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

Abstract

The present invention relates to a sulfide-based solid electrolyte, a method for producing same, and an all-solid-state battery comprising same.

Description

Sulfide-based solid electrolyte, method for manufacturing the same, and all-solid-state battery including the same

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

[0002] This application claims the benefit of the filing date of Korean Patent Application No. 10-2024-0133303 filed with the Korean Intellectual Property Office on September 30, 2024, the entire contents of which are incorporated herein as part.

[0003] The present invention relates to a sulfide-based solid electrolyte having high structural stability, a method for manufacturing the same, and an all-solid-state battery including the same.

[0004] All-solid-state batteries are next-generation battery systems that replace the functions of the liquid electrolyte and separator in conventional lithium-ion batteries with a solid electrolyte. Because all-solid-state batteries do not use flammable liquid electrolytes, they are safe and eliminate the risk of explosion. Furthermore, they are attracting attention as next-generation batteries due to their higher energy density compared to conventional batteries, as they allow the use of Li metal or Li alloys as the anode material.

[0005] Solid electrolytes, which are the core materials of all-solid-state batteries, can be broadly classified into polymers, sulfides, and oxides. Among these, sulfide-based solid electrolytes are considered suitable for the manufacture of large batteries due to their excellent mechanical properties, superior moldability, and high structural stability.

[0006] However, due to their low phase stability, sulfide-based solid electrolytes may experience degraded lifespan characteristics caused by adverse reactions with electrode materials during cell operation. Additionally, they present a problem where the ionic conductivity of the solid electrolyte decreases upon exposure to the atmosphere due to reactions with oxygen, carbon dioxide, and moisture. If the ionic conductivity of the solid electrolyte decreases, it may lead to performance degradation in all-solid-state batteries utilizing such electrolytes.

[0007] Therefore, for the commercialization of all-solid-state batteries using sulfide-based solid electrolytes, it is necessary to improve cell characteristics by increasing the phase stability of the sulfide-based solid electrolyte. In addition, it is necessary to ensure processability within the drying room by securing atmospheric stability.

[0008] The present invention aims to provide a sulfide-based solid electrolyte having high structural stability and atmospheric stability, a method for manufacturing the same, and an all-solid-state battery including the same.

[0009] One embodiment of the present invention provides a sulfide-based solid electrolyte represented by the following chemical formula 1.

[0010] [Chemical Formula 1]

[0011] Li a P 1-b M b S c Cl d X e

[0012] In the above chemical formula 1,

[0013] X is one or more selected from F, Br, and I, and

[0014] M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and

[0015] a is 5.0 ≤ a ≤ 7.5, and

[0016] b is 0 ≤ b ≤ 0.3, and

[0017] c is 4.0 ≤ c ≤ 5.0, and

[0018] d is 0.1 ≤ d ≤ 1.0, and

[0019] e is 0.1 ≤ e ≤ 1.0, and

[0020] The above a, d, and e satisfy 0.2 < (d+e) / a < 0.24 and 1.0 < e / d < 2.0.

[0021] In addition, one embodiment of the present invention comprises the steps of: preparing a mixture comprising a Li and S-containing compound, a P and S-containing compound, and two or more lithium halides and M-containing compounds; grinding the mixture; and heat-treating the mixture.

[0022] The above M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and

[0023] A method for manufacturing a sulfide-based solid electrolyte is provided, wherein at least one of the lithium halides is LiCl.

[0024] Finally, one embodiment of the present invention provides an all-solid-state battery comprising an anode; a cathode; and a solid electrolyte layer interposed between the anode and the cathode, wherein the solid electrolyte layer comprises a sulfide-based solid electrolyte according to the present invention.

[0025] The sulfide-based solid electrolyte according to the present invention has high structural stability.

[0026] The sulfide-based solid electrolyte according to the present invention does not decompose easily even when exposed to the atmosphere, so it has excellent atmospheric stability.

[0027] The method for manufacturing a sulfide-based solid electrolyte according to the present invention can effectively manufacture a sulfide-based solid electrolyte having high structural stability and atmospheric stability.

[0028] The present invention is described in detail below so that those skilled in the art can easily implement it. However, the present invention may be embodied in various different forms and is not limited to the configurations described herein.

[0029] Unless otherwise defined in this specification, all technical and scientific terms are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0030] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Specifically, in this specification, terms such as "comprising," "having," or "having" are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0031] In this specification, "part by weight" refers to a relative concept in which the weight of one substance is expressed as a ratio to the weight of another 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.

[0032] Meanwhile, "weight % (% by weight)" refers to an absolute concept in which the weight of a substance is expressed as a percentage of the total weight. In the mixture given as an example above, the content of substance A, substance B, and substance C is 50 weight%, 20 weight%, and 30 weight%, respectively, out of 100% of the total weight of the mixture.

[0033] In this specification, 'a to b' means a or more and b or less.

[0034] In this specification, 'a, b, c or d' means a, or b, or c, or d.

[0035] In this specification, element symbols are described based on the periodic table.

[0036] Sulfide-based solid electrolytes

[0037] One embodiment of the present invention provides a sulfide-based solid electrolyte represented by the following chemical formula 1. Specifically, the sulfide-based solid electrolyte of the present invention comprises lithium, phosphorus, and sulfur elements, and comprises two or more halogen elements, wherein the content of the halogen elements satisfies a specific range. Furthermore, at least one of the two or more halogen elements is a chlorine element (Cl).

[0038] [Chemical Formula 1]

[0039] Li a P 1-b M b S c Cl d X e

[0040] In the above chemical formula 1,

[0041] X is one or more selected from F, Br, and I, and

[0042] M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and

[0043] a is 5.0 ≤ a ≤ 7.5, and

[0044] b is 0 ≤ b ≤ 0.3, and

[0045] c is 4.0 ≤ c ≤ 5.0, and

[0046] d is 0.1 ≤ d ≤ 1.0, and

[0047] e is 0.1 ≤ e ≤ 1.0, and

[0048] The above a, d, and e satisfy 0.2 < (d+e) / a < 0.24 and 1.0 < e / d < 2.0.

[0049] That is, the sulfide-based solid electrolyte of the present invention is characterized by having an azirodite structure with a high ion conductivity composition, and additionally containing one or more halogen elements in addition to the chlorine element, and the content of the halogen element including the chlorine element satisfies the conditions of Chemical Formula 1 above.

[0050] Through this, the sulfide-based solid electrolyte of the present invention has high structural stability and atmospheric stability.

[0051] High structural stability implies excellent phase stability of the sulfide-based solid electrolyte; therefore, in the case of a cell using a sulfide-based solid electrolyte with high structural stability, adverse reactions with the electrode material during operation can be suppressed. This implies excellent battery life characteristics.

[0052] Furthermore, high atmospheric stability means that sulfide-based solid electrolytes undergo low decomposition by moisture when exposed to air. This implies that ionic conductivity can be maintained for a long time. Atmospheric stability can be described as moisture stability.

[0053] In one embodiment of the present invention, the sulfide-based solid electrolyte may have an azirodite-type crystal structure. The azirodite-type crystal structure is PS4 3- It is a structure in which the main unit structure of the framework is used, and surrounding sites are occupied by S and halogens surrounded by Li.

[0054] When one or more metal M cations are substituted at the P-sites of a sulfide-based solid electrolyte, the decomposition of the sulfide-based solid electrolyte due to exposure to the atmosphere is suppressed according to the Hard Soft Acids and Bases theory (HASB), thereby improving atmospheric stability.

[0055] In addition, when introducing halogen elements into sulfide-based solid electrolytes, the anions of the halogen elements and S 2- Good ion conductivity can be secured through the occurrence of anion disorder in the liver.

[0056] The inventors of the present invention additionally, Cl - It was confirmed that when halogen elements other than the chlorine element satisfy the conditions of Chemical Formula 1 above, the amount of moisture adsorbed upon exposure to the atmosphere is lowered, thereby increasing atmospheric stability.

[0057] In one embodiment of the present invention, X may be one or more selected from F, Br, and I. More specifically, in one embodiment of the present invention, X may be one or more selected from Br and I.

[0058] In one embodiment of the present invention, M of Formula 1 may be one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and preferably may be one selected from Sb, Ge, Zn, Cu, and Sn.

[0059] In one embodiment of the present invention, a of Formula 1 may be 5.0 ≤ a ≤ 7.5, 5.0 ≤ a ≤ 6.5, 5.0 ≤ a ≤ 6.0, or 5.0 ≤ a ≤ 5.9, and preferably 5.5 ≤ a ≤ 5.9.

[0060] In one embodiment of the present invention, b of Formula 1 may be 0 ≤ b ≤ 0.3, 0 ≤ b ≤ 0.25, or 0 ≤ b ≤ 0.2, and preferably 0 ≤ b ≤ 0.1.

[0061] In one embodiment of the present invention, c of Formula 1 may be 4.0 ≤ c ≤ 5.0, or 4.0 ≤ c ≤ 4.9, and preferably 4.5 ≤ a ≤ 4.9.

[0062] In one embodiment of the present invention, a and c may be 0.5 ≤ ac ≤ 1.5, or 0.5 ≤ ac ≤ 1.2, preferably 0.5 ≤ ac ≤ 1.0.

[0063] In one embodiment of the present invention, d of Formula 1 may be 0.1 ≤ d ≤ 1.0, or 0.3 ≤ d ≤ 0.8, preferably 0.45 ≤ d ≤ 0.6.

[0064] In one embodiment of the present invention, e of Formula 1 may be 0.1 ≤ e ≤ 1.0, or 0.3 ≤ e ≤ 0.8, preferably 0.65 ≤ e ≤ 0.8.

[0065] In one embodiment of the present invention, a, d, and e satisfy 0.2 < (d+e) / a < 0.24 and 1.0 < e / d < 2.0.

[0066] Specifically, in one embodiment of the present invention, a, d, and e may be 0.2 < (d+e) / a < 0.24, or 0.2 < (d+e) / a < 0.235, preferably 0.2 < (d+e) / a < 0.23.

[0067] In one embodiment of the present invention, a and d may be d / a > 0.05, or d / a > 0.07, preferably d / a > 0.08.

[0068] In one embodiment of the present invention, d and e may be 1.0 < e / d < 2.0, or 1.0 < e / d < 1.8, preferably 1.1 < e / d < 1.8.

[0069] In addition, in one embodiment of the present invention, d and e may be 0.35 < d / (d+e) < 0.5, or 0.36 < d / (d+e) < 0.49, preferably 0.37 < d / (d+e) < 0.48.

[0070] In one embodiment of the present invention, c, d, and e may be 0.2 < (d+e) / c < 0.3, or 0.22 < (d+e) / c < 0.3, preferably 0.24 < (d+e) / c < 0.29.

[0071] When the above numerical range is satisfied, the sulfide-based solid electrolyte of the present invention has high structural stability, a low amount of moisture adsorption upon exposure to the atmosphere, and consequently, high atmospheric stability.

[0072] In one embodiment of the present invention, the above chemical formula 1 may be represented by the following chemical formula 2.

[0073] [Chemical Formula 2]

[0074] Li a P 1-b M b S c Cl d Br e1 I e2

[0075] In the above chemical formula 2,

[0076] The definitions of M, a, b, c, and d are the same as the definitions of Chemical Formula 1 above, and

[0077] e1 and e2 satisfy 0.1 ≤ e1 ≤ 1.0 and 0 ≤ e2 ≤ 0.5, respectively, and

[0078] The above a, d, e1 and e2 satisfy 0 ≤ e1 + e2 ≤ 1, 0.2 < (d+e1+e2) / a < 0.24 and 1 < (e1+e2) / d < 2.

[0079] At this time, e1 and e2 of the above chemical formula 2 satisfy e1 + e2 = e, and the above-described condition of e can be applied.

[0080] In one embodiment of the present invention, the above chemical formula 1 can be represented by the following chemical formula 3.

[0081] [Chemical Formula 3]

[0082] Li a PS c Cl d X e

[0083] In the above chemical formula 3,

[0084] The definitions of a, c, d, and e are the same as the definitions of Chemical Formula 1 above. Being represented by Chemical Formula 3 above means that metal M is not used, and in this case, there may be advantages in terms of electrode stability.

[0085] The sulfide-based solid electrolyte of the present invention can obtain an initial ionic conductivity of 2.0 mS / cm or higher at 25°C and can also suppress side reactions occurring between the positive and / or negative electrodes of an all-solid-state battery and the solid electrolyte.

[0086] When lithium metal is used as the anode in an all-solid-state battery, side reactions occur in which the sulfide-based solid electrolyte is reduced by the lithium anode due to the low reduction stability of the solid electrolyte during charge-discharge cycles. This increases interfacial resistance and reduces battery performance. Additionally, dendrites are formed as lithium grows unevenly toward the anode during charge-discharge cycles, causing the battery to degrade.

[0087] The sulfide-based solid electrolyte according to the present invention can suppress the side reaction by doping cations and anions together, thereby lowering the increase in interfacial resistance, and by suppressing dendrites, it can maintain high ionic conductivity while preventing a decrease in battery performance.

[0088] The sulfide-based solid electrolyte of Formula 1 according to the present invention has sufficient lithium ion conductivity for the operation of a lithium battery at room temperature, i.e., 25°C. Specifically, the sulfide-based solid electrolyte may have an ion conductivity of 2.5 mS / cm or more and 13.5 mS / cm or less, preferably 3.0 mS / cm or more and 13.0 mS / cm or less, measured at 25°C in a state of induced disintegration immediately after heat treatment, more preferably 3.5 mS / cm or more and 13.0 mS / cm or less. The electrical conductivity measured in this way may have a different value from the initial ion conductivity measured in a state where the particle size is controlled so that the D50 value of the solid electrolyte measured by PSA is 2 μm to 3 μm.

[0089] In this specification, the ion conductivity measured at 25°C immediately after heat treatment in a state of induced disintegration is defined as 'ion conductivity immediately after heat treatment'. The state of induced disintegration corresponds to a state where particle size is not controlled.

[0090] The sulfide-based solid electrolyte of the present invention may have an adsorbed moisture content of 12,000 ppm to 18,000 ppm after being exposed for 5 hours in a sealed container at a dew point temperature of -30°C, wherein the D50 value measured by PSA is 2 μm to 3 μm. Specifically, the adsorbed moisture content of the solid electrolyte may be 12,500 ppm or more, or 13,000 ppm or more, and 17,500 ppm or less, or 17,000 ppm or less.

[0091] The sulfide-based solid electrolyte of the present invention may have a particle size control such that the D50 value measured by PSA is 2 μm to 3 μm, and then have an ionic conductivity measured at 25°C of 2.0 mS / cm or more and 13.0 mS / cm or less, preferably 2.5 mS / cm or more and 12.5 mS / cm or less, more preferably 3.5 mS / cm or more and 12.5 mS / cm or less.

[0092] Thus, the ionic conductivity measured at 25°C after controlling the particle size of the electrolyte so that the D50 value measured by PSA is 2 μm to 3 μm can be called the 'initial ionic conductivity,' and the initial ionic conductivity may have a slightly lower value than the ionic conductivity immediately after the heat treatment. This may have a different value from the ionic conductivity measured at 25°C in a state of disintegration induced immediately after the heat treatment.

[0093] The sulfide-based solid electrolyte of the present invention, having a D50 value of 2 μm to 3 μm measured by PSA, may have an ion conductivity retention rate calculated according to the following Equation 1, which is 40% or more, 42% or more, 44% or more, 60% or less, 59% or less, and 58% or less after being exposed for 5 hours in a sealed container at a dew point temperature of -30℃.

[0094] [Equation 1]

[0095] Ion conductivity retention rate (%) = [Ion conductivity after 5 hours of exposure in a sealed container at a dew point of -30℃ / Initial ion conductivity] × 100 (%)

[0096] In the above Equation 1, the initial ionic conductivity refers to the ionic conductivity of a sulfide-based solid electrolyte with a D50 value of 2 μm to 3 μm, measured at 25°C.

[0097] That is, the sulfide-based solid electrolyte according to the present invention has excellent atmospheric stability.

[0098] Ionic conductivity varies depending on the molding pressure, diameter, thickness, and pressurization method of the sample being measured. In the present invention, ionic conductivity is derived from the resistance value of a Nyquist plot obtained by placing 0.15 g of a sulfide-based solid electrolyte into a 13ф (mm) SUS mold, pressurizing it at 370 MPa for 1 minute, maintaining it at 100 MPa, and measuring the AC impedance in the range of 0.1 Hz to 7 MHz. At this time, all physical property measurements are performed in a drying room at room temperature and 0.7% relative humidity.

[0099] Method for manufacturing sulfide-based solid electrolytes

[0100] One embodiment of the present invention provides a method for preparing a sulfide-based solid electrolyte according to the present invention, comprising the steps of: preparing 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; grinding the mixture; and heat-treating the mixture.

[0101] The method for manufacturing a sulfide-based solid electrolyte according to the present invention is characterized in that M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and at least one of the lithium halides is LiCl, thereby enabling the manufacturing of a sulfide-based solid electrolyte according to the present invention.

[0102] That is, the method for manufacturing a sulfide-based solid electrolyte according to the present invention can produce a sulfide-based solid electrolyte having high ionic conductivity and atmospheric stability.

[0103] 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 element.

[0104] In one embodiment of the present invention, the compound containing sulfur (S) is sulfur (S8), lithium sulfide (Li -2 It may be phosphorus sulfides such as phosphorus trisulfide (P2S3) or phosphorus pentasulfide (P2S5).

[0105] In one embodiment of the present invention, the phosphorus (P)-containing compound may include, for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and phosphorus element.

[0106] In one embodiment of the present invention, the compound containing the halogen element may be LiCl, LiBr, LiI, PCl3, PCl5, PBr3, P2Cl4, SCl2, S2Cl2, etc. Preferably, it may be LiCl, LiBr, or LiI.

[0107] In one embodiment of the present invention, M may be one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga. Specifically, the compound containing the metal M may be a sulfide, bromide, or chloride of M.

[0108] One embodiment of the present invention is a step of preparing 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, which may be a step of preparing a mixture comprising a Li and S containing compound, a P and S containing compound, and two or more lithium halides and M containing compounds.

[0109] In one embodiment of the present invention, the step of preparing the mixture may include: preparing a first mixture comprising a Li and S-containing compound, a P and S-containing compound, and two or more lithium halides; and preparing a second mixture by adding an M-containing compound to the first mixture. In this case, the second compound may refer to the compound.

[0110] In the temporary state of the present invention, the Li and S-containing compound may be lithium sulfide (Li2S), but is not limited thereto.

[0111] In the temporary state of the present invention, the P and S-containing compound may be phosphorus trisulfide (P2S3) or phosphorus pentasulfide (P2S5), but is not limited thereto.

[0112] In the temporary state of the present invention, at least one of the lithium halides is LiCl, and the other lithium halides may be LiBr or LiI, but are not limited thereto.

[0113] In one embodiment of the present invention, M of Formula 1 may be one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and preferably may be one selected from Sb, Ge, Zn, Cu, and Sn.

[0114] In one embodiment of the present invention, the content ratio of the compounds used in the step of preparing the first mixture and the second mixture can be varied according to the molar ratio of the final sulfide-based solid electrolyte, and is not specifically limited in the present invention. That is, the content ratio of the compounds can be adjusted so as to produce a sulfide-based solid electrolyte represented by Chemical Formula 1.

[0115] In one embodiment of the present invention, the step of grinding the mixture may be performed as a grinding and mixing process. Specifically, the mixture may be ground and mixed while applying mechanical energy, such as a bead mill, planetary ball mill, planetary mill, mechanofusion, mortar and pestle, or 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 in the grinding and mixing is not particularly limited, and examples include alumina balls, zirconia balls, stainless steel balls, silicon nitride balls, tungsten carbide balls, etc.

[0116] Specifically, in one embodiment of the present invention, the step of grinding the mixture may be carried out using a planetary ball mill. When grinding the mixture using the planetary ball mill, the rotation speed of the planetary ball mill may be carried out at a speed of 100 rpm to 2000 rpm for 1 hour to 50 hours, but is not limited thereto. More preferably, 10 mm zirconia balls may be fed into the planetary ball mill, ground at a speed of 400 rpm to 700 rpm, and then further ground using a mortar and pestle or an auto grinder.

[0117] In one embodiment of the present invention, the step of heat-treating the mixture may be performed after the step of grinding the mixture.

[0118] In one embodiment of the present invention, the step of heat-treating the mixture 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 grinding the mixture can be removed to the maximum extent, and at the same time, the crystallinity of the sulfide-based solid electrolyte within the structure can be increased, thereby further increasing the ionic conductivity.

[0119] In one embodiment of the present invention, the step of heat-treating the mixture can be performed at a temperature of less than 500°C, preferably at a temperature range of 200°C or more and less than 500°C, preferably at a temperature range of 250°C or more and 480°C or less.

[0120] In one embodiment of the present invention, the step of heat-treating the mixture can be performed for 3 to 15 hours.

[0121] A sulfide-based solid electrolyte according to one embodiment of the present invention can be ground to control particle size suitable for a battery application layer. For example, the sulfide-based solid electrolyte can be ground 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 exhibited due to increased inter-particle contact when applied to a battery. The above D50 represents the median value and is a particle size value corresponding to the cumulative distribution percentage reaching 50%.

[0122] In addition, the description regarding the configuration of the method for manufacturing a sulfide-based solid electrolyte according to the present invention may also be applied to the sulfide-based solid electrolyte according to the present invention. The reverse is also true.

[0123] All-solid-state battery

[0124] 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 Formula 1 according to the present invention.

[0125] Specifically, the all-solid-state battery comprises a positive electrode including a positive active material, a negative electrode including a negative 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.

[0126] The sulfide-based solid electrolyte according to the present invention has high ionic conductivity and atmospheric stability. In addition, when lithium metal is applied as the cathode, side reactions between the cathode and the solid electrolyte can be suppressed.

[0127] In other words, an all-solid-state battery using a sulfide-based solid electrolyte according to the present invention has excellent performance.

[0128] 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 stacking and pressurizing so that a solid electrolyte layer exists between a positive electrode and a negative electrode. At this time, the thickness of the solid electrolyte layer can be adjusted to various thicknesses by controlling the performance of the all-solid-state battery and various process parameters, and preferably, the thickness may be 1 to 10 mm, and more preferably, 3 mm to 4 mm.

[0129] In the present invention, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0130] The above positive active material layer comprises a positive active material, a solid electrolyte, a binder, and a conductive material. The positive can be manufactured by coating a positive slurry comprising a positive active material, a binder, a conductive material, and a solvent onto a positive current collector.

[0131] 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, fine irregularities may be formed on the surface to strengthen the bonding strength of the positive active material, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0132] The above-mentioned positive 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.

[0133] 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 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 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 r3MS2)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 each atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.) etc., and any one or more of these compounds may be included.

[0134] 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 MnO2CoO2)O2, Li(Ni 0.5 Mn 0.3 CoO2)O2, Li(NiO7MnO 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 desirable in that they can improve the capacity characteristics and stability of the battery.

[0135] 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 0.8 Mn 0.1 Co 0.1 O2, etc. is more desirable in that it has an excellent improvement effect depending on the control of the type and content ratio of constituent elements forming the lithium complex metal oxide.

[0136] The above-mentioned positive active material may be included in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, based on the total weight of the solid content excluding the solvent in the positive slurry.

[0137] 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, carboxymethylcellulose, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0138] Typically, the binder may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solids excluding the solvent in the anode slurry.

[0139] The above conductive material is a component intended to further enhance the conductivity of the positive electrode active material.

[0140] The above conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, carbon-based materials such as graphite; carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or 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 may be used.

[0141] Typically, the conductive material may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solids excluding the solvent in the anode slurry.

[0142] The above solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that results in a desirable viscosity when the above positive active material and optionally a binder and a conductive material are included. For example, the solvent may be included such that the concentration of the solid component including the positive active material and optionally a binder and a conductive material is 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0143] The cathode can be manufactured, for example, by coating a cathode slurry containing a cathode active material, a binder, a conductive material, and a solvent onto a cathode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the cathode.

[0144] For example, when a negative electrode is manufactured by coating a negative electrode slurry onto the negative current collector, the negative current collector generally has a thickness of 3 μm to 500 μm. Such a 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., or aluminum-cadmium alloy may be used. In addition, similar to the positive current collector, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0145] The above-mentioned negative electrode active material may be 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), metals (Me) such as Si, SiOx, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of said metals (Me); oxides of said metals (Me) (MeOx); and composites of said 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 silicon alloy. In this case, a thin and stable SEI layer containing siloxane bonds is formed, which can further improve the high-temperature stability and lifespan characteristics of the battery.

[0146] The above-mentioned cathode active material may be included in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, based on the total weight of the solids excluding the solvent in the cathode slurry.

[0147] 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, carboxymethylcellulose, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0148] Typically, the binder may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the solids excluding the solvent in the cathode slurry.

[0149] The above conductive material is a component intended to further enhance the conductivity of the negative electrode active material. Such conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery, and examples may be used, such as graphite, such as natural graphite or synthetic graphite; carbon black, such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers, such as carbon fibers or metal fibers; metal powders, such as carbon fluoride, aluminum, or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; or conductive materials, such as polyphenylene derivatives.

[0150] The above conductive material may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, more preferably 1% to 10% by weight, based on the total weight of the solids excluding the solvent in the cathode slurry.

[0151] The above solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that results in a desirable viscosity when the above negative electrode active material and optionally a binder and a conductive material are included. For example, the solvent may be included such that the concentration of the solid component including the negative electrode active material and optionally a binder and a conductive material is 50% to 95% by weight, preferably 70% to 90% by weight.

[0152] When using the metal itself as the 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 may use an electro-deposition method or a chemical vapor deposition method.

[0153] For example, the metal thin film itself or the metal bonded / rolled / deposited on the negative 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.

[0154] The manufacturing of an all-solid-state battery having the above-described configuration is not specifically limited in the present invention, and known methods may be used.

[0155] In the manufacture of the all-solid-state battery of the present invention, electrodes including a positive electrode and a negative electrode are arranged, and then the battery is assembled by pressure molding.

[0156] The assembled battery is installed inside the outer casing and then sealed by heat pressing or the like. Laminate packs made of aluminum, stainless steel, etc., and cylindrical or prismatic metal containers are highly suitable as outer casings.

[0157] As described above, since the all-solid-state battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0158] The present invention will be explained in more detail below by way of examples. However, the scope of the present invention is not limited to these examples.

[0159] [Example 1]

[0160] Li2S, P2S5, LiCl, LiBr, and LiI were weighed as raw material powders according to the compositions in Table 1 below. The above raw material powders were placed in a ZrO2 container along with 700g of 10mm ZrO2 balls (approximately 7 times the total amount of precursors). Subsequently, using a high-energy ball milling machine (Fritsch, Pulverisette 5 Premium), milling was performed at 150 rpm for 30 minutes, followed by planetary ball milling at 500 rpm for 12 hours. Afterward, heat treatment was carried out at a temperature of 470°C for 12 hours in an Ar atmosphere to obtain a sulfide-based solid electrolyte. The obtained electrolyte was then ground to obtain the Li₂S, which is the sulfide-based solid electrolyte of Example 1 with a D50 level of 3 μm. 5.8 PS 4.8 Cl 0.5 Br 0.7 I 0.1 obtained.

[0161] [Examples 2 to 5 and Comparative Examples 1 to 5]

[0162] Sulfide-based solid electrolytes of Examples 2 to 5 and Comparative Examples 1 to 5 of Table 1 were prepared in the same manner as Example 1, except that the type and content of the raw material powder were changed as shown in Table 1 below.

[0163] Sulfide-based solid electrolyte chemical formula Li2S(g)P2S5(g)LiCl(g)LiBr(g)LiI(g) Example 1 Li 5.7 PS 4.7 Cl 0.5 Br 0.7 I 0.1 32.67836.2526.91419.8304.327 Example 2Li 5.8 PS 4.8 Cl 0.5 Br 0.7 35.16237.3127.11620.410-Example 3Li 5.7 PS 4.7 Cl 0.6 Br 0.6 I 0.133.15836.7858.41917.2474.390 Example 4Li 5.7 PS 4.7 Cl 0.6 Br 0.7 33.66937.3518.54920.431-Example 5Li 5.7 PS 4.7 Cl 0.5 Br 0.8 33.17336.8017.01923.006-Comparative Example 1Li 5.8 PS 4.76 Cl 1.24 I 0.04 37.846 40.871 19.332 -1.951 Comparative Example 2Li 5.88 PS 4.76 Cl 1.24 Br 0.12 37.14740.11618.9753.762-Comparative Example 3Li 5.92 PS 4.76 Cl 1.24 Br 0.12 I 0.04 36.44939.36218.6193.6911.879Comparative Example 4Li 6.0 PS 5.0 Cl 1.0 42.57841.56615.856--Comparative Example 5Li 5.3 PS 4.3 ClBr 0.7 27.66437.51014.30820.518-

[0164] [Experimental Example 1] - Initial Ionic Conductivity

[0165] 150 mg each of the sulfide-based solid electrolytes of Examples 1 to 5 and Comparative Examples 1 to 5 were taken and placed into a 13ф diameter SUS mold, then pressurized at 370 MPa for 1 minute, maintained at 100 MPa, and the ionic conductivity was derived from the resistance values ​​of the Nyquist plot obtained by measuring the AC impedance in the range of 0.1 Hz to 7 MHz. All measurements were performed in a dry room at room temperature (25℃) and relative humidity of 0.7%.

[0166] The results are listed in Table 2 below.

[0167] [Experimental Example 2] - Ionic conductivity retention rate

[0168] The sulfide-based solid electrolytes of Examples 1 to 5 and Comparative Examples 1 to 5 were each exposed to a sealed container at a dew point temperature of -30°C for 5 hours. Afterward, the ionic conductivity was measured in the same manner as the initial ionic conductivity was measured.

[0169] The ion conductivity retention rates of the sulfide-based solid electrolytes of Examples 1 to 5 and Comparative Examples 1 to 5 were each calculated based on Formula 1 below.

[0170] [Equation 1]

[0171] Ion conductivity retention rate (%) = [Ion conductivity after 5 hours of exposure in a sealed container at a dew point of -30℃ / Initial ion conductivity] × 100 (%)

[0172] In the above Equation 1, the initial ionic conductivity refers to the ionic conductivity of a sulfide-based solid electrolyte with a D50 value of 2 to 3 μm measured at 25°C.

[0173] The results are listed in Table 2 below.

[0174] Sulfide-based solid electrolyte chemical formula Initial ionic conductivity (mS / cm) Ionic conductivity retention rate (%) Example 1 Li 5.7 PS 4.7 Cl 0.5 Br 0.7 I 0.1 3.9356 Example 2Li 5.8 PS 4.8 Cl 0.5 Br 0.7 3.8950 Example 3Li 5.7 PS 4.7 Cl 0.6 Br 0.6 I 0.1 3.9753 Example 4Li 5.7 PS 4.7 Cl 0.6 Br 0.7 4.0547 Example 5Li 5.7 PS 4.7Cl 0.5 Br 0.8 3.9051 Comparative Example 1Li 5.8 PS 4.76 Cl 1.24 I 0.04 3.9730 Comparative Example 2Li 5.88 PS 4.76 Cl 1.24 Br 0.12 4.1025 Comparative Example 3Li 5.92 PS 4.76 Cl 1.24 Br 0.12 I 0.04 4.0832 Comparative Example 4Li 6.0 PS 5.0 Cl 1.0 2.7637 Comparative Example 5Li 5.3 PS 4.3 ClBr 0.7 3.4223

[0175] Looking at the results in Table 2 above, it was confirmed that the sulfide-based solid electrolytes of Examples 1 to 5 had excellent initial ionic conductivity of 3.0 mS / cm or higher, and an ionic conductivity retention rate of 40% or higher.

[0176] On the other hand, it was confirmed that the sulfide-based solid electrolytes of Comparative Examples 1 to 3 had excellent initial ionic conductivity comparable to that of the Examples, but had an ionic conductivity retention rate of less than 40%, and in the case of the sulfide-based solid electrolytes of Comparative Examples 4 and 5, the initial ionic conductivity was not as good as that of the Examples, and it was confirmed that the ionic conductivity retention rate was less than 40%.

[0177] That is, it was confirmed that the sulfide-based solid electrolytes of Examples 1 to 5 had excellent initial ionic conductivity and ionic conductivity retention rates.

[0178] That is, from the results of Table 2 above, it was confirmed that the sulfide-based solid electrolyte according to the present invention has high structural stability and does not decompose easily even when exposed to the atmosphere, thus having excellent atmospheric stability.

[0179] In other words, the sulfide-based solid electrolyte according to the present invention has excellent performance.

Claims

1. A sulfide-based solid electrolyte with an azirodite structure represented by the following chemical formula 1: [Chemical Formula 1] Li a P 1-b M b S c Cl d X e In the above chemical formula 1, X is one or more selected from F, Br, and I, and M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and a is 5.0 ≤ a ≤ 7.5, and b is 0 ≤ b ≤ 0.3, and c is 4.0 ≤ c ≤ 5.0, and d is 0.1 ≤ d ≤ 1.0, and e is 0.1 ≤ e ≤ 1.0, and The above a, d, and e satisfy 0.2 < (d+e) / a < 0.24 and 1.0 < e / d < 2.

0.

2. In Paragraph 1, The above a and c are sulfide-based solid electrolytes having 0.5 ≤ ac ≤ 1.

5.

3. In Paragraph 1, The above d and e are sulfide-based solid electrolytes in which 0.35 < d / (d+e) < 0.

5.

4. In Paragraph 1, The above c, d, and e are sulfide-based solid electrolytes such that 0.2 < (d+e) / c < 0.

3.

5. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having an ionic conductivity of 2.5 mS / cm or higher measured at 25°C in a state of induced disintegration immediately after heat treatment.

6. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte that has a particle size controlled so that the D50 value measured by PSA is 2 μm to 3 μm, and has an ionic conductivity of 2.0 mS / cm or higher measured at 25°C.

7. In Paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having a D50 standard particle size of 2.5 μm to 3.5 μm as measured by PSA, which has an ionic conductivity retention rate of 40% or more calculated according to the following Equation 1 after being exposed for 5 hours in a sealed container at a dew point temperature of -30℃: [Equation 1] Ion conductivity retention rate (%) = [Ion conductivity after 5 hours of exposure in a sealed container at a dew point of -30℃ / Initial ion conductivity] × 100 (%) In the above Equation 1, Initial ionic conductivity refers to the ionic conductivity of a sulfide-based solid electrolyte with a D50 value of 2 μm to 3 μm, measured at 25°C.

8. A step of preparing 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 step of grinding the above mixture; and The method includes the step of heat-treating the above mixture, The above M is one or more selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, and A method for manufacturing a sulfide-based solid electrolyte according to claim 1, wherein at least one of the lithium halides is LiCl.

9. In Paragraph 8, The step of preparing the above mixture is A step of preparing a first mixture comprising a Li and S-containing compound, a P and S-containing compound, and two or more types of lithium halides; and A method for preparing a sulfide-based solid electrolyte comprising the step of preparing a second mixture by adding an M-containing compound to the first mixture.

10. 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 above solid electrolyte layer comprises a sulfide-based solid electrolyte according to claim 1, in an all-solid-state battery.