JP6670968B2 - Electrolyte for electrochemical cell and electrochemical cell - Google Patents

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

  However, when it is difficult to completely densify the electrolyte, the electromotive force may decrease due to the permeation of the oxidant from the cathode to the anode and the permeation of the fuel from the anode to the cathode.

  An object of the present invention is to provide an electrolyte for an electrochemical cell and an electrochemical cell capable of suppressing permeation of an oxidizing agent and a fuel.

  The electrolyte for an electrochemical cell according to the present invention includes a porous substrate, an ion conductor, and a metal component. The porous substrate has a three-dimensional network structure and forms continuous pores. The ion conductor has ion conductivity and is arranged in the continuous pore. The metal component is disposed in a gap between the porous substrate and the ion conductor.

  ADVANTAGE OF THE INVENTION According to this invention, the electrolyte for electrochemical cells which can suppress permeation of an oxidizing agent and a fuel, and an electrochemical cell can be provided.

Sectional view schematically showing the configuration of a solid alkaline fuel cell Partial enlarged view of FIG.

(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, a solid alkaline fuel cell 10 which is an example of an alkaline fuel cell (AFC) using hydroxide ions as a carrier will be described. This will be described with reference to the drawings.

  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. 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

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 Group 8 to Group 10 elements such as platinum group elements (Ru, Rh, Pd, Ir, Pt) and iron group elements (Fe, Co, Ni). 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 0.05 to 10 mg / cm ² , and more preferably 0.05 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), 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. For example, the cathode 12 can be formed by mixing a cathode catalyst and, if desired, a carrier with a binder to form a paste, and applying the paste mixture 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, 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 fuel containing hydrogen atoms only needs to contain a fuel compound capable of reacting with hydroxide ions (OH ⁻ ) at the anode 14 and may be in any form of a liquid fuel or a gaseous fuel.

Examples of fuel compounds 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 ), 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) s, (ii) urea _{(NH 2 CONH 2), (} iii) ammonia _(NH 3), _(iv) an imidazole, 1,3,5-triazine, 3-amino-1,2,4-heterocycle 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 a fuel as it is, 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 a liquid fuel as they are. In addition, hydrazine carbonate, hydrazine sulfate, carboxyhydrazide, 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, 30 to 99.9% by weight, and preferably 66 to 99.9% 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, but may be in the form of an organometallic complex having the metal atom of the metal catalyst as a central metal, or the organometallic complex may be supported as a carrier. In addition, 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), platinum-ruthenium-supported carbon (PtRu / 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 anode 14 is not particularly limited. For example, the anode 14 may be formed by mixing an anode catalyst and, if desired, a carrier with a binder to form a paste, and applying the paste mixture to the anode-side surface 16T of the electrolyte 16. it can.

  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, a layer shape, or a sheet shape.

  FIG. 2 is a schematic diagram showing an enlarged cross section of the electrolyte 16. The electrolyte 16 has a porous substrate 20, an inorganic solid electrolyte body 22, and a plurality of metal components 24.

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

  The porous substrate 20 may have 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. However, the porous substrate 20 may not have a three-dimensional network structure.

  The porous substrate 20 can be composed of at least one selected from a metal material, a ceramic material, and a polymer 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 radiation efficiency of the porous substrate 20 can be improved, and the temperature distribution in the porous substrate 20 is reduced. Can be done.

  As the porous substrate 20 having a three-dimensional network structure, for example, a cell-like or monolith-like structure made of a porous metal material (for example, a foamed metal material), or a mesh-like structure made of a fine-wire metal material Lumps and metal non-woven fabrics are exemplified.

  As the porous base material 20 having no three-dimensional network structure, in addition to a mesh member formed by weaving a plurality of wires made of a metal material, a metal thin plate formed with a plurality of fine straight holes is used. No. 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 base material 20, the gaps (ie, openings) between the respective wires become the continuous holes 20a. The straight holes in the metal sheet 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.

When the porous substrate 20 is made of a metal material, 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 may be a passivation film formed by passivation processing of a base metal, or may be an oxide such as Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, MgAl ₂ O ₄ . It may be a configured oxide film. 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. However, in the present embodiment, the first and second film portions 22b and 22c described later function as insulating films between the cathode 12 and the anode 14, respectively. The film may not be formed.

  Examples of the ceramic material constituting the porous substrate 20 include alumina, zirconia, titania, magnesia, calcia, cordierite, zeolite, mullite, zinc oxide, silicon carbide, and any combination thereof.

  Examples of the polymer material constituting the porous substrate 20 include polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE, etc.), cellulose, nylon, polyethylene, polyimide, and the like. Any combination of When the porous base material 20 is made of a flexible polymer material, the thickness of the continuous holes 20a can be easily reduced while increasing the volume, so that the hydroxide ion conductivity can be improved. As the porous substrate 20 composed of a polymer material, a microporous film commercially available as a separator for a lithium battery can be used.

  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, and most preferably 50 μm or less. The lower limit of the thickness of the porous substrate 20 may be appropriately set according to the application, but is preferably 10 μm or more, and more preferably 15 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. When the porous substrate 20 is made of a metal material, the average inner diameter of the continuous holes 20a can be 1 to 1000 μm, preferably 2 to 500 μm, more preferably 5 to 400 μm, and still more preferably 7 to 300 μm. And particularly preferably 10 to 200 μm. When the porous substrate 20 is made of a ceramic material or a polymer material, the average inner diameter of the continuous holes 20a can be, for example, 0.001 to 1.5 μm, and preferably 0.001 to 1.5 μm. .25 μm, more preferably 0.001 to 1.0 μm, still 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 observed image when the cross section of the porous substrate 20 is observed with an electron microscope. Can be 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 an 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 pore is an open pore that opens on the surface of the porous substrate 20, and it is more preferable that each pore is impregnated with the inorganic solid electrolyte body 22. Thereby, a short distance ion conduction path of continuous pore 20a → pore in porous substrate 20 → continuous pore 20a, or continuous pore 20a → pore in porous substrate 20 → second membrane portion 22c, or A 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 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 body 22 has hydroxide ion conductivity. During 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 is preferably dense. The relative density of the inorganic solid electrolyte body 22 calculated by the Archimedes method is not particularly limited, but is preferably 90% or more, more preferably 92% or more, and further preferably 95% or more. The inorganic solid electrolyte body 22 can be densified by, for example, hydrothermal treatment.

  The inorganic solid electrolyte body 22 can be made of a ceramic material having hydroxide ion conductivity. As such a ceramic material, a known ceramic having hydroxide ion conductivity can be used, and a layered double hydroxide (LDH: Layered Double Hydroxide) described below is particularly preferable.

LDH is M ²⁺ _1−x M ³⁺ _x (OH) _{2 An} ⁻ x / n · mH ₂ O (where M ²⁺ is a divalent cation, M ³⁺ is a trivalent cation, and 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 which means 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. 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 constituent elements, 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 production method, and can be mixed into the LDH from, for example, raw materials and base materials.

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 exactly specify LDH by a general formula. If mainly ^Ni 2+ hydroxide base ^layer, Al 3+, assuming shall be composed of ^{Ti 4+} and OH groups, LDH of the general _{^{formula: Ni 2+ 1-x-y}} 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, 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 the “basic composition”, and other elements or ions (of the same element) to the extent that elements such as Ni ²⁺ , Al ³⁺ , and Ti ⁴⁺ do not impair the basic characteristics of LDH. (Including elements or ions of other valences or elements or ions which can be inevitably mixed in the production process).

  In the present embodiment, 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 part 22b and the second film part 22c. The composite part 22a is arranged in the continuous hole 20a of the porous substrate 20. The composite portion 22a is impregnated in the continuous hole 20a 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.

  In the present embodiment, the composite portion 22a extends over substantially the entire area of the continuous pores 20a of the porous substrate 20, but the inorganic solid electrolyte body 22 is at least one of the first film portion 22b and the second film portion 22c. When there is no one, the composite part 22a may be impregnated only in a part of the porous base material 20.

  The first film-like 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-shaped portion 22c continues to the anode 14 side of the composite portion 22a. The second film 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 is made of a hydroxide ion conductive ceramic component. The thickness of each of the first film-like portion 22b and 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. 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.

  Each of the plurality of metal components 24 is arranged in the composite part 22a. Specifically, the metal component 24 may be disposed in a gap between the porous substrate 20 and the composite portion 22a, or may be disposed inside the composite portion 22a. That is, the metal component 24 may be sandwiched between the porous substrate 20 and the composite portion 22a, or may be embedded in the composite portion 22a.

  As described above, since the voids in the composite portion 22a are filled with the metal component 24, the density of the inorganic solid electrolyte body 22 is easily improved as compared with a method of completely eliminating the voids when the composite portion 22a is formed. be able to. Thereby, the permeation of the oxidizing agent from the cathode 12 to the anode 14 and the permeation of the fuel from the anode 14 to the cathode 12 can be suppressed, so that the decrease in the electromotive force of the solid alkaline fuel cell 10 can be suppressed.

  Further, even if a minute crack is generated in the composite part 22a due to the temperature distribution or the wet / dry distribution in the composite part 22a during the long-term operation of the solid alkaline fuel cell 10, the metal component 24 Is arranged, it is possible to suppress the crack from developing. In particular, when the porous substrate 20 is made of a polymer material or a metal material, the crack can be further suppressed from developing. Therefore, permeation of the oxidant from the cathode 12 to the anode 14 and permeation of the fuel from the anode 14 to the cathode 12 can be suppressed for a long period of time.

  Each metal component 24 is a Group 8-10 element such as a platinum group element (Ru, Rh, Pd, Ir, Pt) or an iron group element (Fe, Co, Ni), or a Group 11 element such as Cu, Ag, or Au. It is constituted by one kind selected from elements. The metal to be selected is not limited as long as it is stably present in the LDH film. In particular, it is preferable that each metal component 24 be composed of Pt, since Pt can be subjected to electrolytic deposition in a manufacturing process described later.

  Each metal component 24 is arranged in a partial region R1 of the electrolyte 16 that extends in a plane direction perpendicular to the thickness direction. The partial region R1 is a partial region of the electrolyte 16. In the thickness direction, the thickness TH1 of the partial region R1 is preferably equal to or less than 1/10 of the thickness TH2 of the porous substrate 20. By distributing each metal component 24 thinly only in a part of the region R1 as described above, it is possible to suppress the electrolyte 16 from exhibiting electron conductivity. The thickness TH1 of the partial region R1 is not particularly limited, but can be, for example, 10 μm or less, preferably 5 μm or less, and more preferably 2 μm or less.

  It is preferable that the partial region R1 is disposed closer to the cathode 12 than the center of the porous substrate 20 in the thickness direction. That is, the partial region R1 is preferably located near the cathode 12. This makes it possible to achieve both gas barrier properties and durability.

  The average equivalent circle diameter of the metal component 24 in the cross section of the electrolyte 16 is not particularly limited, but may be, for example, 0.01 to 1 μm. The average equivalent circle diameter of the metal component 24 is preferably 0.5 μm or less, more preferably 0.1 μm or less. This makes it possible to achieve both gas barrier properties and durability. The average equivalent circle diameter of the metal component 24 is obtained by observing a cross section of the electrolyte 16 with an electron microscope and arithmetically averaging the equivalent circle diameters of 100 metal components 24 selected at random. The equivalent circle diameter of the metal component 24 is the diameter of a circle having the same area as the metal component 24 when the cross section of the electrolyte 16 is observed with an electron microscope. The 100 metal components 24 may be selected from a plurality of visual fields. The magnification of the electron microscope may be appropriately set according to the cross-sectional size of the metal component 24.

(Method for producing electrolyte 16)
Next, a method for manufacturing the electrolyte 16 will be described.

  First, a porous substrate 20 is prepared.

  Next, a mixed sol of alumina and titania is prepared, and the mixed sol penetrates all or most of the inside of the porous substrate 20.

  Next, the porous base material 20 into which the mixed sol has penetrated is subjected to heat treatment (atmospheric atmosphere, 50 to 150 degrees, 1 to 30 minutes) to form an alumina / titania layer in each hole of the porous base material 20. .

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

  Next, the porous substrate 20 is subjected to hydrothermal treatment in the raw material aqueous solution. At this time, by appropriately adjusting the hydrothermal treatment conditions (100 to 150 degrees, 10 to 100 hours), the composite portion 22a is formed in the porous base material 20 and both main surfaces of the porous base material 20 The first film-like portion 22b and the second film-like portion 22c are formed to become the electrolyte 16. At this time, gaps are formed between the porous substrate 20 and the composite portion 22a, and pores are formed in the composite portion 22a.

Next, LDH is immersed in a molten metal-containing solution (for example, tetraammine platinum hydroxide aqueous solution [Pt (NH ₃ ) ₄ ] (OH) ₂ or the like), and the porous substrate 20 filled with the composite portion 22a is immersed. Infiltrate the molten metal ions into the metal. The infiltrated metal ions accumulate in gaps between the porous substrate 20 and the composite portion 22a and in pores in the composite portion 22a. Thereafter, an electrode (for example, a platinum foil surface-treated and platinum-blackened) is attached so as to sandwich the electrolyte 16 and a current is applied, whereby the metal is electrolytically deposited and solidified. Thereby, the metal component 24 is arranged in the gap between the porous base material 20 and the composite portion 22a and in the pores in the composite portion 22a. As described above, by filling the voids in the composite portion 22a with the metal component 24, the denseness of the electrolyte 16 can be improved. As a result, the permeation of the oxidizing agent from the cathode 12 to the anode 14 and the permeation of the fuel from the anode 14 to the cathode 12 can be suppressed, so that the decrease in the electromotive force of the solid alkaline fuel cell 10 can be suppressed.

In the present embodiment, an alkaline metal-containing solution is used. However, if the electrolyte 16 is a cation exchange membrane, an acidic metal-containing solution (for example, chloroplatinate acid solution H ₂ PtCl ₆ ) may be used.

  In addition, although the electrolytic deposition treatment is used to deposit the metal, the present invention is not limited to this as long as the insulation of the electrolyte 16 can be ensured and the permeability of the oxidizing agent and the fuel can be suppressed.

(Modification of Embodiment)
Although the embodiments of the present invention have been described above, 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 embodiment, the electrolyte 16 has a plurality of metal components 24. However, if the electrolyte 16 has at least one metal component 24, the cathode Permeation of the oxidant from the anode to the anode 14 and permeation of the fuel from the anode to the cathode 12 can be suppressed.

[Modification 2]
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. That is, the inorganic solid electrolyte body 22 does not need to include 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-like portion 22b, the composite portion 22a may be impregnated into the entire continuous pores 20a of the porous substrate 20, or may be continuous with the porous substrate 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 holes 20a of the porous base material 20 on the cathode 12 side, at least a part of the anode 14 may be disposed in the void region of the continuous holes 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 base material 20, at least a part of the cathode 12 may be arranged 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 3]
In the above embodiment, the inorganic solid electrolyte body 22 has the metal component 24 arranged in the partial region R1, but may further have another metal component arranged in another partial region. Good. The other partial region is a region that extends in the plane direction at a position apart from the partial region R1 in the thickness direction. The other metal component arranged in another partial region can be made of a metal different from the metal component 24 arranged in the partial region R1. Thus, by arranging the metal components 24 in multiple layers, permeation of the oxidant and the fuel can be further suppressed.

[Modification 4]
In the above-described 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. As an electrochemical cell, for example, it can be applied to a fuel cell using protons as a carrier, a secondary battery (a nickel zinc secondary battery, a zinc air secondary battery, etc.), an electrolytic cell that generates hydrogen and oxygen from water vapor, and the like. it can. 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 those arranged.

[Modification 5]
In the above embodiment, as shown in FIG. 2, the plurality of metal components 24 are arranged in the gap between the porous base material 20 and the composite portion 22a and inside the composite portion 22a. Not limited. The plurality of metal components 24 may be disposed only in the gap between the porous substrate 20 and the composite portion 22a, or may be disposed only inside the composite portion 22a.

[Modification 6]
In the above embodiment, the composite portion 22a is formed by performing a hydrothermal treatment on the porous base material 20 on which the alumina / titania layer is formed in an aqueous solution of the raw material. However, the present invention is not limited to this.

  For example, the composite portion 22a is formed by printing a paste obtained by mixing a binder material (for example, a polymer binder material such as polyvinylidene fluoride powder) and a ceramic material having hydroxide ion conductivity (for example, LDH powder). After forming the sheet, the sheet can also be formed by subjecting the sheet to heat treatment or hot pressing. In this case, the porous substrate 20 is constituted by the binder material solidified by the heat treatment, and the composite portion 22a (an example of the “ion conductor”) is constituted by the ceramic particles.

  Even in such a composite part 22a, it is difficult to completely densify the composite part 22a, and a void (a gap between the porous substrate 20 and the composite part 22a or the composite part 22a) is formed in the composite part 22a. Pores). Therefore, the voids in the composite portion 22a can be filled with the metal component 24 by electrolytically depositing the metal component 24 by the method described in the above embodiment. As a result, the density of the electrolyte 16 can be easily improved, so that the permeation of the oxidizing agent from the cathode 12 to the anode 14 and the permeation of the fuel from the anode 14 to the cathode 12 can be suppressed. Further, even if a minute crack occurs in the composite portion 22a, the metal component 24 is disposed in the composite portion 22a, so that the crack can be suppressed from developing. As a result, permeation of the oxidant from the cathode 12 to the anode 14 and permeation of the fuel from the anode 14 to the cathode 12 can be suppressed for a long period of time. In particular, when the porous base material 20 is made of a polymer binder material, the crack can be further suppressed from developing.

DESCRIPTION OF SYMBOLS 10 Solid alkaline fuel cell 12 Cathode 14 Anode 16 Electrolyte 16S Cathode side surface 16T Anode side surface 20 Porous substrate 22 Inorganic solid electrolyte body 22a Composite part 22b First film part 22c Second film part 24 Metal component

Claims (9)

A porous substrate having a three-dimensional network structure and forming continuous pores,
Having ion conductivity, an ion conductor disposed in the continuous hole,
A plurality of metal components arranged in the gap between the porous substrate and the ion conductor,
Equipped with a,
In the cross section of the porous substrate, the average circle equivalent diameter of the plurality of metal components is 1 μm or less,
Electrolyte for electrochemical cells. The plurality of metal components are arranged in a partial region extending in a plane direction perpendicular to the thickness direction of the electrochemical cell electrolyte ,
The electrolyte for an electrochemical cell according to claim 1. In the thickness direction, the thickness of the partial region is 1/10 or less of the thickness of the porous substrate.
The electrolyte for an electrochemical cell according to claim 2. Each of the plurality of metal components is Pt;
For electrochemical cell electrolyte according to any one of claims 1 to 3. A porous substrate forming continuous pores,
Having ion conductivity, an ion conductor disposed in the continuous hole,
A plurality of metal components arranged in the gap between the porous substrate and the ion conductor,
Equipped with a,
In the cross section of the porous substrate, the average circle equivalent diameter of the plurality of metal components is 1 μm or less,
Electrolyte for electrochemical cells. A porous substrate forming continuous pores,
Having ion conductivity, an ion conductor disposed in the continuous hole,
A plurality of metal components disposed in the ion conductor,
Equipped with a,
In the cross section of the porous substrate, the average circle equivalent diameter of the plurality of metal components is 1 μm or less,
Electrolyte for electrochemical cells. The porous substrate has a three-dimensional network structure,
The electrolyte for an electrochemical cell according to claim 5 . A cathode to which an oxidant is supplied;
An anode to which fuel is supplied;
The electrolyte for an electrochemical cell according to any one of claims 1 to 7 , which is disposed between the cathode and the anode,
An electrochemical cell comprising: The plurality of metal components are arranged in a partial region extending in a plane direction perpendicular to a thickness direction of the electrochemical cell electrolyte ,
The partial region is disposed closer to the cathode than the center of the porous substrate in the thickness direction,
An electrochemical cell according to claim 8 .

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