Method for producing garnet-type oxide solid electrolyte

Abstract

Provided is a method for manufacturing a garnet-type oxide solid electrolyte by pressure molding a Li7La3Zr2O12 powder having a median diameter (D50) of 0.02-0.2 µm to obtain an intermediate, heating the intermediate at a temperature of 950-1050°C for two to seven hours, and then cooling to room temperature over a period of four hours or longer to obtain a first garnet-type oxide solid electrolyte.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a garnet-type oxide solid electrolyte. [Background technology]

[0002] In recent years, all-solid-state batteries have been proposed as next-generation batteries for automobiles and electronic devices. All-solid-state batteries are secondary batteries with a solid electrolyte interposed between a positive electrode and a negative electrode. Known solid electrolytes used in all-solid-state batteries include sulfide-based solid electrolytes and oxide-based solid electrolytes. Generally, sulfide-based solid electrolytes are softer than oxide-based solid electrolytes, resulting in lower interfacial resistance and higher ionic conductivity. However, sulfide-based solid electrolytes are less chemically stable than oxide-based solid electrolytes and generate hydrogen sulfide gas if they come into contact with air. On the other hand, oxide-based solid electrolytes are more chemically stable than sulfide-based solid electrolytes, but are harder, making it difficult to reduce interfacial resistance and resulting in lower ionic conductivity.

[0003] The oxide-based solid electrolyte is a perovskite-type La 1-3x Li 3x TiO3, NASICON type Li 1+x Al x Ti 2-x (PO4)3, garnet-type Li7La3Zr2O 12 (hereinafter, sometimes referred to as "LLZO"). LLZO is highly stable against lithium metal and is considered a promising oxide solid electrolyte for all-solid-state batteries. However, LLZO has a property that lithium carbonate easily forms on its surface. Lithium carbonate formed on the surface of LLZO increases the interfacial resistance of the garnet-type oxide solid electrolyte. The increase in interfacial resistance causes a decrease in ionic conductivity. Patent Document 1 discloses a method for reducing interfacial resistance by polishing a garnet-type oxide solid electrolyte to remove lithium carbonate formed on the surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-205284 Summary of the Invention

[0005] A method for producing a garnet-type oxide solid electrolyte according to one embodiment of the present disclosure includes the steps of: Li7La3Zr2O with a median diameter (D50) of 0.02 to 0.2 μm 12 (LLZO) powder is pressed to obtain an intermediate; The intermediate product is heated at 950 to 1050° C. for 2 to 7 hours, and then cooled to room temperature over 4 hours or more to obtain a first garnet-type oxide solid electrolyte. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a graph showing the relationship between the heating time in the heating / cooling step and the ionic conductivity of a garnet-type oxide solid electrolyte. [Figure 2] 1 is a graph showing the relationship between the heating temperature in the heating / cooling step and the ionic conductivity in garnet-type oxide solid electrolytes made from LLZO powders having different median diameters (D50). DETAILED DESCRIPTION OF THE INVENTION

[0007] <Problems to be Solved by the Invention of the Present Disclosure> As described above, oxide-based solid electrolytes have lower ionic conductivity than sulfide-based solid electrolytes. Furthermore, the ionic conductivity of garnet-type oxide solid electrolytes is reduced due to lithium carbonate and other substances formed on the surface. Therefore, a method for producing a garnet-type oxide solid electrolyte with high ionic conductivity is desired.

[0008] The method disclosed in Patent Document 1 is a method for increasing the ionic conductivity of a garnet-type oxide solid electrolyte by removing lithium carbonate formed on the surface of the garnet-type oxide solid electrolyte through a polishing process. However, it is difficult to apply the polishing method described in Patent Document 1 to a garnet-type oxide solid electrolyte having an undulating surface. Therefore, when applying the polishing process, the shape of the garnet-type oxide solid electrolyte to be manufactured is limited. Therefore, there is a need for a method for manufacturing a garnet-type oxide solid electrolyte that can easily remove impurities such as lithium carbonate from garnet-type oxide solid electrolytes of various shapes.

[0009] <Effects of the Invention of the Present Disclosure> According to the invention of the present disclosure, there is provided a method for producing a garnet-type oxide solid electrolyte, which can be easily adapted to garnet-type oxide solid electrolytes of various shapes and can produce a garnet-type oxide solid electrolyte with high ionic conductivity.

[0010] <Summary of the embodiments of the present disclosure> Below, an outline of the embodiments of the present disclosure will be listed and described. (1) The method for producing a garnet-type oxide solid electrolyte of the present disclosure is to produce Li7La3Zr2O having a median diameter (D50) of 0.02 to 0.2 μm. 12 (LLZO) powder is pressed to obtain an intermediate; The intermediate product is heated at 950 to 1050° C. for 2 to 7 hours, and then cooled to room temperature over 4 hours or more to obtain a first garnet-type oxide solid electrolyte.

[0011] The manufacturing method described in (1) above can manufacture garnet-type oxide solid electrolytes with high ionic conductivity and various shapes.

[0012] (2) In the manufacturing method described in (1) above, the first garnet-type oxide solid electrolyte is brought into contact with at least one selected from an organic plastic ionic crystal and an ionic liquid to obtain a second garnet-type oxide solid electrolyte.

[0013] The manufacturing method described in (2) above can manufacture a second garnet-type oxide solid electrolyte having higher ionic conductivity.

[0014] (3) In the manufacturing method according to (1) or (2), the LLZO powder is compressed under a pressure of 72 MPa or more to obtain the intermediate.

[0015] The manufacturing method described in (3) above can ensure sufficient hardness of the intermediate, so that the shape of the intermediate can be maintained.

[0016] <Details of the embodiment of the present disclosure> Hereinafter, embodiments of the present disclosure will be described. It should be noted that in this disclosure, the embodiments of the invention should be considered to be illustrative in all respects and not restrictive. The scope of the rights of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

[0017] The method for producing a garnet-type oxide solid electrolyte according to the present disclosure includes the steps of: 1) Li7La3Zr2O with a median diameter (D50) of 0.02 to 0.2 μm 12 (LLZO) A ​​pressing process in which powder is pressed to obtain an intermediate; 2) a heating and cooling step of heating the intermediate at 950 to 1050°C for 2 to 7 hours and then cooling it to room temperature over 4 hours or more to obtain a first garnet-type oxide solid electrolyte; Includes. Furthermore 3) a contacting step of contacting the first garnet-type oxide solid electrolyte with at least one selected from an organic plastic ionic crystal and an ionic liquid to obtain a second garnet-type oxide solid electrolyte; The above 1) pressure molding step, 2) heating and cooling step, and 3) contacting step will be described below in order.

[0018] 1) Pressure molding process First, in the method for producing a garnet-type oxide solid electrolyte of the present disclosure, an intermediate is obtained by pressure-molding an LLZO powder having a median diameter (D50) of 0.02 to 0.2 μm. The median diameter (D50) is a value measured by a laser diffraction / scattering method in accordance with JIS Z 8825:2013.

[0019] The LLZO powder having a median diameter (D50) of 0.02 to 0.2 μm may be a commercially available LLZO powder, or may be an LLZO powder prepared to the above-mentioned predetermined median diameter by pulverizing an LLZO powder having a median diameter (D50) exceeding 0.2 μm. The LLZO powder may be pulverized by any known method without any particular limitation. Specific examples of pulverization methods include pulverization methods using a bead mill, a ball mill, a jet mill, or the like. The LLZO powder having the above-mentioned predetermined median diameter can be obtained, for example, by pulverizing a commercially available LLZO powder having a median diameter (D50) exceeding 0.2 μm in isopropanol using a bead mill to obtain an isopropanol suspension, and then removing the isopropanol using an evaporator.

[0020] The pressure molding may be any known pressure molding method used in the production of solid electrolytes, and is not particularly limited. An example of a process including known pressure molding is a process of introducing LLZO powder having the predetermined median diameter into a powder molding machine and then uniaxially pressing the powder using a hydraulic press. In the uniaxial pressing, the pressure used to obtain the LLZO powder intermediate is preferably 72 MPa or higher. An intermediate formed under pressure conditions of 72 MPa or higher has sufficient hardness. Any high pressure may be used to obtain the LLZO powder intermediate. The upper limit of the pressure used to obtain the LLZO powder intermediate is limited by the upper limit of the pressure that can be applied by the pressurizing device used in the hydraulic press, and is, for example, 650 MPa or lower, but may be higher. This allows the shape of the intermediate to be maintained throughout the subsequent heating / cooling process and contacting process, which will be described later.

[0021] 2)Heating and cooling process In the method for producing a garnet-type oxide solid electrolyte of the present disclosure, the intermediate is heated at 950 to 1050°C for 2 to 7 hours, and then cooled to room temperature over 4 hours or more to obtain a first garnet-type oxide solid electrolyte. The heating and cooling step can be performed using a known firing furnace used in the production of solid electrolytes. The treatment of the intermediate at 950 to 1050°C for 2 to 7 hours is intended to remove impurities present in the intermediate, such as lithium carbonate and lithium hydroxide.

[0022] The heating temperature in the heating and cooling step is 950 to 1050°C. The heating time in the heating and cooling step is 2 to 7 hours, preferably 3 to 6 hours. Here, the heating temperature of 950°C or higher and the heating time of 2 hours or longer lead to sufficient removal of impurities from the LLZO powder intermediate. The heating temperature of 1050°C or lower and the heating time of 7 hours or shorter reduce energy consumption due to continuous heating, thereby reducing the manufacturing cost of the manufacturing method of the present disclosure.

[0023] The LLZO powder intermediate that has undergone the heat treatment described above is cooled to room temperature over a period of 4 hours or more to form a first garnet-type oxide solid electrolyte. Here, room temperature is 5 to 35°C. The cooling is performed, for example, by turning off the power to the furnace and allowing the temperature inside the furnace to drop to room temperature over a period of 4 hours or more by natural cooling. The cooling time to room temperature is preferably 4 to 8 hours. A cooling time of 8 hours or less shortens the production lead time, thereby improving the production efficiency of the production method of the present disclosure. Furthermore, the first garnet-type oxide solid electrolyte obtained by the production method of the present disclosure, which includes a heating and cooling step having the above-mentioned combination of heating temperature, heating time, and cooling time, has high ionic conductivity.

[0024] 3) Contact process The second garnet-type oxide solid electrolyte manufacturing method of the present disclosure is a method for obtaining a second garnet-type oxide solid electrolyte by contacting the first garnet-type oxide solid electrolyte with at least one selected from organic plastic ionic crystals and an ionic liquid (hereinafter, sometimes referred to as "organic plastic ionic crystals, etc."). The organic plastic ionic crystals, etc. can form an ion conduction path. Therefore, by contacting the first garnet-type oxide solid electrolyte with the organic plastic ionic crystals, etc., the internal resistance and interfacial resistance of the second garnet-type oxide solid electrolyte are reduced. Furthermore, by contacting the first garnet-type oxide solid electrolyte with the organic plastic ionic crystals, etc., the second garnet-type oxide solid electrolyte is coated with the organic plastic ionic crystals, etc. This prevents lithium carbonate from being formed on the surface of the first garnet-type oxide solid electrolyte. As a result, the second garnet-type oxide solid electrolyte has high ionic conductivity. From the viewpoint of coating the surface of the first garnet-type oxide solid electrolyte, it is preferable to bring the ionic liquid into contact with the organic plastic ionic crystals, which leads to obtaining a second garnet-type oxide solid electrolyte having higher ionic conductivity.

[0025] The method for achieving contact between the first garnet-type oxide solid electrolyte and the organic plastic ionic crystals, etc., is not particularly limited as long as it is a method that can impregnate the first garnet-type oxide solid electrolyte with the organic plastic ionic crystals, etc. Examples of the method for achieving the contact include immersing the first garnet-type oxide solid electrolyte in the organic plastic ionic crystals, etc., or dropping the organic plastic ionic crystals, etc. onto the first garnet-type oxide solid electrolyte.

[0026] The organic plastic ionic crystals are not particularly limited as long as they are known organic plastic ionic crystals that can be used in lithium secondary batteries. Examples of the organic plastic ionic crystals include aliphatic quaternary ammonium salts consisting of perfluoro anions, such as N,N-diethyl-N-methyl-N-propylammonium trifluoromethyl trifluoroborate (N 2、2、1、3 [BF3CF3]) analogue, N-ethyl-N-methyl-pyrrolidinium bisfluorosulfonylamide (Py 1、2 [FSA] analogues, etc. From the viewpoint of electrochemical stability, the organic plastic ionic crystals are 2、2、1、3 [BF3CF3] is preferred.

[0027] The ionic liquid is not particularly limited as long as it is a known ionic liquid that can be used in lithium secondary batteries. Examples of the ionic liquid include N-methyl-N-propylpyrrolidinium bisfluorosulfonylamide (Py 1、3 [FSA]) and N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonylamide) (Py 1、3 [TFSA]), N-ethyl-N-methylimidazolium bisfluorosulfonylamide (]EMI[FSA]). From the electrochemical point of view, the above ionic liquids are Py 1、3 [FSA] is preferred.

[0028] Each step in the method for producing a garnet-type oxide solid electrolyte of the present disclosure can be performed in a dry chamber or a glove box. In particular, it is preferable that the heating / cooling step and the contacting step be performed in a dry chamber. This prevents lithium carbonate or lithium hydroxide from being formed on the surface of the first garnet-type oxide solid electrolyte due to a reaction between the first garnet-type oxide solid electrolyte and carbon dioxide or water. It is preferable that the dew point of the dry chamber be −50° C. or lower, and that the environment of the glove box be −70° C. or lower under an inert gas atmosphere. [Example]

[0029] Next, the present invention will be described in more detail based on examples, but the present invention is not limited to only these examples.

[0030] 1.Raw materials used (LLZO powder) LLZO powder median diameter (D50) 0.1 μm LLZO powder, median diameter (D50) 1 μm (manufactured by Toshima Manufacturing Co., Ltd.) LLZO powder, median diameter (D50) 8.9 μm (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) LLZO powder, median diameter (D50) 10 μm (manufactured by Toshima Manufacturing Co., Ltd.)

[0031] (LLZO powder with a median diameter (D50) of 0.1 μm) The LLZO isopropanol suspension was prepared by grinding LLZO powder with a median diameter (D50) of 1 μm (manufactured by Toshima Manufacturing Co., Ltd.) in isopropanol using a bead mill (Easy Nano (RMB type) (manufactured by Imex Co., Ltd.)) with ZrO2 media diameter of 0.1 mm. LLZO powder with a median diameter (D50) of 0.1 μm was obtained by removing the isopropanol from the LLZO isopropanol suspension using an evaporator.

[0032] 2. Pressure molding process 1) Obtaining intermediate 1 Intermediate 1 was obtained by placing 60 mg of LLZO powder with a median diameter (D50) of 0.1 μm into a powder molding machine with an inner diameter of 10 mm in a dry chamber with a dew point of -50°C or less, and then uniaxially pressing the LLZO powder with a median diameter (D50) of 0.1 μm at 433 MPa using a hydraulic press. The diameter of Intermediate 1 is 10 mm.

[0033] 2 ) Acquisition of intermediate 2 Intermediate 2 was produced using LLZO powder with a median diameter (D50) of 1 μm. Intermediate 2 was obtained by processing in the same manner as for obtaining Intermediate 1 described above, except that LLZO powder with a median diameter (D50) of 1 μm was used instead of LLZO powder with a median diameter (D50) of 0.1 μm. The diameter of Intermediate 2 is 10 mm.

[0034] 3) Obtaining intermediate 3 Intermediate 3 was produced using LLZO powder with a median diameter (D50) of 10 μm. Intermediate 3 was obtained by processing in the same manner as for obtaining Intermediate 1 described above, except that LLZO powder with a median diameter (D50) of 10 μm was used instead of LLZO powder with a median diameter (D50) of 0.1 μm. The diameter of Intermediate 3 is 10 mm.

[0035] 3.Heating and cooling process 1) Preparation of the first garnet-type oxide solid electrolyte 1 The first garnet-type oxide solid electrolyte 1 was obtained by heating the intermediate 1 in a firing furnace under the conditions described in the "Effect of Heating Temperature on Ionic Conductivity" section below, and then cooling it to room temperature in the firing furnace over 2 to 4 hours. The diameter of the first garnet-type oxide solid electrolyte 1 was 8 mm to 9.5 mm, which was slightly smaller than before firing.

[0036] 2) Obtaining the first garnet-type oxide solid electrolyte 2 The first garnet-type oxide solid electrolyte 2 was produced using the above-mentioned intermediate 2. The first garnet-type oxide solid electrolyte 2 was obtained by treating in the same manner as in the above-mentioned "Obtaining Garnet-Type Oxide Solid Electrolyte 1", except that the above-mentioned intermediate 2 was used and heating was performed under the conditions of "Effect of Heating Time on Ion Conductivity" and "Effect of Heating Temperature on Ion Conductivity" described below. The diameter of the first garnet-type oxide solid electrolyte 2 was 8 mm to 9.5 mm, which was slightly smaller than before firing.

[0037] 3) Obtaining the first garnet-type oxide solid electrolyte 3 The first garnet-type oxide solid electrolyte 3 was produced using the above-mentioned intermediate 3. The first garnet-type oxide solid electrolyte 3 was obtained by treating in the same manner as in the above-mentioned "Obtaining garnet-type oxide solid electrolyte 1" except that the above-mentioned intermediate 3 was used. The diameter of the first garnet-type oxide solid electrolyte 3 was 8 mm to 9.5 mm, which was slightly smaller than before firing.

[0038] 4. Ionic Conductivity Measurement To measure the ionic conductivity, Li symmetric cell 1 was fabricated using first garnet-type oxide solid electrolyte 1. In Li symmetric cell 1, first garnet-type oxide solid electrolyte 1 was sandwiched between two lithium disks (8–9 mm in diameter) at a pressure of approximately 1.5 N·m. The ionic conductivity was measured using an AC impedance method. The AC impedance measurement conditions were an amplitude of 100 mV (increased to 500 mV when the resistance was high and measurement was difficult), and a scan frequency of 32 MHz–10 μHz. Li symmetric cell 2 was fabricated using the same process as Li symmetric cell 1, except that first garnet-type oxide solid electrolyte 2 was used instead of first garnet-type oxide solid electrolyte 1. Li symmetric cell 3 was fabricated using the same process as Li symmetric cell 1, except that first garnet-type oxide solid electrolyte 3 was used instead of first garnet-type oxide solid electrolyte 1. The ionic conductivities of the first garnet-type oxide solid electrolyte 2 and the first garnet-type oxide solid electrolyte 3 were measured by the same measurement method as that for the first garnet-type oxide solid electrolyte 1, except that the Li symmetric cell 2 and the Li symmetric cell 3 were used instead of the Li symmetric cell 1.

[0039] 5. Effect of heating time on ionic conductivity 1) Preparation of garnet-type oxide solid electrolyte 2 with different heating times The first garnet-type oxide solid electrolyte 2 (0.5h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C in a calcination furnace for 30 minutes under the conditions in the dry chamber, and then cooled to room temperature in the calcination furnace over 2 to 4 hours. The first garnet-type oxide solid electrolyte 2 (1h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C in a calcination furnace for 1 hour under the conditions in the dry chamber, and then cooled to room temperature in the calcination furnace over 2 to 4 hours. The first garnet-type oxide solid electrolyte 2 (2h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C in a calcination furnace for 2 hours under the conditions in the dry chamber, and then cooled to room temperature in the calcination furnace over 2 to 4 hours. The first garnet-type oxide solid electrolyte 2 (4h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C for 4 hours in a calcination furnace under the conditions in the dry chamber described above, followed by cooling to room temperature in the calcination furnace over 2 to 4 hours. The first garnet-type oxide solid electrolyte 2 (6h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C for 6 hours in a calcination furnace under the conditions in the dry chamber described above, followed by cooling to room temperature in the calcination furnace over 2 to 4 hours. The first garnet-type oxide solid electrolyte 2 (8h) was obtained by a heating and cooling process in which intermediate 2 was heated to 1000°C for 8 hours in a calcination furnace under the conditions in the dry chamber described above, followed by cooling to room temperature in the calcination furnace over 2 to 4 hours.

[0040] 2) Confirmation of the effect of heating time on ionic conductivity Figure 1 shows the measurement results of the ionic conductivity of the first garnet-type oxide solid electrolyte 2 heated for different times. As shown in Figure 1, the first garnet-type oxide solid electrolyte 2 (2h), the first garnet-type oxide solid electrolyte 2 (4h), and the first garnet-type oxide solid electrolyte 2 (6h) have an ionic conductivity of 4.0 × 10 -5On the other hand, the first garnet-type oxide solid electrolyte 2 (0.5 h), the first garnet-type oxide solid electrolyte 2 (1 h), and the first garnet-type oxide solid electrolyte 2 (8 h), which were obtained by heating for 30 minutes, 1 hour, and 8 hours, respectively, had an ionic conductivity of 4.0 × 10 -5 1, the first garnet-type oxide solid electrolyte 2 obtained by the treatment for a heating time of 2 to 7 hours has an ionic conductivity of 5.0 × 10 -5 It has high ionic conductivity of over S / cm.

[0041] 6. Effect of heating temperature on ionic conductivity 1) Obtaining the first garnet-type oxide solid electrolyte 1 at different heating temperatures The first garnet-type oxide solid electrolyte 1 (800°C) was obtained by a heating and cooling process in which intermediate 1 was heated to 800°C in a calcination furnace under the conditions in the dry chamber described above for two hours, and then cooled to room temperature in the calcination furnace over two to four hours. The first garnet-type oxide solid electrolyte 1 (900°C) was obtained by a heating and cooling process in which intermediate 1 was heated to 900°C in a calcination furnace under the conditions in the dry chamber described above for two hours, and then cooled to room temperature in the calcination furnace over two to four hours. The first garnet-type oxide solid electrolyte 1 (1000°C) was obtained by a heating and cooling process in which intermediate 1 was heated to 1000°C in a calcination furnace under the conditions in the dry chamber described above for two hours, and then cooled to room temperature in the calcination furnace over two to four hours. The first garnet-type oxide solid electrolyte 1 (1100°C) was obtained by a heating and cooling process in which the intermediate 1 was heated to 1100°C using a firing furnace under the above-mentioned conditions in the dry chamber for 2 hours, and then cooled to room temperature in the firing furnace over 2 to 4 hours.

[0042] 2) Preparation of the first garnet-type oxide solid electrolytes 2 and 3 at different heating temperatures By using Intermediate 2 instead of Intermediate 1, and by using the same method as in the above-mentioned "Obtaining Garnet-Type Oxide Solid Electrolytes 1 with Different Heating Temperatures," first garnet-type oxide solid electrolyte 2 (800°C), first garnet-type oxide solid electrolyte 2 (900°C), first garnet-type oxide solid electrolyte 2 (1000°C), and first garnet-type oxide solid electrolyte 2 (1100°C) with different heating temperatures were obtained. Similarly, by using Intermediate 3, first garnet-type oxide solid electrolyte 3 (800°C), first garnet-type oxide solid electrolyte 3 (900°C), first garnet-type oxide solid electrolyte 3 (1000°C), and first garnet-type oxide solid electrolyte 3 (1100°C) with different heating temperatures were obtained.

[0043] 3) Confirmation of the effect of heating temperature on ionic conductivity FIG. 2 shows the results of measuring the ionic conductivity of the first garnet-type oxide solid electrolytes 1 to 3 heated at different temperatures. As shown in FIG. 2, when the heating temperatures are 800, 900, and 1000°C, the first garnet-type oxide solid electrolyte 1 has higher ionic conductivity than the first garnet-type oxide solid electrolytes 2 and 3. In particular, when the heating temperature is 1000°C, the ionic conductivity of the first garnet-type oxide solid electrolyte 1 (approximately 1.4×10 -4 S / cm) of the first garnet-type oxide solid electrolyte 2 (approximately 5.0 × 10 -5 S / cm), and 3 (approximately 4.0 × 10 -5 This is significantly higher than the ionic conductivity of 0.25 S / cm.

[0044] First garnet-type oxide solid electrolyte 1 is a first garnet-type oxide solid electrolyte produced using LLZO powder with a median diameter (D50) of 0.1 μm. On the other hand, first garnet-type oxide solid electrolytes 2 and 3 are first garnet-type oxide solid electrolytes produced using LLZO powder with a median diameter (D50) of 1 μm and 10 μm, respectively. That is, according to FIG. 2, when the heating temperature is 950 to 1050°C, the first garnet-type oxide solid electrolyte produced using LLZO powder with a median diameter (D50) of 0.02 to 0.2 μm has significantly higher ionic conductivity than the first garnet-type oxide solid electrolyte produced using LLZO powder with a median diameter (D50) of 1 μm or more.

Claims

1. Li with a median diameter (D50) of 0.02 to 0.2 μm ７ La ３ Zr ２ O １２ The powder is compressed to obtain an intermediate product. the intermediate is heated at 950 to 1050°C for 2 to 7 hours, and then cooled to room temperature over 4 hours or more to obtain a first garnet-type oxide solid electrolyte; A method for producing a garnet-type oxide solid electrolyte.

2. 2. The method for producing a garnet-type oxide solid electrolyte according to claim 1, wherein the first garnet-type oxide solid electrolyte is brought into contact with at least one selected from an organic plastic ionic crystal and an ionic liquid to obtain a second garnet-type oxide solid electrolyte.

3. The Li ７ La ３ Zr ２ O １２ 3. The method for producing a garnet-type oxide solid electrolyte according to claim 1, wherein the intermediate is obtained by compacting the powder under a pressure of 72 MPa or more.

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