Sulfide-based solid electrolyte, manufacturing method therefor, and all-solid-state battery comprising same

Abstract

The present invention relates to a sulfide-based solid electrolyte represented by chemical formula 1, a manufacturing method therefor, and an all-solid-state battery comprising same. [Chemical formula 1] Li7-b-c-(a×d)MaPS6-b-cClbBrc In chemical formula 1, M is at least one selected from metals satisfying expression 1, a satisfies 0.01≤a≤0.5, b satisfies 0.2≤b≤1.5, c satisfies 0.2≤c≤1.5, d denotes d in an M cation (Md+) with valence d+, b and c satisfy 0.4≤b+c≤1.5, and a, b, c, and d satisfy 5<7-b-c-(a×d)<5.6. [Expression 1] 0.2<(rM / d) / (rLi)<0.7 In expression 1, rM indicates a hexacoordinate ionic radius (Shannon radius) of the cation Md+ with valence d+, d denotes d in an M cation (Md+) with valence d+, and rLi indicates a hexacoordinate ionic radius of Li+.

Description

Sulfide-based solid electrolyte, method for producing the same, and all-solid-state battery comprising the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0121359, filed September 6, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a sulfide-based solid electrolyte having high ionic conductivity and moisture resistance, a method for producing the same, and an all-solid-state battery including the same.

[0004] All-solid-state batteries are a next-generation battery system that replaces the liquid electrolyte and separator functions of conventional lithium secondary batteries with a solid electrolyte. All-solid-state batteries are safe because they do not use flammable liquid electrolytes, eliminating the risk of explosion. Furthermore, they allow the use of lithium metal or lithium alloys as a cathode material, resulting in higher energy density than conventional batteries, making them a promising next-generation battery.

[0005] Solid electrolytes, which are the core materials of all-solid-state batteries, can be broadly classified into polymers, sulfides, and oxides. Among them, sulfide-based solid electrolytes, which have excellent mechanical properties, excellent formability, and high ionic conductivity, are considered suitable for manufacturing large-scale batteries.

[0006] However, sulfide-based solid electrolytes have the problem of reacting with atmospheric oxygen, carbon dioxide, and moisture when exposed to the atmosphere, reducing the ionic conductivity of the solid electrolyte. This reduction in ionic conductivity can potentially lead to a decline in the performance of all-solid-state batteries using the solid electrolyte.

[0007] Furthermore, the process of manufacturing sulfide-based solid electrolytes requires a dry or wet mixing step of solid raw materials with different properties. This process can lead to problems such as partial solidification of the raw materials, which reduces workability and causes uneven mixing of the raw materials. While organic solvents can act as lubricants, their complete removal before precursor firing is difficult, and any remaining solvents can carbonize, degrading electrolyte performance.

[0008] Therefore, in order to commercialize an all-solid-state battery using a sulfide-based solid electrolyte, it is necessary to secure processability in a drying room by increasing the initial ionic conductivity of the sulfide-based solid electrolyte and ensuring atmospheric stability.

[0009] The present invention aims to provide a sulfide-based solid electrolyte having high ionic conductivity and moisture resistance, a method for producing the same, and an all-solid-state battery including the same.

[0010] One embodiment of the present invention is

[0011] A sulfide-based solid electrolyte represented by the following chemical formula 1 is provided:

[0012] [Chemical Formula 1]

[0013] Li7-bc-(a×d)M a PS 6-b-c Cl b Br c

[0014] In the above chemical formula 1,

[0015] M is at least one metal selected from among metals satisfying the following formula 1,

[0016] a is 0.01 ≤ a ≤ 0.5,

[0017] b is 0.2 ≤ b ≤ 1.5,

[0018] c is 0.2 ≤ c ≤ 1.5,

[0019] d is the d of M is the cation (M d+) means d,

[0020] The above b and c satisfy 0.4 ≤ b+c ≤ 1.5,

[0021] The above a, b, c and d satisfy 5 < 7-bc-(a×d) < 5.6,

[0022] [Formula 1]

[0023] 0.2 < (r M / d) / (r Li ) < 0.7

[0024] In the above equation 1,

[0025] r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius),

[0026] d is the d of M is the cation (M d+ ) means d,

[0027] r Li is Li + is the 6-coordinate ionic radius.

[0028] In addition, the present invention provides a method for producing a sulfide-based solid electrolyte according to the present invention, comprising the steps of producing a mixture comprising a lithium (Li)-containing compound, a phosphorus (P)-containing compound, a sulfur (S)-containing compound, a halogen-containing compound, and a metal M-containing compound; a pulverizing the mixture; and a heat-treating the mixture to obtain a solid electrolyte, wherein M satisfies the above formula 1.

[0029] Finally, one embodiment of the present invention provides an all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein the solid electrolyte layer includes a sulfide-based solid electrolyte according to the present invention.

[0030] The sulfide-based solid electrolyte according to the present invention has high ionic conductivity.

[0031] The sulfide-based solid electrolyte according to the present invention has excellent moisture resistance because it does not decompose easily even when exposed to moisture.

[0032] The method for producing a sulfide-based solid electrolyte according to the present invention can effectively produce a sulfide-based solid electrolyte having high ionic conductivity and moisture resistance.

[0033] Hereinafter, the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention can be implemented in various different forms and is not limited to the configuration described herein.

[0034] Unless otherwise defined herein, all technical and scientific terms used herein are used solely to describe exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0035] When a part in this specification is said to "include" a certain component, this does not mean that other components may be included, unless otherwise specifically stated. Specifically, in this specification, terms such as "include," "have," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0036] In this specification, "part by weight" means a relative concept that expresses the weight of a substance as a ratio based on the weight of the remaining substance. For example, in a mixture containing 50 g of substance A, 20 g of substance B, and 30 g of substance C, the amounts of substance B and substance C are 40 parts by weight and 60 parts by weight, respectively, based on 100 parts by weight of substance A.

[0037] Meanwhile, "% by weight" refers to an absolute concept that expresses the weight of a certain substance as a percentage of the total weight. In the mixture in the example above, the contents of substance A, substance B, and substance C are 50% by weight, 20% by weight, and 30% by weight, respectively, out of 100% of the total weight of the mixture.

[0038] In this specification, 'a to b' means a or more and b or less.

[0039] In this specification, 'a, b, c or d' means a, or b, or c, or d.

[0040] In this specification, element symbols are described based on the periodic table.

[0041] Sulfide-based solid electrolyte

[0042] One embodiment of the present invention provides a sulfide-based solid electrolyte represented by the above chemical formula 1. The sulfide-based solid electrolyte of the present invention is characterized in that it contains lithium (Li), phosphorus (P), sulfur (S) elements, metal M, and two halogen elements, each in a specific content. In addition, the two halogen elements are characterized in that they are chlorine (Cl) and bromine (Br), respectively.

[0043] In one embodiment of the present invention, the sulfide-based solid electrolyte has an argyrodite structure. The argyrodite-type crystal structure is PS4. 3-The structure is a structure in which the main unit structure of the skeleton is occupied by S and halogen surrounded by Li at the sites around it.

[0044] That is, the sulfide-based solid electrolyte of the present invention is a high ionic conductivity composition of argyrodite (Li 7-x-y PS 6-x-y Cl x Br y ) structure, ionic conductivity and moisture resistance are improved through cation doping (Li-site substitution) and anion doping (S-site substitution).

[0045] High moisture resistance means that the sulfide-based solid electrolyte is less susceptible to moisture decomposition when exposed to air. This means that ionic conductivity can be maintained for long periods of time. Moisture resistance can also be expressed as atmospheric stability.

[0046] Specifically, argyrodite (Li 7-x-y PS 6-x-y Cl x Br y ) structure, when one or more metal M cations are substituted for the Li-site of the sulfide-based solid electrolyte, the moisture resistance is improved by suppressing the decomposition of the sulfide-based solid electrolyte due to exposure to the atmosphere. Specifically, in the argyrodite structure, the Li-site atom is surrounded by six S 2- The ion is located, and the metal M cation of Li-site is S 2- S due to moisture due to stronger interaction with ions 2- Because it can alleviate ion detachment and crystal structure destruction.

[0047] Additionally, Li depends on the ionic strength and size of the metal M cation. + It can affect the movement of ions, and when using a metal M that satisfies the above formula 1, Li +This also has the effect of increasing ionic conductivity because it results in the path of ion movement becoming shorter, the size of the location to which ions will move becoming larger, or the energy required for movement being reduced.

[0048] In addition, when using a metal M that can be substituted for a Li-site during the manufacturing process, the metal M can perform a lubricant function, thereby improving the workability of the precursor mixing process required during the solid electrolyte manufacturing process. Specifically, the sulfides, chlorides, and bromides of the metal M can perform a solid lubricant function, thereby improving the workability of the precursor mixing process.

[0049] In addition, when a halogen element is introduced into a sulfide-based solid electrolyte, the anion of the halogen element and S 2- The anion disorder phenomenon of the liver can occur, ensuring good ionic conductivity. In addition, lithium halide, a hydrolysis product of the argyrodite structure, can form a hydrate, which has the effect of controlling additional approaching water molecules to a certain extent, and the water molecules of the lithium halide hydrate present in trace amounts on the surface can be easily removed during the drying process, so it can be used to increase moisture resistance.

[0050] However, in the case of LiI among lithium halides, if a material with an LPSI-based argyrodite structure is used to utilize the same effect, I can be used in many types of organic solvents. - Since anions tend to be eluted, in the present invention, when using lithium halides, LiCl and LiBr were used.

[0051] Among them, the inventors of the present invention confirmed that when the substituted elements satisfy the conditions of the chemical formula 1, there is a more excellent effect in terms of ionic conductivity and moisture resistance.

[0052] In one embodiment of the present invention, M may be at least one selected from Mg, Ca, Cu, Zn, Al, and Ga. More specifically, in one embodiment of the present invention, M may be Mg, Ca, Cu, Zn, Al, or Ga.

[0053] In one embodiment of the present invention, a in the chemical formula 1 may be 0.01 ≤ a ≤ 0.5, 0.01 ≤ a ≤ 0.4, 0.02 ≤ a ≤ 0.3, or 0.03 ≤ a ≤ 0.2.

[0054] In one embodiment of the present invention, b in the chemical formula 1 may be 0.2 ≤ b ≤ 1.5, 0.2 ≤ b ≤ 1.4, 0.3 ≤ b ≤ 1.3, or 0.4 ≤ b ≤ 1.2.

[0055] In one embodiment of the present invention, c in the chemical formula 1 may be 0.2 ≤ c ≤ 1.5, 0.2 ≤ c ≤ 1.4, 0.3 ≤ c ≤ 1.3, or 0.4 ≤ c ≤ 1.2.

[0056] In one embodiment of the present invention, b and c may be b ≥ c or b > c.

[0057] In one embodiment of the present invention, b and c may be 0.4 ≤ b+c ≤ 1.5, 0.5 ≤ b+c ≤ 1.5, or 0.6 ≤ b+c ≤ 1.5.

[0058] Additionally, in one embodiment of the present invention, b and c may be b / (b+c) < 1, 0.1 < b / (b+c) < 0.9, 0.2 < b / (b+c) < 0.8, or 0.3 < b / (b+c) < 0.75.

[0059] In one embodiment of the present invention, d in the chemical formula 1 may be 1 ≤ d ≤ 3. The d is a cation (M d+ ) means d, for example, Cu 2+If d = 2, then Al 3+ If d = 3.

[0060] In one embodiment of the present invention, a, b, c and d may be 5 < 7-bc-(a×d) < 5.6 or 5.2 < 7-bc-(a×d) < 5.6.

[0061] In addition, in one embodiment of the present invention, a, b, c and d may be (b+c) / {7-bc-(a×d)} < 0.3, 0.2 < (b+c) / {7-bc-(a×d)} < 0.3 or 0.2 < (b+c) / {7-bc-(a×d)} < 0.29.

[0062] In one embodiment of the present invention, a, b, c and d may be (b+c) / (6-bc) ≤ 0.35, 0.25 ≤ ((b+c) / (6-bc) ≤ 0.35 or 0.28 ≤ (b+c) / {7-bc-(a×d)} ≤ 0.35.

[0063] When the above numerical range is satisfied, the sulfide-based solid electrolyte of the present invention can have high ionic conductivity and excellent moisture resistance.

[0064] As described above, the sulfide-based solid electrolyte according to the present invention can satisfy the following equation 1.

[0065] [Formula 1]

[0066] 0.2 < (r M / d) / (r Li ) < 0.7

[0067] In the above equation 1,

[0068] r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius),

[0069] d is the d of M is the cation (M d+ ) means d,

[0070] r Li is Li+ is the 6-coordinate ionic radius.

[0071] In addition, in one embodiment of the present invention, the sulfide-based solid electrolyte can satisfy the following equation 2.

[0072] [Formula 2]

[0073] 1.85 < (r M ×d) / (r Li ) < 2.65

[0074] In the above equation 2,

[0075] r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius),

[0076] d is the d of M is the cation (M d+ ) means d,

[0077] r Li is Li + is the 6-coordinate ionic radius.

[0078] In one embodiment of the present invention, the sulfide-based solid electrolyte can simultaneously satisfy Equations 1 and 2.

[0079] If the above equation 1 and / or equation 2 is satisfied, M is added to the L-site. d+ Doping is easier and the sulfide-based solid electrolyte can have higher ionic conductivity.

[0080] The sulfide-based solid electrolyte of the present invention may have a particle size of 2.5 μm to 3.5 μm based on D50. The D50 represents a median, which is a particle size value corresponding to a cumulative distribution percentage reaching 50%.

[0081] The sulfide-based solid electrolyte of the present invention can obtain an initial ionic conductivity of 5.0 mS / cm or more at 22°C and has excellent moisture resistance.

[0082] That is, in one embodiment of the present invention, the sulfide-based solid electrolyte may have an initial ionic conductivity of 5.0 mS / cm or more.

[0083] In this specification, the initial ionic conductivity means the ionic conductivity measured at 22°C in a state where the solid electrolyte obtained after heat treatment is particle-sized so that the D50 standard particle size is 2.5 μm to 3.5 μm.

[0084] The initial ionic conductivity of the sulfide-based solid electrolyte of chemical formula 1 according to the present invention may be 5.0 mS / cm or more, 5.5 mS / cm or more, or 6.0 mS / cm or more, and 13.0 mS / cm or less, or 12.5 mS / cm or less, and 5.0 mS / cm or more and 13.0 mS / cm or less, 5.0 mS / cm or more and 12.5 mS / cm or less, 5.5 mS / cm or more and 13.0 mS / cm or less, 5.5 mS / cm or more and 12.5 mS / cm or less, 6.0 mS / cm or more and 13.0 mS / cm or less, or 6.0 mS / cm or more and 12.5 mS / cm or less.

[0085] The sulfide-based solid electrolyte of the present invention can have an ionic conductivity of 3.7 mS / cm or more when exposed to a sulfide-based solid electrolyte having a particle size of 2.5 μm to 3.5 μm based on D50 measured by PSA in a container having a dew point temperature of -40°C for 5 hours.

[0086] The sulfide-based solid electrolyte of the present invention can have an ionic conductivity retention rate of 40% or more, calculated based on the following equation 3, after exposing a sulfide-based solid electrolyte having a particle size of 2.5 μm to 3.5 μm based on D50 measured by PSA to a container having a dew point temperature of -40°C for 5 hours.

[0087] [Formula 3]

[0088] Ionic conductivity retention rate (%) = [Ionic conductivity after 5 hours of exposure in a container with a dew point temperature of -40℃ / Initial ionic conductivity] × 100 (%)

[0089] For reference, the above container has a structure in which air continuously flows.

[0090] That is, the sulfide-based solid electrolyte according to the present invention has excellent moisture resistance.

[0091] Ionic conductivity values ​​vary depending on the molding pressure, diameter, thickness, and pressurization method of the measurement sample. In the present invention, the ionic conductivity is derived from the resistance value of the Nyquist plot obtained by placing 0.15 g of the sulfide-based solid electrolyte with particle size control as described above into a 13Φ(mm) SUS mold, pressurizing at 370 MPa for 1 minute, and then maintaining 100 MPa and measuring the AC impedance in the range of 0.1 Hz to 7 MHz. At this time, all physical property values ​​are measured in a drying room at room temperature and a relative humidity of 0.7%.

[0092] <Method for producing sulfide-based solid electrolyte>

[0093] One embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte according to the present invention, comprising the steps of: producing a mixture comprising a lithium (Li)-containing compound, a phosphorus (P)-containing compound, a sulfur (S)-containing compound, a halogen-containing compound, and a metal M-containing compound; pulverizing the mixture; and heat-treating the mixture to obtain a solid electrolyte.

[0094] Specifically, the method for producing a sulfide-based solid electrolyte according to the present invention is such that M satisfies the above formula 1 and / or formula 2, and a sulfide-based solid electrolyte represented by the above formula 1 can be produced.

[0095] That is, the method for manufacturing a sulfide-based solid electrolyte according to the present invention can manufacture a sulfide-based solid electrolyte having high ionic conductivity and moisture resistance.

[0096] In one embodiment of the present invention, the lithium (Li)-containing compound may be a lithium compound such as lithium sulfide (Li2S), lithium oxide (Li2O), lithium carbonate (Li2CO3), or a lithium metal monohydrate.

[0097] In one embodiment of the present invention, the compound containing sulfur (S) is sulfur (S8), lithium sulfide (Li -2 It may be a sulfide such as S), disulfide trisulfide (P2S3), or disulfide pentasulfide (P2S5).

[0098] In one embodiment of the present invention, the compound containing phosphorus (P) may include, for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and phosphorus single particles.

[0099] In one embodiment of the present invention, the compound containing the halogen element may include LiCl, LiBr, PCl3, PCl5, PBr3, P2Cl4, SCl2, S2Cl2, etc. Preferably, it may be LiCl or LiBr.

[0100] In one embodiment of the present invention, the compound containing the metal M may be at least one selected from Mg, Ca, Cu, Zn, Al, and Ga. Specifically, the compound containing the metal M may be a sulfide, bromide, or chloride of M.

[0101] More specifically, the compound containing the metal M is MgCl 2, It can be CaS, CaCl2, CuS, ZnBr2, ZnCl2, Al2S3AlBr3, AlCl3, GaCl2, GaCl3, Ga2Cl4, GaCl5, etc.

[0102] One embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, comprising the steps of: producing a mixture comprising a Li and S-containing compound, a P and S-containing compound, one or more lithium halides, and an M and X-containing compound; pulverizing the mixture; and heat-treating the mixture to obtain a solid electrolyte.

[0103] In one embodiment of the present invention, the lithium halide may be LiCl or LiBr.

[0104] In one embodiment of the present invention, the compound containing the metal M may be a compound containing M and X.

[0105] In one embodiment of the present invention, the M and X-containing compound may be a sulfide, bromide or chloride of M. As described above, the metal M of the M and X-containing compound may perform a lubricant function, thereby improving the workability of the precursor mixing process required in the solid electrolyte manufacturing process.

[0106] In the temporary state of the present invention, the Li and S-containing compound may be lithium sulfide (Li2S), but is not limited thereto.

[0107] In the present invention, the P and S-containing compound may be, but is not limited to, diphosphorus trisulfide (P2S3) or diphosphorus pentasulfide (P2S5).

[0108] The method for manufacturing a sulfide-based solid electrolyte according to the present invention is characterized in that M is at least one selected from Mg, Ca, Cu, Zn, Al, and Ga, and X is at least one selected from S, Cl, and Br, thereby manufacturing a sulfide-based solid electrolyte according to the present invention.

[0109] That is, the method for manufacturing a sulfide-based solid electrolyte according to the present invention can manufacture a sulfide-based solid electrolyte having high ionic conductivity and moisture resistance.

[0110] In one embodiment of the present invention, the content ratio of the compound used in the preparation of the first mixture can be variously adjusted depending on the molar ratio of the final sulfide-based solid electrolyte to be prepared, and is not particularly limited in the present invention. That is, the content ratio of the compound can be adjusted so as to prepare the sulfide-based solid electrolyte represented by the chemical formula 1.

[0111] In one embodiment of the present invention, the step of grinding the mixture may be performed by a grinding and mixing process. Specifically, the grinding and mixing may be performed while applying mechanical energy, such as by a bead mill, a planetary ball mill, a planetary mill, a mechanofusion mill, a mortar, or an auto grinder. If necessary, a non-polar organic solvent, such as toluene, xylene, heptane, octane, or anisole, may be added. The material of the balls used for the grinding and mixing is not particularly limited, and examples thereof include alumina balls, zirconia balls, stainless steel balls, silicon nitride balls, and tungsten carbide balls.

[0112] Specifically, in one embodiment of the present invention, the step of pulverizing the mixture may be performed using a planetary ball mill. When pulverizing the mixture using the planetary ball mill, the rotation speed of the planetary ball mill may be 100 rpm to 2000 rpm for 1 to 50 hours, but is not limited thereto. More preferably, after putting 10 mm zirconia balls into the planetary ball mill, pulverizing at a speed of 400 rpm to 700 rpm can be performed, and then further pulverizing can be performed using a mortar or auto grinder.

[0113] In one embodiment of the present invention, the step of heat-treating the mixture to obtain a solid electrolyte can be performed after the step of pulverizing the mixture.

[0114] In one embodiment of the present invention, the step of heat-treating the mixture to obtain a solid electrolyte may be performed under reduced pressure or a vacuum atmosphere. By performing the step under reduced pressure or a vacuum atmosphere, the residual solvent used in the step of pulverizing the mixture is maximally removed, while at the same time increasing the crystallinity of the sulfide-based solid electrolyte within the structure, thereby further enhancing ionic conductivity.

[0115] In one embodiment of the present invention, the step of heat-treating the mixture to obtain a solid electrolyte can be performed at a temperature range of less than 500°C, preferably less than 200 to 500°C, and preferably less than 250 to 480°C.

[0116] In one embodiment of the present invention, the step of heat-treating the mixture to obtain a solid electrolyte can be performed for 3 to 15 hours.

[0117] According to one embodiment of the present invention, the sulfide-based solid electrolyte can be pulverized to control particle size to suit the battery application layer. For example, the sulfide-based solid electrolyte can be pulverized to control particle size to a level of 0.4 μm to 3.5 μm based on D50. In this case, excellent battery performance can be achieved due to increased interparticle contact when applied to a battery.

[0118] That is, the method for manufacturing a sulfide-based solid electrolyte according to one embodiment of the present invention may further include a step of pulverizing the solid electrolyte to control the particle size to 1.5 μm to 3.5 μm based on D50.

[0119] In addition, the description regarding the composition of the method for manufacturing a sulfide-based solid electrolyte according to the present invention can also be applied to the sulfide-based solid electrolyte according to the present invention. The opposite is also true.

[0120] All-solid-state battery

[0121] In one embodiment of the present invention, an all-solid-state battery comprising a sulfide-based solid electrolyte is provided. The sulfide-based solid electrolyte may be represented by the chemical formula 1 according to the present invention. Specifically, the all-solid-state battery comprises a positive electrode comprising a positive electrode active material, a negative electrode comprising a negative electrode active material, and a solid electrolyte layer comprising a sulfide-based solid electrolyte according to the present invention, disposed between the positive electrode and the negative electrode.

[0122] The sulfide-based solid electrolyte according to the present invention possesses high ionic conductivity and atmospheric stability. Furthermore, when lithium metal is applied as the negative electrode, side reactions between the negative electrode and the solid electrolyte can be suppressed.

[0123] That is, the all-solid-state battery using the sulfide-based solid electrolyte according to the present invention has excellent performance.

[0124] The all-solid-state battery of the present invention can be manufactured according to conventional methods known in the art. For example, it can be manufactured by laminating and pressurizing a solid electrolyte layer so that it exists between the positive and negative electrodes. At this time, the solid electrolyte layer can be adjusted to various thicknesses by controlling the performance of the all-solid-state battery and various process variables. Preferably, the thickness can be 1 to 10 mm, and more preferably, it can have a thickness of 3 to 4 mm.

[0125] In the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0126] The above-mentioned positive electrode active material layer includes a positive electrode active material, a solid electrolyte, a binder, and a conductive agent. The positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive agent, and a solvent on a positive electrode current collector.

[0127] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. 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 bonding strength of the positive electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0128] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0129] More specifically, the lithium metal oxide is a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z NizO4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y 1O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 MS2)O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and one or more compounds of these may be included.

[0130] The above lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn02Co02)O2, Li(Ni 0.5 Mn 0.3 Co02)O2, Li(Ni07Mn0 15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.) are more preferable in that they can increase the capacity characteristics and stability of the battery.

[0131] The above lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co02)O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8Mn 0.1 Co 0.1 )O2, etc. is more preferable in that the improvement effect is excellent according to the control of the type and content ratio of the constituent elements forming the lithium composite metal oxide.

[0132] The above positive electrode active material may be included in an amount of 60 wt% to 99 wt%, preferably 70 wt% to 99 wt%, and more preferably 80 wt% to 98 wt%, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0133] The above binder is a component that helps bond between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0134] Typically, the binder may be included in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0135] The above-mentioned conductive agent is a component for further improving the conductivity of the positive electrode active material.

[0136] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, carbon-based materials such as graphite; carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0137] Typically, the conductive agent may be included in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of solids excluding the solvent in the positive electrode slurry.

[0138] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desirable viscosity when including the positive electrode active material and optionally a binder and a conductive material. For example, the solvent may be included so that the concentration of the solid content including the positive electrode active material and optionally a binder and a conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 95 wt%, and more preferably 70 wt% to 90 wt%.

[0139] The negative electrode can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the negative electrode.

[0140] For example, when manufacturing a negative electrode by coating a negative electrode slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change 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., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0141] The negative electrode active material may include one or more negative electrode active materials selected from the group consisting of natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxide (LTO); Si, SiOx, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe metals (Me); alloys composed of the metals (Me); oxides (MeOx) of the metals (Me); and complexes of the metals (Me) and carbon. Specifically, the negative electrode active material may be a silicon-based negative electrode active material including silicon (Si), silicon oxide (SiOx) or a silicon alloy. In this case, a thin and stable SEI layer containing a siloxane bond is formed, thereby further improving the high-temperature stability and lifespan characteristics of the battery.

[0142] The above negative electrode active material may be included in an amount of 60 wt% to 99 wt%, preferably 70 wt% to 99 wt%, and more preferably 80 wt% to 98 wt%, based on the total weight of solids excluding the solvent in the negative electrode slurry.

[0143] The above binder is a component that helps bond between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0144] Typically, the binder may be included in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of solids excluding the solvent in the slurry for the negative electrode.

[0145] The above conductive agent is a component for further improving the conductivity of the negative electrode active material. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0146] The above-mentioned conductive agent may be included in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of solids excluding the solvent in the negative electrode slurry.

[0147] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desirable viscosity when including the negative electrode active material and optionally a binder and a conductive material. For example, the solvent may be included so that the concentration of the solid content including the negative electrode active material and optionally a binder and a conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

[0148] When using the metal itself as the above-mentioned cathode, it can be manufactured by physically bonding, rolling, or depositing the metal onto the metal thin film itself or the cathode current collector. The deposition method can use an electrical deposition method or a chemical vapor deposition method.

[0149] For example, the metal to be bonded / rolled / deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0150] The manufacture of an all-solid-state battery having the above-described configuration is not particularly limited in the present invention, and a known method can be used.

[0151] When manufacturing the all-solid-state battery of the present invention, electrodes including a positive electrode and a negative electrode are placed and then pressure-molded to assemble the battery.

[0152] The assembled battery is then installed in an outer packaging material and sealed by heat pressing, etc. As the outer packaging material, a laminate pack made of aluminum, stainless steel, etc., or a cylindrical or square metal container is highly suitable.

[0153] As described above, the all-solid-state battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0154] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to these examples.

[0155] [Example 1]

[0156] Li2S, P2S5, LiCl, LiBr, and M and X-containing compounds (MX) were weighed as raw material powders according to the compositions in Table 1 below. Specifically, CaS was used as the M and X-containing compound (MX). The raw material powders were placed in a 45 ml ZrO2 container together with 30 g of 10 mm ZrO2 balls (about 6 times the total amount of the precursor). Subsequently, planetary ball milling was performed at 600 rpm for 8 hours using high-energy ball milling equipment (Fritsch, Pulverisette 5 premium). After that, heat treatment was performed at 450°C for 12 hours in an Ar atmosphere, thereby obtaining Li, a sulfide-based solid electrolyte of Example 1. 5.4 Ca 0.05 PS 4.5 Cl 1.0 Br 0.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte having a particle size of 2.16 μm based on D50.

[0157] [Examples 2 to 6 and Comparative Examples 1 to 6]

[0158] Except that the type and content of the raw material powder and the particle size D50 of the sulfide-based solid electrolyte were changed as shown in Table 1 below, the sulfide-based solid electrolytes of Examples 2 to 6 and Comparative Examples 1 to 6 of Table 1 below were manufactured in the same manner as Example 1 above.

[0159] Sulfide-based solid electrolyte chemical formula D50 (㎛) Li2S (g) P2S5 (g) LiCl (g) LiBr (g) MX Type Content (g) Example 1 Li 5.4 Ca 0.05 PS 4.5 Cl 1.0 Br 0.5 2.161.54411.91530.73060.7483CaS0.0616Example 2Li 5.3 Ca 0.1 PS 4.5 Cl 1.0 Br 0.5 2.091.49791.90690.72740.7451CaS0.1227Example 3Li 5.2 Ca 0.15 PS 4.5 Cl 1.0 Br 0.5 2.651.45211.89860.72420.7418CaS0.1832Example 4Li 5.3 Ca 0.1 PS 4.5 Cl 1.0 Br 0.5 2.771.57701.90720.58200.7452CaCl20.1886Example 5Li 5.35 Al 0.05 PS 4.5 Cl 1.0 Br 0.5 2.091.52921.92150.73300.7508Al2S30.0656Example 6Li 5.35 Ga 0.05 PS 4.5 Cl 1.0 Br 0.5 2.191.51851.90800.72780.7455Ga2S30.1001Comparative Example 1Li 5.5 PS 4.5 Cl 1.0 Br 0.5 2.011.59071.92380.73380.7517--Comparative Example 2Li 5.5 PS 4.5 Cl 1.5 2.371.72332.08421.1925---Comparative Example 3Li 5.4 Ca 0.05 PS4.5 Cl 1.5 2.641.67222.07421.1868-CaS0.0667Comparative Example 4Li 5.35 Al 0.05 PS 4.5 Cl 1.5 2.081.65652.08151.1910-Al2S30.0710Comparative Example 5Li 5.35 Ga 0.05 PS 4.5 Cl 1.5 2.341.64402.06571.1820-Ga2S30.1084Comparative Example 6Li 5.35 Ca 0.05 PS 4.5 Cl 1.0 Br 0.6 2.321.39941.88050.71730.8817CaS0.1210

[0160] In addition, the result values ​​of the following mathematical expressions 1 and 2 reflecting the six-coordinate ionic radius (Shannon radius) of the metal M used in the manufacturing process of the sulfide-based solid electrolytes of Examples 1 to 6 and Comparative Examples 1 to 6 and whether the above mathematical expressions 1 and 2 are satisfied are described in Table 2 below.

[0161] [Mathematical Formula 1]

[0162] (r M / d) / (r Li )

[0163] [Equation 2]

[0164] (r M ×d) / (r Li )

[0165] In the above mathematical expressions 1 and 2, r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius), and d is the d of M cation (M d+ ) means d, and r Li is Li + is the 6-coordinate ionic radius.

[0166] Metal M +Mathematical expression 1 result value Mathematical expression 2 result value Whether expression 1 is satisfied Whether expression 2 is satisfied Ca 2+ 0.6582.632OOCu 2+ 0.4801.921OOMg 2+ 0.4741.895OOGa 3+ 0.2722.447OOAl 3+ 0.2352.112OONa + 1.3421.342XX

[0167] [Experimental Example 1] - Initial ionic conductivity

[0168] Each of the sulfide-based solid electrolytes of Examples 1 to 6 and Comparative Examples 1 to 6 was taken in an amount of 150 mg and placed in a SUS mold with a diameter of 13 mm. Then, the mold was pressurized at 370 MPa for 1 minute, maintained at 100 MPa, and the AC impedance was measured in the range of 0.1 Hz to 7 MHz. The ionic conductivity was derived from the resistance value of the resulting Nyquist plot. All measurements were performed in a dry room at room temperature (22°C) and a relative humidity of 0.7%.

[0169] The results are shown in Table 3 below.

[0170] [Experimental Example 2] - Ionic conductivity measured after exposure to air

[0171] The sulfide-based solid electrolytes of Examples 1 to 6 and Comparative Examples 1 to 6 were each exposed to a container having a dew point temperature of -40°C for 5 hours. Thereafter, the ionic conductivity was measured in the same manner as the initial ionic conductivity.

[0172] The results are shown in Table 3 below.

[0173] [Experimental Example 3] - Ionic Conductivity Maintenance

[0174] The ionic conductivity retention rates of the sulfide-based solid electrolytes of Examples 1 to 6 and Comparative Examples 1 to 6 were calculated based on Equation 3 below.

[0175] [Formula 3]

[0176] Ionic conductivity retention rate (%) = [Ionic conductivity after 5 hours of exposure in a container with a dew point temperature of -40℃ / Initial ionic conductivity] × 100 (%)

[0177] The results are shown in Table 3 below.

[0178] Sulfide-based solid electrolyte chemical formula Initial ionic conductivity (mS / cm) Ionic conductivity after exposure to air (mS / cm) Ionic conductivity retention (%) Example 1 Li 5.4 Ca 0.05 PS 4.5 Cl 1.0 Br 0.5 9.833.9640.3 Example 2Li 5.3 Ca 0.1 PS 4.5 Cl 1.0 Br 0.5 9.914.4344.7 Example 3Li 5.2 Ca 0.15 PS 4.5 Cl 1.0 Br 0.5 9.624.4045.7 Example 4Li 5.3 Ca 0.1 PS 4.5 Cl 1.0 Br 0.5 9.824.4144.9 Example 5Li 5.35 Al 0.05 PS 4.5 Cl 1.0 Br 0.5 8.084.3854.3 Example 6Li 5.35 Ga 0.05 PS 4.5 Cl 1.0 Br 0.5 9.094.2947.1 Comparative Example 1Li 5.5 PS 4.5 Cl 1.0 Br 0.5 9.043.5038.7 Comparative Example 2Li 5.5 PS 4.5 Cl 1.5 7.422.9139.2 Comparative Example 3Li 5.4 Ca 0.05 PS 4.5 Cl 1.57.363.2544.2 Comparative Example 4Li 5.35 Al 0.05 PS 4.5 Cl 1.5 7.123.4247.9 Comparative Example 5Li 5.35 Ga 0.05 PS 4.5 Cl 1.5 7.903.1640.0 Comparison Example 6Li 5.35 Ca 0.05 PS 4.5 Cl 1.0 Br 0.6 9.683.6938.2

[0179] As can be confirmed from the results in Table 3 above, the sulfide-based solid electrolytes of Examples 1 to 6 all have an initial ionic conductivity of 8.0 mS / cm or more, and the ionic conductivity retention rate after exposure to the atmosphere is 40% or more, so they also have excellent moisture resistance.

[0180] On the other hand, the sulfide-based solid electrolyte of Comparative Example 1 has a high initial ionic conductivity, but the ionic conductivity retention rate after exposure to the atmosphere is 38.7%, which is less than 40%, and thus has poor moisture resistance.

[0181] The sulfide-based solid electrolytes of Comparative Examples 2 to 5 have poor performance, with an initial ionic conductivity of less than 8.0 mS / cm, and the sulfide-based solid electrolyte of Comparative Example 2 has poor moisture resistance, with an ionic conductivity retention rate of 39.2%, which is less than 40% after exposure to the atmosphere.

[0182] The sulfide-based solid electrolyte of Comparative Example 6 also has a high initial ionic conductivity of 9.68 mS / cm, but the ionic conductivity retention rate after exposure to the atmosphere is 38.2%, which is less than 40%, so the moisture resistance is poor.

[0183] Through this, it was confirmed that the sulfide-based solid electrolyte according to the present invention has high ionic conductivity and excellent moisture resistance as it does not decompose easily even when exposed to moisture. In other words, the performance of the all-solid-state battery using the sulfide-based solid electrolyte according to the present invention is also excellent.

Claims

1. A sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li7-b-c-(a×d)M a PS 6-b-c Cl b Br c In the above chemical formula 1, M is at least one metal selected from among metals satisfying the following formula 1, a is 0.01 ≤ a ≤ 0.5, b is 0.2 ≤ b ≤ 1.5, c is 0.2 ≤ c ≤ 1.5, d is the d of M is the cation (M d+ ) means d, The above b and c satisfy 0.4 ≤ b+c ≤ 1.5, The above a, b, c and d satisfy 5 < 7-bc-(a×d) < 5.6, [Formula 1] 0.2 < (r M / d) / (r Li ) < 0.7 In the above equation 1, r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius), d is the d of M is the cation (M d+ ) means d, r Li is Li + is the 6-coordinate ionic radius.

2. In paragraph 1, The above sulfide-based solid electrolyte satisfies the following equation 2: Sulfide-based solid electrolyte: [Formula 2] 1.85 < (r M ×d) / (r Li ) < 2.65 In the above equation 2, r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius), d is the d of M is the cation (M d+ ) means d, r Li is Li + is the 6-coordinate ionic radius.

3. In paragraph 1, The above M is at least one selected from Mg, Ca, Cu, Zn, Al and Ga. Sulfide-based solid electrolyte.

4. In paragraph 1, The above a, b, c and d are (b+c) / {7-bc-(a×d)} < 0.3, Sulfide-based solid electrolyte.

5. In paragraph 1, The above a, b, c and d are (b+c) / (6-bc) ≤ 0.35, Sulfide-based solid electrolyte.

6. In paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having an initial ionic conductivity of 5.0 mS / cm or more.

7. In paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having a particle size of 2.5 μm to 3.5 μm based on D50 measured by PSA, which is exposed to a container with a dew point temperature of -40°C for 5 hours, and has an ionic conductivity of 3.7 mS / cm or more.

8. In paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having a particle size of 2.5 μm to 3.5 μm based on D50 measured by PSA, which is exposed to a container with a dew point temperature of -40°C for 5 hours, and has an ionic conductivity retention rate of 40% or more calculated based on the following equation 3: [Formula 3] Ionic conductivity retention rate (%) = [Ionic conductivity after 5 hours of exposure in a container with a dew point temperature of -40℃ / Initial ionic conductivity] × 100 (%) .

9. A step of preparing a mixture comprising a compound containing lithium (Li), a compound containing phosphorus (P), a compound containing sulfur (S), a compound containing halogen, and a compound containing metal M; a step of grinding the above mixture; and Comprising a step of heat-treating the above mixture to obtain a solid electrolyte, The above M is a method for manufacturing a sulfide-based solid electrolyte according to claim 1, which satisfies the following formula 1: [Formula 1] 0.2 < (r M / d) / (r Li ) < 0.7 In the above equation 1, r M Silver d is a cation M d+ is the six-coordinate ionic radius (Shannon radius), d is the d of M is the cation (M d+ ) means d, r Li is Li + is the 6-coordinate ionic radius.

10. In paragraph 9, The compound containing the above metal M is a compound containing M and X, The above M and X containing compounds are sulfides, bromides or chlorides of M, Method for producing a sulfide-based solid electrolyte.

11. In paragraph 9, Further comprising a step of crushing the solid electrolyte to control the particle size to 1.5 μm to 3.5 μm based on D50. Method for producing a sulfide-based solid electrolyte.

12. An all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer interposed between the positive electrode and the negative electrode, The solid electrolyte layer comprises a sulfide-based solid electrolyte according to any one of claims 1 to 8. All-solid-state battery.