Process for producing a garnet-type oxide solid electrolyte

Abstract

A method for producing a garnet-type oxide solid electrolyte includes: obtaining an intermediate by compression molding Li7La3Zr2O 12 -powder having an average diameter (D50) of 0.02 to 0.2 µm; and obtaining a first garnet-type oxide solid electrolyte by heating the intermediate product at 1050 to 1150 °C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour.

Description

Technical area

[0001] The present disclosure relates to a method for producing a garnet type oxide solid electrolyte. State of the art

[0002] In recent years, all-solid-state batteries have been proposed as next-generation batteries for automobiles and electronic devices. The all-solid-state battery is a secondary battery in which a solid electrolyte is sandwiched between a cathode and an anode. Common 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 and therefore have lower interfacial resistance and higher ionic conductivity. However, sulfide-based solid electrolytes have lower chemical stability than oxide-based solid electrolytes. When the sulfide-based solid electrolytes come into contact with air, hydrogen sulfide gas is generated.Oxide-based solid electrolytes have higher chemical stability than sulfide-based solid electrolytes, but it is difficult to reduce the interfacial resistance because of the hardness of oxide-based solid electrolytes. Therefore, oxide-based solid electrolytes have low ionic conductivity.

[0003] Examples of oxide-based solid electrolytes include La 1-3x Li 3x Perovskite-type TiO3, Li 1+x AlxTi 2-x (PO4)3 of the NASICON type and Li7La3Zr2O 12Garnet-type oxide solid electrolyte (hereinafter sometimes referred to as "LLZO"). LLZO has high stability toward lithium metal and is considered promising as an oxide-based solid electrolyte for all-solid-state batteries. However, LLZO has the property that lithium carbonate is easily formed on the surface. The lithium carbonate formed on the surface of LLZO increases the interfacial resistance of the garnet-type oxide solid electrolyte. The increase in the interfacial resistance causes a decrease in ionic conductivity. Patent Document 1 discloses a method for reducing the interfacial resistance by polishing the garnet-type oxide solid electrolyte to remove lithium carbonate formed on the surface. Prior art documentsPatent documents

[0004] Patent Document 1: Japanese Unexamined Patent Application Laid-Open No. 2020-205284 (JP 2020-205284 A) Brief description of the invention

[0005] A method for producing a garnet-type oxide solid electrolyte according to one aspect of the present disclosure includes: Obtaining an intermediate by compression molding of Li7La3Zr2O 12 (LLZO) powder with an average diameter (D50) of 0.02 to 0.2 µm, and Obtaining a first garnet-type oxide solid electrolyte by heating the intermediate product at 950 to 1050 °C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour. Brief description of the drawings Fig. Figure 1 is a graph showing the relationship between a heating temperature in a heating / cooling step in which a cooling time is 4 hours (4 hours or more) and the ionic conductivity in garnet-type solid electrolytes made of LLZO powders with different average diameters (D50). Fig. Figure 2 is a graph showing the relationship between the heating temperature in the heating / cooling step where the cooling time is 1 hour (1 hour or less) and the ionic conductivity in garnet-type solid electrolytes made of LLZO powders with different average diameters (D50). Modes for carrying out the invention<Durch die offenbarte Erfindung zu lösende Probleme>

[0006] As described above, the oxide-based solid electrolyte has lower ionic conductivity than the sulfide-based solid electrolyte. Furthermore, the ionic conductivity of the garnet-type oxide solid electrolyte decreases due to the formation of lithium carbonate on the surface, etc. Therefore, there is a need for a method for producing a garnet-type oxide solid electrolyte with high ionic conductivity.

[0007] 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, the polishing method described in Patent Document 1 is difficult to apply to a garnet-type oxide solid electrolyte with a wavy surface. Therefore, when the above polishing process is applied, the shape of the garnet-type oxide solid electrolyte to be produced is limited. Thus, there is a need for a method for producing garnet-type oxide solid electrolytes that can easily remove impurities such as lithium carbonate from garnet-type oxide solid electrolytes with various shapes. <Effekte der offenbarten Erfindung>

[0008] The invention of the present disclosure provides a method for producing a garnet-type oxide solid electrolyte which can be easily applied to garnet-type oxide solid electrolytes having various shapes and which can produce a garnet-type oxide solid electrolyte having high ionic conductivity. <Umrisse einer Ausführungsform der offenbarten Erfindung>

[0009] Below are outlines of an embodiment of the invention of the present disclosure. (1) The method for producing a garnet type oxide solid electrolyte according to the present disclosure includes: Obtaining an intermediate by compression molding of Li7La3Zr2O 12 (LLZO) powder with an average diameter (D50) of 0.02 to 0.2 µm; and Obtaining a first garnet-type oxide solid electrolyte by heating the intermediate product at 1050 to 1150 °C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour.

[0010] With the manufacturing method according to (1), it is possible to produce garnet-type oxide solid electrolytes with high ionic conductivity and various shapes.

[0011] (2) The manufacturing method according to (1) includes obtaining a second garnet-type oxide solid electrolyte by bringing at least one of the materials selected from an organic plastic ionic crystal and an ionic liquid into contact with the first garnet-type oxide solid electrolyte.

[0012] With the manufacturing method according to (2), it is possible to produce the second garnet type oxide solid electrolyte with higher ionic conductivity.

[0013] (3) In the manufacturing method according to (1) or (2), the intermediate product is obtained by compression molding the LLZO powder under a condition of 72 MPa or more.

[0014] In the manufacturing process according to (3), the hardness of the intermediate product can be sufficiently ensured. Therefore, the shape of the intermediate product can be maintained. <details einer ausführungsform der offenbarten erfindung>

[0015] The embodiment of the present disclosure will be described below.

[0016] It is to be understood that the embodiment of the invention in the present disclosure is in all respects illustrative and not restrictive. The scope of the present invention is defined by the claims and is intended to include all modifications equivalent in meaning and scope to the claims.

[0017] The method for producing a garnet type oxide solid electrolyte according to the present disclosure includes: 1) a compression molding step to obtain an intermediate product by compression molding Li7La3Zr2O 12 (LLZO) powder with an average diameter (D50) of 0.02 to 0.2 µm; and 2) a heating / cooling step for obtaining a first garnet-type oxide solid electrolyte by heating the intermediate product at 1050 to 1150 °C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour. The procedure also includes

[0018] 3) a contact step of obtaining a second garnet-type oxide solid electrolyte by bringing at least one of the materials selected from an organic plastic ionic crystal and an ionic liquid into contact with the first garnet-type oxide solid electrolyte. 1) The compression molding step, 2) the heating / cooling step, and 3) the contact step are described below in order. 1) Compression molding step

[0019] First, the method for producing a garnet-type oxide solid electrolyte according to the present disclosure includes obtaining an intermediate product by compression molding LLZO powder having an average diameter (D50) of 0.02 to 0.2 µm. The average diameter (D50) is a value measured by a laser diffraction / scattering method in accordance with JIS Z 8825: 2013.

[0020] The above LLZO powder with an average diameter (D50) of 0.02 to 0.2 μm can be commercially available LLZO powder or LLZO powder prepared to have the above predetermined average diameter by pulverizing LLZO powder with an average diameter (D50) of more than 0.2 μm. The LLZO powder can be pulverized by any known method without particular limitation. Specific examples of the pulverization method include a pulverization method using a bead mill, a ball mill, or a jet mill.The LLZO powder having the above predetermined average diameter can be obtained, for example, by pulverizing commercially available LLZO powder having an average diameter (D50) of more than 0.2 µm in isopropanol using a bead mill to obtain an isopropanol suspension, and then removing isopropanol from the isopropanol suspension using an evaporator.

[0021] The above compression molding can be any known compression molding for use in the production of solid electrolytes and is not particularly limited. An example of a process including known compression molding is a process in which LLZO powder having the above predetermined average diameter is filled into a powder compression molding machine and then uniaxial compression molding is performed using a hydraulic press. In uniaxial compression molding, the pressure to obtain the LLZO powder intermediate is preferably 72 MPa or more. The intermediate obtained by compression molding under the condition of 72 MPa or more has sufficient hardness. The pressure to obtain the LLZO powder intermediate can be any pressure as long as it is high.The upper limit of pressure required to obtain the LLZO powder intermediate is limited to the upper limit of the pressure that can be applied by a pressurizing device for use in the hydraulic press, and is, for example, 650 MPa, but can be higher. Thus, the shape of the intermediate can be maintained throughout the subsequent heating / cooling step and the subsequent contact step, which will be described later. 2) Heating / cooling step

[0022] The method for producing a garnet-type oxide solid electrolyte according to the present disclosure includes obtaining the first garnet-type oxide solid electrolyte by heating the above intermediate product at 1050 to 1150°C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour. The heating in the heating / cooling step can be performed using a known furnace for use in the production of solid electrolytes. Treating the intermediate product 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 product.

[0023] The heating temperature in the above heating / cooling step is 1050 to 1150°C. The heating time in the heating / cooling step is 1 to 3 hours. The heating temperature of 1050°C or more and the heating time of 1 hour or more result in sufficient removal of impurities from the above LLZO powder intermediate. The heating temperature of 1150°C or less and the heating time of 3 hours or less reduce energy consumption due to progressive heating, resulting in a reduction in the manufacturing cost of the manufacturing method of the present disclosure.

[0024] The LLZO powder intermediate subjected to the above heat treatment is cooled to room temperature within 1 hour to become the first garnet-type oxide solid electrolyte. The room temperature is 5 to 35°C. Cooling is performed, for example, by removing the LLZO powder intermediate subjected to the heat treatment from the firing furnace and leaving it in a drying chamber or a glove box described later to cool it to room temperature within 1 hour. The first garnet-type oxide solid electrolyte obtained by the manufacturing method of the present disclosure, which includes the heating / cooling step with the above combination of the heating temperature, heating time, and cooling time, has high ionic conductivity. 3) Contact step

[0025] The method for producing the second garnet-type oxide solid electrolyte according to the present disclosure includes obtaining the second garnet-type oxide solid electrolyte by contacting at least one of an organic plastic ionic crystal and an ionic liquid (hereinafter sometimes referred to as "organic plastic ionic crystal, etc.") with the above first garnet-type oxide solid electrolyte. The above organic plastic ionic crystal, etc., can form an ion conduction path. By contacting the above organic plastic ionic crystal, etc., with the first garnet-type oxide solid electrolyte, the internal resistance and the interfacial resistance of the second garnet-type oxide solid electrolyte are reduced. By contacting the above organic plastic ionic crystal, etc.The first garnet-type oxide solid electrolyte is coated with the organic plastic ion crystal, etc., on the second garnet-type oxide solid electrolyte. This suppresses the formation of lithium carbonate on the surface of the first garnet-type oxide solid electrolyte. As a result, the second garnet-type oxide solid electrolyte is a garnet-type oxide solid electrolyte with high ionic conductivity. From the perspective of coating the surface of the first garnet-type oxide solid electrolyte, it is preferable to bring the organic plastic ion crystal into contact. Bringing the organic plastic ion crystal into contact with the first garnet-type oxide solid electrolyte results in obtaining a second garnet-type oxide solid electrolyte with higher ionic conductivity.

[0026] The method for achieving the above contact between the first garnet-type oxide solid electrolyte and the organic plastic ion crystal, etc., is not particularly limited as long as the first garnet-type oxide solid electrolyte can be impregnated with the organic plastic ion crystal, etc. Examples of the method for achieving the above contact include a method of immersing the first garnet-type oxide solid electrolyte in the organic plastic ion crystal, etc., and a method of dripping the organic plastic ion crystal, etc., onto the first garnet-type oxide solid electrolyte.

[0027] The above organic plastic ion crystal is not particularly limited as long as it is a known organic plastic ion crystal that can be applied to lithium secondary batteries. Examples of the organic plastic ion crystal include aliphatic quaternary ammonium salts composed of perfluoroanions, such as N,N-diethyl-N-methyl-N-propylammonium trifluoromethyltrifluoroborate (N 2,2,1,3 [BF3CF3]) analogues and N-ethyl-N-methylpyrrolidinium bisfluorosulfonylamide (Py 1,2 [FSA]) analogues. From the point of view of electrochemical stability, the organic plastic ionic crystal is preferably N 2,2,1,3 [BF3CF3].

[0028] The above ionic liquid is not particularly limited as long as it is a known ionic liquid that can be applied to lithium secondary batteries. Examples of the ionic liquid include N-methyl-N-propylpyrrolidinium bisfluorosulfonylamide (Py 1,3 [FSA]), N-methyl-N-propylpyrrolidiniumbis(trifluoromethylsulfonylamide) (Py 1,3 [TFSA]) and N-ethyl-N-methylimidazolium bisfluorosulfonylamide (]EMI[FSA]). From an electrochemical point of view, the ionic liquid is preferably Py 1,3 [FSA].

[0029] Each step in the method for producing a garnet-type oxide solid electrolyte according to the present disclosure can be performed in a drying chamber or a glove box. In particular, it is preferable that the heating / cooling step and the contact step be performed in the drying chamber. This suppresses the formation of lithium carbonate or lithium hydroxide 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 environment in the drying chamber or glove box be such that the dew point is -50°C or less. Examples

[0030] Next, the invention of the present disclosure will be described in more detail by way of examples, but the invention of the present disclosure is not limited to these examples only. 1. Raw materials used: LLZO powder LLZO powder A: average diameter (D50) of 0.1 µm LLZO powder B: average diameter (D50) of 0.1 µm LLZO powder: average diameter (D50) of 1 µm (manufactured by Toshima Manufacturing Co., Ltd.) LLZO powder: average diameter (D50) of 10 µm (manufactured by Toshima Manufacturing Co., Ltd.) Obtaining LLZO powder A with an average diameter (D50) of 0.1 µm

[0031] An LLZO-isopropanol suspension was prepared by pulverizing LLZO powder with a mean diameter (D50) of 8.9 µm (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) in isopropanol using a bead mill (Easynano (RMB type) (manufactured by Aimex Co., Ltd.)) with ZrO2 with a mean particle size of φ0.1 mm. LLZO powder A with a mean diameter (D50) of 0.1 µm was obtained by removing isopropanol from the LLZO-isopropanol suspension using an evaporator. Obtaining LLZO powder B with an average diameter (D50) of 0.1 µm

[0032] An LLZO-isopropanol suspension was prepared by pulverizing the above LLZO powder with a mean diameter (D50) of 1 µm (manufactured by Toshima Manufacturing Co., Ltd.) in isopropanol using a bead mill (Easynano (RMB type) (manufactured by Aimex Co., Ltd.)) with ZrO2 with a mean particle size of φ0.1 mm. LLZO powder B with a mean diameter (D50) of 0.1 µm was obtained by removing isopropanol from the LLZO-isopropanol suspension using an evaporator. 2. Compression molding step1) Obtaining intermediate product 1

[0033] An intermediate product 1 was obtained by filling 0.075 to 0.15 g of LLZO powder A with an average diameter (D50) of 0.1 µm into a powder compression molding machine with a bore diameter of 10 mm in a drying chamber with a dew point of -50°C or less. Uniaxial compression molding was then performed on the LLZO powder with an average diameter (D50) of 0.1 µm at 433 MPa using a hydraulic press. The diameter of intermediate product 1 is 10 mm. 2) Obtaining intermediate 2

[0034] An intermediate 2 was prepared using LLZO powder B with an average diameter (D50) of 0.1 µm. Intermediate 2 was obtained by a process carried out using the same method as that used to obtain Intermediate 1 above, except that LLZO powder B with an average diameter (D50) of 0.1 µm was used instead of LLZO powder A with an average diameter (D50) of 0.1 µm. The diameter of Intermediate 2 is 10 mm. 3) Obtaining intermediate 3

[0035] An intermediate 3 was prepared using the LLZO powder with an average diameter (D50) of 1 µm. Intermediate 3 was obtained by a process carried out using the same method as that used to obtain Intermediate 1 above, except that the LLZO powder with an average diameter (D50) of 1 µm was used instead of the LLZO powder A with an average diameter (D50) of 0.1 µm. The diameter of Intermediate 3 is 10 mm. 4) Obtaining intermediate 4

[0036] An intermediate 4 was prepared using the LLZO powder with an average diameter (D50) of 10 µm. Intermediate 4 was obtained by a process carried out using the same method as that used to obtain Intermediate 1 above, except that the LLZO powder with an average diameter (D50) of 10 µm was used instead of the LLZO powder A with an average diameter (D50) of 0.1 µm. The diameter of Intermediate 4 is 10 mm. 3. Heating / cooling step1) Obtaining a first oxide solid electrolyte of garnet type 1

[0037] A first garnet-type oxide solid electrolyte 1 was obtained by treating the above intermediate 1 using a firing furnace under the above condition in the drying chamber by methods described later in "Effect of heating temperature on ionic conductivity when cooling time is 4 hours (4 hours or more)" and "Effect of heating temperature on ionic conductivity when cooling time is 1 hour (1 hour or less)." The diameter of the first garnet-type oxide solid electrolyte 1 is 10 mm. 2) Obtaining a first garnet type 2 oxide solid electrolyte

[0038] A first garnet-type oxide solid electrolyte 2 was prepared using the above intermediate product 2. The first garnet-type oxide solid electrolyte 2 was obtained by a process performed by the method described in "Effect of Heating Temperature on Ionic Conductivity When Cooling Time is 1 Hour (1 Hour or Less)" for "Obtaining Garnet-type Oxide Solid Electrolyte 1", except that the above intermediate product 2 was used. The diameter of the first garnet-type oxide solid electrolyte 2 is 10 mm. 3) Obtaining a first garnet type 3 oxide solid electrolyte

[0039] A first garnet-type oxide solid electrolyte 3 was prepared using the above intermediate product 3. The first garnet-type oxide solid electrolyte 3 was obtained by a process performed by the same method as that for "Obtaining Garnet-type Oxide Solid Electrolyte 1," except that the above intermediate product 3 was used. The diameter of the first garnet-type oxide solid electrolyte 3 is 10 mm. 4) Obtaining a first oxide solid electrolyte of garnet type 4

[0040] A first garnet-type oxide solid electrolyte 4 was prepared using the above intermediate product 4. The first garnet-type oxide solid electrolyte 4 was obtained by a process carried out by the method described in "Effect of Heating Temperature on Ionic Conductivity When Cooling Time is 4 Hours (4 Hours or More)" for "Obtaining Garnet-type Oxide Solid Electrolyte 1", except that the above intermediate product 4 was used. The diameter of the first garnet-type oxide solid electrolyte 4 is 10 mm. 4. Measurement of ionic conductivity

[0041] To measure the ionic conductivity, a symmetrical Li cell 1 was fabricated using the first garnet-type 1 oxide solid electrolyte. In the symmetrical Li cell 1, the first garnet-type 1 oxide solid electrolyte is sandwiched between two lithium disks (8 to 9 mm in diameter) at a pressure of approximately 1.5 N m. The ionic conductivity was measured using an alternating current impedance method. The conditions for measuring the alternating current impedance were an amplitude of 10 to 100 mV and a sampling frequency of 32 MHz to 10 µHz. A symmetrical Li cell 2 was fabricated using the first garnet-type 2 oxide solid electrolyte. Symmetric Li cell 2 was fabricated by the same process as for symmetric Li cell 1, except that garnet type 2 first oxide solid electrolyte was used instead of garnet type 1 first oxide solid electrolyte.A symmetrical Li cell 3 was fabricated using the first garnet-type 3 oxide solid electrolyte. The symmetrical Li cell 3 was fabricated by the same process as for the symmetrical Li cell 1, except that the first garnet-type 3 oxide solid electrolyte was used instead of the first garnet-type 1 oxide solid electrolyte. A symmetrical Li cell 4 was fabricated using the first garnet-type 4 oxide solid electrolyte. The symmetrical Li cell 4 was fabricated by the same process as for the symmetrical Li cell 1, except that the first garnet-type 4 oxide solid electrolyte was used instead of the first garnet-type 1 oxide solid electrolyte.The ionic conductivities of the first garnet type 2 oxide solid electrolyte, the first garnet type 3 oxide solid electrolyte, and the first garnet type 4 oxide solid electrolyte were measured by the same measurement method as for the above first garnet type 1 oxide solid electrolyte, using the symmetrical Li cell 2, the symmetrical Li cell 3, and the symmetrical Li cell 4 instead of the symmetrical Li cell 1.

[0042] 5. Effect of heating temperature on ionic conductivity when cooling time is 4 hours (4 hours or more).

[0043] 1) Obtaining first oxide solid electrolytes of garnet type 1 (4 hours or more), which differ in heating temperatures with cooling time of 1 hour (4 hours or more).

[0044] A first garnet-type oxide solid electrolyte 1 (800°C, 4 hours or more) was obtained through a heating / cooling step in which the intermediate product 1 was heated at a heating temperature of 800°C for a heating time of 2 hours using a firing furnace according to the above condition in the drying chamber, and then cooled to room temperature in the firing furnace for 4 hours. A first garnet-type oxide solid electrolyte 1 (900°C, 4 hours or more) was obtained through a heating / cooling step in which the intermediate product 1 was heated at a heating temperature of 900°C for a heating time of 2 hours using a firing furnace according to the above condition in the drying chamber, and then cooled to room temperature in the firing furnace for 4 hours.A first garnet-type oxide solid electrolyte 1 (1000°C, 4 hours or more) was obtained through a heating / cooling step in which the intermediate product 1 was heated at a heating temperature of 1000°C for a heating time of 2 hours using a firing furnace according to the above condition in the drying chamber, and then cooled to room temperature in the firing furnace for 4 hours. A first garnet-type oxide solid electrolyte 1 (1100°C, 4 hours or more) was obtained through a heating / cooling step in which the intermediate product 1 was heated at a heating temperature of 1100°C for a heating time of 2 hours using a firing furnace according to the above condition in the drying chamber, and then cooled to room temperature in the firing furnace for 4 hours.

[0045] 2) Obtaining garnet type 3 (4 hours or more) and 4 (4 hours or more) oxide solid electrolytes, which differ in heating temperatures with cooling time of 4 hours (4 hours or more).

[0046] Using Intermediate 3, a garnet-type 3 first oxide solid electrolyte (800 °C, 4 hours or more), a garnet-type 3 first oxide solid electrolyte (900 °C, 4 hours or more), a garnet-type 3 first oxide solid electrolyte (1000 °C, 4 hours or more), and a garnet-type 3 first oxide solid electrolyte (1100 °C, 4 hours or more) differing in heating temperatures were obtained by the same method as that for "Obtaining Garnet-type 1 Oxide Solid Electrolytes Differing in Heating Temperatures with Cooling Time of 4 Hours (4 Hours or More)", except that Intermediate 3 was used instead of Intermediate 1.Similarly, a garnet type 4 first oxide solid electrolyte (800 °C, 4 hours or more), a garnet type 4 first oxide solid electrolyte (900 °C, 4 hours or more), a garnet type 4 first oxide solid electrolyte (1000 °C, 4 hours or more), and a garnet type 4 first oxide solid electrolyte (1100 °C, 4 hours or more) differing in heating temperatures were obtained using Intermediate 4.

[0047] 3) To check the effect of heating temperature on ionic conductivity when the cooling time is 4 hours (4 hours or more).

[0048] Fig. Figure 1 shows the measurement results of the ionic conductivities of the above first garnet type oxide solid electrolytes 1 (4 hours or more), 3 (4 hours or more), and 4 (4 hours or more), which differ in the heating temperatures with the cooling time of 4 hours (4 hours or more). Fig. Figure 1 shows that when the heating temperature is 800 to 1000 °C, the ionic conductivities of the first oxide solid electrolytes of garnet type 1 (4 hours or more), 3 (4 hours or more), and 4 (4 hours or more) tend to increase. Fig. However, Figure 1 shows that when the heating temperature is 1000 °C or more, the ionic conductivity of the first garnet-type 1 oxide solid electrolyte (4 hours or more) decreases, in contrast to the first garnet-type 3 oxide solid electrolytes (4 hours or more) and 4 oxide solid electrolytes (4 hours or more). It is experimentally shown that when the heating temperature is 1100 °C, the ionic conductivity of the first garnet-type 1 oxide solid electrolyte (4 hours or more) (about 6.0 × 10 -5 S / cm) is significantly lower than the ionic conductivity of the first garnet type 3 oxide solid electrolyte (4 hours or more) (about 1.2 × 10 -4 S / cm) and the ionic conductivity of the first oxide solid electrolyte of garnet type 4 (4 hours or more) (about 9.0 × 10 -5 S / cm).

[0049] 6. Effect of heating temperature on ionic conductivity when cooling time is 1 hour (1 hour or less).

[0050] 1) Obtaining first oxide solid electrolytes of garnet type 1 (1 hour or less) differing in heating temperatures with cooling time of 1 hour (1 hour or less).

[0051] A garnet type 1 first oxide solid electrolyte (800 °C, 1 hour or less), a garnet type 1 first oxide solid electrolyte (900 °C, 1 hour or less), a garnet type 1 first oxide solid electrolyte (1000 °C, 1 hour or less), and a garnet type 1 first oxide solid electrolyte (1100 °C, 1 hour or less) differing in heating temperatures were obtained by the same method as that for "Obtaining garnet type 1 first oxide solid electrolytes differing in heating temperatures with the cooling time of 4 hours (4 hours or more)", except that the cooling time is 1 hour (1 hour or less) instead of 4 hours (4 hours or more).

[0052] 2) Obtaining garnet type 2 (1 hour or less) and 3 (1 hour or less) oxide solid electrolytes, which differ in heating temperatures with cooling time of 1 hour (1 hour or less).

[0053] Using Intermediate 2, a garnet-type 2 first oxide solid electrolyte (800 °C, 1 hour or less), a garnet-type 2 first oxide solid electrolyte (900 °C, 1 hour or less), a garnet-type 2 first oxide solid electrolyte (1000 °C, 1 hour or less), and a garnet-type 2 first oxide solid electrolyte (1100 °C, 1 hour or less) differing in heating temperatures were obtained by the same method as that for "Obtaining Garnet-type 1 Oxide Solid Electrolytes Differing in Heating Temperatures with Cooling Time of 1 Hour (1 hour or less)", except that Intermediate 2 was used instead of Intermediate 1.Similarly, a garnet type 3 first oxide solid electrolyte (800 °C, 1 hour or less), a garnet type 3 first oxide solid electrolyte (900 °C, 1 hour or less), a garnet type 3 first oxide solid electrolyte (1000 °C, 1 hour or less), and a garnet type 3 first oxide solid electrolyte (1100 °C, 1 hour or less) differing in heating temperatures were obtained using Intermediate 3.

[0054] 3) To check the effect of heating temperature on ionic conductivity when the cooling time is 1 hour (1 hour or less).

[0055] Fig. Figure 2 shows the results of measuring the ionic conductivities of the above first garnet type 1 to 3 oxide solid electrolytes, which differ in the heating temperatures with the cooling time of 1 hour (1 hour or less). Fig. Figure 2 shows that when the heating temperature is 800 and 900 °C, the first oxide solid electrolytes of garnet types 1 to 3 show approximately the same increase in ionic conductivity. Fig. Figure 2 shows that the ionic conductivities of the first garnet-type 1 and 2 oxide solid electrolytes increase significantly when the heating temperature is 1000 °C or higher. It is experimentally shown that when the heating temperature is 1100 °C, the ionic conductivity of the first garnet-type 1 oxide solid electrolyte (about 4.5 × 10 -4 S / cm) and the ionic conductivity of the first garnet type 2 oxide solid electrolyte (about 3.5 × 10 -4 S / cm) are significantly higher than the ionic conductivity of the first garnet type 3 oxide solid electrolyte (about 1.0 × 10 -4 S / cm).

[0056] The first garnet-type oxide solid electrolytes 1 and 2 are the first garnet-type oxide solid electrolytes produced using LLZO powders with average diameters (D50) of 0.1 µm and 0.1 µm, respectively. The first garnet-type oxide solid electrolytes 3 and 4 are the first garnet-type oxide solid electrolytes produced using LLZO powders with average diameters (D50) of 1 µm and 10 µm, respectively. Fig. 1 and Fig. 2, the effects of heating temperature on the ionic conductivities of the garnet type 1 and 2 first oxide solid electrolytes differ between the case where the cooling time is 4 hours (4 hours or more) and the case where the cooling time is 1 hour (1 hour or less). More specifically, at a heating temperature of 1000 °C or more, the ionic conductivities of the garnet type 1 and 2 first oxide solid electrolytes decrease when the cooling time is 4 hours (4 hours or more) and increase when the cooling time is 1 hour (1 hour or less).Specifically, at the heating temperature of 1100 °C, the ionic conductivities of the first garnet type 1 and 2 oxide solid electrolytes are significantly lower than the ionic conductivity of the first garnet type 3 oxide solid electrolyte when the cooling time is 4 hours (4 hours or more), and are significantly higher than the ionic conductivity of the first garnet type 3 oxide solid electrolyte when the cooling time is 1 hour (1 hour or less).From this, it is experimentally suggested 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 the LLZO powder with the average diameter (D50) of 0.02 to 0.2 μm has a significantly higher ionic conductivity than the first garnet-type oxide solid electrolyte prepared using the LLZO powder with the average diameter (D50) of 1 μm or more. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-205284

[0004] JP 2020-205284 A

[0004] Cited non-patent literature

[0000] JIS Z 8825: 2013

[0019] < / details>

Claims

[1] A process for producing a garnet-type oxide solid electrolyte, the process comprising: obtaining an intermediate by compression molding of Li7La3Zr2O 12 -powders with an average diameter (D50) of 0.02 to 0.2 µm; and obtaining a first garnet-type oxide solid electrolyte by heating the intermediate product at 1050 to 1150 °C for 1 to 3 hours and then cooling the intermediate product to room temperature within 1 hour. [2] A method for producing the garnet type oxide solid electrolyte according to claim 1, further comprising obtaining a second garnet type oxide solid electrolyte by contacting at least one of an organic plastic ionic crystal and an ionic liquid with the first garnet type oxide solid electrolyte. [3] A method for producing the garnet type oxide solid electrolyte according to claim 1 or 2, wherein the intermediate product is obtained by compression molding the Li7La3Zr2O 12 powder is obtained under a condition of 72 MPa or more.

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