal structure even after immersion in an aqueous potassium hydroxide solution at 70 ° C. for 3 weeks. In particular, the position of the (003) peak of LDH contained in the functional layer was 2θ = 11.34 in any functional layer before immersion in the KOH aqueous solution, after immersion for 1 week, and after immersion for 3 weeks.
-Evaluation 5: The ionic conductivity of the functional layer was 2.2 mS / cm, which was the same level as Example 2 which is a comparative example described later.
-Evaluation 6: It was confirmed that the functional layer and the composite material have high denseness that does not have air permeability.
-Evaluation 7: The He permeability of the functional layer and the composite material was 0.0 cm ³ / min · atm.

Example 2 (Comparison)
A functional layer and a composite material containing Mg and Al-containing LDH were prepared and evaluated by the following procedure.

(1) Production of porous substrate A porous substrate made of alumina was produced in the same manner as in step (1) in Example 1.

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

(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 nonahydrate 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. In a beaker, ion exchange water was added to make a total volume of 70 ml. After stirring the obtained solution, urea weighed at a ratio of urea / NO ₃ ⁻ (molar ratio) = 4 was added to the solution, and further stirred to obtain a raw material aqueous solution.

(4) Film formation by hydrothermal treatment A Teflon (registered trademark) sealed container (with an internal volume of 100 ml, the outside is a stainless steel jacket) and 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 fixed by being floated from the bottom of a Teflon (registered trademark) sealed container, and placed horizontally so that the solution was in contact with both surfaces of the base material. Thereafter, a hydrothermal treatment was performed at a hydrothermal temperature of 70 ° C. for 168 hours (7 days) to form an LDH alignment film on the substrate surface. After a lapse of a predetermined time, the substrate was taken out from the sealed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a part of the functional layer containing LDH was incorporated into the porous substrate. Got in shape. The thickness of the functional layer obtained was about 3 μm (including the thickness of the portion incorporated in the porous substrate).

(5) Evaluation results Evaluations 1 to 7 were performed on the obtained functional layers or composite materials. 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 images of the surface microstructure and the cross-sectional microstructure of the functional layer were as shown in FIGS. 11A and 11B, respectively. In almost the same manner as the functional layer obtained in Example 1, a functional layer composed of a film-shaped portion made of an LDH film and a composite portion made of LDH and a porous substrate located under the film-shaped 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 contained in the functional layer, that is, the LDH film on the substrate surface and the LDH portion in the substrate. . That is, Mg and Al are constituent elements of the hydroxide basic layer, while C corresponds to CO ₃ ²⁻ which is an anion constituting the intermediate layer of LDH.
-Evaluation 4: The SEM image which image | photographed the surface microstructure of the functional layer before the immersion in KOH aqueous solution and after 1 week immersion was as being shown in FIG. As can be seen from FIG. 12, even after one week immersion in a 30 ° C. aqueous potassium hydroxide solution lower than 70 ° C. in Example 1 (ie even under milder alkaline conditions than in Example 1), the microstructure of the functional layer There was a change. Moreover, the X-ray-diffraction result of the functional layer before immersion in the KOH aqueous solution and after 1 week immersion was as shown in FIG. As can be seen from FIG. 13, even after soaking for 1 week in a 30 ° C. aqueous potassium hydroxide solution lower than 70 ° C. in Example 1 (ie, even under milder alkaline conditions than in Example 1), the crystal structure changes. It was seen. 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 1 week. It was. This shift of the (003) peak can suggest that Al contained in LDH is eluted into the KOH aqueous solution and deteriorates LDH. From these results, the functional layer of Example 2 is inferior in alkali resistance to the functional layer of Example 1, that is, the functional layer of Example 1 which is an example of the present invention is more excellent in alkali resistance than the functional layer of Example 2 which is a comparative example. I understood that.
-Evaluation 5: The conductivity of the functional layer was 2.0 mS / cm.
-Evaluation 6: It was confirmed that the functional layer and the composite material have high denseness that does not have air permeability.
-Evaluation 7: The He permeability of the functional layer and the composite material was 0.0 cm ³ / min · atm.

Claims

A functional layer comprising a layered double hydroxide,
The layered double hydroxide is composed of Ni, Ti and OH groups, or a plurality of hydroxide basic layers composed of Ni, Ti, OH groups and inevitable impurities, and the plurality of hydroxide basic layers A functional layer composed of an intermediate layer composed of an anion and H 2 O intervening in
The functional layer according to claim 1, wherein the functional layer has hydroxide ion conductivity.
The functional layer according to claim 1 or 2, wherein the functional layer has an ionic conductivity of 0.1 mS / cm or more.
When the layered double hydroxide is immersed in a 6 mol / L potassium hydroxide aqueous solution containing zinc oxide at a concentration of 0.4 mol / L for 3 weeks at 70 ° C., the surface microstructure and crystal structure change. The functional layer according to any one of claims 1 to 3, which does not occur.
The layered double hydroxide includes an aggregate of a plurality of plate-like particles, and the plurality of plate-like particles are oriented in a direction such that their plate surfaces perpendicularly or obliquely intersect the layer surface of the functional layer. The functional layer according to any one of claims 1 to 4, wherein:
The functional layer according to any one of claims 1 to 5, wherein the functional layer has a He permeability per unit area of 10 cm / min · atm or less.
The functional layer according to any one of claims 1 to 6, wherein the functional layer has a thickness of 100 µm or less.
The functional layer according to any one of claims 1 to 6, wherein the functional layer has a thickness of 50 µm or less.
The functional layer according to any one of claims 1 to 6, wherein the functional layer has a thickness of 5 μm or less.
A porous substrate;
The functional layer according to any one of claims 1 to 9, provided on the porous substrate and / or incorporated in the porous substrate;
Including composite materials.
The composite material according to claim 10, wherein the porous substrate is composed of at least one selected from the group consisting of a ceramic material, a metal material, and a polymer material.
The functional layer has a film-like part provided on the porous substrate, and the layered double hydroxide constituting the film-like part includes an aggregate of a plurality of plate-like particles, and the plurality of plate-like parts The composite material according to claim 10 or 11, wherein the particles are oriented such that their plate surfaces intersect perpendicularly or obliquely with the surface of the porous substrate.
The composite material according to any one of claims 10 to 12, wherein the He permeation rate per unit area is 10 cm / min · atm or less.
A battery comprising the functional layer according to any one of claims 1 to 9 or the composite material according to any one of claims 10 to 13 as a separator.