KR20220120979A - Method of preparing llzo solid electrolyte, llzo solid electrolyte and all solid state lithium ion battery comprising the same - Google Patents

Abstract

The present invention relates to a method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte, and an all-solid-state lithium secondary battery including the same. The method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention comprises the following steps of: preparing a first sol composition by adding a first substitutional doping material to a first mixed solution in which a Li raw material and La raw material are dissolved in a solvent, and then synthesizing the same in a sol form; preparing a second sol composition by adding a second substitutional doping material to a second mixed solution in which a Zr raw material and a catalyst are dissolved in a solvent, and then synthesizing the same in a sol form; gelating the first sol composition and the second sol composition, respectively, and then pre-calcining the same to prepare respective powders; milling, mixing, pulverizing, and calcining the respective powders to form a substitution material-doped LLZO powder; and molding the substitution material-doped LLZO powder to form a molded body, and sintering the molded body. According to the present invention, composition change of the solid electrolyte is easy, and a process is possible at low temperature to prevent degradation of properties of the LLZO material.

Description

Lithium lanthanum zirconium oxide (LLZO) solid electrolyte manufacturing method, lithium lanthanum zirconium oxide (LLZO) solid electrolyte and all-solid lithium secondary battery comprising the same THE SAME}

The present invention relates to a method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte, a lithium lanthanum zirconium oxide (LLZO) solid electrolyte, and an all-solid lithium secondary battery comprising the same.

The lithium-ion battery market is growing steadily in line with the recent expansion of the electric vehicle market and increased demand and interest in energy storage systems (ESS). In the case of a lithium ion battery using a liquid electrolyte that is conventionally used, there is a risk for safety such as explosion and ignition due to leakage and expansion.

On the other hand, since all-solid-state batteries use solid electrolyte, there is no risk of leakage or expansion, so safety is excellent. Accordingly, research is being actively conducted. Among the various solid electrolyte materials, cubic Li _x La ₃ M ₂ O ₁₂ (M=Ta, Nb, Zr) with a garnet structure has thermal and electrochemical stability, relatively small intergranular resistance, and high ionic conductivity (~10 ^-4 S/cm) and stability with lithium anodes, it is attracting attention as a solid electrolyte for next-generation batteries.

The conventional solid-phase synthesis method for synthesizing LLZO has a problem in that, due to the high sintering temperature and the long sintering time of 24 hours or more, the ionic conductivity decreases due to the increase of voids as lithium volatilizes, and it can have an unstable chemical composition ratio including a secondary phase.

Accordingly, there is a need for research to solve the limitations in the process leading to deterioration of the properties of the material.

The present invention is to solve the above-mentioned problems, an object of the present invention is lithium lanthanum zirconium oxide (LLZO) solid that can prevent deterioration of the properties of the LLZO material by enabling easy composition change and processing at a low temperature To provide a method for manufacturing an electrolyte, a lithium lanthanum zirconium oxide (LLZO) solid electrolyte, and an all-solid-state lithium secondary battery comprising the same.

However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In the method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention, a first substitution doping material is added to a first mixed solution in which a Li raw material and a La raw material are dissolved in a solvent, and then a sol preparing a first sol composition by synthesizing it in the form; preparing a second sol composition by adding a second substitution doping material to a second mixed solution in which a Zr raw material and a catalyst are dissolved in a solvent and then synthesizing it in a sol form; preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively; milling each of the powders, mixing and pulverizing, and calcining to form a substitution material-doped LLZO powder; and forming the substitution material-doped LLZO powder to form a green body, and sintering the green body.

In one embodiment, the first substitution doping material is aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium It may include at least one selected from the group consisting of (Ce) and rubidium (Rb).

In one embodiment, the second substitution doping material is at least selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb), and tantalum (Ta). It may include any one.

In one embodiment, the solvent is n-propyl alcohol, 2-methoxyethanol, ethanol, methanol, 1-propanol, iso-butanol, tert-butanol, 1-butanol, 2-propanol, 2-butanol, 1 - It may include at least one selected from the group consisting of decanol, phenol, 2-butanone, ethyl acetate, toluene, and heptane.

In one embodiment, the catalyst is nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, chlorosulfonic acid, iodic acid, tartaric acid, perchloric acid, polyphosphoric acid, pyrophosphoric acid, para-toluic acid, trichloroacetic acid, formic acid, acetic acid and citric acid At least one acid catalyst selected from the group consisting of; or sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, n-butylamine, di-n-butylamine, tri-n-butylamine, imidazole, and at least one basic catalyst selected from the group consisting of ammonium perchlorate may be doing

In one embodiment, after preparing the first sol composition and preparing the second sol composition, respectively, the first sol composition and the second sol composition are aged for 6 hours to 24 hours ( aging) may be further included.

In one embodiment, the gelation of the first sol composition and the second sol composition may be dried in a drying furnace at 100°C to 200°C for 3 hours to 12 hours.

In one embodiment, the step of preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively, at 400°C to 500°C for 3 hours to 12 hours it may be performing

In an embodiment, the calcination may be performed at 700° C. to 950° C. for 3 hours to 12 hours.

In one embodiment, the milling is selected from the group consisting of a ball mill, a vibration mill, a jet mill, a bead mill, and an attrition mill. It may be carried out for 12 hours to 36 hours using at least one method.

In one embodiment, before the step of sintering the compact, cold isostatic pressing (CIP) applying a pressure of 200 MPa to 300 MPa to the compact, or 10 MPa to 20 MPa at a high temperature of 1000 ° C. or higher It may be to perform hot isostatic pressing (HIP) applying pressure.

In one embodiment, the sintering may be performed at 900 °C to 1100 °C for 3 hours to 12 hours.

A lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to another embodiment of the present invention is represented by the following Chemical Formula 1:

[Formula 1]

Li _7-x A _x La _3-y B _y Zr _{2 z} M _z O ₁₂

(where 0<x≤1, 0≤y≤1, 0<z≤1, A is a Li substitution doping element, B is a La substitution doping application, M is a Zr substitution doping element, A and B are, from the group consisting of aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce) and rubidium (Rb), respectively At least one selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb) and tantalum (Ta) to include).

In one embodiment, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte may be prepared by the method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention.

An all-solid-state lithium secondary battery according to another embodiment of the present invention, an electrolyte layer comprising a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention; a positive electrode including a positive active material; and an anode including an anode active material.

According to the lithium lanthanum zirconium oxide (LLZO) solid electrolyte manufacturing method according to an embodiment of the present invention, synthesized in each sol form using the sol-gel method, then powdered, and then manufactured by the solid-phase synthesis method. It is possible to form a stabilized cubic phase by suppressing the generation of a secondary phase due to the generation of La _-2 -Zr ₂ O ₇ . In addition, by performing a pre-calcination process in the form of a sol by adding a substitution doping material to the mixed solution, the impurity content is lowered by removing the residual solvent and organic matter contained in the material, thereby secondary By inhibiting phase expression, deterioration of properties can be prevented.

In addition, it is possible to produce a small and uniform nano-sized precursor powder with an easy composition change, so that a solid electrolyte with excellent ionic conductivity can be produced even in a low-temperature sintering process. It is expected to overcome the process limitations of loss and secondary phase generation.

The lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention may have a stabilized cubic phase without a secondary phase.

1 is a process flow chart for explaining a method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention.
Figure 2 is a process flow chart for explaining the (Al, Ta) LLZO pellet manufacturing method according to an embodiment of the present invention.
3 is a process flow chart for explaining the LCO cathode deposition on (Al, Ta) LLZO according to an embodiment of the present invention.
4 is a SEM image of a raw material powder prepared by a sol-gel method according to an embodiment of the present invention.
5 is an optical image of the LLZO solid electrolyte sintered body prepared according to an embodiment of the present invention.
6 is a graph showing the XRD analysis result of the LLZO solid electrolyte sintered body prepared according to an embodiment of the present invention.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes may be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all modifications, equivalents and substitutes for the embodiments are included in the scope of the rights.

Terms used in the examples are used for the purpose of description only, and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

In addition, in the description with reference to the accompanying drawings, the same components are assigned the same reference numerals regardless of the reference numerals, and the overlapping description thereof will be omitted. In the description of the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms.

Components included in one embodiment and components having a common function will be described using the same names in other embodiments. Unless otherwise stated, descriptions described in one embodiment may be applied to other embodiments as well, and detailed descriptions within the overlapping range will be omitted.

Hereinafter, a method for manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte of the present invention, a lithium lanthanum zirconium oxide (LLZO) solid electrolyte, and an all-solid lithium secondary battery including the same will be described in detail with reference to Examples and drawings. . However, the present invention is not limited to these examples and drawings.

In the method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention, a first substitution doping material is added to a first mixed solution in which a Li raw material and a La raw material are dissolved in a solvent, and then a sol preparing a first sol composition by synthesizing it in the form; preparing a second sol composition by adding a second substitution doping material to a second mixed solution in which a Zr raw material and a catalyst are dissolved in a solvent and then synthesizing it in a sol form; preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively; milling each of the powders, mixing and pulverizing, and calcining to form a substitution material-doped LLZO powder; and forming a compact by molding the substitution material-doped LLZO powder, and sintering the compact.

1 is a process flow chart for explaining a method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention.

Referring to FIG. 1 , the method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention includes a first sol composition preparation step 110 , a second sol composition preparation step 120 , and powder preparation. Step 130 , calcining to form a displacement material-doped LLZO powder 140 , and sintering 150 .

In one embodiment, in the first sol composition preparation step 110, a first substitution doping material is added to a first mixed solution in which a Li raw material and a La raw material are dissolved in a solvent, and then synthesized in a sol form. It is a step of preparing the first sol composition.

In one embodiment, the Li raw material, Lithium nitrate hydrate (LiNO ₃ · x H ₂ O), Lithium nitrate (LiNO ₃ ), Lithium hydroxide (LiOH) and Lithium carbonate (Li ₂ CO ₃ ) Selected from the group consisting of It may be to include at least any one of.

In one embodiment, the raw material La, Lanthanum nitrate hydrate (La(NO ₃ ) ₃ · x H ₂ O, may be one containing.

In one embodiment, the solvent is n-propyl alcohol, 2-methoxyethanol, ethanol, methanol, 1-propanol, iso-butanol, tert-butanol, 1-butanol, 2-propanol, 2-butanol, 1 - It may include at least one selected from the group consisting of decanol, phenol, 2-butanone, ethyl acetate, toluene, and heptane.

In one embodiment, the first substitution doping material is aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium It may include at least one selected from the group consisting of (Ce) and rubidium (Rb).

Preferably, the first substitutional doping material may be aluminum (Al).

In an embodiment, the first substitution doping material may include aluminum oxide (Al ₂ O ₃ ).

In one embodiment, the first substitutional doping material may be one or two. For example, when the first substituted doping material is A or B, the first sol composition may be an A or B-doped sol.

In one embodiment, in the second sol composition preparation step 120, a second substituted doping material is added to a second mixed solution in which a Zr raw material and a catalyst are dissolved in a solvent, and then synthesized in a sol form to form a second sol composition. is the stage of preparation.

In an embodiment, the Zr raw material may include zirconium(IV) propoxide (Zr(OC ₃ H ₇ ) ₄ .

In one embodiment, the solvent is n-propyl alcohol, 2-methoxyethanol, ethanol, methanol, 1-propanol, iso-butanol, tert-butanol, 1-butanol, 2-propanol, 2-butanol, 1 - It may include at least one selected from the group consisting of decanol, phenol, 2-butanone, ethyl acetate, toluene, and heptane.

In one embodiment, the catalyst is nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, chlorosulfonic acid, iodic acid, tartaric acid, perchloric acid, polyphosphoric acid, pyrophosphoric acid, para-toluic acid, trichloroacetic acid, formic acid, acetic acid and citric acid At least one acid catalyst selected from the group consisting of; or sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, n-butylamine, di-n-butylamine, tri-n-butylamine, imidazole, and at least one basic catalyst selected from the group consisting of ammonium perchlorate may be doing

In one embodiment, the second substitution doping material is at least selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb), and tantalum (Ta). It may include any one.

Preferably, the second substitution doping material may be tantalum (Ta).

In an embodiment, the second substitution doping material may include tantalum(V) ethoxide (Ta(OC ₂ H ₅ ) ₅ .

In one embodiment, the second substitutional doping material may be one. For example, when the second substitution doping material is M, the second sol composition may be an M-doped sol.

In one embodiment, the substitution doping material to be added to the first mixed solution and the second mixed solution is Al ³⁺ , Ga ³⁺ , Ba ²⁺ or Ge ⁴⁺ for Li ⁺ sites; La ³⁺ sites are Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Sr ²⁺ , K ⁺ , Ce ⁴⁺ or Rb ⁺ ; Zr ⁴⁺ The site may include at least one selected from the group consisting of Mo ⁶⁺ , W ⁶⁺ , Sb ⁵⁺ , Y ³⁺ , Nb ⁵⁺ or Ta ⁵⁺ .

In one embodiment, the first substitutional doping material and the second substitutional doping material may be single, double, or triple doped according to a compositional design. Li ⁺ ion diffusion by substitution at each site And it shows the effect of improving the ion conductivity by expanding the pathway.

In one embodiment, after preparing the first sol composition and preparing the second sol composition, respectively, the first sol composition and the second sol composition are aged for 6 hours to 24 hours ( aging) may be further included.

In one embodiment, the powder preparation step 130 is a step of preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively.

In one embodiment, the gelation of the first sol composition and the second sol composition may be dried in a drying furnace at 100°C to 200°C for 3 hours to 12 hours. When the drying temperature is less than 100 °C, gelation of the first sol composition and the second sol composition may not be insignificant, and when the drying temperature is higher than 200 °C, there is a possibility that an unwanted reaction may occur.

In one embodiment, the step of preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively, at 400°C to 500°C for 3 hours to 12 hours it may be performing When the pre-calcination temperature is less than 400 ° C, residual solvents or organic matter remain and the impurity content is high, resulting in the expression of a secondary phase, which may deteriorate properties. Burning problems may occur.

In one embodiment, the calcining step 140 to form a displacement substance-doped LLZO powder is a step of milling the respective powders to mix and pulverize and calcinate to form a displacement substance-doped LLZO powder.

In one embodiment, the milling is selected from the group consisting of a ball mill, a vibration mill, a jet mill, a bead mill, and an attrition mill. It may be carried out for 12 hours to 36 hours using at least one method.

Preferably, it may be grinding for 24 hours or more using a ball milling method.

In one embodiment, in the ball milling process, 1 wt% to 30 wt%, preferably, 10 to 15 wt% excess of Li may be included in the powder than the content of Li element. This may be an excessive addition of the Li raw material used as the starting raw material in order to compensate for the loss of Li.

In an embodiment, the calcination may be performed at 700° C. to 950° C. for 3 hours to 12 hours. If the calcination temperature is less than 700 ℃, the reaction between the materials may not be made, so synthesis may not be made. there may be

In an embodiment, the sintering step 150 is a step of forming a green body by molding the substitution material-doped LLZO powder, and sintering the green body.

In one embodiment, the substitution material-doped LLZO powder is, for example, using a hydraulic press at a pressure of 3 MPa to 100 MPa by molding the substitution material-doped LLZO powder in the form of pellets. it could be

In one embodiment, before the step of sintering the compact, cold isostatic pressing (CIP) applying a pressure of 200 MPa to 300 MPa to the compact, or 10 MPa to 20 MPa at a high temperature of 1000 ° C. or higher It may be to perform hot isostatic pressing (HIP) applying pressure.

The compact may be made more dense by the cold isostatic pressing and the hot isostatic pressing.

In one embodiment, the sintering may be performed at 900 °C to 1100 °C for 3 hours to 12 hours. When the sintering temperature is less than 900 ° C, crystallization is not performed properly due to the low sintering temperature, so there may be a problem that low density and properties are lowered, and when it is more than 1100 ° C, Li volatilizes and ionic conductivity decreases due to an increase in voids, There may be a problem in that Li segregation occurs outside the LLZO particles to form a tetragonal LLZO rather than a stable cubic LLZO.

In one embodiment, in order to prevent the loss of Li, the LLZO solid electrolyte may be prepared by covering the molded body with the same kind of powder and performing final sintering.

In one embodiment, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte prepared after the sintering may be AB-doped LLZMO pellets.

In one embodiment, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte may be represented by the following Chemical Formula 1:

[Formula 1]

Li _7-x A _x La _3-y B _y Zr _{2- z} M _z O ₁₂

(where 0<x≤1, 0≤y≤1, 0<z≤1, A is a Li substitution doping element, B is a La substitution doping application, M is a Zr substitution doping element, A and B are, from the group consisting of aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce) and rubidium (Rb), respectively At least one selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb) and tantalum (Ta) to include).

According to the lithium lanthanum zirconium oxide (LLZO) solid electrolyte manufacturing method according to an embodiment of the present invention, it is synthesized in each sol form using the sol-gel method and then powdered and then manufactured by the solid phase synthesis method. It is possible to form a stabilized cubic phase by suppressing the generation of a secondary phase due to the generation of La _-2 -Zr ₂ O ₇ . In addition, by performing a pre-calcination process in the form of a sol by adding a substitution doping material to the mixed solution, the impurity content is lowered through the removal of residual solvents and organic matter contained in the material, thereby secondary in the subsequent process. By inhibiting phase expression, deterioration of properties can be prevented.

A lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to another embodiment of the present invention is represented by the following Chemical Formula 1:

[Formula 1]

Li _7-x A _x La _3-y B _y Zr _{2- z} M _z O ₁₂

(where 0<x≤1, 0≤y≤1, 0<z≤1, A is a Li substitution doping element, B is a La substitution doping application, M is a Zr substitution doping element, A and B are, from the group consisting of aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce) and rubidium (Rb), respectively At least one selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb) and tantalum (Ta) to include).

In one embodiment, the substitution doping material to be added to the mixed solution is Al ³⁺ , Ga ³⁺ , Ba ²⁺ or Ge ⁴⁺ for Li ⁺ sites; La ³⁺ sites are Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Sr ²⁺ , K ⁺ , Ce ⁴⁺ or Rb ⁺ ; Zr ⁴⁺ The site may include at least one selected from the group consisting of Mo ⁶⁺ , W ⁶⁺ , Sb ⁵⁺ , Y ³⁺ , Nb ⁵⁺ and Ta ⁵⁺ .

In one embodiment, the substitution doping material may be single, double, or triple doped according to the compositional design. By substituting at each site, the effect of improving ion conductivity is improved by Li ⁺ ion diffusion and pathway expansion. see.

In one embodiment, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte may be prepared by the method of manufacturing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention.

The lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention may have a stabilized cubic phase without a secondary phase.

An all-solid-state lithium secondary battery according to another embodiment of the present invention, an electrolyte layer comprising a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to an embodiment of the present invention; a positive electrode including a positive active material; and an anode including an anode active material.

Hereinafter, the present invention will be described in more detail by way of Examples.

However, the following examples are only for illustrating the present invention, and the content of the present invention is not limited to the following examples.

[Example]

Preparation of LLZO Pellets Doped with Al and Ta Using the Sol-Gel Method

Lithium nitrate hydrate (LiNO ₃ xH ₂ O, 99.999 %, Alfa Aesar), lanthanum nitrate hydrate (La(La() NO ₃ ) ₃ xH ₂ O, 99.9 %, Sigma Aldrich), zirconium (IV) propoxide (zirconium(IV) propoxide) (Zr(OC ₃ H ₇ ) ₄ , 70 wt. % in 1-propanol, Sigma Aldrich), tantalum (V) ethoxide (Ta (OC ₂ H ₅ ) 5, 99.98 %, Sigma Aldrich) and aluminum oxide (Al ₂ O ₃ , 20 wt. % in isopropanol, Sigma Aldrich) was used. To effectively dissolve the raw materials, 1-propanol (CH ₃ CH ₂ CH ₂ OH, anhydrous 99.7%, Sigma Aldrich) and 2-methoxyethanol (2-MOE, CH ₃ OCH ₂ CH ₂ OH, anhydrous 99.8 %, Sigma Aldrich) ) was used. Acetic acid (AC, CH ₃ COOH, Sigma Aldrich) was used as a chelating agent to promote sol-gel formation. The chemical composition of the sol-gel powder Li _x Al _y La ₃ Zr _2-z Ta _z O ₁₂ varied as x = 6.2, 6.82, 7.44 and 8.06 mol and y = z = 0.2 mol.

Figure 2 is a process flow chart for explaining the (Al, Ta) LLZO pellet manufacturing method according to an embodiment of the present invention.

Referring to FIG. 2, LLZO sol doped with Al and Ta was gelled to produce a powder, and then pellets were prepared by sintering. After aging for 12 hours, the gel was dried on a hot plate at 160 °C for 9 hours. In order to remove the solution remaining in the synthesized gel together with volatile components, it was pre-calcined at 450 °C for 4 hours and then calcined at 950 °C for 4 hours. The calcined gel was ground in a mortar and ball milled for 24 hours. Then, 10 mm pellets were fabricated using a hydraulic press applied with a cold isostatic press (CIP), and the pellets were pressed at 300 MPa for 2 minutes. The final sintering step was carried out at 1100 °C for 4 hours. In order to prevent lithium loss on the surface during high-temperature sintering, powder of the same composition as the pellets was applied to the upper and lower portions of the pellets.

Preparation of LCO negative electrode by sol-gel and slurry method

3 is a process flow chart for explaining the LCO cathode deposition on (Al, Ta) LLZO according to an embodiment of the present invention.

As shown in Fig. 3, the LCO cathode was fabricated using two different methods and then used for cell measurements. In the first method, 0.8 M LiCoO ₂ (Quintess Co., Korea) was spin-coated on the LLZO solid electrolyte. Before coating with LCO, LLZO pellets were polished with 2000 grit paper to remove scratches on the surface, and then heat treatment at 450 ° C. for 5 minutes to remove residual organic matter. Next, the LCO solution was evenly sprayed onto the LLZO solid electrolyte and spin-coated at 500 rpm for 5 s and 2000 rpm for 25 s. To prevent cracking of the LCO-coated LLZO electrolyte due to thermal stress, several heat treatment steps were performed: 120 °C for 10 min, 300 °C for 7 min, and 650 °C for 5 min. After repeating the spin coating and heat treatment process 10 times, the final heat treatment was performed at 650 °C for 1 hour to form an LCO cathode.

The second method was to tape-cast LCO powder to the surface of LLZO pellets using the slurry method to prepare the negative electrode. The slurry was mixed with lithium cobalt oxide (LiCoO ₂ , 99.8%, Sigma Aldrich) in polyvinylidene fluoride (PVDF, (CH ₂ CF ₂ ) _n , Sigma Aldrich) as binder and conductive additive carbon black (Alfa Aesar) was composed of These ingredients were mixed in a 95:3:2 ratio. The prepared solid powder (60% by weight) was dissolved in N -methylpyrrolidinone (NMP, anhydrous 99.5%, C ₅ H ₉ NO, Sigma Aldrich) for 12 hours and then Al using a doctor blade method. coated on foil. The obtained slurry was dried at 120 °C for 5 hours to obtain a final LCO negative electrode.

4 is a SEM image of a raw material powder prepared by a sol-gel method according to an embodiment of the present invention.

Referring to the SEM image of FIG. 4 , it can be confirmed that small and fine raw material powder having an average particle size of 200-500 nm is produced.

Figure 5 is an optical image of the LLZO solid electrolyte sintered body prepared according to an embodiment of the present invention, Figure 6 is a graph showing the XRD analysis results of the LLZO solid electrolyte sintered body prepared according to the embodiment of the present invention.

5 and 6, looking at the XRD analysis results of the sintered body, it can be seen that the manufactured LLZO forms a stable cubic phase without generation of a secondary phase.

As described above, although the embodiments have been described with reference to the limited drawings, those skilled in the art may apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order than the described method, and/or the described components of the system, structure, apparatus, circuit, etc. are combined or combined in a different form than the described method, or other components Or substituted or substituted by equivalents may achieve an appropriate result.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (14)

preparing a first sol composition by adding a first substitution doping material to a first mixed solution in which a Li raw material and a La raw material are dissolved in a solvent and then synthesizing it in a sol form;
preparing a second sol composition by adding a second substitution doping material to a second mixed solution in which a Zr raw material and a catalyst are dissolved in a solvent and then synthesizing it in a sol form;
preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively;
milling each of the powders, mixing and pulverizing, and calcining to form a substitution material-doped LLZO powder; and
forming a green body by molding the substitution material-doped LLZO powder, and sintering the green body;
containing,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The first substitutional doping material is aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce) and rubidium ( Rb) comprising at least one selected from the group consisting of,
The second substitution doping material includes at least one selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb), and tantalum (Ta) sign,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The solvent is n-propyl alcohol, 2-methoxyethanol, ethanol, methanol, 1-propanol, iso-butanol, tert-butanol, 1-butanol, 2-propanol, 2-butanol, 1-decanol, phenol, 2-butanone, including at least one selected from the group consisting of ethyl acetate, toluene and heptane,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The catalyst is
At least one selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, chlorosulfonic acid, iodic acid, tartaric acid, perchloric acid, polyphosphoric acid, pyrophosphoric acid, para-toluic acid, trichloroacetic acid, formic acid, acetic acid and citric acid acid catalyst; or
At least one basic catalyst selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, n-butylamine, di-n-butylamine, tri-n-butylamine, imidazole and ammonium perchlorate that is,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
After preparing the first sol composition and preparing the second sol composition, respectively,
aging the first sol composition and the second sol composition for 6 hours to 24 hours;
further comprising,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
Gelation of the first sol composition and the second sol composition,
It will be dried in a drying furnace at 100 ° C. to 200 ° C. for 3 hours to 12 hours,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The steps of preparing each powder by pre-calcining after gelation of the first sol composition and the second sol composition, respectively,
which is carried out at 400 ° C. to 500 ° C. for 3 hours to 12 hours,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The calcination is
Which is carried out at 700 ° C. to 950 ° C. for 3 hours to 12 hours,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The milling is at least one method selected from the group consisting of a ball mill, a vibration mill, a jet mill, a bead mill, and an attrition mill. It is carried out for 12 hours to 36 hours using
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
Prior to the step of sintering the compact,
Cold Isostatic Pressing (CIP) for applying a pressure of 200 MPa to 300 MPa to the molded body, or
To perform hot isostatic pressing (HIP) applying a pressure of 10 MPa to 20 MPa at a high temperature of 1000 ° C. or higher,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
According to claim 1,
The sintering is
Which is carried out at 900 ° C. to 1100 ° C. for 3 hours to 12 hours,
A method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
A lithium lanthanum zirconium oxide (LLZO) solid electrolyte represented by the following formula (1):
[Formula 1]
Li _7-x A _x La _3-y B _y Zr _{2- z} M _z O ₁₂
(where 0<x≤1, 0≤y≤1, 0<z≤1, A is a Li substitution doping element, B is a La substitution doping application, M is a Zr substitution doping element, A and B are, from the group consisting of aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce) and rubidium (Rb), respectively At least one selected from the group consisting of molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb) and tantalum (Ta) to include).
13. The method of claim 12,
The lithium lanthanum zirconium oxide (LLZO) solid electrolyte is prepared by the method for preparing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte according to any one of claims 1 to 11,
Lithium lanthanum zirconium oxide (LLZO) solid electrolyte.
An electrolyte layer comprising the lithium lanthanum zirconium oxide (LLZO) solid electrolyte of claim 12;
a positive electrode comprising a positive electrode active material; and
a negative electrode comprising an anode active material;
comprising,
All-solid-state lithium secondary battery.

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