Method for manufacturing lithium-ion conductive sulfide-based compound

Abstract

The present specification relates to: a method for manufacturing a lithium-ion conductive sulfide-based compound; and a lithium secondary battery including same. More specifically, the present specification relates to a method for obtaining a sulfide-based compound having excellent electrochemical properties and atmospheric stability by resolving the problem that a sulfide-based solid electrolyte compound having an argyrodite-type crystal structure easily deteriorates when pulverized.

Description

Method for manufacturing lithium ion conductive sulfide-based compounds

[0001] This specification relates to a method for manufacturing a lithium ion-conducting sulfide-based compound and a lithium secondary battery comprising the same. More specifically, this specification relates to a method for obtaining a sulfide-based compound having excellent electrochemical properties and atmospheric stability by improving the problem of easy degradation during grinding of a sulfide-based solid electrolyte compound having an azirodite-type crystal structure.

[0002]

[0003] A battery stores electrical power by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example of such a battery is the lithium secondary battery, which stores electrical energy based on the difference in chemical potential when lithium ions intercalate or deintercalate at the positive and negative electrodes.

[0004] The above lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive and negative active materials, and by filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes.

[0005] However, these organic or polymer electrolytes typically use flammable organic solvents. Therefore, if abnormally high temperatures occur due to internal or external factors of the lithium secondary battery, a fire or explosion may occur due to the electrolyte.

[0006] Due to these safety concerns, solid-state batteries utilizing solid electrolytes are attracting attention as a substitute for liquid batteries. Solid-state batteries are expected to be commercialized as next-generation batteries with high energy density due to their high stability.

[0007] Among the solid electrolytes used in lithium-ion batteries, sulfide-based solid electrolytes are currently receiving significant attention. Various crystal structures of sulfide-based solid electrolytes are known, one of which is the argyrodite-type crystal structure.

[0008] However, sulfide-based solid electrolytes with an agitite-type crystal structure have problems such as high reactivity with moisture and oxygen, complex manufacturing processes, and significant variability in ionic conductivity performance. Additionally, due to the nature of solid-phase materials, micronization is essential to maximize the contact surface area; however, this grinding process leads to degradation such as amorphization and impurity formation, resulting in a decrease in ionic conductivity.

[0009]

[0010] According to the present specification, one objective is to provide a method for manufacturing a lithium ion-conducting sulfide-based compound with improved electrochemical performance, which prevents performance degradation caused by deterioration that easily occurs during the grinding of a sulfide-based compound having an azirodite-type crystal structure.

[0011] In addition, the present specification has one objective of providing a lithium secondary battery using a sulfide-based solid electrolyte compound as defined herein.

[0012] The purposes of the present invention are not limited to those mentioned above, and other purposes and advantages of the present invention not mentioned may be understood from the following description and will be more clearly understood from the embodiments of this specification. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0013]

[0014] According to one aspect of the present specification, a method for preparing a lithium ion-conducting sulfide-based compound is provided, comprising: (a) preparing a sulfide-based compound having a crystalline phase having an argyrodite-type crystal structure; and (b) wet grinding the sulfide-based compound to obtain particles having an average particle size of 3 μm or less, wherein the wet grinding is performed using a solvent having a moisture content of less than 12.0 ppm.

[0015] In one embodiment, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0016] [Chemical Formula 1]

[0017] Li 7-x PS 6-x X x

[0018] In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0≤x≤2.

[0019] Here, the wet grinding of step (b) above may be performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill.

[0020] Meanwhile, the above solvent may be a compound in which one or more alkyl groups are bonded to a benzene ring.

[0021] In addition, the solvent may be purified using a microfilter and a molecular sieve.

[0022] In particular, the above solvent may be purified by microfilter and then purified by molecular sieve.

[0023] Meanwhile, the above microfilter may have a pore size of 0.1 to 1 μm.

[0024] Here, the proportion of particles with a particle size of 1 μm or less among the particles obtained in step (b) above may be 20 weight% or more.

[0025] In one embodiment, after step (b), the method may further include step (c) of separating particles having a particle size of 1 μm or less among the particles.

[0026] According to another aspect of the present specification, a lithium secondary battery is provided, comprising a lithium ion conductive sulfide-based compound manufactured according to the manufacturing method described above.

[0027]

[0028] According to the present specification, it is possible to provide a sulfide compound with superior electrochemical properties by suppressing the deterioration that may occur during the grinding of an azirodite-type sulfide compound.

[0029] In addition to the effects described above, the specific effects of the present invention are described together with the specific details of the specification below.

[0030]

[0031] Figure 1 is the result of an analysis of the critical current density and electrochemical characteristics of a sulfide-based compound according to one example of the present specification.

[0032]

[0033] For convenience, specific terms are defined herein to facilitate a better understanding of this specification. Unless otherwise defined herein, scientific and technical terms used in this invention shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0034]

[0035] Method for manufacturing lithium ion conductive sulfide-based compounds

[0036] A method for preparing a lithium ion-conducting sulfide-based compound according to one aspect of the present specification comprises: (a) preparing a sulfide-based compound having a crystalline phase having an argyrodite-type crystal structure; and (b) wet grinding the sulfide-based compound to obtain particles having an average particle size of 3 μm or less; wherein the wet grinding may be performed using a solvent having a moisture content of less than 12.0 ppm.

[0037] Step (a) above may be a step of synthesizing a lithium ion-conducting sulfide-based compound or preparing a compound prior to grinding.

[0038] The above sulfide-based compound has lithium ion conductivity and can have a crystal phase with an azirodite-type crystal structure.

[0039] The term "azirodite-type crystal structure" refers to a structure identical to that of azirodite (Ag8GeS6), a silver-germanium-sulfur mineral. The azirodite-type crystal structure can possess orthorhombic (Pna21) and cubic (F-43m) phases, among which the cubic crystal structure exhibits high lithium ion conductivity. Typically, the azirodite-type crystal structure displays the cubic phase, which exhibits excellent lithium ion conductivity at high temperatures, and the orthorhombic phase at low temperatures.

[0040] For example, Li7PS6, Li6PS5X (where X is at least one of Cl, Br, and I) are known as lithium ion conductive solid electrolyte compounds having an azirodite-type crystal structure.

[0041] However, the azirodite crystal structure has the problem of easily degrading performance due to sensitivity to air and humidity. Therefore, compounds having an azirodite crystal structure may experience performance degradation or easily form impurities during the manufacturing process.

[0042] For example, the above sulfide-based compound is prepared by mixing lithium sulfide (Li2S) powder, phosphorus sulfide (P2S5) powder, and lithium halide (LiX) powder, and subjecting the mixture to an inert atmosphere at 350–500°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. It can be obtained by firing at 500℃ or a temperature in the range between two of these values, but is not limited thereto.

[0043] Meanwhile, the above sulfide-based compound is prepared by mixing lithium sulfide (Li2S) powder, phosphorus sulfide (P2S5) powder, and lithium halide (LiX) powder, and subjecting the mixture to 350–650°C in an atmosphere containing hydrogen sulfide gas, 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, It may be obtained by firing at a temperature of 495℃, 500℃, 505℃, 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 a range between two of these values, but is not limited thereto.

[0044] Here, each component can be stoichiometrically calculated and mixed to have the desired composition.

[0045] Here, in the crystalline phase of the azirodite-type crystal structure, the molar ratio Li / P of lithium (Li) and phosphorus (P) elements is 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, 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, It may be 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 is not limited thereto.

[0046] By adjusting the Li / P value, the arrangement and distribution ratio of lithium ions within the compound change, thereby improving ionic conductivity.

[0047] In addition, in the crystal phase of the azirodite-type crystal structure, the molar ratio S / P of sulfur (S) and phosphorus (P) elements is 4.00 to 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, It may be 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 is not limited thereto.

[0048] By adjusting the S / P value, the chemical stability and high ionic conductivity of the above compound can be secured in balance.

[0049] In an azyrodite-type crystal structure, replacing sulfur with a halogen anion stabilizes the cubic phase, allowing the structure to be maintained even at room temperature.

[0050] Substituted halogen elements can form vacancies at Li sites within the azirodite unit cell, thereby reducing activation energy and forming new lithium ion conduction pathways, which can consequently improve lithium ion conductivity.

[0051] Meanwhile, the crystal phase of the above-mentioned azyrodite-type crystal structure may contain two or more halogen elements. Halogen elements include F, Cl, Br, I, etc., but Cl, Br, I, etc. can typically be used in compounds having an azyrodite-type crystal structure.

[0052] Here, in the crystal phase of the azyrodite-type crystal structure, the molar ratio X / P of the halogen (X) element and the phosphorus (P) element is 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, 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 is not limited thereto.

[0053] In one embodiment, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0054] [Chemical Formula 1]

[0055] Li 7-x PS 6-xX x

[0056] In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0≤x≤2.

[0057] Step (b) above involves grinding the prepared sulfide-based compound to an average particle size (D 50 ) may be a step of obtaining particles of 3 μm or less.

[0058] Compounds with an agitite-type crystal structure are difficult to satisfy the desired particle size range during grinding due to their characteristic ductility, and coarse particles are likely to remain or the particle size distribution may be non-uniform.

[0059] In addition, since the sulfide-based compound having an azirodite-type crystal structure can easily deteriorate due to air, moisture, etc., and its performance may be reduced, a special grinding process may be required.

[0060] Therefore, in step (b) above, the sulfide-based compound can be ground using a wet grinding method.

[0061] Here, the average particle size of the ground particles is 3 μm or less, 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, 0.5 μm, 0.48 μm, 0.46 μm, 0.44 μm, 0.42 μm. It may be µm, 0.4 µm, 0.38 µm, 0.36 µm, 0.34 µm, 0.32 µm, 0.3 µm, 0.28 µm, 0.26 µm, 0.24 µm, 0.22 µm, 0.2 µm, 0.18 µm, 0.16 µm, 0.14 µm, 0.12 µm, 0.1 µm, 0.08 µm, 0.06 µm, 0.04 µm, 0.02 µm, or a range between two of these values.

[0062] Here, the grinding may be performed by repeating the process one or more times. For example, it may 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 or more times, but if the process is performed an excessively large number of times, the sulfide-based compound may easily deteriorate.

[0063] Here, the wet grinding of step (b) may be performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill, but is not limited thereto.

[0064] In one embodiment, the grinding may be performed under conditions of 15°C or lower, for example, 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 in a range between two of these values.

[0065] By performing grinding at a low temperature, the ductility of the above sulfide-based compound is minimized, and as a result, the particle size distribution can be controlled more precisely.

[0066] In particular, since the particle size distribution may become non-uniform due to the heat generated during the grinding process, the particle size distribution of the finely ground particles may vary depending on the temperature control method.

[0067] In another example, the grinding can be performed in a system including a cooler, a bead mill, and a slurry tank.

[0068] A bead mill is equipment capable of controlling particle size through collisions with small beads by introducing the material along with beads into a grinding container and grinding it. It can be used by mixing the material to be ground in a solvent and then introducing it into a grinding container equipped with stirring blades.

[0069] In particular, in the grinding process, cooling water is circulated in the order of a cooler, a bead mill, a slurry tank, and a cooler, and the temperature of the cooling water is 5°C or lower, 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, 2.9°C, 2.8°C, 2.7°C, 2.6°C, 2.5°C, 2.4°C, 2.3°C, 2.2°C, 2.1°C, 2°C, 1.9°C, 1.8°C, 1.7°C, 1.6°C, 1.5°C, It may be maintained at 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 within a range between two of these values.

[0070] If the circulation of cooling water is carried out as described above, more efficient cooling is possible, and the temperature of the slurry itself is lowered, thereby suppressing the ductility of the sulfide-based compound, which allows for the production of finely ground particles with a narrow particle size distribution.

[0071] Beads may be introduced in an amount of 30 to 90 wt% based on the slurry introduced into the bead mill, for example, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 37.5 wt%, 40 wt%, 42.5 wt%, 45 wt%, 47.5 wt%, 50 wt%, 52.5 wt%, 55 wt%, 57.5 wt%, 60 wt%, 62.5 wt%, 65 wt%, 67.5 wt%, 70 wt%, 72.5 wt%, 75 wt%, 77.5 wt%, 80 wt%, 82.5 wt%, 85 wt%, 87.5 wt%, 89 wt%, 90 wt%, or a range between two of these values. If the beads are not sufficiently filled, grinding may be difficult, and if they are filled excessively, coarse particles may form.

[0072] The above beads may be selected from ZrO2, Al2O3, Y2O3, HfO2, etc., depending on the purpose, and have an average particle size of 0.05 to 1.5 mm, for example, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, or two of these values. You may use items within the specified range, but you are not limited to them.

[0073] To minimize the degradation of the above sulfide-based compound, the wet grinding of step (b) can be performed using a solvent with a moisture content of less than 12.0 ppm.

[0074] Here, the water content of the solvent is 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, 6.3 ppm, 6.1 ppm, 5.9 ppm, 5.7 ppm, 5.5 ppm, 5.3 ppm, 5.1 ppm, 4.9 ppm, 4.7 ppm, 4.5 ppm, 4.3 ppm, 4.1 ppm, 3.9 ppm, 3.7 ppm, 3.5 ppm, 3.3 ppm, 3.1 ppm, 2.9 ppm, 2.7 ppm, 2.5 ppm, 2.3 ppm, 2.1 ppm, 1.9 ppm, 1.7 ppm, 1.5 ppm, 1.3 ppm, 1.1 ppm, 0.9 ppm, 0.7 ppm, 0.5 ppm, 0.3 ppm, 0.1 ppm, or may satisfy a range between two of these values.

[0075] For example, the wet grinding above may be performed by dispersing the sulfide-based compound prepared in step (a) in the solvent and then grinding it.

[0076] The above-mentioned sulfide compounds can easily degrade, leading to a decrease in electrochemical performance. In particular, since the surface area of ​​the particles increases during the grinding process, making degradation more likely, it is necessary to suppress this.

[0077] The above solvent may be a compound in which one or more alkyl groups are bonded to a benzene ring. For example, alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl groups. There are compounds in which one, two, or three such alkyl groups are bonded to the benzene ring, but the solvent is not limited thereto. That is, a non-polar solvent may be used to minimize the water content in the above solvent.

[0078] However, it may be difficult to sufficiently suppress the deterioration of the above sulfide-based compounds by simply using a solvent with a low moisture content.

[0079] Although the exact mechanism of action has not been elucidated, the sulfide-based compound may deteriorate due to impurities that can inevitably be dissolved in the solvent, such as various gases.

[0080] Therefore, the above solvent may be purified using a microfilter and a molecular sieve.

[0081] When the above solvent is purified using a microfilter and a molecular sieve, the water content is reduced, and at the same time, components capable of degrading the above sulfide-based compound in the solvent can be removed.

[0082] In particular, the above solvent may be purified by microfilter and then purified by molecular sieve.

[0083] If the above solvent is purified with a microfilter and then purified with a molecular sieve, impurities can be removed without degrading the performance of the molecular sieve.

[0084] Since the performance of the molecular sieve may vary depending on the moisture and / or impurity content and composition in the solvent, the solvent may be purified first using a microfilter before the molecular sieve is applied.

[0085] The above microfilter can be used without limitation on the material, as long as it is capable of removing moisture present in the solvent and does not remain in the solvent. For example, polymer materials, ceramic materials, metal materials, etc., can be used.

[0086] Meanwhile, the microfilter may have 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.

[0087] The above molecular sieve is a material containing uniform and extremely small pores and can be used to remove various impurities such as gases, liquids, and dissolved substances. Here, the molecular sieve can adsorb the largest molecule among those capable of moving through the pores.

[0088] Meanwhile, the above molecular sieve may be used 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.

[0089] Since the performance of the molecular sieve may vary depending on the moisture and / or impurity content and composition in the solvent, the solvent may be purified first using a microfilter before the molecular sieve is applied.

[0090] Meanwhile, the grinding in step (b) above can be performed by introducing an inert gas. For example, N2, Ar, etc., can be used as the inert gas.

[0091] 분쇄된 상기 황화물계 화합물 입자는 25℃ 이온전도도가 2.90 mS / cm 초과, 예를 들어, 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, 3.22 mS / cm, 3.24 mS / cm, 3.26 mS / cm, 3.28 mS / cm, 3.30 mS / cm, 3.32 mS / cm, 3.34 mS / cm, 3.36 mS / cm, 3.38 mS / cm, 3.40 mS / cm, 3.42 mS / cm, 3.44 mS / cm, 3.46 mS / cm, 3.48 mS / cm, 3.50 mS / cm, 3.52 mS / cm, 3.54 mS / cm, 3.56 mS / cm, 3.58 mS / cm, 3.60 mS / cm, 3.62 mS / cm, 3.64 mS / cm, 3.66 mS / cm, 3.68 mS / cm, 3.70 mS / cm, 3.72 mS / cm, 3.74 mS / cm, 3.76 mS / cm, 3.78 mS / cm, 3.80 mS / cm, 3.82 mS / cm, 3.84 mS / cm, 3.86 mS / cm, 3.88 mS / cm, 3.90 mS / cm, 3.92 mS / cm, 3.94 mS / cm, 3.96 mS / cm, 3.98 mS / cm, 4.00 mS / cm, 4.05 mS / cm, 4.10 mS / cm, 4.15 mS / cm, 4.20 mS / cm, 4.25 mS / cm, 4.30 mS / cm, 4.35 mS / cm, 4.40 mS / cm, 4.45 mS / cm, 4.50 mS / cm, 4.55 mS / cm, 4.60 mS / cm, 4.65 mS / cm, 4.70 mS / cm, 4.75 mS / cm, 4.80 mS / cm, 4.85 mS / cm, 4.90 mS / cm, 4.95 mS / cm, 5.00 mS / cm 또는 이들 중 두 값의 사이 범위인 것일 수 있다.

[0092] The above sulfide-based compound particles can have relatively high ionic conductivity as deterioration is suppressed during the grinding process.

[0093] Meanwhile, the pulverized sulfide-based compound particles have a critical current density of 1.7 mA / cm² 2 Exceeding, e.g., 1.71 mA / cm² 2 , 1.75 mA / cm 2 , 1.8 mA / cm 2 , 1.85 mA / cm 2 , 1.9 mA / cm 2 , 1.95 mA / cm 2 , 2 mA / cm 2 , 2.05 mA / cm 2 , 2.1 mA / cm 2 , 2.15 mA / cm 2 , 2.2 mA / cm 2 , 2.25 mA / cm 2 , 2.3 mA / cm 2 , 2.35 mA / cm 2 , 2.4 mA / cm 2 , 2.45 mA / cm 2 , 2.5 mA / cm 2 Or it may be a range between two of these values.

[0094] The sulfide-based compound particles ground according to the above process may have excellent atmospheric stability.

[0095] [Critical Current Density]

[0096] Here, the critical current density is defined as the current value at which a cell short circuit occurs when charging and discharging a symmetric cell in which Li metal is positioned at both ends of a solid electrolyte layer prepared by pressurizing 200 mg of the sulfide-based solid electrolyte compound at 4 ton for 2 minutes at 25°C while increasing the current value per unit area.

[0097] The above sulfide-based compound particles can be used for manufacturing solid electrolyte membranes that replace separators, but they can also be used to manufacture a composite cathode by mixing them with a cathode active material.

[0098] Here, using a solid electrolyte with a small particle size increases the contact area with the positive electrode active material, so the electrochemical properties can be superior.

[0099] Therefore, a solid electrolyte with a particle size of 1 μm or less can be used for the anode composite.

[0100] Here, the proportion of particles having a particle size of 1 μm or less among the particles obtained in step (b) is 20 wt% or more, for example, 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt%, 22.5 wt%, 23 wt%, 23.5 wt%, 24 wt%, 24.5 wt%, 25 wt%, 25.5 wt%, 26 wt%, 26.5 wt%, 27 wt%, 27.5 wt%, 28 wt%, 28.5 wt%, 29 wt%, 29.5 wt%, 30 wt%, 30.5 wt%, 31 wt%, 31.5 wt%, 32 wt%, 32.5 wt%, 33 wt%, 33.5 wt%, 34 wt%, 34.5 wt%, 35 wt%, 35.5 wt%, 36 wt%, 36.5 wt%, 37 wt%, 37.5 wt%, 38 wt%, 38.5 wt%, 39 wt%, 39.5 wt%, 40 wt%, 40.5 wt%, 41 wt%, 41.5 wt%, 42 wt%, 42.5 wt%, 43 wt%, 43.5 wt%, 44 wt%, 44.5 wt%, 45 wt%, 45.5 wt%, 46 wt%, 46.5 wt%, 47 wt%, 47.5 wt%, 48 wt%, 48.5 wt%, 49 wt%, 49.5 wt%, 50 wt%, or a range between two of these values.

[0101] The higher the proportion of particles with small particle sizes, the easier it is to apply as a solid electrolyte for anode composites, but the possibility of the above sulfide-based compound deteriorating may also increase.

[0102] In one embodiment, after step (b), (c) a step of separating particles having a particle size of 1 μm or less among the particles may be further included, but is not limited thereto.

[0103] The particles with a particle size of 1 μm or less obtained through step (c) above can be used as a solid electrolyte for the anode composite, and the remaining particles can be used for the solid electrolyte membrane.

[0104]

[0105] lithium secondary battery

[0106] According to another aspect of the present specification, a lithium secondary battery is provided, comprising a lithium ion conductive sulfide-based compound manufactured according to the manufacturing method described above.

[0107] The above lithium ion conductive sulfide-based compound can be used to form a positive electrode by mixing it with a positive electrode active material, or it can be used as a solid electrolyte membrane to replace a separator.

[0108] The above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0109] Meanwhile, the above lithium secondary battery may have the separator replaced with a solid electrolyte. The solid electrolyte may be disposed as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. In such cases, an electrode slurry composition in which the solid electrolyte is further added during the manufacture of the negative electrode may be used.

[0110] That is, the lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a solid electrolyte membrane interposed between the positive electrode and the negative electrode.

[0111] In addition, the above-mentioned lithium secondary battery may be provided as an anode-free secondary battery. Here, since the anode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not described above will be explained in detail below. Furthermore, the description regarding the anode to be described later should be understood as being based on the premise that an anode is present in the above-mentioned lithium secondary battery.

[0112] In one example, the anode may include an anode current collector and an anode active material layer formed on the anode current collector. Here, the anode active material layer may include an anode active material and a lithium ion conductive sulfide-based compound according to the various embodiments described above.

[0113] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0114] The above-mentioned cathode active material may use a compound capable of reversible intercalation / deintercalation of lithium. Examples include, but are not limited to, cobalt oxide-based (LCO), nickel oxide-based (LNO), manganese oxide-based (LMO), nickel-cobalt-manganese oxide-based (NCM), nickel-cobalt-aluminum oxide-based (NCA), iron phosphate-based (LFP), and those doped with and / or coated therefrom.

[0115] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes the sulfide-based compound and the positive active material, along with optionally a conductive material, a binder, etc., to the positive current collector as needed.

[0116] At this time, the sulfide-based compound may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0117] Meanwhile, the above-mentioned positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0118] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0119] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight based on the total weight of the positive active material layer.

[0120] The above anode can be manufactured according to a conventional anode manufacturing method. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing a sulfide-based compound, an anode active material, a binder, and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0121] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0122] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0123] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0124] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0125] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and optionally a binder together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0126] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, 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 βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include 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 calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0127] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0128] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer.

[0129] Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0130] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0131] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0132] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0133] In addition, the electrolytes used in the above lithium secondary battery include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. that can be used when manufacturing lithium secondary batteries, but are not limited to these.

[0134] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0135] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0136] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0137] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight percent based on the total weight of the electrolyte.

[0138] In another example, the lithium secondary battery may be a type of all-solid-state battery that does not contain an electrolyte and includes a solid electrolyte layer made of a solid electrolyte membrane.

[0139] Here, the solid electrolyte membrane may refer to a sulfide-based solid electrolyte compound, which is a type of solid-phase material capable of ion conduction, formed in a membrane-like structure.

[0140] A solid electrolyte membrane can be manufactured according to conventional methods known in the art, for example, by press-molding a powder of a sulfide-based solid electrolyte compound and then processing it into the required shape.

[0141] However, since it is difficult to maintain a membrane-like structure with sulfide-based compounds alone, solid electrolyte membranes can be manufactured by mixing a binder.

[0142] Here, the binder should preferably have excellent binding strength to the sulfide-based compound, excellent flexibility without reducing ion conductivity, and be easily peelable from the release film typically used in the manufacture of solid electrolyte membranes.

[0143] Examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0144] This type of solid electrolyte membrane can be manufactured by applying a slurry containing a sulfide-based compound, a binder, and a solvent onto a release film, and then removing the solvent.

[0145] In addition, the above solid electrolyte membrane may further include a conductive material, an auxiliary binder, etc., as needed.

[0146] Conductive materials are used to impart conductivity so that electron movement accompanying ion movement is possible, and their types are not limited as long as they possess electronic conductivity without unnecessary chemical reactions. Examples include graphite, carbon black, acetylene black, Ketjen black, furnace black, lamp black, thermo black, carbon fiber, carbon nanotube, graphene, copper, aluminum, nickel, gold, silver, conductive polymers, etc.

[0147] The content of the sulfide-based solid electrolyte compound in the above solid electrolyte membrane is 80 to 99.9 wt%, for example, 80 wt%, 80.5 wt%, 81 wt%, 81.5 wt%, 82 wt%, 82.5 wt%, 83 wt%, 83.5 wt%, 84 wt%, 84.5 wt%, 85 wt%, 85.5 wt%, 86 wt%, 86.5 wt%, 87 wt%, 87.5 wt%, 88 wt%, 88.5 wt%, 89 wt%, 89.5 wt%, 90 wt%, 90.5 wt%, 91 wt%, 91.5 wt%, 92 wt%, 92.5 wt%, 93 wt%, 93.5 wt%, 94 wt%, 94.5 wt%, 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, 98 wt%, 98.5 wt%, 99 wt%, 99.5 wt%, 99.9 wt%, or a range between two of these values, but is not limited thereto.

[0148] Here, the thickness of the solid electrolyte membrane is not limited and ranges 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, 155 µm, 160 µm, 165 µm, 170 µm, 175 It may have a range between two of these values, such as µm, 180 µm, 185 µm, 190 µm, 195 µm, 200 µm, 205 µm, 210 µm, 215 µm, 220 µm, 225 µm, 230 µm, 235 µm, 240 µm, 245 µm, 250 µm, 255 µm, 260 µm, 265 µm, 270 µm, 275 µm, 280 µm, 285 µm, 290 µm, 295 µm, 300 µm.

[0149] Meanwhile, the above-mentioned solid electrolyte membrane may have free-standing characteristics that allow it to be used without a separate support, but is not limited thereto.

[0150] The above lithium secondary battery may optionally further include an electrode assembly of the positive electrode, the negative electrode, and the separator, or a battery container housing the electrode assembly of the positive electrode, the negative electrode, and the solid electrolyte membrane, and a sealing member for sealing the battery container.

[0151] As described above, since the lithium secondary battery containing the sulfide-based compound according to the present specification exhibits excellent electrochemical properties, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0152] The external shape of the lithium secondary battery according to the present specification is not subject to any particular limitations, but may be cylindrical, prismatic, pouch, or coin-shaped using a can. In addition, the lithium secondary battery may not only be used as a battery cell for powering small devices, but may also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0153] According to another aspect of the present specification, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0154] The battery module or the battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0155]

[0156] The present invention will be described in more detail below through examples. However, these examples are intended solely to illustrate the present invention and should not be interpreted as limiting the scope of the present invention.

[0157]

[0158] Preparation Example 1. Preparation of sulfide-based compounds

[0159] Comparative Example 1

[0160] Inside a glove box (N2, H2O < 10 ppm), in a grinding container coupled to a horizontal bead mill, toluene as a solvent, and the average particle size (D 50 Li with ) 6 μm 5.5 PS 4.5 Cl 1.5A slurry formed by charging a sulfide-based compound having the composition was stirred. Here, the water content of the solvent was measured to be 19.7 ppm.

[0161] 60% by weight of 0.5 mm ZrO2 beads were added to a grinding container based on the slurry, the stirring speed was set to 6 m / s, and the pump speed was set to 2 ml / s to circulate the stirred slurry for 40 minutes and then transferred to a container.

[0162] Next, dehydration was performed inside a glove box using a vacuum filtration device (Pore size: 0.5㎛). Afterward, the dehydrated product was dried in a vacuum oven (10 torr, 100℃) for 2 hours, cooled in an N2 atmosphere (50℃), and recovered to produce a crushed sulfide-based compound.

[0163]

[0164] Comparative Example 2

[0165] A pulverized sulfide-based compound was prepared in the same manner as Comparative Example 1, except that a solvent purified by passing it through a porous microfilter (Pore size: 0.5 μm) capable of removing moisture bound to the housing was used.

[0166] Here, the water content of the solvent was measured to be 12.0 ppm.

[0167]

[0168] Comparative Example 3

[0169] A pulverized sulfide-based compound was prepared in the same manner as Comparative Example 1, except that a solvent purified by introducing a bead-shaped zeolite molecular sieve with an average diameter of 3 to 5 mm into the solvent was used.

[0170]

[0171] Examples

[0172] A pulverized sulfide-based compound was prepared in the same manner as in Comparative Example 1, except that a solvent purified by passing through the microfilter (Pore size: 0.5 μm) used in Comparative Example 2 and then introducing the molecular sieve used in Comparative Example 3 was used.

[0173] Here, the water content of the solvent was measured to be 8.0 ppm.

[0174]

[0175] Experimental Example 1. Characterization of Sulfide Compounds

[0176] The ratio of particles with a particle size of less than 1 μm, D, based on the particle size analysis results of the fine sulfide-based compound according to Preparation Example 1. 50 , D max The results were verified, and the ionic conductivity was measured and shown in Table 1 below.

[0177] Classification Comparative Example 1 Comparative Example 2 Comparative Example 3 Example <1 µm (%) 28.75 27.20 27.50 26.20 D 50 (㎛)2.152.212.122.37D max (㎛) 13.08 13.08 11.00 13.08 Ion conductivity (mS / cm) 2.5 5 2.9 0 2.3 4 3.32

[0178] According to Table 1, it can be seen that the quality of the ground product varies depending on the method of purifying the solvent during wet grinding of sulfide-based solid electrolyte compounds. For example, Comparative Example 2, in which the solvent was purified with a microfilter, showed increased ionic conductivity compared to Comparative Example 1.

[0179] Meanwhile, Comparative Example 3, in which the solvent was purified with a molecular sieve, actually showed a decrease in ionic conductivity compared to Comparative Example 1.

[0180] The example in which the solvent was purified in the order of a microfilter and a molecular sieve showed significantly improved ionic conductivity compared to Comparative Example 1.

[0181]

[0182] Preparation Example 2. Preparation of a solid electrolyte membrane and a lithium secondary battery (symmetric cell)

[0183] A pressure cell was prepared by applying a uniaxial pressure of 200 MPa to 200 mg of the sulfide-based compounds of the comparative example and the example. At this time, Li metal was inserted at both ends of the solid electrolyte to prepare a symmetric lithium secondary battery cell with a Li / sulfide-based compound / Li electrode structure.

[0184]

[0185] Experimental Example 2. Evaluation of Electrochemical Characteristics of a Lithium Secondary Battery (Symmetric Cell)

[0186] The electrochemical characteristics of the lithium secondary battery (symmetric cell) prepared in Preparation Example 2 were evaluated using Toyo's TOSCAT-3100 equipment.

[0187] To measure the critical current value for atmospheric stability evaluation, the Li plating / stripping characteristics were evaluated by gradually increasing the charge / discharge current value to determine the current value at which a cell short occurred, i.e., the critical current value, and the results are shown in Figure 1.

[0188] Here, the critical current density is 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 It was shown as (Example).

[0189] In addition, an evaluation of 300 cycles was conducted by applying a current of 0.25–0.30 mA per unit area. The electrochemical stability of the solid electrolyte was evaluated by repeating stripping and plating (1 hr each) per cycle, with 0.25 mA / cm² up to 150 cycles. 2 The current is 0.30 mA / cm² in the subsequent cycle. 2 The result was shown in Figure 1 after applying a current.

[0190] Referring to Figure 1, it can be seen that the quality of the ground product varies depending on the method of purifying the solvent during wet grinding of sulfide-based solid electrolyte compounds.

[0191] For example, Comparative Example 2, in which the solvent was purified with a microfilter, showed an increased critical current value compared to Comparative Example 1, but exhibited a similar level of electrochemical stability.

[0192] Meanwhile, in Comparative Example 3, where the solvent was purified with a molecular sieve, the critical current value increased, but electrochemical stability actually decreased due to a short circuit occurring in the symmetric cell.

[0193] In the example where the solvent was purified in the order of a microfilter and a molecular sieve, both the critical current value and electrochemical stability were improved compared to Comparative Example 1. In particular, unlike the symmetrical cell of the Comparative Example where overvoltage or a short circuit occurred, the symmetrical cell of the example showed stable results without overvoltage or a short circuit up to 600 hr.

[0194]

[0195] Although embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

Claims

1. (a) a step of preparing a sulfide-based compound comprising a crystalline phase having an argyrodite-type crystal structure; and (b) a step of wet-grinding the sulfide-based compound to obtain particles having an average particle size of 3 μm or less; comprising, The above wet grinding is performed using a solvent with a moisture content of less than 12.0 ppm, Method for manufacturing lithium ion conductive sulfide-based compounds.

2. In Paragraph 1, The crystalline phase of the above azirodite-type crystal structure is represented by the following chemical formula 1, Method for preparing lithium ion-conducting sulfide compounds: [Chemical Formula 1] Li 7-x PS 6-x X x In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br, and I, and 0≤x≤2.

3. In Paragraph 1, The wet grinding of step (b) above is performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill. Method for manufacturing lithium ion conductive sulfide-based compounds.

4. In Paragraph 1, The above solvent is a compound in which one or more alkyl groups are bonded to a benzene ring, Method for manufacturing lithium ion conductive sulfide-based compounds.

5. In Paragraph 1, The above solvent is purified by microfilters and molecular sieves, Method for manufacturing lithium ion conductive sulfide-based compounds.

6. In Paragraph 5, The above solvent is purified by microfilter and then purified by molecular sieve, Method for manufacturing lithium ion conductive sulfide-based compounds.

7. In Paragraph 5, The above microfilter has a pore size of 0.1 to 1 μm, Method for manufacturing lithium ion conductive sulfide-based compounds.

8. In Paragraph 1, The proportion of particles with a particle size of 1 μm or less among the particles obtained in step (b) above is 20 weight% or more, Method for manufacturing lithium ion conductive sulfide-based compounds.

9. In Paragraph 1, After step (b) above, (c) a step of separating particles having a particle size of 1 μm or less among the above particles; further comprising, Method for manufacturing lithium ion conductive sulfide-based compounds.

10. A lithium ion-conducting sulfide-based compound prepared according to any one of claims 1 to 9, Lithium secondary battery.

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