JP2019220461A - Electrolyte for electrochemical cell, and electrochemical cell - Google Patents

Abstract

To provide an electrolyte for an electrochemical cell, capable of improving ionic conductivity.SOLUTION: An electrolyte 16 for an electrochemical cell includes a porous base material 20 and a composite part 22a. The porous base material 20 has a first main surface S, a second main surface 20T, and a lateral face 20U. The composite part 22a is filled in the porous base material 20. The composite part 22a covers a lateral face 20U of the porous base material 20. The composite part 22a has ionic conductivity.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art Conventionally, in electrochemical cells such as an alkaline fuel cell, an alkaline secondary battery, and an electrolytic cell, an ion conductor having ionic conductivity is used as an electrolyte (for example, see Patent Document 1).

JP-A-2006-071948

  By improving the ionic conductivity of the electrolyte for an electrochemical cell as described above, the power generation efficiency of the electrochemical cell can be improved. Therefore, there is a demand for improving the ionic conductivity of the electrolyte for an electrochemical cell. Therefore, an object of the present invention is to provide an electrolyte for an electrochemical cell capable of improving ionic conductivity.

  An electrolyte for an electrochemical cell according to a first aspect of the present invention includes a porous substrate and an ionic conductor. The porous substrate has a first main surface, a second main surface, and side surfaces. The ion conductor is filled in the porous substrate. The ion conductor covers the side surface of the porous substrate. The ion conductor has ion conductivity.

  According to this configuration, since the ion conductor covers the side surface of the porous substrate, the ion conductivity can be improved.

  Preferably, the side surface of the electrolyte for an electrochemical cell is constituted by an ionic conductor.

  Preferably, the thickness of the ion conductor covering the side surface of the porous substrate is 0.1 to 30 μm.

  Preferably, the electrolyte for an electrochemical cell further includes a first film-like portion. The first film portion has ion conductivity. The first film portion covers the first main surface of the porous substrate.

  Preferably, the electrolyte for an electrochemical cell further includes a second film-shaped portion. The second film portion has ion conductivity. The second film portion covers the second main surface of the porous substrate.

  Preferably, the thickness of the ion conductor covering the side surface of the porous substrate is smaller than the thickness of the first film-shaped portion.

  Preferably, the average particle diameter of the particles constituting the ion conductor covering the side surface of the porous substrate is smaller than the average particle diameter of the particles constituting the first film-like portion. According to this configuration, peeling of the ionic conductor covering the side surface of the porous substrate can be suppressed.

  Preferably, the porous substrate is composed of at least one selected from a ceramic material and a polymer material.

  Preferably, the porous substrate has a three-dimensional network structure. Also, the porous structure has continuous pores. Then, the ion conductor is disposed in the continuous hole. Further, the ion conductor has closed pores inside. According to this configuration, separation of the electrolyte for an electrochemical cell can be suppressed.

  Preferably, the closed pores are remote from the porous substrate.

  Preferably, the closed pore is in contact with the porous substrate.

  Preferably, the ion conductor has a plurality of closed pores including closed pores.

  Preferably, the porous substrate has pores inside. These pores are impregnated with an ion conductor.

  Preferably, the electrolyte for an electrochemical cell further includes an annular protrusion. The protruding portion is disposed on an outer peripheral portion of the main surface of the electrolyte for an electrochemical cell and protrudes from the main surface.

  An electrochemical cell according to a second aspect of the present invention includes a cathode, an anode, and any one of the above electrolytes for an electrochemical cell. The cathode is supplied with an oxidant. The anode is supplied with fuel. The electrolyte for the electrochemical cell is disposed between the cathode and the anode.

  According to the present invention, ionic conductivity can be improved.

FIG. 1 is a cross-sectional view schematically illustrating a configuration of a solid alkaline fuel cell. The elements on larger scale of FIG. The figure corresponding to FIG. 2 of the electrolyte which concerns on a modification. The figure corresponding to FIG. 2 of the electrolyte which concerns on a modification. The figure corresponding to FIG. 2 of the electrolyte which concerns on a modification.

  Hereinafter, as an example of an electrochemical cell to which the electrolyte for an electrochemical cell according to the present invention is applied, an embodiment of a solid alkaline fuel cell 10 which is a kind of an alkaline fuel cell (AFC) using hydroxide ions as a carrier. This will be described with reference to the drawings.

(Solid alkaline fuel cell 10)
FIG. 1 is a cross-sectional view illustrating a configuration of a 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 an electrolyte for an electrochemical cell). The solid alkaline fuel cell 10 generates power 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, methanol is used as an example of the fuel.

・ 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

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

The cathode 12 is not particularly limited as long as it includes a known air electrode catalyst used for AFC. Examples of the cathode catalyst include a group 8-10 element such as a platinum group element (Ru, Rh, Pd, Os, Ir, Pt) and an iron group element (Fe, Co, Ni) in the periodic table in IUPAC format. Group 11 elements such as Cu, Ag, and Au (elements belonging to Group 11 in the periodic table in 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 carried on the cathode 12 is not particularly limited, but is preferably 0.1 to 10 mg / cm ² , more preferably 0.1 to 5 mg / cm ² . The cathode catalyst is preferably supported on carbon. Preferable examples of the cathode 12 or a catalyst constituting the cathode 12 include platinum-supported carbon (Pt / C), palladium-supported carbon (Pd / C), rhodium-supported carbon (Rh / C), nickel-supported carbon (Ni / C), Copper on carbon (Cu / C) and silver on carbon (Ag / C).

  The method for producing the cathode 12 is not particularly limited. For example, the cathode 12 is formed by mixing a cathode catalyst and a carrier as desired with a binder to form a paste, and applying the paste mixture to the cathode-side main surface 16S of the electrolyte 16. Can be.

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

  The anode 14 is a cathode generally called a fuel electrode. During the power generation of the solid alkaline fuel cell 10, the fuel containing hydrogen atoms (H) is supplied to the anode 14 via the fuel supply means 15.

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

Examples of the fuel compound include (i) hydrazine (NH ₂ NH ₂ ), hydrazine hydrate (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} ), hydrazine, such as monomethyl hydrazine _(CH 3 NHNH _2), dimethylhydrazine _{((CH 3) 2 NNH 2} , CH 3 NHNHCH 3), and a carboxylic hydrazide ((NHNH _{2) 2} CO) (Ii) Heterocycle such as urea (NH ₂ CONH ₂ ), (iii) ammonia (NH ₃ ), (iv) imidazole, 1,3,5-triazine, 3-amino-1,2,4-triazole class compounds, (v) hydroxylamine _(NH 2 OH), hydro such as sulfuric hydroxylamine _{(NH 2 OH · H 2 SO} 4) Shiruamin acids, and combinations thereof. Among these fuel compounds, compounds containing no carbon (that is, hydrazine, hydrazine hydrate, 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 it is as a fuel, or may be used as a solution dissolved in water and / or an alcohol (eg, 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 liquid fuels as they are. Also, hydrazine carbonate, hydrazine sulfate, carboxylic hydrazide, urea, imidazole, 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 soluble in water. As described above, the solid fuel compound can be used as a liquid fuel by dissolving it in water or alcohol. When the fuel compound is used by dissolving it in water and / or alcohol, the concentration of the fuel compound in the solution is, for example, 1 to 90% by weight, and preferably 1 to 30% by weight.

  In addition, hydrocarbon-based liquid fuels containing alcohols and ethers such as methanol and ethanol, hydrocarbon-based gases such as methane, and pure hydrogen can be used as fuels as they are. In particular, methanol is suitable as the fuel used for the solid alkaline fuel cell 10 according to the present embodiment. Methanol may be in any of a gas state, a liquid state, and a gas-liquid mixed state.

  The anode 14 is not particularly limited as long as it includes 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. However, the metal catalyst may be in the form of an organometallic complex having a metal atom as a central metal, or the organometallic 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 a catalyst constituting the anode 14 include nickel, cobalt, silver, platinum-supported carbon (Pt / C), palladium-supported carbon (Pd / C), rhodium-supported carbon (Rh / C), and nickel-supported carbon. (Ni / C), copper supported carbon (Cu / C), and silver supported carbon (Ag / C).

  The method of producing the anode 14 is not particularly limited. For example, the anode 14 is formed by mixing an anode catalyst and a carrier as desired with a binder to form a paste, and applying the paste mixture to the anode-side main surface 16T of the electrolyte 16. Can be.

(Electrolyte 16)
The electrolyte 16 is disposed 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 a film shape having a main surface and side surfaces. The cathode 12 is disposed on the cathode-side main surface 16S of the electrolyte 16, and the anode 14 is disposed on the anode-side main surface 16T.

  FIG. 2 is a schematic diagram showing an enlarged cross section of the electrolyte 16. The electrolyte 16 has a porous substrate 20 and an inorganic solid electrolyte body 22.

  The porous substrate 20 has a three-dimensional network structure. The “three-dimensional network structure” is a structure in which constituent materials of a base material are connected three-dimensionally and in a network. The porous substrate 20 forms continuous holes 20a. The continuous holes 20 a are formed by connecting the holes three-dimensionally and in a mesh form, and are exposed on the outer surface of the porous substrate 20. The continuous holes 20a are impregnated with the inorganic solid electrolyte body 22.

  The porous substrate 20 can be composed of at least one selected from a ceramic material and a polymer material. Ceramic materials include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof. Examples of the polymer material include polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrofluorinated fluororesin (tetrafluorinated resin: PTFE, etc.), cellulose, nylon, polyethylene and any combination thereof. . When the porous substrate 20 is made of a flexible polymer material, the thickness is easily reduced while increasing the porosity, so that the hydroxide ion conductivity can be improved. As the porous substrate 20 composed of a polymer material, a microporous membrane commercially available as a lithium battery separator can be used.

  The porous substrate 20 is in the form of a film. The porous substrate 20 has a first main surface 20S, a second main surface 20T, and a side surface 20U. The thickness of the porous substrate 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, still more preferably 50 μm or less, particularly preferably 25 μm or less, and 5 μm or less. The following are most preferred. The lower limit of the thickness of the porous substrate 20 may be appropriately set according to the application, but is preferably 1 μm or more, more preferably 2 μm or more, to secure a certain degree of rigidity.

  The average inner diameter of the continuous holes 20a in the cross section of the porous substrate 20 is not particularly limited, but may be, for example, 0.001 to 1.5 μm, preferably 0.001 to 1.25 μm, and more preferably 0. It is 001 to 1.0 μm, more preferably 0.001 to 0.75 μm, and particularly preferably 0.001 to 0.5 μm. When the content is within these ranges, the density of the inorganic solid electrolyte body 22 can be improved while imparting strength to the porous substrate 20 as a support. 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 locations randomly selected on the observation image when the cross section of the porous substrate 20 is observed with an electron microscope. can get. The equivalent circle 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. Note that the magnification of the electron microscope may be appropriately set according to the cross-sectional size of the continuous hole 20a.

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

  Although not shown in FIG. 2, the porous substrate 20 preferably has a plurality of pores inside itself. The plurality of pores may be connected to each other inside the porous substrate 20. Each of the pores is an open pore that opens on the surface of the porous substrate 20, and it is more preferable that each of the pores is impregnated with the inorganic solid electrolyte body 22. Thereby, a short-distance ion conduction path of continuous pores 20a → pores in porous substrate 20 → continuous pores 20a, or continuous pores 20a → pores in porous substrate 20 → second film-like portion 22c, or A long-distance ion conduction path of the first film-like portion 22b → pores in the porous substrate 20 → the second film-like portion 22c can be formed. As a result, the ion-conducting area in the composite portion 22a is expanded, so that the ion conductivity of the electrolyte 16 as a whole can be improved.

The inorganic solid electrolyte member 22 has hydroxide ion conductivity. During the power generation of the solid alkaline fuel cell 10, the inorganic solid electrolyte body 22 conducts hydroxide ions (OH ⁻ ) from the cathode 12 side to the anode 14 side. The hydroxide ion conductivity of the inorganic solid electrolyte body 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 hydroxide ion conductivity of the inorganic solid electrolyte body 22 is preferably as high as possible, 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, a layered double hydroxide (LDH: Layered Double Hydroxide) is preferable.

LDH ^is, 2 O (wherein _{^{M 2+ 1-x M 3+ x}} (OH) 2 A n- x / n · mH, M 2+ is a divalent ^{cation, M 3+} is a trivalent cation, A ^n- is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is any 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⁺ . Examples of M ³⁺ include Al ³⁺ , Fe ³⁺ , Ti ³⁺ , ^{Y 3+, Ce 3+, Mo 3+} , and ^{Cr 3+, and} examples of ^{a n-} is _CO ^{3 2-} and OH ^- are exemplified. Each of M ²⁺ and M ³⁺ may be used alone or in combination of two or more.

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

Ni in the LDH can take the form of nickel ions. The nickel ions in the LDH are typically considered to be Ni ²⁺ , but are not particularly limited since there may be other valences such as Ni ³⁺ . Al in the LDH can take the form of aluminum ions. The aluminum ion in the LDH is typically considered to be Al ³⁺ , but is not particularly limited because there may be other valences. Ti in LDH can take the form of titanium ions. The titanium ion in the LDH is typically considered to be Ti ⁴⁺ , but is not particularly limited because there may be other valences such as Ti ³⁺ . The hydroxide basic layer preferably contains Ni, Al, Ti and OH groups as main constituents, but may contain other elements or ions or may contain unavoidable impurities. The unavoidable impurities are optional elements that can be unavoidably mixed in the manufacturing method, and can be mixed into the LDH from, for example, 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 valent anion, preferably a monovalent or divalent ion. Preferably, anions in the LDH is OH ^- containing and / or _CO ^{3 2-} and.

As described above, since the valences of Ni, Al, and Ti are not always known, it is impractical or impossible to strictly specify LDH by a general formula. Assuming that the hydroxide basic layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ and OH groups, the LDH is represented 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 Is 0.01 ≦ x ≦ 0.5, 0 <y <1, preferably 0.01 ≦ y ≦ 0.5, 0 <x + y <1, and m is 0 or more, typically more than 0 or 1 or more Is a real number). However, the above general formula should be interpreted as a “basic composition” to the last, and other elements or ions (of the same element) to the extent that elements such as Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ do not impair the basic properties of LDH. (Including elements or ions of other valences or elements or ions which can be inevitably mixed in the production process).

  The inorganic solid electrolyte body 22 has a composite portion 22a (an example of an ion conductor), a first film-like portion 22b, and a second film-like portion 22c.

  The composite part 22a is disposed between the first film-like part 22b and the second film-like part 22c. The composite portion 22a is filled in the porous substrate 20. Specifically, the composite portion 22a is arranged in a plurality of holes of the porous substrate 20. The composite portion 22a is impregnated in the continuous holes 20a of the porous substrate 20, and is integrated with the porous substrate 20. Since the inorganic solid electrolyte body 22 is supported by the porous substrate 20 as described above, the strength of the inorganic solid electrolyte body 22 can be improved, so that the inorganic solid electrolyte body 22 can be made thin. As a result, the resistance of the electrolyte 16 can be reduced.

  Further, the composite portion 22a covers the side surface 20U of the porous substrate 20. That is, the side surface 20U of the porous substrate 20 is not exposed on the side surface of the electrolyte 16. For this reason, the side surface of the electrolyte 16 is constituted only by the oriented solid electrolyte member 22 including the composite portion 22a.

  The thickness t3 of the composite portion 22a that covers the side surface 20U of the porous substrate 20 can be, for example, about 0.1 to 30 μm. The thickness t3 of the composite portion 22a can be an average value of thicknesses measured at three points at intervals in the thickness direction in a cross section of an arbitrary portion.

  In the present embodiment, the composite portion 22a extends over substantially the entire area of the continuous hole 20a of the porous substrate 20. However, when the inorganic solid electrolyte body 22 does not have at least one of the first film-like portion 22b and the second film-like portion 22c, the composite portion 22a may be impregnated only in a part of the porous substrate 20. Good.

  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, a change in volume of the electrolyte 16 due to a change in the water content of the composite portion 22a during operation of the solid alkaline fuel cell 10 can be reduced. . Thereby, generation of stress at the interface between the electrolyte 16 and the cathode 12 and / or the interface between the electrolyte 16 and the anode 14 can be suppressed. As a result, separation of the electrolyte 16 from the cathode 12 and / or the anode 14 and deformation of the electrolyte 16 itself can be suppressed.

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

  As shown in FIG. 2, the closed pores 24 are separated from the porous substrate 20. That is, the closed pores 24 are confined inside the composite portion 22a and do not directly contact the inner surface of the continuous holes 20a. Accordingly, when the volume change or deformation occurs in the electrolyte 16 as compared with the case where the closed pores 24 are in direct contact with the porous base material 20, the three components of the porous base material 20, the composite portion 22a and the closed pores 24 are used. Starting from the corner formed by the above, it is possible to suppress the separation of the composite portion 22a from the porous substrate 20.

  The average equivalent circle diameter of each closed pore 24 is not particularly limited, but may be, for example, 0.001 to 1.0 μm. The average equivalent circle diameter of each closed pore 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 equivalent circle diameter of each closed pore 24 is preferably 1.0 μm or less, more preferably 0.8 μm or less. Thus, it is possible to prevent the oxidant 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.

  The average equivalent circle diameter of each closed pore 24 is obtained by observing the cross section of the electrolyte 16 with an electron microscope at a magnification of 20,000 to 1,500,000 and arithmetically calculating the equivalent circle diameter of 20 randomly selected closed pores 24. Obtained by averaging. The equivalent circle diameter of the closed pores 24 is the diameter of a circle having the same area as the closed pores 24 in the cross section of the electrolyte 16. However, since the closed pores 24 having a circle equivalent diameter of 0.001 μm or less contribute very little to the improvement of the flexibility of the composite portion 22a, they should be excluded when calculating the average circle equivalent diameter of each closed pore 24. I do.

  The first film-shaped portion 22b is disposed on the first main surface 20S of the porous substrate 20, and covers the first main surface 20S of the porous substrate 20. The first film-shaped portion 22b continues to the cathode 12 side of the composite portion 22a. The first film-like portion 22b is formed in a film shape. The first film-like portion 22b is formed integrally with the composite portion 22a.

  The second film-like portion 22c is disposed on the second main surface 20T of the porous substrate 20, and covers the second main surface 20T of the porous substrate 20. The second film-shaped portion 22c continues to the anode 14 side of the composite portion 22a. The second film-like portion 22c is formed in a film shape. The second film-like portion 22c is formed integrally with the composite portion 22a.

  Each of the first film-like portion 22b and the second film-like portion 22c can be made of a ceramic material having hydroxide ion conductivity. Each of the first film-like portion 22b and the second film-like portion 22c may be formed in a uniform planar shape, or may be patterned into a desired planar shape such as a stripe shape. The thicknesses t1 and t2 of each of the first film-like portion 22b and the second film-like portion 22c are not particularly limited, but can be, for example, 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less.

  Note that the thickness t1 of the first film-shaped portion 22b is the same as the thickness of the composite portion 22a measured at three points at intervals in the in-plane direction (x-axis direction) on the same cross-section as the cross-section measured. It can be an average value. The thickness t2 of the second film-like portion 22c can be measured in the same manner as the thickness t1 of the first film-like portion 22b.

(Method of Manufacturing Inorganic Solid Electrolyte Body 22)
The method for producing the inorganic solid electrolyte body 22 is not particularly limited. However, when the inorganic solid electrolyte body 22 is made of LDH and the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups, In the steps (1) to (4).

  (1) A porous substrate 20 is prepared.

  (2) The entire porous substrate 20 is impregnated with a mixed sol of alumina and titania and heat-treated to form an alumina-titania layer. As described later, in order to grow LDH from the entire surface of the porous substrate 20, it is important to form an alumina-titania layer on the entire surface of the porous substrate 20, and therefore a mixed sol of alumina and titania is required. And heat-treating a plurality of times. Thereby, an alumina / titania layer can be formed on the entire surface of the porous substrate 20.

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

  (4) By performing a hydrothermal treatment on the porous substrate 20 in the raw material aqueous solution to form LDH on the porous substrate 20 and in the porous substrate 20, the composite portion 22a, the first film portion 22b, Then, the inorganic solid electrolyte member 22 having the second film-shaped portion 22c is formed. At this time, by appropriately adjusting the hydrothermal treatment time and the solution concentration, the reaction is stopped before the pores are closed, so that the closed pores 24 can be formed in the composite portion 22a. Since the LDH grows with the alumina / titania layer formed on the surface of the porous substrate 20 as a nucleus, when the alumina / titania layer is formed on the entire surface of the porous substrate 20, the porous substrate 20 LDH grows from the entire surface of the substrate. As a result, the closed pores 24 can be separated from the porous substrate 20.

(Modification of Embodiment)
The embodiments of the present invention have been described above. However, the present invention is not limited to these, and various modifications can be made without departing from the spirit of the present invention.

Modification 1
In the above-described embodiment, the closed pores 24 are separated from the porous substrate 20. However, as shown in FIG. 3, the closed pores 24 may be in contact with the porous substrate 20. That is, the closed pore 24 may be in direct contact with the inner surface of the continuous hole 20a. As a result, the restrained area of the porous substrate 20 due to the presence of the closed pores 24 can be reduced as compared with the case where the closed pores 24 are apart from the porous substrate 20. Can be improved. Therefore, when a change in volume or deformation occurs in the electrolyte 16, it is possible to further suppress the occurrence of stress at the interface between the cathode 12 and the electrolyte 16 and / or at the interface between the anode 14 and the electrolyte 16.

Modification 2
In the above embodiment, the electrolyte 16 has a plurality of closed pores 24. However, if the electrolyte 16 has at least one closed pore 24, compared to a case where it has no closed pore 24, the composite portion Since flexibility can be imparted to 22a, peeling of electrolyte 16 can be suppressed.

Modification 3
In the above embodiment, the shape of the closed pores 24 is circular in cross section, but the shape of the closed pores 24 is not limited to this. For example, the closed pores 24 may have an elliptical cross section or other shapes.

Modification 4
In the above embodiment, the porous substrate 20 is made of at least one selected from a ceramic material and a polymer material, but the material of the porous substrate 20 is not limited to this. For example, the porous substrate 20 can also be formed of a metal material. As a metal material constituting the porous substrate 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, the heat dissipation efficiency of the porous substrate 20 can be improved, and the temperature distribution in the porous substrate 20 is reduced. Can be done.

  The porous substrate 20 may be, for example, a cellular or monolithic structure made of a porous metal material (for example, a foamed metal material), or a mesh-like lump made of a fine-wire metal material. It may be.

  Further, the porous substrate 20 may not have a three-dimensional network structure. Examples of the porous base material 20 having no three-dimensional network structure include a mesh member formed by weaving a plurality of wires made of a metal material, a metal thin plate having a plurality of fine straight holes, and the like. Is 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 tatami weave, twill tatami weave, or other weave. When a mesh member is used as the porous substrate 20, gaps (ie, openings) between the respective wires become continuous holes 20a. The straight holes in the metal sheet can be formed, for example, by laser processing. When a thin metal plate is used as the porous substrate 20, the straight holes become continuous holes 20a.

An insulating film may be formed on the surface of the porous substrate 20 (including the inner surface of the continuous hole 20a). The insulating film can be made of Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, MgAl ₂ O ₄ or the like. When the porous substrate 20 is made of stainless steel, a Cr ₂ O ₃ film as an insulating film can be easily formed by oxidizing the stainless steel. Since the first and second film portions 22b and 22c function as an insulating film between the cathode 12 and the anode 14, even if the insulating film is not formed on the surface of the porous substrate 20, Good.

Modification 5
In the above embodiment, the inorganic solid electrolyte body 22 has the composite portion 22a, the first film-shaped portion 22b, and the second film-shaped portion 22c. However, it is sufficient that the inorganic solid electrolyte body 22 has at least the composite portion 22a. That is, the inorganic solid electrolyte body 22 may not include at least one of the first film-like portion 22b and the second film-like portion 22c.

  When the inorganic solid electrolyte body 22 does not include the first film-shaped portion 22b, the composite portion 22a may be impregnated into the entire continuous pores 20a of the porous base material 20, or may be continuous with the porous base material 20. Only the region on the cathode 12 side of the hole 20a may be impregnated. When the composite portion 22a is impregnated only in the region of the continuous hole 20a of the porous substrate 20 on the cathode 12 side, at least a part of the anode 14 may be disposed in the void region of the continuous hole 20a. The anode 14 arranged in the void region of the continuous hole 20a may be filled in the continuous hole 20a, or may be formed in a film shape so as to cover the inner surface of the continuous hole 20a.

  When the inorganic solid electrolyte body 22 does not include the second film-like portion 22c, the composite portion 22a may be impregnated into the entire continuous pores 20a of the porous base material 20, or may be continuous with the porous base material 20. Only the region on the anode 14 side of the hole 20a may be impregnated. When the composite portion 22a is impregnated only in the region on the anode 14 side of the continuous holes 20a of the porous substrate 20, at least a part of the cathode 12 may be disposed in the void region of the continuous holes 20a. The cathode 12 arranged in the void region of the continuous hole 20a may be filled in the continuous hole 20a, or may be formed in a film shape so as to cover the inner surface of the continuous hole 20a.

Modification 6
As shown in FIG. 4, the thickness t3 of the composite portion 22a that covers the side surface 20U of the porous substrate 20 can be smaller than the thickness t1 of the first film-like portion 22b. Further, the thickness t3 of the composite portion 22a that covers the side surface 20U of the porous substrate 20 can be smaller than the thickness t2 of the second film-like portion 22c. Although not particularly limited, for example, the thickness t3 of the composite portion 22a can be about 5 to 50% of the thickness t1 of the first film-like portion 22b.

Modification 7
The first average particle size of the particles constituting the composite portion 22a covering the side surface 20U of the porous substrate 20 is smaller than the second average particle size of the particles constituting the first film-like portion 22b. For example, the first average particle size can be about 5 to 50% of the second average particle size. The average particle diameter of the particles constituting the composite portion 22a covering the side surface 20U of the porous substrate 20 is smaller than the average particle diameter of the particles constituting the second film-like portion 22c. In addition, each average particle diameter can be calculated | required from the cross-sectional image by an electron microscope (scanning electron microscope (SEM) or transmission electron microscope (TEM)). Specifically, the first average particle diameter is a value obtained by arithmetically averaging the diameters of circles having the same area as each of 50 randomly selected particles in the cross-sectional image of the composite portion 22a. Similarly, the second average particle diameter is a value obtained by arithmetically averaging the diameters of circles having the same area as each of 50 randomly selected particles in a cross-sectional image of the first film-shaped portion 22b. The first average particles are measured at the center in the in-plane direction (xy-plane direction) and the thickness direction (z-axis direction) in the composite portion 22a that covers the side surface 20U of the porous substrate 20. The second average particles are measured in the first film-like portion 22c at the center in the in-plane direction (xy-plane direction) and the thickness direction (z-axis direction).

Modification 8
As shown in FIG. 5, the electrolyte 16 may have first and second protrusions 25a and 25b. The first and second protrusions 25a, 25b are annular. The first protrusion 25a is arranged on the outer peripheral edge of the cathode-side main surface 16S. The first protrusion 25a protrudes from the cathode-side main surface 16S. The first protruding portion 25a is arranged so as to surround the cathode 12.

  The second protrusion 25b is arranged on the outer peripheral edge of the anode-side main surface 16T. The second protrusion 25b protrudes from the anode-side main surface 16T. The second protrusion 25b is disposed so as to surround the anode 14.

Modification 9
In the above embodiment, the cathode 12 is formed on the first film-like portion 22b and the anode 14 is formed on the second film-like portion 22c, but the invention is not limited to this. For example, the anode 14 may be formed on the first film portion 22b, and the cathode 12 may be formed on the second film portion 22c.

Modification 10
In the above embodiment, the alkaline fuel cell using hydroxide ions as a carrier has been described as an example of the electrochemical cell to which the electrochemical cell electrolyte according to the present invention is applied, but the electrochemical cell electrolyte according to the present invention is described. Is applicable to various electrochemical cells. Examples of electrochemical cells include fuel cells using protons as carriers, secondary batteries (nickel zinc secondary batteries, zinc air secondary batteries, etc.), and electrolytic cells (SOEC) that generate hydrogen and oxygen from water vapor. can do. When the electrochemical cell uses protons as carriers, the composite portion 22a, the first film portion 22b, and the second film portion 22c contain a proton conductive ceramic component instead of the hydroxide ion conductive ceramic component. Just do it. An electrochemical cell is a device for converting chemical energy into electrical energy and a device for converting electrical energy into chemical energy. A pair of electrodes is used to generate an electromotive force from the overall oxidation-reduction reaction. Is a generic term for the arrangement.

Reference Signs List 10 solid alkaline fuel cell 12 cathode 14 anode 16 functional layer 20 porous substrate 20S first main surface 20T second main surface 20U side surface 22 inorganic solid electrolyte body 22a composite part

Claims (15)

A first main surface, a second main surface, and a porous substrate having side surfaces;
An ion conductor filled with the porous substrate and covering the side surface of the porous substrate, and having ion conductivity,
An electrolyte for an electrochemical cell, comprising:
The side surface of the electrolyte for an electrochemical cell is constituted by the ion conductor,
The electrolyte for an electrochemical cell according to claim 1.
The thickness of the ion conductor covering the side surface of the porous substrate is 0.1 to 30 μm,
The electrolyte for an electrochemical cell according to claim 1.
A first film-shaped portion covering the first main surface of the porous base material and having ion conductivity;
The electrolyte for an electrochemical cell according to any one of claims 1 to 3, further comprising:
A second film-shaped portion covering the second main surface of the porous substrate and having ion conductivity;
The electrolyte for an electrochemical cell according to claim 4, further comprising:
The thickness of the ionic conductor covering the side surface of the porous substrate is smaller than the thickness of the first film-shaped portion,
The electrolyte for an electrochemical cell according to claim 4.
The average particle diameter of the particles constituting the ion conductor covering the side surface of the porous substrate is smaller than the average particle diameter of the particles constituting the first film-like portion,
An electrolyte for an electrochemical cell according to any one of claims 4 to 6.
The porous substrate is constituted by at least one selected from a ceramic material and a polymer material,
An electrolyte for an electrochemical cell according to claim 1.
The porous substrate has a three-dimensional network structure and forms continuous pores,
The ionic conductor is disposed in the continuous hole,
The ionic conductor has a closed pore inside,
An electrolyte for an electrochemical cell according to any one of claims 1 to 8.
The closed pores are separated from the porous substrate,
An electrolyte for an electrochemical cell according to claim 9.
The closed pores are in contact with the porous substrate,
An electrolyte for an electrochemical cell according to claim 9.
The ion conductor has a plurality of closed pores including the closed pores,
An electrolyte for an electrochemical cell according to any one of claims 9 to 11.
The porous substrate has pores inside,
The pores are impregnated with the ion conductor,
An electrolyte for an electrochemical cell according to claim 1.
It is arranged on the outer peripheral edge of the main surface of the electrochemical cell electrolyte, and further comprises an annular protrusion protruding from the main surface,
An electrolyte for an electrochemical cell according to any one of claims 1 to 13.
A cathode to which an oxidant is supplied;
An anode to which fuel is supplied;
An electrolyte for an electrochemical cell according to any one of claims 1 to 14, which is disposed between the cathode and the anode;
An electrochemical cell comprising:

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