Solid electrolyte composition and method for manufacturing the same

Abstract

To provide a solid electrolyte composition by which a sintered body having high relative density can be obtained, and a method for manufacturing the composition.SOLUTION: A solid electrolyte composition of the present invention contains (A) garnet type solid electrolyte including Li, La and Zr, (B) complex oxide including Li, Ge and V, (C) Li3BO3 or a precursor thereof, and the component (B) is amorphous. It is preferable that the components (A), (B) and (C) be integrated, and it is preferable that a composition in this case has a granular state. A solid electrolyte composition of the present invention can be manufactured by a method comprising a step of mixing the garnet type solid electrolyte, a precursor material BX of the complex oxide, a precursor material CX of Li3BO3, and water to prepare dispersion liquid in which the garnet type solid electrolyte is dispersed in aqueous solution of the precursor material BX and precursor material CX, and a step of removing water from the dispersion liquid, sequentially.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a garnet-type solid electrolyte composition, a method for producing the same, a sintered body, a method for producing the same, and an all-solid-state battery.

Background Art

[0002] As a solid electrolyte constituting an oxide all-solid-state battery, a Li7La3Zr2O having a garnet-type structure, which gives higher ionic conductivity than an amorphous solid electrolyte, 12 based materials are known, and in order to obtain more excellent ionic conductivity and the like, studies have been made on modifying materials having a garnet-type structure or laminating other solid electrolyte layers.

[0003] Patent Document 1 discloses a ceramic material containing lithium (Li), lanthanum (La), zirconium (Zr), oxygen (O), and aluminum (Al). Patent Document 2 discloses a ceramic material containing Li, La, Zr, Nb and / or Ta and O and having a garnet-type or garnet-type similar crystal structure. Patent Document 3 discloses a lithium ion conductive oxide characterized by containing lithium, lanthanum, zirconium, boron, and aluminum. Further, Non-Patent Document 1 discloses a multilayer solid electrolyte sheet obtained by forming a film on a Li7La3Zr2O 12 sheet using crystalline Li 3.5 Ge 0.5 V 0.5 O4 prepared in advance.

[0004] When manufacturing an all-solid-state battery, at least a positive electrode material, a solid electrolyte, and a negative electrode material (all solids) are used, and a precursor composite in which each layer made of these materials is sequentially laminated is heat-treated (sintered) and integrally formed. In this case, from the viewpoint of battery performance such as improvement of ionic conductivity, densification of each layer in the integrated product is required, and for example, heat treatment at a high temperature of 1000 °C or higher has been common.

[0005] However, setting a high heat treatment temperature (sintering temperature) is not economical, and the stability of the solid electrolyte contained in the battery may not be maintained. Therefore, solid electrolytes or methods for manufacturing the same that can reduce the heat treatment temperature for sintering have been investigated.

[0006] Patent Document 4 discloses a solid electrolyte having a garnet-type crystal structure, comprising solid electrolyte particles composed of a lithium lanthanum zirconium-based composite oxide containing an M3 element consisting of at least one of Bi and Sb, and a non-molten phase present in at least one of the intragranular and intergranular regions of the solid electrolyte particles, the non-molten phase being composed of a material having a lower lithium ion conductivity than the lithium lanthanum zirconium-based composite oxide.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a solid electrolyte composition capable of obtaining a sintered body with a high relative density by firing, a method for manufacturing the same, a sintered body, a method for manufacturing the same, and an all-solid-state battery. Another object of the present invention is to provide a solid electrolyte composition capable of densifying and obtaining a sintered body with a high relative density even when firing is performed at a temperature as low as about 700°C, instead of a high temperature of at least 900°C as in the conventional method, a method for manufacturing the same, a sintered body, and a method for manufacturing the same. In the present invention, density means relative density, which is the ratio of the measured density to the theoretical density.

Means for Solving the Problems

[0010] The present inventors have found that when an amorphous composite oxide containing Li, Ge, and V and Li3BO3 or its precursor are used as sintering aids and fired on a garnet-type solid electrolyte, a sintered body mainly composed of a garnet-type solid electrolyte with a high relative density can be obtained.

[0011] The present invention is shown below. 1. A solid electrolyte composition containing (A) a garnet-type solid electrolyte containing Li, La, and Zr, (B) a composite oxide containing Li, Ge, and V, and (C) Li3BO3 or its precursor material, wherein the above component (B) is amorphous. 2. The solid electrolyte composition according to item 1 above, wherein the above components (A), (B), and (C) are integrated. 3. The solid electrolyte composition according to item 2 above, which has a particulate form. 4. The solid electrolyte composition according to item 1 above, wherein the content ratios of the above components (A), (B), and (C) are 80 to 95% by mass, 3 to 15% by mass, and 2 to 10% by mass, respectively, when the total of these is 100% by mass. 5. A method for manufacturing the solid electrolyte composition according to item 1 above, Mix the above garnet-type solid electrolyte, the precursor material BX of the above composite oxide, the precursor material CX of the above Li3BO3, and water to prepare a dispersion in which the garnet-type solid electrolyte is dispersed in an aqueous solution of the precursor material BX and the precursor material CX, and a method for producing a solid electrolyte composition sequentially comprising a step of removing water from the dispersion. 6. The method for producing a solid electrolyte composition according to item 5 above, wherein the precursor material BX contains lithium hydroxide, germanium oxide, and vanadium oxide. 7. The method for producing a solid electrolyte composition according to item 5 above, wherein the precursor material CX contains lithium hydroxide and boric acid. 8. A method for producing a sintered body sequentially comprising a step of subjecting the solid electrolyte composition according to item 1 above to pressure molding to produce a molded body, and a step of subjecting the molded body to heat treatment. 9. The method for producing a sintered body according to item 8 above, wherein the temperature of the heat treatment is 700°C to 800°C. 10. A sintered body obtained by the method for producing a sintered body according to item 8 above. 11. An all-solid-state battery including the sintered body according to item 10 above.

Advantages of the Invention

[0012] When the solid electrolyte composition of the present invention is fired, a sintered body with a high relative density can be obtained. Therefore, this sintered body is expected to be suitably used, for example, as a solid electrolyte layer having high ionic conductivity in an all-solid-state battery. Further, for example, when manufacturing a bulk-type all-solid-state battery, a method of integrally molding a precursor composite in which a solid cathode layer forming material, a solid electrolyte layer forming material, and a solid anode layer forming material are used and each layer made of these materials is sequentially laminated is applied. However, in the conventional method, the heat treatment temperature during integral molding was at least 900°C, usually 1000°C or higher. In the solid electrolyte composition of the present invention, for forming the solid electrolyte layer, a low temperature of 700°C can be used. Therefore, not only can the manufacturing cost be reduced, but also an effect of suppressing the problem that the composition of the cathode layer, solid electrolyte layer, or anode layer changes due to the high heat treatment temperature is expected.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] The solid electrolyte composition of the present invention is a composition containing, as component (A), a garnet-type solid electrolyte containing Li, La, and Zr, as component (B), an amorphous composite oxide containing Li, Ge, and V, and as component (C), Li3BO3 or its precursor material. The solid electrolyte composition of the present invention uses the sintered body thereof as the solid electrolyte layer of an all-solid-state battery. [1] After producing a plate-shaped molded article by pressure molding or the like, the loaded article obtained by arranging this molded article between a sheet for forming a positive electrode layer and a sheet for forming a negative electrode layer is subjected to heat treatment (firing treatment) to sinter at least the above-mentioned molded article, and further, a positive electrode current collector (21) and a negative electrode current collector (29) are disposed, for example, to constitute the all-solid-state battery (10) shown in FIG. 1, or [2] After producing a plate-shaped molded article by pressure molding or the like, this molded article is subjected to heat treatment (firing treatment) to obtain a sintered body, and the obtained sintered body is interposed between a positive electrode layer (23) and a negative electrode layer (27) as a solid electrolyte layer (25), and further, the positive electrode layer (23) and the negative electrode layer (27) are respectively in contact with and arranged on a positive electrode current collector (21) and a negative electrode current collector (29), for example, to constitute the all-solid-state batteries (10, 11) shown in FIGS. 1 and 2.

[0015] The above-mentioned component (A) is a garnet-type solid electrolyte, and is usually an oxide containing Li, La, and Zr. As long as the above-mentioned component (A) has a garnet structure, it may be a compound composed of Li, La, Zr, and O, or further, a compound containing Ta, Nb, Al, Ga, etc. as other atoms. As the above-mentioned component (A), Li7La3Zr2O 12 , Li 7-x La3Zr 2-y (Ta,Nb) y O 12 , Li 7-3x Al x La3Zr2O 12 , Li 7-3x Ga x La3Zr2O 12 and the like can be mentioned. The component (A) contained in the solid electrolyte composition of the present invention may be only one kind or two or more kinds.

[0016] Component (B) is an amorphous composite oxide containing Li, Ge, and V, and its composition is not particularly limited. In the present invention, this component (B) is preferably a crystalline Li-Ge-V-based composite oxide by heat treatment (firing treatment) during the production of the sintered body, specifically, crystalline Li 3.5 Ge 0.5 V 0.5 O4-providing compound, and is an amorphous composite oxide with an element molar ratio of Li:Ge:V = 3.5:0.5:0.5.

[0017] Component (C) is Li3BO3 or its precursor material (hereinafter referred to as "precursor material C1"). The former Li3BO3 may be either crystalline or amorphous. The latter precursor material C1 may be composed of a single substance or a plurality of substances as long as crystalline Li3BO3 is formed by heat treatment (firing treatment) for producing the sintered body. In the present invention, this precursor material C1 preferably contains lithium carbonate and / or lithium hydroxide, and boric acid, which provide crystalline Li3BO3 by heat treatment (firing treatment). Component (C) contained in the solid electrolyte composition of the present invention may be either one or both of Li3BO3 and precursor material C1.

[0018] The preferred content ratios of components (A), (B), and (C) contained in the solid electrolyte composition of the present invention are, for example, when a molded product prepared by subjecting the solid electrolyte composition to pressure molding or the like is heat-treated (fired) to obtain a sintered body, in terms of being able to achieve a high relative density and fully reflecting the ion conductivity based on component (A) in the all-solid-state battery, when the total of components (A), (B), and (C) is 100% by mass, they are preferably 80 to 95% by mass, 3 to 15% by mass, and 2 to 10% by mass, respectively, and more preferably 80 to 85% by mass, 5 to 10% by mass, and 5 to 10% by mass.

[0019] In the present invention, when the solid electrolyte composition is subjected to pressure molding or the like, a molded product for producing a sintered body can be efficiently obtained, so the solid electrolyte composition is preferably, for example, a mixture of powders consisting of components (A), (B) and (C) (hereinafter referred to as "Aspect 1"), or an integrated product of components (A), (B) and (C) (hereinafter referred to as "Aspect 2"). In the latter case of Aspect 2, the shape and size of the integrated product are not particularly limited. The shape of the integrated product can be particulate, blocky, etc., but in the present invention, from the viewpoint of formability of the molded product used to form the sintered body, it is preferable that the integrated product is particulate. In this case, the particle size is preferably 30 μm or less, more preferably 1 to 20 μm.

[0020] The method for producing the solid electrolyte composition of the present invention is not particularly limited. In the case of aspect 1, the solid electrolyte composition can be produced by a method of mixing the components (A), (B), and (C) that have been prepared. In the case of aspect 2, the solid electrolyte composition can be produced by a method (hereinafter referred to as the "production method of the solid electrolyte composition of the present invention") that sequentially includes a step of preparing a dispersion in which the garnet-type solid electrolyte is dispersed in an aqueous solution of the precursor materials BX and CX by mixing the garnet-type solid electrolyte, the precursor of the amorphous composite oxide (hereinafter referred to as the "precursor material BX"), the precursor material of Li3BO3 (hereinafter referred to as the "precursor material CX"), and water, and a step of removing water from the dispersion (hereinafter referred to as the "water removal step"). In particular, according to the method for producing a solid electrolyte composition of the present invention for producing the solid electrolyte composition of embodiment 2, it is possible to efficiently produce a solid electrolyte composition consisting of an integrated product containing a garnet-type solid electrolyte as component (A), an amorphous composite oxide as component (B), and Li3BO3 as component (C).

[0021] In the dispersion preparation step according to the method for manufacturing a solid electrolyte composition of the present invention, a garnet-type solid electrolyte, a precursor material BX, a precursor material CX, and water are mixed. As the garnet-type solid electrolyte, the above component (A) is used as it is, and its average particle diameter is preferably 0.1 to 5 μm, more preferably 0.2 to 3 μm.

[0022] The precursor material BX provides an amorphous composite oxide as component (B) by a water removal step after the dispersion preparation step, and it is preferably a raw material component that dissolves in water in the resulting dispersion. In the present invention, it is particularly preferable to contain lithium hydroxide (or its hydrate), germanium oxide, and vanadium oxide. Further, the precursor material BX is preferably composed of these raw material components such that the molar ratio of the elements is Li:Ge:V = 3.5:0.5:0.5. Incidentally, in order to synthesize the composite oxide as component (B) using the precursor material BX, the precursor material may need to contain water in some cases. However, here, since water is used for the preparation of the dispersion, the precursor material BX is assumed not to contain water.

[0023] The precursor material CX provides Li3BO3, preferably amorphous Li3BO3, as component (C) by a water removal step after the dispersion preparation step, and it is preferably a raw material component that dissolves in water in the resulting dispersion. In the present invention, it is particularly preferable to contain lithium hydroxide (or its hydrate) and boric acid. Further, the precursor material CX is preferably composed of these raw material components such that the molar ratio of the elements is Li:B = 3:1. Incidentally, in order to synthesize Li3BO3 as component (C) using the precursor material CX, the precursor material CX may need to contain water in some cases. However, here, since water is used for the preparation of the dispersion, the precursor material CX is assumed not to contain water.

[0024] In the dispersion preparation step, conventionally, a garnet-type solid electrolyte, a precursor material BX, a precursor material CX, and water may be mixed by a known method. The mixing means, the atmosphere during mixing, the mixing temperature, the mixing time, etc. are not particularly limited. Also, the amounts of the garnet-type solid electrolyte, the precursor material BX, the precursor material CX, and water used are not particularly limited, but when the total of components (A), (B), and (C) is 100% by mass after the water removal step in the dispersion preparation step, the garnet-type solid electrolyte, the precursor material BX, and the precursor material CX are preferably used such that they are 80 to 95% by mass, 3 to 15% by mass, and 2 to 10% by mass, respectively, and water is used such that the concentration of the medium is preferably 2 to 30% by mass.

[0025] The inventors of the present invention believe that, with respect to the dispersion obtained by the dispersion preparation step, at the time when the garnet-type solid electrolyte, the precursor material BX, the precursor material CX, and water are mixed, the garnet-type solid electrolyte is dispersed in the aqueous solutions of the precursor material BX and the precursor material CX, but at the time when the mixing is completed, component (A), the amorphous component (B) generated from the precursor material BX and water, and the amorphous Li3BO3, i.e., component (C), generated from the precursor material CX and water are dispersed in water.

[0026] Next, the water removal step in the method for manufacturing a solid electrolyte composition of the present invention is a step of removing the solvent water from the dispersion obtained in the dispersion preparation step, i.e., a dehydration step. In this water removal step, a heat drying method, a vacuum drying method, etc. can be applied. In the present invention, a heat drying method by spray drying or thin film drying is preferable. Specifically, a spray drying method such as a spray drying method, a drum drying method, a disk drying method, a belt drying method, etc. can be mentioned. By applying spray drying such as a spray drying method, a particulate solid electrolyte composition that is easy to press-mold, i.e., a particulate solid electrolyte composition in which components (A), (B), and (C) are integrated, can be efficiently manufactured.

[0027] In the method for producing a solid electrolyte composition of the present invention, when the solid electrolyte composition obtained by the water removal step does not have the components (A), (B), and (C) in desired proportions, a composition adjustment step of further adding and mixing the component (A), (B), or (C) can be further provided.

[0028] As described above, the solid electrolyte composition of the present invention is suitable as a raw material for producing a sintered body having a high relative density. The method for producing such a sintered body is not particularly limited, but the method for producing a sintered body of the present invention includes a step of subjecting the solid electrolyte composition to pressure molding to produce a molded article (hereinafter referred to as the "molded article production step"), and a step of subjecting the obtained molded article to heat treatment (hereinafter referred to as the "firing step") in sequence.

[0029] In the molded article production step according to the method for producing a sintered body of the present invention, conventionally known pressure molding means can be applied. The shape and size of the molded article are not particularly limited.

[0030] In the firing step according to the method for producing a sintered body of the present invention, conventionally known heat treatment means (for example, hot isostatic pressing, spark plasma sintering, hot pressing, etc.) can be applied. The heat treatment conditions of the firing step according to the present invention are not particularly limited. The atmosphere can be air, oxygen, etc. Further, the heat treatment temperature is preferably 650°C or higher, more preferably 700°C or higher, and the upper limit can be 800°C. However, in the present invention, a sintered body having a high relative density can be produced even at 800°C.

[0031] According to the firing step of the method for producing a sintered body of the present invention, the component (A) contained in the molded article remains without decomposition, denaturation, etc., and the amorphous component (B) contained in the molded article is denatured into a crystalline form. Further, regardless of whether the component (C) contained in the molded article is Li3BO3 or its precursor, crystalline Li3BO3 is formed. Therefore, the obtained sintered body of the present invention contains a garnet-type solid electrolyte, a crystalline Li-Ge-V-based composite oxide, and crystalline Li3BO3.

[0032] The content ratios of the garnet-type solid electrolyte, crystalline Li-Ge-V-based composite oxide, and crystalline Li3BO3 that constitute the sintered body of the present invention, when the total of these is 100% by mass, are preferably 80 to 95% by mass, 3 to 15% by mass, and 2 to 10% by mass, respectively, and more preferably 80 to 85% by mass, 5 to 10% by mass, and 5 to 10% by mass.

[0033] The relative density of the sintered body of the present invention is preferably 80% or more, more preferably 85% or more, and the upper limit is usually 90%.

[0034] The all-solid-state battery of the present invention is characterized by including the sintered body of the present invention. As described above, the all-solid-state battery (10: bulk-type all-solid-state battery) in FIG. 1 and the all-solid-state battery (11: thin-film-type all-solid-state battery) in FIG. 2 exemplify the all-solid-state battery of the present invention, and are all-solid-state batteries in which the solid electrolyte layer (25) is formed by the sintered body of the present invention. The bulk-type all-solid-state battery in FIG. 1 and the thin-film-type all-solid-state battery in FIG. 2 have conventionally known structures.

[0035] Hereinafter, the positive electrode current collector (21), positive electrode layer (23), solid electrolyte layer (25), negative electrode layer (27), and negative electrode current collector (29) included in the all-solid-state battery of the present invention will be briefly described.

[0036] The constituent materials of the positive electrode current collector (21) and the negative electrode current collector (29) are not particularly limited, and either can be Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, or the like. The thicknesses of the positive electrode current collector (21) and the negative electrode current collector (29) are also not particularly limited and are appropriately selected according to the desired battery performance.

[0037] The positive electrode layer (23) contains at least particulate positive electrode active material. The positive electrode active material is not particularly limited, and examples include lithium manganese composite oxides (e.g., Li x Mn2O4, Li x MnO2), lithium nickel composite oxides (e.g., Li x NiO2), lithium cobalt composite oxides (e.g., Li xCoO₂), lithium nickel cobalt composite oxide (e.g., LiNi 1-y Co y O₂), lithium manganese cobalt composite oxide (e.g., LiMn y Co 1-y O₂), lithium manganese cobalt nickel composite oxide (e.g., LiMn x Co y Ni z O₂), spinel-type lithium manganese nickel composite oxide (e.g., Li x Mn 2-y NiyO₄), lithium phosphate compound having an olivine structure (e.g., Li x FePO₄, Li x Fe 1-y Mn y PO₄, Li x CoPO₄), lithium phosphate compound having a NASICON structure (e.g., Li x V₂(PO₄)₃), iron sulfate, vanadium oxide (e.g., V₂O₅), etc. may be mentioned. In addition, a lithium niobate layer, a lithium titanate layer, a lithium phosphate layer, etc. may be provided on the surface of the core portion composed of these compounds.

[0038] The positive electrode layer (23) can contain, in addition to the positive electrode active material, a solid electrolyte, a conductive assistant, a binder, etc., if necessary. As the solid electrolyte, conventionally known oxide solid electrolytes, sulfide solid electrolytes, etc. can be used. As the conductive assistant, carbon materials such as acetylene black, ketjen black, channel black, furnace black, carbon fiber; metal materials such as nickel, aluminum, stainless steel, etc. can be used. As the binder, butadiene rubber, butylene rubber, acrylate butadiene rubber, styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, etc. can be used.

[0039] The thickness of the positive electrode layer (23) is not particularly limited, but is usually 10 μm or more, and the upper limit is usually 1 mm.

[0040] As described above, the solid electrolyte layer (25) contains a garnet-type solid electrolyte as a main component, and both crystalline Li-Ge-V-based composite oxides and Li3BO3.

[0041] The thickness of the solid electrolyte layer (25) is not particularly limited, but is usually 1 μm or more, and the upper limit is usually 1 mm.

[0042] The negative electrode layer (27) contains at least particulate negative electrode active material. The negative electrode active material is not particularly limited, and examples include silicon-based active materials (e.g., Si, Si alloys, silicon oxides, etc.); carbon-based active materials (e.g., graphite, hard carbon, etc.); oxide-based active materials (e.g., SnO, SnO2, GeO, GeO2, In2O, In2O3, PbO, PbO2, Pb2O3, Pb3O4, Ag2O, AgO, Ag2O3, Sb2O3, Sb2O4, Sb2O5, ZnO, CoO, NiO, FeO, TiO2, Li4Ti5O 12 etc.); metallic lithium, lithium alloys, and the like.

[0043] In addition to the negative electrode active material, the negative electrode layer (27) can contain a solid electrolyte, a conductive assistant, a binder, etc., which may also be contained in the positive electrode layer (23) as necessary.

[0044] The thickness of the negative electrode layer (27) is not particularly limited, but is usually 10 μm or more, and the upper limit is usually 1 mm.

[0045] In the present invention, for example, the bulk-type all-solid-state battery (10) of FIG. 1 can further include a resin exterior body that covers the outer peripheries of the positive electrode current collector (21), the positive electrode layer (23), the solid electrolyte layer (25), the negative electrode layer (27), and the negative electrode current collector (29) (not shown).

[0046] Since the garnet-type solid electrolyte contained in the solid electrolyte layer (25) is an oxide, it has excellent atmospheric stability and high conductivity at room temperature. Therefore, if the solid electrolyte layer (25) is made of a sintered body with a high relative density, it is useful in the bulk-type all-solid-state battery (10) of FIG. 1. Also, as described above, such a dense sintered body can be obtained by heat-treating a pressure-formed body composed of a solid electrolyte composition containing components (A), (B), and (C) at 700°C to 800°C. Therefore, when manufacturing a bulk-type all-solid-state battery, when using a solid cathode layer forming material, the above solid electrolyte composition, and a solid anode layer forming material, and integrally molding a precursor composite in which each layer made of these materials is sequentially laminated, by heat-treating at 700°C to 800°C, it is possible to suppress the compositional changes of the obtained cathode layer, solid electrolyte layer, and anode layer.

[0047] Also, in the thin-film type all-solid-state battery (11) of FIG. 2, the substrate (20) can be made of, for example, resins such as polyamide, polyimide, PET, PPS, polypropylene, glass, silicon, etc.

[0048] The method for manufacturing the all-solid-state battery of the present invention is not particularly limited. The bulk-type all-solid-state battery of FIG. 1, for example, includes a negative electrode forming step of forming a negative electrode layer (27) by applying and drying a slurry containing a negative electrode active material on a negative electrode current collector layer (29), a step of placing a pressure-formed body (thin body) made of the solid electrolyte composition of the present invention on the negative electrode layer (27), a positive electrode forming step of forming a positive electrode layer (23) by applying and drying a slurry containing a positive electrode active material on the pressure-formed body of the solid electrolyte composition, a negative electrode current collector placing step of placing a negative electrode current collector (29) on the positive electrode layer (23) to produce a stacked product, and a step of heat-treating (firing) the stacked product under pressure. It can be manufactured by a method that sequentially includes these steps. In addition, instead of the step of placing the pressure-formed body of the solid electrolyte composition and the positive electrode forming step, a solid electrolyte layer (25) can be formed by applying and drying a slurry of the solid electrolyte composition on the negative electrode layer (27), and then, a positive electrode layer (23) can be formed by applying and drying a slurry containing a positive electrode active material on this solid electrolyte layer (25).

[0049] In addition, the thin-film all-solid-state battery (11) shown in FIG. 2 can be manufactured, for example, by a method sequentially including a current collector forming step of forming a positive current collector (21) and a negative current collector (29) on a substrate (20), a negative electrode forming step of forming a negative electrode layer (27) containing a negative electrode active material on the negative current collector layer (29), a solid electrolyte layer forming step of forming a solid electrolyte layer (25) covering a part of the surface of the positive current collector (21) and the entire surface of the negative electrode layer (27) using the solid electrolyte composition of the present invention, and a positive electrode forming step of forming a positive electrode layer (23) containing a positive electrode active material so as to cover a part of the surface of the positive current collector (21) and the solid electrolyte layer (25). In the solid electrolyte layer forming step, heat treatment (firing) can be performed after the solid electrolyte composition is disposed at a predetermined portion.

Example

[0050] Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples at all.

[0051] 1. Manufacturing raw materials As the garnet-type solid electrolyte, solid electrolyte powder "Li 6.6 La3Zr 1.6 Ta 0.4 O 12 " (hereinafter referred to as "LLZT") manufactured by Toyoshima Seisakusho Co., Ltd. was used. When X-ray diffraction measurement of this LLZT powder was performed, it was found to be crystalline (not shown).

[0052] Those obtained in Synthesis Examples 1 to 4 were used as sintering aids.

[0053] Synthesis Example 1 (Synthesis of crystalline LGVO) 6.53 g of lithium carbonate, 2.66 g of germanium dioxide, and 2.30 g of vanadium oxide were mixed using an agate mortar, and the obtained mixture was heated at 900 ° C for 1 hour to obtain Li-Ge-V powder. The molar ratio of each element is Li:Ge:V = 3.5:0.5:0.5.

[0054] When X-ray diffraction measurement was performed on the obtained Li-Ge-V powder, the diffraction pattern shown in Fig. 3 was obtained. From Fig. 3, it was found that the Li-Ge-V powder was crystalline Li 3.5 Ge 0.5 V 0.5 O4 (hereinafter referred to as "crystalline LGVO").

[0055] Synthesis Example 2 (Synthesis of Crystalline LBO) 3.11 g of lithium hydroxide hydrate and 6.30 g of boric acid were mixed using an agate mortar, and the resulting mixture was heated at 600 °C for 12 hours to obtain Li-B powder. The molar ratio of each element was Li:B = 3:1.

[0056] When X-ray diffraction measurement was performed on the obtained Li-B powder, the diffraction pattern shown in Fig. 4 was obtained. From Fig. 4, it was found that the Li-B powder was crystalline Li3BO3 (hereinafter referred to as "crystalline LBO").

[0057] Synthesis Example 3 (Synthesis of Amorphous LGVO) 16.2 g of lithium hydroxide hydrate was dissolved in 250 mL of ion-exchanged water to obtain an aqueous solution. Next, this aqueous solution was adjusted to 20 °C to 25 °C, and while stirring, 5.2 g of germanium dioxide and 4.6 g of vanadium oxide were added and reacted over 1 hour while dissolving. Then, ion-exchanged water was added to make a total of 500 mL to obtain a 0.2 mol / L Li-Ge-V aqueous solution. The molar ratio of each element was Li:Ge:V = 3.5:0.5:0.5. Next, using a spray dryer device manufactured by Yamato Corporation, Li-Ge-V particles with Li:Ge:V = 3.5:0.5:0.5 were formed from the above Li-Ge-V aqueous solution.

[0058] When X-ray diffraction measurement was performed on the obtained Li-Ge-V particles, the diffraction pattern shown in Fig. 5 was obtained. From Fig. 5, it was found that the Li-Ge-V particles were amorphous. Further, when this amorphous Li-Ge-V particle was heat-treated at 600 °C in the air and X-ray diffraction measurement of the heat-treated product was performed, the diffraction pattern shown in Fig. 6 was obtained. Since Fig. 6 shows the same pattern as Fig. 3, the above amorphous Li-Ge-V particles are Li3.5 Ge 0.5 V 0.5 It is presumed to be VGeO4 (hereinafter referred to as "amorphous LGVO").

[0059] Synthesis Example 4 (Synthesis of Li3BO3 Precursor Material) 27.7 g of lithium hydroxide hydrate was dissolved in 250 mL of ion-exchanged water to obtain an aqueous solution. Next, while maintaining this aqueous solution at 20°C to 25°C and stirring, 12.4 g of boric acid was added and reacted over 1 hour while being dissolved. Then, ion-exchanged water was added to make a total of 1 L, and a 0.2 mol / L Li-B aqueous solution was obtained. The molar ratio of each element is Li:B = 3:1. Next, solid particles were formed from the Li-B aqueous solution using a spray dryer apparatus.

[0060] When X-ray diffraction measurement of the obtained solid particles was performed, the diffraction image of FIG. 7 was obtained. From this FIG. 7, it was found that the solid particles consisted of low-crystalline lithium carbonate, lithium hydroxide, and boric acid. Regarding the detection of lithium carbonate, the inventors presume that it was formed by the reaction of the Li-B aqueous solution with carbon dioxide in the atmosphere during the spray drying process. Further, when this solid particle was heat-treated at 600°C in the atmosphere and X-ray diffraction measurement of the heat-treated product was performed, the diffraction image of FIG. 8 was obtained. Since this FIG. 8 shows the same pattern as FIG. 4 (the pattern of Li3BO3), the above solid particles consist of a precursor that gives crystalline Li3BO3 (hereinafter referred to as "Li3BO3 precursor material").

[0061] 2. Manufacture and Evaluation of Solid Electrolyte Composition Example 1 Into the mill container (internal volume 80 mL) of a planetary ball mill, 15.1 mL of a 4M-LiOH aqueous solution prepared by dissolving lithium hydroxide hydrate in ion-exchanged water and 23.6 mL of ion-exchanged water were put. Next, 7.2 g of LLZT powder was added to this mixed solution, and further, as a dispersion medium, 60 g of φ5 mm zirconia balls were put. Then, the mill container was sealed and the planetary ball mill was driven (rotation speed: 300 rpm, 3 hours). Next, the dispersion slurry in the mill container was filtered to remove the zirconia balls, and the liquid reaction product (hereinafter referred to as "the first slurry") was recovered. Thereafter, while stirring this first slurry at 20°C to 25°C, 0.314 g of germanium dioxide, 0.276 g of vanadium oxide, and 0.703 g of boric acid were added and reacted while being dissolved to obtain a reaction solution (concentration: 3% by mass) in which the composite was dissolved. Then, using a spray dryer device, particles were formed from the reaction solution to obtain composite particles (hereinafter referred to as "the first composite particles") containing LLZT, Li-Ge-V-O, and Li-B-O in a mass ratio of 80:10:10.

[0062] When X-ray diffraction measurement of the obtained first composite particles was performed, the diffraction image of FIG. 9 was obtained. From this FIG. 9, only the pattern of garnet-structured LLZT could be confirmed. Crystalline Li 3.5 Ge 0.5 V 0.5 The patterns of O4 and crystalline Li3BO3 were not seen, so it is considered that Li-Ge-V-O is amorphous and Li-B-O is also amorphous.

[0063] Furthermore, when the first composite particles were photographed with an electron microscope, the image of FIG. 10 was obtained. According to this FIG. 10, it can be seen that many of the first composite particles have a convex structure with minute pieces attached to the surface of the base portion composed of substantially spherical bodies. From this, it is estimated that the base portion is composed of garnet-structured LLZT and the minute pieces are composed of amorphous Li-Ge-V-O and amorphous Li-B-O. Also, the particle size of the first composite particles was 1 to 20 μm.

[0064] Next, in order to produce a sintered body, a disk-shaped compact (diameter: about 10 mm, thickness: about 1.2 mm) was produced by the following method using the first composite particles. That is, 1 g of the first composite particles was put into the cavity of a molding machine, and after performing preliminary molding (48 MPa) of uniaxial pressing, it was subjected to CIP molding (215 MPa). Subsequently, the obtained disk-shaped compact was placed in a crucible and fired using an electric furnace to obtain a sintered body. The firing temperature was 700 °C, 750 °C, or 800 °C, and the firing time was 12 hours in each case. No defects were found in the appearance of the three types of sintered bodies obtained.

[0065] When the relative density of the obtained sintered body was measured, it was 87.8% at a firing temperature of 700 °C, 87.8% at a firing temperature of 750 °C, and 86.9% at a firing temperature of 800 °C.

[0066] Example 2 LLZT particles, amorphous LGVO particles obtained in Synthesis Example 3, and Li3BO3 precursor material particles obtained in Synthesis Example 4 were weighed into a mill container (inner volume: 80 mL) of a planetary ball mill so that the mass ratio was 80:10:10. Further, 60 g of φ5 mm zirconia balls were added as a dispersion medium. Subsequently, the mill container was sealed and the planetary ball mill was driven (rotation speed: 400 rpm, 15 hours). Next, the zirconia balls were removed using a sieve to obtain a homogeneous mixture (mixed powder) composed of garnet-structured LLZT, amorphous LGVO, and Li3BO3 precursor material.

[0067] When X-ray diffraction measurement of the obtained mixed powder was performed, a diffraction pattern with the same pattern as in FIG. 9 was obtained (not shown).

[0068] Next, in order to produce a sintered body, a disk-shaped compact (diameter: about 10 mm, thickness: about 1.2 mm) was produced in the same manner as in Example 1 using the above homogeneous mixture, and then fired using an electric furnace (firing temperature: 700 °C, firing time: 12 hours). No defects were found in the appearance of the obtained sintered body. Subsequently, when the relative density of the obtained sintered body was measured, it was 84.4%.

[0069] Comparative Example 1 LLZT particles, crystalline LGVO powder obtained in Synthesis Example 1, and crystalline LBO powder obtained in Synthesis Example 2 were weighed so that the mass ratio was 80:10:10, and the same operations as in Example 2 were performed except for using these materials, to obtain a homogeneous mixture (mixed powder) composed of LLZT, crystalline Li-Ge-V-O, and crystalline Li-B-O.

[0070] Next, in order to produce a sintered body, a disk-shaped compact (diameter: about 10 mm, thickness: about 1.2 mm) was produced in the same manner as in Example 1 using the above homogeneous mixture, and then fired using an electric furnace to obtain a sintered body. The firing temperature was 700 °C, 750 °C, or 800 °C, and the firing time was 12 hours for all cases. No defects were found in the appearance of the three types of sintered bodies obtained.

[0071] When the relative density of the obtained sintered body was measured, it was 74.5% at a firing temperature of 700 °C, 77.7% at a firing temperature of 750 °C, and 79.5% at a firing temperature of 800 °C.

Industrial Applicability

[0072] When the solid electrolyte composition of the present invention is fired, a sintered body with a high relative density can be obtained. Therefore, this sintered body can be suitably used, for example, as a solid electrolyte layer having high ionic conductivity in an all-solid-state battery. In addition, since the heat treatment temperature during the production of the sintered body can be set lower than the conventional method, for example, 700 °C, when manufacturing an all-solid-state battery by a method of integrally molding a precursor composite in which each layer made of these materials, namely, a positive electrode material, a solid electrolyte, and a negative electrode material, are sequentially laminated, an effect of suppressing defects in which the composition of the positive electrode layer, the solid electrolyte layer, or the negative electrode layer changes is expected.

Explanation of Reference Numerals

[0073] 10, 11: All-solid-state battery 20: Substrate 21: Positive electrode current collector 23: Positive electrode layer 25: Solid electrolyte layer 27: Negative electrode layer 29: Negative electrode current collector

Claims

1. (A) A garnet-type solid electrolyte containing Li, La, and Zr; (B) A composite oxide containing Li, Ge, and V; and (C) Li ３ BO ３ Or a precursor material thereof, and a solid electrolyte composition in which the component (B) is amorphous.

2. The solid electrolyte composition according to claim 1, wherein the component (A), the component (B), and the component (C) are integrated.

3. The solid electrolyte composition according to claim 2, which has a particulate shape.

4. When the total content of the component (A), the component (B), and the component (C) is 100% by mass, the content ratios thereof are 80 to 95% by mass, 3 to 15% by mass, and 2 to 10% by mass, respectively, for the solid electrolyte composition according to claim 1.

5. A method for producing the solid electrolyte composition according to claim 1, comprising: Mixing the garnet-type solid electrolyte, a precursor material BX of the composite oxide, and a precursor material CX of the Li ３ BO ３ And water to prepare a dispersion in which the garnet-type solid electrolyte is dispersed in an aqueous solution of the precursor material BX and the precursor material CX, and a step of removing water from the dispersion, in that order.

6. The method for producing a solid electrolyte composition according to claim 5, wherein the precursor material BX contains lithium hydroxide, germanium oxide, and vanadium oxide.

7. The method for producing a solid electrolyte composition according to claim 5, wherein the precursor material CX contains lithium hydroxide and boric acid.

8. A method for producing a sintered body, comprising: subjecting the solid electrolyte composition according to claim 1 to pressure molding to produce a molded product, and subjecting the molded product to heat treatment, in that order.

9. The method for manufacturing a sintered body according to claim 8, wherein the temperature of the heat treatment is 700°C to 800°C.

10. A sintered body obtained by the method for manufacturing a sintered body according to claim 8.

11. An all-solid-state battery including the sintered body according to claim 10.

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