Method for producing garnet-type oxide solid electrolyte

Abstract

Disclosed is a method for producing a garnet-type oxide solid electrolyte, wherein: an intermediate is obtained by press molding an Li7La3Zr2O12 powder having a median diameter (D50) of 0.02 µm to 0.2 µm; and the intermediate is heated at 1050-1150°C for one to three hours and is subsequently cooled to room temperature within one hour, thereby obtaining 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 1050~1150 After heating at 0° C. for 1 to 3 hours, the mixture is cooled to room temperature within 1 hour 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 temperature and the ionic conductivity in a heating / cooling process in which the cooling time is 4 hours (4 hours or more) for garnet-type oxide solid electrolytes made of LLZO powders having different median diameters (D50). [Figure 2] 1 is a graph showing the relationship between the heating temperature and the ionic conductivity in a heating / cooling process with a cooling time of 1 hour (within 1 hour) for 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 1050 to 1150° C. for 1 to 3 hours, and then cooled to room temperature within 1 hour 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 1050 to 1150°C for 1 to 3 hours and then cooling it to room temperature within 1 hour 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 in which LLZO powder having the predetermined median diameter is introduced into a powder molding machine and then uniaxially pressed 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 pressed under 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, 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 1050 to 1150°C for 1 to 3 hours, and then cooled to room temperature within 1 hour 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 1050 to 1150°C for 1 to 3 hours is intended to remove impurities such as lithium carbonate and lithium hydroxide present in the intermediate.

[0022] The heating temperature in the heating and cooling step is 1050 to 1150°C. The heating time in the heating and cooling step is 1 to 3 hours. Here, the heating temperature of 1050°C or higher and the heating time of 1 hour or longer lead to sufficient removal of impurities from the LLZO powder intermediate. The heating temperature of 1150°C or lower and the heating time of 3 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 above-mentioned heat treatment is cooled to room temperature within one hour to form a first garnet-type oxide solid electrolyte. Here, room temperature is 5 to 35°C. The cooling is performed, for example, by removing the LLZO powder intermediate that has undergone the heat treatment from a firing furnace and leaving it in a dry chamber or glove box described below to cool to room temperature within one hour. 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 organic plastic ionic crystal into contact with the first garnet-type oxide solid electrolyte, 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. The environment in the dry chamber or glove box preferably has a dew point of −50° C. or lower. [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 Product A LLZO powder median diameter (D50) 0.1 μm Product B LLZO powder, median diameter (D50) 1 μm (manufactured by Toshima Manufacturing Co., Ltd.) LLZO powder, median diameter (D50) 10 μm (manufactured by Toshima Manufacturing Co., Ltd.)

[0031] (LLZO powder median diameter (D50) 0.1 μm, quality A obtained) The LLZO isopropanol suspension was prepared by grinding LLZO powder with a median diameter (D50) of 8.9 μm (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) in isopropanol using a bead mill (Easy Nano (RMB type) (manufactured by Aimex Co., Ltd.)) with ZrO2 media diameter of 0.1 mm. LLZO powder with a median diameter (D50) of 0.1 μm (Product A) was obtained by removing the isopropanol from the LLZO isopropanol suspension using an evaporator.

[0032] (LLZO powder median diameter (D50) 0.1 μm, product B obtained) The LLZO isopropanol suspension was prepared by grinding the above-mentioned 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 (Product B) was obtained by removing the isopropanol from the LLZO isopropanol suspension using an evaporator.

[0033] 2. Pressure molding process 1) Obtaining intermediate 1 Intermediate 1 was obtained by placing 0.075 to 0.15 g of LLZO powder A 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 A with a median diameter (D50) of 0.1 μm at 433 MPa using a hydraulic press. The diameter of Intermediate 1 was 10 mm.

[0034] 2) Obtaining intermediate 2 Intermediate 2 was produced using LLZO powder with a median diameter (D50) of 0.1 μm, product B. 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 0.1 μm, product B, was used instead of LLZO powder with a median diameter (D50) of 0.1 μm, product A. The diameter of Intermediate 2 is 10 mm.

[0035] 3) Obtaining intermediate 3 Intermediate 3 was produced using LLZO powder with a median diameter (D50) of 1 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 1 μm was used instead of LLZO powder with a median diameter (D50) of 0.1 μm product A. The diameter of Intermediate 3 is 10 mm.

[0036] 4) Obtaining intermediate 4 Intermediate 4 was produced using LLZO powder with a median diameter (D50) of 10 μm. Intermediate 4 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 product A. The diameter of Intermediate 4 is 10 mm.

[0037] 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 treating the intermediate 1 described above in a firing furnace under the conditions in the dry chamber described above by the methods described later in "Effect of heating temperature on ionic conductivity when the cooling time is 4 hours (4 hours or more)" and "Effect of heating temperature on ionic conductivity when the cooling time is 1 hour (1 hour or less)." The diameter of the first garnet-type oxide solid electrolyte 1 was 10 mm.

[0038] 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 it using the method described in "Effect of heating temperature on ionic conductivity when cooling time is 1 hour (within 1 hour)" in the above-mentioned "Obtaining garnet-type oxide solid electrolyte 1", except that the above-mentioned intermediate 2 was used. The diameter of the first garnet-type oxide solid electrolyte 2 was 10 mm.

[0039] 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 10 mm.

[0040] 4) Preparation of the first garnet-type oxide solid electrolyte 4 The first garnet-type oxide solid electrolyte 4 was produced using the above-mentioned intermediate 4. The first garnet-type oxide solid electrolyte 4 was obtained by treating it using the method described in "Effect of heating temperature on ionic conductivity when cooling time is 4 hours (4 hours or more)" in the above-mentioned "Obtaining garnet-type oxide solid electrolyte 1", except that the above-mentioned intermediate 4 was used. The diameter of the first garnet-type oxide solid electrolyte 4 was 10 mm.

[0041] 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 10–100 mV and a scan frequency of 32 MHz–10 μHz. Li symmetric cell 2 was fabricated using first garnet-type oxide solid electrolyte 2. 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. Li symmetric cell 4 was fabricated using first garnet-type oxide solid electrolyte 4. Li symmetric cell 4 was fabricated using the same process as Li symmetric cell 1, except that first garnet-type oxide solid electrolyte 4 was used instead of first garnet-type oxide solid electrolyte 1. The ionic conductivities of first garnet-type oxide solid electrolyte 2, first garnet-type oxide solid electrolyte 3, and first garnet-type oxide solid electrolyte 4 were measured by the same measurement method as for first garnet-type oxide solid electrolyte 1, except that Li symmetric cell 2, Li symmetric cell 3, and Li symmetric cell 4 were used instead of Li symmetric cell 1.

[0042] 5. Effect of heating temperature on ionic conductivity when the cooling time is 4 hours (or more than 4 hours) 1) Obtaining the first garnet-type oxide solid electrolyte 1 (4 hours or more) at different heating temperatures with a cooling time of 1 hour (4 hours or more). The first garnet-type oxide solid electrolyte 1 (800°C, 4 hours or more) was obtained by a heating / 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 2 hours, and then cooled to room temperature in the calcination furnace over 4 hours. The first garnet-type oxide solid electrolyte 1 (900°C, 4 hours or more) was obtained by a heating / 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 2 hours, and then cooled to room temperature in the calcination furnace over 4 hours. The first garnet-type oxide solid electrolyte 1 (1000°C, 4 hours or more) was obtained by a heating / 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 2 hours, and then cooled to room temperature in the calcination furnace over 4 hours. The first garnet-type oxide solid electrolyte 1 (1100°C, 4 hours or more) 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 4 hours.

[0043] 2) Obtaining garnet-type oxide solid electrolytes 3 (4 hours or more) and 4 (4 hours or more) with different heating temperatures when the cooling time was 4 hours (4 hours or more). By using Intermediate 3 instead of Intermediate 1, and by using the same method as in the above-mentioned "Obtaining Garnet-Type Oxide Solid Electrolytes 1 at Different Heating Temperatures with a Cooling Time of 4 Hours (4 Hours or More)," except that Intermediate 3 was used, First Garnet-Type Oxide Solid Electrolyte 3 (800°C, 4 Hours or More), First Garnet-Type Oxide Solid Electrolyte 3 (900°C, 4 Hours or More), First Garnet-Type Oxide Solid Electrolyte 3 (1000°C, 4 Hours or More), and First Garnet-Type Oxide Solid Electrolyte 3 (1100°C, 4 Hours or More) at different heating temperatures were obtained. Similarly, by using Intermediate 4, First Garnet-Type Oxide Solid Electrolyte 4 (800°C, 4 Hours or More), First Garnet-Type Oxide Solid Electrolyte 4 (900°C, 4 Hours or More), First Garnet-Type Oxide Solid Electrolyte 4 (1000°C, 4 Hours or More), and First Garnet-Type Oxide Solid Electrolyte 4 (1100°C, 4 Hours or More) were obtained at different heating temperatures.

[0044] 3) Confirmation of the effect of heating temperature on ionic conductivity when the cooling time is 4 hours (or more than 4 hours) FIG. 1 shows the results of measuring the ionic conductivity of the first garnet-type oxide solid electrolytes 1 (4 hours or more), 3 (4 hours or more), and 4 (4 hours or more) heated at different temperatures, when the cooling time was 4 hours (4 hours or more). FIG. 1 shows that the ionic conductivity of the first garnet-type oxide solid electrolytes 1 (4 hours or more), 3 (4 hours or more), and 4 (4 hours or more) tends to increase when the heating temperature is between 800 and 1000°C. However, it can be seen that the ionic conductivity of the first garnet-type oxide solid electrolyte 1 (4 hours or more) decreases when the heating temperature is 1000°C or more, unlike the first garnet-type oxide solid electrolytes 3 (4 hours or more) and 4 (4 hours or more). Furthermore, when the heating temperature was 1100°C, the ionic conductivity of the first garnet-type oxide solid electrolyte 1 (4 hours or more) (approximately 6.0 × 10 -5 S / cm) is the ionic conductivity (approximately 1.2 × 10 -4 S / cm), and the ionic conductivity of the first garnet-type oxide solid electrolyte 4 (over 4 hours) (approximately 9.0 × 10 -5It has been experimentally shown that the solubility of the solubility is significantly lower than the solubility of ...

[0045] 6. Effect of heating temperature on ionic conductivity when cooling time is 1 hour (within 1 hour) 1) Obtaining garnet-type oxide solid electrolyte 1 (within 1 hour) at first different heating temperatures with a cooling time of 1 hour (within 1 hour) By using the same method as in the above-mentioned "Obtaining first garnet-type oxide solid electrolyte 1 at different heating temperatures with a cooling time of 4 hours (4 hours or more)", except that the cooling time was changed from 4 hours (4 hours or more) to 1 hour (within 1 hour), first garnet-type oxide solid electrolyte 1 (800°C, within 1 hour), first garnet-type oxide solid electrolyte 1 (900°C, within 1 hour), first garnet-type oxide solid electrolyte 1 (1000°C, within 1 hour), and first garnet-type oxide solid electrolyte 1 (1100°C, within 1 hour) were obtained at different heating temperatures.

[0046] 2) Obtaining garnet-type oxide solid electrolytes 2 (within 1 hour) and 3 (within 1 hour) at different heating temperatures with a cooling time of 1 hour (within 1 hour). 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 at Different Heating Temperatures with a Cooling Time of 1 Hour (within 1 Hour)," except that Intermediate 2 was used, First Garnet-Type Oxide Solid Electrolyte 2 (800°C, within 1 Hour), First Garnet-Type Oxide Solid Electrolyte 2 (900°C, within 1 Hour), First Garnet-Type Oxide Solid Electrolyte 2 (1000°C, within 1 Hour), and First Garnet-Type Oxide Solid Electrolyte 2 (1100°C, within 1 Hour) were obtained at different heating temperatures. Similarly, by using Intermediate 3, First Garnet-Type Oxide Solid Electrolyte 3 (800°C, within 1 Hour), First Garnet-Type Oxide Solid Electrolyte 3 (900°C, within 1 Hour), First Garnet-Type Oxide Solid Electrolyte 3 (1000°C, within 1 Hour), and First Garnet-Type Oxide Solid Electrolyte 3 (1100°C, within 1 Hour) were obtained at different heating temperatures.

[0047] 3) Confirmation of the effect of heating temperature on ionic conductivity when the cooling time is 1 hour (within 1 hour) 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 after a cooling time of 1 hour (within 1 hour). It can be seen from FIG. 2 that when the heating temperatures are 800 and 900°C, the first garnet-type oxide solid electrolytes 1 to 3 show almost the same increase in ionic conductivity. On the other hand, when the heating temperature is 1000°C or higher, the ionic conductivity of the first garnet-type oxide solid electrolytes 1 and 2 increases significantly. Furthermore, when the heating temperature is 1100°C, the ionic conductivity of the first garnet-type oxide solid electrolyte 1 (about 4.5×10 -4 S / cm), and the ionic conductivity of the first garnet-type oxide solid electrolyte 2 (approximately 3.5 × 10 -4 S / cm) is the ionic conductivity of the first garnet-type oxide solid electrolyte 3 (approximately 1.0 × 10 -4 It has been experimentally shown that the ion exchange rate is significantly higher than the ion exchange rate (S / cm).

[0048] First garnet-type oxide solid electrolytes 1 and 2 were prepared using LLZO powders with median diameters (D50) of 0.1 μm and 0.1 μm, respectively. Meanwhile, first garnet-type oxide solid electrolytes 3 and 4 were prepared using LLZO powders with median diameters (D50) of 1 μm and 10 μm, respectively. As shown in FIGS. 1 and 2, the effect of heating temperature on the ionic conductivity of first garnet-type oxide solid electrolytes 1 and 2 differs between the cooling times of 4 hours (4 hours or more) and 1 hour (1 hour or less). More specifically, when the heating temperature is 1000°C or higher, the ionic conductivity of first garnet-type oxide solid electrolytes 1 and 2 decreases when the cooling time is 4 hours (4 hours or more) and increases when the cooling time is 1 hour (1 hour or less). In particular, at a heating temperature of 1100°C, the ionic conductivities of the first garnet-type oxide solid electrolytes 1 and 2 are significantly lower when the cooling time is 4 hours (4 hours or more) than the ionic conductivities of the first garnet-type oxide solid electrolyte 3, and are significantly higher when the cooling time is 1 hour (1 hour or less). This experimentally suggests that when the heating temperature is 1050 to 1150°C and the cooling time to room temperature is 1 hour or less, the first garnet-type oxide solid electrolyte prepared using LLZO powder with a median diameter (D50) of 0.02 to 0.2 μm has significantly higher ionic conductivities than the first garnet-type oxide solid electrolyte prepared 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 1050 to 1150°C for 1 to 3 hours, and then cooled to room temperature within 1 hour 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.

Images