JP6771073B2 - Electrolytes for electrochemical cells and electrochemical cells - Google Patents

Description

The present invention relates to an electrolyte for an electrochemical cell and an electrochemical cell.

Conventionally, in an electrochemical cell such as an alkaline fuel cell, an alkaline secondary battery, and an electrolytic cell, an ionic conductor having ionic conductivity is used as an electrolyte (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-071948

However, in the above-mentioned electrochemical cell, since the electrolyte is used in the presence of water (or water vapor), the volume of the electrolyte changes depending on the water content in the electrolyte. Therefore, the electrolyte may be peeled off from the cathode and / and the anode, or the electrolyte itself may be deformed.

An object of the present invention is to provide an electrolyte for an electrochemical cell capable of suppressing peeling or deformation, and an electrochemical cell capable of suppressing peeling or deformation of the electrolyte.

The electrolyte for an electrochemical cell according to the present invention includes a porous base material, an ionic conductor, and closed pores. The porous substrate has a three-dimensional network structure and forms continuous pores. The ionic conductor has ionic conductivity and is arranged in a continuous hole. Voids are formed in the ionic conductor. The porous substrate is composed of a metallic material. The closed pores are in contact with the porous substrate.

According to the present invention, it is possible to provide an electrolyte for an electrochemical cell capable of suppressing peeling or deformation, and an electrochemical cell capable of suppressing peeling or deformation of the electrolyte.

Cross-sectional view schematically showing the configuration of a solid alkaline fuel cell Schematic diagram showing an enlarged cross section of the electrolyte according to the first embodiment. Schematic diagram showing an enlarged cross section of the electrolyte according to the second embodiment. Schematic diagram showing an enlarged cross section of the electrolyte according to the third embodiment.

1. 1. 1st Embodiment (Solid alkaline fuel cell 10)
Hereinafter, as an example of an electrochemical cell to which the electrolyte for an electrochemical cell according to the present invention is applied, the first embodiment of a solid alkaline fuel cell 10 which is a kind of alkaline fuel cell (AFC) having a hydroxide ion as a carrier The form will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the configuration of the solid alkaline fuel cell 10 according to the embodiment. The solid alkaline fuel cell 10 includes a cathode 12, an anode 14, and an electrolyte 16 (an example of "electrolyte for an electrochemical cell"). The solid alkaline fuel cell 10 generates electricity at a relatively low temperature (for example, 50 ° C. to 250 ° C.) based on the following electrochemical reaction formula. However, in the following electrochemical reaction formula, the case where methanol is used as an example of fuel is exemplified.

・ Cathode 12: 3 / 2O ₂ + 3H ₂ O + 6e ⁻ → 6OH ⁻
・ Anode 14: CH ₃ OH + 6OH ⁻ → 6e ⁻ + CO ₂ + 5H ₂ O
・ Overall: CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O

The cathode 12 is an anode generally called an air electrode. During power generation of the solid alkaline fuel cell 10, an oxidizing agent containing oxygen (O ₂ ) is supplied to the cathode 12 via the oxidizing agent supplying means 13. As the oxidizing agent, it is preferable to use air, and it is more preferable that the air is humidified. The cathode 12 is a porous body capable of diffusing an oxidizing agent inside. The porosity of the cathode 12 is not particularly limited. The thickness of the cathode 12 is not particularly limited, but can be, for example, 10 to 200 μm.

The cathode 12 is not particularly limited as long as it contains a known air electrode catalyst used for AFC. Examples of cathode catalysts include group 8-10 elements (IUPAC format periodic table) such as group 11 elements (Ru, Rh, Pd, Ir, Pt) and group 11 elements (Fe, Co, Ni). Group 10 elements), Group 11 elements such as Cu, Ag, and Au (elements belonging to Group 11 in the periodic table in the IUPAC format), rhodium phthalocyanine, tetraphenylporphyrin, Co-salen, Ni-salen (salen = N, N'-bis (salicylidene) ethylenediamine), silver nitrate, and any combination thereof. The amount of the catalyst supported on the cathode 12 is not particularly limited, but is preferably 0.05 to 10 mg / cm ² , more preferably 0.05 to 5 mg / cm ² . The cathode catalyst is preferably supported on carbon. Preferred examples of the cathode 12 or the catalyst constituting the cathode 12 are platinum-supported carbon (Pt / C), platinum-cobalt-supported carbon (PtCo / C), palladium-supported carbon (Pd / C), and rhodium-supported carbon (Rh / C). , Nickel-supported carbon (Ni / C), copper-supported carbon (Cu / C), and silver-supported carbon (Ag / C).

The method for producing the cathode 12 is not particularly limited, and for example, the cathode catalyst and, if desired, the carrier may be mixed with a binder to form a paste, and the paste-like mixture may be applied to the cathode side surface 16S of the electrolyte 16. it can.

The anode 14 is a cathode generally called a fuel electrode. During power generation of the solid alkaline fuel cell 10, fuel containing a hydrogen atom (H) is supplied to the anode 14 via the fuel supply means 15. The anode 14 is a porous body capable of diffusing fuel inside. The porosity of the anode 14 is not particularly limited. The thickness of the anode 14 is not particularly limited, but can be, for example, 10 to 500 μm.

The fuel may contain a fuel compound capable of reacting with hydroxide ions (OH ⁻ ) at the anode 14, and may be in the form of either liquid fuel or gaseous fuel.

Examples of the fuel compound include (i) hydrazine (NH ₂ NH ₂ ), hydrated hydrazine (NH ₂ NH ₂ · H ₂ O), hydrazine carbonate ((NH ₂ NH ₂ ) ₂ CO ₂ ), and hydrazine sulfate (NH). ₂ NH ₂ · H ₂ SO ₄ ), monomethylhydrazine (CH ₃ NHNH ₂ ), dimethylhydrazine ((CH ₃ ) ₂ NNH ₂ , CH ₃ NHNHCH ₃ ), and hydrazines such as carboxylic hydrazine ((NHNH ₂ ) ₂ CO). Class, (ii) urea (NH ₂ CONH ₂ ), (iii) ammonia (NH ₃ ), (iv) imidazole, 1,3,5-triazine, 3-amino-1,2,4-triazole and other heterocycles. Examples thereof include hydroxylamines such as (v) hydroxylamine (NH ₂ OH) and hydroxylamine sulfate (NH ₂ OH · H ₂ SO ₄ ), and combinations thereof. Of these fuel compounds, carbon-free compounds (ie, hydrazine, hydrated hydrazine, hydrazine sulfate, ammonia, hydroxylamine, hydroxylamine sulfate, etc.) are particularly suitable because they do not have the problem of catalyst poisoning by carbon monoxide. is there.

The fuel compound may be used as a fuel as it is, or may be used as a solution dissolved in water and / or an alcohol (for example, a lower alcohol such as methanol, ethanol, propanol or isopropanol). For example, among the above fuel compounds, hydrazine, hydrated hydrazine, monomethylhydrazine and dimethylhydrazine are liquids and can be used as they are as liquid fuels. In addition, hydrazine carbonate, hydrazine sulfate, carboxylic hydrazine, urea, imidazole, and 3-amino-1,2,4-triazole, and hydroxylamine sulfate are solid but soluble in water. 1,3,5-triazine and hydroxylamine are solid but soluble in alcohol. Ammonia is a gas but is soluble in water. As described above, the solid fuel compound can be dissolved in water or alcohol and used as a liquid fuel. When the fuel compound is dissolved in water and / or alcohol and used, the concentration of the fuel compound in the solution is, for example, 30 to 99.9% by weight, preferably 66 to 99.9% by weight.

Further, a hydrocarbon-based liquid fuel containing alcohols such as methanol and ethanol and ethers, a hydrocarbon-based gas such as methane, or pure hydrogen can be used as it is as a fuel. In particular, methanol is preferable as the fuel used in the solid alkaline fuel cell 10 according to the present embodiment. Methanol may be in a gaseous state, a liquid state, or a gas-liquid mixed state.

The anode 14 is not particularly limited as long as it contains a known anode catalyst used for AFC. Examples of anode catalysts include metal catalysts such as Pt, Ni, Co, Fe, Ru, Sn, and Pd. The metal catalyst is preferably supported on a carrier such as carbon, but may be in the form of an organic metal complex having a metal atom of the metal catalyst as a central metal, or the organic metal complex may be supported as a carrier. Further, a diffusion layer made of a porous material or the like may be arranged on the surface of the anode catalyst. Preferred examples of the anode 14 and the catalysts constituting the anode 14 are nickel, cobalt, silver, platinum-supported carbon (Pt / C), platinum-luthenium-supported carbon (PtRu / C), palladium-supported carbon (Pd / C), and rhodium-supported. Examples thereof include carbon (Rh / C), nickel-supported carbon (Ni / C), copper-supported carbon (Cu / C), and silver-supported carbon (Ag / C).

The method for producing the anode 14 is not particularly limited, but for example, the anode catalyst and, if desired, the carrier may be mixed with a binder to form a paste, and the paste-like mixture may be applied to the anode-side surface 16T of the electrolyte 16. it can.

The electrolyte 16 is arranged between the cathode 12 and the anode 14. The electrolyte 16 is connected to each of the cathode 12 and the anode 14. The electrolyte 16 is formed in the form of a film, a layer, or a sheet.

FIG. 2 is a schematic view showing an enlarged cross section of the electrolyte 16 according to the first embodiment. The electrolyte 16 has a porous base material 20 and an inorganic solid electrolyte 22.

The porous base material 20 forms continuous pores 20a. The continuous holes 20a are formed so as to be continuous with the front and back surfaces of the porous base material 20. The continuous pores 20a are impregnated with the inorganic solid electrolyte 22 described later.

The porous base material 20 is made of a metal material. As the metal material constituting the porous base material 20, stainless steel (Fe—Cr alloy, Fe—Ni—Cr alloy, etc.), aluminum, zinc, nickel, titanium, or the like can be used. Since such a metal material has higher thermal conductivity than a ceramic material or a polymer material, it is possible to improve the heat dissipation efficiency of the porous base material 20 and reduce the temperature distribution in the porous base material 20. Can be made to.

The porous base material 20 may have a three-dimensional network structure. The "three-dimensional network structure" is a structure in which the constituent substances of the base material are three-dimensionally and network-likely connected. Examples of the porous base material 20 having a three-dimensional network structure include a cell-like or monolithic structure made of a porous metal material (for example, a foamed metal material) and a mesh shape made of a fine wire metal material. Examples include lumps and metal non-woven fabrics.

The porous base material 20 does not have to have a three-dimensional network structure. The porous base material 20 having no three-dimensional network structure includes a mesh member formed by weaving a plurality of wire rods made of a metal material, and a thin metal plate having a plurality of fine straight holes formed therein. Can be mentioned. The mesh member may be formed in a sheet shape as a whole. The weave of the wire may be plain weave, twill weave, plain weave, twill weave, or other weave. When a mesh member is used as the porous base material 20, the gap (that is, the opening) of each wire rod becomes a continuous hole 20a. The straight holes of the thin metal plate can be formed by, for example, laser processing. When a thin metal plate is used as the porous base material 20, the straight holes become continuous holes 20a.

An insulating film may be formed on the surface of the porous base material 20 (including the inner surface of the continuous pores 20a). The insulating film may be a passivation film formed by a passivation treatment of the base metal, or may be made of oxides such as Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, and Mg Al ₂ O ₄ . It may be a constituent oxide film. When constituting the porous substrate 20 by stainless steel, by oxidizing the stainless steel, it can be easily formed a Cr ₂ O ₃ film as an insulating film. However, in the present embodiment, since the first and second film-like portions 22b and 22c, which will be described later, function as an insulating film between the cathode 12 and the anode 14, the surface of the porous base material 20 has an insulating film. May not be formed.

The thickness of the porous base material 20 is not particularly limited, but can be, for example, 200 μm or less, preferably 100 μm or less, more preferably 75 μm or less, and most preferably 50 μm or less. The lower limit of the thickness of the porous base material 20 may be appropriately set according to the intended use, but is preferably 10 μm or more, more preferably 15 μm or more in order to secure a certain degree of hardness.

The average inner diameter of the continuous holes 20a in the cross section of the porous base material 20 is not particularly limited, but can be, for example, 1 to 1000 μm, preferably 2 to 500 μm, more preferably 5 to 400 μm, still more preferably 7 to 300 μm. , Particularly preferably 10 to 200 μm. By setting the content within these ranges, the density of the inorganic solid electrolyte 22 can be improved while imparting strength as a support to the porous base material 20. The average inner diameter of the continuous holes 20a is obtained by arithmetically averaging the circle-equivalent diameters of the continuous holes 20a at 20 randomly selected positions on the observation image when the cross section of the porous substrate 20 is observed with an electron microscope. Be done. The circle-equivalent diameter of the continuous hole 20a is the diameter of a circle having the same area as the cross-sectional area of the continuous hole 20a in the observation image. The magnification of the electron microscope may be appropriately set according to the cross-sectional size of the continuous hole 20a.

The volume fraction of the continuous hole 20a is not particularly limited, but can be, for example, 10 to 60%, preferably 15 to 55%, and more preferably 20 to 50%. Within these ranges, the density of the inorganic solid electrolyte 22 can be improved while ensuring the strength of the porous base material 20 as a support. The volume fraction of the continuous hole 20a can be measured by the Archimedes method.

Further, although not shown in FIG. 2, the porous base material 20 preferably has a plurality of pores inside itself. The plurality of pores may be connected to each other inside the porous base material 20. It is more preferable that each pore is an open pore that opens on the surface of the porous base material 20, and each pore is impregnated with the inorganic solid electrolyte 22. As a result, a short-distance ion conduction path of continuous pores 20a → pores in the porous base material 20 → continuous pores 20a, continuous pores 20a → pores in the porous base material 20, → second film-like portion 22c, or , The long-distance ion conduction path of the first film-like portion 22b → the pores in the porous substrate 20 → the second film-like portion 22c can be formed. As a result, the ionic conductive region in the composite portion 22a is widened, so that the ionic conductivity of the electrolyte 16 as a whole can be improved. When the porous base material 20 is made of a porous metal material, a plurality of pores can be easily provided inside the porous base material 20.

The inorganic solid electrolyte body 22 has hydroxide ion conductivity. During the power generation of the solid alkaline fuel cell 10, the inorganic solid electrolyte 22 conducts hydroxide ions (OH ⁻ ) from the cathode 12 side to the anode 14 side. The hydroxide ion conductivity of the inorganic solid electrolyte 22 is not particularly limited, but is preferably 0.1 mS / cm or more, more preferably 0.5 mS / cm or more, and further preferably 1.0 mS / cm or more. The higher the hydroxide ion conductivity of the inorganic solid electrolyte 22 is, the more preferable it is, and the upper limit thereof is not particularly limited, but is, for example, 10 mS / cm.

The inorganic solid electrolyte body 22 can be made of a ceramic material having hydroxide ion conductivity. As such a ceramic material, well-known ceramics having hydroxide ion conductivity can be used, but layered double hydroxide (LDH) described below is particularly suitable.

LDH is M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ x / n · mH ₂ O (in the formula, M ²⁺ is a divalent cation, M ³⁺ is a trivalent cation, and A ^The basic composition represented by the general formula of ⁿ⁻ is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is an arbitrary integer meaning the number of moles of water). Have. Examples of M ²⁺ include Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ni ²⁺ , Co ²⁺ , Fe ²⁺ , Mn ²⁺ , and Zn ²⁺ , and examples of M ³⁺ include Al ³⁺ , Fe ³⁺ , Ti ³⁺ , ^{Y 3+, Ce 3+, Mo 3+} , and ^{Cr 3+} can be mentioned, An ^- and the like ^- _CO ^{3 2-and} OH examples of. As M ²⁺ and M ³⁺ , one type may be used alone or two or more types may be used in combination.

LDH is composed of a plurality of basic hydroxide layers and an intermediate layer interposed between the plurality of basic hydroxide layers. Intermediate layer is composed of an anion and _{H 2} O. The hydroxide basic layer contains, for example, Ni, Al, Ti and OH groups when the metal M is Ni, Al, Ti. Hereinafter, the case where the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups will be described.

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. The hydroxide basic layer preferably contains Ni, Al, Ti and OH groups as main constituent elements, but may contain other elements or ions, or may contain unavoidable impurities. The unavoidable impurity is an arbitrary element that can be unavoidably mixed in the production method, and can be mixed in LDH, for example, derived from a raw material or a base material.

Intermediate layer of LDH is composed of anionic 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- .

As described above, since the valences of Ni, Al and Ti are not always fixed, it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the basic hydroxide layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ and OH groups, LDH is expressed by the general formula: Ni ²⁺ _1-xy Al ³⁺ _x Ti ⁴⁺ _y (OH). _{^{) 2 a n- (x + 2y}} ) / 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, 0 <y <1, preferably 0.01 ≦ y ≦ 0.5, 0 <x + y <1, m is 0 or more, typically more than 0 or 1 or more It can be expressed by the basic composition (which is a real number of). However, the above general formula should be understood as "basic composition" to the extent that elements such as Ni ²⁺ , Al ³⁺ , and Ti ⁴⁺ do not impair the basic characteristics of LDH, and other elements or ions (of the same element). It should be understood as replaceable with elements or ions of other valences or elements or ions that can be unavoidably mixed in the process.

In the present embodiment, the inorganic solid electrolyte body 22 has a composite portion 22a (an example of an “ionic conductor”), a first membrane-like portion 22b, and a second membrane-like portion 22c.

The composite portion 22a is arranged between the first film-like portion 22b and the second film-like portion 22c. The composite portion 22a is arranged in the continuous pores 20a of the porous base material 20. The composite portion 22a is impregnated in the continuous pores 20a and is integrated with the porous base material 20. By supporting the inorganic solid electrolyte 22 with the porous base material 20 in this way, the strength of the inorganic solid electrolyte 22 can be improved, so that the inorganic solid electrolyte 22 can be made thinner. As a result, the resistance of the electrolyte 16 can be reduced.

Here, the composite portion 22a has a plurality of closed pores 24 formed therein. Since such closed pores 24 are formed inside the composite portion 22a, it is possible to alleviate the volume change of the electrolyte 16 due to the change in the water content of the composite portion 22a during the operation of the solid alkaline fuel cell 10. it can. As a result, it is possible to suppress the generation of stress at the interface between the cathode 12 and the electrolyte 16 and / or the interface between the anode 14 and the electrolyte 16, so that the electrolyte 16 may peel off from the cathode 12 and / and the anode 14. Alternatively, it is possible to prevent the electrolyte 16 itself from being deformed.

Further, since the closed pores 24 are formed inside the composite portion 22a, the composite portion 22a can be provided with flexibility. Therefore, due to the temperature distribution in the solid alkaline fuel cell 10, the cathode 12 and the cathode 12 It is possible to suppress the generation of thermal stress at the interface with the electrolyte 16 and / or the interface between the anode 14 and the electrolyte 16. Therefore, it is possible to prevent the electrolyte 16 from peeling off from the cathode 12 and / and the anode 14 or the electrolyte 16 itself from being deformed.

As shown in FIG. 2, the closed pores 24 are preferably in contact with the porous base material 20. That is, it is preferable that the closed pores 24 are in direct contact with the inner surface of the continuous pores 20a. As a result, the restricted area of the porous base material 20 due to the presence of the closed pores 24 can be reduced as compared with the case where the closed pores 24 are separated from the porous base material 20, so that the flexibility of the porous base material 20 itself can be reduced. Can be improved. Therefore, when the volume of the electrolyte 16 is changed or deformed, it is possible to further suppress the generation of stress at the interface between the cathode 12 and the electrolyte 16 and / or the interface between the anode 14 and the electrolyte 16.

The average circle-equivalent diameter of each closed hole 24 is not particularly limited, but can be, for example, 0.001 to 1.0 μm. The average circle-equivalent diameter of each closed hole 24 is preferably 0.001 μm or more, and more preferably 0.002 μm or more. Thereby, the flexibility of the composite portion 22a can be further improved. The average circle-equivalent diameter of each of the closed pores 24 is preferably 1.0 μm or less, more preferably 0.8 μm or less. As a result, it is possible to prevent the oxidizing agent supplied to the cathode 12 from permeating to the anode 14 side or the fuel supplied to the anode 14 from permeating to the cathode 12 side.

For the average equivalent circle diameter of each closed pore 24, the cross section of the electrolyte 16 was observed with an electron microscope at a magnification of 20,000 to 1,500,000 times, and the equivalent circle diameter of 20 randomly selected closed pores 24 was calculated. Obtained by averaging. The circle-equivalent diameter of the closed pore 24 is the diameter of a circle having the same area as the closed pore 24 in the cross section of the electrolyte 16. However, since the closed pores 24 having a circular equivalent diameter of 0.001 μm or less have an extremely small contribution to mitigating the volume change and improving the flexibility of the composite portion 22a, when determining the average circular equivalent diameter of each closed pore 24, Shall be excluded.

The number of closed pores 24 can be determined from the number of closed pores 24 present in the observation field of view by observing the fracture surface of the electrolyte 16 with an electron microscope of 20,000 to 1,500,000 times. However, since the closed pores 24 having a diameter equivalent to a circle of 0.001 μm or less have an extremely small contribution to improving the flexibility of the composite portion 22a, they are excluded when determining the number of the closed pores 24.

The first film-like portion 22b is connected to the cathode 12 side of the composite portion 22a. The first film-like portion 22b is formed in a film-like shape. The first film-like portion 22b is integrally formed with the composite portion 22a. The first film-like portion 22b may be formed in a uniform planar shape, or may be patterned in a desired planar shape such as a striped shape. The thickness of the first film-like portion 22b is not particularly limited, but can be, for example, 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. By providing such a first film-like portion 22b, the contact resistance between the cathode 12 and the electrolyte 16 can be reduced as compared with the case where the cathode 12 and the porous base material 20 are in direct contact with each other. ..

The second film-like portion 22c is connected to the anode 14 side of the composite portion 22a. The second film-like portion 22c is formed in a film-like shape. The second film-like portion 22c is integrally formed with the composite portion 22a. The second film-like portion 22c may be formed in a uniform planar shape, or may be patterned in a desired planar shape such as a striped shape. The thickness of the second film-like portion 22c is not particularly limited, but can be, for example, 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. By providing such a second film-like portion 22c, the contact resistance between the anode 14 and the electrolyte 16 can be reduced as compared with the case where the anode 14 and the porous base material 20 are in direct contact with each other. ..

The method for producing the inorganic solid electrolyte 22 is not particularly limited, but when the inorganic solid electrolyte 22 is composed of LDH and the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups, the following It can be produced by the steps (1) to (4) of.

(1) Prepare the porous base material 20.

(2) The entire porous base material 20 is impregnated with a mixed sol of alumina and titania and heat-treated to form an alumina-titania layer. Here, as will be described later, in order to prevent LDH from growing from a part of the surface of the porous base material 20, an alumina titania layer is formed on at least a part of the inner surface of the continuous pores 20a of the porous base material 20. It is important to provide a part that does not form. Therefore, a part of the alumina-titania layer formed by applying ultrasonic waves to the porous base material 20 after being impregnated with the mixed sol and heat-treated is peeled off, or the mixed sol of alumina and titania is set to a low concentration to form a porous group. Measures such as reducing the amount of adhesion of the material 20 to the surface are taken.

(3) The porous base material 20 is immersed in a raw material aqueous solution containing nickel ions (Ni ²⁺ ) and urea.

(4) By hydrothermally treating the porous base material 20 in the raw material aqueous solution (100 to 150 degrees, 10 to 100 hours) to form LDH on the porous base material 20 and in the porous base material 20. An inorganic solid electrolyte 22 having a composite portion 22a, a first film-like portion 22b, and a second film-like portion 22c is formed. At this time, by appropriately adjusting the hydrothermal treatment time and the solution concentration, the closed pores 24 can be formed in the composite portion 22a by stopping the reaction before the pores are closed. Since LDH grows around the alumina-titania layer formed on the surface of the porous base material 20, LDH is not formed on the surface of the porous base material 20 where the alumina-titania layer is not formed. As a result, the closed pores 24 can be brought into direct contact with the porous substrate 20.

2. Second Embodiment Hereinafter, the second embodiment of the solid alkaline fuel cell 10 will be described with reference to the drawings. The difference from the first embodiment is that the inorganic solid electrolyte 22 does not include the first and second film-like portions 22b and 22c (see FIG. 2). Therefore, the differences will be mainly described below.

FIG. 3 is a schematic view showing an enlarged cross section of the electrolyte 17 according to the second embodiment. The electrolyte 17 has a porous base material 20 and an inorganic solid electrolyte body 26.

The configuration of the porous base material 20 is as described in the first embodiment, but since the porous base material 20 is in contact with each of the cathode 12 and the anode 14, the surface of the porous base material 20 is covered. Needs to form an insulating film. The insulating film can be composed of Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, Mg Al ₂ O _{4, and the} like.

The inorganic solid electrolyte body 26 does not include the first and second film-like portions 22b and 22c, and is substantially composed of only the composite portion 22a (an example of the “ionic conductor”). As described above, since the inorganic solid electrolyte body 26 does not include the first and second film-like portions 22b and 22c, the ohm loss at the interface between the cathode 12 and the electrolyte 17 and the interface between the anode 14 and the electrolyte 17 is reduced. Since it can be reduced, the power generation efficiency of the solid alkaline fuel cell 10 can be improved.

The structure of the composite portion 22a is as described in the first embodiment, and the closed pores 24 in contact with the porous base material 20 are formed inside. Therefore, it is possible to prevent the electrolyte 17 from peeling off or being deformed.

The inorganic solid electrolyte body 26 composed of only the composite portion 22a ends the treatment before the first and second film-like portions 22b and 22c are formed when the porous base material 20 is hydrothermally treated in the raw material aqueous solution. Just let me do it.

3. 3. Third Embodiment Hereinafter, the third embodiment of the solid alkaline fuel cell 10 will be described with reference to the drawings. The difference from the first embodiment is that the inorganic solid electrolyte 28 does not have the first and second film-like portions 22b and 22c (see FIG. 2), and the inorganic solid electrolyte 28 is the porous base material 20. It is in that it is placed only in a part of. Therefore, the differences will be mainly described below.

FIG. 4 is a schematic view showing an enlarged cross section of the electrolyte 18 according to the third embodiment. The electrolyte 18 has a porous base material 20 and an inorganic solid electrolyte body 28.

The configuration of the porous base material 20 is as described in the first embodiment, but since the porous base material 20 is in contact with each of the cathode 12 and the anode 14, the surface of the porous base material 20 is covered. Needs to form an insulating film. The insulating film can be composed of Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, Mg Al ₂ O _{4, and the} like.

The inorganic solid electrolyte body 28 (an example of “ionic conductor”) is arranged only in a part of the porous base material 20 in the thickness direction of the porous base material 20. In the present embodiment, as shown in FIG. 4, the inorganic solid electrolyte 28 is impregnated only in the region of the continuous pores 20a of the porous base material 20 on the anode 14 side. The cathode 12 is impregnated in the region of the continuous pores 20a of the porous base material 20 that is not impregnated with the inorganic solid electrolyte 28.

However, the inorganic solid electrolyte 28 may be impregnated only in the region on the cathode 12 side of the continuous pores 20a of the porous base material 20. In this case, the anode 14 may be impregnated in the region of the continuous pores 20a of the porous base material 20 that is not impregnated with the inorganic solid electrolyte body 28. Further, the inorganic solid electrolyte body 28 may be impregnated only in the central region in the thickness direction of the continuous pores 20a of the porous base material 20. In this case, the region of the continuous pores 20a of the porous base material 20 on the cathode 12 side of the inorganic solid electrolyte 28 is impregnated with the cathode 12, and the region of the inorganic solid electrolyte 28 on the anode 14 side is impregnated with the anode 14. Just do it.

The inorganic solid electrolyte body 28 is preferably arranged over the entire area of the porous base material 20 in the plane direction perpendicular to the thickness direction.

The inorganic solid electrolyte 28 has substantially the same configuration as the composite portion 22a described in the first embodiment. Therefore, it is possible to prevent the electrolyte 18 from peeling off or being deformed.

The inorganic solid electrolyte 28 arranged only in a part of the porous base material 20 may be obtained by immersing only a part of the porous base material 20 in the raw material aqueous solution when the porous base material 20 is hydrothermally treated.

(Modified example of embodiment)
Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the present invention.

[Modification 1]
In the above embodiment, an alkaline fuel cell having a hydroxide ion as a carrier has been described as an example of an electrochemical cell to which the electrolyte for an electrochemical cell according to the present invention is applied. However, the electrolyte for an electrochemical cell according to the present invention has been described. Is applicable to various electrochemical cells. The electrochemical cell can be applied to, for example, a fuel cell using a proton as a carrier, a secondary battery (nickel-zinc secondary battery, zinc-air secondary battery, etc.), an electrolytic cell that generates hydrogen and oxygen from steam, and the like. it can. When the electrochemical cell uses protons as carriers, the composite portion 22a, the first film-like portion 22b, and the second film-like portion 22c contain a proton-conducting ceramic component instead of the hydroxide ion conductive ceramic component. You just have to do it. The electrochemical cell is a device for converting chemical energy into electrical energy and a device for converting electrical energy into chemical energy, and is a pair of electrodes so that electromotive force is generated from the overall oxidation-reduction reaction. Is a general term for those in which.

[Modification 2]
In the first to third embodiments, the electrolytes 16, 17, and 18 have a plurality of closed pores 24, but if they have at least one closed pore 24, they have completely closed pores 24. Since the composite portion 22a can be provided with flexibility as compared with the case where the composite portion 22a is not provided, peeling of the electrolytes 16, 17, and 18 can be suppressed.

[Modification 3]
In the first embodiment, the inorganic solid electrolyte body 22 has a first film-like portion 22b and a second film-like portion 22c, but at least one of the first film-like portion 22b and the second film-like portion 22c You do not have to have one.

Similarly, in the second embodiment, the inorganic solid electrolyte body 26 is substantially composed of only the composite portion 22a, but even if one of the first and second film-like portions 22b and 22c is provided. Good.

Further, in the third embodiment, the inorganic solid electrolyte 28 is arranged only on a part of the porous base material 20, but when the inorganic solid electrolyte 28 is arranged on the cathode 12 side, the third embodiment is used. One film-shaped portion 22b may be provided, or a second film-shaped portion 22c may be provided when the inorganic solid electrolyte 28 is arranged on the anode 14 side.

[Modification example 4]
In the third embodiment, the cathode 12 is impregnated in the region of the continuous pores 20a of the porous base material 20 that is not impregnated with the inorganic solid electrolyte 28, but the cathode 12 is formed in the continuous pores 20a. It does not have to be filled, and may be formed in a film shape so as to cover the inner surface of the continuous hole 20a. Similarly, when the anode 14 is impregnated in a part of the continuous holes 20a of the porous base material 20, the anode 14 does not need to be filled in the continuous holes 20a and covers the inner surface of the continuous holes 20a. It may be formed in the form of a film.

[Modification 5]
In the above embodiment, all of the plurality of closed pores are separated from the porous base material 20, but some of the plurality of closed pores may be in contact with the porous base material 20.

10 Solid alkaline fuel cell 12 Cathode 14 Anode 16, 17, 18 Electrolyte 16S Cathode side surface 16T Anode side surface 20 Porous base material 20a Continuous holes 22, 26, 28 Inorganic solid electrolyte 22a Composite part 22b First film-like part 22c Second membrane-like part 24 Closed pores

Claims (6)

A porous substrate that has a three-dimensional network structure and forms continuous pores,
An ionic conductor having ionic conductivity and arranged in the continuous pores,
The closed pores formed in the ion conductor and
With
The porous substrate is composed of a metal material and is composed of a metal material.
The closed pores are in contact with the porous substrate.
Electrolyte for electrochemical cell. It is formed in the ion conductor and has a plurality of closed pores including the closed pores.
The electrolyte for an electrochemical cell according to claim 1. The porous substrate has pores inside and
The pores are impregnated with the ionic conductor.
The electrolyte for an electrochemical cell according to claim 1 or 2. An insulating film is formed on at least one main surface of the porous base material or on the surface of the porous base material including the inner surface of the continuous pores .
The electrolyte for an electrochemical cell according to any one of claims 1 to 3. Porous base material that forms continuous pores and
An ionic conductor having ionic conductivity and arranged in the continuous pores,
The closed pores formed in the ion conductor and
With
The porous substrate is composed of a metal material and is composed of a metal material.
The closed pores are in contact with the porous substrate.
Electrolyte for electrochemical cell. The cathode to which the oxidant is supplied and
The anode to which the fuel is supplied and
The electrolyte for an electrochemical cell according to any one of claims 1 to 5, which is arranged between the cathode and the anode.
An electrochemical cell equipped with.

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