JP2022130301A - Solid electrolyte, active material layer, electrolyte layer and secondary battery - Google Patents

Abstract

To provide a solid electrolyte which can be fabricated by sintering at a low temperature, and which is high in ion conductivity, and a secondary battery having such a solid electrolyte.SOLUTION: A solid electrolyte comprises a borate containing Li, an element R selected from a group consisting of Yb, Er, Ho, Tm, La, Nd and Sm, and an element M selected from a group consisting of Zr, Ce and Sn.SELECTED DRAWING: Figure 7

Description

The present invention relates to a solid electrolyte, an active material layer comprising the electrolyte, an electrolyte layer, and a secondary battery.

An all-solid secondary battery using a solid electrolyte can improve high heat resistance. In addition, since the electrolyte does not leak or volatilize, safety can be improved. Therefore, it is possible to reduce the module cost and increase the energy density.

A sulfide-based solid electrolyte has been reported as one of such solid electrolytes. However, since sulfide-based solid electrolytes use sulfides as raw materials for their production, there has been a problem from the viewpoint of workability. Therefore, oxide-based solid electrolytes have been reported as non-sulfide-based solid electrolytes.

Li-based solid electrolytes include NASICON-type Li ₁ +xAlxTi _2-x (PO ₄ ) ₃ (LATP), perovskite-type Li _3+x La _2/3-x TiO ₃ (LLT), and garnet-type cubic Li ₇ . La ₃ Zr ₂ O ₁₂ (LLZ) has been reported. As Na-based solid electrolytes, β″ alumina type Na ₂ O. ₍ 5-7)Al ₂ O ₃ and NASICON type Na ₃ Zr ₂ Si ₂ PO ₁₂ have been reported. However, these solid electrolytes are limited in the negative electrode materials that can be used. There were problems such as the need for knots. In particular, sintering at a high temperature sometimes forms a high-resistance phase between solid electrolytes or at the interface between a solid electrolyte and an active material, which limits the improvement of ionic conductivity.

Therefore, in recent years, attempts have been made to lower the sintering temperature. Patent Document 1 discloses that the firing temperature can be lowered to about 900° C. by using a solid electrolyte containing lithium borate, such as Li _2+x C _1-x B _x O ₃ . there is

Further, according to Patent Document 2, the sintering temperature for forming a solid electrolyte can be lowered to 650 to 800° C. by mixing Li ₃ BO ₃ with an LLZ-based oxide.

JP-A-5-54712 JP 2013-37992 A

The firing temperature of the secondary battery containing the solid electrolytes disclosed in Patent Documents 1 and 2 is lowered, making it difficult to form a high resistance phase as an intermediate layer between other materials. However, the ionic conductivity σ _SE of the region occupied by the solid electrolyte may be lower than 1×10 ⁻⁷ S/cm at room temperature, and there is a demand for an oxide-based solid electrolyte with higher ionic conductivity. rice field.

An object of the present invention is to provide a solid electrolyte that can be produced by sintering at a low temperature and has high ion conductivity, and an electrolyte layer, an active material layer, and a secondary battery containing such a solid electrolyte.

A solid electrolyte according to an embodiment of the present invention contains an oxide represented by the general formula Li _6-x R _1-x M1 _x (BO ₃ ) ₃ .

However, R is at least one or two elements selected from the group containing the trivalent elements Yb, Er, Ho, and Tm, M1 is a tetravalent element, and x is a real number that satisfies 0<x<1. is. The solid electrolyte according to the embodiment of the present invention includes Li, an element R selected from the group containing Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from the group containing Zr, Ce, and Sn. and boric oxide containing.

Further, the solid electrolyte according to the embodiment of the present invention is selected from the group containing Li, the element R selected from the group containing Yb, Er, Ho, Tm, La, Nd, and Sm, and the group containing Zr, Ce, and Sn. It contains a borate containing the element M, and in X-ray diffraction analysis using CuKα rays, exhibits two diffraction peaks in the range of diffraction angles 2θ from 27.4 degrees to 29.0 degrees, and exhibits two diffraction peaks on the high angle side. The difference 2θd in the diffraction angle between the diffraction peak of and the diffraction peak on the low angle side is 0.43 degrees or more.

Furthermore, a solid electrolyte according to an embodiment of the present invention contains an oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ . However, in the formula, R contains a rare earth element selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm and is at least one or two elements, M is a tetravalent element, x is a real number that satisfies 0<x<1. A solid electrolyte comprising an oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ . However, in the formula, R is a rare earth element selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, M is an element selected from the group including Zr, Ce, and Sn, and x is a real number that satisfies 0<x<1.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the solid electrolyte with high ion conductivity which can be produced by sintering at low temperature, and a secondary battery which has the same.

4 is a diagram showing the relationship between the ionic conductivity of solid electrolytes according to Examples 1 to 12 included in the first embodiment and the value of the composition x(x1+x2) of the substitution element M. FIG. 1 shows diffraction curves of fixed electrolytes according to Examples 1 to 12. FIG. 1 shows diffraction curves of fixed electrolytes according to Examples 1 to 6. FIG. 1 shows diffraction curves of fixed electrolytes according to Examples 7 to 10. FIG. FIG. 4A is a schematic cross-sectional view of a secondary battery according to a second embodiment, and FIG. 4B is a partially enlarged view of a positive electrode and an electrolyte layer; The relationship between the ionic conductivity of the solid electrolytes according to Examples 13 to 33(a) and Examples 1 to 12(b) included in the first embodiment and the value of the composition x(x1+x2) of the substitution element M is FIG. 4 is a diagram showing; The relationship between the ionic conductivity of the solid electrolytes according to Examples 1 to 33, Comparative Examples 1 to 5, and Reference Examples 1 to 3 included in the first embodiment and the value of the composition x (x1+x2) of the substitution element M was FIG. 4 is a diagram showing;

Preferred embodiments of the present invention are described in detail below with reference to the drawings.

(First embodiment)
The solid electrolyte according to this embodiment contains an oxide represented by the general formula Li _6-x R _1-x M1 _x (BO ₃ ) ₃ .

In the formula, R is at least one or two elements selected from the group containing the trivalent elements Yb, Er, Ho and Tm, and M1 is a tetravalent element. Furthermore, in the formula, x is a real number that satisfies 0<x<1.

In the formula, when R contains at least two elements selected from the group containing the trivalent elements Yb, Er, Ho, and Tm, only a combination of elements selected from the group containing Yb, Er, Ho, and Tm Instead, these elements may be combined with other trivalent elements having ionic radii close to each other.

In other words, the solid electrolyte according to this embodiment contains an oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ .

In the formula, R is at least one or two rare earth elements selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, and M is an element selected from the group including Zr, Ce, and Sn. . Furthermore, in the formula, x is a real number that satisfies 0<x<1.

Further, in the formula, when R contains at least two elements selected from the group containing rare earth elements Yb, Er, Ho, Tm, La, Nd, and Sm, not only combinations of rare earth elements of such groups but also these may be combined with another rare earth element having an ionic radius close to that of the element.

The reason why the ion conductivity is improved in the solid electrolyte having the oxide represented by the above general formula is presumed as follows.

When some of the rare earth elements Yb, Er, Ho, Tm, La, Nd, and Sm are replaced with the element M having a tetravalence, the charge balance is adjusted so that the crystal as a whole becomes neutral. Therefore, a state in which Li ⁺ is deficient in the crystal lattice is generated. Portions lacking elements are generally called vacancies. A phenomenon in which Li ^{2 +} around the vacancies moves to the vacancies, a phenomenon generally called hopping, occurs in concert, thereby improving the ionic conductivity.

The solid electrolyte of the present embodiment contains Li, an element R selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from the group including Zr, Ce, and Sn. In other words, it is a solid electrolyte containing boric oxide.

The solid electrolyte of the present embodiment preferably has a monoclinic crystal structure.

In X-ray diffraction analysis (hereinafter referred to as XRD) using CuKα rays, the diffraction peak occurring at a diffraction angle 2θ of around 28 degrees varies depending on the composition of the solid electrolyte.

In the solid electrolyte of the present embodiment in which the oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ has Yb as R, 2θ=28.07 in XRD using CuKα rays. It is preferable to have a diffraction peak in the range of 28.20 degrees or more. More preferably, it has a peak in the range of 2θ=28.10 degrees or more and 28.20 degrees or less.

In the solid electrolyte of the present embodiment in which R is Er and the oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ , 2θ=27.94 in XRD using CuKα rays. It is preferable to have a diffraction peak in the range of 28.10 degrees or more. More preferably, it has a peak in the range of 2θ=28.0 degrees or more and 28.20 degrees or less.

In XRD using CuKα rays, the position of the diffraction peak generated near 2θ = 28 degrees can be controlled by adjusting the value of x in the above general formula and changing the element represented by M. .

M in the above general formula is a tetravalent element. Also, M is at least one element selected from the group including Zr, Ce, and Sn.

Elements with similar ionic radii are easily substituted for Yb, Er, Ho, Tm, La, Nd, and Sm, which are trivalent elements of R. Specifically, Zr ⁴⁺ , Ce ⁴⁺ , Sn ⁴⁺ , Ti ⁴⁺ , Nb ⁴⁺ , Pb ⁴⁺ , Pr ⁴⁺ and Nb ⁵⁺ are candidates. Among them, Zr ⁴⁺ and Ce ⁴⁺ are easier to be substituted.

In the above general formula, x is a real number that satisfies 0<x<1. As x corresponding to the substitution amount of the element R with the substitution element M, 0.025 or more and 0.4 or less is adopted. Furthermore, a more preferable x is 0.100 or more and 0.227 or less.

The reason why the above range of x is preferable is presumed as follows. If the value of x is less than 0.025, the substitution amount of the element R is small, so that sufficient structural change does not occur, and a path for ions is not sufficiently formed, resulting in no improvement in ionic conductivity. Also, when the value of x is larger than 0.4, the amount of the substitution element M becomes too large, and the element R in the crystal and the excess element M that does not contribute to the substitution have an effect on ion conduction rather than the substitution effect in the crystal. It will contribute as an inhibitory component.

Next, a method for producing the solid electrolyte of this embodiment will be described.

In the method for producing a solid electrolyte of the present embodiment _, elements _{Li , R} , _M , Alternatively, it has a firing step of heating these oxides in an oxygen-containing atmosphere. (Wherein, R is at least one or two elements selected from the group containing rare earth elements Yb, Er, Ho, Tm, La, Nd, and Sm, and M is a tetravalent element.)

The method for producing a solid electrolyte of the present embodiment includes a calcination step of solid-phase synthesizing the oxide represented by the above general formula by heat-treating at a temperature below the melting point of the oxide, and and densifying by heat treatment.

Hereinafter, the method for producing the solid electrolyte of the present embodiment, including the temporary sintering step and the main sintering, will be described in detail, but the production method is not limited to the following.

<Temporary firing process>
_In the calcination step, chemical reagent grade Li _{3 BO 3} , H ₃ BO _{3 ,} Yb ₂ O _{3 ,} Er ₂ O _{3 ,} Ho Raw materials such as ₂ O ₃ , Tm ₂ O ₃ , ZrO ₂ , and CeO ₂ are weighed and mixed using a predetermined stoichiometric ratio as an index. Raw materials to be weighed to give a predetermined stoichiometric ratio also include SnO ₂ , Nb ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ and Sm ₂ O ₃ . Here, R is at least one or two elements selected from the group including rare earth elements Yb, Er, Ho, Tm, La, Nd and Sm, and M is a tetravalent element.

As a device used for mixing, a mixer such as a ball mill can be used in addition to a mortar and pestle.

After the mixed powder of the raw materials is obtained by the mixing treatment, the obtained mixed powder is press-molded into pellets. Here, as the pressure molding method, a known pressure molding method such as a cold uniaxial molding method, a cold isostatic pressure molding method, or the like can be used. Conditions for pressure molding in the calcination step are not particularly limited, but the pressure can be, for example, 100 to 300 MPa.

The obtained pellets are calcined at 500° C. to 800° C. using an atmospheric calcining apparatus or the like to carry out solid-phase synthesis. The time for the calcination step is not particularly limited, but can be, for example, about 700 to 750 minutes (eg, 720 minutes).

The obtained calcined body is the oxide represented by the above general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ . A calcined powder can be obtained by pulverizing the calcined compact using a mortar, pestle, or the like.

<Baking process>
In the main firing step, the calcined body obtained in the calcining step and at least one selected from the group including the calcined body are subjected to pressure molding and main firing to obtain a dense sintered body.

Pressure molding and main firing may be performed simultaneously using discharge plasma sintering, hot pressing, or the like, or after pellets are produced by cold uniaxial molding, main firing may be performed in an air atmosphere or the like. Conditions for pressure molding in the main firing are not particularly limited, but the pressure can be, for example, 100 to 300 MPa.

The temperature for main firing is preferably 800° C. or lower, more preferably 700° C. or lower, and even more preferably 680° C. or lower.

The time for the main baking process can be appropriately changed according to the temperature of the main baking and the like, and can be, for example, about 700 to 750 minutes (eg, 720 minutes).

The cooling method in the main firing step is not particularly limited, and the product may be naturally cooled, or may be cooled more slowly than naturally cooled.

Next, the secondary battery of this embodiment will be described.

A secondary battery generally includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, an electrolyte containing a solid electrolyte disposed between the positive electrode and the negative electrode, and optionally a current collector. , have

The secondary battery of the present embodiment is a secondary battery having at least a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte, and selected from the group including the positive electrode, the negative electrode, and the electrolyte At least one selected contains the solid electrolyte of the present embodiment.

In the secondary battery of the present embodiment, the electrolyte may consist of the solid electrolyte of the present embodiment, or may contain other solid electrolytes. Other solid electrolytes are not particularly limited, and examples include Li ₃ PO ₄ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li _0.33 La _0.55 TiO ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ and the like may be included. The content of the solid electrolyte of the present embodiment in the electrolyte in the secondary battery of the present embodiment is preferably 25% by mass or more. It is more preferably 50% by mass or more, still more preferably 75% by mass or more, and particularly preferably 100% by mass.

The secondary battery of this embodiment can be obtained by a known method such as laminating a positive electrode, a solid electrolyte, and a negative electrode, followed by molding and heat treatment. Since the solid electrolyte of the present embodiment can be produced by heat treatment at a lower temperature than that of the conventional technology, the formation of a high-resistance phase caused by the reaction between the solid electrolyte and the electrode active material can be reduced. You can get the following batteries. In addition, the term “solid” as used in the specification of the present application includes those having self-sustainability to the extent that a certain shape and volume are maintained even if the posture of the object is changed, and the viscosity is less than 1×10 ⁷ cP (1 ×10 ⁴ Pa·sec).

Next, a method for measuring physical properties according to the present disclosure will be described.

・Identification of R and M If the collected sample is not a mixture with other materials, inductively coupled high-frequency plasma atomic emission spectroscopy (ICP-AES), wavelength dispersive X-ray fluorescence analysis after solution treatment of the collected sample The composition ratio of the sample can be identified by a device (WDXRF) or the like. WDXRF may be rephrased as WDX.

On the other hand, if there is a high probability that the collected sample is a mixture, an elemental mapping image such as a scanning electron microscope equipped with an X-ray photoelectron spectrometer (XPS, ESCA) or an energy dispersive X-ray fluorescence spectrometer (EDXRF) can be applied to the scanning analyzer. Henceforth, a scanning electron microscope equipped with an energy dispersive X-ray fluorescence spectrometer (EDXRF) may be abbreviated as SEM/EDX. Further, when the collected sample is highly likely to be a mixture, the crystal structure may be identified by a transmission electron microscope (TEM-ED) equipped with an electron beam diffraction function. Note that EDXRF may be rephrased as EDX.

ICP-AES and XPS are employed in order to precisely obtain the composition ratio of Li, which is a light element, and other elements with higher atomic numbers such as B, O, Zr, and rare earth elements.

If the collected sample is a mixture, selectively remove the non-analytical parts by physical removal such as dicing or ion beam processing, chemical removal such as dry etching or wet etching, or a combination thereof. pretreatment is adopted. Pretreatment may employ washing, degreasing, sectioning, pulverization, pelleting, and the like.

For standard samples, S-4800 manufactured by Hitachi High-Technologies Corporation can be used as an analyzer for SEM/EDX.

• Measurement of X-ray diffraction peak RINT-2100 manufactured by Rigaku Corporation is used for X-ray diffraction analysis of solid electrolytes.

A powder obtained by pulverizing a solid electrolyte with a mortar and pestle is subjected to X-ray diffraction analysis using characteristic X-rays of CuKα. The temperature is room temperature, the analysis range is 10 degrees to 70 degrees, the step is 0.016 degrees, and the scan speed is 0.5 steps/second.

(Second embodiment)
<Structure of secondary battery and positive electrode>
An electrolyte layer 40 having a solid electrolyte 44 according to the first embodiment and a secondary battery 100 having the electrolyte layer 40 will be described with reference to FIGS. 5(a) and 5(b).

FIG. 5(a) is a schematic cross-sectional view of a secondary battery 100 including an electrolyte layer 40 to which the solid electrolyte 44 of this embodiment is applied. The secondary battery 100 includes an electrolyte layer 40 on the side opposite to the side of the positive electrode current collector layer 10 in contact with the positive electrode active material layer 20 . The secondary battery 100 includes a negative electrode 70 on the side opposite to the side where the electrolyte layer 40 is in contact with the positive electrode active material layer 20 . The negative electrode 70 includes a negative electrode active material layer 50 on the surface of the electrolyte layer 40 opposite to the surface in contact with the positive electrode active material layer 20 . The negative electrode 70 has a negative electrode current collector layer 60 on the surface opposite to the surface where the negative electrode active material layer 50 is in contact with the electrolyte layer 40 . In other words, the secondary battery 100 includes the negative electrode 70 , the electrolyte layer 40 and the positive electrode 30 in the stacking direction 200 .

The electrolyte layer 40 to which the electrolyte 44 of the present embodiment is applied includes, as shown in FIG. is in contact with the positive electrode 30 having In the specification of the present application, a structure in which lithium ions (active material ions) are exchanged with the electrolyte layer 40 is referred to as a positive electrode. Layer 20 may be referred to as cathode 20 . In addition, since the positive electrode active material layer 20 of the present embodiment includes the electrolyte 24 in the positive electrode, it may be referred to as the composite positive electrode active material layer 20 or the composite positive electrode structure 20 .

The collector layer 10 is a conductor that conducts electrons with an external circuit (not shown) and an active material layer. The current collector layer 10 employs a laminate form of a self-supporting film of metal such as SUS or aluminum, metal foil, and a resin base.

The cathode active material layer 20 includes cathode active material layers 20a, 20b, and 20c as sublayers. The positive electrode active material layers 20a, 20b, and 20c are distinguished by the unit of lamination in the layer thickness direction 200 before the active material particles 22 and the electrolyte 24 in the positive electrode are sintered. The positive electrode active material layers 20a, 20b, and 20c may have a layer thickness distribution in the volume fraction of the active material particles 22 and the electrolyte 24 in the positive electrode, the conductive aid (not shown), the porosity, and the like. . The layer thickness direction 200 is parallel or anti-parallel to the lamination direction in which the layers are laminated, so it may be rephrased as the lamination direction 200 .

The solid electrolyte 44 according to the present embodiment is applied to the intra-positive electrode electrolyte 24 included in the composite positive electrode active material layer 20 . The positive electrode electrolyte 24 and the solid electrolyte 44 contained in the electrolyte layer 40 may have a common composition and particle size distribution, or may have different compositions and particle size distributions. may be adopted.

(negative electrode)
A known method can be applied to the method of manufacturing the negative electrode. As in the second embodiment of the present application, the manufacturing method of the positive electrode 30 of the first embodiment may be applied mutatis mutandis to manufacture the negative electrode. As with the positive electrode 30, the negative electrode may have a form in which the negative electrode active material and the solid electrolyte are mixed in the layer, or may be formed as a film of a metal such as metal Li or In--Li.

[Negative electrode active material]
Examples of negative electrode active materials include metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, and various alloy materials. Among them, metals, oxides, carbon materials, silicon, silicon compounds, tin, tin compounds, and the like are preferable from the viewpoint of capacity density. Examples of metals include metal Li and In—Li, and examples of oxides include Li ₄ Ti ₅ O ₁₂ (LTO: lithium titanate). Carbon materials include, for example, various natural graphites (graphite), coke, ungraphitized carbon, carbon fibers, spherical carbon, various artificial graphites, and amorphous carbon. Silicon compounds include, for example, silicon-containing alloys, silicon-containing inorganic compounds, silicon-containing organic compounds, solid solutions, and the like. Examples of tin compounds include SnO _b (0<b<2), SnO ₂ , SnSiO ₃ , Ni ₂ Sn ₄ and Mg ₂ Sn. Further, the negative electrode material may contain a conductive aid. Examples of conductive aids include graphite such as natural graphite and artificial graphite, and carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Conductive agents include conductive fibers such as carbon fibers, carbon nanotubes, and metal fibers, carbon fluoride, metal powders such as aluminum, conductive whiskers such as zinc oxide, conductive metal oxides such as titanium oxide, and phenylene dielectrics. organic conductive materials such as

An example of producing and evaluating the solid electrolyte of the present embodiment as a sintered body will be described. It should be noted that the present disclosure is not limited to the following examples.

[Example 1]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.975 Yb _0.975 Zr _0.025 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 1 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 2 to 4]
<Temporary firing process>
A calcined body and a calcined powder were produced in the same process as in Example 1, except that the raw materials described in Example 1 were weighed at a predetermined stoichiometric ratio so that x was the value shown in Table 1. did.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1.

[Example 5]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by Shin Nippon Denko), and CeO ₂ (manufactured by Iwatani Sangyo) It was prepared as a raw material for a solid electrolyte. In the same process as in Example 1, except that the composition after sintering was Li _5.875 Yb _0.875 Zr _0.100 Ce _0.025 (BO ₃ ) ₃ and weighed at a predetermined stoichiometric ratio. A calcined body and calcined powder were produced.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1. The heating temperature was 650° C. and the holding time was 720 minutes.

[Example 6]
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by Shin Nippon Denko), and CeO ₂ (manufactured by Iwatani Sangyo) It was prepared as a raw material for a solid electrolyte. In the same process as in Example 1, except that the composition after sintering was Li _5.850 Yb _0.850 Zr _0.100 Ce _0.050 (BO ₃ ) ₃ with a predetermined stoichiometric ratio. A calcined body and calcined powder were produced.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 7]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Er ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.975 Er _0.975 Zr _0.025 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 7 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 8 to 10]
<Temporary firing process>
A calcined body and a calcined powder were produced in the same process as in Example 7, except that the raw materials described in Example 7 were weighed at a predetermined stoichiometric ratio so that x was the value shown in Table 1. did.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1.

[Example 11]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Ho ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Ho _0.900 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 11 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 650° C. and the holding time was 720 minutes.

[Example 12]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Tm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Tm _0.900 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 12 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Comparative Example 1]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), and Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory) were prepared as raw materials for solid electrolytes. A calcined body and a calcined powder were produced in the same steps as in Example 1, except that the materials were weighed in a predetermined stoichiometric ratio so that the composition after sintering would be Li ₆ Yb(BO ₃ ) ₃ .

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1. The heating temperature was 670° C. and the holding time was 720 minutes.

[Comparative Example 2]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), and Er ₂ O ₃ (manufactured by Kojundo Chemical Laboratory) were prepared as raw materials for solid electrolytes. A calcined body and calcined powder were produced in the same steps as in Example 1, except that the materials were weighed in a predetermined stoichiometric ratio so that the composition after sintering would be Li ₆ Er(BO ₃ ) ₃ .

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1. The heating temperature was 670° C. and the holding time was 720 minutes.

[Reference example 1]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Nd ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Nd _0.900 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Reference Example 1 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 650° C. and the holding time was 720 minutes.

[Reference example 2]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Sm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), and ZrO ₂ (manufactured by Shin Nippon Denko) were prepared as raw materials for solid electrolytes. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Sm _0.900 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Reference Example 2 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 650° C. and the holding time was 720 minutes.

The sintered bodies of Examples 1 to 12, Comparative Examples 1 and 2, and Reference Examples 1 and 2 were subjected to composition analysis and X-ray diffraction peak measurement by the above methods. Also, ion conductivity was measured by the following method. A method for measuring ionic conductivity is described below. Table 1 shows the obtained evaluation results.

Measurement of ionic conductivity On the upper and lower surfaces of the flat plate-shaped sintered body obtained by main firing, a gold electrode is formed using a magnetron sputtering device MSP-10 manufactured by Vacuum Device Co., Ltd., and AC impedance is measured. It was used as a sample for performing

Potentiometer/galvanostat SI1287A and frequency response analyzer 1255B manufactured by Solartron Analytical were used for AC impedance measurement. The measurement conditions were room temperature and a frequency of 1 MHz to 0.1 Hz.

The resistance of the sintered body was calculated from a complex impedance plot obtained by impedance measurement. From the calculated resistance, the thickness of the sintered body, and the electrode area, the ionic conductivity was determined using the following formula.
Ionic conductivity (S/cm)=thickness of sintered body (cm)/(resistance of sintered body (Ω)×electrode area (cm ² ))

[Examples 13 and 14]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Tm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New manufactured by Nippon Denko) was prepared as a raw material for the solid electrolyte. The composition after _sintering is _{Li5.900Yb0.720Tm0.180Zr0.100 ( BO3} ) _{3 , Li5.800Yb0.640Tm0.160Zr0.200 ( BO3 ) 3 .} and mixed with a mortar and pestle.

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
The sintered bodies of Examples 13 and 14 were produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcining. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 15]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Tm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New Nippon Denko Co., Ltd.) and CeO ₂ (Iwatani Sangyo Co., Ltd.) were prepared as raw materials for the solid electrolyte. Weighed in a predetermined stoichiometric ratio so that the composition after sintering would be Li _5.875 Yb _0.700 Tm _0.175 Zr _0.100 Ce _0.025 (BO ₃ ) ₃ and mixed with a mortar and pestle did.

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 15 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 16 and 17]
<Temporary firing process>
Each raw material described in Example 15 was weighed at a predetermined stoichiometric ratio so that R1, R2, R1 ratio, R2 ratio, M1 component, and x = x1 + x2 were the values shown in Table 2. A calcined body and a calcined powder were produced in the same process as in Example 15.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 15.

[Example 18]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Nd ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New manufactured by Nippon Denko) was prepared as a raw material for the solid electrolyte. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Yb _0.720 Nd _0.180 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 18 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 19 to 21]
<Temporary firing process>
Each raw material described in Example 18 was weighed at a predetermined stoichiometric ratio so that R1, R2, R1 ratio, R2 ratio, M1 component, and x = x1 + x2 were the values shown in Table 2. A calcined body and a calcined powder were produced in the same process as in Example 18.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 18.

[Examples 22 and 23]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Nd ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New Nippon Denko Co., Ltd.) and CeO ₂ (Iwatani Sangyo Co., Ltd.) were prepared as raw materials for the solid electrolyte. The composition _{after sintering is Li5.875Yb0.788Nd0.088Zr0.100Ce0.025 ( BO3 ) 3 , Li5.875Yb0.700Nd0.175Zr0.100Ce .} It was weighed in a predetermined stoichiometric ratio so as to be _0.025 (BO ₃ ) ₃ . The weighed ingredients were stirred and mixed with a mortar and pestle.

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
The sintered bodies of Examples 22 and 23 were produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcining. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 24]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Er ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New manufactured by Nippon Denko) was prepared as a raw material for the solid electrolyte. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.800 Yb _0.640 Er _0.160 Zr _0.200 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 24 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 25]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Sm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (manufactured by New manufactured by Nippon Denko) was prepared as a raw material for the solid electrolyte. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Yb _0.810 Sm _0.090 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 25 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 26]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), La ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (New manufactured by Nippon Denko) was prepared as a raw material for the solid electrolyte. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.900 Yb _0.810 La _0.090 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 26 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Example 27]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), La ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (New Nippon Denko Co., Ltd.) and CeO ₂ (Iwatani Sangyo Co., Ltd.) were prepared as raw materials for the solid electrolyte. Weighed in a predetermined stoichiometric ratio so that the composition after sintering would be Li _5.88 Yb _0.788 La _0.088 Zr _0.100 Ce _0.025 (BO ₃ ) ₃ and mixed with a mortar and pestle did.

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 27 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 28 and 29]
<Temporary firing process>
Each raw material described in Example 27 was weighed at a predetermined stoichiometric ratio so that R1, R2, R1 ratio, R2 ratio, M1 component, and x = x1 + x2 were the values shown in Table 2. A calcined body and a calcined powder were produced in the same process as in Example 27.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 27.

[Comparative Examples 3-5]
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Yb ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Tm ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), Nd ₂ O ₃ (manufactured by Kojundo Chemical Laboratory) and La ₂ O ₃ (manufactured by Kojundo Chemical Laboratory) were prepared as raw materials for the solid electrolyte.

<Temporary firing process>
Each raw material described in Example 13 was weighed at a predetermined stoichiometric ratio so that R1, R2, R1 ratio, R2 ratio, M1 component, and x = x1 + x2 were the values shown in Table 2. A calcined body and calcined powder were produced in the same process as in Example 13.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 13.

[Example 30]
<Temporary firing process>
Li ₃ BO ₃ (manufactured by Toyoshima Seisakusho), H ₃ BO ₃ (manufactured by Kishida Chemical), Er ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), La ₂ O ₃ (manufactured by Kojundo Chemical Laboratory), ZrO ₂ (New Nippon Denko Co., Ltd.) and CeO ₂ (Iwatani Sangyo Co., Ltd.) were prepared as raw materials for the solid electrolyte. They were weighed in a predetermined stoichiometric ratio and mixed with a mortar and pestle so that the composition after sintering would be Li _5.9 Er _0.81 La _0.090 Zr _0.100 (BO ₃ ) ₃ .

After that, the mixed powder was cold uniaxially molded using a hydraulic press SSP-10A manufactured by Shimadzu Corporation, and heat-treated in an air atmosphere. The heating temperature was 650° C. and the holding time was 720 minutes.

The obtained calcined body was pulverized with a mortar and pestle to prepare a calcined powder.

<Baking process>
A sintered body of Example 30 was produced by molding and heat-treating the calcined powder obtained above in the same manner as in the calcination. The heating temperature was 670° C. and the holding time was 720 minutes.

[Examples 31-33]
<Temporary firing process>
A calcined body and a calcined powder were produced in the same process as in Example 1, except that the raw materials described in Example 1 were weighed at a predetermined stoichiometric ratio so that x was the value shown in Table 2. did.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1.

[Reference example 3]
<Temporary firing process>
A calcined body and a calcined powder were produced in the same process as in Example 1, except that the raw materials described in Example 1 were weighed at a predetermined stoichiometric ratio so that x was the value shown in Table 2. did.

<Baking process>
A sintered body was produced from the pre-sintered powder obtained above in the same main firing process as in Example 1.

The sintered bodies of Examples 13 to 33, Comparative Examples 3 to 5, and Reference Examples 1 to 3 were subjected to composition analysis and X-ray diffraction peak measurement in the same manner as in Example 1. Also, the ion conductivity was measured in the same manner as in Example 1.

・Result Table 1 shows the stoichiometric amount of raw materials, the heating temperature during main firing, the diffraction peak position, Indicates ionic conductivity. In addition, Table 2 shows the stoichiometric amounts of the raw materials when producing the solid electrolytes according to Examples 13 to 33, Comparative Examples 3 to 5, and Reference Example 3, the heating temperature during main firing, the diffraction peak position, and the ion conductivity. rate. Further, FIG. 6(a) shows the relationship between the ionic conductivity of the solid electrolytes according to Examples 13 to 33 and Comparative Examples 3 to 5 included in the first embodiment and the value of the composition x(x1+x2) of the substitution element M. indicates Further, FIG. 6B shows the ionic conductivity and the composition x (x1+x2 ) values. FIG. 6(b) is based on substantially the same measurement data as in FIG. 1, and is created to match the appearance of the graph with FIG. 6(a) corresponding to Examples 13-33. Further, FIG. 7 shows the ionic conductivity and the composition x (x1+x2 ) values. FIG. 7 is substantially based on the measured data of FIG. 6(a) and the measured data of FIG. 6(b).

As a result of the above composition analysis, it was confirmed that all the sintered bodies (solid electrolytes) had the raw material elements listed in Tables 1 and 2. Moreover, the sintered bodies (solid electrolytes) according to Examples 1 to 33 were solid electrolytes that could be densified at a low temperature of less than 700° C. and exhibited high ionic conductivity.

FIG. 1 shows the relationship between the ionic conductivity of the solid electrolytes according to Examples 1 to 12 included in this embodiment and the value of x in the general formula. The value of x in the general formula corresponds to the sum of x1 and x2 shown in Table 1.

FIG. 2 shows diffraction curves in the range of 2θ=10° to 40° obtained by XRD. Examples 1 to 6 have a crystal structure of Li ₆ Yb(BO ₃ ) ₃ , Examples 7 to 10 have a crystal structure of Li ₆ Er(BO ₃ ) ₃ , and Example 11 have a crystal structure of Li ₆ Ho(BO ₃ ). ₃ and Example 12 have a monoclinic crystal structure of Li ₆ Tm(BO ₃ ) ₃ . Similarly, it was confirmed from the XRD measurement that the crystal structures of Examples 13 to 33 were monoclinic crystal structures.

FIG. 3 and FIG. 4 show diffraction curves in the range of 2θ=27 degrees or more and 29 degrees or less obtained by XRD. It can be seen that the peak positions near 2θ=28.1 degrees and 28.5 degrees in Examples 1 to 6 are shifted to the higher angle side than the peak position in Comparative Example 1. Also, the peak positions near 2θ=28.0 degrees and 28.4 degrees in Examples 7 to 10 are shifted to the higher angle side than the peak positions in Comparative Example 2. These are changes in the X-ray diffraction profile corresponding to changes in the crystal structure caused by at least one element selected from the group containing M substituting at least part of the rare earth elements Yb and Er. I believe. It was confirmed by the same measurement that the peak positions of Examples 13 to 33 were shifted to the higher angle side than the peak position when x was 0. Similarly, at least one element selected from the group containing M is a change in the X-ray diffraction profile corresponding to a change in the crystal structure caused by substituting at least part of the rare earth element being used. thinking.

In addition, as shown in Tables 1 and 2, the solid electrolytes according to Examples 1 to 33 exhibiting an ionic conductivity σ of 1×10 ⁻⁷ S/cm or more exhibit a high-angle shift of the X-ray diffraction angle peak, A peak shift to the high angle side of the bimodal diffraction angle peak is observed. That is, in the range of 27.4 degrees or more and 29.0 degrees or less, the diffraction peak on the high angle side observed at 28.3 to 29.0 degrees and the diffraction peak on the low angle side observed at 27.4 to 28.3 degrees It can be read that the difference 2θd between the diffraction angles of the two is expanded to 0.43 degrees or more. That is, the solid electrolyte according to the present embodiment includes Li, an element R selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from the group including Zr, Ce, and Sn. And, in other words, it contains a borate oxide containing. Furthermore, the solid electrolyte according to the present embodiment exhibits two diffraction peaks in the range of the diffraction angle 2θ of 27.4 degrees or more and 29.0 degrees or less in XRD using CuKα rays, one on the high angle side and the other on the low angle side. In other words, the electrolyte has a diffraction angle difference 2θd from the diffraction peak of 0.43 degrees or more.

The two diffraction angle peaks observed in the diffraction angle 2θ range of 27.4 degrees or more and 29.0 degrees or less may exhibit a plurality of peaks including three peaks and four peaks depending on the crystallinity. In the specification of the present application, two diffraction angle peaks, one on the low angle side and one on the high angle side, are represented with a diffraction angle 2θ of 28.3 degrees as a boundary. In this way, the diffraction angle peaks are separated by fitting to the bimodal diffraction angle profile.

The diffraction angle peak on the high angle side is broadened and shifted to the high angle side more significantly than the diffraction angle peak on the low angle side as the component of the substitution element M increases or the ionic conductivity increases. . From this, it can be seen that the solid electrolyte 44 of the present embodiment has a different crystal structure than the non-substituted comparative example, such that a plurality of crystal structures having distributions in lattice spacing and crystallite size are mixed. is read as

The solid electrolytes according to Examples 13 to 33 shown in Table 2, FIG. 6(a), and FIG. Yb, Sm), (Yb, La), and (Er, La) are different from the solid electrolytes according to Examples 1-12.

The solid electrolytes in Examples 14 to 16, 18, 22, 23, and 26 to 33 exhibited ionic conductivity of 1E-5 (S/cm) or more in the same manner as in Examples 2 to 6 and 12, and LCO and the like It can be adopted as a positive electrode of an all-solid-state battery by forming a composite structure combined with the positive electrode active material particles.

Further, in the solid electrolytes according to Examples 1 to 33 exhibiting an ionic conductivity of 1E-7 (S/cm) or more, the atomic concentration ratio [M]/[R] of the substitution element M to the rare earth element R was 0.5. 026 or more and 1.500 or less. Further, the solid electrolytes according to Examples 2 to 6, 8 to 10, and 12 to 33 exhibiting an ionic conductivity of 1E-6 (S/cm) or more have an atomic concentration ratio [M] of the substitution element M to the rare earth element R /[R] was 0.111 or more and 0.667 or less. Furthermore, the solid electrolytes according to Examples 2 to 6, 12, 14 to 16, 18, 22, 23, 26 to 33 exhibiting an ionic conductivity of 2E-5 (S / cm) or more are The atomic concentration ratio [M]/[R] of the substitution element M was 0.111 or more and 0.290 or less.

Among the solid electrolytes containing multicomponent rare earth elements according to Examples 13 to 33, those exhibiting an ionic conductivity of 1E-5 (S / cm) or more have an atomic concentration ratio ([R]-[Yb]) / [R ] was 0.063 or more and 0.200 or less.

The atomic concentration ratio [M]/[R] of the substitution element M to the rare earth element R is obtained by using the R1 ratio, R2 ratio, x1, and x2 described in Table 2, [M]/[R]=(x1+x2)/ It is algebraically written as (R1 ratio+R2 ratio). Similarly, the atomic concentration ratio [M]/[R] of the substitution element M to the rare earth element R is obtained using x1 and x2 described in Table 1, [M]/[R]=(x1+x2)/(1 -x1-x2), and is algebraically described.

The atomic concentration ratio ([R]-[Yb])/[R] is algebraically described as (R2 ratio)/(R1 ratio+R2 ratio) using the R1 ratio and R2 ratio shown in Table 2. .

In Tables 1 and 2, the atomic concentration ratio [M]/[R] of the substitution element M is shown as the atomic concentration ratio [M1]/[R] of the substitution element M1.

44 solid state electrolyte

Claims (30)

A solid electrolyte comprising an oxide represented by the general formula Li _6-x R _1-x M1 _x (BO ₃ ) ₃ .
However, in the formula, R is a trivalent element selected from the group containing Yb, Er, Ho, and Tm, M1 is a tetravalent element selected from the group containing Zr, Ce, and Sn, and x is , 0<x<1. X-ray diffraction analysis using CuKα rays shows two diffraction peaks in the range of 2θ = 27.4 degrees or more and 29.0 degrees or less. 2. The solid electrolyte according to claim 1, wherein the difference 2[theta]d is 0.43 degrees or more. 2. The solid electrolyte according to claim 1, wherein R is Yb, and exhibits a diffraction peak in the range of 2θ=28.07 degrees or more and 28.20 degrees or less in X-ray diffraction analysis using CuKα rays. The solid electrolyte according to any one of claims 1 to 3, wherein said R is Yb, said M1 is Zr, and said x satisfies 0<x<1. 2. The solid electrolyte according to claim 1, wherein said R is Er, and exhibits a diffraction peak in the range of 2θ=27.94 degrees or more and 28.10 degrees or less in X-ray diffraction analysis using CuKα rays. 6. The solid electrolyte according to any one of claims 1, 2 and 5, wherein said R is Er, said M1 is Zr, and said x satisfies 0<x<1. 7. The positive electrode active material through which lithium ions are exchanged between the solid electrolyte and the electrolyte, and a surface on which the solid electrolyte and the active material are arranged. positive electrode. A positive electrode according to claim 7;
an electrolyte layer that is arranged in contact with the surface and exchanges lithium ions with the positive electrode;
a negative electrode in contact with the surface of the electrolyte layer opposite to the surface in contact with the surface. 7. The electrolyte layer according to any one of claims 1 to 6, having a surface on which the solid electrolytes are arranged. The electrolyte layer according to claim 9, a positive electrode disposed so as to be in contact with said surface and disposed so that lithium ions are exchanged with said electrolyte layer, and a surface opposite said surface of said electrolyte layer. A secondary battery comprising: a negative electrode in contact with the battery; A solid containing a borate containing Li, an element R selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from the group including Zr, Ce, and Sn. Electrolytes. 12. The solid electrolyte according to claim 11, wherein the atomic concentration ratio [M]/[R] of the element M to the element R is 0.026 or more and 1.500 or less. 13. The solid electrolyte according to claim 12, wherein the atomic concentration ratio [M]/[R] is 0.111 or more and 0.290 or less. containing a borate containing Li, an element R selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from the group including Zr, Ce, and Sn, In the X-ray diffraction analysis using CuKα rays, two diffraction peaks are exhibited in the range of the diffraction angle 2θ from 27.4 degrees to 29.0 degrees, and the diffraction peak on the high angle side and the diffraction peak on the low angle side A solid electrolyte having a difference 2θd of 0.43 degrees or more. A solid electrolyte comprising an oxide represented by the general formula Li _6-x R _1-x M _x (BO ₃ ) ₃ .
However, in the formula, R is a rare earth element selected from the group including Yb, Er, Ho, Tm, La, Nd, and Sm, M is an element selected from the group including Zr, Ce, and Sn, and x is a real number that satisfies 0<x<1. In the X-ray diffraction analysis using CuKα rays, two diffraction peaks are exhibited in the range of the diffraction angle 2θ from 27.4 degrees to 29.0 degrees, and the diffraction peak on the high angle side and the diffraction peak on the low angle side 16. The solid electrolyte according to claim 14 or 15, wherein the difference 2[theta]d is 0.43 degrees or more. 17. The solid electrolyte according to any one of claims 11 to 16, wherein said element M contains Zr. 18. The solid electrolyte according to claim 17, wherein said element M further contains Ce. 19. The solid electrolyte according to any one of claims 11 to 18, wherein said element R includes a plurality of rare earth elements. 20. The solid electrolyte according to claim 19, wherein said plurality of rare earth elements include at least Yb. 21. The method according to claim 20, wherein the atomic concentration ratio ([R]-[Yb])/[R] of the elements contained in the element R excluding the Yb in the rare earth element R is 0.063 or more and 0.200 or less. The solid electrolyte described. 22. Any one of claims 11 to 21, wherein the element R contains Yb, and exhibits a diffraction peak in a range of diffraction angles 2θ of 28.07 degrees or more and 28.20 degrees or less in X-ray diffraction analysis using CuKα rays. Solid electrolyte according to. 16. The solid electrolyte according to claim 15, wherein said R comprises Yb, said M comprises Zr, and said x satisfies 0<x<1. 16. The solid electrolyte according to claim 15, wherein said R contains Er, and exhibits a diffraction peak in the range of diffraction angle 2θ of 27.94 degrees or more and 28.10 degrees or less in X-ray diffraction analysis using CuKα rays. 16. The solid electrolyte according to claim 15, wherein said R comprises Er, said M comprises Zr, and said x satisfies 0<x<1. A positive electrode comprising: the solid electrolyte according to any one of claims 11 to 25; and a positive electrode active material with which lithium ions are exchanged with the solid electrolyte. 27. The positive electrode according to claim 26, having a surface on which the solid electrolyte and the positive electrode active material are arranged. A positive electrode according to claim 27;
an electrolyte layer that is arranged in contact with the surface and exchanges lithium ions with the positive electrode;
a negative electrode in contact with the surface of the electrolyte layer opposite to the surface in contact with the surface. An electrolyte layer having a surface on which the solid electrolyte according to any one of claims 11 to 28 is arranged. 30. The electrolyte layer according to claim 29, a positive electrode disposed in contact with said surface and disposed so that lithium ions are exchanged with said electrolyte layer, and a surface opposite said surface of said electrolyte layer. A secondary battery comprising: a negative electrode in contact with the battery;

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