JP2012074371A - Solid electrolyte material, and metal-air all-solid secondary battery manufactured using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte material, and a metal-air all-solid secondary battery manufactured using the solid electrolyte material.SOLUTION: An electrolyte material of the present invention is a gelatinized product of MO(OH)(in the formula, M represents an element belonging to group-4, -13 or -14 on the periodic table, and each of a and b is a value determined according to a valence of M so that the gelatinized product is electrically neutral) and contains a basic hydroxide. The electrolyte material is obtained by agitating, under conditions of the presence of a basic hydroxide, an alcoholic solution of an alkoxide of an element belonging to group-4, -13 or -14 on the periodic table to produce a gelatinized product and then subjecting the gelatinized product to heat treatment.

Description

  The present invention relates to a solid electrolyte material and an all-solid secondary battery using the same.

  Among the secondary batteries, the lithium ion battery is considered to have the highest energy density (the amount of electric power that can be discharged with respect to the battery weight) at present, but the secondary battery exceeds the energy density of the lithium ion battery. For example, metal-air secondary batteries have attracted attention. In the metal-air secondary battery, the reactant of the positive electrode is oxygen in the air, and the negative electrode is metal. The greatest feature of this metal-air secondary battery is that, since oxygen in the atmosphere is utilized in the positive electrode, the weight of the reactant in the positive electrode can theoretically be reduced to zero. Since the weight of the reaction material at the positive and negative electrodes and the weight of the electrolyte that mediates the reaction occupy most of the weight of the battery, the metal-air secondary battery that can reduce the reaction material on one electrode to zero, There is a possibility that the energy density can be dramatically improved.

  Conventionally, a metal-air battery has an air electrode in which a conductive material such as carbon powder and an oxygen reduction catalyst are combined as a positive electrode, zinc, aluminum, iron, hydrogen, etc. as a negative electrode, and an electrolyte such as an alkaline aqueous solution. It was something to prepare. In general, an aqueous electrolyte such as an alkaline aqueous solution has strong alkalinity, so that it is necessary to seal liquid leakage due to corrosion, and there is a problem in terms of portability. In addition, since an aqueous solution is used, there is a limit to improving the energy density. For example, Patent Document 1 proposes a battery using an ionic liquid, but it is difficult to control and, as described above, it is a liquid, and thus problems such as liquid leakage are not solved. In contrast, in recent years, there are batteries that use organic solvent electrolytes or organic polymer gel electrolytes. However, since these electrolytes are volatile and flammable, the electrolytes are depleted by long-term storage in an unused state. There is also a risk of causing explosive destruction due to combustible components when the battery is damaged.

JP 2008-293678 A

  This invention is made | formed in view of the said situation, and it aims at forming the main component of the solid electrolyte of a metal-air all-solid-state secondary battery with a non-organic substance.

In the present invention, MO _a (OH) _b (wherein M represents an element of Group 4, 13 or 14 of the periodic table, and a and b are electrically neutral depending on the valence of M. The electrolyte material is characterized in that it contains a basic hydroxide. The electrolyte material of the present invention produces a gelled product by stirring an alcohol solution of an alkoxide of a group 4, 13 or 14 element of the periodic table in the presence of a basic hydroxide, and heat-treating this gelled product. It is obtained by doing. The temperature of the heat treatment is preferably 600 to 800 ° C.

In the electrolyte material of the present invention, the M element is preferably Zr, and the ratio of the molar amount of the basic hydroxide to the molar amount of the MO _a (OH) _b (the molar amount of the basic hydroxide). It is also preferred that the amount / mole amount of MO _a (OH) _b ) x is 0.2 or more and 5 or less. When the basic hydroxide is an alkali metal hydroxide, x is 4 or less, and when the basic hydroxide is an ammonium hydroxide salt, x is 1 or more. Recommended. In the electrolyte material of the present invention, the gelled product may contain a ketone compound.

  Further, the present invention is a metal-air all-solid secondary battery comprising an air electrode containing carbon, a metal electrode containing metal, and a first solid electrolyte, wherein the first solid electrolyte is any one of the above. The metal-air all-solid secondary battery which is the electrolyte material described in 1) is also included.

  Furthermore, the present invention is a metal-air all-solid secondary battery including an air electrode including carbon, a metal electrode including a metal, a conductor, and a second solid electrolyte, and a first solid electrolyte, A metal-air all-solid secondary battery, which is the same or different from the second solid electrolyte and is an electrolyte material as described above, is also included. In the metal-air all-solid secondary battery, (i) an air electrode, a first solid electrolyte, and a metal electrode are provided in this order, and the metal electrode has a metal directly on each particle surface of the second solid electrolyte and Partly formed, the metal electrode includes a second solid electrolyte in which a metal is formed, a conductor in a mixed state, and (ii) the metal is iron, and the conductor is Carbon is preferable, and iron is supported on the carbon. In addition, when the mixing ratio of the second solid electrolyte in which the metal is formed in the metal electrode and the conductor is arranged so that the ratio of the solid electrolyte increases as the distance from the air electrode increases, the metal electrode can smoothly take out electricity. This is preferable.

  In the metal-air all solid state secondary battery of the present invention, an air electrode containing carbon is provided on one side of the first solid electrolyte, a metal electrode containing metal is provided on the other side, and the carbon is added. It is preferable that the air electrode to be provided has a carbon layer with catalyst. The metal of the metal electrode is recommended to be iron or magnesium.

  In the metal-air all solid state secondary battery of the present invention, the metal of the metal electrode is preferably formed directly on the surface of the first or second solid electrolyte. In this case, the metal electrode has a thickness of 1 nm or more and less than 100 μm. It is preferable that the Fe concentration is 30 atomic% or more. An example of a method for directly forming the metal electrode metal on the surface of the first or second solid electrolyte is a sputtering method.

According to the solid electrolyte according to the present invention, MO _a (OH) _b (wherein M represents an element of Group 4, 13 or 14 of the periodic table, and a and b depend on the valence of M) In this case, a basic hydroxide is contained in the gelled product (value determined so as to be electrically neutral), so that sufficient conductivity is obtained even at room temperature (for example, about 10 ⁻³ S / cm). Can be demonstrated. This solid electrolyte is useful for, for example, a metal-air all-solid secondary battery, and the metal-air all-solid secondary battery using the solid electrolyte of the present invention can be charged and discharged and is sufficient as a secondary battery. Can be operated.

FIG. 1 is a diagram showing a procedure for producing a zirconia gel in an example described later. FIG. 2 is a graph showing the AC conductivity of zirconia gel when the temperature is changed from 20 ° C. to 80 ° C. in Examples described later. FIG. 3 is a graph showing the AC conductivity of the zirconia gel when the molar ratio x of potassium hydroxide is changed in the examples described later. FIG. 4 is a graph showing the AC conductivity of the zirconia gel when the molar ratio y of acetylacetone is changed in the examples described later. FIG. 5 is a diagram showing a procedure for producing a zirconia gel in Examples described later. FIG. 6 is a graph showing the AC conductivity of the zirconia gel when the temperature is changed from 20 ° C. to 80 ° C. in the examples described later. FIG. 7 is a graph showing the AC conductivity of zirconia gel when the molar ratio x of tetramethylammonium hydroxide is changed in the examples described later. FIG. 8 is a graph showing the AC conductivity of zirconia gel when the molar ratio y of acetylacetone is changed in the examples described later. FIG. 9 is a schematic view showing a configuration of a cylindrical battery produced in Examples described later. FIG. 10 is a graph showing the cell voltage of a battery manufactured in an example described later. FIG. 11 is a diagram showing a procedure for producing a zirconia gel in Examples described later. FIG. 12 is a graph showing an XRD pattern of zirconia gel powder in Examples described later. FIG. 13 is a graph showing the relationship between the heat treatment temperature during the production of zirconia gel and the AC conductivity of the zirconia gel in the examples described later. FIG. 14 shows the results of simultaneous differential heat / thermogravimetric measurement of zirconia gel in Examples described later. FIG. 15 is a graph showing the relationship between current and power density of a metal-air all solid state secondary battery in Examples described later. FIG. 16 is a graph showing charge / discharge characteristics (relationship between time and cell voltage) in the examples described later. FIG. 17 is a diagram showing a procedure for producing carbon carrying iron in Examples to be described later. FIG. 18 is an SEM photograph of carbon carrying iron produced in the examples described later. FIG. 19 is a graph showing a charge curve and a discharge curve of a battery manufactured in an example described later.

The present inventors examined a new solid electrolyte to replace the organic solid electrolyte. As a result, MO _a (OH) _b (wherein M represents an element of Group 4, 13 or 14 of the periodic table, and a and b are electrically neutral depending on the valence of M. When a basic hydroxide is included in the gelled product), it becomes clear that hydroxide ions can be conducted to a high degree and is useful as an electrolyte material. Non-organic (inorganic) solid electrolyte It came to realize.

When a group 4, 13, or 14 element forms a MO _a (OH) _b gel, ie, an oxide or oxyhydroxide, even in the presence of a basic hydroxide, ie, in a strongly alkaline environment The gelled product can be stabilized. The element M is preferably Zr, Al, or Si, and particularly preferably Group 4 Zr. When MO _a (OH) _b is an oxide, MO _a (OH) _b can be expressed by MO _a (ie, b = 0), and a is (M valence) = (O atom Value (usually −2) × a). When MO _a (OH) _b is an oxyhydroxide, the values of a and b are (M valence) + (O valence (usually −2)) × a + (OH valence). (Normally −1)) × b = 0 is satisfied (however, a> 0, b> 0). When a metal alkoxide is used as a starting material, OH groups tend to remain in the structure by hydrolysis. The ratio of a and b can be controlled by the heat treatment conditions. Generally, the higher the heat treatment temperature, the larger the value of a, and the lower the OH group concentration (that is, the smaller the value of b). Cheap. For example, in the examples described later, the heat treatment is performed at 110 ° C. for 5 hours, and the electrical neutrality is satisfied when a = 1 and b = 2 in stoichiometry (that is, ZrO ₁ (OH) ₂ ). Considering this, the value of a is approximately 1.0 to 1.8, and the value of b is approximately 0.4 to 2.0.

The gelled product of MO _a (OH) _b may be a gel-like product by forming a network of a plurality of Ms and Os by M-O-M bonds, and other groups (for example, alkoxy groups), etc. May be bound or remain.

As the basic hydroxide, a compound capable of liberating OH ⁻ ions can be used. By using such a basic hydroxide, OH ^- ions can move in the solid electrolyte, and the conductivity of the electrolyte can be increased. Preferred basic hydroxides are strong alkalis that completely dissociate OH ⁻ ions, such as alkali metal hydroxides and ammonium hydroxide salts. As the alkali metal hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide and the like are preferable, and potassium hydroxide is particularly preferable. The ammonium hydroxide salt is preferably an aliphatic quaternary ammonium hydroxide, such as a tetra C _1-3 alkyl ammonium compound, particularly tetramethyl ammonium hydroxide.

The molar amount of the basic hydroxide and the MO _a (OH) molar quantity ratio of _b (molar amount of basic hydroxide / MO _a (OH) molar amount of _b) x is 0.2 or more, 5 Or less, more preferably 0.5 or more and 4.5 or less.

  When the basic hydroxide is an alkali metal hydroxide, x is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. In the alkali metal hydroxide, the conductivity is particularly good when x is 4 or less. When the hydroxide is an ammonium salt, x is preferably 1 or more, more preferably 1.5 or more, and further preferably 2 or more. In the ammonium salt, the conductivity is particularly good when x is 1 or more.

  Further, the gelled product may contain a ketone compound added to stabilize the alkoxide in the sol preparation stage. The ketone compound includes a monoketone compound, a diketone compound, a triketone compound, and the like, and a diketone compound is preferable. As the diketone compound, α-diketone compounds (such as diacetyl), β-diketone compounds, γ-diketone compounds (such as 2,5-hexadione) and the like, in particular, β-diketone compounds can be used. β-diketone compounds include acetylacetone, 2,2-dimethylpentane-3,5-dione, 2-methyl-1,3-butanedione, 1,3-butanedione, 2,2,6,6-tetramethyl-3. Aliphatic chain diketone compounds such as 1,5-heptanedione and 3-methyl-2,4-pentanedione; aliphatic cyclic diketone compounds such as 2-acetylcyclopentanone and 2-acetylcyclohexanone; 1,3-diphenyl Examples include aromatic ring diketone compounds such as -1,3-propanedione, benzoylacetone, and dibenzoylacetone. Preferred ketone compounds are those having 3 to 10 carbon atoms (more preferably 4 to 6), particularly aliphatic chain diketone compounds having 3 to 10 carbon atoms (more preferably 4 to 6) such as acetylacetone. It is.

(Molar amount / MO _a (OH) molar amount of _b ketone compound) y molar amount of the MO _a (OH) _b molar amount of the ratio of the ketone compound, 0.05 or more, preferably 5 or less, more preferably Is 0.10 or more and 4 or less, more preferably 0.10 or more and 3 or less. In particular, when the basic hydroxide is an ammonium hydroxide salt, y is recommended to be 0.15 or more.

The resulting gel containing the ketone compound becomes MO _a (OH) _b , which is generically referred to as an oxide or oxyhydroxide, because the ketone compound is burned away by heat treatment at 300 ° C. or higher. The gel after the heat treatment is usually obtained in the form of a powder.

  The electrolyte material of the present invention stirs an alcohol solution of an alkoxide of an element of Group 4, 13 or 14 of the periodic table (hereinafter simply referred to as an alkoxide compound) in the presence of a basic hydroxide, and is allowed to stand at room temperature. Alternatively, it can be obtained by holding at about 50 ° C. (for example, 40 to 60 ° C.) to produce a gelled product (intermediate gelled product) and heat-treating the gelled product. -A gel method can be used.

  As an alkoxide of an element of Group 4, 13 or 14 of the periodic table, an alkoxide having about 1 to 10 carbon atoms (preferably about 2 to 7) such as methoxide, ethoxide, propoxide, butoxide, pentoxide can be used. . The alcohol for dissolving the alkoxide is not particularly limited as long as it is volatile, but ethanol, such as methanol and ethanol, is preferably used.

The concentration of the alkoxide compound in the alcohol solution is, for example, 5 to 80% by mass, preferably 10 to 60% by mass, and more preferably 20 to 50% by mass. In addition, the concentration of the basic hydroxide may be appropriately determined depending on the amount of MO _a (OH) _{b and} the amount added for exhibiting the characteristics (ionic conductivity) of the electrolyte material. By stirring and leaving the alcohol solution of the basic hydroxide and the alkoxide compound, the intermediate gelled product can be generated as described above.

  As long as the intermediate gelled product is generated, the temperature condition of the standing is not particularly limited. However, for example, when it is held at about 40 to 60 ° C., it usually takes about 5 to 10 days to complete the generation.

  By heat-treating the intermediate gelled product, the solid electrolyte material (final gelled product) of the present invention can be obtained. The heat treatment temperature may be set to an arbitrary temperature of 600 ° C. or lower when an inorganic basic hydroxide is used, but by setting the heat treatment temperature to 600 to 800 ° C., the crystallinity of the obtained gel powder is increased. While being able to raise, high electrical conductivity is securable also near room temperature. On the other hand, when an organic basic compound (for example, tetramethylammonium hydroxide) is used, the temperature can be, for example, about 70 to 150 ° C, preferably about 100 to 120 ° C.

  The use of the solid electrolyte material is not particularly limited, and can be used for a metal-air secondary battery, a nickel metal hydride battery, a nickel cadmium battery, or the like, and in particular, a metal having an air electrode and a metal electrode containing a metal- Preferably, the metal-air all-solid secondary battery is provided with an air electrode containing carbon on one side of the solid electrolyte (first solid electrolyte) and on the other side. More preferably, a metal electrode including a metal is provided, and the air electrode including carbon includes a carbon layer with a catalyst.

  The metal electrode functions as a negative electrode of a metal-air all-solid secondary battery. When the metal used is M, a reaction of the following formula (1) occurs.

  Zinc, aluminum, lithium, iron, magnesium, etc. can be used as the metal of the metal electrode, but iron and magnesium are preferred. Magnesium is an abundant element unlike lithium and the like, and an improvement in battery voltage can be expected. Moreover, the said iron is meant to include iron alloys and iron-containing substances. Although the absolute value of the oxidation-reduction potential is relatively small, iron has an advantage that the metal electrode is stabilized even when repeatedly charged and discharged because the ionized product (iron ion) does not move. In addition to the metal, the metal electrode preferably contains a conductor (for example, carbon, carbon alloy, carbide, etc.) and the solid electrolyte material of the present invention (second solid electrolyte) (especially a mixture consisting of only these). Preferably). By including a conductor, an increase in cell resistance of the battery due to passivation of the metal of the metal electrode can be reduced, and particularly when the metal is iron or aluminum (especially iron), the effect can be exhibited remarkably. Further, by using a solid electrolyte (second solid electrolyte) for the metal electrode, it is possible to efficiently exchange electrons generated by metal oxidation or electrons from hydroxide ions. The second solid electrolyte may be the same as or different from the first solid electrolyte. When a mixture of metal, conductor, and solid electrolyte material (second solid electrolyte) is used for the metal electrode, the ratio of conductor to metal (conductor / metal) is about 0.1 / 1 to 10/1 by mass ratio. The ratio of solid electrolyte material to metal (solid electrolyte material / metal) is about 1/1 to 50/1.

  The content ratio of the metal element in the metal electrode is, for example, 15 atomic% or more, preferably 20 atomic% or more, more preferably 30 atomic% or more, and may be 100 atomic%.

The metal electrode may be a metal foil, for example, metal powder having an average particle diameter of 0.01 to 10 μm (more preferably an average particle diameter of 0.1 to 5 μm) and metal wool (for example, a fiber diameter of 10 ˜60 μm) may be formed into a pellet shape.
It is also preferable that the metal electrode is directly formed on the surface of the solid electrolyte (first solid electrolyte or second solid electrolyte) material by, for example, PVD method (for example, sputtering method, vacuum deposition method). It is known that a battery using a solid electrolyte has a large resistance at the interface and deteriorates the characteristics. In addition, when a powdery substance is used as the battery material, a battery is formed by applying pressure by mixing each element (electrode material, electrolyte material). In this case, contact between the elements is sufficient. However, there is a possibility that the characteristics cannot be fully exhibited. Therefore, by forming the metal electrode so as to be in direct contact with the surface of the solid electrolyte material, the resistance between the metal electrode and the electrolyte can be lowered to improve the characteristics. When the first and second solid electrolytes are included, the metal of the metal electrode may be directly formed on the second solid electrolyte. As a method of directly forming the metal electrode, a sputtering method is particularly preferable. This is because film formation by sputtering is performed in a vacuum, so that contamination of impurities can be prevented, the surface is cleaned by ion energy during film formation, and the interface is improved by energy assist, This is because there are advantages such as improved adhesion.

  The thickness of the metal electrode is, for example, 1 nm or more, and is preferably 0.1 mm or more because it sufficiently acts as a negative electrode. On the other hand, if the thickness of the metal electrode becomes too thick, it is difficult to make good contact with the electrolyte and the anode material cannot be used effectively, or it becomes difficult to reduce the weight and thickness of the element. The thickness is preferably 3 mm or less, more preferably 1 mm or less, and still more preferably less than 100 μm.

  In particular, when the metal electrode is directly formed on the surface of the solid electrolyte material, the thickness of the metal electrode is preferably 1 nm or more and less than 100 μm (more preferably 3 nm or more and 1 μm or less). The Fe concentration in the metal electrode is 30 atomic%. The above is preferable. When the thickness of the metal electrode is less than 1 nm, the covering property of the metal electrode on the solid electrolyte is extremely lowered, so that the performance as the electrode layer cannot be sufficiently exhibited. On the other hand, when the thickness of the metal electrode is 100 μm or more, the weight of the metal electrode itself causes an increase in the battery weight and the charging efficiency per unit weight is lowered, which is not preferable. The Fe concentration can be calculated from the analysis value of semi-quantitative analysis of EDX analysis of TEM.

  In the aspect in which the metal electrode includes the metal, the conductor, and the second solid electrolyte, the mutual positional relationship and concentration distribution are not particularly limited. Regarding the positional relationship, for example, the metal, the conductor, and the second solid electrolyte may all be mixed, or may be arranged in layers in an arbitrary order. The concentration distribution may be uniform in the metal electrode or non-uniform for each of the metal, the conductor, and the second solid electrolyte. Particularly for the metal and the second solid electrolyte, it is preferable that the metal is directly and partially (discontinuously) formed on the surface of each particle of the second solid electrolyte. In this case, the thickness of the metal electrode is preferably 1 nm or more. The upper limit of the thickness of the metal electrode is not particularly limited, as long as the shape of the solid electrolyte (for example, powder) is substantially maintained in the state before metal adhesion, for example, about 1/10 of the particle diameter of the solid electrolyte powder, Usually, it is 1 μm or less. The aspect in which the metal is partially formed on the surface of each particle of the solid electrolyte includes the case where the metal is aggregated and formed. What is the thickness of the metal electrode when the metal is partially formed? It means the film thickness converted into a continuous film. If the thickness of the metal electrode is too thin, the metal enters the uneven portion of the solid electrolyte and cannot contact the metal, solid electrolyte, or carbon on the metal surface, and electricity does not flow. On the other hand, if the thickness of the metal electrode is too thick, the proportion of the metal that does not contribute to the reaction increases and the efficiency decreases. The metal coverage is preferably 50% or more. When the metal is formed directly and partially on the surface of each particle of the second solid electrolyte, the conductor powder (for example, a conductor powder mainly composed of carbon) and the second solid electrolyte (metal is formed on the surface) Mixture (especially, when the mixing ratio of the second solid electrolyte in which the metal is formed in the metal electrode and the conductor is such that the ratio of the solid electrolyte increases as it approaches the air electrode, the metal electrode can smoothly take out electricity. When the first solid electrolyte (no metal is formed) and the air electrode are provided in this order, hydroxide ions introduced from the air electrode are removed from the discontinuous portion of the metal. It can enter and react with iron to efficiently transfer electrons to the conductor, and a battery with high utilization efficiency can be realized.

  In an embodiment in which the metal electrode includes a metal, a conductor, and a second solid electrolyte, it is preferable that the metal be supported on the conductor, and it is particularly preferable that iron be supported on carbon. By supporting the metal on the conductor, a nano-sized metal can be formed, and the surface area contributing to the reaction can be increased.

  The carbon-containing air electrode functions as a positive electrode of a metal-air all-solid secondary battery, and a reaction of the following formula (2) occurs.

In order to sufficiently function as a positive electrode, the thickness is preferably 0.05 mm or more, and more preferably 0.1 mm or more. On the other hand, if the thickness of the positive electrode (for example, the carbon layer with catalyst) becomes too thick, it becomes difficult to efficiently form the three-phase interface of electrolyte / catalyst / air. Therefore, the thickness of the positive electrode is preferably 0.3 mm or less, more preferably 0.2 mm or less. When the air electrode containing carbon includes a carbon layer with a catalyst, the catalyst may be any catalyst that can promote the oxygen reduction reaction, and examples thereof include Pt and MnO ₂ . The form of the carbon layer may be a carbon powder compact, or carbon paper or the like may be used.

  The thickness of the solid electrolyte layer is preferably about 0.1 mm in order to sufficiently exhibit the action of conducting hydroxide ions and prevent a short circuit. On the other hand, if the thickness of the solid electrolyte layer becomes too thick, the actual resistance (battery internal resistance) increases, resulting in a problem that current cannot be extracted. Therefore, the thickness of the solid electrolyte layer is preferably 0.3 mm or less.

  The metal-air all solid state secondary battery is formed by laminating an air electrode containing carbon on one side of the solid electrolyte layer and a metal electrode containing metal on the other side, and having a room temperature to 500 ° C., 100 MPa or less, 1 to 100 minutes. It can be produced by pressing under conditions. In addition, the solid electrolyte layer and the air electrode, or the solid electrolyte layer and the metal electrode may be provided with a primer layer for improving adhesion.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by the following examples, and can of course be implemented with appropriate modifications within a range that can be adapted to the above-described gist. Included in the range.

Example 1
The zirconia gel was produced according to the procedure shown in FIG. First, an ethanol solution of zirconium tetra n-butoxide (zirconium tetra n-butoxide concentration: about 40% by mass) was stirred at room temperature for 30 minutes (S1 in FIG. 1), acetylacetone was added, and the mixture was further stirred at room temperature for 30 minutes ( S2 in Fig. 1. When acetylacetone was not added, an ethanol solution of zirconium tetra-n-butoxide was stirred at room temperature for 60 minutes). Thereafter, potassium hydroxide, water, and ethanol were added to prepare the composition shown in Table 1 below. This solution was stirred at room temperature for 90 minutes (S3 in FIG. 1), and then allowed to stand at 50 ° C. for 5 to 10 days (S4 in FIG. 1). Furthermore, it heat-processed at 110 degreeC for 5 hours (S5 of FIG. 1), and obtained the zirconia gel powder containing potassium hydroxide.

The ionic conductivity (AC conductivity) of the obtained zirconia gel was measured using an electrochemical measurement system (SI 1260, Solartron) and dedicated software (Z-plot). The obtained powder was formed into a pellet (diameter 13 mm, thickness 0.4 to 0.8 mm) by press-bonding using a mold (Shimadzu Corporation, KBr tablet molding machine) under conditions of 5 MPa and 10 min. . Electrodes are formed on both sides of the pellet-like sample by gold sputtering using a mask (area: 0.385 cm ² ) using a quick coater (Sanyu Electronics Co., Ltd., QuickCoater SC-701) under conditions of 3 mV and 5 min. Formed. A gold wire (Niraco Co., Ltd., φ = 0.08 mm) as a lead wire was joined to an electrode with silver paste (Nisshin EM Co., Ltd., Sylbest P-255), and measurement was performed. The results are shown in FIGS.

Fig. 2 shows the alternating current of zirconia gel when the molar ratio x of potassium hydroxide is 0.5, the molar ratio y of acetylacetone is 0, the relative humidity is 60%, and the temperature is changed from 20 ° C to 80 ° C. It is the graph which showed the electrical conductivity (In addition, a vertical axis | shaft is represented by the common logarithm of alternating current conductivity. Hereafter, it is the same about the graph of alternating current conductivity). According to FIG. 2, it was found that the conductivity was as high as about 10 ⁻³ S / cm even near room temperature.

  FIG. 3 shows that the molar ratio of acetylacetone is 0, the relative humidity is 60%, the temperature is 80 ° C., and the molar ratio x of potassium hydroxide is 0.5, 0.68, 1, 2, 3, 4, 5, It is the graph which showed the alternating current conductivity of the zirconia gel when making it change. FIG. 3 shows that the conductivity decreased as the molar ratio of potassium hydroxide increased.

  FIG. 4 shows the relative humidity: 60%, temperature: 80 ° C., the molar ratio x of potassium hydroxide is changed to 0.68, and the molar ratio y of acetylacetone is changed to 0, 0.16, 0.8. It is the graph which showed the alternating current conductivity of the zirconia gel. According to FIG. 4, there was a tendency for the conductivity to decrease with an increase in acetylacetone.

Example 2
Instead of potassium hydroxide, tetramethylammonium hydroxide was used, and the composition of each raw material was as shown in Table 2, and the procedure shown in FIG. A zirconia gel containing was prepared.

  The AC conductivity of the obtained zirconia gel was measured in the same manner as in Example 1. The results are shown in FIGS.

  FIG. 6 shows the AC conductivity of the zirconia gel when the molar ratio x of tetramethylammonium hydroxide is 0.4, the molar ratio y of acetylacetone is 0, and the temperature is changed from 20 ° C. to 80 ° C. It is a graph. FIG. 7 shows that the molar ratio of acetylacetone is 0, the relative humidity is 60%, the temperature is 80 ° C., and the molar ratio x of tetramethylammonium hydroxide is 0.4, 0.5, 1, 2, 3, 4, It is the graph which showed the alternating current conductivity of the zirconia gel when making it change. According to FIGS. 6 and 7, when the molar ratio of tetramethylammonium hydroxide is small, the conductivity is small and insufficient, whereas the electrical conductivity improves as the molar ratio of tetramethylammonium hydroxide increases. I found out.

  FIG. 8 shows the relative humidity: 60%, temperature: 80 ° C., when the molar ratio x of tetramethylammonium hydroxide is changed to 0.4 and the molar ratio y of acetylacetone is changed to 0, 0.16, and 0.8. It is the graph which showed the alternating current conductivity of zirconia gel. According to FIG. 8, there was a tendency for the conductivity to increase with an increase in acetylacetone.

Example 3
Of the zirconia gel obtained in Example 1, 0.1 g of zirconia gel having a potassium hydroxide molar ratio x of 3 and an acetylacetone molar ratio y of 0 was used as an electrolyte to produce a metal-air all solid secondary battery. did.

The metal electrode was prepared by pressing steel wool having a fiber diameter of 30 to 60 μm at 40 MPa and forming it into a pellet form, and 0.2 g of sponge iron (manufactured by Wako, average particle diameter of iron powder: 1 to 5 μm). . As the carbon layer with catalyst, carbon papers manufactured by Chemix Co., Ltd. were prepared by supporting MnO ₂ (5 to 10 mg / cm ² ) and Pt (0.5 mg / cm ² ) as catalysts. Steel wool 4, sponge iron 3, zirconia gel powder 2, and carbon paper 1 with catalyst were laminated in this order and pressed at room temperature and 40 MPa for 1 minute to produce a cylindrical battery with φ: 13 mm. The thickness of each layer was steel wool: 0.2 mm, sponge iron: 0.2 mm, zirconia gel: 0.3 mm, and carbon paper with catalyst: 0.1 mm. A schematic view of the produced cylindrical battery is shown in FIG.

For each battery using MnO ₂ , Pt as catalyst, high performance potentiostat / galvanostat (Solartron, SI 1287, DC polarization voltage: ± 14.5 V (resolution of 100 μV for ± 14.5 V), current: ± 2 A (resolution 100 pA), measurement resolution (limit of analysis theory of the device) [current resolution: 1 pA, voltage resolution: 1 μV]) and frequency response analyzer (Solartron, 1252 A, frequency range: 10 kHz to 300 kHz, AC amplitude: 0 to 3 Vrms) The cell voltage was measured using AC amplitude resolution: 5 mV). The measurement result of the cell voltage is shown in FIG.

According to FIG. 10, it was found that charging and discharging are possible when either MnO ₂ or Pt is used as the catalyst, and the secondary battery operates.

Example 4
The zirconia gel was produced according to the procedure shown in FIG. First, an ethanol solution of zirconium tetra n-butoxide (zirconium tetra n-butoxide concentration: about 60 wt%) was stirred at room temperature for 30 minutes (S1 in FIG. 11), and then potassium hydroxide, water and ethanol were added. Then, zirconium tetra-n-butoxide, ethanol, water, and potassium hydroxide were prepared to have a molar ratio of 1: 10: 3: 1. This solution was stirred at room temperature for 90 minutes (S2 in FIG. 11), and then kept at 60 ° C. for 10 days (S3 in FIG. 11). Furthermore, it heat-processed for 5 hours at any temperature of 110 degreeC, 600 degreeC, and 800 degreeC (S4 of FIG. 11), and obtained the zirconia gel powder containing potassium hydroxide.

The result of having analyzed the obtained gel powder sample by XRD is shown in FIG. The sample heat-treated at 110 ° C. ((a) in FIG. 12) was found to be amorphous with no diffraction peak detected. In the sample heat treated at 600 ° C. ((b) in FIG. 12), peaks attributable to tetragonal zirconia (ZrO ₂ ) and potassium carbonate (K ₂ CO ₃ ) were detected. In the sample heat treated at 800 ° C. ((c) in FIG. 12), peaks attributed to tetragonal and monoclinic zirconia (ZrO ₂ ) and potassium carbonate (K ₂ CO ₃ ) were detected. From these samples, it was found that the peak attributed to tetragonal zirconia (ZrO ₂ ) became sharper as the heat treatment temperature increased, and the crystallinity increased.

In addition, the AC conductivity of the obtained gel powder at a relative humidity of 60% and a temperature of 20 to 80 ° C. was measured. The results are shown in FIG. In the samples heat-treated at 600 ° C. or higher (□ and ▲ in FIG. 13), the conductivity increased by an order of magnitude compared to the samples heat-treated at 110 ° C. (◯ in FIG. 13). Specifically, the AC conductivity σ at 20 ° C. of the sample heat-treated at 600 ° C. is 8.3 × 10 ⁻³ S / cm, and the AC conductivity σ at 20 ° C. of the sample heat-treated at 800 ° C. is 9. It was 2 × 10 ⁻³ S / cm.

Furthermore, in order to evaluate the thermal stability of the obtained gel powder, simultaneous differential heat / thermogravimetric measurement was performed on a sample heat-treated at 110 ° C. The results are shown in FIG. The weight loss between 800 and 1100 ° C. is considered to be due to decomposition of potassium carbonate (K ₂ CO ₃ ), which is a reaction product of KOH and CO ₂ , and decomposition of the electrolyte (zirconia gel) by heat treatment exceeding 800 ° C. It turns out that happens.

Example 5
Except for using a mixed powder composed of pure iron powder, zirconia gel powder, carbon powder (mixing ratio is pure iron powder: zirconia gel powder: carbon powder = 1: 12: 0.48) on the metal electrode. A metal-air all-solid secondary battery was produced in the same manner as in Example 3 and in the same manner as in Example 3 except that only pure iron powder was used for the metal electrode for comparison. Each battery was measured using the same high performance potentiostat / galvanostat as in Example 3, and the relationship between current and power density was examined. The results are shown in FIG. The battery using the mixed powder for the metal electrode ((b) in FIG. 15) showed higher performance than the battery using only the iron powder for the metal electrode ((a) in FIG. 15). By adding carbon to the metal electrode, an electron conduction path was formed, and the increase in cell resistance due to the passivation of iron was reduced, so the performance was considered improved. Moreover, as a result of conducting a charge / discharge test, it was found that the battery using the mixed powder for the metal electrode can also be charged / discharged.

Example 6
A 250 nm Fe thin film was formed by sputtering on solid pellets obtained by pressing the zirconia gel powder of Example 3. As a sputtering apparatus, a magnetron sputtering apparatus (HSM-225) manufactured by Shimadzu Emit was used, and film formation was performed at a power density of 200 W / φ4 inches (power density per magnet) by RF. The process gas was Ar, and the gas pressure was 10 mTorr. After the Fe thin film was formed, the Fe thin film-formed zirconia gel and the same catalyst-coated carbon paper as in Example 3 were laminated and pressed at room temperature and 40 MPa for 1 minute to produce a cylindrical battery with φ: 13 mm. When the produced battery was measured in the same manner as in Example 3, the open-circuit voltage was about 1.1 V, and an ideal open-circuit voltage as an iron-air battery could be obtained.

Example 7
The same zirconia gel powder used in Example 3 was attached to a Kapton tape, and Fe was formed on the surface of the zirconia gel powder by a sputtering method. The film thickness of Fe is 5 nm in terms of continuous film. As a sputtering apparatus, a magnetron sputtering apparatus (HSM-225) manufactured by Shimadzu Emit was used, and film formation was performed at a power density of 200 W / φ4 inches (power density per magnet) by RF. The process gas was Ar, and the gas pressure was 10 mTorr. Thereafter, the solid electrolyte material powder on which the Fe film was formed was collected with a spoon. Instead of steel wool and sponge iron used as the metal electrode in Example 3, carbon powder and the above-described Fe-formed zirconia gel powder were used (in order from the air electrode side, Fe-formed zirconia gel powder and carbon powder). Produced a cylindrical battery in the same manner as in Example 3. In addition, mass ratio of Fe formation zirconia gel powder in a metal electrode and the amount of carbon was 12: 1.

In the same manner as in Example 3, the battery was measured for charge / discharge characteristics under the conditions of charge: 0.5 mA / cm ² and discharge: 0.1 mA / cm ² (three times). The charge / discharge characteristics of the battery of Example 5 (the mass ratio of Fe, electrolyte, and carbon is 1: 12: 0.48) using a mixture of carbon powder and zirconia gel powder were compared. The results are shown in FIG. In the example using the zirconia gel powder formed with Fe as the metal electrode ((A) in FIG. 16), compared with the example using the mixture ((B) in FIG. 16) as the metal electrode, Fe The charge / discharge characteristics equivalent to those in the case of (B) were obtained even though the amount of 1/1000 was 1/1000 on the mass basis. In other words, when zirconia gel powder with Fe film formed as a metal electrode is used, it can be confirmed that good characteristics are exhibited by three times of charge and discharge, and operation as a secondary battery is possible because of high utilization efficiency. I found out.

Example 8
FIG. 17 shows a procedure for producing iron-supported carbon (hereinafter referred to as iron-supported carbon). Carbon black (Ketjen Black, manufactured by Lion Corporation) was impregnated with an ethanol solution of 3.5% by mass of iron acetylacetonate. The mixing ratio was iron: carbon black = 1: 1, 1: 4, 1: 8 by mass ratio. After drying in air at 100 ° C. for 1 day, heat treatment was performed at 400 ° C. for 2 hours in an N ₂ gas atmosphere to produce carbon carrying iron. FIG. 18 shows an SEM image (reflection electron image) of iron-supporting carbon. In FIG. 18, the mass ratios of iron: carbon black of (a), (b), and (c) are 1: 8, 1: 4, and 1: 1, respectively. In (a), (b), and (c), iron nanoparticles of (a) 30 to 50 nm, (b) 20 to 50 nm, and (c) about 30 to 50 nm were observed, respectively.

The iron-supported carbon (metal electrode) prepared with an iron: carbon black mass ratio of 1: 8, the same air electrode as in Example 3 (however, the amount of MnO _{2 in} the air electrode is 1 mg / cm ² ), and zirconia gel powder Was pressed with a uniaxial pressure molding machine under the condition of a pressure of 40 MPa to prepare an iron-air battery. A power generation test was performed at a temperature of 20 ° C. and a relative humidity of 60% under the conditions of charging: 0.5 mA / cm ² and discharging: 0.1 mA / cm ² , and charging / discharging of a battery using iron-supported carbon for the metal electrode. The characteristics were measured ((b) in FIG. 19), and the battery of Example 5 using a mixture of pure iron powder, carbon powder, and zirconia gel powder as the metal electrode (the mass ratio of Fe, electrolyte, and carbon was 1:12). : 0.48, and the particle size of the iron powder was compared with the charge / discharge characteristics ((a) in FIG. 19).

  It was found that (b) using iron-supporting carbon for the metal electrode showed a higher discharge capacity than (a) using iron powder for the metal electrode.

Example 9
A 250 nm magnesium thin film was formed on the solid pellet obtained by pressing the zirconia gel powder of Example 3 using a vacuum deposition method. As the apparatus, a resistance heating type vapor deposition apparatus (BMC-800T) manufactured by Shincron was used. The process gas was Ar, and the gas pressure was 2 mTorr. The sample preparation process after electrode formation is the same as in Example 6. When the created battery was measured in the same manner as in Example 3, charging / discharging could be confirmed, and the open circuit voltage was larger than that of the battery of Example 6.

1 Carbon paper with catalyst 2 Zirconia gel powder 3 Sponge iron 4 Steel wool

Claims (18)

MO _a (OH) _b (wherein M represents an element of Group 4, 13, or 14 of the periodic table, and a and b are electrically neutral depending on the valence of M) An electrolyte material characterized in that it is a gelled product of a defined value) and contains a basic hydroxide.   An electrolyte material obtained by stirring an alcohol solution of an alkoxide of an element of Group 4, 13 or 14 of the periodic table in the presence of a basic hydroxide to form a gel, and heat-treating the gel .   The electrolyte material according to claim 1 or 2, wherein the element of Group 4, Group 13, or Group 14 of the periodic table is Zr. The molar amount of the basic hydroxide and the MO _a (OH) molar quantity ratio of _b (molar amount of basic hydroxide / MO _{a (OH)} molar amount of _b) x is 0.2 or more, 5 The electrolyte material according to claim 1 or 3, wherein:   The electrolyte material according to claim 4, wherein the basic hydroxide is an alkali metal hydroxide, and the x is 4 or less.   The electrolyte material according to claim 4, wherein the basic hydroxide is an ammonium hydroxide salt, and the x is 1 or more.   The electrolyte material according to any one of claims 1 to 6, wherein the gelled product contains a ketone compound.   The electrolyte material according to claim 2, wherein the temperature of the heat treatment is 600 to 800 ° C.   A metal-air all-solid secondary battery comprising an air electrode containing carbon, a metal electrode containing metal, and a first solid electrolyte, wherein the first solid electrolyte is any one of claims 1 to 8. A metal-air all solid secondary battery which is the electrolyte material described. A metal-air all-solid secondary battery comprising an air electrode comprising carbon, a metal electrode comprising a metal, a conductor and a second solid electrolyte, and a first solid electrolyte,
The metal-air all-solid-state secondary battery which is the electrolyte material in any one of Claims 1-8 by which the 1st and 2nd solid electrolyte is the same or different.   An air electrode containing carbon is provided on one side of the first solid electrolyte, a metal electrode containing metal is provided on the other side, and the air electrode containing carbon has a carbon layer with catalyst. Item 11. The metal-air all-solid secondary battery according to Item 9 or 10.   The metal-air all-solid secondary battery according to claim 9, wherein the metal of the metal electrode is iron.   The metal-air all-solid secondary battery according to any one of claims 9 to 12, wherein the metal of the metal electrode is directly formed on the surface of the first or second solid electrolyte.   The metal-air all-solid-state secondary battery according to claim 13, wherein the metal electrode has a thickness of 1 nm or more and less than 100 µm and an Fe concentration of 30 atomic% or more.   The metal-air all-solid secondary battery according to claim 13 or 14, wherein the metal of the metal electrode is directly formed on the surface of the first or second solid electrolyte by a sputtering method. A metal-air all-solid secondary battery in which an air electrode, a first solid electrolyte, and a metal electrode are provided in this order,
In the metal electrode, a metal is directly and partially formed on each particle surface of the second solid electrolyte,
The metal-air all-solid-state secondary battery according to any one of claims 10 to 15, wherein the metal electrode includes a second solid electrolyte in which a metal is formed and a conductor in a mixed state.   13. The metal-air all-solid secondary battery according to claim 10, wherein in the metal electrode, the metal is iron, the conductor is carbon, and iron is supported on the carbon.   The metal-air all-solid secondary battery according to claim 9, wherein the metal of the metal electrode is magnesium.