JP2019121462A - Method for manufacturing electrode active substance coated with oxide electrolyte sintered body, electrode active substance coated with oxide electrolyte sintered body, and sulfide solid battery - Google Patents

Abstract

A method for producing an electrode active material coated with a sintered oxide electrolyte using crystal particles of garnet ion conductive oxide, and oxide containing crystal particles of garnet ion conductive oxide Provision of an electrode active material coated with an electrolyte sintered body.
A method of producing an electrode active material coated with an oxide electrolyte sintered body includes the steps of preparing crystal particles of garnet type ion conductive oxide, preparing a lithium-containing flux, and electrode A step of preparing an active material, a step of mixing crystal particles of garnet type ion conductive oxide, a flux and an electrode active material, a step of heating and sintering the mixture at a temperature of 650 ° C. or less, And.
[Selected figure] Figure 5

Description

  The present disclosure relates to a method for producing an electrode active material coated with an oxide electrolyte sintered body, an electrode active material coated with an oxide electrolyte sintered body, and a sulfide solid battery.

In the case of a Li-ion battery, there is a case that the combination of materials used causes a problem that the electrode active material reacts with the electrolyte material which transfers Li ions. Therefore, for the purpose of suppressing the reaction between the electrode active material and the electrolyte material, studies have been conducted to cover the electrode active material with a chemically stable Li ion conductive solid electrolyte.
For example, Patent Document 1 describes perovskite-type oxide-based solid electrolytes, garnet-type oxide-based solid electrolytes, Li ₁₄ ZnGe ₄ O ₁₆ , Li ₃ PO _4-x N _x (0 ≦ x ≦ 0.5). Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃ (M is Ti, Ge, Ti and Ge, 0 ≦ x ≦ 0.5), and at least one selected from the group consisting of titanium oxide-based solid electrolytes There have been proposed positive electrode active material particles whose surface is covered with an oxide-based solid electrolyte layer having a thickness of 0.001 μm to 0.5 μm which contains one kind. In addition, in the Example of patent document 1, there is no description regarding the positive electrode active material particle coat | covered with the oxide type solid electrolyte of a garnet type.

JP, 2016-164888, A

  Among the materials described as oxide electrolytes for coating electrode active materials in Patent Document 1, garnet-type ion conductive oxides have high Li ion conductivity, and accordingly, increase the thickness of the coating layer. It is preferable because the effect of suppressing the reaction between the electrode active material and the electrolyte is high. Here, in order to coat the electrode active material with a garnet-type ion conductive oxide, it is necessary to sinter crystal particles on the surface of the active material to obtain a covering layer.

However, in the crystal particles of garnet type ion conductive oxide that has been used conventionally, the temperature at which the particles sinter and the temperature at which the particles are deformed and formable are high, and the garnet type ion conductive oxide and the electrode active The electrode active material could not be coated with the garnet-type ion conductive oxide in a temperature range in which the substance does not react chemically.
The present disclosure has been made in view of the above circumstances, and is directed to a method of producing an electrode active material coated with an oxide electrolyte sintered body using crystal particles of garnet-type ion conductive oxide, garnet-type ion conductivity An electrode active material coated with an oxide electrolyte sintered body containing oxide crystal particles, and an electrode active material coated with an oxide electrolyte sintered body containing crystal particles of garnet type ion conductive oxide It is an object of the present invention to provide a sulfide solid battery having the

A method of producing an electrode active material coated with the oxide electrolyte sintered body of the present disclosure is
A method for producing an electrode active material coated with 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;
Preparing an electrode active material;
Mixing the crystal particles of the garnet ion conductive oxide, the flux, and the electrode active material;
And sintering the mixture obtained in the previous step at a temperature of 650 ° C. or lower.
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 electrode active material of the present disclosure is
An electrode active material coated with an oxide electrolyte sintered body,
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
The number average particle diameter of the crystal particles is 3 μm or less,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb It is characterized in that it is coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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 electrode active material of the present disclosure is
An electrode active material coated with an oxide electrolyte sintered body,
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
A lithium-containing flux exists at the triple point of grain boundaries between the crystal grains,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb It is characterized in that it is coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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 sulfide solid battery of the present disclosure is
A sulfide solid battery comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte layer disposed between the positive electrode and the negative electrode,
The positive electrode or the negative electrode includes an electrode active material coated with the oxide electrolyte sintered body.

  According to the present disclosure, a method for producing an electrode active material coated with an oxide electrolyte sintered body using crystal particles of garnet type ion conductive oxide, oxidation containing crystal particles of garnet type ion conductive oxide A sulfide solid battery having an electrode active material coated with a substance electrolyte sintered body, and an electrode active material coated with an oxide electrolyte sintered body containing crystal particles of garnet type ion conductive oxide be able to.

It is a schematic diagram of the electrode active material covered with the oxide electrolyte sintered compact. 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 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 schematic diagram which shows an example of the manufacturing method of this indication. It is a SEM image of the grain boundary triple point of the oxide electrolyte sintered compact which coats the electrode active material of this indication. 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 by the reference experiment example 1 (Z = 0.75). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained by the reference experiment example 3 (Z = 0.91). It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained by the reference experiment example 5 (Z = 3.4). It is a SEM observation image of the cross section of the electrode active material covered with the oxide electrolyte sintered compact obtained in Example 1. It is a SEM observation image of the oxide electrolyte sintered compact coating layer cross section of the electrode active material covered with the oxide electrolyte sintered compact obtained in Example 1. FIG. It is a SEM observation image of the press surface of the oxide electrolyte sintered compact obtained by the reference 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 reference comparative example 3 (Z = 0.4). It is a SEM observation image of the oxide electrolyte sintered compact coating layer cross section of the electrode active material covered with the oxide electrolyte sintered compact obtained by the comparative example 1. FIG.

1. A method for producing an electrode active material coated with an oxide electrolyte sintered body A method for producing an electrode active material coated with an oxide electrolyte sintered body according to the present disclosure
Preparing crystal particles of a garnet-type ion conductive oxide represented by the following general formula (1):
Preparing a flux containing lithium;
Preparing an electrode active material;
Mixing the crystal particles of the garnet ion conductive oxide, the flux, and the electrode active material;
And sintering the mixture obtained in the previous step at a temperature of 650 ° C. or lower.
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. )

When the electrode active material is coated with an oxide electrolyte sintered body for the purpose of suppressing the reaction between the electrode active material and the electrolyte, the thickness of the coating layer is important.
FIG. 1A shows a schematic view of an electrode active material having a thick covering layer, and FIG. 1B shows a schematic view of an electrode active material having a thin covering layer.
As shown in FIG. 1 (B), when the covering layer is thin, it is difficult to control and confirm the thickness, and when there is a portion which is not covered at all, the distance between the electrode active material and the electrolyte material is close Therefore, the effect of suppressing the reaction between the electrode active material and the electrolyte material is low.
On the other hand, when the covering layer is thick as shown in FIG. 1 (A), the thickness can be easily managed and confirmed, and even if there is a portion not covered, the electrode active material and the electrolyte material Because the distance between the two is difficult to contact with each other, the effect of suppressing the reaction between the electrode active material and the electrolyte material is high.

Table 1 shows the relationship between the thickness of the coating layer and the Li ion transfer resistance R of the coating layer calculated from the Li ion resistivity of the material. The Li ion transfer resistance R is a value obtained by the following formula 2.
Formula 2: Li ion transfer resistance of the coating layer R = Li ion resistivity of the coating layer material (Ω cm) × coating layer thickness (cm) / area (cm ² )
From Table 1, when the allowable Li ion transfer resistance R in the coating layer is the same, the thickness of the coating layer should be thicker as the Li ion resistivity (Ω cm) of the material itself coating the electrode active material is lower. It can be seen that

Garnet-type ion conductive oxides, which have conventionally been used as a material for oxide electrolyte sintered bodies, have the property of high Li ion conductivity (low Li ion resistivity), and therefore a thick covering layer Therefore, it has been strongly desired to apply as a material for coating an electrode active material.
However, as described above, since the heating temperature required for sintering or forming is high, the active material is reacted with the garnet-type ion conductive oxide during the sintering to deteriorate the active material. And the problem that the function as an electrolyte is lost, or a garnet type ion conductive oxide particle is cracked during sintering to obtain an electrode active material with a high coverage to the extent that the reaction between the electrode active material and the electrolyte is suppressed. There was a problem that I could not do it.

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-3y-z} , E y, and crystal grains of a garnet-type ion conductive oxide represented by _{H z) L α M β O} γ, by using a mixture of a flux containing lithium Sintering below the temperature at which the electrode active material and the garnet type ion conductive oxide react, and the formability at the time of sintering can be improved, and crystal particles of the garnet type ion conductive oxide can be obtained. It has been found that an electrode active material coated with the contained oxide electrolyte sintered body can be obtained.

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

When the garnet type ion conductive oxide of the said General formula (2) in the oxide electrolyte sintered compact which coat | covers the electrode active material obtained by the manufacturing method of this indication is analyzed, said said General formula (1) used as a raw material _{) (Li x-3y-z} , E y, than _H z) L _alpha garnet represented by M _beta O _gamma ion conductive oxide, the content ratio of Li element is increased, the content ratio of the proton Is decreasing.
From this, in the production method of the present disclosure, protons in crystal particles of the garnet-type ion conductive oxide represented by the general formula (1), which is a raw material, are substituted in the sintering step, and Li ions in the flux are substituted. Know that
First, the reason why bonding of crystal particles of garnet-type ion conductive oxide is possible at low temperature in the manufacturing method of the present disclosure will be described with reference to FIG.
The figure on the left side of FIG. 2 shows crystal particles of garnet type ion conductive oxide (denoted as LLZ particles in FIG. 2) 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. 2 is a figure which shows the state of "the heating initial stage" of the said complex. As shown in the center of FIG. 2, 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 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. 2 is a view showing the “end of heating” state of the mixture. As shown in the right side of FIG. 2, 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.

Next, the reason why the formability can be improved in the manufacturing method of the present disclosure will be described.
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.
On the other hand, 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 are not only surfaces, Since protons are also present in the specific crystal plane mentioned above, when protons present in a specific crystal plane in the particle are re-replaced with Li in the flux in the sintering step, slip occurs in the crystal plane. It is presumed that the formability is improved because it tends to occur.

(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 oxide solid electrolyte represented by the above general formula (1) in which Li ions are substituted by E element ions or protons described later is used. By substituting a specific amount of Li ions with protons, it is possible to sinter at low temperature and improve formability.
Here, as shown in FIG. 4, in the crystal structure of the garnet oxide solid electrolyte, Li ions exist at 24 d and 96 h. In the present disclosure, a garnet oxide solid electrolyte in which this Li site is substituted by a specific amount of E element or proton is used.
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. . When the composition of Li in the above general formula is x-3y-z <3, the potential of the 96h site, which is a specific site into which Li is contained in the crystal structure of the garnet oxide solid electrolyte, is increased. By making it difficult for Li to enter therein, the Li occupancy rate may decrease and the Li ion conductivity may decrease.

In the production method of the present disclosure, in the general formula (1), the element E has four coordination which is the same coordination number as Li and which has 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 manufacturing 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 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 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 element of alkaline earth metal and lanthanoid element 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 oxide electrolyte having high crystal structure stability and high ion conductivity It is because a sintered compact 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 an average value of these particle sizes is defined as an 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 step of preparing the crystal particle of the garnet type ion conductive oxide represented by the general formula (1) is a garnet type ion represented by the following general formula (A) Obtaining a crystal particle of a garnet-type ion-conductive oxide represented by the following general formula (A) 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 (A) with a proton to obtain the garnet type ion conductive oxide represented by the general formula (1) You may have.
General formula (A) (Li _{x -3 y} , E _y ) L _α M _β O _γ
(In the above general formula (A),
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. )

Formula _{(A) (Li x-3y} , E y) L α M β O garnet ion conductive oxide represented by _γ, the general formula _{(1) (Li x-3y} -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.
As the general formula _{(A) (Li x-3y} , E y) garnet ion conductive oxide represented by _L α M β O _γ, 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 .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.
In the production method of the present disclosure, the method of substituting Li ions in the garnet type ion conductive oxide represented by the general formula (A) with protons is the method represented by the general formula (1) ( _Lix-3y-z , E _The garnet-type ion conductive oxide represented by _y , H _z ) L _α M _β O _γ is not particularly limited as long as it can be obtained, but from the viewpoint of facilitating control of the substitution amount, for example, A method of stirring and / or immersing the powder of the garnet type ion conductive oxide represented by A) in pure water for several minutes to 5 days at room temperature 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) Electrode Active Material Preparation Step The production method of the present disclosure has a step of preparing an electrode active material.
The electrode active material used in the present disclosure may be a negative electrode active material or a positive electrode active material as long as it can be used for a Li-ion battery.
As a positive electrode active material, LiCoO ₂ , Li (Co, Mn, Ni) O ₂ , Li (Ni, Co, Al) O ₂ , LiFePO ₄ , LiMn ₂ O ₄ , Li (Ni _0.5 Mn _1.5 ) O ₄ and Li (CoMn) O ₄ can be mentioned. As the negative electrode active _{material, Li 4 Ti 5 O 12,} Si, Sn, include C (graphite) is.

(4) Step of Mixing Crystalline Particles of Garnet-Type Ion-Conductive Oxide, Flux, and Electrode Active Material In the production method of the present disclosure, crystals of garnet-type ion-conductive oxide represented by the above general formula (1) And a step of mixing particles, the flux containing Li, and the electrode active material.
There is no restriction | limiting in particular in the method to mix the crystal particle of garnet type ion conductive oxide, a flux, and an electrode active material, A well-known method is employable.
The order in which the garnet-type ion conductive oxide crystal particles, the flux, and the electrode active material are mixed is not particularly limited. For example, the garnet type ion conductive oxide crystal particles and the electrode active material are added to the flux solution. After that, the solution may be dried, or the electrode active material may be mixed after a crystal particle of garnet type ion conductive oxide and a flux are mixed to obtain a complex.
The complex of the garnet-type ion conductive oxide crystal particle and the flux is not particularly limited, but it may be a complex in which the garnet-type ion conductive oxide crystal particle and the flux are uniformly mixed. The surface of the crystal particle of garnet type ion conductive oxide may be a complex coated with 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%).
Further, the mixing ratio of the crystal particles of the garnet type ion conductive oxide to the electrode active material is not particularly limited either, but in order to finely coat the surface of the electrode active material, 1:99 (volume%) to 99: 1 It may be (volume%).

(5) Sintering Step The production method of the present disclosure comprises a mixture of crystal particles of the garnet-type ion conductive oxide represented by the general formula (1), a flux containing the Li, and the electrode active material. It has the process of heating and sintering at the temperature below ° C.
According to the present disclosure, by using crystal particles of the garnet-type ion conductive oxide represented by the general formula (1) and a flux containing the Li, the temperature is lower (for example, 350 ° C.) than conventional. However, the crystal particles of the garnet-type ion conductive oxide sinter together and enable plastic deformation, so that the coverage with the oxide electrolyte sintered body having high Li ion conductivity is high. An electrode active material can be obtained.
The crystal particles of the garnet-type ion conductive oxide have high chemical stability at a temperature of 650 ° C. or less, and therefore, the reaction with the electrode active material can be suppressed. Therefore, in the production method of the present disclosure, the upper limit of the sintering temperature is set to 650 ° C. or less, and from the viewpoint of further suppressing the reaction between the crystal particles of the garnet ion conductive oxide and the electrode active material, It may be.
The lower limit value of the sintering temperature may be equal to or higher than the melting point temperature of the flux, and promotes the substitution of protons in the garnet type ion conductive oxide crystal particles represented by the general formula (1) and Li ions in the flux. The temperature may be 350 ° C. or higher, or 400 ° C. or higher, from the viewpoint of improving adhesion and formation between particles.

In the sintering step, the pressure applied to the mixture or the sintered body is not particularly limited, but from the viewpoint of forming a dense oxide electrolyte sintered body covering layer, heating is performed under pressure conditions exceeding atmospheric pressure. May be 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, the crystal particles of the garnet-type ion conductive oxide are plastically deformed, so that the coverage is improved and the covering layer of the obtained oxide electrolyte sintered body is densified. As a result, since the bonding between the oxide electrolyte sintered particles is improved, the Li ion conductivity in the interface between the oxide electrolyte sintered body and the electrode active material and in the covering layer of the oxide electrolyte sintered body 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.

An example of the manufacturing method of the present disclosure will be described with reference to FIG.
First, crystal particles of a garnet-type ion conductive oxide represented by the above general formula (1) coated with a flux containing Li and an electrode active material are prepared. Next, crystalline particles of the garnet-type ion conductive oxide represented by the general formula (1) coated with flux on the surface of the active material are coated using a dry particle composite apparatus. A removable component such as carbon is added to this, and it is compacted after kneading. In this state, by heating at a temperature of 650 ° C. or less, Li ions and protons generated between crystal particles of the garnet-type ion conductive oxide represented by the above general formula (1) coated with a flux containing Li Ion exchange reaction to promote bonding and deformation of crystal particles. Finally, carbon is removed by heating in an oxygen atmosphere to obtain an electrode active material coated with an oxide electrolyte sintered body.

2. Electrode Active Material Coated with Oxide Electrolyte Sintered Body The first embodiment of the electrode active material coated with the oxide electrolyte sintered body of the present disclosure is
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
The number average particle diameter of the crystal particles is 3 μm or less,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb It is an electrode active material coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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 electrode active material coated with the oxide electrolyte sintered body of the present disclosure, the oxide electrolyte sintered body has the general formula (2) (Li _{x -3 y -z} , E _y , H _z ) L _α M _β There are grain boundaries between garnet-type solid electrolyte particles represented by O _γ .
In the garnet type ion conductive oxide of the general formula (2) in the oxide electrolyte sintered body which covers the electrode active material of the present disclosure, the general formula (1) (Li _{x -3 y-z} ) used as a raw material , E _y , H _z ) L _α M _β O _{γ As} the proton in the garnet-type ion conductive oxide represented by _γ substitutes for Li ions in the flux, the proton content ratio z decreases. The range is 0 ≦ z <3.4.
The garnet type ion conductive oxide of the general formula (1) and the general formula (2) has a proton content ratio z because no reaction occurs except that protons are substituted by Li ions in the sintering step. There is no difference in the composition other than.
In the garnet type ion conductive oxide represented by the general formula (2), the Li ion conductivity is improved as z is smaller, so the range of 0 ≦ z ≦ 0.9 may be satisfied, z = It may be 0.

In the electrode active material coated with the oxide electrolyte sintered body of the present disclosure, the oxide electrolyte sintered body is a grain boundary between crystal particles of the garnet-type ion conductive oxide represented by the general formula (2). Have. At the grain boundaries, garnet type ion conductive oxide particles are joined in a state capable of conducting Li ions.
The first aspect of the electrode active material coated with the oxide electrolyte sintered body of the present disclosure is characterized in that the number average particle diameter of the crystal particles is 3 μm or less.
In the sintered body containing the garnet type ion conductive oxide of the prior art, a temperature of 1000 ° C. or more is necessary to bond the particles. At 1000 ° C. or higher, grain growth is promoted, so the number average particle diameter can not be 3 μm or less.
On the other hand, in the electrode active material coated with the oxide electrolyte sintered body of the present disclosure, since the electrode active material is sintered at a temperature of 650 ° C. or less, the grain growth in the sintering step is slow and the number average of crystal grains It is characterized in that the particle size is small and 3 μm or less.

In a garnet-type ion-conductive oxide sintered body, ions (eg, lithium ions) conduct both grain boundaries between crystal particles of garnet-type ion-conductive oxide and within the grains of crystal particles. . Therefore, the ion conductivity of the garnet-type ion conductive oxide sintered body is determined based on the sum (total resistance) of the grain boundary resistance and the intragranular resistance. For example, if the overall resistance is high, the ion conductivity will be low, and if the overall resistance is low, the ion conductivity will be high. In addition, since it is generally considered that ions are more difficult to conduct between crystal grains than in crystal grains, the grain boundary resistance is considered to be larger than the intragranular resistance. Therefore, the lower the ratio of the grain boundary of the garnet ion conductive oxide, the higher the ion conductivity of the oxide electrolyte sintered body.
The oxide electrolyte sintered body of the present disclosure is a sintered body of a garnet type ion conductive oxide when sintered at 1000 ° C. or higher, or a sintered body of a garnet type ion conductive oxide subjected only to proton substitution. Unlike in the ion conduction in the oxide electrolyte sintered body, the ratio of grain boundary resistance is 60% or less of the total resistance (intragrain resistance + grain boundary resistance) (R _gb / (R _b + R _gb ) ≦ 0.6). is there. Thereby, the factor which inhibits lithium ion conduction is small, and the lithium ion conductivity of the oxide electrolyte sintered body is high.
Incidentally, the ratio of the grain boundary resistance Rgb for total resistance is the sum of the intragranular resistance _{R b} and grain boundary resistance _{R gb (R b + R gb} = R total) R gb / (R b + R gb ) Can be calculated by an AC impedance measurement method.

According to a second aspect of the electrode active material coated with the oxide electrolyte sintered body of the present disclosure,
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
A lithium-containing flux exists at the triple point of grain boundaries between the crystal grains,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb It is an electrode active material coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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 second aspect of the electrode active material coated with the oxide electrolyte sintered body of the present disclosure has a feature that a lithium-containing flux is present at the grain boundary triple point between crystal particles.
The electrode active material coated with the oxide electrolyte sintered body of the present disclosure differs from the oxide electrolyte sintered body when sintered at 1000 ° C. or higher, or the oxide electrolyte sintered body subjected only to proton substitution, Is hardly present at the bonding interface between the particles of the crystalline oxide electrolyte, and segregates at grain boundary triple points, which are voids between crystal particles, as shown in FIG.
The other features are the same as those of the first embodiment except that the number average particle diameter of crystal particles is not 3 μm or less, and the description thereof is omitted here.

3. Sulfide Solid Battery The sulfide solid battery of the present disclosure is a sulfide solid battery having a positive electrode, a negative electrode, and a sulfide solid electrolyte disposed between the positive electrode and the negative electrode,
The positive electrode or the negative electrode may And an electrode active material coated with the oxide electrolyte sintered body described in 4.
In the sulfide solid battery of the present disclosure, since the positive electrode active material and / or the negative electrode active material is covered with a thick and dense oxide electrolyte sintered body, the interfacial resistance is improved by the reaction between the sulfide solid electrolyte and the active material. Since it is a sintered body of particles of a garnet-type oxide solid electrolyte that suppresses rising and has high Li ion conductivity, the internal resistance is low.

1. Examination of Sintered Body of Oxide Electrolyte Used for Cover Layer First, a sample for property evaluation of the oxide electrolyte sintered body was prepared, and it was examined whether it could be applied to coating of an electrode active material.
(1) Production of sintered body of oxide electrolyte (Reference Experimental 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.
2.0 g of garnet-type ion conductive oxide crystal particles obtained as described above were immersed in 100 mL of pure water at room temperature for 60 minutes to replace Li ions with protons, and were used in Reference Experimental Example 1 Garnet-type ion 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.
From the above, it was revealed that the garnet type ion conductive oxide particles used in Reference Experimental Example 1 had 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 used in Reference Experimental Example 1 by weighing the prepared garnet-type ion conductive oxide crystal particles 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 conductive oxide crystal particles and flux was obtained.

[Sintering process]
The composite of garnet-type ion conductive oxide crystal particles obtained as described above and a flux is compressed at room temperature (load: 1 ton / cm ² (≒ 98 MPa)), and the obtained green compact is Hot pressing (400 ° C., load: 3.2 ton / cm ² (≒ 313 MPa), 4 hours) was performed to obtain a sintered body of the oxide electrolyte of Reference Experimental Example 1.

(Reference Experiment 2)
Composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Experimental Example 2 in the same manner as Reference Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. A sintered body of the body and the oxide electrolyte of Experimental Example 2 was obtained.
A garnet type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet type ion used in Reference Experimental Example 2 was subjected to partial substitution of hydrogen ion and Li ion by immersing 2.0 g of the obtained garnet type ion conductive oxide crystal particles in 200 mL of pure water at room temperature for 60 minutes. Conductive oxide crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial substitution of hydrogen ions in the same manner as in Reference Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Experimental Example 2 were Li _5.6 H _0.80 La ₃ it has been found that a composition of Zr _1.4 Nb _0.6 O _12.

(Reference Experiment Example 3)
Composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Experimental Example 3 in the same manner as in Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference experiment example 3 was obtained.
A garnet type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet type ion used in Reference Experimental Example 3 was subjected to partial substitution of hydrogen ions and Li ions by immersing 2.0 g of the garnet type ion conductive oxide crystal particles thus obtained in 300 mL of pure water at room temperature for 60 minutes. Conductive oxide crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial substitution of hydrogen ions in the same manner as in Reference Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Experimental Example 3 were Li _5.48 H _0.91 La ₃ it has been found that a composition of Zr _1.4 Nb _0.6 O _12.

(Reference Experiment 4)
Composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Experimental Example 4 in the same manner as Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference experiment example 4 was obtained.
A garnet type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet type ion used in Reference Experimental Example 4 was subjected to partial substitution of hydrogen ion and Li ion by immersing 2.0 g of the garnet type ion conductive oxide crystal particles thus obtained in 400 mL of pure water at room temperature for 60 minutes. Conductive oxide crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after the partial replacement of hydrogen ions in the same manner as in Reference Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Experimental Example 4 were Li _4.6 H _1.8 La ₃ it has been found that a composition of Zr _1.4 Nb _0.6 O _12.

(Reference Experiment 5)
Composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Experimental Example 5 in the same manner as Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference experiment example 5 was obtained.
A garnet-type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet-type ion used in Reference Experimental Example 5 was subjected to partial substitution of hydrogen ions and Li ions by immersing 2.0 g of the garnet-type ion conductive oxide crystal particles thus obtained in 500 mL of pure water at room temperature for 48 hours. Conductive oxide 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 Reference Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Experimental Example 5 were Li _3.0 H _3.4 La ₃ it has been found that a composition of Zr _1.4 Nb _0.6 O _12.

(Reference Comparative Example 1)
A composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Comparative Example 1 in the same manner as in Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference comparative example 1 was obtained.
The composition in the same manner as in Reference 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 not subjected to hydrogen substitution, and were used as garnet-type ion conductive oxide crystal particles used in Reference Comparative Example 1 as they were.

(Reference Comparative Example 2)
Composite of garnet-type ion conductive oxide crystal particles and flux used in Reference Comparative Example 2 in the same manner as in Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference comparative example 2 was obtained.
A garnet type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet-type ion used in Reference Comparative Example 2 was subjected to partial substitution of hydrogen ion and Li ion by immersing 2.0 g of the garnet-type ion conductive oxide crystal particles thus obtained in 50 mL of pure water at room temperature for 30 minutes. Conductive oxide crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial substitution of hydrogen ions in the same manner as in Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Comparative Example 2 were Li _6.27 H _0.13 La ₃ Zr It became clear that it had a composition of _1.4 Nb _0.6 O ₁₂ .

(Reference Comparative Example 3)
A composite of garnet-type ion conductive oxide crystal particles and a flux used in Reference Comparative Example 3 in the same manner as in Reference Experimental Example 1 except that garnet-type ion conductive oxide particles were prepared as follows. The sintered compact of the body and the oxide electrolyte of the reference comparative example 3 was obtained.
A garnet-type ion conductive oxide particle having a number average particle diameter of 2.8 μm and a composition of Li _6.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ was obtained by the same method as Reference Experimental Example 1. .
The garnet type ion used in Reference Comparative Example 3 was subjected to partial substitution of hydrogen ion and Li ion by immersing 2.0 g of the obtained garnet type ion conductive oxide crystal particles in 100 mL of pure water at room temperature for 60 minutes. Conductive oxide crystal particles were obtained.
When ICP analysis was performed on crystal particles before and after partial substitution of hydrogen ions in the same manner as in Reference Experimental Example 1, the garnet-type ion conductive oxide particles used in Reference Comparative Example 3 were Li _6.0 H _0.4 La ₃ it has been found that a composition of Zr _1.4 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 Reference Experimental Examples 1 to 5 and Reference Comparative Examples 1 to 3 was measured The relative density was calculated assuming that the true density of the garnet oxide was 5.10 g / cm ³ as 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 microscopic observation SEM observation was performed with respect to the sintered compact surface of the oxide electrolyte of the reference experiment examples 1-5 and the reference comparative examples 1-3.
In SEM observation, evaluation of the degree of plastic deformation by the shape of particles and calculation of the number average particle diameter of crystal particles in the oxide electrolyte sintered body were performed.
(2-3) X-ray crystal diffraction (XRD)
X-ray crystal diffraction was performed on the sintered bodies of the oxide electrolytes of Reference Experimental Examples 1 to 5 and Reference Comparative Examples 1 to 3. The crystallinity was evaluated by X-ray crystal diffraction.
(2-4) Lithium Ion Conductivity Measurement Lithium ion conductivity was measured for the oxide electrolyte sintered body manufactured in Reference Experimental Examples 1 to 5 and Reference Comparative Examples 1 to 3. The lithium ion conductivity was measured by an alternating current impedance measurement method using a potentiostat 1470 (manufactured by Solartron) and an impedance analyzer FRA 1255B (manufactured by Solartron) at a voltage amplitude of 25 mV and a measurement frequency F of 0.1 Hz to 1 MHz. The temperature was measured at 25 ° C. under normal pressure.
Further, the AC impedance measurement results, Reference Experiment Example 1-5, the oxide electrolyte sintered body manufactured in Reference Comparative Examples 1 to 3 is the sum of the intragranular resistance R _b and grain boundary resistance R _gb total resistance was calculated the ratio of the grain boundary resistance _{R gb} for _{(R b + R gb = R} total) R gb / (R b + R gb = R total).

The characteristics of the garnet-type oxide electrolyte crystal particles used in Table 2 and the evaluation results of the sintered body of the oxide electrolyte are collectively shown. Further, FIG. 7 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 2 and Figure _7, it does not contain the _{(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 Reference Comparative Example 1 using the garnet-type oxide electrolyte crystal particles of Reference Comparative Example 1 as a raw material had a relative density as low as 70%. In addition, Reference Comparative Example 2 using garnet-type oxide electrolyte crystal particles having a content ratio z of H of 0.13 and reference comparison using garnet-type oxide electrolyte crystal particles having az of 0.4. The sintered body of Example 3 also had a low relative density of less than 80%. From the SEM images of the pressed surfaces of the sintered bodies of Reference Comparative Example 2 and Reference Comparative Example 3 as shown in FIG. 13 and FIG. 14, the garnet-type oxide electrolyte crystal particles are hardly deformed and the voids are large. I understand.
_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 _{2, (Li x-3y-} z, E y, H z) of _L α M β O γ represented by garnet-type oxide electrolyte crystal grains, the content ratio of the H The sintered bodies of Reference Experimental Examples 1 to 5 using garnet type oxide electrolyte crystal particles having a range of 0.75 ≦ z ≦ 3.4 had a relative density as high as 85% or more. As shown in FIGS. 8 to 10, from the SEM images of the pressed surfaces of the sintered bodies of Reference Experimental Examples 1, 3 and 5, the garnet-type oxide electrolyte crystal particles are moderately deformed while the crystal structure is maintained, and the voids are I understand that it is narrow. In addition, in the sintered compact of the reference experiment examples 1-5, the flux existed in the grain boundary triple point which is a space | gap.
Further, in the sintered bodies of Reference Experimental Examples 1 to 5, the average crystal grain size of the garnet-type ion conductive oxide is 3 μm or less, and R _gb / (R _b + R _gb = R _total ) is 0.6 or less. It became clear that the grain boundaries were well bonded and the grain boundary resistance was sufficiently small.
As mentioned above, the process of preparing the crystal particle of the garnet type ion conductive oxide represented by said General formula (1), the process of preparing the flux containing lithium, and the crystal | crystallization of said garnet type ion conductive oxide The method of producing an oxide electrolyte sintered body comprising the steps of mixing particles and the flux to form a composite, and heating and sintering the composite, the sinterability and the formability at low temperatures It became clear that it was excellent.

2. Evaluation of electrode active material coated with oxide electrolyte sintered body It was examined whether the evaluation results of the oxide electrolyte sintered body of the above were also reflected when the electrode active material was coated.
(1) Production of electrode active material coated with oxide electrolyte sintered body (Example 1)
[Garnet-type ion conductive oxide crystal particle preparation process]
To obtain a garnet-type ion conductive oxide crystal particles having a composition in the same manner as in Reference Experiment Example _{3 Li 5.48 H 0.91 La 3 Zr} 1.4 Nb 0.6 O 12.

[Flux preparation process]
LiNO ₃ having a melting point of 260 ° C. and LiOH having a melting point of 462 ° C. were used as the flux.
LiNO ₃ was dissolved in pure water at 60 ° C. to supersaturation, and cooled to 25 ° C. The degree of saturation was lowered by cooling, and the precipitated LiNO ₃ was filtered out to obtain a saturated solution of LiNO _{3 at} 25 ° C. In the same manner, a saturated solution of LiOH at 25 ° C. was prepared. The LiNO ₃ and LiOH concentrations in the saturated solution were measured.

[Electrode active material preparation process]
An electrode active material, Li (Ni _1/3 Co _1/3 Mn _1/3 ) O ₂ was prepared.

[Mixing process of garnet type ion conductive oxide crystal particles, flux and electrode active material]
Garnet type ion conductive oxide crystal particles having the composition of LiNO ₃ saturated solution, LiOH saturated solution, and Li _5.48 H _0.91 La ₃ Zr _1.4 Nb _0.6 O ₁₂ prepared as described above Were weighed so that the molar ratio of LiNO ₃ : LiOH: garnet-type ion conductive oxide crystal particles was 0.45: 0.45: 1.00.
After weighing, the LiNO ₃ saturated solution and the LiOH saturated solution were mixed in a state of being diluted about 10 to 20 times with absolute ethanol and mixed, and the weighed garnet type ion conductive oxide crystal particles were charged.
The mixed solution thus obtained was evaporated in a dry room at 25 ° C. to obtain flux coated garnet-type ion conductive oxide crystal particles.
The garnet type ion conductive oxide crystal particles coated with the flux thus obtained and the prepared active material Li (Ni _1/3 Co _1/3 Mn _1/3 ) O ₂ in volume ratio 25 The mixture was dry mixed in a mortar so as to be: 75.

[Sintering process]
The mixed powder obtained as described above was introduced into a uniaxial former, and hot pressed (400 ° C., 4.0 tons / cm ² load, 4 hours) to perform coating on the oxide electrolyte sintered body of Example 1 An electrode active material was obtained.

(Comparative example 1)
Example 1 was repeated except that garnet type ion conductive oxide particles having a composition of Li _6.0 H _0.4 La ₃ Zr _1.4 Nb _0.6 O ₁₂ were prepared in the same manner as in Reference Comparative Example 3. An electrode active material coated with the oxide electrolyte sintered body of Comparative Example 1 was obtained by the same method.

(2) Electron Microscope Observation SEM observation was performed on the cross section of the electrode active material coated with the oxide electrolyte sintered body of Example 1 and Comparative Example 1. 11 and 12 show an SEM observation image of Example 1, and FIG. 15 shows an SEM observation image of Comparative Example 1.

As shown in FIG. 15, in the SEM observation image of Comparative Example 1, the garnet type ion conductive oxide crystal particles were cracked, and the surface of the electrode active material could not be coated.
On the other hand, as shown in FIGS. 11 and 12, in the SEM observation image of Example 1, garnet-type ion conductive oxide crystal particles are joined while appropriately deformed to cover the surface of the electrode active material. It became clear that In addition, since the sintered body of the oxide electrolyte of the covering layer had the characteristics of Reference Experimental Example 3 shown in Table 2, if the manufacturing conditions of the oxide electrolyte sintered body of Reference Experimental Examples 1 to 5 are satisfied. It is considered that an electrode active material coated with an oxide electrolyte sintered body can be obtained.

  As mentioned above, the process of preparing the crystal particle of the garnet type ion conductive oxide represented by the said General formula (1), the process of preparing the flux containing lithium, the process of preparing an electrode active material, and the said The present disclosure includes the steps of mixing crystal particles of garnet-type ion conductive oxide, the flux, and the electrode active material, and sintering the mixture at a temperature of 650 ° C. or less. It has become apparent that an electrode active material coated with an oxide electrolyte sintered body containing crystal particles of a garnet-type ion conductive oxide can be obtained by the method according to the present invention.

Claims (4)

A method for producing an electrode active material coated with 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;
Preparing an electrode active material;
Mixing the crystal particles of the garnet ion conductive oxide, the flux, and the electrode active material;
And sintering the mixture obtained in the previous step at a temperature of 650 ° C. or less. A method of producing an electrode active material coated with an oxide electrolyte sintered body, comprising the steps of:
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. ) An electrode active material coated with an oxide electrolyte sintered body,
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
The number average particle diameter of the crystal particles is 3 μm or less,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb What is claimed is: 1. An electrode active material, which is coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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. ) An electrode active material coated with an oxide electrolyte sintered body,
The oxide electrolyte sintered body has grain boundaries between crystal particles of a garnet-type ion conductive oxide represented by the following general formula (2),
A lithium-containing flux exists at the triple point of grain boundaries between the crystal grains,
Oxidation satisfying the following formula 1 when the intragranular resistance value which is the ion conduction resistance in the inside of the crystal particle is R _b and the grain boundary resistance value which is the ion conduction resistance in the grain boundary between the crystal particles is R _gb What is claimed is: 1. An electrode active material, which is coated with a substance electrolyte sintered body.
Formula 1: R _gb / (R _b + R _gb ) ≦ 0.6
Formula _{(2) (Li x-3y} -z, E y, H z) 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, y and z are real numbers satisfying 3 ≦ x−3y−z ≦ 7, 0 ≦ y <0.22, 0 ≦ 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. ) A sulfide solid battery comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte disposed between the positive electrode and the negative electrode,
The said positive electrode or a negative electrode has an electrode active material coat | covered with the oxide electrolyte sintered compact of Claim 2 or Claim 3, The sulfide solid battery characterized by the above-mentioned.