Composite solid electrolyte and all-solid-state battery including the same

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 the benefit of priority based on Korean Patent Application No. 10-2022-0082075, filed on July 4, 2022, and all the contents disclosed in the literature of the Korean Patent Application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a sulfide-based composite solid electrolyte with improved air stability and chemical resistance, and an all-solid-state battery including the same.

Background Art

[0003] An all-solid-state battery is a battery in which the liquid electrolyte filling the space between the positive and negative electrodes of a conventional lithium secondary battery is replaced with a solid. It is safe without the risk of explosion, and has a higher energy density than conventional batteries, attracting attention as a next-generation battery. The solid electrolyte used in an all-solid-state battery is a solid substance through which lithium ions in the battery can conduct, and currently has a high ionic conductivity at the level of the electrolyte applied to lithium secondary batteries. Core materials constituting the solid electrolyte include polymers, sulfides, oxides, etc. Among them, sulfide-based solid electrolytes with high flexibility and high ionic conductivity are evaluated as suitable for manufacturing high-capacity large batteries.

[0004] However, since sulfide-based solid electrolytes have high reactivity with moisture, they react not only with moisture in the air but also with moisture under low humidity conditions, generating hydrogen sulfide (H2S), a harmful gas. Therefore, not only does the toxic hydrogen sulfide have an adverse effect on the stability of workers, but there is also a problem that the performance of the sulfide-based solid electrolyte itself deteriorates.

[0005] Therefore, there is a need to develop a sulfide-based solid electrolyte with excellent air stability and chemical resistance.

Summary of the Invention

Problems to be Solved by the Invention

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

[0007] However, the problems to be solved by the present invention are not limited to the problems 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 Problems

[0008] 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 including 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.

[0010] (2) In the above (1), the present invention provides a composite solid electrolyte in which the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0011] (3) In the above (1) or (2), the present invention provides a composite solid electrolyte in which the polymer of the polymer coating layer is one or more selected from 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) In any one of the above (1) to (3), the present invention provides a composite solid electrolyte in which the polymer of the polymer coating layer contains 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 monomer based on the total weight of the polymer.

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

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

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

[0018] (9) The present invention provides a composite solid electrolyte in any one of (1) to (8) above, wherein 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 cm per 1 g of the composite solid electrolyte. 3 as follows.

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

Advantages of the Invention

[0020] The composite solid electrolyte according to the present invention has a polymer coating layer excellent in air stability and chemical resistance formed on the sulfide-based solid electrolyte particles, and not only has excellent air stability of the composite solid electrolyte itself, but also the chemical resistance can be improved in a wet process when manufacturing a battery.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, in order to facilitate the understanding of the present invention, the present invention will be described in more detail.

[0022] The terms and words used in this specification should not be construed as being limited to their ordinary or dictionary meanings. In accordance with the principle that the inventors can appropriately define the concepts of the terms in order to explain their invention in the best way, they should be construed in meanings and concepts consistent with the technical idea of the present invention.

[0023] The terms used in this specification are merely used to explain exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly has a different meaning.

[0024] In this specification, terms such as "including", "comprising", or "having" are used to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and should be understood not to preclude in advance the presence or possibility of addition of one or more different features, numbers, steps, components, or combinations thereof.

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

[0026] Composite solid electrolyte The composite solid electrolyte according to the present invention 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 polymer having a Mooney Viscosity (ML1+4, 100 °C) of 30 or more and 110 or less.

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

[0028] The composite solid electrolyte according to the present invention has a polymer coating layer containing a polymer having a Mooney viscosity (ML1+4, 100 °C) of 30 or more and 110 or less, and when exposed to moisture or oxygen, it can suppress the decomposition and deterioration of sulfide-based solid electrolyte particles. As a result, in particular, the generation of hydrogen sulfide, which is a toxic gas, can be suppressed, and the decrease in the ionic conductivity of the composite solid electrolyte can be prevented. The Mooney viscosity (ML1+4, 100 °C) of the polymer can specifically be 30 to 90, and more specifically 30 to 80. On the other hand, when the Mooney viscosity of the polymer is less than 30, there are problems such as a decrease in heat resistance and chemical resistance and instability during battery operation. When it exceeds 110, there are problems such as the coating layer being thick and unevenly formed, 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 a lithium negative electrode. The sulfide-based solid electrolyte can be a sulfide-based solid electrolyte containing Li, P, and S. For example, the sulfide-based solid electrolyte is Li 7-x PS 6-x A x (where A is Cl, Br, I, Sn, or a combination thereof, and x is 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 an acrylonitrile monomer and a butadiene monomer, a hydride thereof, and a polymer of a styrene monomer and a butadiene monomer. That is, the polymer of the polymer coating layer can be one or more selected from acrylonitrile-butadiene resin, which is a copolymer of an acrylonitrile monomer and a butadiene monomer, hydrogenated acrylonitrile-butadiene resin, which is a hydride thereof, and styrene-butadiene resin, which is a copolymer of a styrene monomer and a butadiene monomer. In this case, it is similar to a binder substance and has the advantage of improving the dispersibility of composite solid electrolyte particles in the electrode slurry process.

[0031] According to the present invention, the polymer of the polymer coating layer can contain a repeating unit represented by the following Chemical Formula 1 and a repeating unit represented by the following Chemical Formula 2 in terms of improving the dispersibility of the composite solid electrolyte particles in the electrode slurry process.

[0032]

Chemical formula

[0033]

Chemical formula

[0034] According to the present invention, the polymer of the polymer coating layer can contain 15 wt% to 50 wt%, specifically 20 wt% to 40 wt% of a repeating unit derived from an acrylonitrile monomer based on the total weight of the polymer. In this case, it is easy to dissolve in the non-polar solvent used in the production of the coating solution, and there is an advantage in improving the dispersibility of the composite solid electrolyte particles.

[0035] According to the present invention, the polymer of the polymer coating layer can contain 50 wt% to 85 wt%, specifically 60 wt% to 80 wt% of a repeating unit derived from a butadiene monomer based on the total weight of the polymer.

[0036] For example, when the polymer of the polymer coating layer consists of the repeating unit represented by the Chemical Formula 1 and the repeating unit represented by the Chemical Formula 2, the repeating unit represented by the Chemical Formula 1 can be contained in a content of 15 wt% to 50 wt% based on the total weight of the polymer, and the repeating unit represented by the Chemical Formula 2 can be contained in a content of 50 wt% to 85 wt%.

[0037] According to the present invention, the polymer coating layer can be included in an amount of 0.1 to 10 parts by weight, specifically 0.1 to 7 parts by weight, and more specifically 0.5 to 5 parts by weight, based on 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 more, 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. Although a higher ionic conductivity of the electrolyte is preferred, 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 cm per 1 g of the composite solid electrolyte. 3 Specifically, 14 cm or less. 3 That is, the composite solid electrolyte according to the present invention has excellent moisture stability, a low reduction rate of ionic conductivity even after exposure to moisture, and in particular, a small amount of hydrogen sulfide, which is a toxic gas, and a slow generation rate, so that process stability can be ensured. On the other hand, the atmosphere when 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 air atmosphere.

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

[0041] The sulfide-based solid electrolyte particles can be synthesized, for example, by a mechanical milling method. Specifically, three kinds of precursors, Li2S, P2S5, and LiCl, are weighed according to stoichiometry, and then ball-milled and mixed. After the obtained mixed precursor is heat-treated for crystallization, it is also pulverized by ball-milling. The mixing, heat-treatment, and pulverization processes are carried out in an inert gas atmosphere.

[0042] The polymer having a Mooney Viscosity (ML1+4, 100 °C) of 30 or more and 110 or less can be produced by polymerizing the above-mentioned acrylonitrile monomer and butadiene monomer by methods such as suspension polymerization, solution polymerization, and bulk polymerization. For example, after dispersing the above-mentioned acrylonitrile monomer and butadiene monomer, and selectively, a chain transfer agent, a dispersant, a thermal initiator, etc. in a solvent, suspension polymerization can be carried out while mixing with a stirrer to produce a polymer.

[0043] Further, the polymer composition can be produced by dissolving or dispersing a polymer having a Mooney Viscosity (ML1+4, 100 °C) of 30 or more and 110 or less 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 or more and 110 or less to the solvent such as toluene or xylene can be 1:20 to 2:1.

[0044] Finally, the coating can be performed by a process of mixing and stirring the polymer composition and the sulfide-based solid electrolyte and then drying, or by a process of spraying the polymer composition onto the sulfide-based solid electrolyte and then drying. However, it is not limited thereto, and it can be performed by a method known in the art.

[0045] All-solid-state battery The present invention provides an all-solid-state battery including 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 containing the composite solid electrolyte according to the present invention disposed between the positive electrode and the negative electrode.

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

[0048] Here, the all-solid-state battery of the present invention can be manufactured by a conventional method well-known in the art. For example, it can be manufactured by laminating such that a solid electrolyte layer exists between the positive electrode and the negative electrode and then applying pressure.

[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, a solvent, etc. on a positive electrode current collector.

[0050] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. Also, fine irregularities can be formed on the surface to strengthen the binding force of the positive electrode active material, and it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0051] The positive electrode active material can include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium, as a compound capable of reversible intercalation and deintercalation of lithium. More specifically, the lithium metal oxide can be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (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 a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo; p2, q2, r3, and s2 are atomic fractions of independent elements, 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 can be included.

[0052] Among them, in terms of being able to enhance the capacity characteristics and stability of the 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.), etc. Considering the remarkable improvement effect by controlling the types and content ratios of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide can be 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 or two or more of these mixtures can be used.

[0053] The positive electrode active material can be contained in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, more preferably 80% to 98% by weight, based on the total weight of the solid content other than the solvent in the positive electrode slurry.

[0054] The binder is a component that helps bind 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.

[0055] Generally, the binder can be contained 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 solid content other than the solvent in the positive electrode slurry.

[0056] The conductive material is a component for further improving 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 has conductivity. For example, graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, 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] Generally, the conductive material can be contained in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, more preferably 1 wt% to 10 wt% based on the total weight of the solids other than the solvent in the positive electrode slurry.

[0059] The solvent can include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and when including the positive electrode active material and optionally a binder and a conductive material, etc., it can be used in an amount that results in a preferable viscosity. For example, it can be included such 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%, more preferably 70 wt% to 90 wt%.

[0060] (2) Negative electrode 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, a solvent, etc. on a negative electrode current collector, or a graphite electrode or the metal itself made of carbon (C) can be used as the negative electrode.

[0061] 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. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change to the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Also, similar to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

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

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

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

[0065] Generally, the binder can be contained 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 solid components other than the solvent in the negative electrode slurry.

[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 has conductivity. For example, graphite such as natural graphite and 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; conductive materials such as polyphenylene derivatives, etc. can be used.

[0067] The conductive material can be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solid components other than the solvent in the negative electrode slurry.

[0068] The solvent can include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and can be used in an amount that results in a preferred viscosity when containing the negative electrode active material and optionally a binder, a conductive material, etc. For example, it can be contained such that the concentration of the solid components including the negative electrode active material and optionally a binder and a conductive material is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

[0069] When using the metal itself as the negative electrode, it can be manufactured by methods such as physically bonding, rolling, or vapor depositing the metal on the metal thin film itself or the negative electrode current collector. For the vapor deposition method, an electrical vapor deposition method or a chemical vapor deposition method can be used for the metal.

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

[0071] (3) Solid electrolyte layer In addition to the solid electrolyte according to the present invention, the solid electrolyte layer can further contain a binder.

[0072] The binder is a component that helps bind 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, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like.

[0073] Generally, the binder can be contained 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 solid electrolyte layer.

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

[0075] Hereinafter, in order to facilitate understanding of the present invention, preferred embodiments are presented. However, it is obvious to those skilled in the art that the embodiments are only illustrative of the description and various changes and modifications are possible within the scope of the description and the scope of the technical idea. Needless to say, such variations and modifications belong to the scope of the appended claims.

[0076] Production example Three precursors, Li2S, P2S5, and LiCl, were dry-mixed (ball-milled) at a molar ratio of 5:1:2. During the dry mixing, a planetary ball mill device with zirconia balls was used and rotated at a speed of 300 rpm or more for uniform mixing. Then, the obtained mixed precursor was heat-treated at 600 °C for 12 hours for crystallization and then pulverized by ball milling to produce Li6PS5Cl having an argyrodite-type crystal structure. The above processes were all 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 based on the total weight of the polymer.

[0078] The polymer composition and Li6PS5Cl having an argyrodite-type crystal structure were mixed at a weight ratio of 1:1 and 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-type crystal structure.

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

[0080] Example 2 A composite solid electrolyte in which a polymer coating layer containing a polymer having a Mooney viscosity of 46 was formed on Li6PS5Cl particles having an argyrodite-type crystal structure was obtained in the same manner as in Example 1, except that a polymer having a Mooney viscosity of 46 and containing 33.5% by weight of repeating units derived from acrylonitrile monomers based on the total weight of the polymer was used.

[0081] Example 3 A composite solid electrolyte with a polymer coating layer containing a polymer having a Mooney viscosity of 77.5 was obtained in the same manner as in Example 1, except that a polymer containing 33.5% by weight of repeating units derived from acrylonitrile monomer was used based on the total weight of the polymer, and the polymer coating layer 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 production example was used as the solid electrolyte of Comparative Example 1.

[0083] Comparative Example 2 A composite solid electrolyte with a polymer coating layer containing a polymer having a Mooney viscosity of 27 was obtained in the same manner as in Example 1, except that a polymer containing 33.5% by weight of repeating units derived from acrylonitrile monomer was used based on the total weight of the polymer, and the polymer coating layer was formed on Li6PS5Cl particles having an argyrodite-type crystal structure.

[0084] Comparative Example 3 A composite solid electrolyte with a polymer coating layer containing a polymer having a Mooney viscosity of 115 was obtained in the same manner as in Example 1, except that a polymer containing 33.5% by weight of repeating units derived from acrylonitrile monomer was used based on the total weight of the polymer, and the polymer coating layer 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 of Examples 1 to 3, the solid electrolyte of Comparative Example 1, and the composite solid electrolyte powders of Comparative Examples 2 to 3 were taken and put into a SUS mold with a diameter of 13 mm. With the mold mounted on a press together with PEEK for insulation, a potentiostat was connected to the SUS mold. After pressurizing at 370 MPa to sufficiently densify the electrolyte structure, the pressure was slowly decreased and maintained at 100 MPa while performing AC impedance measurements from a measurement frequency of 1 Hz to 7 MHz. From the measured resistance values, the ionic conductivity was calculated using a Nyquist plot and 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 the amount of hydrogen sulfide gas generated 5 mg each of the composite solid electrolytes of Examples 1 to 3, the solid electrolyte of Comparative Example 1, and the composite solid electrolyte powders of Comparative Examples 2 to 3 were taken and left in a glove box equipped with a hydrogen sulfide sensor (Drying Air atmosphere controlled to a relative humidity of 0.59%) for 1 hour or more. Immediately after leaving, the amount of hydrogen sulfide generated per gram of the composite solid electrolyte was calculated based on the amount of hydrogen sulfide generated in 1 hour and shown in Table 2 below.

[0088] [Table 2]

[0089] Referring to Table 2, it can be confirmed that the composite solid electrolytes of Examples 1 to 3 are excellent in atmospheric stability and chemical resistance because the amount of hydrogen sulfide gas generated is less than that of the solid electrolytes of Comparative Examples 1 to 3. Since the polymers used in the polymer coating layers of Examples 1 to 3 act as resistors, it can be confirmed that the composite solid electrolytes of Examples 1 to 3 are significantly superior in moisture barrier performance although their ionic conductivity is inferior to that of Comparative Examples 1 and 2.

[0090] That is to say, in the composite solid electrolyte according to the present invention, the polymer coating layer contains a polymer having a Mooney Viscosity (ML1+4, 100 °C) of 30 or more and 110 or less, and it can be seen that when exposed to moisture or oxygen, the decomposition and deterioration of the sulfide-based solid electrolyte particles can be suppressed. Thereby, in particular, it can be seen that the generation of hydrogen sulfide, which is a toxic gas, can be suppressed, and the decrease in the ionic conductivity of the composite solid electrolyte can be prevented.

Claims

1. 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 contains a polymer having a Mooney viscosity (ML1+4, 100°C) of 30 or more and 110 or less.

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

3. The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer is at least one selected from a polymer of an acrylonitrile monomer and a butadiene monomer, a hydride thereof, and a polymer of a styrene monomer and a butadiene monomer.

4. The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer contains a repeating unit represented by the following Chemical Formula 1 and a repeating unit represented by the following Chemical Formula 2.

5. 【Chemical 1】 The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer contains 15% by weight to 50% by weight of a repeating unit derived from an acrylonitrile monomer based on the total weight of the polymer.

6. The composite solid electrolyte according to claim 1, wherein the polymer in the polymer coating layer contains 50% by weight to 85% by weight of a repeating unit derived from a butadiene monomer based on the total weight of the polymer.

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

8. The composite solid electrolyte according to claim 1, having an ionic conductivity of 0.001 mS / cm to 20 mS / cm.

9.

10. 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 (H ２ S) generated in the first hour is 15 cm per gram of the composite solid electrolyte ３ or less. The composite solid electrolyte according to claim 1 A all-solid-state battery comprising the composite solid electrolyte according to any one of claims 1 to 9. ​

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