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

Abstract

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

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 Korean Patent Application No. 10-2024-0048334 filed with the Korean Intellectual Property Office on April 9, 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, 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 lower ionic conductivity than existing commercially available liquid electrolytes. Furthermore, sulfide-based solid electrolytes react with atmospheric oxygen, carbon dioxide, and moisture when exposed to the air, reducing the ionic conductivity of the solid electrolyte. This reduced ionic conductivity can potentially degrade the performance of all-solid-state batteries using the solid electrolyte.

[0007] 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.

[0008] The present invention aims to provide a sulfide-based solid electrolyte having high ionic conductivity and atmospheric stability, a method for producing 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 7-x-y+na P 1-a M a S 6-x-y-z X z Cl x Br y

[0012] In the above chemical formula 1,

[0013] M is at least one selected from Sb, Ge, Zn, Cu, and Sn,

[0014] X is one or more selected from Se and Te,

[0015] a is 0.01 ≤ a ≤ 1,

[0016] z is 0.01 ≤ z ≤ 0.3,

[0017] 1.2 ≤ x + y ≤ 1.7,

[0018] n is n = 5-(oxidation number of M).

[0019] In addition, 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, wherein M is at least one selected from Sb, Ge, Zn, Cu, and Sn, and X is at least one selected from Se and Te.

[0020] 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.

[0021] The sulfide-based solid electrolyte according to the present invention has high ionic conductivity.

[0022] The sulfide-based solid electrolyte according to the present invention is not easily decomposed even when exposed to the atmosphere, and thus has excellent atmospheric stability.

[0023] 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 atmospheric stability.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] In this specification, element symbols are described based on the periodic table.

[0028] Sulfide-based solid electrolyte

[0029] One embodiment of the present invention provides a sulfide-based solid electrolyte represented by the chemical formula 1. The sulfide-based solid electrolyte of the present invention comprises lithium, phosphorus, and sulfur elements, and comprises two or more types of cations and two or more types of anions, and is characterized in that it necessarily comprises metal M and Se and / or Te.

[0030] 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, it is characterized by increasing atmospheric stability through cation doping (P-site substitution) and improving ionic conductivity through anion doping (S-site substitution). In addition, it is characterized by using at least one selected from Sb, Ge, Zn, Cu, and Sn as cation doping elements, and using at least one selected from Se and Te as anion doping elements. That is, among the chalcogen elements, O is not used.

[0031] Through this, the sulfide-based solid electrolyte of the present invention has high ionic conductivity for improving the operating characteristics of all-solid-state batteries and atmospheric stability for improving the manufacturing process of all-solid-state batteries. High atmospheric stability means that the sulfide-based solid electrolyte is less susceptible to moisture decomposition when exposed to air. This improves the manufacturing process of all-solid-state batteries and means that ionic conductivity can be maintained for a long time. Atmospheric stability can be expressed as moisture stability.

[0032] In one embodiment of the present invention, the sulfide-based solid electrolyte may have an argyrodite-type crystal structure. The argyrodite-type crystal structure is PS4. 3- The structure is a structure in which the main unit structure of the skeleton is used, and the sites around it are occupied by S and halogen surrounded by Li. As described above, the sulfide-based solid electrolyte of the present invention is a structure in which argyrodite (Li 7-x-y PS 6-x-y Cl x Br y ) structure, it is characterized by using at least one selected from Sb, Ge, Zn, Cu, and Sn as a cation doping element, and using at least one selected from Se and Te as an anion doping element.

[0033] When Br or Cl is introduced as a halogen element into a sulfide-based solid electrolyte, Cl - or Br - and S 2-Anion disorder can occur between the two, ensuring good ionic conductivity. Furthermore, substituting Se or Te, which have large ionic radii, at the S-site increases the lattice size. When the lattice size increases, the activation energy for lithium ion conduction decreases, thereby improving the ionic conductivity of the sulfide-based solid electrolyte. Consequently, the operating characteristics of all-solid-state batteries can be enhanced.

[0034] In addition, when one or more metal M cations are substituted for the P-site of a sulfide-based solid electrolyte, the atmospheric stability is improved by suppressing the decomposition of the sulfide-based solid electrolyte due to exposure to the atmosphere according to the Hard Soft Acids and Bases theory (HSAB). This improves the processability of the all-solid-state battery manufacturing process as described above and produces the effect of maintaining ionic conductivity for a long time.

[0035] O, like Se and Te, is a chalcogen element. However, since O has a smaller ionic radius than Se and Te, it is difficult to increase the lattice size to the level of using Se or Te when using it. In addition, O has a stronger bonding force with O than Se and Te, so the strength of the Li-O bond between O and Li increases, and Li + The mobility of the sulfide solid electrolyte may be reduced. As a result, when O is used instead of Se and Te as a chalcogen element, the ionic conductivity of the sulfide solid electrolyte may be reduced.

[0036] In addition, the doping concentration of cations and anions is also a factor affecting the ionic conductivity and atmospheric stability of the sulfide-based solid electrolyte, and the sulfide-based solid electrolyte according to the present invention has a doping concentration that satisfies a specific range.

[0037] That is, the sulfide-based solid electrolyte according to the present invention represented by the above chemical formula 1 is characterized by having a doping concentration of cations and anions that exhibits excellent ionic conductivity and atmospheric stability rather than simply double doping.

[0038] In one embodiment of the present invention, M in the chemical formula 1 may be at least one selected from Sb, Ge, Zn, Cu, and Sn, and preferably may be one selected from Sb, Ge, Zn, Cu, and Sn.

[0039] In one embodiment of the present invention, X in the chemical formula 1 may be at least one selected from Se and Te, and preferably may be Se or Te.

[0040] In one embodiment of the present invention, a in the chemical formula 1 may be 0.01 ≤ a ≤ 1, preferably 0.01 ≤ a ≤ 0.5, and more preferably 0.01 ≤ a ≤ 0.2.

[0041] In one embodiment of the present invention, x and y may be 1.2 ≤ x + y ≤ 1.7, preferably 1.2 ≤ x + y ≤ 1.6.

[0042] In one embodiment of the present invention, z in the chemical formula 1 may be 0.01 ≤ z ≤ 0.3, preferably 0.01 ≤ z ≤ 0.2.

[0043] In one embodiment of the present invention, x and y may be x > y.

[0044] In one embodiment of the present invention, x in the chemical formula 1 may be 0.3 ≤ x ≤1.6, preferably 0.4 ≤ x ≤1.6.

[0045] In one embodiment of the present invention, y in the chemical formula 1 may be 0 ≤ y ≤ 1.2, preferably 0 ≤ y ≤ 0.8.

[0046] In one embodiment of the present invention, n in the chemical formula 1 is 5-(oxidation number of M). This is to match the stoichiometry of the solid electrolyte, and na in the chemical formula 1 means a value obtained by multiplying n and a.

[0047] The oxidation number of M refers to the oxidation number of metal M. Here, the oxidation number refers to the number of charges that a specific atom of a substance would have if electron exchange were completely performed within the substance. In other words, n refers to the value obtained by subtracting the oxidation number of metal M from 5.

[0048] In one embodiment of the present invention, a, x, y and n may be 5 ≤ 7 - x - y + na ≤ 7.

[0049] When the doping concentrations of cations and anions satisfy the above conditions, the sulfide-based solid electrolyte according to the present invention exhibits excellent ionic conductivity and atmospheric stability. As a result, the sulfide-based solid electrolyte of the present invention exhibits excellent operating characteristics of all-solid-state batteries and can also improve the manufacturing processability of all-solid-state batteries.

[0050] In one embodiment of the present invention, the chemical formula 1 may be represented by the following chemical formula 2.

[0051] [Chemical Formula 2]

[0052] Li7-x-y+0.1nP 0.9 M 0.1 S 6-x-y-z X z Cl x Br y

[0053] In the above chemical formula 2,

[0054] The definitions of M, X, x, y, z and n are the same as those in the above chemical formula 1.

[0055] The sulfide-based solid electrolyte of the present invention can obtain an initial ionic conductivity of 2.0 mS / cm or more at 25°C, and also suppresses side reactions between the negative electrode of an all-solid-state battery and the solid electrolyte.

[0056] When lithium metal is used as the anode in an all-solid-state battery, the low reduction stability of the solid electrolyte leads to a side reaction in which the sulfide-based solid electrolyte is reduced by the lithium anode during charge-discharge cycles. This reaction increases interfacial resistance and reduces battery performance. Furthermore, dendrites, in which lithium grows unevenly toward the anode during charge-discharge cycles, can occur, causing battery degradation.

[0057] The sulfide-based solid electrolyte according to the present invention suppresses the above-mentioned side reaction by doping cations and anions together, thereby reducing the increase in interfacial resistance, and prevents deterioration of battery performance while maintaining high ionic conductivity by suppressing dendrites.

[0058] The sulfide-based solid electrolyte of chemical formula 1 according to the present invention has a lithium ion conductivity sufficient for the operation of a lithium battery at room temperature, i.e., 25°C, and specifically, has an initial ion conductivity of 2.0 mS / cm or more and 13.0 mS / cm or less, preferably 5.0 mS / cm or more and 12.5 mS / cm or less, and more preferably 7.0 mS / cm or more and 11.0 mS / cm or less at 25°C. The initial ion conductivity is the ion conductivity of the sulfide-based solid electrolyte after heat treatment.

[0059] The sulfide-based solid electrolyte of the present invention may have an ionic conductivity of 2.6 mS / cm to 4.5 mS / cm measured after exposure for 5 hours in a sealed container having a dew point temperature of -30°C. Specifically, the ionic conductivity of the solid electrolyte may be 2.6 mS / cm or more, 2.7 mS / cm or more, 2.9 mS / cm or more, or 3.0 mS / cm or more, and 4.5 mS / cm or less, 4.0 mS / cm or less, or 3.8 mS / cm or less. The ionic conductivity measured after exposure for 5 hours in a sealed container having a dew point temperature of -30°C may be defined as the ionic conductivity after exposure to air.

[0060] The sulfide-based solid electrolyte of the present invention may have an ionic conductivity retention rate calculated based on Equation 1 below of 26% or more, 28% or more, 30% or more, and 45% or less, 44% or less, or 43% or less after exposure for 5 hours in a sealed container having a dew point temperature of -30°C.

[0061] [Formula 1]

[0062] Ionic conductivity retention rate (%) = [Ionic conductivity after 5 hours of exposure in a sealed container at a dew point temperature of -30℃ / Initial ionic conductivity] Х 100 (%)

[0063] In other words, the sulfide-based solid electrolyte according to the present invention exhibits excellent atmospheric stability. This means that the sulfide-based solid electrolyte according to the present invention can maintain ionic conductivity for a long period of time, thereby exhibiting superior operational characteristics and enhancing the manufacturing processability of all-solid-state batteries.

[0064] Ionic conductivity values ​​vary depending on the molding pressure, diameter, thickness, and measuring 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 a sulfide-based solid electrolyte into a 13ф 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%.

[0065] <Method for producing sulfide-based solid electrolyte>

[0066] 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.

[0067] In the method for manufacturing a sulfide-based solid electrolyte according to the present invention, M may be at least one selected from Sb, Ge, Zn, Cu, and Sn, and X may be at least one selected from Se and Te.

[0068] Through this, the method for manufacturing a sulfide-based solid electrolyte according to the present invention can manufacture a sulfide-based solid electrolyte according to the present invention. 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 atmospheric stability.

[0069] In one embodiment of the present invention, the step of preparing the mixture may include the step of preparing a first mixture including a Li and S-containing compound, a P and S-containing compound, and one or more lithium halides; and the step of adding an M and X-containing compound to the first mixture to prepare a second mixture. In this case, the second mixture may refer to the mixture.

[0070] In the temporary state of the present invention, the Li and S-containing compound may be lithium sulfide (Li2S), but is not limited thereto.

[0071] In the present invention, the P and S-containing compound may be, but is not limited to, diphosphorus trisulfide (P2S3) or diphosphorus pentasulfide (P2S5).

[0072] In the temporary state of the present invention, the lithium halide may be LiCl or LiBr, but is not limited thereto.

[0073] In the temporary state of the present invention, the M may be at least one selected from Sb, Ge, Zn, Cu, and Sn, and preferably may be one selected from Sb, Ge, Zn, Cu, and Sn.

[0074] In one embodiment of the present invention, X may be at least one selected from Se and Te, and preferably may be Se or Te.

[0075] That is, in one embodiment of the present invention, the M and X-containing compound may be metal selenide or metal telluride. The M and X-containing compound may be at least one selected from Cu2Se, ZnSe, Sb2Se3, and GeTe, but is not limited thereto.

[0076] 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 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 compounds can be adjusted so as to prepare the sulfide-based solid electrolyte represented by the chemical formula 1.

[0077] 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.

[0078] 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.

[0079] In one embodiment of the present invention, the step of heat-treating the mixture can be performed after the step of pulverizing the mixture.

[0080] 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 heat-treating step under reduced pressure or a vacuum atmosphere, the residual solvent used in the step of pulverizing the mixture can be removed as much as possible, while at the same time increasing the crystallinity of the sulfide-based solid electrolyte within the structure, thereby further enhancing ionic conductivity.

[0081] 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 in a temperature range of less than 200 to 500°C, and preferably in a temperature range of 250 to 480°C.

[0082] In one embodiment of the present invention, the step of heat treating the mixture can be performed for 3 to 15 hours.

[0083] According to one embodiment of the present invention, the sulfide-based solid electrolyte can be pulverized to control the particle size. For example, the sulfide-based solid electrolyte can be pulverized to control the particle size to a level of 2.5 μm to 2.5 μm based on D50. In this case, ionic conductivity and moisture stability can be further improved. The D50 represents the median, which is the particle size value corresponding to the cumulative distribution percentage that reaches 50%.

[0084] 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.

[0085] All-solid-state battery

[0086] 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.

[0087] The sulfide-based solid electrolyte according to the present invention possesses high ionic conductivity and atmospheric stability. Accordingly, an all-solid-state battery comprising the sulfide-based solid electrolyte according to the present invention exhibits superior operating characteristics and can also improve the manufacturing processability of all-solid-state batteries. Furthermore, when lithium metal is used as the anode, side reactions between the anode and the solid electrolyte can be suppressed.

[0088] That is, the all-solid-state battery using the sulfide-based solid electrolyte according to the present invention has excellent performance.

[0089] 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.

[0090] 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.

[0091] The above-mentioned positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent. The positive electrode can be manufactured by coating a positive electrode slurry including a positive electrode active material, a binder, a conductive agent, and a solvent on a positive electrode current collector.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] The above-mentioned conductive agent is a component for further improving the conductivity of the positive electrode active material.

[0101] 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.

[0102] 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.

[0103] 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%.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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%.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] When manufacturing the all-solid-state battery of the present invention, the electrodes including the positive and negative electrodes are placed and then pressure-molded to assemble the battery.

[0117] 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.

[0118] 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).

[0119] 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.

[0120] [Example 1]

[0121] Li2S, P2S5, LiCl, LiBr, and Cu2Se as raw material powders were weighed according to the composition in Table 1 below. The raw material powders were placed in a ZrO2 container together with 30 g of 10 mm ZrO2 balls (about 6 times the total amount of precursors). Then, planetary ball milling was performed at 600 rpm for 8 hours using high-energy ball milling equipment (Fritsch, Pulverisette 7). After that, heat treatment was performed for 12 hours, and Li, a sulfide-based solid electrolyte of Example 1, was prepared. 5.9 P 0.9 Cu 0.1 S 4.45 Se 0.05 ClBr 0.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0122] [Example 2]

[0123] Li, a sulfide-based solid electrolyte of Example 2, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl and Cu2Se were weighed as raw material powders according to the composition in Table 1 below. 5.9 P 0.9 Cu 0.1 S 4.45 Se 0.05 Cl 1.5was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0124] [Example 3]

[0125] Li, a sulfide-based solid electrolyte of Example 3, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl, LiBr and ZnSe were weighed according to the composition in Table 1 below as raw material powders. 5.8 P 0.9 Zn 0.1 S 4.4 Se 0.1 ClBr 0.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0126] [Example 4]

[0127] Li, a sulfide-based solid electrolyte of Example 4, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl and ZnSe were weighed as raw material powders according to the composition in Table 1 below. 5.8 P 0.9 Zn 0.1 S 4.4 Se 0.1 Cl 1.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0128] [Example 5]

[0129] Li, a sulfide-based solid electrolyte of Example 5, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl, LiBr and Sb2Se3 were weighed as raw material powders according to the composition in Table 1 below. 5.7 P 0.9 Sb 0.1 S 4.35 Se 0.15 ClBr 0.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0130] [Example 6]

[0131] Li, a sulfide-based solid electrolyte of Example 6, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl and Sb2Se3 were weighed as raw material powders according to the composition in Table 1 below. 5.7 P 0.9 Sb 0.1 S 4.35 Se 0.15 Cl 1.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0132] [Example 7]

[0133] Li, a sulfide-based solid electrolyte of Example 7, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl, LiBr and GeTe were weighed according to the composition in Table 1 below as raw material powders. 5.8 P 0.9 Ge 0.1 S 4.35 Te 0.1 ClBr 0.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0134] [Example 8]

[0135] Li, a sulfide-based solid electrolyte of Example 8, was prepared in the same manner as Example 1, except that Li2S, P2S5, LiCl and GeTe were weighed according to the composition in Table 1 below as raw material powders. 5.8 P 0.9 Ge 0.1 S 4.35 Te 0.1 Cl 1.5 was obtained. Afterwards, the obtained electrolyte was pulverized to obtain a solid electrolyte of 3 μm in size based on D50.

[0136] [Comparative Example 1]

[0137] Li, a sulfide-based solid electrolyte of Comparative Example 1, was prepared in the same manner as Example 1, except that the content of the raw material powder was changed as shown in Table 1 below. 5.5 PS 4.5 ClBr 0.5 was manufactured.

[0138] [Comparative Example 2]

[0139] Li, a sulfide-based solid electrolyte of Comparative Example 2, was prepared in the same manner as Example 1, except that the content of the raw material powder was changed as shown in Table 1 below. 5.5 PS 4.5 Cl 1.5 was manufactured.

[0140] [Comparative Example 3]

[0141] Li, a sulfide-based solid electrolyte of Comparative Example 3, was prepared in the same manner as Example 1, except that the content of the raw material powder was changed as shown in Table 1 below. 6.6 Si 0.6 Sb 0.4 S5I1 was manufactured.

[0142] [Comparative Example 4]

[0143] Li, a sulfide-based solid electrolyte of Comparative Example 4, was prepared in the same manner as Example 1, except that the content of the raw material powder was changed as shown in Table 1 below. 5.5 PS 4.4 O 0.1 Cl 1.5 was manufactured.

[0144] [Comparative Example 5]

[0145] Li, a sulfide-based solid electrolyte of Comparative Example 5, was prepared in the same manner as Example 1, except that the content of the raw material powder was changed as shown in Table 1 below. 5.5 PS 4.4 O 0.1 ClBr 0.5 was manufactured.

[0146] Li2S(g)P2S5(g)LiCl(g)LiBr(g)Cu2Se(g)Example 11.69061.68800.71540.73280.1730Example 21.82771.82491.160200.1870Li2S(g)P2S5(g)LiCl(g)LiBr(g)ZnSe(g)Example 31.70851.70590.72300.74060.1218Example 41.84861.84591.173500.1318Li2S(g)P2S5(g)LiCl(g)LiBr(g)Sb2Se3(g)Example 51.56631.63840.69440.71120.3895Example 61.68931.76711.123400.4201Li2S(g)P2S5(g)LiCl(g)LiBr(g)GeTe(g)Example 71.69251.69000.71630.73360.1674Example 81.82991.82721.161700.1810Li2S(g)P2S5(g)LiCl(g)LiBr(g)-Comparative Example 11.58091.92930.73590.7538-Comparative Example 21.71312.09061.19620-Li2S(g)P2S5(g)LiI(g)LiBr(g)SbSi4(g)Comparative Example 31.41481.64770.83600.82500.2762Li2S(g)P2S5(g)LiCl(g)LiBr(g)Cu2O(g)Comparative Example 41.64942.01301.151800.1856Comparative Example 51.52651.86300.71060.72790.1718

[0147] [Experimental Example 1] - Initial ionic conductivity

[0148] Each of 150 mg of the sulfide-based solid electrolytes of Examples 1 to 8 and Comparative Examples 1 to 5 was placed into a SUS mold with a diameter of 13 Φ, pressurized at 370 MPa for 1 minute, maintained at 100 MPa, and AC impedance was measured in the range of 0.1 Hz to 7 MHz, and 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 (25°C) and a relative humidity of 0.7%.

[0149] The results are shown in Table 2 below.

[0150] [Experimental Example 2] - Ionic conductivity measured after exposure to air

[0151] The sulfide-based solid electrolytes of Examples 1 to 8 and Comparative Examples 1 to 5 were each exposed in a sealed container with a dew point temperature of -30°C for 5 hours. Thereafter, the ionic conductivity was measured in the same manner as the initial ionic conductivity.

[0152] The results are shown in Table 2 below.

[0153] [Experimental Example 3] - Ionic Conductivity Maintenance

[0154] The ionic conductivity retention rates of the sulfide-based solid electrolytes of Examples 1 to 8 and Comparative Examples 1 to 5 were calculated based on Equation 1 below.

[0155] [Formula 1]

[0156] Ionic conductivity retention rate (%) = [Ionic conductivity after 5 hours of exposure in a sealed container at a dew point temperature of -30℃ / Initial ionic conductivity] Х 100 (%)

[0157] The results are shown in Table 2 below.

[0158] Chemical formula Initial ionic conductivity (mS / cm) Ionic conductivity after exposure to air (mS / cm) Ionic conductivity retention rate (%) Example 1 Li 5.9 P 0.9 Cu 0.1 S 4.45 Se 0.05 ClBr 0.5 7.392.8238.2 Example 2Li 5.9 P 0.9 Cu 0.1 S 4.45 Se 0.05 Cl 1.5 8.012.6232.7 Example 3Li 5.8 P 0.9 Zn 0.1 S 4.4 Se 0.1 ClBr 0.59.33.5237.8 Example 4Li 5.8 P 0.9 Zn 0.1 S 4.4 Se 0.1 Cl 1.5 8.473.1236.8 Example 5Li 5.7 P 0.9 Sb 0.1 S 4.35 Se 0.15 ClBr 0.5 8.613.1536.6 Example 6Li 5.7 P 0.9 Sb 0.1 S 4.35 Se 0.15 Cl 1.5 7.913.2240.7 Example 7Li 5.8 P 0.9 Ge 0.1 S 4.35 Te 0.1 ClBr 0.5 8.13.1138.4 Example 8Li 5.8 P 0.9 Ge 0.1 S 4.35 Te 0.1 Cl 1.5 7.162.7738.7 Comparative Example 1Li 5.5 PS 4.5 ClBr 0.5 7.51.824 Comparative Example 2Li 5.5 PS 4.5 Cl 1.5 7.321.723.2 Comparative Example 3Li 6.6 Si 0.6 Sb 0.4 S5I16.31.523.8 Comparative Example 4Li 5.5 PS 4.4 O 0.1 Cl 1.5 5.352.1440.0 Comparison Example 5Li 5.5 PS 4.4 O 0.1 ClBr 0.5 6.072.3438.6

[0159] Looking at the results in Table 2 above, it was confirmed that the sulfide-based solid electrolytes of Examples 1 to 8 had excellent initial ionic conductivity of 7.0 mS / cm or higher, and excellent ionic conductivity of 2.6 mS / cm or higher after exposure to the atmosphere. Accordingly, it was confirmed that the sulfide-based solid electrolyte according to the present invention also had excellent ionic conductivity retention.

[0160] On the other hand, the sulfide-based solid electrolytes of Comparative Examples 1 and 2 had excellent initial ionic conductivity comparable to that of the Examples, but had ionic conductivity of less than 2.6 mS / cm, more specifically, less than 1.8 mS / cm, after exposure to the atmosphere, indicating poor performance in terms of atmospheric stability compared to the Examples. In addition, it was confirmed that the ionic conductivity retention rate was also poor compared to that of the sulfide-based solid electrolytes of the Examples.

[0161] In the case of the sulfide-based solid electrolyte of Comparative Example 3, it was confirmed that although it had a double-doped structure like the sulfide-based solid electrolyte according to the present invention, the initial ionic conductivity, the ionic conductivity after exposure to the atmosphere, and the ionic conductivity retention rate were all poor compared to the examples.

[0162] In the case of the sulfide-based solid electrolytes of Comparative Examples 4 and 5, the ionic conductivity retention rate was excellent, but the initial ionic conductivity was 5.35 mS / cm and 6.07 mS / cm, respectively, and it was confirmed that the initial ionic conductivity was not good compared to the examples.

[0163] From the results in Table 2 above, it was confirmed that the sulfide-based solid electrolyte according to the present invention not only has high ionic conductivity required to improve the operating characteristics of an all-solid-state battery, but also has excellent moisture stability to improve the processability of the all-solid-state battery manufacturing process.

[0164] That is, it can be seen that the sulfide-based solid electrolyte according to the present invention has excellent characteristics in terms of both the performance of the all-solid-state battery and the manufacturing process of the all-solid-state battery.

Claims

1. A sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li 7-x-y+na P 1-a M a S 6-x-y-z X z Cl x Br y In the above chemical formula 1, M is at least one selected from Sb, Ge, Zn, Cu, and Sn, X is one or more selected from Se and Te, a is 0.01 ≤ a ≤ 1, z is 0.01 ≤ z ≤ 0.3, 1.2 ≤ x + y ≤ 1.7, n is n = 5-(oxidation number of M).

2. In paragraph 1, The above a is a sulfide-based solid electrolyte in which 0.01 ≤ a ≤ 0.

5.

3. In paragraph 1, The above z is a sulfide-based solid electrolyte in which 0.01 ≤ z ≤ 0.

25.

4. In paragraph 1, The above x is 0.3≤ x ≤1.6, The above y is a sulfide-based solid electrolyte in which 0 ≤ y ≤ 1.

2.

5. In paragraph 1, The above chemical formula 1 is a sulfide-based solid electrolyte represented by the following chemical formula 2: [Chemical Formula 2] Li7-x-y+0.1nP 0.9 M 0.1 S 6-x-y-z X z Cl x Br y In the above chemical formula 2, The definitions of M, X, x, y, z and n are the same as those in the above chemical formula 1.

6. In paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having an ionic conductivity of 2.6 mS / cm or more measured after exposure in a sealed container at -30°C for 5 hours.

7. In paragraph 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte having an ionic conductivity retention rate of 26% or more.

8. A step of preparing a mixture comprising a Li and S-containing compound, a P and S-containing compound, one or more lithium halides, and a M and X-containing compound; a step of grinding the above mixture; and Comprising a step of heat treating the above mixture, The above M is at least one selected from Sb, Ge, Zn, Cu and Sn, A method for producing a sulfide-based solid electrolyte according to any one of claims 1 to 7, wherein X is at least one selected from Se and Te.

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 at least one lithium halide; and A method for producing a sulfide-based solid electrolyte, comprising the step of producing a second mixture by adding M and X-containing compounds 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, An all-solid-state battery, wherein the solid electrolyte layer comprises a sulfide-based solid electrolyte according to any one of claims 1 to 7.