Method for producing garnet-type oxide solid electrolyte

Abstract

A method for producing a garnet-type oxide solid electrolyte, in which a Li7La3Zr2O12 powder having a median diameter (D50) of 0.02-0.2 [mu] m is press-molded to obtain an intermediate, the intermediate is heated at 950-1050 DEG C for 2-7 hours, and then cooled to room temperature for 4 hours or more to obtain a first garnet-type oxide solid electrolyte.

Description

Technical Field

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

[0002] In recent years, all-solid-state batteries have been proposed as next-generation batteries for automobiles and electronic devices. An all-solid-state battery is a secondary battery in which a solid electrolyte is sandwiched between a positive electrode and a negative electrode. As the solid electrolyte used in an all-solid-state battery, sulfide-based solid electrolytes and oxide-based solid electrolytes are known. Generally, sulfide-based solid electrolytes are softer than oxide-based solid electrolytes, so they have a lower interfacial resistance and a higher ionic conductivity. However, sulfide-based solid electrolytes have lower chemical stability than oxide-based solid electrolytes, and hydrogen sulfide gas is generated in the event of contact with the atmosphere. On the other hand, oxide-based solid electrolytes have higher chemical stability than sulfide-based solid electrolytes, but are hard, so it is difficult to reduce the interfacial resistance and the ionic conductivity is low.

[0003] Oxide-based solid electrolytes include 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"), etc. LLZO has high stability with respect to lithium metal and is expected to be used as an oxide-based solid electrolyte for all-solid-state batteries. However, LLZO has the property of easily forming lithium carbonate on its surface. The 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. It should be noted that Patent Document 1 discloses the following method: by grinding a garnet-type oxide solid electrolyte, the lithium carbonate formed on the surface is removed, and the interfacial resistance is reduced.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-205284 Summary of the Invention

[0007] In the method for manufacturing a garnet-type oxide solid electrolyte according to one aspect of the present disclosure,

[0008] Li7La3Zr2O with a median particle size (D50) of 0.02 to 0.2 μm 12 (LLZO) powder is pressure-molded to obtain an intermediate product,

[0009] After heating the above intermediate at 950 - 1050 °C for 2 - 7 hours, it is cooled for more than 4 hours until room temperature to obtain a first garnet-type oxide solid electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a graph showing the relationship between the heating time in the heating and cooling process and the ionic conductivity of the garnet-type oxide solid electrolyte.

[0011] Figure 2 is a graph showing the relationship between the heating temperature and the ionic conductivity in the heating and cooling process of the garnet-type oxide solid electrolyte made of LLZO powder with different median particle sizes (D50). DETAILED DESCRIPTION OF THE INVENTION

[0012] <Problems to be Solved by the Invention of the Present Disclosure>

[0013] As described above, compared with sulfide-based solid electrolytes, oxide-based solid electrolytes have low ionic conductivity. In addition, the ionic conductivity of garnet-type oxide solid electrolytes is reduced due to lithium carbonate formed on the surface. Therefore, a method for manufacturing garnet-type oxide solid electrolytes with high ionic conductivity is needed.

[0014] The method disclosed in Patent Document 1 is a method for removing lithium carbonate formed on the surface of a garnet-type oxide solid electrolyte by grinding treatment and increasing the ionic conductivity of the above garnet-type oxide solid electrolyte. However, it is difficult to apply the grinding method described in Patent Document 1 to a garnet-type oxide solid electrolyte with undulating surfaces. Therefore, when applying the above grinding treatment, the shape of the garnet-type oxide solid electrolyte to be manufactured is restricted. Therefore, a method for manufacturing a garnet-type oxide solid electrolyte that can easily remove impurities such as lithium carbonate for various shapes of garnet-type oxide solid electrolytes is needed.

[0015] <Effects of the Invention of the Present Disclosure>

[0016] According to the invention of the present disclosure, there is provided a method for manufacturing a garnet-type oxide solid electrolyte that can easily adapt to various shapes of garnet-type oxide solid electrolytes and can manufacture garnet-type oxide solid electrolytes with high ionic conductivity.

[0017] <Outline of Embodiments of the Invention of the Present Disclosure>

[0018] Hereinafter, the outline of the embodiments of the invention of the present disclosure will be listed and described.

[0019] ​​(1) In the method for manufacturing a garnet-type oxide solid electrolyte of the present disclosure, Li7La3Zr2O powder with a median particle size (D50) of 0.02 to 0.2 μm is 12 pressure-formed to obtain an intermediate product,

[0020] After heating the above intermediate product at 950 to 1050 °C for 2 to 7 hours, it is cooled for 4 hours or more until room temperature to obtain a first garnet-type oxide solid electrolyte.

[0021] The manufacturing method described in the above (1) can manufacture garnet-type oxide solid electrolytes of various shapes with high ionic conductivity.

[0022] (2) In the manufacturing method described in the above (1), at least one selected from organic plastic ionic crystals and ionic liquids is brought into contact with the above first garnet-type oxide solid electrolyte to obtain a second garnet-type oxide solid electrolyte.

[0023] The manufacturing method described in the above (2) can manufacture a second garnet-type oxide solid electrolyte with higher ionic conductivity.

[0024] (3) In the manufacturing method described in the above (1) or (2), the above LLZO powder is pressure-formed under the condition of 72 MPa or more to obtain the above intermediate product.

[0025] The manufacturing method described in the above (3) can fully ensure the hardness of the intermediate product, and thus can maintain the shape of the intermediate product.

[0026] <Details of the Embodiments of the Invention of the Present Disclosure>

[0027] Hereinafter, embodiments of the present disclosure will be described.

[0028] In addition, in the present disclosure, it should be considered that the embodiments of the invention are illustrative in all aspects and not restrictive. The scope of the present invention is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0029] The method for manufacturing a garnet-type oxide solid electrolyte of the present disclosure includes:

[0030] 1) A pressure-forming step of pressure-forming Li7La3Zr2O powder with a median particle size (D50) of 0.02 to 0.2 μm 12 (LLZO) to obtain an intermediate product;

[0031] 2) Heating and cooling process: After heating the above intermediate at 950 - 1050 °C for 2 - 7 hours, cool it for more than 4 hours until room temperature to obtain the first garnet-type oxide solid electrolyte.

[0032] Furthermore, it has

[0033] 3) Contact process: Contact at least one selected from organic plastic ionic crystals and ionic liquids with the above first garnet-type oxide solid electrolyte to obtain the second garnet-type oxide solid electrolyte.

[0034] Hereinafter, the above 1) pressing and forming process, 2) heating and cooling process, and 3) contact process will be described in sequence.

[0035] 1) Pressing and forming process

[0036] First, in the method for manufacturing a garnet-type oxide solid electrolyte of the present disclosure, LLZO powder with a median particle size (D50) of 0.02 - 0.2 μm is pressed and formed to obtain an intermediate. The median particle size (D50) is a value measured by the laser diffraction / scattering method in accordance with JIS Z 8825:2013.

[0037] The above LLZO powder with a median particle size (D50) of 0.02 - 0.2 μm can be commercially available LLZO powder, or can be LLZO powder prepared by pulverizing LLZO powder with a median particle size (D50) exceeding 0.2 μm to the above predetermined median particle size. Here, the pulverizing method of LLZO powder can use a known method and is not particularly limited. Examples of specific pulverizing methods include using a bead mill, a ball mill, a jet mill, etc. The above LLZO powder with a predetermined median particle size can be obtained, for example, by pulverizing commercially available LLZO powder with a median particle size (D50) exceeding 0.2 μm in isopropyl alcohol using a bead mill to obtain an isopropyl alcohol suspension, and removing isopropyl alcohol from the isopropyl alcohol suspension with an evaporator.

[0038] The above-mentioned pressure forming can be carried out by known pressure forming used in the manufacture of solid electrolytes, without particular limitation. An example of a known process including a pressure forming step is a step of uniaxially pressure forming using a hydraulic press after charging LLZO powder having the above-mentioned predetermined median particle diameter into a powder former. In the above-mentioned uniaxial pressure forming, the pressure when obtaining the intermediate of the above-mentioned LLZO powder is preferably 72 MPa or more. The intermediate pressure formed under the condition of 72 MPa or more has sufficient hardness. The pressure when obtaining the intermediate of the above-mentioned LLZO powder can be a high pressure. The upper limit of the pressure when obtaining the intermediate of the above-mentioned LLZO powder is limited by the upper limit that can be pressurized by the pressurizing device of the above-mentioned hydraulic press, for example, 650 MPa or less, but it can also be more than that. Thus, the shape of the intermediate is maintained through the subsequent heating and cooling steps and contact steps described later.

[0039] 2) Heating and cooling step

[0040] In the method for manufacturing a garnet-type oxide solid electrolyte of the present disclosure, the above-mentioned intermediate is heated at 950 to 1050 °C for 2 to 7 hours and then cooled for 4 hours or more until room temperature to obtain a first garnet-type oxide solid electrolyte. The heating in the heating and cooling step can be carried out using a known firing furnace used in the manufacture of solid electrolytes. It should be noted that the treatment of the above-mentioned intermediate at 950 to 1050 °C for 2 to 7 hours is for the purpose of removing impurities such as lithium carbonate and lithium hydroxide present in the above-mentioned intermediate.

[0041] The heating temperature in the above-mentioned heating and cooling step is 950 to 1050 °C. In addition, the heating time in the above-mentioned heating and cooling step is 2 to 7 hours, preferably 3 to 6 hours. Here, the heating temperature being 950 °C or more and the heating time being 2 hours or more are related to sufficiently removing impurities from the intermediate of the above-mentioned LLZO powder. When the heating temperature is 1050 °C or less and the heating time is 7 hours or less, the energy consumption caused by continuous heating is suppressed, so it is related to reducing the manufacturing cost of the manufacturing method of the present invention.

[0042] The intermediate of the LLZO powder after the above heat treatment is cooled for 4 hours or more until room temperature, thereby becoming a first garnet-type oxide solid electrolyte. Here, the room temperature is 5 to 35 °C. The above cooling is performed, for example, by turning off the power supply of the firing furnace and allowing the temperature inside the firing furnace to decrease to room temperature by natural cooling for 4 hours or more. It should be noted that the cooling time until room temperature is preferably 4 to 8 hours. A cooling time of 8 hours or less can shorten the manufacturing cycle time, and thus the manufacturing efficiency of the manufacturing method of the present disclosure is improved. In addition, the first garnet-type oxide solid electrolyte obtained by the manufacturing method of the present disclosure including a heating and cooling step having a combination of the above heating temperature, heating time, and the above cooling time has high ionic conductivity.

[0043] 3) Contact step

[0044] The manufacturing method of the second garnet-type oxide solid electrolyte of the present disclosure is a method of obtaining a second garnet-type oxide solid electrolyte by bringing at least one selected from organic plastic ionic crystals and ionic liquids (hereinafter sometimes referred to as "organic plastic ionic crystals, etc.") into contact with the above first garnet-type oxide solid electrolyte. The above organic plastic ionic crystals, etc. can form an ionic conduction path. Therefore, by bringing the above organic plastic ionic crystals, etc. into contact with the first garnet-type oxide solid electrolyte, the internal resistance and interface resistance of the second garnet-type oxide solid electrolyte become reduced states. In addition, by bringing the above organic plastic ionic crystals, etc. into contact with the first garnet-type oxide solid electrolyte, the second garnet-type oxide solid electrolyte becomes covered with the above organic plastic ionic crystals, etc. Thereby, the formation of lithium carbonate on the surface of the first garnet-type oxide solid electrolyte can be suppressed. As a result, the second garnet-type oxide solid electrolyte is a garnet-type oxide solid electrolyte having high ionic conductivity. It should be noted that from the viewpoint of covering the surface of the above first garnet-type oxide solid electrolyte, it is preferable to bring the above ionic liquid and organic plastic ionic crystal into contact. Bringing the above organic plastic ionic crystal into contact with the first garnet-type oxide solid electrolyte results in obtaining a garnet-type oxide solid electrolyte having the second highest ionic conductivity.

[0045] The method of obtaining the contact between the above first garnet-type oxide solid electrolyte and the above organic plastic ionic crystals, etc. may be a method capable of impregnating the above first garnet-type oxide solid electrolyte with the above organic plastic ionic crystals, etc., and there is no particular limitation. The method of obtaining the above contact is, for example, a method of immersing the first garnet-type oxide solid electrolyte in the above organic plastic ionic crystals, etc., or a method of dropping the above organic plastic ionic crystals, etc. onto the first garnet-type oxide solid electrolyte.

[0046] The above-mentioned organic plastic ionic crystal may be a known organic plastic ionic crystal applicable to lithium secondary batteries, without particular limitation. As the above-mentioned organic plastic ionic crystal, an aliphatic quaternary ammonium salt containing a perfluoro anion can be cited, such as N,N-diethyl-N-methyl-N-propylammonium trifluoromethyltrifluoroborate (N 2,2,1,3 [BF3CF3]) analog, N-ethyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)amide (Py 1,2 [FSA]) analog, etc. It should be noted that from the viewpoint of electrochemical stability, the above-mentioned organic plastic ionic crystal is preferably N 2,2,1,3 [BF3CF3].

[0047] The above-mentioned ionic liquid may be a known ionic liquid applicable to lithium secondary batteries, without particular limitation. As the above-mentioned ionic liquid, for example, N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide (Py 1,3 [FSA]), N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)amide (Py 1,3 [TFSA]), N-ethyl-N-methylimidazolium bis(fluorosulfonyl)amide (]EMI[FSA]) can be cited. It should be noted that from the viewpoint of electrochemistry, the above-mentioned ionic liquid is preferably Py 1,3 [FSA].

[0048] Each process in the method for manufacturing the garnet-type oxide solid electrolyte of the present disclosure can be carried out in a drying chamber or a glove box. It is particularly preferred to carry out the above-mentioned heating and cooling process and contact process in a drying chamber. Thereby, the formation of lithium carbonate and lithium hydroxide on the surface of the first garnet-type oxide solid electrolyte due to the reaction of the first garnet-type oxide solid electrolyte with carbon dioxide and water can be suppressed. Preferably, the dew point of the above-mentioned drying chamber is -50°C or lower, and the environment of the glove box is a dew point of -70°C or lower and an inert gas atmosphere.

[0049] Examples

[0050] Next, the invention of the present disclosure will be described in more detail based on examples, but the invention of the present disclosure is not limited to the examples.

[0051] 1. Raw materials used

[0052] (LLZO powder)

[0053] · LLZO powder, median particle size (D50) 0.1 μm product

[0054] · LLZO powder, median particle size (D50) 1 μm product (manufactured by Toyoshima Seisakusho Co., Ltd.)

[0055] ·LLZO powder with median particle size (D50) of 8.9 μm (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd.)

[0056] ·LLZO powder with median particle size (D50) of 10 μm (manufactured by Toyoshima Seisakusho Co., Ltd.)

[0057] (Obtaining LLZO powder with median particle size (D50) of 0.1 μm)

[0058] The LLZO isopropanol suspension is prepared by pulverizing LLZO powder with median particle size (D50) of 1 μm (manufactured by Toyoshima Seisakusho Co., Ltd.) in isopropanol using a bead mill (Easynano (RMB type) (manufactured by Aimex Co., Ltd.)) with ZrO2 media particle size of φ0.1 mm. The LLZO powder with median particle size (D50) of 0.1 μm is obtained by removing isopropanol from the LLZO isopropanol suspension using an evaporator.

[0059] 2. Pressing and forming process

[0060] 1) Obtaining Intermediate 1

[0061] Intermediate 1 is obtained as follows: In a drying chamber with a dew point of -50°C or lower, 60 mg of LLZO powder with median particle size (D�) of 0.1 μm is put into a powder forming device with an inner diameter of 10 mm, and then the LLZO powder with median particle size (D50) of 0.1 μm is uniaxially pressed and formed at 433 MPa using a hydraulic press. The diameter of Intermediate 1 is 10 mm.

[0062] 1) Obtaining Intermediate 2

[0063] Intermediate 2 is manufactured using LLZO powder with median particle size (D50) of 1 μm. Intermediate 2 is obtained by treating in the same manner as the above-mentioned method for obtaining Intermediate 1, except that LLZO powder with median particle size (D50) of 1 μm is used instead of LLZO powder with median particle size (D50) of 0.1 μm. The diameter of Intermediate 2 is 10 mm.

[0064] 3) Obtaining Intermediate 3

[0065] Intermediate 3 is manufactured using LLZO powder with median particle size (D50) of 10 μm. Intermediate 3 is obtained by treating in the same manner as the above-mentioned method for obtaining Intermediate 1, except that LLZO powder with median particle size (D50) of 10 μm is used instead of LLZO powder with median particle size (D50) of 0.1 μm. The diameter of Intermediate 3 is 10 mm.

[0066] 3. Heating and cooling process

[0067] 1) Obtaining of the first garnet-type oxide solid electrolyte 1

[0068] The first garnet-type oxide solid electrolyte 1 is obtained by heating the above-mentioned intermediate 1 under the conditions in the above-mentioned drying chamber using a firing furnace under the conditions of "influence of heating temperature on ionic conductivity" described below, and then cooling it to room temperature in the furnace of the firing furnace for 2 to 4 hours. The diameter of the first garnet-type oxide solid electrolyte 1 becomes 8 mm to 9.5 mm, and it slightly shrinks compared to before firing.

[0069] 2) Obtaining of the first garnet-type oxide solid electrolyte 2

[0070] The first garnet-type oxide solid electrolyte 2 is manufactured using the above-mentioned intermediate 2. The first garnet-type oxide solid electrolyte 2 is obtained by treating it in the same manner as the above-mentioned "obtaining of the garnet-type oxide solid electrolyte 1" except that it is heated under the conditions of using the above-mentioned intermediate 2 and the "influence of heating time on ionic conductivity" and "influence of heating temperature on ionic conductivity" described below. The diameter of the first garnet-type oxide solid electrolyte 2 becomes 8 mm to 9.5 mm, and it slightly shrinks compared to before firing.

[0071] 3) Obtaining of the first garnet-type oxide solid electrolyte 3

[0072] The first garnet-type oxide solid electrolyte 3 is manufactured using the above-mentioned intermediate 3. The first garnet-type oxide solid electrolyte 3 is obtained by treating it in the same manner as the above-mentioned "obtaining of the garnet-type oxide solid electrolyte 1" except that it uses the above-mentioned intermediate 3. The diameter of the first garnet-type oxide solid electrolyte 3 becomes 8 mm to 9.5 mm, and it slightly shrinks compared to before firing.

[0073] 4. Measurement of ionic conductivity

[0074] To measure the ionic conductivity, a Li symmetric cell 1 was fabricated using a first garnet-type oxide solid electrolyte 1. Inside the Li symmetric cell 1, the first garnet-type oxide solid electrolyte 1 was sandwiched between two lithium disks (diameter 8 - 9 mm) under a pressure of approximately 1.5 N·m. The measurement of the ionic conductivity was carried out by the AC impedance method. The conditions for AC impedance measurement were an amplitude of 100 mV (appropriately increased up to 500 mV in cases where the resistance was too high and difficult to measure), and a scanning frequency of 32 MHz to 10 μHz. The Li symmetric cell 2 was fabricated by the same process as the Li symmetric cell 1, except that the first garnet-type oxide solid electrolyte 2 was used instead of the first garnet-type oxide solid electrolyte 1. The Li symmetric cell 3 was fabricated by the same process as the Li symmetric cell 1, except that the first garnet-type oxide solid electrolyte 3 was used instead of the 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 using the Li symmetric cell 2 and the Li symmetric cell 3 instead of the Li symmetric cell 1, by the same measurement method as the above-mentioned first garnet-type oxide solid electrolyte 1.

[0075] 5. Influence of Heating Time on Ionic Conductivity

[0076] 1) Obtaining Garnet-Type Oxide Solid Electrolyte 2 with Different Heating Times

[0077] The first garnet-type oxide solid electrolyte 2(0.5 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 30 minutes, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 2(1 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 1 hour, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 2(2 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 2 hours, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 2(4 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 4 hours, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 2(6 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 6 hours, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 2(8 h) is obtained through the following heating and cooling process: For intermediate 2, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, and after the heating time is set to 8 hours, it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours.

[0078] 2) Confirmation of the influence of heating time on ionic conductivity

[0079] Figure 1 are the measurement results of the ionic conductivity of the first garnet-type oxide solid electrolyte 2 with different heating times above. According to Figure 1 it can be seen that the ionic conductivities of the first garnet-type oxide solid electrolyte 2(2 h), the first garnet-type oxide solid electrolyte 2(4 h), and the first garnet-type oxide solid electrolyte 2(6 h) are 4.0×10 -5 S / cm or more. On the other hand, it can be seen that the ionic conductivities of 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) obtained by the treatment with heating times of 30 minutes, 1 hour, and 8 hours are less than 4.0×10 -5 S / cm, and the ionic conductivity decreases. In addition, according toFigure 1 , the first garnet-type oxide solid electrolyte 2 obtained by treatment with a heating time of 2 to 7 hours has a high ionic conductivity of 5.0×10 -5 S / cm or more.

[0080] 6. Influence of heating temperature on ionic conductivity

[0081] 1) Obtaining of the first garnet-type oxide solid electrolyte 1 with different heating temperatures

[0082] The first garnet-type oxide solid electrolyte 1 (800 °C) is obtained through the following heating and cooling process: For intermediate 1, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 800 °C, the heating time is set to 2 hours, and then it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 1 (900 °C) is obtained through the following heating and cooling process: For intermediate 1, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 900 °C, the heating time is set to 2 hours, and then it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 1 (1000 °C) is obtained through the following heating and cooling process: For intermediate 1, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1000 °C, the heating time is set to 2 hours, and then it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours. The first garnet-type oxide solid electrolyte 1 (1100 °C) is obtained through the following heating and cooling process: For intermediate 1, under the conditions in the above drying chamber, using a firing furnace, the heating temperature is set to 1100 °C, the heating time is set to 2 hours, and then it is cooled to room temperature in the furnace of the firing furnace in 2 to 4 hours.

[0083] 2) Obtaining of the first garnet-type oxide solid electrolytes 2 and 3 with different heating temperatures

[0084] By using intermediate 2, except using intermediate 2 instead of intermediate 1, through the same method as the above "Obtaining of the garnet-type oxide solid electrolyte 1 with different heating temperatures", the first garnet-type oxide solid electrolyte 2 (800 °C), the first garnet-type oxide solid electrolyte 2 (900 °C), the first garnet-type oxide solid electrolyte 2 (1000 °C), and the first garnet-type oxide solid electrolyte 2 (1100 °C) with different heating temperatures are obtained. Similarly, by using intermediate 3, the first garnet-type oxide solid electrolyte 3 (800 °C), the first garnet-type oxide solid electrolyte 3 (900 °C), the first garnet-type oxide solid electrolyte 3 (1000 °C), and the first garnet-type oxide solid electrolyte 3 (1100 °C) with different heating temperatures are obtained.

[0085] 3) Confirmation of the effect of heating temperature on ionic conductivity

[0086] Figure 2 are the measurement results of the ionic conductivities of the first garnet-type oxide solid electrolytes 1 to 3 with different heating temperatures above. According to Figure 2 , when the heating temperature is 800 °C, 900 °C, and 1000 °C, the first garnet-type oxide solid electrolyte 1 has a higher ionic conductivity compared to 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 (about 1.4×10 -4 S / cm) is significantly higher than the ionic conductivities of the first garnet-type oxide solid electrolyte 2 (about 5.0×10 -5 S / cm) and 3 (about 4.0×10 -5 S / cm).

[0087] The first garnet-type oxide solid electrolyte 1 is a first garnet-type oxide solid electrolyte manufactured using LLZO powder with a median particle size (D50) of 0.1 μm. On the other hand, the first garnet-type oxide solid electrolytes 2 and 3 are first garnet-type oxide solid electrolytes manufactured using LLZO powder with median particle sizes (D50) of 1 μm and 10 μm, respectively. That is, according to Figure 2 , when the heating temperature is 950 to 1050 °C, the first garnet-type oxide solid electrolyte manufactured using LLZO powder with a median particle size (D50) of 0.02 to 0.2 μm has a significantly higher ionic conductivity compared to the first garnet-type oxide solid electrolyte manufactured using LLZO powder with a median particle size (D50) of 1 μm or more.

Claims

1. A method for manufacturing a garnet-type oxide solid electrolyte, wherein, Pressurize and form Li7La3Zr2O powder with a median particle size (D50) of 0.02 to 0.2 μm to obtain an intermediate product. 12 ​ The intermediate is heated at 950 to 1050 °C for 2 to 7 hours and then cooled for 4 hours or more until room temperature to obtain a first garnet-type oxide solid electrolyte.

2. The manufacturing method of the garnet-type oxide solid electrolyte according to claim 1, wherein, At least one selected from organic plastic ionic crystals and ionic liquids is brought into contact with the first garnet-type oxide solid electrolyte to obtain a second garnet-type oxide solid electrolyte.

3. The method for manufacturing a garnet-type oxide solid electrolyte according to claim 1 or 2, wherein, Press the Li7La3Zr2O 12 powder under a condition of 72 MPa or more to obtain the intermediate product.

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