Lithium-ion conductive sulfide-based compound and manufacturing method therefor

Abstract

The present specification relates to a lithium-ion conductive sulfide-based compound, a manufacturing method therefor, and a lithium secondary battery comprising same. More specifically, the present specification relates to a method for controlling the particle size distribution during the pulverization of a sulfide-based solid electrolyte having an argyrodite-type crystal structure.

Description

Lithium ion conductive sulfide-based compound and method for manufacturing the same

[0001] The present specification relates to a lithium ion-conducting sulfide-based compound, a method for manufacturing the same, a cathode including the same, and a lithium secondary battery. More specifically, the present specification relates to a method for controlling the particle size of a sulfide-based compound having an azirodite-type crystal structure during grinding, and to a sulfide-based compound, a cathode, and a lithium secondary battery including the same in which it is possible to improve the particle size distribution by applying a specific process during the grinding of a sulfide-based 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] Solid electrolytes can be used to replace separators or to form anodes by mixing with cathode active materials. In particular, solid electrolytes for cathode composites must have a small average particle size.

[0009] However, sulfide-based solid electrolytes with an azirodite-type crystal structure have ductility, making it difficult to control the desired particle size during grinding, and even if the average particle size is controlled, there is a problem that the particle size distribution is not homogeneous.

[0010] Furthermore, solid electrolytes have lower ionic conductivity than liquid electrolytes and pose a problem in that they can easily degrade due to decomposition reactions within the battery. In particular, sulfide-based solid electrolytes can generate hydrogen sulfide by reacting with moisture and / or oxygen in the atmosphere. Since the grinding of sulfide-based solid electrolytes with an azirodite-type crystal structure takes a longer time, there is a problem that they can easily degrade during this process.

[0011]

[0012] According to the present specification, one objective is to provide a method for manufacturing a lithium ion-conducting sulfide compound having an azirodite-type crystal structure, which allows for more precise and easier control of the particle size of the sulfide compound.

[0013] In addition, the present specification aims to provide a solid electrolyte membrane and a lithium secondary battery using a sulfide-based solid electrolyte compound defined herein.

[0014] 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.

[0015]

[0016] According to one aspect of the present specification, (a) a step of preparing a sulfide-based compound comprising a crystalline phase having an argyrodite-type crystal structure; (b) a step of first grinding the sulfide-based compound to obtain an average particle size (D 50 A step of obtaining coarsely ground particles having a particle size of 3 μm or more; and (c) secondary grinding the coarsely ground particles to obtain an average particle size (D 50 A method for manufacturing a lithium ion conductive sulfide-based compound is provided, comprising the step of obtaining finely ground particles having a thickness of 1.5 μm or less.

[0017] In one embodiment, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0018] [Chemical Formula 1]

[0019] Li 7-x PS 6-x X x

[0020] 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.

[0021] Meanwhile, the above primary grinding 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, vibrating mill, stirring mill, disc mill, and grinding classifier mill.

[0022] In addition, the secondary grinding can be performed by a wet grinding method that grinds a slurry containing a non-protic solvent, a dispersant, and the coarsely ground particles.

[0023] In one embodiment, the secondary grinding can be performed under conditions of 15°C or lower.

[0024] Here, the secondary grinding can be performed in a system including a cooler, a bead mill, and a slurry tank.

[0025] In addition, in the secondary grinding of the above manufacturing method, the cooling water is circulated in the order of the cooler, bead mill, slurry tank, and cooler, and the temperature of the cooling water can be maintained at 5℃ or lower.

[0026] Meanwhile, the bead mill is a horizontal bead mill including a grinding vessel equipped with stirring blades, and more than 30% by weight and less than 90% by weight of beads may be fed based on the slurry fed into the bead mill.

[0027] According to another aspect of the present specification, a particulate sulfide compound comprising a crystalline phase having an argyrodite-type crystal structure, wherein the sulfide compound particles have an average particle size (D 50 ) is 1.5 μm or less, the span value expressed by Equation 1 below is 1–3.66, and the BET specific surface area is 13.02 m 2 A lithium ion conductive sulfide-based compound with a content of 1 / g or more is provided.

[0028] [Equation 1]

[0029] span = (D 90 -D 10 ) / D 50 .

[0030] In particular, the above particles have an average particle size (D 50 ) is 0.1~0.8 μm, and the ionic conductivity may be 1 mS / cm or higher.

[0031] According to another aspect of the present specification, a positive electrode is provided comprising the above-described lithium ion conductive sulfide-based compound; and a positive electrode active material.

[0032] According to another aspect of the present specification, a lithium secondary battery comprising the anode described above is provided.

[0033]

[0034] According to the present specification, the particle size distribution of an azirodite-type sulfide-based compound can be controlled more precisely, product degradation that may occur during manufacturing can be minimized, and a wide contact interface can be formed, thereby providing excellent performance as a solid electrolyte.

[0035] 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.

[0036]

[0037] FIG. 1 is the result of particle size analysis of a sulfide-based compound according to one example of the present specification;

[0038] FIG. 2 is an SEM image of a sulfide-based compound according to one example of the present specification;

[0039] FIGS. 3 and 4 are the average particle size of sulfide-based compounds according to the number of bead mill grinding cycles according to one example of the present specification.

[0040]

[0041] For convenience of understanding this specification, specific terms are defined herein. 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.

[0042]

[0043] Method for manufacturing lithium ion conductive sulfide-based compounds

[0044] 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 comprising a crystalline phase having an argyrodite-type crystal structure; (b) first grinding the sulfide-based compound to obtain an average particle size (D 50 A step of obtaining coarsely ground particles having a particle size of 3 μm or more; and (c) secondary grinding the coarsely ground particles to obtain an average particle size (D 50 It may include a step of obtaining finely ground particles having a particle size of 1.5 μm or less.

[0045] Step (a) above may be a step of synthesizing a lithium ion-conducting sulfide-based compound or preparing a compound prior to grinding.

[0046] For example, the above lithium ion conductive 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 350–500°C under an inert atmosphere, 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. Calcined at a temperature of 495℃, 500℃, or a range between two of these values, or at 350 to 650℃ in an atmosphere containing hydrogen sulfide gas, e.g., 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℃, 510℃, It may be obtained by firing at a temperature of 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.

[0047] Here, each component can be stoichiometrically calculated and mixed to have the desired composition.

[0048] The above sulfide-based solid electrolyte compound has lithium ion conductivity and can have a crystalline phase with an azirodite-type crystal structure.

[0049] 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.

[0050] 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.

[0051] However, the azirodite crystal structure has the problem of easily degrading performance due to sensitivity to air, humidity, etc. Therefore, the performance of compounds having an azirodite crystal structure can deteriorate even during the manufacturing process.

[0052] In one embodiment, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0053] [Chemical Formula 1]

[0054] Li 7-x PS 6-x X x

[0055] 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.

[0056] Here, the molar ratio Li / P of lithium (Li) and phosphorus (P) elements in the crystal phase of the azirodite-type crystal structure may be 5.00 to 6.50, 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, or a range between two of these values, but is limited thereto. It is not.

[0057] By adjusting the Li / P value, the arrangement and distribution ratio of lithium ions within the compound change, thereby preventing the phenomenon of reduced ion conductivity.

[0058] In addition, in the crystal phase of the azyrodite-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.

[0059] By adjusting the S / P value, the chemical stability and high ionic conductivity of the above compound can be secured in balance.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] In one example, if the halogen (X) element contains Cl and Br, the content of Cl may be higher than the content of Br. In such cases, the content of the Br is 0.05 to 0.5 moles based on 1 mole of the phosphorus (P) element, for example, 0.05 moles, 0.06 moles, 0.07 moles, 0.08 moles, 0.09 moles, 0.1 moles, 0.11 moles, 0.12 moles, 0.13 moles, 0.14 moles, 0.15 moles, 0.16 moles, 0.17 moles, 0.18 moles, 0.19 moles, 0.2 moles, 0.21 moles, 0.22 moles, 0.23 moles, 0.24 moles, 0.25 moles, 0.26 moles, 0.27 moles, 0.28 moles, 0.29 moles, 0.3 moles, 0.31 moles, 0.32 moles, 0.33 moles, 0.34 moles, 0.35 moles, 0.36 moles, 0.37 moles, 0.38 moles, 0.39 moles, 0.4 moles, 0.41 moles, 0.42 moles, 0.43 moles, 0.44 moles, 0.45 moles, 0.46 moles, 0.47 moles, 0.48 moles, 0.49 moles, 0.5 moles, or a range between two of these values, but is not limited thereto.

[0065] Step (b) above involves primary grinding the prepared sulfide-based compound to an average particle size (D 50 ) may be a step of obtaining coarsely ground particles of 3 μm or more.

[0066] Since the above-mentioned sulfide-based compounds having an azirodite-type crystal structure are difficult to obtain a uniform particle size through grinding, it is necessary to apply a grinding process suitable for this.

[0067] However, since such a special grinding process may have relatively sensitive process conditions, grinding efficiency can be increased by coarse grinding through a simpler form of primary grinding.

[0068] Here, the average particle size (D) of the coarsely ground particles 50) is 3 μm or more, for example, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 µm, 6.5 µm, 6.6 µm, 6.7 µm, 6.8 µm, 6.9 µm, 7 µm, 7.1 µm, 7.2 µm, 7.3 µm, 7.4 µm, 7.5 µm, 7.6 µm, 7.7 µm, 7.8 µm, 7.9 µm, 8 µm, 8.1 µm, 8.2 µm, 8.3 µm, 8.4 µm, 8.5 µm, 8.6 µm, 8.7 µm, 8.8 µm, 8.9 µm, 9 µm, 9.1 µm, 9.2 µm, 9.3 µm, 9.4 µm, 9.5 µm, 9.6 µm, 9.7 µm, 9.8 µm, 9.9 µm, It may be 10 μm or a range between two of these values.

[0069] In addition, the above primary grinding 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 vibratory mill, an atrition mill, a disk mill, and a classifier mill, but is not limited thereto.

[0070] The above step (c) involves secondary grinding of the coarsely ground sulfide-based compound to an average particle size (D 50 ) may be a step of obtaining finely ground particles with a thickness of 1.5 μm or less.

[0071] The above finely ground particles can be used for manufacturing solid electrolyte membranes that replace separators, but they may be more suitable for manufacturing a composite cathode by mixing them with a cathode active material.

[0072] Here, the secondary grinding may be performed by repeating one or more grinding processes. 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 deteriorate.

[0073] For example, the average particle size (D) of the finely ground particles. 50) is 1.5 μm or less, for example, 1.5 μm, 1.48 μm, 1.46 μm, 1.44 μm, 1.42 μm, 1.4 μm, 1.38 μm, 1.36 μm, 1.34 μm, 1.32 μm, 1.3 μm, 1.28 μm, 1.26 μm, 1.24 μm, 1.22 μm, 1.2 μm, 1.18 μm, 1.16 μm, 1.14 μm, 1.12 μm, 1.1 μm, 1.08 μm, 1.06 μm, 1.04 μm, 1.02 μm, 1 μm, 0.98 μm, 0.96 μm, 0.94 μm, 0.92 ㎛, 0.9 ㎛, 0.88 ㎛, 0.86 ㎛, 0.84 ㎛, 0.82 ㎛, 0.8 ㎛, 0.78 ㎛, 0.76 ㎛, 0.74 ㎛, 0.72 ㎛, 0.7 ㎛, 0.68 ㎛, 0.66 ㎛, 0.64 ㎛, 0.62 ㎛, 0.6 ㎛, 0.58 ㎛, 0.56 ㎛, 0.54 ㎛, 0.52 ㎛, 0.5 ㎛, 0.48 ㎛, 0.46 ㎛, 0.44 ㎛, 0.42 ㎛, 0.4 ㎛, 0.38 ㎛, 0.36 ㎛, 0.34 ㎛, 0.32 ㎛, 0.3 ㎛, It may be 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, but is not limited thereto.

[0074] 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.

[0075] Considering these characteristics, the above manufacturing method can first form coarse-ground particles that are less related to the particle size distribution of the final product through primary grinding, and then produce fine-ground particles of uniform particle size by secondary grinding.

[0076] In one example, the secondary grinding may be performed by a wet grinding method that grinds a slurry comprising a non-protic solvent, a dispersant, and the coarsely ground particles.

[0077] Using a wet grinding method can be advantageous for forming finely ground particles of relatively small size.

[0078] In addition, when performing the above secondary grinding using a wet grinding method, using an aprotic solvent can minimize the deterioration of the sulfide-based compound during grinding.

[0079] The above-mentioned aprotic solvent may include a benzene ring to which one or more alkyl groups are attached. For example, alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl groups. There are cases where one, two, or three of these alkyl groups are attached to the benzene ring, but the solvent is not limited thereto.

[0080] Meanwhile, using two or more different solvents as a non-protic solvents can increase grinding efficiency by compensating for the disadvantages of each solvent, but it is not limited to this.

[0081] In one example, the above-mentioned aprotic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, amine-based, phosphine-based solvent, etc.

[0082] For example, the above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0083] The above ester-based solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, etc.

[0084] The above ether-based solvents may include dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc., and the above ketone-based solvents may include cyclohexanone, etc.

[0085] In addition, triethylamine, triphenylamine, etc. can be used as the above amine-based solvent. Trietherphosphine, etc. can be used as the above phosphine-based solvent.

[0086] In addition, as aprotic solvents, 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-directing ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes may also be used.

[0087] Meanwhile, the above-mentioned dispersant increases the efficiency of the secondary grinding process, allowing the desired particle size to be obtained with fewer grinding processes. In addition, the above-mentioned dispersant can narrow the particle size distribution by suppressing the increase in ductility of the sulfide-based compound caused by the heat generated during the grinding process.

[0088] The above-mentioned dispersant may be used without limitation as long as it is not reactive with the above-mentioned sulfide-based compound or the above-mentioned aprotic solvent and has excellent dispersibility in the above-mentioned solvent.

[0089] For example, various substances can be used, such as alkyl sulfate esters, polyoxyethylene alkyl ethers, ethyl acetate, acetylacetone, ethyl acetoacetate, polyacrylamide, propylene glycol monomethyl ether acetate, propylene glycol methyl ether propionic acid, propylene glycol monomethyl ether, lauryl sulfoacetate, laurylamine acetate, hexyl ketone cyclohexanone, etc.

[0090] In one example, by using an acetate-based dispersant as the dispersant, the inter-particle dispersibility is improved, making it easier to form a uniform particle size distribution.

[0091] Meanwhile, the above-mentioned dispersant may be used in an amount of 1 to 10 wt% based on the above-mentioned slurry, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or a range between two of these values. However, if the content of the above-mentioned dispersant exceeds 6 wt%, it may be difficult to achieve a significant effect even when increasing the amount.

[0092] In one embodiment, the secondary 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.

[0093] By performing secondary grinding at a low temperature, the ductility of the sulfide-based compound is minimized, and as a result, the particle size distribution can be controlled more precisely.

[0094] 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.

[0095] In one example, the secondary grinding can be performed in a system including a cooler, a bead mill, and a slurry tank.

[0096] A bead mill is equipment capable of controlling particle size through collisions with small beads by introducing materials into a grinding container along with beads and grinding them. 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.

[0097] In particular, in the above secondary grinding, 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℃ or lower, for example, 5℃, 4.9℃, 4.8℃, 4.7℃, 4.6℃, 4.5℃, 4.4℃, 4.3℃, 4.2℃, 4.1℃, 4℃, 3.9℃, 3.8℃, 3.7℃, 3.6℃, ​​3.5℃, 3.4℃, 3.3℃, ​​3.2℃, 3.1℃, 3℃, 2.9℃, 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℃, It may be maintained at 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 within a range between two of these values.

[0098] 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.

[0099] The above bead mill may be equipped with a disc-type, horizontal peg-type, etc., stirring blade, but is not limited thereto. Depending on the shape of the stirring blade, aggregation may occur in the slurry or dispersibility may be improved.

[0100] Depending on the shape and characteristics of the bead mill above, the sedimentation and aggregation characteristics of the slurry may vary, and particles of low uniformity may be formed.

[0101] Meanwhile, the bead mill is a horizontal bead mill comprising a grinding vessel equipped with stirring blades, and beads are to be fed into the bead mill in a range of greater than 30 wt% and less than 90 wt%, for example, 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%, or a range between two of these values, based on the slurry fed into the bead mill. It is possible. If the beads are not sufficiently filled, grinding may be difficult, and if they are filled excessively, coarse particles may form.

[0102] 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.

[0103] Meanwhile, if the efficiency of the secondary grinding mentioned above is increased, the operating time is reduced, and not only is it possible to form finely ground particles in a shorter time, but the deterioration of the sulfide-based compound is also minimized, thereby improving quality such as ion conductivity.

[0104]

[0105] lithium ion conductive sulfide compounds

[0106] A lithium ion-conducting sulfide-based compound according to one aspect of the present specification is a particulate sulfide-based compound comprising a crystalline phase having an argyrodite-type crystal structure, wherein the sulfide-based compound particles have an average particle size (D 50 ) is 1.50 μm or less, the span value expressed by Equation 1 below is 1–3.66, and the BET specific surface area is 13.02 m 2 / g or more:

[0107] [Equation 1]

[0108] span = (D 90 -D 10 ) / D 50 .

[0109] The above lithium ion conductive sulfide-based compound may be obtained by the manufacturing method described above. Accordingly, the average particle size (D) of the above particles 50) is 1.5 μm or less, for example, 1.5 μm, 1.48 μm, 1.46 μm, 1.44 μm, 1.42 μm, 1.4 μm, 1.38 μm, 1.36 μm, 1.34 μm, 1.32 μm, 1.3 μm, 1.28 μm, 1.26 μm, 1.24 μm, 1.22 μm, 1.2 μm, 1.18 μm, 1.16 μm, 1.14 μm, 1.12 μm, 1.1 μm, 1.08 μm, 1.06 μm, 1.04 μm, 1.02 μm, 1 μm, 0.98 μm, 0.96 μm, 0.94 μm, 0.92 ㎛, 0.9 ㎛, 0.88 ㎛, 0.86 ㎛, 0.84 ㎛, 0.82 ㎛, 0.8 ㎛, 0.78 ㎛, 0.76 ㎛, 0.74 ㎛, 0.72 ㎛, 0.7 ㎛, 0.68 ㎛, 0.66 ㎛, 0.64 ㎛, 0.62 ㎛, 0.6 ㎛, 0.58 ㎛, 0.56 ㎛, 0.54 ㎛, 0.52 ㎛, 0.5 ㎛, 0.48 ㎛, 0.46 ㎛, 0.44 ㎛, 0.42 ㎛, 0.4 ㎛, 0.38 ㎛, 0.36 ㎛, 0.34 ㎛, 0.32 ㎛, 0.3 ㎛, It may be 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, but is not limited thereto.

[0110] Using a solid electrolyte with a small particle size increases the contact area with the positive electrode active material, which can lead to superior electrochemical properties.

[0111] However, average particle size (D 50 Even if the particle size is small, if the particle size is widely distributed, the performance of the anode may be degraded.

[0112] The span value represented by Equation 1 above represents the particle size distribution, and a smaller value indicates a more uniform particle size distribution.

[0113] The above sulfide-based particles have a span value of 1 to 3.66, for example, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3, 3.05, It may represent 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.66, or a range between two of these values, but is not limited thereto.

[0114] Solid electrolytes with a wide particle size distribution, i.e., a large span value, cannot achieve sufficient performance even if they are fine particles because the interface in contact with the positive active material is narrow.

[0115] On the other hand, the sulfide-based compound produced by the above-described manufacturing method has a small particle size and a small span value, so it can have excellent performance as a solid electrolyte.

[0116] The above particle has a BET specific surface area of ​​13.02 m² 2 / g or more, e.g., 13.02 m 2 / g~50 m 2 / g, 15 m 2 / g~45 m 2 / g or 15.82 m 2 / g~30 m 2 It may be / g, but is not limited to this.

[0117] In particular, the above particles have an average particle size (D 50) is 0.1~0.8 μm, and the ionic conductivity is 1 mS / cm or higher, for example, 1 mS / cm, 1.05 mS / cm, 1.1 mS / cm, 1.15 mS / cm, 1.2 mS / cm, 1.25 mS / cm, 1.3 mS / cm, 1.35 mS / cm, 1.4 mS / cm, 1.45 mS / cm, 1.5 mS / cm, 1.55 mS / cm, 1.6 mS / cm, 1.65 mS / cm, 1.7 mS / cm, 1.75 mS / cm, 1.8 mS / cm, 1.85 mS / cm, 1.9 mS / cm, 1.95 mS / cm, 2 mS / cm, 2.05 mS / cm, 2.1 mS / cm, 2.15 mS / cm, 2.2 mS / cm, 2.25 mS / cm, 2.3 mS / cm, 2.35 mS / cm, 2.4 mS / cm, 2.45 mS / cm, 2.5 mS / cm, 2.55 mS / cm, 2.6 mS / cm, 2.65 mS / cm, 2.7 mS / cm, 2.75 mS / cm, 2.8 mS / cm, 2.85 mS / cm, 2.9 mS / cm, 2.95 mS / cm, 3 mS / cm, may be within the range between two of these values ​​or greater, but is not limited thereto.

[0118]

[0119] anode

[0120] According to another aspect of the present specification, a positive electrode is provided comprising the above-described lithium ion conductive sulfide-based compound; and a positive electrode active material.

[0121] In one example, the anode may be provided to 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132]

[0133] lithium secondary battery

[0134] According to another aspect of the present specification, a lithium secondary battery comprising the anode described above may be provided.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] In addition, the above solid electrolyte membrane may further include a conductive material, an auxiliary binder, etc., as needed.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] As described above, since the lithium secondary battery including the positive electrode according to the present specification exhibits excellent electrochemical characteristics, 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).

[0168] 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.

[0169] 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.

[0170] 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.

[0171]

[0172] 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.

[0173]

[0174] Preparation Example 1. Preparation of sulfide-based compounds

[0175] Example 1

[0176] Toluene, average particle size (D) of particles in a grinding vessel coupled to a horizontal bead mill inside a glove box (N2, H2O < 10 ppm) 50 Li with ) 6 μm 5.5 PS 4.5 Cl 1.5 A slurry was formed by charging a crushed product having the composition. An acetate-based dispersant was further added to the slurry at 5% by weight relative to the slurry, and then the slurry was stirred.

[0177] 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. At this time, in order to maintain the temperature of the bead mill, cooling water was circulated from the chiller to the bead mill, from the bead mill to the tank connected to the bead mill, and from the tank back to the chiller, while maintaining the temperature of the cooling water at 3℃.

[0178] 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 fine sulfide-based compound.

[0179]

[0180] Example 2

[0181] A fine sulfide-based compound was prepared in the same manner as in Example 1, except that 2.5% by weight of an acetate-based dispersant was added based on the slurry.

[0182]

[0183] Comparative Example 1

[0184] Toluene, average particle size (D) in a grinding container coupled to a horizontal bead mill inside a glove box (N2, H2O < 10 ppm) 50 Li with ) 6 μm 5.5 PS 4.5 Cl 1.5 A slurry formed by charging a crushed product having the composition was stirred.

[0185] 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. At this time, in order to maintain the temperature of the bead mill, cooling water was circulated from the cooler to the bead mill and from the bead mill back to the cooler, and the temperature of the cooling water was maintained at 20℃.

[0186] 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 fine sulfide-based compound.

[0187]

[0188] Comparative Example 2

[0189] A fine sulfide-based compound was prepared by the same method as in Example 1, except that the cooling water was not circulated and the shape of the bead mill was changed to a vertical bead mill, but it was impossible to grind.

[0190]

[0191] Comparative Example 3

[0192] A finely ground sulfide-based compound was prepared in the same manner as in Example 1, except that the temperature of the cooling water was maintained at 3℃ and no dispersant was added, but grinding was not possible.

[0193]

[0194] Comparative Example 4

[0195] A fine sulfide-based compound was prepared by grinding in the same manner as in Example 1, except that 30% by weight of 0.5 mm ZrO2 beads were added to the grinding container based on the slurry.

[0196]

[0197] Comparative Example 5

[0198] A fine sulfide-based compound was prepared in the same manner as in Example 1, except that the horizontal bead mill connected to the grinding container was changed to a vertical bead mill.

[0199]

[0200] Comparative Example 6

[0201] A fine sulfide-based compound was prepared by grinding in the same manner as in Example 1, except that 90% by weight of 0.5 mm ZrO2 beads were added to the grinding container based on the slurry, but grinding was not possible.

[0202]

[0203] Experimental Example 1. Size Analysis of Sulfide Compounds

[0204] The particle size analysis results and BET specific surface area of ​​the fine sulfide-based compound according to Preparation Example 1 are shown in Table 1 and Figure 1 below.

[0205] In addition, SEM images were taken to confirm the particle shape of the fine sulfide-based compound prepared according to Preparation Example 1 and are shown in Fig. 2.

[0206] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 4 Comparative Example 5 D 10 ㎛0.23 0.37 0.18 0.92 0.42D 50 ㎛0.571.370.702.350.9D 90 ㎛ 1.5 7 5.38 2.88 9.24 4.2 span - 2.35 3.66 3.86 3.54 4.20 BET specific surface area m 2 / g15.8213.0212.938.6411.52

[0207] According to Table 1 and Figure 1, it can be seen that the particle distribution of fine sulfide-based compounds produced varies depending on the cooling water temperature, bead mill shape, dispersant, and bead filling rate.

[0208] Experimental Example 2. Analysis of Characteristics by Manufacturing Process

[0209] To confirm the effect according to the dispersant content, the average particle size (D) in the slurry according to the number of bead mill passes was varied in Example 1 while the dispersant content was varied. 50 ) was analyzed and shown in Figure 3.

[0210] To confirm the effect according to the cooling water temperature, the average particle size (D) in the slurry according to the number of bead mill passes in the fine sulfide-based compounds according to Example 1 and Comparative Example 1 50 ) was analyzed and shown in Figure 4.

[0211]

[0212] Experimental Example 3. Characterization of Sulfide Compounds

[0213] Each fine sulfide-based compound prepared according to Preparation Example 1, LiNi 0.8 Co 0.15 Mn 0.05 An anode sheet was prepared by mixing an O2 anode active material and a carbon nanotube conductive material in a weight ratio of 30:65:5, respectively, and then forming and pressing them into a sheet shape on a carbon-coated aluminum film with a thickness of 20 μm.

[0214] A lithium foil is used as a counter electrode for the above anode, and Li in a solvent 5.5 PS 4.5 Cl 1.5 A solid electrolyte layer prepared by mixing a solid electrolyte having a composition and a PVDF binder in a weight ratio of 99:1, then coating and drying, was interposed between the positive electrode and the counter electrode to manufacture a battery.

[0215] The discharge capacity was measured by performing charge-discharge experiments using an electrochemical analyzer at 25℃, with a voltage range of 2.0~3.65 V and a discharge rate of 0.1~1.0 C.

[0216] The ionic conductivity and discharge capacity of the fine sulfide-based compound according to Preparation Example 1 are shown in Table 2 below.

[0217] Classification Ion Conductivity (mS / cm) Initial Discharge Capacity (mAh / g) 0.33C / 0.1C Discharge Capacity Ratio 1.0C / 0.1C Discharge Capacity Ratio 0.33C 50 Cycles / 1 Cycle Discharge Capacity Ratio Example 1 2.35 199.19 3.80% 88.20% 88.20% Example 2 1.79 183.39 4.10% 86.60% 87.50% Comparative Example 11.14 174.89 3.90% 85.50% 94.30% Comparative Example 4 1.32 155.19 0.90% 80.50% 88.80% Comparative Example 50.45 146.98 9.70% 76.20% 84.80%

[0218] 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 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; (b) The above sulfide-based compound is first ground to obtain an average particle size (D 50 A step of obtaining coarsely ground particles having a thickness of 3 μm or more; and (c) The above coarsely ground particles are secondarily ground to obtain an average particle size (D 50 A step of obtaining finely ground particles having a thickness of 1.5 μm or less; comprising 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 above primary grinding 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 secondary grinding is performed by a wet grinding method that grinds a slurry comprising an aprotic solvent, a dispersant, and the above coarsely ground particles. Method for manufacturing lithium ion conductive sulfide-based compounds.

5. In Paragraph 1, The above secondary grinding is performed under conditions of 15℃ or lower, Method for manufacturing lithium ion conductive sulfide-based compounds.

6. In Paragraph 5, The above secondary grinding is performed in a system including a cooler, a bead mill, and a slurry tank, Method for manufacturing lithium ion conductive sulfide-based compounds.

7. In Paragraph 6, The cooling water circulates in the order of the cooler, bead mill, slurry tank, and cooler, and The temperature of the above cooling water is maintained at 5℃ or lower, Method for manufacturing lithium ion conductive sulfide-based compounds.

8. In Paragraph 6, The above bead mill is a horizontal bead mill comprising a grinding container equipped with stirring blades, and 35 to 90 weight percent of beads are fed into the slurry fed into the above bead mill, Method for manufacturing lithium ion conductive sulfide-based compounds.

9. Manufactured by a manufacturing method according to any one of paragraphs 1 to 8, and As a particulate sulfide compound containing a crystalline phase of an argyrodite-type crystal structure, The above sulfide-based compound particles are, Average particle size (D 50 ) is 1.5 μm or less, and The span value represented by Equation 1 below is 1 to 3.66, and BET specific surface area is 13.02 m² 2 / g or more, Lithium ion conductive sulfide compounds: [Equation 1] span = (D 90 -D 10 ) / D 50 .

10. In Paragraph 9, The above particles are, Average particle size (D 50 ) is 0.1~0.8 μm, and ionic conductivity of 1 mS / cm or higher, Lithium ion conductive sulfide-based compounds.

11. A lithium ion-conducting sulfide-based compound according to paragraph 9; and Anode active material; including, anode.

12. Including the anode according to paragraph 11, Lithium secondary battery.

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