Process for producing lithium ion-conducting sulfide-based compounds

Abstract

This specification relates to a method for manufacturing lithium-ion conductive sulfide compounds and lithium secondary batteries including such compounds. More specifically, this specification relates to a method for improving the problem of easy deterioration of sulfide solid electrolyte compounds with a sulfide-germanium sulfide crystal structure during pulverization, thereby obtaining sulfide compounds with excellent electrochemical properties and atmospheric stability.

Description

Technical Field

[0001] This specification relates to a method for manufacturing lithium-ion conductive sulfide compounds and lithium secondary batteries including such compounds. More specifically, this specification relates to a method for improving the problem of easy deterioration of sulfide solid electrolyte compounds with a sulfide-germanium sulfide crystal structure during pulverization, thereby obtaining sulfide compounds with excellent electrochemical properties and atmospheric stability. Background Technology

[0002] Batteries use materials capable of electrochemical reactions at the positive and negative electrodes to store electrical energy. A representative example of such batteries is the lithium-ion secondary battery, which stores electrical energy through the difference in chemical potential during the insertion / extraction of lithium ions at the positive and negative electrodes.

[0003] The lithium secondary battery is prepared by using materials capable of reversible lithium-ion insertion / extraction as positive and negative active materials, and filling the space between the positive and negative electrodes with an organic electrolyte or a polymer electrolyte.

[0004] However, these organic or polymer electrolytes typically use flammable organic solvents. Therefore, when abnormally high temperatures occur due to internal or external factors affecting the lithium secondary battery, there is a possibility of fire or explosion caused by the electrolyte.

[0005] Due to these safety concerns, solid-state batteries, which utilize solid electrolytes, have gained attention as an alternative to liquid batteries. Solid-state batteries offer high stability and are anticipated to be commercialized as a next-generation battery with high energy density.

[0006] Among the solid electrolytes used in lithium-ion batteries, sulfide-based solid electrolytes are currently attracting much attention. Various crystal structures of sulfide-based solid electrolytes are known, including the Argyrodite type.

[0007] However, sulfide-based solid electrolytes with a sulfide-germanium ore-type crystal structure are highly reactive with water and oxygen, requiring stringent manufacturing processes and exhibiting significant deviations in ionic conductivity. Furthermore, due to the characteristics of solid materials, micronization is necessary to maximize the contact area; however, this pulverization process leads to amorphization, impurity formation, and other degradations, resulting in a decrease in ionic conductivity. Summary of the Invention

[0008] Technical issues According to this specification, one objective is to provide a method for manufacturing a lithium-ion conductive sulfide compound that prevents performance degradation caused by the easy deterioration of sulfide compounds with a sulfide-germanium-sulfide crystal structure during pulverization and improves electrochemical performance.

[0009] Furthermore, one object of this specification is to provide a solid electrolyte membrane and a lithium secondary battery using a sulfide-based solid electrolyte compound as defined herein.

[0010] The purpose of this specification is not limited to those stated above. Other purposes and advantages not mentioned herein will be understood through the following description and through the embodiments described herein. Furthermore, it will be readily understood that the purposes and advantages of this invention can be achieved by the means and combinations thereof described in the claims.

[0011] Technical solution According to one aspect of this specification, a method for manufacturing a lithium-ion conductive sulfide compound is provided, comprising: (a) preparing a sulfide compound comprising a crystal phase with an Argyrodite-type crystal structure; and (b) wet pulverizing the sulfide compound to obtain particles with an average particle size of less than 3 μm; wherein the wet pulverization is performed using a solvent with a moisture content of less than 12.0 ppm.

[0012] In one embodiment, the crystal phase of the sulfide-germanium ore-type crystal structure can be represented by the following chemical formula 1: [Chemical Formula 1] Li 7-x PS 6-x X x In the chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0 ≤ x ≤ 2.

[0013] Here, the wet pulverization in step (b) can be performed using at least one selected from the group consisting of a ball mill, pebble mill, rod mill, roller mill, colloid mill, impact mill, jet mill, bead mill, vibratory mill, stirred mill, disc mill, and pulverizing and classifying machine.

[0014] On the other hand, the solvent may be a compound having one or more alkyl groups bonded to a benzene ring.

[0015] Furthermore, the solvent may be a solvent purified by microfiltration and molecular sieve.

[0016] In particular, the solvent may be a solvent that has been purified by a microfilter and then by a molecular sieve.

[0017] On the other hand, the microfilter can be a microfilter with a pore size of 0.1~1μm.

[0018] Here, the proportion of particles with a particle size of less than 1 μm in the particles obtained in step (b) can be 20% by weight or more.

[0019] In one embodiment, step (b) may be further included after step (c) of separating particles with a particle size of less than 1 μm from the particles.

[0020] According to another aspect of this specification, a lithium secondary battery is provided, comprising a lithium-ion conductive sulfide compound manufactured according to the manufacturing method described herein.

[0021] Beneficial effects According to this specification, it is possible to suppress the potential deterioration of sulfide compounds of the sulfide type during pulverization, thereby providing sulfide compounds with superior electrochemical properties.

[0022] In addition to the effects described above, the specific effects of the present invention will be described below while explaining the specific matters for carrying out the invention. Attached Figure Description

[0023] Figure 1 The results of the analysis of the critical current density and electrochemical properties of a sulfide compound according to an example of this specification are presented. Detailed Implementation

[0024] To facilitate understanding of this specification, specific terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used in this specification shall have the meanings commonly understood by one of ordinary skill in the art. Furthermore, unless the context specifically indicates otherwise, the singular form of a term shall also include its plural form, and the plural form of a term shall also be understood to include its singular form.

[0025] Method for manufacturing lithium-ion conductive sulfide compounds A method for manufacturing a lithium-ion conductive sulfide compound according to one aspect of this specification may include: (a) preparing a sulfide compound comprising a crystal phase with an Argyrodite-type crystal structure; and (b) wet pulverizing the sulfide compound to obtain particles with an average particle size of less than 3 μm; wherein the wet pulverization may be performed using a solvent with a moisture content of less than 12.0 ppm.

[0026] Step (a) may be a step of synthesizing a lithium-ion conductive sulfide compound or preparing a compound before pulverization.

[0027] The sulfide compounds are lithium-ion conductive and can have a crystal phase with a sulfide-germanium ore-type crystal structure.

[0028] The argyrogermanium sulfide crystal structure refers to the same structure as argyrogermanium sulfide (Ag8GeS6), a silver-germanium-sulfur mineral. The argyrogermanium sulfide crystal structure can exhibit both orthorhombic (Pna21) and cubic (F-43m) phases, with the cubic phase exhibiting higher lithium-ion conductivity. Typically, the argyrogermanium sulfide crystal structure exhibits a cubic phase with excellent lithium-ion conductivity at high temperatures and an orthorhombic phase at low temperatures.

[0029] For example, Li7PS6 and Li6PS5X (where X is at least one of Cl, Br, and I) are known as lithium-ion conductive solid electrolyte compounds with a sulfogermanium ore-type crystal structure.

[0030] However, the argyrocerite-type crystal structure is sensitive to air and humidity, which can easily lead to performance degradation. Therefore, compounds with the argyrocerite-type crystal structure may also experience performance degradation during the manufacturing process, or are prone to the formation of impurities.

[0031] For example, the sulfide-based compound can be obtained by, but is not limited to, mixing lithium sulfide (Li₂S) powder, phosphorus sulfide (P₂S₅) powder, and lithium halide (Li₂X) powder, and then heating the mixture at 350°C under an inactive atmosphere. Firing at 500°C, for example, 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, 395°C, 400°C, 405°C, 410°C, 415°C, 420°C, 425°C, 430°C, 435°C, 440°C, 445°C, 450°C, 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C, 500°C, or a range between two of these values.

[0032] On the other hand, the sulfide-based compounds can be obtained, but are not limited to, by mixing lithium sulfide (Li2S) powder, phosphorus sulfide (P2S5) powder, and lithium halide (LiX) powder at 350°C in an atmosphere including hydrogen sulfide gas. 650℃, for example 350℃, 355℃, 360℃, 365℃, 370℃, 375℃, 380℃, 385℃, 390℃, 395℃, 400℃, 405℃, 410℃, 415℃, 420℃, 425℃, 430℃, 435℃, 440℃, 445℃, 450℃, 455℃, 460℃, 465℃, 470℃, 475℃, 480℃, 485℃, 490℃, 495℃, 500℃, 505℃ Firing at temperatures ranging from 510℃, 515℃, 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃, 595℃, 600℃, 605℃, 610℃, 615℃, 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, or between two of these values.

[0033] Here, the components can be calculated and mixed according to stoichiometry to achieve the desired composition.

[0034] Here, in the crystal phase of the sulfide-germanium type crystal structure, the molar ratio of lithium (Li) to phosphorus (P), Li / P, can be 5.00 to 7.00, for example, 5.00, 5.05, 5.10, 5.15, 5.20, 5.25, 5.30, 5.35, 5.40, 5.45, 5.50, 5.55, 5.60, 5.65, 5.70, 5.75, 5.80. The values ​​may be 5.85, 5.90, 5.95, 6.00, 6.05, 6.10, 6.15, 6.20, 6.25, 6.30, 6.35, 6.40, 6.45, 6.50, 6.55, 6.60, 6.65, 6.70, 6.75, 6.80, 6.85, 6.90, 6.95, 7.00, or a range between two of these values, but are not limited to these.

[0035] Adjusting the Li / P ratio changes the arrangement and distribution ratio of lithium ions within the compound, thereby improving ionic conductivity.

[0036] Furthermore, in the crystal phase of the sulfide-germanium-type crystal structure, the molar ratio of sulfur (S) to phosphorus (P), S / P, can be 4.00~6.00, for example 4.00, 4.05, 4.10, 4.15, 4.20, 4.25, 4.30, 4.35, 4.40, 4.45, 4.50, 4.55, 4.60, 4.65, 4.70, 4.75, 4.80, 4.85, 4.90, 4.95, 5.00, 5.05, 5.10, 5.15, 5.20, 5.25, 5.30, 5.35, 5.40, 5.45, 5.50, 5.55, 5.60, 5.65, 5.70, 5.75, 5.80, 5.85, 5.90, 5.95, 6.00, or a range between two of these values, but not limited to these.

[0037] By adjusting the S / P value, the chemical stability and high ionic conductivity of the compound can be ensured in a balanced manner.

[0038] In the sulfide-germanium ore type crystal structure, if sulfur is replaced with halide anions, the cubic crystal system can be stabilized, thus allowing it to have a cubic crystal system structure at room temperature.

[0039] The substituted halogen element creates a vacancy at the Li site inside the unit cell of silver-germanium sulfide, thereby reducing the activation energy and forming a new lithium-ion conduction pathway, which in turn improves the lithium-ion conductivity.

[0040] On the other hand, the crystal phase of the sulfogermanite-type crystal structure may include two or more halogen elements. Halogen elements include F, Cl, Br, and I, but in compounds with a sulfogermanite-type crystal structure, Cl, Br, and I are commonly used.

[0041] Here, in the crystal phase of the sulfide-germanium type crystal structure, the molar ratio of halogen (X) to phosphorus (P), X / P, can be 1.00 to 2.00, for example, 1.00, 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, 1.20, 1.22, 1.24, 1.26, 1.28, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40, 1.42. The values ​​may be 1.44, 1.46, 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, 1.66, 1.68, 1.70, 1.72, 1.74, 1.76, 1.78, 1.80, 1.82, 1.84, 1.86, 1.88, 1.90, 1.92, 1.94, 1.96, 1.98, 2.00, or a range between two of these values, but are not limited to these.

[0042] In one embodiment, the crystal phase of the sulfide-germanium ore-type crystal structure can be represented by the following chemical formula 1: [Chemical Formula 1] Li 7-x PS 6-x X x In the chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0 ≤ x ≤ 2.

[0043] Step (b) may involve pulverizing the prepared sulfide compound to obtain an average particle size (D). 50 The step is for particles smaller than 3 μm.

[0044] Compounds with a sulfide-germanium ore-type crystal structure are difficult to achieve the desired particle size range during pulverization due to their unique ductility, and are prone to leaving coarse powder or uneven particle size distribution.

[0045] Furthermore, since the sulfide compounds with the sulfide-germanium sulfide crystal structure are easily degraded by air, moisture, etc., resulting in a decline in performance, special pulverization processes may be required.

[0046] Therefore, in step (b), the sulfide compound can be pulverized using a wet pulverization method.

[0047] Here, the average particle size of the pulverized particles can be less than 3 μm, for example, 3 μm, 2.75 μm, 2.5 μm, 2.25 μm, 2 μm, 1.75 μm, 1.5 μm, 1.45 μm, 1.4 μm, 1.35 μm, 1.3 μm, 1.25 μm, 1.2 μm, 1.15 μm, 1.1 μm, 1.05 μm, 1 μm, 0.95 μm, 0.9 μm, 0.85 μm, 0.8 μm, 0.75 μm, 0.7 μm, 0.65 μm, 0.6 μm, 0.55 μm. μm, 0.5μm, 0.48μm, 0.46μm, 0.44μm, 0.42μm, 0.4μm, 0.38μm, 0.36μm, 0.34μm, 0.32μm, 0.3μm, 0.28μm, 0.26μm, 0.24μm, 0.22μm, 0.2μm, 0.18μm, 0.16μm, 0.14μm, 0.12μm, 0.1μm, 0.08μm, 0.06μm, 0.04μm, 0.02μm, or a range between two of these values.

[0048] Here, the pulverization process can be repeated more than once. For example, it can be performed 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 times or more. However, if the process is performed too many times, the sulfide compound may easily deteriorate.

[0049] Here, the wet pulverization in step (b) can be performed using at least one selected from the group consisting of a ball mill, pebble mill, rod mill, roller mill, colloid mill, impact mill, jet mill, bead mill, vibratory mill, stirred mill, disc mill, and pulverizing and classifying machine, but is not limited thereto.

[0050] In one embodiment, the pulverization can be performed at temperatures below 15°C, such as 15°C, 14.5°C, 14°C, 13.5°C, 13°C, 12.5°C, 12°C, 11.5°C, 11°C, 10.5°C, 10°C, 9.5°C, 9°C, 8.5°C, 8°C, 7.5°C, 7°C, 6.5°C, 6°C, 5.5°C, 5°C, 4.5°C, 4°C, 3.5°C, 3°C, 2.5°C, 2°C, 1.5°C, 1°C, 0.5°C, 0°C, or a range between two of these values.

[0051] By performing the pulverization at low temperatures, the ductility of the sulfide compounds can be minimized, resulting in more precise control over particle size distribution.

[0052] In particular, since the heat generated during the pulverization process may cause the particle size distribution to become uneven, the particle size distribution of the micro-pulverized particles may change depending on the temperature control method.

[0053] In another example, the pulverization can be performed in a system that includes a cooler, a bead mill, and a slurry tank.

[0054] A bead mill is a device that crushes materials by feeding them into a grinding container along with beads, and adjusts the particle size through collisions with small beads. The material to be crushed can be mixed with a solvent and then fed into a grinding container equipped with stirring blades.

[0055] In particular, during the pulverization process, cooling water circulates sequentially through a cooler, a bead mill, a slurry tank, and back to the cooler. The temperature of the cooling water can be maintained below 5°C, for example, 5°C, 4.9°C, 4.8°C, 4.7°C, 4.6°C, 4.5°C, 4.4°C, 4.3°C, 4.2°C, 4.1°C, 4°C, 3.9°C, 3.8°C, 3.7°C, 3.6°C, 3.5°C, 3.4°C, 3.3°C, 3.2°C, 3.1°C, 3°C, and 2°C. 9℃, 2.8℃, 2.7℃, 2.6℃, 2.5℃, 2.4℃, 2.3℃, 2.2℃, 2.1℃, 2℃, 1.9℃, 1.8℃, 1.7℃, 1.6℃, 1.5℃, 1.4℃, 1.3℃, 1.2℃, 1.1℃, 1℃, 0.9℃, 0.8℃, 0.7℃, 0.6℃, 0.5℃, 0.4℃, 0.3℃, 0.2℃, 0.1℃, 0℃, or a range between two of these values.

[0056] If the cooling water is circulated as described above, more efficient cooling can be achieved, and the temperature of the slurry itself becomes lower, thereby suppressing the ductility of the sulfide compounds, thus producing micronized particles with a narrow particle size distribution.

[0057] Based on the slurry fed into the bead mill, beads can be added in the range of 30-90% by weight, for example, 30%, 31%, 32%, 33%, 34%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, 52.5%, 55%, 57.5%, 60%, 62.5%, 65%, 67.5%, 70%, 72.5%, 75%, 77.5%, 80%, 82.5%, 85%, 87.5%, 89%, 90%, or any two of these values. Insufficient bead filling may result in difficulty in grinding, while excessive filling may lead to coarse powder.

[0058] The beads can be selected from ZrO2, Al2O3, Y2O3, HfO2, etc., depending on the purpose. Beads with an average particle size of 0.05~1.5mm can be used, such as 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.45mm, 1.5mm, or a range between two of these values, but are not limited thereto.

[0059] To minimize the degradation of the sulfide compounds, the wet milling in step (b) can be performed using a solvent with a moisture content of less than 12.0 ppm.

[0060] Here, the water content of the solvent can be less than 12.0 ppm, for example, 11.9 ppm, 11.7 ppm, 11.5 ppm, 11.3 ppm, 11.1 ppm, 10.9 ppm, 10.7 ppm, 10.5 ppm, 10.3 ppm, 10.1 ppm, 9.9 ppm, 9.7 ppm, 9.5 ppm, 9.3 ppm, 9.1 ppm, 8.9 ppm, 8.7 ppm, 8.5 ppm, 8.3 ppm, 8.1 ppm, 7.9 ppm, 7.7 ppm, 7.5 ppm, 7.3 ppm, 7.1 ppm, 6.9 ppm, 6.7 ppm, 6.5 ppm, 6. 3ppm, 6.1ppm, 5.9ppm, 5.7ppm, 5.5ppm, 5.3ppm, 5.1ppm, 4.9ppm, 4.7ppm, 4.5ppm, 4.3ppm, 4.1ppm, 3.9ppm, 3.7ppm, 3.5ppm, 3.3ppm, 3.1ppm, 2.9ppm, 2.7ppm, 2.5ppm, 2.3ppm, 2.1ppm, 1.9ppm, 1.7ppm, 1.5ppm, 1.3ppm, 1.1ppm, 0.9ppm, 0.7ppm, 0.5ppm, 0.3ppm, 0.1ppm, or a range between two of these values.

[0061] For example, the wet pulverization may be performed after dispersing the sulfide compound prepared in step (a) in the solvent.

[0062] The sulfide compounds are prone to degradation, leading to a decline in electrochemical performance. In particular, as the pulverization process continues, the surface area of ​​the particles increases, making them more susceptible to degradation, thus necessitating its suppression.

[0063] The solvent can be a compound with one or more alkyl groups bonded to the benzene ring. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl. Compounds with one, two, or three alkyl groups bonded to the benzene ring exist, but are not limited to these. That is, to minimize the water content in the solvent, a non-polar solvent can be used.

[0064] However, using solvents with low water content alone may not be sufficient to suppress the degradation of the sulfide compounds.

[0065] Although its exact mechanism of action has not yet been elucidated, the sulfide compounds may deteriorate due to impurities such as various gases that will inevitably dissolve in the solvent.

[0066] Therefore, the solvent can be a solvent purified by microfiltration and molecular sieve.

[0067] If the solvent is purified by passing it through a microfilter and molecular sieve, the water content can be reduced while removing components in the solvent that may degrade the sulfide compounds.

[0068] In particular, the solvent may be a solvent that has been purified by a microfilter and then by a molecular sieve.

[0069] If the solvent is purified by a microfilter and then by a molecular sieve, impurities can be removed along with the solvent without reducing the performance of the molecular sieve.

[0070] Since the performance of the molecular sieve may vary depending on the moisture and / or impurity content and composition of the solvent, the solvent can be purified by microfiltration before the molecular sieve is applied.

[0071] As the microfilter, any microfilter capable of removing moisture present in the solvent without leaving any residue in the solvent can be used, regardless of the material. For example, polymeric materials, ceramic materials, and metallic materials can be used.

[0072] On the other hand, the microfilter may use a pore size of 0.1 to 1 μm, for example 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, or a range between two of these values.

[0073] The molecular sieve is a material with constant and extremely small pores, which can be used to remove various impurities such as gases, liquids, and dissolved substances. Here, the molecular sieve can adsorb the largest molecules capable of moving through the pores.

[0074] On the other hand, the molecular sieve may be a molecular sieve with a pore size of 1 to 10 Å, for example, 1 Å, 1.5 Å, 2 Å, 2.5 Å, 3 Å, 3.5 Å, 4 Å, 4.5 Å, 5 Å, 5.5 Å, 6 Å, 6.5 Å, 7 Å, 7.5 Å, 8 Å, 8.5 Å, 9 Å, 9.5 Å, 10 Å or a range between two of these values.

[0075] Since the performance of the molecular sieve may vary depending on the moisture and / or impurity content and composition of the solvent, the solvent can be purified by microfiltration before the molecular sieve is applied.

[0076] On the other hand, the pulverization in step (b) can be performed using an inert gas. Examples of inert gases include N2 and Ar.

[0077] The ionic conductivity of the pulverized sulfide compound particles at 25°C can exceed 2.90 mS / cm, for example, 2.90 mS / cm, 2.92 mS / cm, 2.94 mS / cm, 2.96 mS / cm, 2.98 mS / cm, 3.00 mS / cm, 3.02 mS / cm, 3.04 mS / cm, 3.06 mS / cm, 3.08 mS / cm, 3.10 mS / cm, 3.12 mS / cm, 3.14 mS / cm, 3.16 mS / cm, 3.18 mS / cm, 3.20 mS / cm, and 3.2 mS / cm. 2mS / cm, 3.24mS / cm, 3.26mS / cm, 3.28mS / cm, 3.30mS / cm, 3.32mS / cm, 3.34mS / cm, 3.36mS / cm, 3.38mS / cm, 3.40mS / cm, 3.42 mS / cm, 3.44mS / cm, 3.46mS / cm, 3.48mS / cm, 3.50mS / cm, 3.52mS / cm, 3.54mS / cm, 3.56mS / cm, 3.58mS / cm, 3.60mS / cm, 3.62mS / cm, 3.64mS / cm, 3.66mS / cm, 3.68mS / cm, 3.70mS / cm, 3.72mS / cm, 3.74mS / cm, 3.76mS / cm, 3.78mS / cm, 3.80mS / cm, 3.82mS / cm, 3.84mS / cm, 3.86mS / cm, 3.88mS / cm, 3.90mS / cm, 3.92mS / cm, 3.94mS / cm, 3.96mS / cm, 3.98mS / cm, 4.00mS / cm, 4.05mS / cm 4.10mS / cm, 4.15mS / cm, 4.20mS / cm, 4.25mS / cm, 4.30mS / cm, 4.35mS / cm, 4.40mS / cm, 4.45mS / cm, 4.50mS / cm, 4.55mS / cm, 4.60mS / cm, 4.65mS / cm, 4.70mS / cm, 4.75mS / cm, 4.80mS / cm, 4.85mS / cm, 4.90mS / cm, 4.95mS / cm, 5.00mS / cm, or a range between two of these values.

[0078] The degradation of the sulfide compound particles is suppressed during the pulverization process, thereby achieving a relatively high ionic conductivity.

[0079] On the other hand, the critical current density of the pulverized sulfide compound particles can exceed 1.7 mA / cm². 2 For example, 1.71 mA / cm 2 1.75mA / cm2 1.8mA / cm 2 1.85mA / cm 2 1.9 mA / cm 2 1.95mA / cm 2 2mA / cm 2 2.05mA / cm 2 2.1 mA / cm 2 2.15mA / cm 2 2.2mA / cm 2 2.25mA / cm 2 2.3mA / cm 2 2.35mA / cm 2 2.4mA / cm 2 2.45mA / cm 2 2.5mA / cm 2 Or the range between two of these values.

[0080] The sulfide compound particles pulverized according to the described process can exhibit excellent atmospheric stability.

[0081] [Critical Current Density] Here, critical current density refers to the critical current density at which a short circuit occurs when a symmetrical battery with Li metal at both ends of a solid electrolyte layer manufactured by applying 200 mg of the sulfide-based solid electrolyte compound at 4 tons of pressure for 2 minutes is charged and discharged at 25°C with the current value per unit area increased.

[0082] The sulfide compound particles can also be used to manufacture solid electrolyte membranes in place of separation membranes, but they can also be mixed with positive electrode active materials to create positive electrodes.

[0083] If a solid electrolyte with small particle size is used, the contact area with the positive electrode active material becomes wider, thus resulting in better electrochemical characteristics.

[0084] Therefore, as a solid electrolyte for positive electrode composite materials, a solid electrolyte with a particle size of less than 1 μm can be used.

[0085] Here, the proportion of particles with a particle size of less than 1 μm in the particles obtained in step (b) can be 20% by weight or more, for example, 20% by weight, 20.5% by weight, 21% by weight, 21.5% by weight, 22% by weight, 22.5% by weight, 23% by weight, 23.5% by weight, 24% by weight, 24.5% by weight, 25% by weight, 25.5% by weight, 26% by weight, 26.5% by weight, 27% by weight, 27.5% by weight, 28% by weight, 28.5% by weight, 29% by weight, 29.5% by weight, 30% by weight, 30.5% by weight, 31% by weight, 31.5% by weight, 32% by weight, 32.5% by weight, 33% by weight, 33.5% by weight. 4% by weight, 34.5% by weight, 35% by weight, 35.5% by weight, 36% by weight, 36.5% by weight, 37% by weight, 37.5% by weight, 38% by weight, 38.5% by weight, 39% by weight, 39.5% by weight, 40% by weight, 40.5% by weight, 41% by weight, 41.5% by weight, 42% by weight, 42.5% by weight, 43% by weight, 43.5% by weight, 44% by weight, 44.5% by weight, 45% by weight, 45.5% by weight, 46% by weight, 46.5% by weight, 47% by weight, 47.5% by weight, 48% by weight, 48.5% by weight, 49% by weight, 49.5% by weight, 50% by weight, or a range between two of these values.

[0086] The higher the proportion of small particles, the easier it is to use as a solid electrolyte for positive electrode composite materials, but the possibility of degradation of the sulfide-based compounds may also increase.

[0087] In one embodiment, step (b) may be further included, but is not limited to, step (c) of separating particles with a particle size of less than 1 μm from the particles.

[0088] The particles with a particle size of less than 1 μm obtained through step (c) can be used as solid electrolytes for positive electrode composites, and the remaining particles can be used for solid electrolyte membranes.

[0089] Lithium secondary batteries According to another aspect of this specification, a lithium secondary battery is provided, comprising a lithium-ion conductive sulfide compound manufactured according to the manufacturing method described herein.

[0090] The lithium-ion conductive sulfide compound can be mixed with the positive electrode active material to form the positive electrode, or used as a solid electrolyte membrane to replace the separation membrane.

[0091] The lithium secondary battery may include a positive electrode, a negative electrode located opposite the positive electrode, and a separation membrane and an electrolyte located between the positive electrode and the negative electrode.

[0092] On the other hand, the lithium secondary battery can also be a battery in which the separator membrane is replaced with a solid electrolyte. The solid electrolyte can be disposed as a separate layer (solid electrolyte layer) between the positive and negative electrodes. In this case, an electrode slurry composition with further addition of solid electrolyte can be used when manufacturing the negative electrode.

[0093] That is, the lithium secondary battery may include a positive electrode, a negative electrode located opposite to the positive electrode, and a solid electrolyte membrane between the positive electrode and the negative electrode.

[0094] Furthermore, the lithium secondary battery can also be provided as an anode-free secondary battery. Here, since the positive electrode is the same as described above, detailed descriptions are omitted for convenience; only the remaining components not described above will be specifically described below. Furthermore, the following descriptions related to the negative electrode should be understood as assuming the presence of a negative electrode in the lithium secondary battery.

[0095] In one example, the positive electrode may include a positive current collector and a positive active material layer formed on the positive current collector. Here, the positive active material layer may include a positive active material and a lithium-ion conductive sulfide compound according to the various embodiments.

[0096] As long as the positive current collector does not cause chemical changes to the battery and is conductive, it is not particularly limited. For example, it can be made of stainless steel, aluminum, nickel, titanium, sintered carbon, or surface-treated aluminum or stainless steel with carbon, nickel, titanium, silver, etc. Furthermore, the positive current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on its surface to improve the adhesion of the positive electrode active material. For example, it can be used in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0097] As the positive electrode active material, compounds capable of reversible lithium insertion / extraction can be used. For example, there are cobalt oxide (LCO), nickel oxide (LNO), manganese oxide (LMO), nickel-cobalt-manganese oxide (NCM), nickel-cobalt-aluminum oxide (NCA), iron phosphate (LFP), and compounds doped with and / or coated with these, but not limited to these.

[0098] The positive electrode active material layer can be manufactured by coating the positive electrode current collector with a positive electrode slurry composition, which, along with the sulfide compound and the positive electrode active material, selectively includes conductive materials, binders, etc., as needed.

[0099] At this time, the sulfide compound may comprise 0.1% to 15% by weight of the total weight of the positive electrode active material layer.

[0100] On the other hand, the positive electrode active material may be contained in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, relative to the total weight of the positive electrode active material layer. Excellent capacity characteristics can be exhibited when contained within this range, but it is not necessarily limited thereto.

[0101] The conductive material is used to impart conductivity to the electrodes. In the constructed battery, any material that exhibits electronic conductivity without causing a chemical change can be used without particular restriction. Specific examples include graphite such as natural or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, and carbon fiber; metal powders or fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these materials can be used alone or in combination of two or more. The conductive material can be contained in an amount from 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0102] The binder enhances the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), PVDF-co-HFP, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these binders may be used alone or in combination of two or more. The binder may be contained in an amount from 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0103] The positive electrode can be prepared according to conventional positive electrode preparation methods. Specifically, it can be prepared by coating a positive electrode slurry composition, which is prepared by dissolving or dispersing a sulfide compound, a positive electrode active material, a binder, and a conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0104] The solvent can be any solvent commonly used in this technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, etc., and can be used alone or in combination with two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and preparation yield of the slurry, and to achieve a viscosity that provides excellent uniformity of thickness during subsequent coating for the preparation of the positive electrode.

[0105] In another embodiment, the positive electrode can also be prepared by casting the positive electrode slurry composition onto a separate support, and then pressing the membrane layer obtained by peeling it off from the support onto the positive electrode current collector.

[0106] The negative electrode may include a negative electrode current collector and a layer of negative electrode active material located on the negative electrode current collector.

[0107] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, it can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, materials with surface treatments of copper or stainless steel using carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloys. Furthermore, the negative electrode current collector typically has a thickness of 3 μm to 500 μm, and similarly to the positive electrode current collector, fine irregularities can be formed on its surface to enhance the adhesion of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0108] The negative electrode active material layer can be prepared by coating the negative electrode current collector with a negative electrode slurry composition that includes a conductive material together with the negative electrode active material and, if necessary, a binder.

[0109] As the negative electrode active material, compounds capable of reversible lithium insertion and extraction can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂. βMetal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the aforementioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, may be used, and any one or a mixture of two or more of them may be used. Furthermore, a thin film of metallic lithium may also be used as the negative electrode active material. In addition, all types of carbon materials, including low-crystallinity carbon and high-crystallinity carbon, may be used. Soft carbon and hard carbon are representative examples of low-crystallinity carbon, while high-crystallinity carbon includes amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature sintered carbon such as petroleum or coal tar pitchdered cokes.

[0110] The negative electrode active material may be contained in 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0111] The binder, as a component that assists in the bonding between the conductive material, the active material and the current collector, is typically added at a rate of 0.1% to 10% by weight, based on the total weight of the negative electrode active material layer.

[0112] The binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added at a rate of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0113] The conductive material is a component used to further improve the conductivity of the negative electrode active material, and can be added at a rate of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. This conductive material is not particularly limited as long as it is conductive without causing a chemical change in the battery. For example, graphite such as natural or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0114] In one embodiment, the negative electrode active material layer can be prepared by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing the negative electrode active material and a binder and conductive material in a solvent, onto the negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support and then pressing the film layer obtained by peeling it off from the support onto the negative electrode current collector.

[0115] On the other hand, in the lithium secondary battery, the separator separates the negative electrode from the positive electrode and provides a channel for the movement of lithium ions. Any separator commonly used in lithium secondary batteries can be used without particular restriction, but those with low resistance to electrolyte ion movement and excellent electrolyte wetting ability are particularly preferred. Specifically, porous polymer membranes can be used, such as porous polymer membranes made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more of these. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. Furthermore, to ensure heat resistance or mechanical strength, separators coated with ceramic components or polymeric substances can be used, and they can be selectively used in single-layer or multi-layer structures.

[0116] Furthermore, examples of electrolytes used in this invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the preparation of lithium secondary batteries.

[0117] Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0118] As for the organic solvent, any solvent that can act as a medium for the movement of ions participating in the electrochemical reaction of the battery can be used without particular restrictions. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (EPC) can be used. Carbonate solvents such as carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, which may contain double bonds, aromatic rings, or ether bonds); amides such as dimethylformamide; dioxolane solvents such as 1,3-dioxolane; or sulfolane solvents. Among these, carbonate solvents are preferred, and a mixture of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant, which can improve the charge-discharge performance of the battery, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, when cyclic carbonates and linear carbonates are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte performance can be excellent.

[0119] The lithium salt can be used without particular restriction as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used as the lithium salt. The concentration of the lithium salt is preferably in the range of 0.1M to 2.0M. When the concentration of the lithium salt is within this range, the electrolyte has suitable conductivity and viscosity, thus exhibiting excellent electrolyte performance, and lithium ions can move efficiently.

[0120] In addition to the electrolyte components, the electrolyte may further include, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and increasing battery discharge capacity, one or more additives such as halogenated alkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additives may comprise 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0121] In another example, the lithium secondary battery may be a type of all-solid-state battery that does not include an electrolyte but includes a solid electrolyte layer consisting of a solid electrolyte membrane.

[0122] Here, solid electrolyte membrane can mean an electrolyte membrane formed from sulfide-based solid electrolyte compounds that are a type of solid material capable of ion conduction.

[0123] Solid electrolyte membranes can be manufactured according to conventional methods known in the art, for example by pressing powdered sulfide-based solid electrolyte compounds into the desired shape.

[0124] However, since it is difficult to maintain the membrane structure using only sulfide compounds, solid electrolyte membranes can be manufactured by mixing binders.

[0125] Here, as an adhesive, it is preferable to have excellent adhesion to the sulfide-based compound, no decrease in ionic conductivity, and excellent flexibility. Furthermore, it should be easily peelable from release films commonly used in the manufacture of solid electrolyte membranes.

[0126] Examples include polyvinylidene fluoride (PVDF), PVDF-co-HFP copolymer, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or multiple copolymers thereof. One of these can be used alone or in mixtures of two or more.

[0127] This type of solid electrolyte membrane can be manufactured by coating a slurry, including sulfide compounds, binders and solvents, onto a release film and then removing the solvent.

[0128] Furthermore, the solid electrolyte membrane may, as needed, include conductive materials, auxiliary binders, etc.

[0129] Conductive materials are used to impart conductivity so that electrons can move along with ions. Their types are unrestricted as long as they are materials that do not undergo unnecessary chemical reactions and possess electronic conductivity. Examples include graphite, carbon black, acetylene black, Ketjen black, furnace black, lamp black, thermal cracking black, carbon fiber, carbon nanotubes, graphene, copper, aluminum, nickel, gold, silver, and conductive polymers.

[0130] In the solid electrolyte membrane, the content of the sulfide-based solid electrolyte compound can be 80-99.9% by weight, for example 80% by weight, 80.5% by weight, 81% by weight, 81.5% by weight, 82% by weight, 82.5% by weight, 83% by weight, 83.5% by weight, 84% by weight, 84.5% by weight, 85% by weight, 85.5% by weight, 86% by weight, 86.5% by weight, 87% by weight, 87.5% by weight, 88% by weight, 88.5% by weight, and 89% by weight. 89.5% by weight, 90% by weight, 90.5% by weight, 91% by weight, 91.5% by weight, 92% by weight, 92.5% by weight, 93% by weight, 93.5% by weight, 94% by weight, 94.5% by weight, 95% by weight, 95.5% by weight, 96% by weight, 96.5% by weight, 97% by weight, 97.5% by weight, 98% by weight, 98.5% by weight, 99% by weight, 99.5% by weight, 99.9% by weight, or a range between two of these values, but not limited to these.

[0131] Here, the thickness of the solid electrolyte membrane is not limited and can range from 5 to 300 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 1 55μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, 200μm, 205μm, 210μm, 215μm, 220μm, 225μm, 230μm, 235μm, 240μm, 245μm, 250μm, 255μm, 260μm, 265μm, 270μm, 275μm, 280μm, 285μm, 290μm, 295μm, 300μm, or a range between two of these values.

[0132] On the other hand, the solid electrolyte membrane may have a free-standing characteristic that allows it to be used without a separate support, but is not limited thereto.

[0133] The lithium secondary battery may optionally further include an electrode assembly housing the positive electrode, the negative electrode, and the separation membrane, or an electrode assembly housing the positive electrode, the negative electrode, and the solid electrolyte membrane, and a sealing component for sealing the battery container.

[0134] As described above, lithium secondary batteries containing sulfide compounds according to this specification exhibit excellent electrochemical characteristics and can therefore be used in portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0135] The shape of the lithium secondary battery according to the present invention is not particularly limited, but it can be cylindrical, square, pouch-shaped, or coin-shaped, etc. Furthermore, the lithium secondary battery can be used not only as a battery cell for powering small devices, but also preferably as a unit battery in medium to large-sized battery modules containing multiple battery cells.

[0136] According to another aspect of the present invention, a battery module comprising the lithium secondary battery as a unit and / or a battery pack comprising the same can be provided.

[0137] The battery module or battery pack can be used as a power tool; an electric vehicle including electric vehicles (EVs), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEVs); or a power source for medium to large-sized equipment in a power storage system.

[0138] The following examples will provide a more detailed description of the described matters. However, these examples are for illustrative purposes only, and the scope of this specification should not be construed as being limited to these examples.

[0139] Manufacturing Example 1. Manufacturing of Sulfide Compounds Comparative Example 1 Inside the glove box (N2, H2O < 10 ppm), toluene as a solvent and the average particle size (D) of the particles are added to the grinding container integrated with the horizontal bead mill. 50 ) with a diameter of 6μm and Li 5.5 PS 4.5 Cl 1.5 The sulfide compounds were stirred to form a slurry. The water content of the solvent was measured to be 19.7 ppm.

[0140] Add 0.5mm ZrO2 beads at 60% by weight of the slurry to the grinding container, set the stirring speed to 6m / s and the pump speed to 2ml / s, circulate the stirred slurry for 40 minutes, and then transfer it to the container.

[0141] Next, the product was dehydrated inside a glove box using a vacuum filtration device (Pore size: 0.5 μm). The dehydrated product was then dried in a vacuum oven (10 torr, 100°C) for 2 hours and cooled in a N2 atmosphere (50°C) before being recovered, thereby producing pulverized sulfide compounds.

[0142] Comparative Example 2 Except for the solvent purified by using a porous microfilter (Pore size: 0.5 μm) incorporated into the shell to remove moisture, the pulverized sulfide compound was prepared in the same manner as in Comparative Example 1.

[0143] Here, the water content of the solvent was measured to be 12.0 ppm.

[0144] Comparative Example 3 Except for the solvent refined by introducing bead-shaped zeolite molecular sieves with an average diameter of 3-5 mm into the solvent, the pulverized sulfide compound was manufactured in the same manner as in Comparative Example 1.

[0145] Example Except for the solvent purified by passing it through a microfilter (Pore size: 0.5 μm) used in Comparative Example 2 and then into the molecular sieve used in Comparative Example 3, the pulverized sulfide compound was prepared in the same manner as in Comparative Example 1.

[0146] Here, the water content of the solvent was measured to be 8.0 ppm.

[0147] Experimental Example 1. Characteristic Analysis of Sulfide Compounds The proportion of particles smaller than 1 μm and D were confirmed by particle size analysis of the particulate sulfide compounds in Manufacturing Example 1. 50 D max The ionic conductivity was measured and is shown in Table 1 below.

[0148] [Table 1]

[0149] According to Table 1, it can be confirmed that the quality of the pulverized product changes depending on the method of solvent refining during the wet pulverization of sulfide-based solid electrolyte compounds. For example, in Comparative Example 2, which uses a microfilter to refine the solvent, the ionic conductivity increases compared to Comparative Example 1.

[0150] On the other hand, the ionic conductivity of Comparative Example 3, which uses molecular sieve-refined solvent, decreased compared to Comparative Example 1.

[0151] Compared to Comparative Example 1, the ionic conductivity was significantly improved in the example of refining the solvent in the order of microfiltration and molecular sieve.

[0152] Manufacturing Example 2. Manufacturing of Solid Electrolyte Membrane and Lithium Secondary Battery (Symmetric Cell) A pressure battery was manufactured by applying a uniaxial pressure of 200 MPa to 200 mg of the sulfide compound in the comparative examples and embodiments. At this time, Li metal was inserted into both ends of the solid electrolyte, thereby creating a symmetrical lithium secondary battery with a Li / sulfide compound / Li electrode structure.

[0153] Experimental Example 2. Evaluation of the electrochemical characteristics of a lithium secondary battery (symmetric battery) The electrochemical characteristics of the lithium secondary battery (symmetric battery) manufactured in Manufacturing Example 2 were evaluated using a Toyo TOSCAT-3100 instrument.

[0154] To determine the critical current value used for atmospheric stability assessment, the charge and discharge current values ​​were gradually increased, and the Liplating / stripping characteristics were evaluated. The current value at which a cell short occurs was identified as the critical current value, and the results are presented below. Figure 1 middle.

[0155] Here, the critical current density is expressed as 1.5 mA / cm². 2 (Comparative Example 1), 1.7 mA / cm 2 (Comparative Example 2) 1.6 mA / cm 2 (Comparative Example 3) 2.1 mA / cm 2 (Example).

[0156] In addition, a current of 0.25–0.30 mA per unit area was applied for 300 cycles to evaluate the electrochemical stability of the solid electrolyte. Stripping / plating was repeated for 1 hour each cycle to evaluate the electrochemical stability of the solid electrolyte; here, 0.25 mA / cm² was applied for up to 150 cycles. 2 The current is applied at 0.30 mA / cm² in subsequent cycles. 2 The current, and its results are shown in Figure 1 middle.

[0157] Reference Figure 1 It can be confirmed that during the wet pulverization of sulfide-based solid electrolyte compounds, the quality of the pulverized product changes depending on the method of refining the solvent.

[0158] For example, in Comparative Example 2, which uses a microfilter to purify the solvent, the critical current value is increased compared to Comparative Example 1, but the electrochemical stability shows a similar level.

[0159] On the other hand, in Comparative Example 3, where the solvent was purified using molecular sieves, the critical current value also increased, but a short circuit occurred in the symmetrical cell, and the electrochemical stability decreased instead.

[0160] Compared to Comparative Example 1, the example in which the solvent was purified in the order of microfiltration and molecular sieve showed improved critical current and electrochemical stability. In particular, unlike the symmetrical cell of the Comparative Example which experienced overvoltage or short circuit, the symmetrical cell of the example showed stable results without overvoltage or short circuit even up to 600 hours.

[0161] The embodiments of the present invention have been described above. However, those skilled in the art can make various modifications and alterations to the present invention by adding, changing, deleting, or supplementing constituent elements without departing from the spirit of the present invention as described in the claims, and these modifications and alterations should also be considered to be included within the scope of the present invention.

Claims

1. A method for manufacturing a lithium-ion conductive sulfide compound, comprising: (a) Steps for preparing sulfide compounds comprising a crystal phase with an Argyrodite-type crystal structure; as well as (b) The step of wet pulverizing the sulfide compound to obtain particles with an average particle size of less than 3 μm; The wet milling process is performed using a solvent with a moisture content of less than 12.0 ppm.

2. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, The crystal phase of the silver-germanium sulfide-type crystal structure is represented by the following chemical formula 1: [Chemical Formula 1] Li 7-x PS 6-x X x In the chemical formula 1, X is selected from at least one of the group consisting of Cl, Br, and I. 0≤x≤2。 3. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, The wet pulverization in step (b) is performed using at least one selected from the group consisting of a ball mill, pebble mill, rod mill, roller mill, colloid mill, impact mill, jet mill, bead mill, vibratory mill, stirred mill, disc mill, and pulverizing and classifying machine.

4. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, The solvent is a compound having one or more alkyl groups bonded to a benzene ring.

5. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, The solvent is purified by microfiltration and molecular sieve.

6. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 5, characterized in that, The solvent is purified by microfiltration and then by molecular sieve.

7. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 5, characterized in that, The pore size of the microfilter is 0.1~1μm.

8. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, The proportion of particles with a size of less than 1 μm in the particles obtained in step (b) is more than 20% by weight.

9. The method for manufacturing the lithium-ion conductive sulfide compound according to claim 1, characterized in that, Following step (b), the method further includes step (c) of separating particles with a particle size of less than 1 μm from the particles.

10. A lithium secondary battery comprising a lithium-ion conductive sulfide compound manufactured by the manufacturing method according to any one of claims 1 to 9.

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