Composite solid electrolytes and all-solid-state batteries containing them

Abstract

The present invention is an invention aimed at improving the air stability of conventional sulfide-based solid electrolytes, and includes sulfide-based solid electrolyte particles and a polymer coating layer formed on the sulfide-based solid electrolyte particles. The polymer coating layer contains a composite solid electrolyte containing a polymer having a Mooney viscosity (ML1+4, 100 °C) of 30 or more and 110 or less, and a all-solid-state battery including the same.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0082075 dated July 4, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a sulfide-based composite solid electrolyte with improved atmospheric stability and chemical resistance, and to an all-solid-state battery containing the same. [Background technology]

[0003] All-solid-state batteries are batteries in which the liquid electrolyte filling the space between the positive and negative electrodes of conventional lithium secondary batteries has been replaced with a solid. They are safe as they do not pose a risk of explosion, and they have a higher energy density than conventional batteries, making them a focus of attention as next-generation batteries. The solid electrolyte used in all-solid-state batteries is a solid-state material that allows lithium ions to conduct within the battery, and it has a high level of ionic conductivity, comparable to the electrolytes currently used in lithium secondary batteries. Core materials that make up the solid electrolyte include polymers, sulfides, and oxides, but among these, sulfide-based solid electrolytes, which have high flexibility and high ionic conductivity, are considered suitable for the manufacture of large-capacity batteries.

[0004] However, sulfide-based solid electrolytes have a high reactivity to moisture, which means they react not only with moisture in the air but also with moisture under low humidity conditions, generating the harmful gas hydrogen sulfide (H2S). This not only negatively affects the safety of workers due to the toxic hydrogen sulfide, but also degrades the performance of the sulfide-based solid electrolyte itself.

[0005] Therefore, there is a need to develop sulfide-based solid electrolytes that exhibit excellent atmospheric stability and chemical resistance. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] An object of the present invention is to provide a composite solid electrolyte with improved atmospheric stability and chemical resistance.

[0007] However, the problem to be solved by the present invention is not limited to the problem mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

Means for Solving the Problem

[0008] In order to solve the above problems, the present invention provides a composite solid electrolyte and an all-solid-state battery.

[0009] (1) The present invention provides a composite solid electrolyte comprising sulfide-based solid electrolyte particles and a polymer coating layer formed on the sulfide-based solid electrolyte particles, wherein the polymer coating layer comprises a polymer having a Mooney Viscosity (ML1+4, 100°C) of 30 or more and 110 or less.

[0010] (2) The present invention provides the composite solid electrolyte according to (1) above, wherein the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0011] (3) The present invention provides the composite solid electrolyte according to (1) or (2) above, wherein the polymer in the polymer coating layer is at least one selected from the group consisting of a polymer of an acrylonitrile monomer and a butadiene monomer, a hydride thereof, and a polymer of a styrene monomer and a butadiene monomer.

[0012] (4) The present invention provides the composite solid electrolyte according to any one of (1) to (3) above, wherein the polymer in the polymer coating layer comprises a repeating unit represented by the following Chemical Formula 1 and a repeating unit represented by the following Chemical Formula 2.

[0013]

Chemical Formula

[0014] (5) The present invention provides a composite solid electrolyte in any one of (1) to (4) above, wherein the polymer in the polymer coating layer contains 15% to 50% by weight of repeating units derived from acrylonitrile monomers, relative to the total weight of the polymer.

[0015] (6) The present invention provides a composite solid electrolyte in which, in any one of (1) to (5) above, the polymer of the polymer coating layer contains 50% to 85% by weight of repeating units derived from butadiene monomers, relative to the total weight of the polymer.

[0016] (7) The present invention provides a composite solid electrolyte in which, in any one of (1) to (6) above, the polymer coating layer is contained in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the sulfide-based solid electrolyte particles.

[0017] (8) The present invention provides a composite solid electrolyte having an ionic conductivity of 0.001 mS / cm to 20 mS / cm in any one of (1) to (7) above.

[0018] (9) In any one of (1) to (8) above, the present invention provides that when the composite solid electrolyte is exposed to a temperature of 25°C and a relative humidity of 0.5% to 0.6%, the amount of hydrogen sulfide (H2S) generated in the first hour is 15 cm³ per gram of the composite solid electrolyte. 3 The following composite solid electrolyte is provided.

[0019] (10) The present invention provides an all-solid-state battery comprising a composite solid electrolyte according to any one of (1) to (9) above. [Effects of the Invention]

[0020] The composite solid electrolyte according to the present invention has a polymer coating layer with excellent atmospheric stability and chemical resistance formed on sulfide-based solid electrolyte particles. Not only is the composite solid electrolyte itself highly atmospherically stable, but its chemical resistance can also be improved during the wet process when manufacturing batteries. [Modes for carrying out the invention]

[0021] The present invention will be described in more detail below to facilitate understanding of it.

[0022] The terms and words used herein should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0023] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0024] In this specification, terms such as “includes,” “equip,” or “have” indicate the presence of implemented features, figures, steps, components, or combinations thereof, but should be understood not to preclude the existence or possibility of adding one or more different features, figures, steps, components, or combinations thereof.

[0025] In this specification, Mooney viscosity is a value measured using a Mooney viscometer. Specifically, the sample is placed on the rotor of the lower die inside the Mooney viscometer, the upper die is lowered at a predetermined piston pressure (approximately 70 psi), the die is preheated at an internal temperature of 100°C for 1 minute, and the rotational force (torque) applied to the rotor is measured while it is rotated clockwise at a speed of 2 rpm for 4 minutes. In this specification, Mooney viscosity is the torque value measured after 4 minutes have elapsed since the 1 minute preheating (total of 5 minutes including preheating time). In this specification, the measurement conditions for Mooney viscosity are indicated as (ML1+4, 100°C), where M is an abbreviation for Mooney Viscosity, L is an abbreviation for Large rotor, the number 1 is the preheating time, +4 is the rotor rotation time, and 100°C is the measurement temperature.

[0026] Composite solid electrolyte The composite solid electrolyte according to the present invention comprises sulfide-based solid electrolyte particles and a polymer coating layer formed on the sulfide-based solid electrolyte particles, wherein the polymer coating layer contains a polymer having a Mooney viscosity (ML1+4, 100°C) of 30 or more and 110 or less.

[0027] The inventors of the present invention have discovered that, in the case of the composite solid electrolyte according to the present invention, a polymer coating layer with excellent atmospheric stability (excellent moisture and oxygen barrier performance) is formed on the sulfide-based solid electrolyte particles, and that not only is the atmospheric stability of the composite solid electrolyte itself excellent, but chemical resistance can also be improved in dry and wet processes when manufacturing batteries, thus completing the present invention.

[0028] The composite solid electrolyte according to the present invention has a polymer coating layer that contains a polymer with a Mooney viscosity (ML1+4, 100°C) of 30 or more and 110 or less, which can suppress the decomposition and degradation of sulfide-based solid electrolyte particles when exposed to moisture or oxygen. As a result, in particular, the generation of hydrogen sulfide, a toxic gas, can be suppressed, and a decrease in the ionic conductivity of the composite solid electrolyte can be prevented. Specifically, the Mooney viscosity (ML1+4, 100°C) of the polymer can be 30 to 90, and more specifically, 30 to 80. On the other hand, if the Mooney viscosity of the polymer is less than 30, there is a problem of instability when the battery is operated due to reduced heat resistance and chemical resistance, and if it is greater than 110, there is a problem that the coating layer is formed thickly and unevenly, resulting in low ionic conductivity and insufficient moisture barrier effect.

[0029] According to the present invention, the sulfide-based solid electrolyte can have an argyrodite-type crystal structure in terms of high ionic conductivity and low reactivity with the lithium anode. The sulfide-based solid electrolyte can be a sulfide-based solid electrolyte containing Li, P, and S. For example, the sulfide-based solid electrolyte may contain Li 7-x PS 6-x A x (where A can be Cl, Br, i, Sn, or any combination thereof, and x can be 0 ≤ x ≤ 2.)

[0030] According to the present invention, the polymer of the polymer coating layer can be one or more selected from a polymer of acrylonitrile monomer and butadiene monomer, its hydride, and a polymer of styrene monomer and butadiene monomer. That is, the polymer of the polymer coating layer can be one or more selected from an acrylonitrile-butadiene resin, which is a copolymer of acrylonitrile monomer and butadiene monomer, a hydrogenated acrylonitrile-butadiene resin, which is its hydride, and a styrene-butadiene resin, which is a copolymer of styrene monomer and butadiene monomer. In this case, it is similar to a binder material and has the advantage of improving the dispersibility of the composite solid electrolyte particles in the electrode slurry process.

[0031] According to the present invention, the polymer in the polymer coating layer may include repeating units represented by the following chemical formula 1 and repeating units represented by the following chemical formula 2, in terms of improving the dispersibility of composite solid electrolyte particles in the electrode slurry process.

[0032] [ka]

[0033] [ka]

[0034] According to the present invention, the polymer in the polymer coating layer may contain 15% to 50% by weight, specifically 20% to 40% by weight, of repeating units derived from acrylonitrile monomers, relative to the total weight of the polymer. In this case, there is an advantage that it is easily soluble in the nonpolar solvent used in the manufacture of the coating solution, and the dispersibility of the composite solid electrolyte particles is improved.

[0035] According to the present invention, the polymer in the polymer coating layer may contain 50% to 85% by weight, specifically 60% to 80% by weight, of repeating units derived from butadiene monomers, relative to the total weight of the polymer.

[0036] For example, if the polymer in the polymer coating layer consists of repeating units represented by chemical formula 1 and repeating units represented by chemical formula 2, the repeating units represented by chemical formula 1 may be included in an amount of 15% to 50% by weight of the total weight of the polymer, and the repeating units represented by chemical formula 2 may be included in an amount of 50% to 85% by weight.

[0037] According to the present invention, the polymer coating layer may be present in an amount of 0.1 to 10 parts by weight, specifically 0.1 to 7 parts by weight, or more specifically 0.5 to 5 parts by weight, per 100 parts by weight of the sulfide-based solid electrolyte particles. In this case, the moisture barrier effect can be improved, and the decrease in ionic conductivity can be minimized.

[0038] According to the present invention, the composite solid electrolyte can have an ionic conductivity of 0.001 mS / cm or higher, specifically 0.001 mS / cm to 20 mS / cm, and more specifically 0.01 mS / cm to 10 mS / cm or 0.01 mS / cm to 5 mS / cm. While a higher ionic conductivity of the electrolyte is preferable, when a polymer coating layer is formed so that the ionic conductivity satisfies the above range, as in the present invention, the moisture stability effect can be improved.

[0039] According to the present invention, when the composite solid electrolyte is exposed to a temperature of 25°C and a relative humidity of 0.5% to 0.6%, the amount of hydrogen sulfide (H2S) generated in the first hour is 15 cm³ per gram of the composite solid electrolyte. 3 Specifically, 14cm 3 The following is possible. That is, the composite solid electrolyte according to the present invention has excellent moisture stability, and even after exposure to moisture, the rate of decrease in ionic conductivity is low. In particular, the amount of hydrogen sulfide generated, which is a toxic gas, is small and the generation rate is slow, thus ensuring process stability. On the other hand, the atmosphere in which the composite solid electrolyte is exposed to a temperature of 25°C and a relative humidity of 0.5% to 0.6% can be an atmospheric atmosphere.

[0040] The composite solid electrolyte according to the present invention can be manufactured by coating sulfide-based solid electrolyte particles onto a polymer composition containing a polymer having a Mooney viscosity (ML1+4, 100°C) of 30 or more and 110 or less.

[0041] The aforementioned sulfide-based solid electrolyte particles can be synthesized, for example, by mechanical milling. Specifically, three precursors, Li2S, P2S5, and LiCl, are weighed according to stoichiometric measurements and then mixed by ball milling. The resulting mixed precursor is heat-treated to crystallize, and then pulverized again by ball milling. The mixing, heat treatment, and pulverization processes are carried out in an inert gas atmosphere.

[0042] Polymers having a Mooney viscosity (ML1+4, 100°C) of 30 to 110 can be produced by polymerizing the above-mentioned acrylonitrile monomer and butadiene monomer by methods such as suspension polymerization, solution polymerization, or bulk polymerization. For example, polymers can be produced by dispersing the above-mentioned acrylonitrile monomer and butadiene monomer, along with selectively a chain transfer agent, dispersant, thermal initiator, etc., in a solvent, and then performing suspension polymerization while mixing with a stirrer.

[0043] Furthermore, the polymer composition can be produced by dissolving or dispersing a polymer having a Mooney viscosity (ML1+4, 100°C) of 30 to 110 in a solvent such as toluene or xylene. Here, the weight ratio of the polymer having a Mooney viscosity (ML1+4, 100°C) of 30 to 110 to the solvent such as toluene or xylene can be 1:20 to 2:1.

[0044] Finally, the coating may be carried out by mixing and stirring the polymer composition with the sulfide-based solid electrolyte and then drying it, or by spraying the polymer composition onto the sulfide-based solid electrolyte and then drying it. However, it is not limited to these methods, and may be carried out by methods known in the art.

[0045] all solid state battery The present invention provides an all-solid-state battery containing the composite solid electrolyte.

[0046] Specifically, the all-solid-state battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, which includes the composite solid electrolyte according to the present invention.

[0047] The all-solid-state battery according to the present invention exhibits less reduction in ionic conductivity due to moisture, and can achieve excellent initial efficiency, lifespan characteristics, and output characteristics.

[0048] Herein, the all-solid-state battery of the present invention can be manufactured by conventional methods well known in the art. For example, it can be manufactured by laminating a positive electrode and a negative electrode such that a solid electrolyte layer is present between them and then pressurizing them.

[0049] (1) Positive electrode The positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, and a solvent onto a positive electrode current collector.

[0050] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. Furthermore, fine irregularities can be formed on the surface to strengthen the bonding force of the positive electrode active material, and it can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and nonwoven fabrics.

[0051] The positive electrode active material, as a compound capable of reversible lithium intercalation and deintercalation, may specifically comprise a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum. More specifically, the lithium metal oxide includes lithium-manganese based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt based oxides (e.g., LiCoO2, etc.), lithium-nickel based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese based oxides (e.g., LiNi 1-Y Mn Y O2 (wherein 0<Y<1), LiMn 2-z Ni z O4 (wherein 0<Z<2), etc.), lithium-nickel-cobalt based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (wherein 0<Y1<1), etc.), lithium-manganese-cobalt based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (wherein 0<Y2<1), LiMn 2-z1 Co z1 O4 (wherein 0<Z1<2), etc.), lithium-nickel-manganese-cobalt based 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 p1 Co 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) oxides (e.g., Li(Ni p2 Co q2 Mn r3 M S2)O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r3 and s2 are each an independent atomic fraction of the element, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, and p2+q2+r3+s2=1), etc.), and any one or two or more of these compounds may be contained.

[0052] Among these, in terms of being capable of improving the capacity characteristics and stability of a battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )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.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the remarkable improvement effect achieved by controlling the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )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., and any one of these or a mixture of two or more thereof may be used.

[0053] The positive electrode active material can be present in the positive electrode slurry at an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, relative to the total weight of the solids other than the solvent.

[0054] The aforementioned binder is a component that helps to bond the conductive material, active material, and 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.

[0055] Typically, the binder can be present in the cathode slurry at an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the solids other than the solvent.

[0056] The aforementioned conductive material is a component that further improves the conductivity of the positive electrode active material.

[0057] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; 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.

[0058] Typically, the conductive material can be included in the positive electrode slurry at an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, relative to the total weight of solid matter other than the solvent.

[0059] The solvent may include organic solvents such as NMP (N-methyl-2-pyrrolidone) and can be used in an amount that results in a desirable viscosity when the positive electrode active material and, selectively, a binder and conductive material are included. For example, the concentration of the solids containing the positive electrode active material and, selectively, the binder and conductive material can be 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0060] (2) Negative electrode The negative electrode can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, binder, conductive material, and solvent onto a negative electrode current collector, or by using a graphite electrode made of carbon (C) or the metal itself as the negative electrode.

[0061] For example, when a negative electrode is manufactured by coating a negative electrode slurry onto the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. Also, similar to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and nonwoven fabrics.

[0062] The negative electrode active material may be natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), Si, SiO xMetals (Me) that are Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of the aforementioned metals (Me); oxides (MeO) of the aforementioned metals (Me) x Examples of negative electrode active materials include silicon (Si), silicon oxide (SiO2), and one or more selected from the group consisting of the aforementioned metals (Me) and carbon composites. Specifically, negative electrode active materials include silicon (Si), silicon oxide (SiO2), and silicon oxide (SiO2). x A silicon-based negative electrode active material, such as ) or a silicon alloy, can be used. In this case, a thin, stable SEI layer containing siloxane bonds is formed, further improving the high-temperature stability and lifespan characteristics of the battery.

[0063] The negative electrode active material can be present in the negative electrode slurry at an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, relative to the total weight of the solid components other than the solvent.

[0064] The aforementioned binder is a component that helps to bond the conductive material, active material, and 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.

[0065] Typically, the binder can be present in the negative electrode slurry at an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the solids other than the solvent.

[0066] The conductive material is a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. Examples of such materials that can be used 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 fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0067] The conductive material can be included in the negative electrode slurry at an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the solids other than the solvent.

[0068] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and can be used in an amount that results in a desirable viscosity when the negative electrode active material and, selectively, a binder and conductive material are included. For example, the solid content including the negative electrode active material and, selectively, the binder and conductive material may be included in a concentration of 50% to 95% by weight, preferably 70% to 90% by weight.

[0069] When using a metal itself as the negative electrode, it can be manufactured by physically bonding, rolling, or vapor-depositing the metal onto the metal thin film itself or onto the negative electrode current collector. The vapor deposition method can be either electro-deposition or chemical vapor deposition.

[0070] For example, the metal bonded / rolled / deposited onto the metal thin film itself or onto the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0071] (3) Solid electrolyte layer The solid electrolyte layer may further contain a binder in addition to the solid electrolyte according to the present invention.

[0072] The aforementioned binder is a component that helps to bond the conductive material, active material, and 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.

[0073] Typically, the binder can be present in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the solid electrolyte layer.

[0074] The present invention provides a battery module and a battery pack containing the all-solid-state battery as a unit cell. Since the battery module and battery pack include the secondary battery having high capacity, high rate-limiting characteristics and cycle characteristics, they can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0075] Hereinafter, preferred embodiments are presented to facilitate understanding of the present invention. However, these embodiments are merely illustrative examples, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present description and the technical concept. It goes without saying that such variations and modifications fall within the scope of the appended claims.

[0076] Manufacturing example Three precursors, Li2S, P2S5, and LiCl, were dry-mixed (ball-milled) in a molar ratio of 5:1:2. A planetary ball mill equipped with zirconia balls was used for dry mixing, and the mill was rotated at a speed of 300 rpm or more to ensure uniform mixing. The resulting mixed precursor was then heat-treated at 600°C for 12 hours to crystallize, and then pulverized by ball milling to produce Li6PS5Cl having an argyrodite-type crystal structure. All of the above processes were carried out under an inert Ar atmosphere.

[0077] Examples and Comparative Examples Example 1 A polymer composition was prepared by dissolving 5 parts by weight of a polymer having a Mooney viscosity of 35 in 100 parts by weight of xylene. Here, the polymer contains 33.0% by weight of repeating units derived from acrylonitrile monomers, relative to the total weight of the polymer.

[0078] The polymer composition and Li6PS5Cl having an argyrodite crystal structure were mixed in a 1:1 weight ratio, stirred for 1 hour using a stirrer, and then the solvent was removed by vacuum drying to form a polymer coating layer on the Li6PS5Cl particles having an argyrodite crystal structure.

[0079] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer with a Mooney viscosity of 35 was formed on Li6PS5Cl particles having an argyrodite-type crystal structure. Here, the content of the polymer coating layer was 4.76 parts by weight per 100 parts by weight of Li6PS5Cl.

[0080] Example 2 A composite solid electrolyte was obtained in the same manner as in Example 1, except that a polymer with a Mooney viscosity of 46 was used, and the polymer contained a polymer with a Mooney viscosity of 46, with a Mooney viscosity of 46. The polymer contained 33.5% by weight of repeating units derived from acrylonitrile monomers relative to the total weight of the polymer.

[0081] Example 3 A composite solid electrolyte was obtained in the same manner as in Example 1, except that a polymer with a Mooney viscosity of 77.5 was used, and 33.5% by weight of repeating units derived from acrylonitrile monomers was used relative to the total weight of the polymer. The polymer coating layer containing the polymer with a Mooney viscosity of 77.5 was formed on Li6PS5Cl particles having an argyrodite-type crystal structure.

[0082] Comparative Example 1 Li6PS5Cl having an argyrodite-type crystal structure, produced in the manufacturing example, was used as the solid electrolyte in Comparative Example 1.

[0083] Comparative Example 2 A composite solid electrolyte was obtained in the same manner as in Example 1, except that a polymer with a Mooney viscosity of 27 was used, and the polymer contained a polymer with a Mooney viscosity of 27, with a Mooney viscosity of 27. The polymer contained 33.5% by weight of repeating units derived from acrylonitrile monomers relative to the total weight of the polymer.

[0084] Comparative Example 3 A composite solid electrolyte was obtained in the same manner as in Example 1, except that a polymer with a Mooney viscosity of 115 was used, and the polymer contained 33.5% by weight of repeating units derived from acrylonitrile monomers relative to the total weight of the polymer. The polymer coating layer containing the polymer with a Mooney viscosity of 115 was formed on Li6PS5Cl particles having an argyrodite-type crystal structure.

[0085] [Table 1]

[0086] Experimental Example 1: Evaluation of Ionic Conductivity 150 mg each of the composite solid electrolytes from Examples 1-3, the solid electrolyte from Comparative Example 1, and the composite solid electrolyte powders from Comparative Examples 2-3 were placed in a 13 mm diameter SUS mold. With the mold mounted in a press machine along with insulating PEEK, a potentiostat was connected to the SUS mold. After pressurizing to 370 MPa to sufficiently densify the electrolyte structure, the pressure was slowly reduced and maintained at 100 MPa while AC impedance measurements were performed at measurement frequencies from 1 Hz to 7 MHz. Ionic conductivity was calculated from the measured resistance values ​​using a Nyquist plot and is shown in Table 2 below. All measurements were performed in a dry room at a temperature of 25°C and a relative humidity of 0.59%.

[0087] Experimental Example 2: Evaluation of Hydrogen Sulfide Gas Generation 5 mg each of the composite solid electrolytes from Examples 1-3, the solid electrolyte from Comparative Example 1, and the composite solid electrolyte powders from Comparative Examples 2-3 were taken and left for at least one hour in a glove box equipped with a hydrogen sulfide sensor (in a dry air atmosphere controlled to a relative humidity of 0.59%). Immediately after leaving the samples, the amount of hydrogen sulfide generated per gram of the composite solid electrolyte was calculated based on the amount of hydrogen sulfide generated after one hour, and this is shown in Table 2 below.

[0088] [Table 2]

[0089] Referring to Table 2, the composite solid electrolytes of Examples 1-3 generate less hydrogen sulfide gas than the solid electrolytes of Comparative Examples 1-3, confirming their superior atmospheric stability and chemical resistance. Because the polymers used in the polymer coating layers of Examples 1-3 act as resistors, the composite solid electrolytes of Examples 1-3 exhibit significantly superior moisture barrier performance, even though their ionic conductivity is inferior to that of Comparative Examples 1 and 2.

[0090] In other words, the composite solid electrolyte according to the present invention contains a polymer coating layer with a Mooney viscosity (ML1+4, 100°C) of 30 to 110, which suppresses the decomposition and degradation of sulfide-based solid electrolyte particles when exposed to moisture or oxygen. This, in particular, suppresses the generation of hydrogen sulfide, a toxic gas, and prevents a decrease in the ionic conductivity of the composite solid electrolyte.

Claims

1. Sulfide-based solid electrolyte particles, The sulfide-based solid electrolyte particles include a polymer coating layer formed on the sulfide-based solid electrolyte particles, The polymer coating layer contains a polymer having a Mooney viscosity (ML1+4, 100°C) of 30 or more and 110 or less. The polymer in the polymer coating layer is a composite solid electrolyte, one or more selected from a polymer of acrylonitrile monomer and butadiene monomer, its hydride, and a polymer of styrene monomer and butadiene monomer.

2. The composite solid electrolyte according to claim 1, wherein the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

3. The polymer in the polymer coating layer comprises a repeating unit represented by the following chemical formula 1 and a repeating unit represented by the following chemical formula 2, as described in claim 1, for the composite solid electrolyte. 【Chemistry 1】

4. The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer contains 15% to 50% by weight of repeating units derived from acrylonitrile monomers, relative to the total weight of the polymer.

5. The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer contains 50% to 85% by weight of repeating units derived from butadiene monomers, relative to the total weight of the polymer.

6. The composite solid electrolyte according to claim 1, wherein the polymer coating layer is contained in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the sulfide-based solid electrolyte particles.

7. The composite solid electrolyte according to claim 1, wherein the ionic conductivity is 0.001 mS / cm to 20 mS / cm.

8. When the composite solid electrolyte is exposed to a temperature of 25°C and a relative humidity of 0.5% to 0.6%, hydrogen sulfide (H) is generated in the first hour. ２ The amount of S generated is 15 cm³ per gram of the composite solid electrolyte. ３ The composite solid electrolyte according to claim 1, which is as follows:

9. A solid-state battery comprising a composite solid electrolyte according to any one of claims 1 to 8.

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