Lithium lanthanum zirconium oxide solid electrolyte prepared using high-frequency focused homogenization synthesis method, and preparation method therefor

Abstract

The present invention relates to a lithium lanthanum zirconium oxide solid electrolyte prepared using a high-frequency focused homogenization synthesis method, and a preparation method therefor. The solid electrolyte of the present invention comprises lithium lanthanum zirconium oxide (LLZO) doped or not doped with a dissimilar metal, wherein the dissimilar metal includes one or more selected from the group consisting of aluminum and gallium. In addition, the preparation method for the solid electrolyte of the present invention uses a precursor mixed solution comprising a zirconium precursor, a dissimilar metal precursor, a lithium precursor, and a lanthanum precursor all in a solvent, and thus enables the simple preparing of a solid electrolyte without a process of adding an additional additive, e.g., a lithium source, in a subsequent process.

Description

Lithium lanthanum zirconium oxide solid electrolyte manufactured using high-frequency focused homogenization synthesis method and manufacturing method thereof

[0001] The present invention relates to a lithium lanthanum zirconium oxide solid electrolyte manufactured using a high-frequency focused homogenization synthesis method and a method for manufacturing the same.

[0002] Lithium secondary batteries are experiencing growing demand for applications such as mobile information terminals, portable electronic devices, small home power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles due to their large electrochemical capacity, high operating potential, and excellent charge-discharge cycling characteristics. This growing demand for lithium-ion batteries is driving the pursuit of lower prices, higher stability, higher capacity, and larger surface areas.

[0003] However, lithium-ion batteries using existing liquid electrolytes have safety issues due to the high possibility of leakage and ignition, and these safety issues are becoming more of an issue as batteries become larger in capacity and area.

[0004] Accordingly, research on all-solid-state secondary batteries (all-solid-state lithium-ion batteries) using inorganic solid electrolytes, which are non-combustible materials, is being actively conducted to increase the capacity of lithium-ion batteries while ensuring their stability. All-solid-state secondary batteries are attracting attention as next-generation secondary batteries in terms of safety, high energy density, high output, long life, simplification of the manufacturing process, and large / compact and low-cost batteries.

[0005] All-solid-state lithium secondary batteries are composed of anode / solid electrolyte layer / cathode, and among these, the solid electrolyte of the solid electrolyte layer requires high ionic conductivity and low electronic conductivity. In addition, the components of the electrode layers, the cathode and anode layers, also include solid electrolytes, and a mixed-conductivity material with high ionic and electronic conductivity is advantageous for the solid electrolyte used in the electrode layers. Inorganic solid electrolytes include sulfides and oxides, and sulfide-based solid electrolytes have the disadvantage of reacting with moisture in the air, making it difficult to control the process atmosphere and causing side reactions at the interface with the electrode. In contrast, oxide-based solid electrolytes have high stability in moisture and the air. Oxide-based solid electrolytes include LLTO(Li 3x La 2 / (3-x) TiO3) system and LLZO(Li7La3Zr2O 12 ) are known, and LLTO has a disadvantage of low overall ionic conductivity due to high resistance at grain boundaries, but on the other hand, LLZO has a wide potential window characteristic and low resistance at grain boundaries compared to LLTO, so it has high overall ionic conductivity, and therefore LLZO is attracting attention as a promising material. LLZO-based solid electrolytes have a tetragonal or cubic structure, and the cubic structure is known to have an ionic conductivity about 100 times higher than the tetragonal structure. LLZO with a cubic structure exhibits high ionic conductivity because the lithium ions in the octahedral sites exist in a twisted form, so the short distance from the lithium ions in the tetrahedral sites and the three-dimensional ion-conducting channel structure. On the other hand, it is known that tetragonal LLZO has a well-ordered lithium ion structure, which makes the distance between ions longer and has a two-dimensional ion conduction channel structure, which results in lower ionic conductivity than cubic LLZO.

[0006] For this reason, in order to have high ionic conductivity, a cubic structure must be formed, but the cubic structure is unstable at room temperature and requires a high sintering temperature of over 1,200℃. Such a high temperature also causes lithium volatilization, resulting in a decrease in the concentration of lithium ions. For this reason, in order to stabilize the cubic structure at room temperature, Al is added to the existing lithium ion site. 3+ , Ga 3+ , Fe 3+ , B 3+ When cations such as these are doped and substituted for lithium, entropy increases, free energy decreases, and the cubic structure can be stabilized. In addition, although it is difficult to synthesize cubic LLZO without doping, it has been reported that it is possible to synthesize cubic LLZO without doping when the particle size is small. The solid-state reaction method is a conventional method for synthesizing LLZO powder. The solid-state reaction method has the disadvantage of a long synthesis process time and a high temperature of 1,000 ℃ or higher, which increases the particle size of the powder and reduces the sinterability during sintering, which lowers the electrochemical properties (ionic conductivity). In this way, electrochemical properties such as ionic conductivity are proportional to the particle size of the powder and the resulting sinterability, so there is a need for the development of a technology that can further refine the particle size of the powder, and a new synthesis method that pursues reduction and simplification of the process time is also needed.

[0007] The purpose of the present invention is to solve the above problems, and to provide LLZO doped or undoped with a heterometal, for example, Ga or Al, having high ionic conductivity by controlling the time and / or heat treatment temperature of a high-frequency focused homogenization synthesis method.

[0008] Another object of the present invention is to provide a manufacturing method capable of simply manufacturing LLZO without a post-process of additionally supplying a lithium source by using a precursor mixture solution containing a zirconium precursor, a heterometal precursor, a lithium precursor, and a lanthanum precursor all in a solvent.

[0009] According to one aspect of the present invention, a solid electrolyte is provided, which is represented by the following chemical formula 1 and includes lithium lanthanum zirconium oxide (LLZO) doped or undoped with a heterometal, wherein the heterometal includes at least one selected from the group consisting of aluminum and gallium.

[0010] [Chemical Formula 1]

[0011] Li x Ga y1 Al y2 La z Zr w O 12

[0012] In chemical formula 1, 5≤x≤9, 0≤y1≤1, 0≤y2≤1, 2≤z≤4, and 1≤w≤3.

[0013] Additionally, the solid electrolyte may be in powder form, and the size of the powder may be 1 to 20 nm.

[0014] Additionally, the size of the powder may have a full width at half maximum of 0.5 to 10 nm.

[0015] Additionally, the size distribution of the powder may be a single-rod distribution.

[0016] In addition, the above chemical formula 1 can be expressed by the following chemical formula 2.

[0017] [Chemical Formula 2]

[0018] Li x Ga y1 La z Zr w O 12

[0019] In chemical formula 2, 5≤x≤9, and 0 <y1≤1이고, 2≤z≤4이고, 1≤w≤3 일 수 있다.

[0020] Additionally, the above chemical formula 1 can be expressed as the following chemical formula 3.

[0021] [Chemical Formula 3]

[0022] Li 6.25 Ga 0.25 La3Zr2O 12

[0023] Additionally, the solid electrolyte may include a cubic structure.

[0024] According to another aspect of the present invention, a solid electrolyte sheet comprising a solid electrolyte and a binder is provided, wherein the solid electrolyte comprises lithium lanthanum zirconium oxide (LLZO) doped or undoped with a heterometal represented by the following chemical formula 4, and the heterometal comprises at least one selected from the group consisting of aluminum and gallium.

[0025] [Chemical Formula 4]

[0026] Li x Ga y1 Al y2 La z Zr w O 12

[0027] In chemical formula 4, 5≤x≤9, 0≤y1≤4, 0≤y2≤4, 2≤z≤4, and 1≤w≤3.

[0028] In addition, the binder may include at least one selected from the group consisting of polyethyleneoxide, polyethyleneglycol, polyacrylonitrile, polyvinylchloride, polymethylmethacrylate, polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone.

[0029] According to another aspect of the present invention, a method for producing a solid electrolyte is provided, comprising: (a) preparing a precursor mixture solution including a lithium (Li) precursor, a lanthanum (La) precursor, a zirconium (Zr) precursor, and a solvent; (b) preparing a solid electrolyte precursor by co-precipitating the precursor mixture solution through high-frequency focused homogenization; and (c) heat-treating the solid electrolyte precursor to produce a solid electrolyte represented by the following chemical formula 1'.

[0030] [Chemical Formula 1']

[0031] Li x La z Zr w O 12

[0032] In chemical formula 1', 5≤x≤9, 2≤z≤4, and 1≤w≤3.

[0033] In addition, the precursor mixture solution further includes a heterometal precursor, and the heterometal precursor includes at least one selected from the group consisting of a gallium precursor and an aluminum precursor, and the solid electrolyte can be expressed by the following chemical formula 1''.

[0034] [Chemical Formula 1'']

[0035] Li x Ga y1 Al y2 La z Zr w O 12

[0036] In chemical formula 1, 5≤x≤9, 0≤y1≤4, 0≤y2≤4, y1+y2≠0, 2≤z≤4, and 1≤w≤3.

[0037] In addition, the method for manufacturing the solid electrolyte may additionally include, after step (b), a step (b') of drying the solid electrolyte precursor.

[0038] Additionally, the solvent may include at least one selected from the group consisting of ethanol, dimethylformamide, and acetic acid.

[0039] Additionally, in step (a), the mole number (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) can be 1 to 40.

[0040] Additionally, in step (a), the mole number (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) can be 10 to 15 days.

[0041] Additionally, the solvent may include ethanol.

[0042] Additionally, the lithium (Li) precursor may include lithium nitrate, the lanthanum (La) precursor may include lanthanum nitrate, the zirconium (Zr) precursor may include zirconium n-propoxide, the gallium (Ga) precursor may include gallium nitrate, and the aluminum (Al) precursor may include aluminum nitrate.

[0043] Additionally, the high-frequency focused homogenization of step (b) can be performed at a power of 0.5 to 5 kwatts.

[0044] Additionally, the high-frequency focused homogenization of step (b) can be performed for 1 to 15 hours.

[0045] Additionally, the high-frequency focused homogenization of step (b) can be performed at a wavelength of 20 to 2000 kHz.

[0046] Additionally, the heat treatment in step (c) may be performed for 0.5 to 10 hours.

[0047] Additionally, the heat treatment in step (c) can be performed at 600 to 1000°C.

[0048] Additionally, the total precursor concentration of the precursor mixture solution may be 10 to 35 wt%.

[0049] The present invention has the effect of enabling simple and accurate control of the stoichiometric ratio by using a precursor mixture solution and performing heat treatment at a low temperature, compared to a co-precipitation method in which lithium precursors are individually injected, heat treated at a high temperature, and synthesized in a small amount over a long period of time, and capable of producing LLZO doped or undoped with a large amount of heterometal.

[0050] In addition, the LLZO of the present invention has the effect of enabling the simple production of LLZO doped or undoped with a different metal by using a precursor mixture solution containing all of the precursors, namely, a zirconium precursor (Zirconium n-propxide), a gallium precursor (Gallium nitrate), a lithium precursor (Lithium nitrate), and a lanthanum precursor (Lanthanum nitrate), in a solvent, thereby proceeding without an additional process of supplying an additional additive, for example, a lithium source, in a subsequent process after preparing the solution.

[0051] In addition, by controlling the high-frequency focused homogenization time, the amount of doped heterometal, the amount of solvent, the heat treatment time, and the heat treatment temperature, it is possible to remove impurities, control the cubic structure, and manufacture a garnet-type oxide-based Ga-LLZO solid electrolyte having high ionic conductivity.

[0052] These drawings are for reference in explaining exemplary embodiments of the present invention, and therefore, the technical idea of ​​the present invention should not be interpreted as being limited to the attached drawings.

[0053] Figure 1 is a schematic diagram for manufacturing a Ga-LLZO solid electrolyte according to an embodiment of the present invention.

[0054] Figure 2 is a schematic diagram showing a manufacturing process of Ga-LLZO solid electrolyte powder according to an embodiment of the present invention.

[0055] FIG. 3 is a graph and an image of an analysis device showing data analyzing the particle size of a Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention.

[0056] FIG. 4 is a scanning electron microscope (SEM) image of particles of Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention.

[0057] FIG. 5 is an XRD graph showing the structure of a Ga-LLZO solid electrolyte powder according to Example 1 of the present invention.

[0058] Fig. 6 is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to heat treatment time according to Example 2 of the present invention.

[0059] FIG. 7 is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to the amount of acetic acid, which is a dissolution solution of a Zr precursor according to Example 3 of the present invention.

[0060] FIG. 8a is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention, and FIG. 8b is a graph showing the size of Ga-LLZO solid electrolyte powder according to Examples 4 and 5 of the present invention.

[0061] FIG. 9a is a graph showing the structure of Ga-LLZO solid electrolyte powder according to the heat treatment temperature according to Example 6 of the present invention, and FIG. 9b is a graph showing the measured impedance of Ga-LLZO solid electrolyte pellet according to the heat treatment temperature according to Example 6 of the present invention.

[0062] FIG. 10a is a graph showing the structure of powder in a Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-1 to 7-3 of the present invention, FIG. 10b is a graph showing the structure of powder in a Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-4 to 7-6 of the present invention, and FIG. 10c is a graph showing the structure of powder in a Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-7 to 7-9 of the present invention.

[0063] FIG. 11 is a graph showing the impedance of a Ga-LLZO solid electrolyte measured according to the pressure applied to the Ga-LLZO solid electrolyte pellet according to Example 8 of the present invention.

[0064] FIG. 12a is a graph showing the impedance of a Ga-LLZO solid electrolyte pellet measured according to a high-frequency focused homogenization time according to Example 9 of the present invention, and FIG. 12b is a graph showing the impedance of a Ga-LLZO solid electrolyte pellet measured according to a high-frequency focused homogenization time according to Example 9 of the present invention at a specific section.

[0065] FIG. 13a is a graph showing the ionic conductivity of a sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 10-1 and 10-2 of the present invention, and FIG. 13b is a graph showing the impedance measured and the sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 10-1 and 1-2 of the present invention.

[0066] FIG. 14a is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Examples 11-1 to 11-6 of the present invention, FIG. 14b is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-1 of the present invention, FIG. 14c is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-4 of the present invention, and FIG. 14d is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-6 of the present invention.

[0067] Figure 15 is an image of particles according to changes in the content of acetic acid according to Examples 11-1 to 11-6 of the present invention.

[0068] FIG. 16 is a graph showing the ionic conductivity of a sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 12-1 to 12-6 of the present invention.

[0069] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

[0070] However, the following description is not intended to limit the present invention to a specific embodiment, and when explaining the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description is omitted.

[0071] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but should be understood to not preclude the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0072] Additionally, terms including ordinal numbers, such as "first," "second," etc., which will be used hereinafter, may be used to describe various components, but these components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a second component, and similarly, a second component could also be referred to as a first component.

[0073] Additionally, when it is said that a component is "formed on" or "laminated on" another component, it should be understood that it may be formed or laminated directly on the entire surface or one side of the other component, but there may also be other components present in between.

[0074] Hereinafter, a lithium lanthanum zirconium oxide solid electrolyte manufactured using a high-frequency focused homogenization synthesis method and a manufacturing method thereof will be described in detail. However, this is provided as an example and the present invention is not limited thereto, and the present invention is defined only by the scope of the claims set forth below.

[0075] According to one aspect of the present invention, a solid electrolyte is provided, which is a solid electrolyte comprising lithium lanthanum zirconium oxide (LLZO) doped or undoped with a heterometal represented by the following chemical formula 1, wherein the heterometal comprises at least one selected from the group consisting of aluminum and gallium.

[0076] [Chemical Formula 1]

[0077] Li x Ga y1 Al y2 La z Zr w O 12

[0078] In chemical formula 1, 5≤x≤9, 0≤y1≤1, 0≤y2≤1, 2≤z≤4, and 1≤w≤3.

[0079] In addition, the solid electrolyte may be in powder form, and the size of the powder may be 1 to 20 nm, preferably 1 to 5 nm. Here, if the size of the powder is less than 1 nm, it is difficult to control the dispersion of the nanopowder, which is not preferable, and if it exceeds 20 nm, the density decreases and the filling ratio decreases, which may lower the efficiency of the battery, which is not preferable.

[0080] In addition, the size of the powder may be a full width at half maximum of 0.5 to 10 nm, preferably 0.5 to 5 nm. Here, if the full width at half maximum exceeds 5 nm, the uniformity of the particles is low, making dispersion difficult, which is not preferable.

[0081] Additionally, the size distribution of the powder may be a single-rod distribution.

[0082] In addition, the above chemical formula 1 can be expressed by the following chemical formula 2.

[0083] [Chemical Formula 2]

[0084] Li x Ga y1 La z Zr w O 12

[0085] In chemical formula 2, 5≤x≤9, and 0 <y1≤1이고, 2≤z≤4이고, 1≤w≤3 일 수 있다.

[0086] Additionally, the above chemical formula 1 can be expressed as the following chemical formula 3.

[0087] [Chemical Formula 3]

[0088] Li 6.25 Ga 0.25 La3Zr2O 12 It could be.

[0089] Additionally, the solid electrolyte may include a cubic structure.

[0090] According to another aspect of the present invention, a solid electrolyte sheet comprising a solid electrolyte and a binder is provided, wherein the solid electrolyte comprises lithium lanthanum zirconium oxide (LLZO) doped or undoped with a heterometal represented by the following chemical formula 4, and the heterometal comprises at least one selected from the group consisting of aluminum and gallium.

[0091] [Chemical Formula 4]

[0092] Li x Ga y1 Al y2 La z Zr w O 12

[0093] In chemical formula 4, 5≤x≤9, 0≤y1≤4, 0≤y2≤4, 2≤z≤4, and 1≤w≤3.

[0094] In addition, the binder may include at least one selected from the group consisting of polyethyleneoxide, polyethyleneglycol, polyacrylonitrile, polyvinylchloride, polymethylmethacrylate, polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone.

[0095] According to another aspect of the present invention, a method for producing a solid electrolyte is provided, comprising: (a) preparing a precursor mixture solution including a lithium (Li) precursor, a lanthanum (La) precursor, a zirconium (Zr) precursor, and a solvent; (b) preparing a solid electrolyte precursor by co-precipitating the precursor mixture solution through high-frequency focused homogenization; and (c) heat-treating the solid electrolyte precursor to produce a solid electrolyte represented by the following chemical formula 1'.

[0096] [Chemical Formula 1']

[0097] Li x La z Zr w O 12

[0098] In chemical formula 1', 5≤x≤9, 2≤z≤4, and 1≤w≤3.

[0099] In addition, the precursor mixture solution further includes a heterometal precursor, and the heterometal precursor includes at least one selected from the group consisting of a gallium precursor and an aluminum precursor, and the solid electrolyte can be expressed by the following chemical formula 1''.

[0100] [Chemical Formula 1'']

[0101] Li x Ga y1 Al y2 La z Zr w O 12

[0102] In chemical formula 1, 5≤x≤9, 0≤y1≤4, 0≤y2≤4, y1+y2≠0, 2≤z≤4, and 1≤w≤3.

[0103] In addition, the method for manufacturing the solid electrolyte may additionally include, after step (b), a step (b') of drying the solid electrolyte precursor.

[0104] Additionally, the solvent may include at least one selected from the group consisting of ethanol, dimethylformamide, and acetic acid.

[0105] Additionally, in step (a), the mole number (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) may be 1 to 40, preferably 5 to 25, and more preferably 10 to 15. Here, if the ratio of the mole number (mA) of acetic acid to the mole number (mL) of the lanthanum precursor (mA / mL) is less than 1, nanoparticles are not formed well and impurities such as LaZrO are formed, which is undesirable. If it exceeds 40, nanoparticles are formed in a tetragonal system due to the non-homogeneous formation of nanoparticles caused by rapid volatilization of the solvent during synthesis, which is undesirable.

[0106] Additionally, in step (a), the mole number (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) can be 10 to 15.

[0107] Additionally, the solvent may include ethanol.

[0108] In addition, the precursor mixture solution may additionally include an organic acid, and the weight ratio of the zirconium precursor:organic acid of the precursor mixture solution may be 1:0.5 to 1:1.2. Here, if the weight ratio of the precursor:organic acid is less than 1:0.5, not only LaO but also many impurities are present, which is undesirable, and if it exceeds 1:1.2, the amount of LaO increases, which is undesirable.

[0109] In addition, the organic acid may include at least one selected from the group consisting of acetic acid, propionic acid, lactic acid, citric acid, succinic acid, oxalic acid, fumaric acid, ascorbic acid, maleic acid, tartaric acid, butanoic acid, and stearic acid.

[0110] Additionally, the lithium (Li) precursor may include lithium nitrate, the lanthanum (La) precursor may include lanthanum nitrate, the zirconium (Zr) precursor may include zirconium n-propoxide, the gallium (Ga) precursor may include gallium nitrate, and the aluminum (Al) precursor may include aluminum nitrate.

[0111] In addition, the high-frequency focused homogenization of step (b) can be performed at a power of 0.5 to 5 kW. Here, if the power of the high-frequency focused homogenization is performed at less than 0.5 kW, the energy required for particle formation is insufficient, which is not preferable, and if it is performed at more than 5 kW, the solvent easily and quickly volatilizes due to the temperature rise caused by excessive energy, which is not preferable, making it difficult to perform the high-frequency focused homogenization.

[0112] In addition, the high-frequency focused homogenization of step (b) can be performed for 1 to 15 hours. Here, if the high-frequency focused homogenization time is less than 1 hour, Ga-LLZO particles are not formed, which is undesirable, and if it exceeds 15 hours, particles are formed, but it is economically undesirable in terms of particle size increase and production process.

[0113] In addition, the high-frequency focused homogenization of step (b) may be performed at a wavelength of 20 to 2000 kHz. Here, if the high-frequency focused homogenization is performed at a wavelength of less than 20 kHz, the high-frequency focused homogenization is not formed, and the precursor is not formed at the high temperature, high pressure, and jet flow required for synthesis, which is undesirable. If the high-frequency focused homogenization is performed at a wavelength exceeding 2000 kHz, particle formation is hindered due to excessive energy, and the precursor is consumed due to deterioration, and other impurities are also generated, which is undesirable.

[0114] In addition, the heat treatment of step (c) can be performed for 0.5 to 10 hours. Before the heat treatment, the impurity LaZrO is the majority, and other precursors are present. Here, if the heat treatment is less than 0.5 hours, homogeneous Ga-LLZO is partially formed, and the impurity LaZrO is still present, which is undesirable. If it exceeds 10 hours, the structure of Ga-LLZO is not formed as a cubic structure due to the volatilization of Li, which is undesirable.

[0115] In addition, the heat treatment in step (c) may be performed at 600 to 1000°C. Here, if the heat treatment is performed at less than 600°C, the crystallinity of Ga-LLZO deteriorates and uncrystallized precursors still remain, which is undesirable. If the heat treatment is performed at more than 1000°C, Ga-LLZO having a tetragonal structure is synthesized, resulting in a composite having a mixed cubic and tetragonal structure, which is undesirable.

[0116] In addition, the total precursor concentration of the precursor mixture solution may be 10 to 35 wt%. Here, if the total precursor concentration is less than 10 wt%, it is not preferable because unnecessary solvent is used and a lot of time is required for drying. If it exceeds 35 wt%, it exceeds the saturated solubility, so impurities are generated because not all of the precursor is dissolved in the solvent, and high-frequency focused homogenization becomes difficult due to an increase in viscosity, which is not preferable.

[0117] [Example]

[0118] Hereinafter, preferred embodiments of the present invention will be described. However, these are provided for illustrative purposes only and the scope of the present invention is not limited thereby.

[0119] Example 1: Change in heat treatment temperature

[0120] Example 1-1: 900 ℃

[0121] Fig. 1 is a schematic diagram for manufacturing a Ga-LLZO solid electrolyte according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing a process for manufacturing a Ga-LLZO solid electrolyte according to an embodiment of the present invention, and Table 1 below is a table showing the time and power of performing high-frequency focused homogenization and the time and temperature of performing heat treatment according to Examples 1-1 to 1-5 of the present invention. Referring to Fig. 1, Fig. 2 and Table 1, the Ga to be manufactured is added to a solvent containing 200 g of ethanol and 40 g of DMF. 0.25 Li 6.25 La3Zr2O 12 According to the composition ratio of the solid electrolyte, 14.5 g of lithium nitrate (LiNO3), 32.2 g of lanthanum nitrate (La(NO3)3), and 32.2 g of zirconium n-propoxide solution (C 12 H 32A precursor mixture solution was prepared by adding 31 g of O4Zr, 2 g of gallium nitrate (Ga(NO3)3), and 30 g of acetic acid. A solid electrolyte precursor mixture solution was prepared by co-precipitating the precursor mixture solution through high-frequency focused homogenization at 2.5 kW power for 240 minutes, and the solid electrolyte precursor mixture solution was dried to prepare a solid electrolyte precursor. The solid electrolyte precursor was heat-treated at 900°C for 360 minutes to form Ga 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0122] Example 1-2: 850 ℃

[0123] Ga was prepared in the same manner as in Example 1-1, except that the heat treatment was performed at 850°C instead of 900°C. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0124] Example 1-3: 800 ℃

[0125] Ga was prepared in the same manner as in Example 1-1, except that the heat treatment was performed at 800°C instead of 900°C. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0126] Example 1-4: 750 ℃

[0127] Ga was prepared in the same manner as in Example 1-1, except that the heat treatment was performed at 750°C instead of 900°C. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0128] Example 1-5: 700 ℃

[0129] Ga was prepared in the same manner as in Example 1-1, except that the heat treatment was performed at 700°C instead of 900°C. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0130] [Table 1]

[0131]

[0132] Example 2: Changes in heat treatment time

[0133] Examples 2-1 to 2-7

[0134] Table 2 below shows the power and execution time of high-frequency focused homogenization and the temperature and execution time of heat treatment according to Examples 2-1 to 2-7 of the present invention. Referring to Table 2 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that the heat treatment was performed at 750°C instead of 700 to 900°C, and the heat treatment was performed for 5 to 360 minutes instead of 360 minutes. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0135] [Table 2]

[0136]

[0137] Example 3: Change in acetic acid amount (compared to Zr precursor)

[0138] Examples 3-1 to 3-4

[0139] Table 3 below shows the change in the amount of acetic acid, the power and execution time of high-frequency focused homogenization, and the temperature and execution time of heat treatment according to Examples 3-1 to 3-4 of the present invention. Referring to Table 3 below, the heat treatment is performed at 750°C instead of 700 to 900°C, the high-frequency focused homogenization power is performed at 1.2 kwatt instead of 2.5 kwatt, and the amount of acetic acid in each of Examples 3-1 to 3-4 is changed, except that Ga-doped Ga is prepared in the same manner as Example 1-1. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0140] [Table 3]

[0141]

[0142] Example 4: 1.2 kW RF focused homogenization time variation

[0143] Examples 4-1 to 4-6

[0144] Table 4 below shows the power and execution time of high-frequency focused homogenization and the temperature and execution time of heat treatment according to Examples 4-1 to 4-6 of the present invention. Referring to Table 4 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that the heat treatment was performed at 750°C instead of 700 to 900°C, the high-frequency focused homogenization power was performed at 1.2 kwatt instead of 2.5 kwatt, and the high-frequency focused homogenization was performed for 120 to 720 minutes instead of 240 minutes. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0145] [Table 4]

[0146]

[0147] Example 5: 2.5 kW RF focused homogenization time variation

[0148] Examples 5-1 to 5-6

[0149] Table 5 below shows the power and execution time of high-frequency focused homogenization and the temperature and execution time of heat treatment according to Examples 5-1 to 5-6 of the present invention. Referring to Table 5 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that the heat treatment was performed at 750°C instead of 700 to 900°C, and the high-frequency focused homogenization was performed for 120 to 720 minutes instead of 240 minutes. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0150] [Table 5]

[0151]

[0152] Example 6: Changes in ionic conductivity of Ga-LLZO solid electrolyte pellets depending on heat treatment temperature.

[0153] Examples 6-1 to 6-3

[0154] Table 6 below is a table showing the change in ionic conductivity of Ga-LLZO solid electrolyte pellets according to the change in heat treatment temperature of Examples 6-1 to 6-3 of the present invention. Referring to Table 6 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that the heat treatment of Examples 6-1 to 6-3 was performed at 750 to 950°C instead of 700 to 900°C. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was prepared. Since it is difficult to measure ionic conductivity in the powder state, the above Ga 0.25 Li 6.25 La3Zr2O 12The solid electrolyte powder was manufactured in pellet form and the ionic conductivity according to the change in heat treatment temperature was measured. The Ga in the 13Φ mold 0.25 Li 6.25 La3Zr2O 12 After filling the solid electrolyte powder, use the S1-200 press equipment to hold it at a load of 5000 kg for 3 minutes to form Ga 0.25 Li 6.25 La3Zr2O 12 Solid electrolyte pellets were manufactured. The ionic conductivity was then measured using an SP-200 analyzer.

[0155] [Table 6]

[0156]

[0157] Example 7: Changes according to the amount of Ga and heat treatment temperature

[0158] Examples 7-1 to 7-9

[0159] Table 7 below shows the change in the amount of gallium (Ga), the power and execution time of high-frequency focused homogenization, and the temperature and execution time of heat treatment according to Examples 7-1 to 7-9 of the present invention. Referring to Table 7 below, the heat treatment is performed at 750 to 850°C instead of 700 to 900°C, the high-frequency focused homogenization power is performed at 1.2 kwatt instead of 2.5 kwatt, and the amount of Ga in each of Examples 7-1 to 7-9 is changed, except that Ga is doped in the same manner as Example 1-1. x Li 6.25 La3Zr2O 12 (0.15≤x≤0.5) Solid electrolyte powder was manufactured.

[0160] [Table 7]

[0161]

[0162] Example 8: Changes in press pressure during pellet production

[0163] Examples 8-1 to 8-4

[0164] Table 8 below shows the power and execution time of high-frequency focused homogenization, the temperature and execution time of heat treatment, and the ionic conductivity according to Examples 8-1 to 8-4 of the present invention. Referring to Table 8 below, Examples 8-1 to 8-4 were prepared by doping Ga with Ga in the same manner as Example 7-2. 0.25 Li7La3Zr2O 12 Solid electrolyte powder was prepared. After that, Ga 0.25 Li7La3Zr2O 12 When manufacturing pellets using solid electrolyte powder, S1-200 press equipment is used, and the press pressure is maintained for 3 minutes each, and then sintered at 1000 ℃ to form Ga. 0.25 Li7La3Zr2O 12 Solid electrolyte pellets were manufactured, and ionic conductivity was measured using an SP-200 analysis device.

[0165] [Table 8]

[0166]

[0167] Example 9: Changes in ionic conductivity according to high-frequency focused homogenization time

[0168] Examples 9-1 to 9-7

[0169] Table 9 below shows the power and execution time of high-frequency focused homogenization, the temperature and execution time of heat treatment, and the ionic conductivity according to Examples 9-1 to 9-7 of the present invention. Referring to Table 9 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that high-frequency focused homogenization was performed for 60 to 720 minutes instead of 240 minutes, and the heat treatment was performed at 750°C instead of 700 to 900°C. 0.25 Li 6.25 La3Zr2O 12 Solid electrolyte powder was prepared. After that, Ga0.25 Li 6.25 La3Zr2O 12 When manufacturing pellets using solid electrolyte powder, S1-200 press equipment was used to maintain a load of 5000 kg for 3 minutes and then sintered at 1000 ℃ to form Ga. 0.25 Li 6.25 La3Zr2O 12 Solid electrolyte pellets were manufactured, and ionic conductivity was measured using an SP-200 analysis device.

[0170] [Table 9]

[0171]

[0172] Example 10: Changes in ionic conductivity according to changes in measurement temperature during the manufacture of Ga-LLZO / PEO mixed sheets.

[0173] Examples 10-1 and 10-2

[0174] Table 10 below shows the power and execution time of high-frequency focused homogenization, the temperature and execution time of heat treatment, and the ionic conductivity according to Examples 10-1 to 10-2 of the present invention. Referring to Table 10 below, Example 10-1 was prepared using the same method as Example 1-4. 0.25 Li 6.25 La3Zr2O 12 Solid electrolyte powder was manufactured, and Example 10-2 was prepared using the same method as Comparative Example 1-1. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was prepared. A solid electrolyte sheet was prepared by mixing the solid electrolyte powder according to Examples 10-1 and 10-2 and PEO at a weight ratio of 60:40, and the ionic conductivity according to the change in measurement temperature was measured using an SP-200 analysis device.

[0175] [Table 10]

[0176]

[0177] Example 11: Changes in the amount of acetic acid (compared to La precursor)

[0178] Examples 11-1 to 11-6

[0179] Table 11 below shows the change in the content of acetic acid, the power and execution time of high-frequency focused homogenization, and the temperature and execution time of heat treatment according to Examples 11-1 to 11-6 of the present invention. Referring to Table 11 below, Ga-doped Ga was prepared in the same manner as Example 1-1, except that the heat treatment was performed at 750°C instead of 900°C, and the amount of acetic acid in Examples 11-1 to 11-6 was changed. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte powder was manufactured.

[0180] [Table 11]

[0181]

[0182] Example 12: Changes in ionic conductivity according to changes in the amount of acetic acid in the preparation of Ga-LLZO / PEO mixed sheets.

[0183] Examples 12-1 to 12-6

[0184] Table 12 below is a table showing the thickness and area of ​​the sheet, the power and execution time of high-frequency focused homogenization, and the temperature and execution time of heat treatment according to Examples 12-1 to 12-6 of the present invention. Referring to Table 12 below, Ga manufactured in Examples 11-1 to 11-6 0.25 Li 6.25 La3Zr2O 12 Solid electrolyte sheets of Examples 12-1 to 12-6 were manufactured by mixing solid electrolyte powder and PEO in a weight ratio of 60:40, and the ionic conductivity at 70°C was measured using SP-200 analysis equipment.

[0185] [Table 12]

[0186]

[0187] Comparative Example 1: Preparation of Ga-LLZO solid electrolyte by co-precipitation method

[0188] Comparative Example 1-1: Co-precipitation method

[0189] Starting material solutions were prepared by dissolving lanthanum nitrate (La(NO3)3·xH2O), zirconium nitrate (ZrO(NO3)2·xH2O), and gallium nitrate (Ga(NO3)3·xH2O) in distilled water so that the molar ratio of their metal elements, La:Zr:Ga, was 3:2:0.25.

[0190] The above starting material solution, 0.6 mol of ammonia water as a complexing agent, and an appropriate amount of sodium hydroxide aqueous solution were added to make a mixed solution with a pH adjusted to 11, and the reaction temperature was 25°C, the reaction time was 24 hr, and the mixture was co-precipitated while stirring to obtain a precursor slurry in the form of a liquid slurry.

[0191] The precursor slurry was washed with purified water and dried for 24 hours. The dried precursor was pulverized with a ball mill, and the LiOH·H2O content of the mixture was added so that the content of Li in LiOH·H2O was 110 parts by weight (10 wt% excess) based on 100 parts by weight of Li in the solid electrolyte produced. The mixture was calcined at 900°C for 2 hours and then pulverized to obtain gallium-doped Ga. 0.25 Li 6.25 La3Zr2O 12 A solid electrolyte was manufactured.

[0192] [Example Exam]

[0193] Test Example 1: Particle Size Analysis: Powder Size Analysis

[0194] FIG. 3 is a graph and an image of an analysis device showing data analyzing the particle size of a Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention, FIG. 4 is a scanning electron microscope (SEM) image of particles of a Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention, FIG. 8a is an XRD graph showing the structure of a Ga-LLZO solid electrolyte powder according to Example 4-2 of the present invention, and FIG. 8b is a graph showing the size of a Ga-LLZO solid electrolyte powder according to Examples 4 and 5 of the present invention. Referring to FIGS. 3, 4, 8a, and 8b, it can be confirmed that the particle size of the Ga-LLZO solid electrolyte powder is 0.5 to 14 nm.

[0195] FIG. 14a is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Examples 11-1 to 11-6 of the present invention, FIG. 14b is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-1 of the present invention, FIG. 14c is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-4 of the present invention, and FIG. 14d is a graph showing data analyzing the particle size of Ga-LLZO solid electrolyte powders according to Example 11-6 of the present invention.

[0196] Referring to FIGS. 14a to 14d and FIG. 15, it can be confirmed that the improvement in ionic conductivity according to particle uniformity as well as particle size is achieved by maintaining constant connections between particles, forming a smoother and more continuous path for ions to move, thereby ensuring path consistency and minimizing resistance occurring at particle boundaries. In addition, it can be confirmed that particle uniformity contributes to increasing ionic conductivity by reducing the formation of pores between particles, thereby reducing factors that cause ion movement paths to be obstructed or broken.

[0197] Test Example 2: XRD Structural Analysis

[0198] FIG. 5 is an XRD graph showing the structure of a Ga-LLZO solid electrolyte powder according to Example 1 of the present invention, and FIG. 6 is an XRD graph showing the structure of a Ga-LLZO solid electrolyte powder according to a heat treatment time according to Example 2 of the present invention.

[0199] Referring to Fig. 5, a test was conducted to confirm the structural change of the Ga-LLZO solid electrolyte according to the heat treatment temperature. The heat treatment was performed at a temperature of 700 to 900 ℃, and the Ga-LLZO solid electrolyte that was heat treated at a temperature of 750 ℃ ​​according to Example 1-4 was 0.25 Li7La3Zr2O 12 It was confirmed that the solid electrolyte exhibited the best cubic structure Ga-LLZO phase.

[0200] Referring to Fig. 6, the heat treatment temperature was set to 750 ℃ ​​in accordance with Fig. 5, and a test was conducted to confirm the structural change of the Ga-LLZO solid electrolyte according to the heat treatment time. The heat treatment was performed for 5 to 360 minutes, and the Ga-LLZO solid electrolyte that was heat treated for 240 minutes according to Example 2-6 0.25 Li7La3Zr2O 12 It was confirmed that the solid electrolyte exhibited the best cubic structure Ga-LLZO phase.

[0201] Test Example 3: XRD Structural Analysis

[0202] Fig. 7 is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to the amount of acetic acid, which is a dissolution solution of a Zr precursor according to Example 3 of the present invention. Referring to Fig. 7, a test was performed to confirm the appropriate amount by changing the amount of acetic acid, which is a dissolution solvent of the Zr precursor. This is a graph showing the structure of Ga-LLZO solid electrolyte powder according to Example 3, and it was confirmed that the best cubic structure Ga-LLZO phase was exhibited when the weight ratio of the Zr precursor and acetic acid according to Example 3-3 was 1:1.

[0203] Test Example 4: XRD Structural Analysis

[0204] Fig. 10a is a graph showing the structure of powder in Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-1 to 7-3 of the present invention, Fig. 10b is a graph showing the structure of powder in Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-4 to 7-6 of the present invention, and Fig. 10c is a graph showing the structure of powder in Ga-LLZO solid electrolyte according to the Ga doping amount and heat treatment temperature according to Examples 7-7 to 7-9 of the present invention. Referring to Figs. 10a to 10c, in order to confirm the change according to the Ga doping content and the structural change according to the heat treatment temperature, the Ga doping content was manufactured to be 0.15 to 0.5 compared to the stoichiometric ratio, and heat treatment was performed at a temperature of 750 to 850°C. Ga according to Example 7-2 0.25 Li7La3Zr2O 12 It was confirmed that the solid electrolyte powder exhibited the best cubic structure Ga-LLZO phase.

[0205] Test Example 5: Ionic Conductivity Analysis of Solid Electrolyte Pellets

[0206] FIG. 9a is a graph showing the structure of Ga-LLZO solid electrolyte powder according to the heat treatment temperature according to Example 6 of the present invention, FIG. 9b is a graph showing the impedance of Ga-LLZO solid electrolyte pellets according to the heat treatment temperature according to Example 6 of the present invention, FIG. 11 is a graph showing the impedance of Ga-LLZO solid electrolyte according to the pressure applied to Ga-LLZO solid electrolyte pellets according to Example 8 of the present invention, FIG. 12a is a graph showing the impedance of Ga-LLZO solid electrolyte pellets according to the high-frequency focused homogenization time according to Example 9 of the present invention, and FIG. 12b is a graph showing the impedance of Ga-LLZO solid electrolyte pellets according to the high-frequency focused homogenization time according to Example 9 of the present invention, measured at a specific section. In addition, Table 13 below is a table showing the ionic conductivity and Rb of the Ga-LLZO solid electrolyte pellet according to Example 6 of the present invention, Table 14 below is a table showing the ionic conductivity, diameter, thickness and Rb of the Ga-LLZO solid electrolyte pellet according to Example 8 of the present invention, and Table 13 below is a table showing the ionic conductivity, diameter, area, thickness and Rb of the Ga-LLZO solid electrolyte pellet according to Example 8 of the present invention.

[0207] We conducted a test to determine the manufacturing conditions for Ga-LLZO solid electrolyte pellets with high ionic conductivity. Because measuring ionic conductivity in powder form of the solid electrolyte is difficult, it was manufactured in pellet form and then measured.

[0208] Referring to FIG. 9a, FIG. 9b and Table 13, it was confirmed that the ionic conductivity of the Ga-LLZO solid electrolyte pellet heat-treated at 750°C according to Example 6-1 was 1.08E-04 S / cm, which was the highest value among the ionic conductivities of the Ga-LLZO solid electrolyte pellets according to Examples 6-1 to 6-3.

[0209] Referring to Fig. 11 and Table 14, Ga-LLZO solid electrolyte pellets were manufactured with a press pressure of 900 to 6000 kg according to the press equipment, and it was confirmed that the higher the pressure, the higher the ionic conductivity.

[0210] Referring to FIGS. 12a, 12b, and Table 15, Ga-LLZO solid electrolyte powder and pellets were manufactured by performing high-frequency focused homogenization for 60 to 600 minutes. The ionic conductivity of the Ga-LLZO solid electrolyte pellets subjected to high-frequency focused homogenization for 240 minutes according to Example 9-3 was 6.29E-05 S / cm, which was the highest value among the ionic conductivities of the Ga-LLZO solid electrolyte pellets subjected to high-frequency focused homogenization for 60 to 720 minutes according to Examples 9-1 to 9-7.

[0211] [Table 13]

[0212]

[0213] [Table 14]

[0214]

[0215] [Table 15]

[0216]

[0217] Test Example 6: Analysis of ionic conductivity of solid electrolyte sheets

[0218] FIG. 13a is a graph showing the ionic conductivity of a sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 10-1 and 10-2 of the present invention, and FIG. 13b is a graph showing the impedance of a sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 10-1 and 1-2 of the present invention. In addition, Table 16 below is a table showing the ionic conductivity, thickness, and area of ​​the Ga-LLZO solid electrolyte pellet according to Example 10 of the present invention. Referring to FIG. 13 and Table 16, the frequency range was 7 MHz to 100 nHz, the amplitude was 10 mV, the ionic conductivity measurement temperature range was 25 to 70°C, and aging was performed for 1 hour for each ionic conductivity measurement section. Based on the ionic conductivity measurement temperature of 70 ℃, it was confirmed that the Ga-LLZO sheet (7.48E-04 S / cm) manufactured by high-frequency focused homogenization according to Example 10-1 had a higher ionic conductivity than the Ga-LLZO sheet (3.49E-04 S / cm) manufactured by the co-precipitation method according to Example 10-2.

[0219] [Table 16]

[0220]

[0221] Test Example 7: Comparison of Solid Electrolyte Particle Sizes

[0222] FIG. 12 is a graph showing the ionic conductivity of Ga-LLZO solid electrolyte pellets according to the high-frequency focused homogenization time according to Example 9 of the present invention. Referring to FIG. 12, a test was conducted to confirm the particle size of the Ga-LLZO solid electrolyte according to the high-frequency focused homogenization power and time. The particle size of the Ga-LLZO solid electrolyte powder that was subjected to high-frequency focused homogenization for 1 hour according to Example 9-1 was confirmed to be about 1 to 2 nm, and the particle size of the Ga-LLZO solid electrolyte powder that was subjected to high-frequency focused homogenization for 12 hours according to Example 9-7 was confirmed to be about 6 to 9 nm. Therefore, it was confirmed that the change in particle size according to Example 9 tended to gradually increase according to the high-frequency focused homogenization time.

[0223] Test Example 8: Impurity Analysis

[0224] Fig. 10 is a graph showing the structure of powder in a Ga-LLZO solid electrolyte according to the amount of Ga doping and the heat treatment temperature according to Example 7 of the present invention. Referring to Fig. 10, it was confirmed that impurities including LaZrO were generated due to insufficient and excessive amounts of Ga.

[0225] Test Example 9: Cubic Structure and Impurity Analysis

[0226] Fig. 6 is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to the heat treatment time according to Example 2 of the present invention. Referring to Fig. 6, a test was conducted to confirm the formation of a cubic structure and the removal of impurities in the Ga-LLZO solid electrolyte according to the heat treatment time. In order to control impurities including LaZrO, an experiment was conducted by increasing the heat treatment time, and it was confirmed that when the heat treatment was performed for 2 hours or more, it was effective in controlling impurities including LaZrO, but when it was performed for 6 hours or more, it was difficult to control impurities including LaO.

[0227] Test Example 10: Impurity Analysis

[0228] Fig. 7 is an XRD graph showing the structure of Ga-LLZO solid electrolyte powder according to the amount of acetic acid, which is a dissolution solution of a Zr precursor according to Example 3 of the present invention. Referring to Fig. 7, it was confirmed that the amount of impurities including LaO increased when the amount of acetic acid exceeded or was less than the appropriate amount of Zr precursor:Acetic acid weight ratio of 1:1.

[0229] Test Example 11: Analysis of ionic conductivity of solid electrolyte sheets according to changes in acetic acid content.

[0230] FIG. 16 is a graph showing the ionic conductivity of a sheet mixed with Ga-LLZO solid electrolyte powder and PEO according to Examples 12-1 to 12-6 of the present invention, and Table 17 is a table showing the ionic conductivity of Ga-LLZO solid electrolyte sheets according to Examples 12-1 to 12-6 of the present invention. The experiment was conducted with a frequency range of 7 MHz to 100 nHz, an amplitude of 10 mV, an ionic conductivity measurement temperature of 70 ℃, and aging for 1 hour for each ionic conductivity measurement section. Referring to FIG. 16 and Table 17, it can be confirmed that the improvement in ionic conductivity according to the uniformity of particles as well as the size of particles is that the connection between particles is maintained constant, the path through which ions can move is formed more smoothly and continuously, thereby securing the consistency of the path and minimizing the resistance occurring at the boundary between particles. In addition, it was found that the uniformity of the particles contributed to increasing the ionic conductivity by reducing the formation of gaps between particles and thus reducing factors that hinder or interrupt the ion movement path, and it was confirmed that the Ga-LLZO sheet according to Example 12-4 had the highest ionic conductivity.

[0231] [Table 17]

[0232]

[0233]

[0234] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A solid electrolyte comprising lithium lanthanum zirconium oxide (LLZO) doped or undoped with a heterometal, represented by the following chemical formula 1, A solid electrolyte comprising at least one heterometal selected from the group consisting of aluminum and gallium: [Chemical Formula 1] Li x Ga y1 Al y2 La z Zr w O 12 In chemical formula 1, 5≤x≤9, 0≤y1≤1, 0≤y2≤1, 2≤z≤4, and 1≤w≤3.

2. In paragraph 1, A solid electrolyte characterized in that the solid electrolyte is in a powder form and the size of the powder is 1 to 20 nm.

3. In paragraph 2, A solid electrolyte characterized in that the powder has a full width at half maximum of 0.5 to 10 nm.

4. In paragraph 2, A solid electrolyte characterized in that the size distribution of the powder has a single-rod distribution.

5. In paragraph 1, A solid electrolyte characterized in that the above chemical formula 1 is expressed by the following chemical formula 2: [Chemical Formula 2] Li x Ga y1 The z Zr w About 12 In chemical formula 2, 5≤x≤9, and 0 <y1≤1이고, 2≤z≤4이고, 1≤w≤3이다.

6. In paragraph 1, A solid electrolyte characterized in that the above chemical formula 1 is expressed by the following chemical formula 3: [Chemical Formula 3] Li 6.25 Ga 0.25 La3Zr2O 12 7. In paragraph 1, A solid electrolyte characterized in that the solid electrolyte comprises a cubic structure. 8.(a) A step of preparing a precursor mixture solution including a lithium (Li) precursor, a lanthanum (La) precursor, a zirconium (Zr) precursor, and a solvent; (b) a step of preparing a solid electrolyte precursor by co-precipitating the precursor mixture solution through high-frequency focused homogenization; and (c) a step of heat-treating the solid electrolyte precursor to produce a solid electrolyte represented by the following chemical formula 1'; Method for manufacturing a solid electrolyte comprising: [Chemical Formula 1'] He x The z Zr w Oh 12 In chemical formula 1', 5≤x≤9, 2≤z≤4, and 1≤w≤3.

9. In paragraph 8, The above precursor mixture solution additionally contains a heterometal precursor, A method for producing a solid electrolyte, wherein the heterometal precursor comprises at least one selected from the group consisting of a gallium precursor and an aluminum precursor, and the solid electrolyte is represented by the following chemical formula 1'': [Chemical Formula 1''] Li x Ga y1 Al y2 La z Zr w O 12 In chemical formula 1, 5≤x≤9, 0≤y1≤4, 0≤y2≤4, y1+y2≠0, 2≤z≤4, and 1≤w≤3.

10. In paragraph 8, After the above solid electrolyte manufacturing method step (b), (b') A method for producing a solid electrolyte, characterized in that it further comprises a step of drying the solid electrolyte precursor.

11. In paragraph 8, In step (a), A method for producing a solid electrolyte, characterized in that the solvent comprises at least one selected from the group consisting of ethanol, dimethylformamide, and acetic acid.

12. In paragraph 11, In step (a), the number of moles (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) is 1 to 40.

13. In paragraph 11, In step (a), the number of moles (m) of the lanthanum precursor L ) moles of acetic acid (m A ) of the ratio (m) A / m L ) is 10 to 15.

14. In paragraph 8, In step (a), The above lithium (Li) precursor comprises lithium nitrate, The above lanthanum (La) precursor comprises lanthanum nitrate, The above zirconium (Zr) precursor comprises zirconium n-propoxide, The gallium (Ga) precursor contains gallium nitrate, A method for producing a solid electrolyte, characterized in that the aluminum (Al) precursor contains aluminum nitrate.

15. In paragraph 8, In step (b), A method for producing a solid electrolyte, characterized in that the high-frequency focused homogenization is performed at a power of 0.5 to 5 kwatts.

16. In paragraph 8, In step (b), A method for producing a solid electrolyte, characterized in that the high-frequency focused homogenization is performed at a wavelength of 20 to 2000 kHz.

17. In paragraph 8, In step (c), A method for producing a solid electrolyte, characterized in that the above heat treatment is performed for 0.5 to 10 hours.

18. In paragraph 8, In step (c), A method for producing a solid electrolyte, characterized in that the above heat treatment is performed at 600 to 1000°C.

19. In paragraph 8, In step (a), A method for producing a solid electrolyte, characterized in that the total precursor concentration of the precursor mixture solution is 10 to 35 wt%.

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