JP2019119627A - Method of producing sintered body of oxide electrolyte, and garnet type ion conductive oxide for use in the production method - Google Patents

Abstract

To provide a production method having excellent molding capability, for producing a sintered body of an oxide electrolyte, and a garnet type ion conductive oxide for use in the production method.SOLUTION: The production method comprises a process of preparing crystal particles of a garnet type ion conductive oxide represented by the following general formula (1), a process of preparing a flux containing lithium, a process of preparing a composite by mixing the crystal particles of a garnet type ion conductive oxide and the flux, and a process of sintering the composite by heating. General formula (1): (Li, E, H)LMO[in the general formula (1), E is at least one kind of element selected from the group consisting of Al, Ga, Fe, and Si, L is at least one kind of element selected from the group consisting of alkali earth metal and lanthanoid, and M is at least one kind of element selected from the group consisting of transition elements and typical elements belonging to Group 12 to 15 of the periodic table, which can take hexa-coordination with oxygen].SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a method for producing an oxide electrolyte sintered body, and a garnet-type ion conductive oxide used in the method for producing the same.

Garnet-type ion conductive oxides composed of at least elements of Li, La, Zr and O have attracted attention as materials of solid electrolytes used for Li ion batteries because of their high Li ion conductivity and the like.
For example, Patent Document 1 has a basic composition Li _x La _3-Y A _Y Zr _2-Z B _Z O ₁₂ (wherein the element A is selected from the group consisting of Sr, Ba, Ca, Mg and Y) One or more elements, the element B is one or more elements selected from the group consisting of Sc, Ti, V, Y, Nb, Hf, Ta, Al, Si, Ga and Ge, and X is , And when the average valence of (La _{3-YA Y} ) is a and the average valence of (Zr _2-Z B _Z ) is b, X = 24-3 × a−2 × b is satisfied, and 0 A garnet type ion conductive oxide represented by <Y ≦ 1.0, 0 <Z ≦ 1.0) is disclosed. Patent Document 1 describes that when sintering the garnet type ion conductive oxide having the above basic composition, the decrease in conductivity can be suppressed as much as possible, and the firing energy can be further reduced.
Further, Patent Document 2 discloses a garnet type ion conductive oxide in which a part of Li is replaced with H.

JP, 2013-032259, A JP 2012-096940 A

As described in Patent Document 1, the garnet type ion conductive oxide is generally used in the state of a sintered body formed by sintering crystal particles. However, the garnet-type ion conductive oxide conventionally used has a problem that the hardness is high and the formability is poor.
This indication is made in view of the said situation, Comprising: It aims at providing the manufacturing method of a highly formable oxide electrolyte sintered compact using garnet type ion conductive oxide.

The method for producing an oxide electrolyte sintered body of the present disclosure is
Preparing crystal particles of a garnet-type ion conductive oxide represented by the following general formula (1):
Preparing a flux containing lithium;
Mixing the crystal particles of the garnet ion conductive oxide with the flux to form a complex;
Heating and sintering the composite.
Formula _{(1) (Li x-3y} -z, E y, H z) L α M β O γ
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )

In the method for producing an oxide electrolyte sintered body of the present disclosure, the step of preparing crystal particles of the garnet-type ion conductive oxide represented by the general formula (1) is
Garnet-type ion conduction represented by the following general formula (2) by mixing raw materials and heating so that it may become the stoichiometry which can obtain the garnet-type ion conductive oxide represented by the following general formula (2) Obtaining crystalline oxide crystal particles,
By substituting Li in the garnet type ion conductive oxide crystal particle represented by the obtained general formula (2) with a proton, the garnet type ion conductive oxide represented by the above general formula (1) is obtained And a process may be included.
General formula (2) (Li _{x -3 y} , E _y ) L _α M _β O _γ
(In the above general formula (2),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x and y are real numbers satisfying 3 ≦ x−3 y ≦ 7 and 0 ≦ y <0.22.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )

  In the method for producing an oxide electrolyte sintered body of the present disclosure, in the general formula (1), E may be Al, and 0 ≦ y ≦ 0.13.

  In the method for producing an oxide electrolyte sintered body of the present disclosure, 0.8 ≦ z ≦ 3.4 may be in the general formula (1).

Garnet ion conductive oxide of the present disclosure, the general formula _{(1) (Li x-3y} -z, E y, H z) , characterized by being represented by L α M β O _γ.
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. ).

  In the garnet type ion conductive oxide of the present disclosure, E in the general formula (1) may be Al, and 0 ≦ y ≦ 0.13.

  The garnet type ion conductive oxide of the present disclosure may satisfy 0.8 ≦ z ≦ 3.4 in the general formula (1).

  The complex of the present disclosure is a complex of crystal particles of an oxide electrolyte and a flux containing lithium, and the crystal particles of the oxide electrolyte have a garnet-type ion conduction represented by the general formula (1). It is characterized in that it is a crystal particle of a crystalline oxide.

  According to the present disclosure, it is possible to provide a method for producing an oxide electrolyte sintered body using a garnet-type ion conductive oxide with high formability, and a garnet-type ion conductive oxide used in the production method. .

It is the schematic diagram which showed the outline | summary of the sintering process of the manufacturing method of this indication. It is a SEM image of the grain boundary triple point of the oxide electrolyte sintered compact obtained by the manufacturing method of this indication. It is a SEM image of the crystal particle of the garnet type ion conductive oxide of the composition formula Li ₇ La ₃ Zr ₂ O ₁₂ immersed in a 0.1 M HCl solution for a long time. It is a schematic diagram which shows Li site etc. in the crystal particle of garnet type ion conductive oxide. It is a graph which shows the relationship between H content ratio z in the crystal particle of garnet type ion conductive oxide, and the relative density of the obtained oxide electrolyte sintered compact. It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained in Example 1 (Z = 0.75). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained in Example 3 (Z = 0.91). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained in Example 5 (Z = 3.4). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained by the comparative example 2 (Z = 0.13). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained by the comparative example 3 (Z = 0.4).

1. Method for Producing Oxide Electrolyte Sintered Body The method for producing an oxide electrolyte sintered body according to the present disclosure is
Preparing crystal particles of a garnet-type ion conductive oxide represented by the following general formula (1):
Preparing a flux containing lithium;
Mixing the crystal particles of the garnet ion conductive oxide with the flux to form a complex;
Heating and sintering the composite.
Formula _{(1) (Li x-3y} -z, E y, H z) L α M β O γ
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )

As described above, the garnet-type ion conductive oxide represented by the composition formula of Li ₇ La ₃ Zr ₂ O ₁₂ conventionally used as a material of an oxide electrolyte sintered body has high Li ion conductivity. Although it is hard and brittle, there is a problem that the formability is low.

The present inventors have found that the Li ion in the garnet type ion conductive oxide represented by the composition formula of Li ₇ La ₃ Zr ₂ O ₁₂ is replaced with the above-mentioned general formula (1) ) (Li _{x -3 y -z} , E _y , H _z ) L _α M _β O _γ A complex of crystal particles of a garnet-type ion conductive oxide represented by _γ and a flux containing lithium is used. It has been found that, by sintering and sintering, the formability at the time of sintering can be improved without impairing the Li ion conductivity of the obtained oxide electrolyte sintered body.

  The reason why the formability at the time of sintering can be improved by using a complex of crystal particles of the garnet type ion conductive oxide represented by the above general formula (1) and a flux containing lithium is clear Although not, I guess it as follows.

Analysis of the garnet-type ion conductive oxide in the resulting oxide electrolyte sintered body in the manufacturing method of the present disclosure, the general formula was used as the raw material (1) (Li x-3y -z, E y, H _z ) It can be seen that the content ratio of Li element increases and the content ratio of protons decreases compared to the garnet type ion conductive oxide represented by L _α M _β O _γ .
Therefore, in the production method of the present disclosure, protons in crystal particles of the garnet-type ion conductive oxide represented by the above general formula (1), which is a raw material in the sintering step, and Li ions in the flux are substituted. I understand that
In the previous study, the present inventors contain crystal particles of garnet-type ion conductive oxide (in the general formula (1), in the range of 0 ≦ z) in which Li ions are substituted by a small amount of protons and lithium. It has been found that by heating a complex obtained by mixing with a flux, it is possible to join crystal particles of garnet-type ion conductive oxide with low energy (low temperature).
The reason why bonding of crystal particles of garnet-type ion conductive oxide is possible with relatively low energy will be described with reference to FIG.
The figure on the left side of FIG. 1 shows solid particles of crystalline particles of garnet type ion conductive oxide (denoted as LLZ particles in FIG. 1) in which a part of Li ions (Li ⁺ ) is replaced with hydrogen ions (H ⁺ ). It is a figure which shows the state of the "before heating" of a complex with the flux of (1).
And the figure of the center of FIG. 1 is a figure which shows the state of "the heating initial stage" of the said complex. As shown in the middle of FIG. 1, when the mixture is heated to the melting point of the flux, the combination of Li ions (Li ⁺ ) and anions (X ⁻ ) in the flux and the garnet type ion conductive oxide The bond between hydrogen ions (H ⁺ ) in the crystal grains and the other constituent elements is weakened. At this time, substitution of hydrogen ions (H ⁺ ) in crystal particles of garnet-type ion conductive oxide and Li ions (Li ⁺ ) of the flux occurs.
Finally, the figure on the right side of FIG. 1 is a view showing the “end of heating” state of the mixture. As shown in the right side of FIG. 1, Li ions (Li ⁺ ) of the flux are incorporated into the crystals of garnet-type ion conductive oxide crystal particles. The hydrogen ions (H ⁺ ) emitted from the crystal particles of garnet-type ion conductive oxide combine with anions (X ⁻ ) of the flux to form a reaction product, and garnet-type ion conductive oxide It does not remain in the crystal grains. Most of the flux used in the sintering step and the reaction product obtained by combining hydrogen ions (H ⁺ ) and anions (X ⁻ ) of the flux are evaporated by heating in the sintering step, As shown in FIG. 2, at the grain boundary triple point of the oxide electrolyte sintered body, the flux used in the sintering step, and the reaction combined with hydrogen ion (H ⁺ ) and anion (X ⁻ ) of the flux The product remains.

However, in the range of 0 ≦ z <0.75 in the general formula (1), the formability could not be improved.
Here, when the crystal particles of the garnet type ion conductive oxide of the composition formula Li ₇ La ₃ Zr ₂ O ₁₂ which does not contain protons are immersed in a 0.1 M HCl solution for a long time and the progress is observed, As shown in 3, cracks occur in the particles. In addition, the plane which the crack produced in FIG. 3 was a specific crystal plane.
When the particles of garnet type ion conductive oxide of composition formula Li ₇ La ₃ Zr ₂ O ₁₂ not containing protons are immersed in a solution containing protons, the Li ions in the garnet type ion conductive oxide particles become protons It is known to be replaced by In addition, it is known that in the garnet type ion conductive oxide of the composition formula Li ₇ La ₃ Zr ₂ O ₁₂ , the crystal structure can not be maintained when the amount of substitution of Li ions with protons exceeds a certain amount. .
For this reason, as shown in FIG. 3, the reason for cracking along a specific crystal plane in the particle is that Li ions have been replaced by protons in a specific crystal plane in excess of a certain amount. It is presumed that this is because the crystal structure can not be maintained along the crystal plane.

As in the sintering step of the production method of the present disclosure, in an environment in which protons and Li ions in the garnet-type ion conductive oxide crystal particles can be substituted, bonding of Li ions or protons with other constituent elements Is temporarily disconnected. When a load is applied to the crystal particles in such a state, it is presumed that a specific crystal plane in the particle in which exchange of Li ions and protons occurs is slipped, and plastic deformation occurs while maintaining the crystal structure.
Here, in the garnet type ion conductive oxide crystal particle represented by the general formula (1), protons exist on the particle surface in the range of 0 ≦ z <0.75, but the proton content in a specific crystal plane Since the amount is small, it is considered that the crystal face is unlikely to slip in the sintering step, and the formability can not be improved.
In contrast, garnet-type ion conductive oxide crystal particles represented by the above general formula (1) in the range of 0.75 ≦ z ≦ 3.4 used in the manufacturing method of the present disclosure have not only the surface, Since protons are also present in the specific crystal face, when protons present in the specific crystal face in the particles are replaced with Li in the flux in the sintering step, slip occurs in the crystal face. Since it becomes easy, it is estimated that moldability improves.

(1) A method of manufacturing a garnet-type ion conductive oxide crystal particles preparation process The present disclosure, the general formula _{(1) (Li x-3y} -z, E y, H z) represented by _L α M β O γ It has the process of preparing the crystal particle of garnet type ion conductive oxide.
Formula _{(1) (Li x-3y} -z, E y, H z) L α M β O γ
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )

In the production method of the present disclosure, a garnet-type ion conductive oxide represented by the above general formula (1) in which Li ion is replaced with E element ion or proton described later is used. It is possible to improve formability by substituting a specific amount of Li ions with protons.
Here, as shown in FIG. 4, in the crystal structure of the garnet-type ion conductive oxide, Li ions exist at 24 d and 96 h. In the present disclosure, a garnet-type ion conductive oxide is used in which this Li site is substituted with a specific amount of E element or proton.
In the manufacturing method of the present disclosure, the value of x-3y-z determined from the composition ratio of Li, E elements and protons at 24d and 96h sites shown in FIG. 4 is in the range of 3 ≦ x-3y-z ≦ 7. The garnet type ion conductive oxide is used. When x-3 y-z> 7, the crystal structure of the garnet-type ion conductive oxide changes from cubic to tetragonal, the symmetry of the crystal is lost, and the Li ion conductivity may decrease. . In addition, when the composition of Li in the above general formula is x-3y-z <3, the potential of the 96h site which is a unique site into which Li enters in the crystal structure of the garnet type ion conductive oxide is increased. Because Li is less likely to enter the crystal, the Li occupancy rate may decrease and the Li ion conductivity may decrease.

In the production method of the present disclosure, in the above general formula (1), an element having four coordinations having the same coordination number as Li as the element E and having an ion radius (Li: 0, 59 Å) close to Li A garnet type ion conductive oxide is used which contains at least one element selected from the group consisting of Al, Ga, Fe and Si.
In the manufacturing method of the present disclosure, a garnet-type ion conductive oxide in which y representing the substitution amount of Li ion by the element E ion is in the range of 0 ≦ y <0.22 is used. The stability of the crystal structure can be improved by setting y to 0 or more, but when y is set to 0.22 or more, the particles may become too hard to affect the formability.
Further, from the viewpoint of the balance between the stability of the crystal structure and the formability, when E in the general formula (1) is Al, it may be in the range of 0 ≦ y ≦ 0.13.

In the production method of the present disclosure, a garnet type ion conductive oxide in which z representing the substitution amount of Li ion by proton in the above general formula (1) is in the range of 0.75 ≦ z ≦ 3.4 is used. If z is in the range of 0.75 ≦ z ≦ 3.4 in the general formula (1), the formability can be improved without largely changing the crystal structure.
From the viewpoint of enhancing the formability, 0.8 ≦ z ≦ 3.4 may be satisfied, or 0.91 ≦ z ≦ 3.4.
There is no restriction | limiting in particular in the measuring method of z which shows substitution amount of Li ion by a proton in said General formula (1), A well-known method can be used.

For example, as described later, when manufacturing by substituting Li ions in a proton-free garnet-type ion conductive oxide with a proton, inductively coupled plasma is generated for the garnet-type ion conductive oxide before and after the substitution treatment. By performing (ICP) analysis, z can be calculated indirectly.
That is, in ICP analysis, the amount of protons in the garnet-type ion conductive oxide can not be directly quantified, but the amount of Li ions in the garnet-type ion conductive oxide before and after the proton substitution treatment can be quantified.
Since the amount of change in the quantitative value of Li ion before and after substitution treatment indicates substitution amount of Li ion by proton, let the value obtained by subtracting the analysis value after substitution treatment from the analysis value before substitution treatment be the value of z. Can.

  It is also possible to measure z-values directly in garnet-type ion-conductive oxide samples, for example by means of mass spectrometry (MS) and thermogravimetry (Tg) devices.

  In the production method of the present disclosure, a garnet in which at least one of alkaline earth metal and lanthanoid elements is contained as the element L in the general formula (1) in the range of 2.5 ≦ α ≦ 3.5. Type ion conductive oxide is used. In the general formula (1), when α indicating the content ratio of the element L is in the range of 2.5 ≦ α ≦ 3.5, the oxide electrolyte has high stability of the crystal structure and high ion conductivity. It is because a sintered compact is obtained. In the present disclosure, the alkaline earth metal is a concept including Ca, Sr, Ba, and Ra. From the viewpoint of obtaining a sintered body of an oxide electrolyte having higher ion conductivity, the element L may be La.

In the production method of the present disclosure, in the general formula (1), as the element M, at least one of a transition element capable of taking six coordination with oxygen and a typical element belonging to Groups 12 to 15 A garnet type ion conductive oxide is used in which the element is contained in the range of 1.5 ≦ β ≦ 2.5. In the general formula (1), when β indicating the content ratio of the element M is in the range of 1.5 ≦ β ≦ 2.5, the burning of the oxide electrolyte having high stability of the crystal structure and ion conductivity It is because a body is obtained.
As the element M, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, Al, Ga, Ge, Sn, Sb And Bi and the like.
Among the elements M, at least the element M is selected from the group consisting of Zr, Nb, and Ta from the viewpoint of obtaining a sintered body of an oxide electrolyte having higher crystal structure stability and ion conductivity. It may be a single element, or may be a combination of Zr and Nb or Ta.
When the element M is a combination of Zr and Nb or Ta, the amount of Zr in the above composition may be 1.4 to 1.75, and the amount of Nb or Ta may be 0.25 to 0.6. .

  In the production method of the present disclosure, a garnet-type ion conductive oxide is used in which γ indicating the content ratio of oxygen O is included in the range of 11 ≦ γ ≦ 13 in the general formula (1). When γ is out of the above range, the crystal structure becomes unstable. From the viewpoint of crystal structure stabilization, γ may be 12.

In the production method of the present disclosure, a garnet-type ion conductive oxide of the general formula (1), which is usually present as crystals at a normal temperature and is in the form of particles, is used.
In the production method of the present disclosure, the average particle diameter of the crystal particles of the garnet-type ion conductive oxide of the general formula (1) is not particularly limited, but may be in the range of 0.1 to 100 μm. It may be in the range of 1 to 3.0 μm.

  The average particle size of the particles in the present disclosure is calculated by a conventional method. The example of the calculation method of the average particle diameter of particle | grains is as follows. First, a transmission electron microscope (Transmission Electron Microscope; hereinafter referred to as TEM) image or scanning electron microscope (hereinafter referred to as SEM) of an appropriate magnification (for example, 50,000 to 1,000,000 times). In the image, for one particle, the particle diameter when the particle is regarded as spherical is calculated. The calculation of the particle size by such TEM observation or SEM observation is performed for 10 to 100 particles of the same type, and the average of these particles is taken as the average particle size.

In the production method of the present disclosure, in the step of preparing crystal particles of the garnet type ion conductive oxide of the general formula (1), the garnet type ion conductive oxide of the general formula (1) is a commercially available crystal particle May be used, or synthesized crystal particles may be used.
When using the synthesized crystal particle, the process of preparing the crystal particle of the garnet type ion conductive oxide represented by the said General formula (1) is the garnet type ion represented by following General formula (2) A process of obtaining crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2) by mixing and heating the raw materials so as to obtain a stoichiometric ratio at which the conductive oxide is obtained; Converting the Li in the garnet type ion conductive oxide crystal particle represented by the general formula (2) with a proton to obtain the garnet type ion conductive oxide represented by the general formula (1) You may have.
General formula (2) (Li _{x -3 y} , E _y ) L _α M _β O _γ
(In the above general formula (2),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x and y are real numbers satisfying 3 ≦ x−3 y ≦ 7 and 0 ≦ y <0.22.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )

The garnet type ion conductive oxide represented by the general formula (2) (Li _{x -3 y} , E _y ) L _α M _β O _γ is a compound represented by the general formula (1) (L _{x-3 y -z} , E _y , H _z ) It is a compound which does not contain a proton in which all the protons of the garnet type ion conductive oxide represented by L _α M _β O _γ are substituted by Li ions. The description other than the absence of a proton overlaps with the description of the garnet-type ion conductive oxide represented by the general formula (1), and thus the description is omitted here.
Examples of garnet type ion conductive oxides represented by the general formula (2) (Li _{x -3 y} , E _y ) L _α M _β O _γ include, for example, Li ₇ La ₃ Zr ₂ O ₁₂ , Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ , Li _6.5 La ₃ Zr _1.7 Nb _0.3 O ₁₂ , Li _6.8 La ₃ Zr _1.7 Nb _0.3 O ₁₂ , (Li _{6. 6 2} Al _0.2 ) La ₃ Zr _1.7 Nb _0.3 O ₁₂ , (Li _5.8 Al _0.2 ) La ₃ (Zr _1.4 Nb _0.6 ) O ₁₂ , (Li _6.1 Al) _{0.13) La 3 (Zr 1.4 Nb} 0.6) O 12, (Li 6.3 Al 0.02) La 3 (Zr 1.4 Nb 0.6) O 12, (Li 6.2 Ga _{0.2) La 3 Zr 1.7 Nb 0.3} O 12 , and the like.
How to replace the Li ion garnet-type ion-conductive oxide represented by the general formula In the production method of the present disclosure (2) the proton of the general formula (1) (Li x-3y -z, E y H _z ) L _α M _β O _γ There is no particular limitation as long as a garnet type ion conductive oxide can be obtained, but from the viewpoint of facilitating control of the substitution amount, for example, the general formula (2) The method of stirring and / or immersing the powder of the garnet-type ion conductive oxide represented by 1.) in pure water at room temperature for several minutes to 5 days may be used.
As described above, the amount of substitution of Li ions by protons can be estimated from the amount of Li ions in the garnet-type ion conductive oxide before and after the substitution treatment.

(2) Flux preparation process The manufacturing method of this indication has the process (flux preparation process) of preparing the flux containing lithium.
The flux used in the present disclosure is not particularly limited as long as it contains lithium, but it is around the temperature at which protons are released from the crystal particles of the garnet-type ion conductive oxide represented by the general formula (1). Those having a melting point are preferable, and examples thereof include LiOH (melting point: 462 ° C.), LiNO ₃ (melting point: 260 ° C.), Li ₂ SO ₄ (melting point: 859 ° C.) and the like. From the viewpoint of lowering the sintering temperature, a flux having a relatively low melting point, such as LiOH or LiNO ₃ , may be used.

(3) Step of mixing crystal particles of garnet-type ion conductive oxide with flux to form a complex In the production method of the present disclosure, garnet-type ion conductive oxide represented by the general formula (1) It has a process of mixing crystal particles and the flux containing Li to form a complex.
There is no restriction | limiting in particular in the method to mix the crystal particle of garnet type ion conductive oxide, and a flux, A well-known method is employable.
There is no particular limitation on the complex of garnet type ion conductive oxide crystal particles and flux obtained in this process, but as a complex in which garnet type ion conductive oxide crystal particles and flux are mixed uniformly. Alternatively, it may be a complex in which the surface of the garnet-type ion conductive oxide crystal particle is coated with a flux.
The mixing ratio of crystal particles of garnet type ion conductive oxide to flux is not particularly limited, but a desired oxide electrolyte sintered body can be efficiently obtained, so 50: 50 (volume%) to 95: 5 ( It may be volume%).

(4) Sintering step The manufacturing method of the present disclosure heats and sinters a composite of crystal particles of the garnet-type ion conductive oxide represented by the general formula (1) and a flux containing the Li. Process.
The sintering temperature may be equal to or higher than the melting point temperature of the flux, and promotes substitution of protons in the garnet type ion conductive oxide crystal particles represented by the general formula (1) and Li ions in the flux, From the viewpoint of improving the binding and formation between particles, it may be 350 ° C. or higher, or 400 ° C. or higher. If the crystal stability of the garnet type ion conductive oxide can be maintained, the temperature is 1000 ° C. or lower Or 850.degree. C. or less.
When a material other than the garnet ion conductive oxide and the flux is contained at the time of sintering, a temperature at which the material and the garnet ion conductive oxide do not react may be selected, and may be 650 ° C. or less It may be 550 ° C. or less.
According to the present disclosure, it is possible to obtain an oxide electrolyte sintered body having a desired shape and Li ion conductivity even when sintering is performed at a lower temperature (for example, 350 ° C.) than conventional.

The pressure applied to the composite or the sintered body in the sintering step is not particularly limited, but from the viewpoint of improving the formability and the Li ion conductivity of the oxide electrolyte sintered body, a pressure exceeding atmospheric pressure is applied. It may be heated under conditions. Although the upper limit of the pressure at the time of heating is not particularly limited, it may be, for example, 6 ton / cm ² (≒ 588 MPa) or less.
The atmosphere in the sintering step is not particularly limited.

Sintering in the sintering step may be performed by hot pressing.
Here, hot pressing is a method of performing heat treatment while uniaxially pressing in a furnace in which the atmosphere is adjusted.
By hot pressing, crystal particles of the garnet-type ion conductive oxide are plastically deformed, so that the formability is improved, and the obtained oxide electrolyte sintered body is densified to improve the density. As a result, since the bonding between the oxide electrolyte sintered particles is improved, the Li ion conductivity is improved.
The pressure of hot pressing may be 1 to 6 ton / cm ² (≒ 98 to 588 MPa). Moreover, the processing time of the hot press processing may be 1 to 600 minutes.

2. Oxide Electrolyte Sintered Body Obtained by the Manufacturing Method of the Present Disclosure The oxide electrolyte sintered body of the present disclosure has grain boundaries between crystal grains of garnet-type ion conductive oxide, and the crystal grains are sintered, It also has high Li ion conductivity at this grain boundary. As described above, since the manufacturing method of the present disclosure is excellent in moldability, the shape of the obtained oxide electrolyte sintered body can be freely designed, and therefore the oxide electrolyte sintered body obtained by the manufacturing method of the present disclosure The body can be used in a wide range of applications as an electrode material and an electrolyte material.

3. Garnet-Type Ion-Conductive Oxide of General Formula (1) The garnet-type ion-conductive oxide for producing an oxide electrolyte sintered body according to the present disclosure has the general formula (1) (Li _{x -3y-z} , E _y , H _z ) is represented by L _α M _β O _γ .
The garnet type ion conductive oxide of the general formula (1) of the present disclosure improves formability at the time of sintering by using it with a flux containing Li as a raw material for obtaining a sintered body of an oxide electrolyte. can do. With regard to the garnet-type ion conductive oxide of the general formula (1), Since the method for producing the oxide electrolyte sintered body has been described in detail, the description is omitted here.
The garnet type ion conductive oxide of the general formula (1) of the present disclosure usually exists as a crystal at normal temperature, and when used in the method for producing a sintered body of the oxide electrolyte of the present disclosure, the crystal May be in the form of particles.
The average particle size of the crystal particles of the garnet-type ion conductive oxide of the general formula (1) of the present disclosure is not particularly limited, but may be in the range of 0.1 to 100 μm, 0.1 to 3 It may be in the range of 0.1 μm.

  The garnet type ion conductive oxide of the present disclosure can be used as an electrode material of various batteries, an electrolyte material, and the like, and can be used as an electrode material of an all-solid battery, an electrolyte material, and the like.

4. Complex of Crystal Particle of Oxide Electrolyte and Flux Containing Lithium A complex of crystal particle of oxide electrolyte and a flux containing lithium, which is used for producing the oxide electrolyte sintered body of the present disclosure, is the above-mentioned general It is a complex of the crystal particle of garnet type ion conductive oxide of a formula (1), and the flux containing Li.
The composite of the present disclosure is not particularly limited as long as it contains crystal particles of the garnet-type ion conductive oxide represented by the general formula (1) and a flux containing Li, but the garnet-type It may be a complex in which crystal particles of the ion conductive oxide and the flux are uniformly mixed, or it may be a flux in which the surface of the crystal particle of the garnet type ion conductive oxide is coated with the flux.
About the garnet type ion conductive oxide of said General formula (1), and the flux containing said Li, 1. Since the method for producing the oxide electrolyte sintered body has been described in detail, the description is omitted here.
The mixing ratio of crystal particles of garnet type ion conductive oxide to flux is not particularly limited either, but a desired oxide electrolyte sintered body can be efficiently obtained, so 50: 50 (volume%) to 95: 5 (volume %).

(1) Production of sintered body of oxide electrolyte (Example 1)
[Garnet-type ion conductive oxide crystal particle preparation process]
LiOH (H ₂ O) (Sigma-Aldrich) as a starting material so as to obtain garnet-type ion conductive oxide crystal particles having a composition of Li _6.75 La ₃ Zr _1.4 Nb _0.6 O ₁₂ ), La (OH) ₃ (manufactured by High Purity Chemical Laboratory Co., Ltd.), ZrO ₂ (manufactured by High Purity Chemical Laboratory Co., Ltd.), Nb ₂ O ₅ (manufactured by High Purity Chemical Laboratory Co., Ltd.) Weighed and mixed each raw material to obtain a mixture.
The mixture is heated from room temperature to 950 ° C. over 8 hours with flux (NaCl) such that the mixture melted in the flux is 2.5 mol%, and held at 950 ° C. for 20 hours, the composition is Li Garnet-type ion conductive oxide crystal particles of _6.75 La ₃ Zr _1.4 Nb _0.6 O ₁₂ were obtained. The number average particle diameter of the obtained crystal particles was 2.8 μm.
The garnet ion ion of Example 1 is subjected to substitution of Li ion and proton by immersing 2.0 g of garnet ion conductive oxide crystal particles obtained as described above in 100 mL of pure water at room temperature for 60 minutes. Conductive oxide crystal particles were obtained.
As a result of performing ICP analysis on crystal particles before and after hydrogen ion partial substitution, the Li ion content ratio was 6.75 before hydrogen ion partial substitution was 6.00 before hydrogen ion partial substitution, so garnet The amount of Li replaced with H in the composition of the type ion conductive oxide was considered to be 0.75.
Thus, the garnet type ion conductive oxide particles of Example 1 _was found to have a composition of _{Li 6.0 H 0.75 La 3 Zr 1.4} Nb 0.6 O 12.

[Flux preparation process]
LiNO ₃ having a melting point of 260 ° C. was used as a flux.
[Mixing process of garnet type ion conductive oxide crystal particles and flux]
Garnet-type ion conduction of Example 1 by weighing the garnet-type ion conductive oxide crystal particles of Example 1 and LiNO ₃ powder so as to have a volume ratio of 75:25 and then mixing them in a dry mortar. A complex of crystalline oxide crystal particles and flux was obtained.

[Sintering process]
A complex of garnet-type ion conductive oxide crystal particles of Example 1 and a flux is compressed at room temperature (load: 1 ton / cm ² (≒ 98 MPa)), and the obtained green compact is hot-pressed ( A sintered body of the oxide electrolyte of Example 1 was obtained at 400 ° C. and a load of 3.2 ton / cm ² (≒ 313 MPa) for 4 hours.

(Example 2)
Composite of garnet-type ion conductive oxide crystal particles and flux of Example 2 and Example by the same method as Example 1 except that garnet-type ion conductive oxide particles were prepared as follows: A sintered body of the oxide electrolyte of 2 was obtained.
In the same manner as in Example 1, the number average particle diameter is 2.8 .mu.m, the composition to obtain a garnet-type ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
The garnet ion conductive oxide of Example 2 was subjected to partial substitution of hydrogen ions and Li ions by immersing 2.0 g of the obtained garnet ion conductive oxide crystal particles in 200 mL of pure water at room temperature for 60 minutes. Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles of Example 2 were Li _5.6 H _0.80 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(Example 3)
Composite of garnet-type ion conductive oxide crystal particles and flux of Example 3 and Example by the same method as Example 1 except that garnet-type ion conductive oxide particles were prepared as follows: A sintered body of the oxide electrolyte of 3 was obtained.
In the same manner as in Example 1, the number average particle diameter is 2.8 .mu.m, the composition to obtain a garnet-type ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
The garnet ion conductive oxide of Example 3 was subjected to partial substitution of hydrogen ions and Li ions by immersing 2.0 g of the obtained garnet ion conductive oxide crystal particles in 300 mL of pure water at room temperature for 60 minutes. Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles in Example 3 were Li _5.48 H _0.91 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(Example 4)
Composite of garnet type ion conductive oxide crystal particle and flux of Example 4 and Example by the same method as Example 1 except that garnet type ion conductive oxide particles were prepared as follows. A sintered body of 4 was obtained.
In the same manner as in Example 1, the number average particle diameter is 2.8 .mu.m, the composition to obtain a garnet-type ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
The garnet ion conductive oxide of Example 4 was subjected to partial substitution of hydrogen ions and Li ions by immersing 2.0 g of the obtained garnet ion conductive oxide crystal particles in 400 mL of pure water at room temperature for 60 minutes. Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles of Example 4 were Li _4.6 H _1.8 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(Example 5)
Composite of garnet-type ion conductive oxide crystal particles and flux of Example 5 and Example by the same method as Example 1 except that garnet-type ion conductive oxide particles were prepared as follows: A sintered body of the oxide electrolyte of 5 was obtained.
In the same manner as in Example 1, the number average particle size of 2.8 .mu.m, a composition was obtained garnet ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
The garnet ion conductive oxide of Example 5 was subjected to partial replacement of hydrogen ions and Li ions by immersing 2.0 g of the obtained garnet ion conductive oxide crystal particles in 500 mL of pure water at room temperature for 48 hours. Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles of Example 5 were Li _3.0 H _3.4 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(Comparative example 1)
Composite of garnet-type ion conductive oxide crystal particles and flux of Comparative Example 1 and Comparative Example in the same manner as Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. A sintered body of the oxide electrolyte of 1 was obtained.
The composition in the same manner as in Example 1 to obtain a garnet-type ion conductive oxide crystal grains of _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12. The obtained garnet-type ion conductive oxide crystal particles were used as the garnet-type ion conductive oxide crystal particles of Comparative Example 1 without hydrogen substitution.

(Comparative example 2)
Composite of garnet-type ion conductive oxide crystal particles and flux of Comparative Example 2 and Comparative Example in the same manner as Example 1 except that garnet-type ion conductive oxide particles were prepared as follows: A sintered body of the oxide electrolyte of 2 was obtained.
In the same manner as in Example 1, the number average particle diameter is 2.8 .mu.m, the composition to obtain a garnet-type ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
2.0 g of the obtained garnet-type ion conductive oxide crystal particles are immersed in 50 mL of pure water at room temperature for 30 minutes to perform partial substitution of hydrogen ions and Li ions, and garnet-type ion conductive oxidation of Comparative Example 2 Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles of Comparative Example 2 were Li _6.27 H _0.13 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(Comparative example 3)
Composite of garnet-type ion conductive oxide crystal particles and flux of Comparative Example 3 and Comparative Example in the same manner as in Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. A sintered body of the oxide electrolyte of 3 was obtained.
In the same manner as in Example 1, the number average particle size of 2.8 .mu.m, a composition was obtained garnet ion conductive oxide particles are _{Li 6.4 La 3 Zr 1.4 Nb 0.6} O 12.
2.0 g of the obtained garnet-type ion conductive oxide crystal particles are immersed in 100 mL of pure water at room temperature for 60 minutes to perform partial substitution of hydrogen ions and Li ions, and garnet-type ion conductive oxidation of Comparative Example 3 Crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial replacement of hydrogen ions in the same manner as in Example 1, the garnet-type ion conductive oxide particles of Comparative Example 3 were Li _6.0 H _0.4 La ₃ Zr _1.4 it has been found that having a composition of nb _0.6 O _12.

(2) Evaluation of Sintered Body of Oxide Electrolyte (2-1) Measurement of Relative Density The density of the sintered body of the oxide electrolyte of Examples 1 to 5 and Comparative Examples 1 to 3 was measured, and a general garnet The relative density was calculated when the true density of oxide, 5.10 g / cm ^3, was 100%.
As the relative density is higher, the oxide electrolyte is more likely to be plastically deformed and it can be evaluated that the formability is higher.
(2-2) Electron Microscope Observation SEM observation was performed with respect to the sintered compact surface of the oxide electrolyte of Examples 1-5 and Comparative Examples 1-3.
In SEM observation, the degree of plastic deformation due to the shape of particles was evaluated.
(2-3) X-ray crystal diffraction (XRD)
X-ray crystal diffraction was performed on the sintered bodies of the oxide electrolytes of Examples 1 to 5 and Comparative Examples 1 to 3. The crystallinity was evaluated by X-ray crystal diffraction.

Table 1 summarizes the characteristics of garnet-type oxide electrolyte crystal particles used as raw materials and the evaluation results of the sintered body of the oxide electrolyte. Further, FIG. 5 shows that H in the garnet-type oxide electrolyte crystal particles represented by the general formula (1) (Li _{x -3 y -z} , E _y , H _z ) L _α M _β O _γ used as the raw material The relation between the content ratio z and the relative density of the obtained sintered body of the oxide electrolyte is shown.

As shown in Table 1 and Figure _5, does not contain _{(Li x-3y-z,} E y, H z) L α M β O of the garnet-type oxide electrolyte crystal grains represented by the _gamma, H The sintered body of Comparative Example 1 using the garnet-type oxide electrolyte crystal particles of Comparative Example 1 as a raw material had a relative density as low as 70%. In addition, Comparative Example 2 using garnet-type oxide electrolyte crystal particles having a content ratio z of H of 0.13 and Comparative Example 3 using garnet-type oxide electrolyte crystal particles having az of 0.4. The sintered body also had a low relative density of less than 80%. As shown in FIGS. 9 and 10, SEM images of the press surfaces of the sintered bodies of Comparative Example 2 and Comparative Example 3 show that the garnet-type oxide electrolyte crystal particles are hardly deformed and the voids are large.
_Thus, in _{(Li x-3y-z,} E y, H z) L α M β O garnet-type oxide electrolyte crystal grains represented by the _gamma, the z is 0.4 or less, clear that poor moldability It became.
In contrast, as shown in Table 1 and Figure _5, out of _{(Li x-3y-z,} E y, H z) L α M β O γ represented by garnet-type oxide electrolyte crystal grains, the H The sintered bodies of Examples 1 to 5 using garnet-type oxide electrolyte crystal particles having a content ratio of 0.75 ≦ z ≦ 3.4 had a high relative density of 85% or more. As shown in FIGS. 6-8, SEM images of the press surfaces of the sintered bodies of Examples 1-5 show that the garnet-type oxide electrolyte crystal particles are deformed moderately and the gaps are narrow. In addition, the crystal structure was also maintained.
As mentioned above, the process of preparing the crystal particle of the garnet type ion conductive oxide represented by General formula (1), the process of preparing the flux containing lithium, the crystal particle of the said garnet type ion conductive oxide The method for producing an oxide electrolyte sintered body according to the present disclosure, which comprises the steps of: mixing the above and the flux to form a composite; and heating and sintering the composite, the formability is excellent. It became clear.

Claims (8)

A method of producing an oxide electrolyte sintered body, comprising
Preparing crystal particles of a garnet-type ion conductive oxide represented by the following general formula (1):
Preparing a flux containing lithium;
Mixing the crystal particles of the garnet ion conductive oxide with the flux to form a complex;
And heating the complex to sinter the composite.
Formula _{(1) (Li x-3y} -z, E y, H z) L α M β O γ
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. ) The process of preparing the crystal particle of the garnet type ion conductive oxide represented by the said General formula (1),
Garnet-type ion conduction represented by the following general formula (2) by mixing raw materials and heating so that it may become the stoichiometry which can obtain the garnet-type ion conductive oxide represented by the following general formula (2) Obtaining crystalline oxide crystal particles,
By substituting Li in the garnet type ion conductive oxide crystal particle represented by the obtained general formula (2) with a proton, the garnet type ion conductive oxide represented by the above general formula (1) is obtained A process for producing an oxide electrolyte sintered body according to claim 1, comprising the steps of:
General formula (2) (Li _{x -3 y} , E _y ) L _α M _β O _γ
(In the above general formula (2),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x and y are real numbers satisfying 3 ≦ x−3 y ≦ 7 and 0 ≦ y <0.22.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )   The method for producing an oxide electrolyte sintered body according to claim 1 or 2, wherein in the general formula (1), E is Al, and 0 ≦ y ≦ 0.13.   The manufacturing method of the oxide electrolyte sintered compact of Claim 1 or 3 in 0.8 <= z <= 3.4 in said General formula (1). Formula _{(1) (Li x-3y} -z, E y, H z) L α M β O garnet characterized by being represented by _γ ion conductive oxide.
(In the above general formula (1),
E represents at least one element selected from the group consisting of Al, Ga, Fe and Si.
L represents at least one element selected from the group consisting of alkaline earth metals and lanthanoid elements.
M represents at least one element selected from the group consisting of a transition element capable of having six coordination with oxygen and a typical element belonging to Groups 12 to 15.
x, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, and 0.75 ≦ z ≦ 3.4.
α, β, and γ are real numbers within the range of 2.5 ≦ α ≦ 3.5, 1.5 ≦ β ≦ 2.5, and 11 ≦ γ ≦ 13, respectively. )   The garnet type ion conductive oxide according to claim 5, wherein in the general formula (1), E is Al, and 0 ≦ y ≦ 0.13.   The garnet type ion conductive oxide according to claim 5 or 6, wherein 0.8 ≦ z 中 3.4 in the general formula (1). A complex of oxide electrolyte crystal particles and a lithium-containing flux,
The crystal particle of the said oxide electrolyte is a crystal particle of the garnet type ion conductive oxide of Claim 5 thru | or 7, The composite characterized by the above-mentioned.