Method for producing fluoride-based solid electrolyte and method for producing all-solid-state lithium ion battery

Abstract

Provided are a method for producing an oxyfluoride-based solid electrolyte having good ionic conductivity (bulk ionic conductivity) and a method for producing an all-solid-state lithium-ion battery. 【Solution means】A step of pulverizing and mixing raw materials to produce a raw material mixture 1, a step of putting the raw material mixture 1 into a firing container and firing it at 800 to 1200 °C to produce an oxide, adding two raw materials of LiF and LaF3 to the oxide, pulverizing and mixing them to produce a raw material mixture 2, and firing the raw material mixture 2 at 850 to 1000 °C in a firing container containing SiC, Si3N4, ZrO2 or C as a main component, thereby producing an oxyfluoride-based solid electrolyte having a lattice constant of 10.436 Å or more represented by the composition formula: Li 2-x La (1+x) / 3 M2O6F (wherein M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0). The method for producing an oxyfluoride-based solid electrolyte includes the steps of:

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an oxyfluoride-based solid electrolyte and a method for manufacturing an all-solid-state lithium-ion battery.

Background Art

[0002] With the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones in recent years, the development of batteries used as their power sources has been emphasized. Among these batteries, lithium-ion batteries have attracted attention from the viewpoint of high energy density. In addition, for lithium secondary batteries in large-scale applications such as power sources for in-vehicle use and load leveling, improvements in energy density and battery characteristics are required.

[0003] In addition, from the viewpoint of improving safety, as a lithium-ion battery that does not use an organic solvent as an electrolyte, a lithium-ion battery in which the entire battery is solidified using a solid electrolyte has attracted attention. As such a solid electrolyte used in a lithium-ion battery, an oxyfluoride-based solid electrolyte has been proposed.

[0004] The oxyfluoride-based solid electrolyte used in an all-solid-state lithium-ion battery is non-flammable, has high stability in the air, and has a higher ionic conductivity than general oxide-based solid electrolytes. Therefore, it is attracting attention as a component of a next-generation battery with high reliability, high output, and high cycle characteristics.

[0005] In particular, Li 2-x La (1+x) / 3 M2O6F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0) is attracting attention as a material that exhibits very high ionic conductivity. The ionic conductivity of the most famous garnet-type structure material of an oxide-based solid electrolyte material is at most about 1 mS / cm at room temperature, whereas the above oxyfluoride solid electrolyte material exhibits a very high ionic conductivity of up to 8 mS / cm.

[0006] Also, regarding conventional fluoride-based solid electrolytes, for example, in Patent Document 1, the composition formula is Aa 2-α Ab (1+α) / 3 B2O 7-β X β A solid electrolyte for a secondary battery including an oxide-based solid electrolyte having a pyrochlore structure represented by the formula, wherein Aa is an alkali metal, Ab contains at least a lanthanoid, B is a cation metal different from Aa and Ab, X is an anion capable of substituting for an O atom constituting the pyrochlore structure, in the composition formula, α is in the range of 0.6 < α < 2.0, β is in the range of 0 < β ≦ 1, and a solid electrolyte for a secondary battery including a defect structure and a method for manufacturing the same are disclosed.

[0007] Also, in Patent Document 2, a particulate core phase (101) and a shell phase (102) covering at least a part of the core phase are provided, and the shell phase is composed of one or more phases. The constituent material of the core phase is a composition formula Aa 2-α Ab (1+α) / 3 B2O 7-β X β (Aa: alkali metal, Ab: lanthanoid, B: cation metal, X: anion capable of substituting for O) including a pyrochlore-type solid electrolyte, the constituent material of the shell phase has a chemical composition different from that of the pyrochlore-type solid electrolyte, has a chemical composition containing Li, and contains a material having a melting point lower than that of the pyrochlore-type solid electrolyte. The pyrochlore-type solid electrolyte is in the range of 0.6 < α < 2.0 and 0 < β ≦ 1 in the composition formula, and the sum of the valences of the cations composed of Aa, Ab, and B and the anions composed of O and X is negative, and a solid electrolyte for a secondary battery including a defect structure is disclosed.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Conventionally, when synthesizing a fluorinated oxide solid electrolyte represented by the compositional formula: Li 2-x La (1+x) / 3 M2O6F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0), when using an alumina crucible or an alumina-containing crucible, which is a general firing container, the alumina component reacts with the material, and small cracks occur in the crucible. As a result, there has been a problem that Li or F in the reaction system volatilizes, or the lattice constant decreases due to the reaction between the fluorinated oxide solid electrolyte and moisture in the air, and the ionic conductivity decreases.

[0010] The present invention has been made to solve the above problems, and an object thereof is to provide a method for manufacturing a fluorinated oxide solid electrolyte having good ionic conductivity (bulk ionic conductivity) and a method for manufacturing an all-solid-state lithium-ion battery.

Means for Solving the Problems

[0011] The present invention completed based on the above findings is defined as follows. (1) A step of pulverizing and mixing raw materials to prepare a raw material mixture 1, A step of putting the raw material mixture 1 into a firing container and firing it at 800 to 1200 °C to produce an oxide, A step of adding two kinds of raw materials, LiF and LaF3, to the oxide, pulverizing and mixing them to prepare a raw material mixture 2, By firing the raw material mixture 2 in a firing container containing SiC, Si3N4, ZrO2 or C as a main component at 850 to 1000 °C, the compositional formula: Li 2-x La (1+x) / 3 M2O6F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0) A step of producing an oxyfluoride-based solid electrolyte having a lattice constant represented by 10.436 Å or more, and A method for producing an oxyfluoride-based solid electrolyte having (2) The method for producing an oxyfluoride-based solid electrolyte according to (1) above, wherein the firing container for the raw material mixture 2 contains SiC as a main component. (3) The method for producing an oxyfluoride-based solid electrolyte according to (1) or (2) above, wherein the firing of the raw material mixture 1 and / or the firing of the raw material mixture 2 are carried out in an atmosphere other than an inert atmosphere. (4) A method for producing an all-solid-state lithium-ion battery including a solid electrolyte layer, a positive electrode layer, and a negative electrode layer, using the oxyfluoride-based solid electrolyte produced by the method for producing an oxyfluoride-based solid electrolyte according to any one of (1) to (3) above.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a method for producing an oxyfluoride-based solid electrolyte having good ionic conductivity (bulk ionic conductivity) and a method for producing an all-solid-state lithium-ion battery. Here, ionic conductivity is roughly divided into "bulk conductivity" and "grain boundary conductivity". "Bulk conductivity" does not vary significantly if a high-quality material can be produced because it is inherent to the material. However, "grain boundary conductivity" may vary significantly depending on the method and accuracy of producing the sintered body. In the present invention, "ionic conductivity" means "bulk conductivity".

Brief Description of the Drawings

[0013]

Figure 1

Embodiments for Carrying Out the Invention

[0014] Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that design changes, improvements, etc. may be appropriately added based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention.

[0015] <Fluoride-based solid electrolyte> The fluoride-based solid electrolyte of this embodiment has a composition formula: Li 2-x La (1+x) / 3 M2O6F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0).

[0016] The fluoride-based solid electrolyte of this embodiment has a pyrochlore structure. The pyrochlore structure has a crystal structure in which metal atoms are arranged at the vertices of a tetrahedron, and each tetrahedral vertex is shared. The fluoride-based solid electrolyte of this embodiment contains La, which is a lanthanoid, in the pyrochlore structure, resulting in defects in the crystal structure and improved ionic conductivity.

[0017] In the above composition formula of the fluoride-based solid electrolyte of this embodiment, 0 ≦ x ≦ 1.0. Therefore, single-phase synthesis becomes easy. Also, defects occur in the crystal structure, and the ionic conductivity can be improved. In the above composition formula of the fluoride-based solid electrolyte of this embodiment, it is preferably 0.5 ≦ x ≦ 0.8.

[0018] The average particle size D50 (50% cumulative volume particle size D50) of the fluoride-based solid electrolyte of this embodiment is not particularly limited, and it may be 0.01 to 100 μm, may be 0.1 to 100 μm, or may be 0.1 to 50 μm.

[0019] The lattice constant of the fluoride-based solid electrolyte of this embodiment is 10.436 Å or more. When the lattice constant of the fluoride-based solid electrolyte is 10.436 Å or more, a sufficient Li conduction path is ensured, and good ionic conductivity can be obtained. The lattice constant of the fluoride-based solid electrolyte is more preferably 10.440 Å or more.

[0020] <Manufacturing method of fluoride-based solid electrolyte> The manufacturing method of the fluoride-based solid electrolyte of this embodiment will be described in detail below. First, weigh the raw materials of the fluoride-based solid electrolyte so as to have a predetermined composition inside a glove box in an inert gas atmosphere such as argon gas or nitrogen gas. Examples of each raw material used here are Li2CO3, La2O3, Nb2O5, etc.

[0021] Next, pulverize and mix the raw materials to produce a raw material mixture 1. The pulverization and mixing of the raw materials are not particularly limited, but for example, it is preferably carried out using a planetary ball mill. Put the above raw materials and zirconia beads with a diameter of 1 mm or less into the container (jar) of the planetary ball mill, and rotate and revolve the container to pulverize and mix the above raw materials. The revolution rotation speed of the planetary ball mill is preferably in the range of 100 rpm to 500 rpm.

[0022] Next, put the raw material mixture 1 into a firing container and fire it at 800 to 1200 °C for 2 to 6 hours to produce an oxide. The firing atmosphere of the raw material mixture 1 is not particularly limited, but it is preferably carried out under an inert gas atmosphere such as argon. Also, from the viewpoint of improving the production efficiency without the need for gas adjustment in a continuous furnace in particular, it is also preferable to carry out the firing in an atmosphere other than the inert atmosphere. As an atmosphere other than the inert atmosphere, for example, it can be carried out in an air atmosphere.

[0023] Next, add two kinds of raw materials, LiF and LaF3, to the oxide, and pulverize and mix them to produce a raw material mixture 2. The pulverization and mixing of the raw material mixture 2 are not particularly limited, but like the raw material mixture 1, it is preferably carried out using a planetary ball mill, for example.

[0024] Next, the raw material mixture 2 is fired in a firing container containing SiC, Si3N4, ZrO2 or C as the main component at 850 to 1000 °C for 2 to 6 hours to cause a fluorination reaction, so that the composition formula: Li 2-x La (1+x) / 3 M2O6F (wherein M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0), a fluoride-based solid electrolyte having a lattice constant of 10.436 Å or more can be produced.

[0025] In an embodiment of the present invention, a fired container containing SiC, Si3N4, ZrO2, or C as a main component means a fired container containing SiC, Si3N4, ZrO2, or C at a ratio of 90% by mass or more. Further, in an embodiment of the present invention, it is preferable that the fired container contains SiC, Si3N4, ZrO2, or C at a ratio of 95% by mass or more, and particularly preferably at a ratio of 99% by mass or more.

[0026] Composition formula: Li 2-x La (1+x) / 3 When synthesizing an oxyfluoride-based solid electrolyte represented by M2O6F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0), if an alumina crucible or an alumina-containing crucible, which is a general fired container, is used, the alumina component reacts with the material, and small cracks occur in the crucible. In contrast, in this embodiment, the raw material mixture 2 is placed in a fired container such as a crucible or a sheath containing SiC, Si3N4, ZrO2, or C as a main component and fired to cause a fluorination reaction. A fired container containing SiC, Si3N4, ZrO2, or C as a main component does not crack even when fired at 850 to 1000°C. Therefore, it is possible to suppress the volatilization of Li or F in the reaction system, or the reduction of the lattice constant and the decrease in ionic conductivity due to the reaction between the oxyfluoride-based solid electrolyte and moisture in the air.

[0027] The fired container contains SiC, Si3N4, ZrO2, or C as a main component as described above. Among these, in particular, the one containing SiC as a main component is preferable from the viewpoints that it can be used even in the air and its workability.

[0028] The firing atmosphere of the raw material mixture 2 is not particularly limited, but it is preferably carried out in an inert gas atmosphere such as argon. Further, from the viewpoint of improving the production efficiency by eliminating the need for gas adjustment in a continuous furnace in particular, it is also preferable to carry out the firing in an air atmosphere.

[0029] <All-solid-state lithium-ion battery> The all-solid-state lithium-ion battery according to an embodiment of the present invention includes a solid electrolyte layer, a positive electrode layer, and a negative electrode layer. The all-solid-state lithium-ion battery according to an embodiment of the present invention can be configured as shown in FIG. 1 using a solid electrolyte layer, a positive electrode layer, and a negative electrode layer.

[0030] (Solid electrolyte layer) The solid electrolyte layer of the present embodiment is formed of the above-described fluoride-based solid electrolyte of the present embodiment. The average thickness of the solid electrolyte layer is not particularly limited and can be appropriately designed according to the purpose. The average thickness of the solid electrolyte layer of the present embodiment may be, for example, 50 μm to 500 μm, or may be 50 μm to 100 μm.

[0031] The method for forming the solid electrolyte layer of the present embodiment is not particularly limited and can be appropriately selected according to the purpose. Examples of the method for forming the solid electrolyte layer of the present embodiment include sputtering using the target material of the solid electrolyte of the present embodiment described above, or a method of compression molding the solid electrolyte of the present embodiment described above.

[0032] (Positive electrode layer) The positive electrode layer of the present embodiment is formed by laminating a positive electrode composite material obtained by mixing a known positive electrode active material for a lithium-ion battery and the above-described fluoride-based solid electrolyte of the present embodiment or another solid electrolyte. The content of the positive electrode active material in the positive electrode layer is preferably, for example, 50% by mass or more and 99% by mass or less, and more preferably 60% by mass or more and 90% by mass or less.

[0033] Examples of the known positive electrode active material for a lithium-ion battery include a composition formula 2: Li a Ni b Co c Mn dIt contains a positive electrode active material represented by O2 (in Composition Formula 2, 1.00 ≦ a ≦ 1.08, 0.60 ≦ b ≦ 0.90, and b + c + d = 1.0). When the positive electrode active material of this embodiment is a high-nickel NCM positive electrode active material with a high Ni ratio of 0.60 to 0.90 as shown in the above Composition Formula 2, generally the capacity of all-solid-state lithium-ion batteries increases. Also, from such a perspective, in the above Composition Formula 2, it is more preferable that 0.80 ≦ b ≦ 0.90.

[0034] The positive electrode composite material may further contain a conductive assistant. As the conductive assistant, a carbon material, a metal material, or a mixture thereof can be used. The conductive assistant may contain, for example, at least one element selected from the group consisting of carbon, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osmium, rhodium, tungsten, and zinc. The conductive assistant is preferably a simple carbon with high conductivity, carbon, or a simple metal containing nickel, copper, silver, cobalt, magnesium, lithium, gold, ruthenium, platinum, niobium, osmium, or rhodium, or a mixture or compound thereof. As the carbon material, for example, carbon black such as ketjen black, acetylene black, denka black, thermal black, channel black, graphite, carbon fiber, activated carbon, etc. can be used.

[0035] The average thickness of the positive electrode layer of all-solid-state lithium-ion batteries is not particularly limited and can be appropriately designed according to the purpose. The average thickness of the positive electrode layer of all-solid-state lithium-ion batteries may be, for example, 1 μm to 100 μm, or may be 1 μm to 10 μm.

[0036] The method for forming the positive electrode layer of all-solid-state lithium-ion batteries is not particularly limited and can be appropriately selected according to the purpose. Examples of the method for forming the positive electrode layer of all-solid-state lithium-ion batteries include a method of compression molding a positive electrode active material for all-solid-state lithium-ion batteries.

[0037] (Negative electrode layer) The negative electrode layer of the all-solid-state lithium-ion battery may be formed by laminating known negative electrode active materials for all-solid-state lithium-ion batteries. Further, the negative electrode layer may be formed by laminating a negative electrode composite material obtained by mixing a known negative electrode active material for all-solid-state lithium-ion batteries and a solid electrolyte. The content of the negative electrode active material in the negative electrode layer is preferably, for example, 10% by mass or more and 99% by mass or less, and more preferably 20% by mass or more and 90% by mass or less.

[0038] Similar to the positive electrode layer, the negative electrode layer may contain a conductive auxiliary agent. As the conductive auxiliary agent, the same materials as those described for the positive electrode layer can be used. Examples of the negative electrode active material include carbon materials, specifically, artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon, etc., or a mixture thereof can be used. Further, as the negative electrode material, for example, metals themselves such as metallic lithium, metallic indium, metallic aluminum, and metallic silicon, or alloys combined with other elements and compounds can be used.

[0039] The average thickness of the negative electrode layer of the all-solid-state lithium-ion battery is not particularly limited and can be appropriately designed according to the purpose. The average thickness of the negative electrode layer of the all-solid-state lithium-ion battery may be, for example, 1 μm to 100 μm, or may be 1 μm to 10 μm.

[0040] The method for forming the negative electrode layer of the all-solid-state lithium-ion battery is not particularly limited and can be appropriately selected according to the purpose. Examples of the method for forming the negative electrode layer of the all-solid-state lithium-ion battery include a method of compression molding negative electrode active material particles and a method of vapor-depositing the negative electrode active material.

[0041] Other members constituting the lithium-ion battery are not particularly limited and can be appropriately selected according to the purpose, and examples include a positive electrode current collector, a negative electrode current collector, and a battery case.

[0042] The size and structure of the positive current collector are not particularly limited and can be appropriately selected according to the purpose. Examples of the material of the positive current collector include die steel, stainless steel, aluminum, aluminum alloy, titanium alloy, copper, gold, nickel, and the like. Examples of the shape of the positive current collector include foil shape, plate shape, mesh shape, and the like. The average thickness of the positive current collector may be, for example, 10 μm to 500 μm, or may be 50 μm to 100 μm.

[0043] The size and structure of the negative current collector are not particularly limited and can be appropriately selected according to the purpose. Examples of the material of the negative current collector include die steel, gold, indium, nickel, copper, stainless steel, and the like. Examples of the shape of the negative current collector include foil shape, plate shape, mesh shape, and the like. The average thickness of the negative current collector may be, for example, 10 μm to 500 μm, or may be 50 μm to 100 μm.

[0044] The battery case is not particularly limited and can be appropriately selected according to the purpose. Examples include known laminate films that can be used in conventional all-solid-state batteries. Examples of the laminate film include resin laminate films, films obtained by vapor-depositing a metal on a resin laminate film, and the like. The shape of the battery is not particularly limited and can be appropriately selected according to the purpose. Examples include cylindrical, rectangular, button-shaped, coin-shaped, flat-shaped, and the like.

Examples

[0045] Examples are provided below to better understand the present invention and its advantages, but the present invention is not limited to these examples.

[0046] <1. Preparation of Acid Fluoride-Based Solid Electrolyte> (Example 1) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3 and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and they were mixed using an automatic mortar to prepare raw material mixture 1. Next, raw material mixture 1 was placed in an alumina crucible and fired at 1200 °C (intermediate synthesis temperature) for 4 hours in an air atmosphere to prepare an oxide. Next, two raw materials of LiF and LaF3 were added to the oxide, and they were pulverized and mixed using an automatic mortar to prepare raw material mixture 2. Next, raw material mixture 2 was fired in a crucible containing SiC as a main component at the content rate shown in Table 1 at 1000 °C (fluorination temperature) for 6 hours in a nitrogen atmosphere to cause a fluorination reaction, thereby producing a fluorooxide-based solid electrolyte.

[0047] (Example 2) In a glove box under an argon atmosphere, Li2CO3, La2O3 and Nb 2 O 5 of each raw material were weighed, and they were mixed using an automatic mortar to prepare raw material mixture 1. Next, raw material mixture 1 was placed in an alumina crucible and fired at 1200 °C (intermediate synthesis temperature) for 4 hours in an air atmosphere to prepare an oxide. Next, two raw materials of LiF and LaF3 were added to the oxide, and they were pulverized and mixed using an automatic mortar to prepare raw material mixture 2. Next, raw material mixture 2 was fired in a crucible containing SiC as a main component at the content rate shown in Table 1 at 900 °C (fluorination temperature) for 6 hours in a nitrogen atmosphere to cause a fluorination reaction, thereby producing a fluorooxide-based solid electrolyte.

[0048] (Example 3) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3 and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and they were mixed using a planetary ball mill to prepare raw material mixture 1. Next, the raw material mixture 1 was placed in a crucible made of Al2O3 and fired at 1000 °C (intermediate synthesis temperature) for 4 hours in an air atmosphere to produce an oxide. Next, two raw materials, LiF and LaF3, were added to the oxide, and pulverized and mixed using an automatic mortar to produce a raw material mixture 2. Next, the raw material mixture 2 was fired at 1000 °C (fluorination temperature) for 6 hours in a crucible containing SiC as the main component at the content rates shown in Table 1 under a nitrogen atmosphere to cause a fluorination reaction, thereby producing a fluoro-oxide-based solid electrolyte.

[0049] (Example 4) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3, and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and mixed using an automatic mortar to produce a raw material mixture 1. Next, the raw material mixture 1 was placed in a crucible made of Al2O3 and fired at 800 °C (intermediate synthesis temperature) for 4 hours in an air atmosphere to produce an oxide. Next, two raw materials, LiF and LaF3, were added to the oxide, and pulverized and mixed using an automatic mortar to produce a raw material mixture 2. Next, the raw material mixture 2 was fired at 1000 °C (fluorination temperature) for 6 hours in a crucible containing SiC as the main component at the content rates shown in Table 1 under a nitrogen atmosphere to cause a fluorination reaction, thereby producing a fluoro-oxide-based solid electrolyte.

[0050] (Example 5) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3, and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and mixed using an automatic mortar to produce a raw material mixture 1. Next, the raw material mixture 1 was placed in a crucible made of Al2O3 and fired at 1200 °C (intermediate synthesis temperature) for 4 hours in an air atmosphere to produce an oxide. Next, two raw materials, LiF and LaF3, were added to the oxide, and pulverized and mixed using an automatic mortar to produce a raw material mixture 2. Next, the raw material mixture 2 was fired in a crucible containing ZrO2 as the main component at the content rates shown in Table 1 for 6 hours at 1000 °C (fluorination temperature) under a nitrogen atmosphere to cause a fluorination reaction, thereby producing an oxyfluoride-based solid electrolyte.

[0051] (Example 6) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3, and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and they were mixed using an automatic mortar to produce a raw material mixture 1. Next, the raw material mixture 1 was placed in an alumina crucible and fired at 1200 °C (intermediate synthesis temperature) for 4 hours under an air atmosphere to produce an oxide. Next, two raw materials of LiF and LaF3 were added to the oxide, and they were pulverized and mixed using an automatic mortar to produce a raw material mixture 2. Next, the raw material mixture 2 was fired in a crucible containing C (carbon) as the main component at the content rates shown in Table 1 for 6 hours at 1000 °C (fluorination temperature) under an argon atmosphere to cause a fluorination reaction, thereby producing an oxyfluoride-based solid electrolyte.

[0052] (Comparative Example 1) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3, and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and they were mixed using an automatic mortar to produce a raw material mixture 1. Next, the raw material mixture 1 was placed in an alumina crucible and fired at 1200 °C (intermediate synthesis temperature) for 4 hours under an air atmosphere to produce an oxide. Next, two raw materials of LiF and LaF3 were added to the oxide, and they were pulverized and mixed using an automatic mortar to produce a raw material mixture 2. Next, the raw material mixture 2 was fired in a crucible containing Al2O3 as the main component at the content rates shown in Table 1 for 6 hours at 1000 °C (fluorination temperature) under a nitrogen atmosphere to cause a fluorination reaction, thereby producing an oxyfluoride-based solid electrolyte.

[0053] (Comparative Example 2) In a glove box under an argon atmosphere, each raw material of Li2CO3, La2O3, and Nb2O5 was weighed so that the raw material charging composition became the stoichiometric composition of the target compound, and they were mixed using an automatic mortar to prepare a raw material mixture 1. Next, the raw material mixture 1 was placed in an alumina crucible and fired at 800 °C (intermediate synthesis temperature) for 4 hours under an air atmosphere to prepare an oxide. Next, two raw materials of LiF and LaF3 were added to the oxide, and they were pulverized and mixed using an automatic mortar to prepare a raw material mixture 2. Next, the raw material mixture 2 was fired in a crucible containing Al2O3 as a main component at a content rate shown in Table 1 at 1000 °C (fluorination temperature) for 6 hours under a nitrogen atmosphere to cause a fluorination reaction, thereby preparing an oxyfluoride-based solid electrolyte.

[0054] <2. Composition Evaluation of Oxyfluoride-Based Solid Electrolyte> 0.5 g of each oxyfluoride-based solid electrolyte obtained in Examples 1 to 6 and Comparative Examples 1 to 2 was weighed, solubilized using various acids, and then subjected to composition analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES) "PS7800" manufactured by Hitachi High-Tech Corporation. The analysis results are shown in Table 1.

[0055] <3. XRD Evaluation of Solid Electrolyte (Lattice Constant Evaluation)> For each solid electrolyte sample obtained in Examples 1 to 6 and Comparative Examples 1 to 2, XRD evaluation was performed under the conditions shown below. · X-ray diffractometer: SmartLab manufactured by Rigaku Corporation · Light source: CuKα ray · Voltage: 40 kV · Current: 30 mA · Detector: One-dimensional detector · Measurement range: 2θ = 5 to 100 degree · Step width: 0.1 degree · Scan rate: 10 degree / min Here, regarding the X-ray diffraction patterns according to Examples 1 to 6 and Comparative Examples 1 to 2 obtained, Rietveld analysis was performed to calculate the lattice constant of each sample. The evaluation results are shown in Table 1.

[0056] <3. Evaluation of Bulk Ion Conductivity of Fluoride-Based Solid Electrolytes> 0.5 g of the powder of each fluoride-based solid electrolyte obtained in Examples 1 to 6 and Comparative Examples 1 to 2 was pressed at a pressure of 370 MPa to form a plate shape, and then the plate formed was placed in a crucible made of Al2O3 or a crucible made of SiC, and fired at 1000 °C for 6 hours in a nitrogen atmosphere to produce a sintered body for measurement. Gold was sputtered on both surfaces of the above-mentioned sintered body to produce a pellet having a gold electrode with a diameter of less than 10 mm. Using this pellet, at 30 °C, an AC impedance measurement from 20 Hz to 100 MHz was performed using an E4990A manufactured by Keysight with an applied voltage of 100 mV and open-short correction. The arc appearing on the high-frequency side of the Cole-Cole plot obtained by the AC impedance measurement was analyzed to obtain the migration resistance of Li ions in the bulk of the sample. Next, based on the following formula, the ion conductivity (bulk ion conductivity) was obtained from the migration resistance of the Li ions, the thickness and area of the solid electrolyte portion of the pellet used for the measurement. Ion conductivity (mS / cm) = thickness of the solid electrolyte portion of the pellet (cm) × 1000 / [(migration resistance of Li ions (Ω)) × (area of the solid electrolyte portion of the pellet (cm 2 ))] The evaluation results are shown in Table 1.

[0057] <4. Evaluation of Relative Density of Fluoride-Based Solid Electrolytes> Using the thickness and area of the solid electrolyte portion of the pellet produced in the above-mentioned "Evaluation of Bulk Ion Conductivity of Fluoride-Based Solid Electrolytes" and the mass of the pellet, the relative density was obtained from the following formula. Dimensional density (g / cm 3 ) = mass of the pellet (g) / [(thickness of the solid electrolyte portion of the pellet (cm)) × (area of the solid electrolyte portion of the pellet (cm 2 ))] Relative density (%) = (dimensional density (g / cm 3 )) / (theoretical density of the fluoride-based solid electrolyte (g / cm 3))×100 The evaluation results are shown in Table 1.

[0058] [Table 1]

[0059] (Evaluation results) In Examples 1 to 6, fluoride-based solid electrolytes having good ionic conductivity were obtained in all cases. On the other hand, for the fluoride-based solid electrolytes according to Comparative Examples 1 and 2, since the raw material mixture 2 was put into a crucible made of Al2O3 and fired, the ionic conductivity was poor.

[0060] According to one embodiment of the present invention, since it is possible to provide a method for manufacturing a fluoride-based solid electrolyte having good ionic conductivity and a method for manufacturing an all-solid-state lithium-ion battery, it leads to the spread of non-fossil energy, reduces the usage amount of fossil energy such as oil and gas that occupies a large part of current energy generation, and may lead to the suppression of global warming. In addition, substances with low environmental impact such as lithium, carbon, manganese, nickel, and cobalt are used as main materials, and no harmful substances such as cadmium, lead, and mercury are used, so there is a possibility of reducing the environmental load. Therefore, one embodiment of the present invention may contribute to Goal 7, "Ensure access for all people to affordable, reliable, and sustainable modern energy," Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation," and Goal 12, "Ensure sustainable consumption and production patterns," which are led by the United Nations' Sustainable Development Goals (SDGs).

Claims

1. A step of pulverizing and mixing raw materials to produce a raw material mixture 1; A step of placing the raw material mixture 1 in a firing container and firing it at 800 to 1200°C to produce an oxide; Add two raw materials, LiF and LaF, to the oxide, and pulverize and mix them to produce a raw material mixture 2. 3 The step of adding two kinds of raw materials of The raw material mixture 2 is fired at 850 to 1000 °C in a fired container containing SiC, Si 3 N 4 , ZrO 2 or C as a main component, whereby the composition formula: Li 2-x La (1+x) / 3 M 2 O 6 F (wherein M is at least one of Nb and Ta, and 0 ≤ x ≤ 1.0). A step of producing an oxyfluoride-based solid electrolyte having a lattice constant represented by of 10.436 Å or more; A method for producing an oxyfluoride-based solid electrolyte, comprising:

2. The method for producing an oxyfluoride-based solid electrolyte according to Claim 1, wherein the firing container for the raw material mixture 2 contains SiC as a main component.

3. The method for producing an oxyfluoride-based solid electrolyte according to Claim 1, wherein the firing of the raw material mixture 1 and / or the firing of the raw material mixture 2 is carried out in an atmosphere other than an inert atmosphere.

4. A method for producing an all-solid-state lithium-ion battery, comprising producing an oxyfluoride-based solid electrolyte by the method for producing an oxyfluoride-based solid electrolyte according to any one of Claims 1 to 3, and forming a solid electrolyte layer with the produced oxyfluoride-based solid electrolyte, the all-solid-state lithium-ion battery comprising the solid electrolyte layer, a positive electrode layer, and a negative electrode layer.

5. A method for producing an all-solid-state lithium-ion battery, comprising forming a solid electrolyte layer with an oxyfluoride-based solid electrolyte having a lattice constant represented by the composition formula: Li 2-x La (1+x) / 3 M 2 O 6 F (where M is at least one of Nb and Ta, and 0 ≦ x ≦ 1.0) of 10.436 Å or more, the all-solid-state lithium-ion battery comprising the solid electrolyte layer, a positive electrode layer, and a negative electrode layer.

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