Composite solid electrolyte, method for producing the same, and all-solid-state battery including the same

Abstract

The present invention is an invention for improving the atmospheric stability of conventional sulfide-based solid electrolytes, and relates to 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 of the polymer coating layer comprises a repeating unit represented by Chemical Formula I described herein; a method for producing the composite solid electrolyte; and an all-solid-state battery comprising the composite solid electrolyte.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0109284, filed on August 30, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a sulfide-based composite solid electrolyte having improved atmospheric stability and chemical resistance, a method for producing the same, and an all-solid-state battery including the same. [Background technology]

[0003] All-solid-state batteries replace the liquid electrolyte currently used between the positive and negative electrodes of lithium secondary batteries with a solid electrolyte. These batteries are safe and explosion-free, and have a higher energy density than conventional batteries, drawing attention as a next-generation battery. The solid electrolyte used in all-solid-state batteries is a solid-state material that allows lithium ions to be conducted within the battery, and has high ionic conductivity comparable to that of the liquid electrolytes currently used in lithium secondary batteries. Key materials for solid electrolytes include polymers, sulfides, and oxides. Among these, sulfide-based solid electrolytes, which are highly flexible and have high ionic conductivity, are considered suitable for the production of large-capacity batteries.

[0004] However, sulfide-based solid electrolytes are highly reactive to moisture, and react not only with moisture in the atmosphere but also with moisture under low humidity conditions, generating the toxic gas hydrogen sulfide (H2S). This not only poses a risk to worker safety, but also leads to the problem of deterioration of the performance of the sulfide-based solid electrolyte itself.

[0005] Therefore, there is a need to develop sulfide-based solid electrolytes that are stable in the atmosphere and have excellent chemical resistance. Summary of the Invention [Problem to be solved by the invention]

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

[0007] However, the problems that the present invention aims to solve are not limited to the problems mentioned above, and other problems not mentioned will 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, a method for producing the 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 of the polymer coating layer comprises a repeating unit represented by the following chemical formula I: [ka] In the above chemical formula I, X is F or Cl.

[0010] (2) The present invention provides a composite solid electrolyte according to (1), wherein the polymer of the polymer coating layer includes a repeating unit represented by the following chemical formula 1: [ka]

[0011] (3) The present invention provides, in the above (1) or (2), a composite solid electrolyte in which the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0012] (4) The present invention provides a composite solid electrolyte according to any one of (1) to (3), wherein the polymer of the polymer coating layer has a weight average molecular weight (Mw) of 1,000 g / mol to 1,000,000 g / mol.

[0013] (5) The present invention provides a composite solid electrolyte according to any one of (1) to (4), wherein the polymer coating layer is contained in an amount of 0.1 to 10 parts by weight relative to 100 parts by weight of the sulfide-based solid electrolyte particles.

[0014] (6) The present invention provides a composite solid electrolyte according to any one of the above (1) to (5), which has an initial ionic conductivity of 0.001 mS / cm to 20 mS / cm.

[0015] (7) In any one of the above (1) to (6), the present invention is characterized in that when the composite solid electrolyte is exposed to an air atmosphere at a temperature of 25°C and a relative humidity of 0.5% to 0.6%, the amount of hydrogen sulfide (HS) generated in the first hour is 10 cm per 1 g of the composite solid electrolyte. 3 A composite solid electrolyte is provided, which is:

[0016] (8) The present invention provides a method for producing a composite solid electrolyte according to any one of (1) to (7), comprising the steps of: (A) mixing a polymer including a repeating unit represented by the following chemical formula I with a sulfide-based solid electrolyte to prepare a mixture; and (B) heat-treating the mixture at a temperature equal to or higher than the melting point of the polymer to form a polymer coating layer on particles of the sulfide-based solid electrolyte.

[0017] [ka] In the above chemical formula I, X is F or Cl.

[0018] (9) The present invention provides a method for producing a composite solid electrolyte according to (8), wherein the polymer contains a repeating unit represented by the following chemical formula 1: [ka]

[0019] (10) The present invention provides the method for producing a composite solid electrolyte according to (8) or (9), wherein in step (A), the polymer is mixed in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the sulfide-based solid electrolyte.

[0020] (11) The present invention provides the method for producing a composite solid electrolyte according to any one of the above (8) to (10), wherein the mixing is dry mixing.

[0021] (12) The present invention provides the method for producing a composite solid electrolyte according to any one of the above (8) to (11), wherein the heat treatment temperature is 180°C to 250°C.

[0022] (13) The present invention provides an all-solid-state battery including the composite solid electrolyte according to any one of (1) to (7) above. [Effects of the Invention]

[0023] The composite solid electrolyte according to the present invention has a polymer coating layer having excellent atmospheric stability and chemical resistance formed on sulfide-based solid electrolyte particles. This not only provides excellent atmospheric stability for the composite solid electrolyte itself, but also improves chemical resistance in a wet process during battery fabrication. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in more detail to facilitate understanding of the present invention.

[0025] The terms and words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0026] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0027] In this specification, the terms "comprises," "includes," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but are not intended to preclude the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0028] In this specification, "*" is a linking site between repeating units, and is F, Cl or H when it is at the end.

[0029] 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, and the polymer of the polymer coating layer includes a repeating unit represented by the following Chemical Formula I:

[0030] [ka] In the above chemical formula I, X is F or Cl.

[0031] According to the present invention, the polymer of the polymer coating layer may include a repeating unit represented by the following Formula 1:

[0032] [ka]

[0033] The present inventors have found that in the case of the composite solid electrolyte according to the present invention, a polymer coating layer having excellent atmospheric stability (excellent moisture and oxygen barrier properties) is formed on sulfide-based solid electrolyte particles, which not only improves the atmospheric stability of the composite solid electrolyte itself but also improves chemical resistance in dry and wet processes during battery fabrication, thereby completing the present invention.

[0034] In the composite solid electrolyte according to the present invention, the polymer coating layer includes a polymer having a repeating unit represented by Chemical Formula I, specifically, a polymer having a repeating unit represented by Chemical Formula 1, and this can prevent decomposition and deterioration of sulfide-based solid electrolyte particles when exposed to moisture or oxygen. As a result, generation of hydrogen sulfide, a toxic gas, can be suppressed. In addition, a decrease in the ionic conductivity of the composite solid electrolyte can be prevented.

[0035] In the composite solid electrolyte according to the present invention, the polymer coating layer includes a polymer having a repeating unit represented by Chemical Formula I, which has lower moisture permeability than polymers such as PTFE, PDMS, and EVA, specifically, a polymer having a repeating unit represented by Chemical Formula 1, and can better block contact of the sulfide-based solid electrolyte particles with moisture.

[0036] According to the present invention, in order to further improve moisture stability, the polymer may specifically consist of only repeating units represented by Chemical Formula 1. That is, the polymer may be polychlorotrifluoroethylene (PCTFE).

[0037] According to the present invention, the sulfide-based solid electrolyte may have an argyrodite-type crystal structure, which has high ionic conductivity and low reactivity with a lithium anode. The sulfide-based solid electrolyte may be a sulfide-based solid electrolyte containing Li, P, and S.

[0038] For example, the sulfide-based solid electrolyte may have a composition represented by the following Chemical Formula 2. In this case, the composite solid electrolyte according to the present invention may have high ionic conductivity and low reactivity with a lithium anode, and the sulfide-based solid electrolyte particles may be prevented from decomposing or deteriorating when exposed to moisture or oxygen.

[0039] [Chemical formula 2] Li a (P 1-b M b )S c X d

[0040] In chemical formula 2, M is one or more selected from Si, Sn, Nb, Ni, Ge, Ga, and Al; X is one or more selected from F, Cl, Br and I; 5.0 <a<7.5、0≦b≦0.7、3.5≦c≦7、0.8≦d≦1.7である。

[0041] The M is a doping element that is doped into the solid electrolyte having an argyrodite-type crystal structure, and may be one or more elements selected from Sn, Nb, Ni, Ge, Ga, and Al, specifically, one or more elements selected from Sn, Nb, Ge, and Al.

[0042] According to the present invention, the polymer of the polymer coating layer may have a weight-average molecular weight (Mw) of 1,000 g / mol to 1,000,000 g / mol. Specifically, the polymer of the polymer coating layer may have a weight-average molecular weight (Mw) of 1,000 g / mol or more, 200,000 g / mol or less, 500,000 g / mol or less, or 1,000,000 g / mol or less. When the weight-average molecular weight (Mw) of the polymer is within this range, a uniform and thin polymer coating layer can be formed, and the decrease in ionic conductivity can be minimized, thereby improving the moisture blocking effect.

[0043] According to the present invention, the polymer coating layer may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the sulfide-based solid electrolyte particles. Specifically, the polymer coating layer may be included in an amount of 0.1 to 0.5 parts by weight, 5 to 7 parts by weight, or 10 to 10 parts by weight based on 100 parts by weight of the sulfide-based solid electrolyte particles. In this case, the moisture barrier effect may be improved and a decrease in ion conductivity may be minimized.

[0044] According to the present invention, the solid electrolyte may have an initial ionic conductivity of 0.001 mS / cm to 20 mS / cm, specifically, 0.001 mS / cm or more, 0.01 mS / cm or more, and 5 mS / cm or less, 10 mS / cm or less, or 20 mS / cm or less. Although a higher ionic conductivity of the electrolyte is preferable, when the initial ionic conductivity satisfies the above range, an excellent effect of improving water stability can be achieved.

[0045] The initial ionic conductivity is a value calculated from the resistance value measured in a dry room at a temperature of 22°C and a relative humidity of 0.7% immediately after the preparation of the composite solid electrolyte. Specifically, the value is calculated by the following method.

[0046] i) Immediately after the production of the composite solid electrolyte, 150 mg of the composite solid electrolyte powder is taken and placed in a SUS mold with a diameter of 13 mm.

[0047] ii) With the mold mounted on a press together with the insulating PEEK, a potentiostat is connected to the SUS mold, and a pressure of 370 MPa is applied to sufficiently densify the electrolyte structure. The pressure is then slowly reduced and maintained at 100 MPa while measuring AC impedance at frequencies from 1 Hz to 7 MHz.

[0048] iii) Calculate the ionic conductivity from the measured resistance values ​​using a Nyquist plot.

[0049] According to the present invention, when the composite solid electrolyte is exposed to an air atmosphere at a temperature of 25°C and a relative humidity of 0.5% to 0.6%, the amount of hydrogen sulfide (HS) generated in the first hour is 10 cm per 1 g of the composite solid electrolyte. 3 It can be:

[0050] That is, the composite solid electrolyte according to the present invention has excellent water stability and generates a small amount of hydrogen sulfide, a toxic gas, at a slow rate, thereby ensuring process safety.

[0051] Method for manufacturing composite solid electrolyte The composite solid electrolyte according to the present invention can be prepared by coating sulfide-based solid electrolyte particles with a polymer composition including a polymer having a repeating unit represented by the following formula I:

[0052] [ka] In the above chemical formula I, X is F or Cl.

[0053] According to the present invention, the polymer may include a repeating unit represented by the following Formula 1:

[0054] [ka]

[0055] Specifically, the method for producing a composite solid electrolyte according to the present invention includes the steps of: (A) preparing a mixture by mixing a polymer including a repeating unit represented by Chemical Formula I with a sulfide-based solid electrolyte; and (B) heat-treating the mixture at a temperature equal to or higher than the melting point of the polymer to form a polymer coating layer on the sulfide-based solid electrolyte particles.

[0056] (A) Step The step (A) is a step of preparing a mixture by mixing a polymer including a repeating unit represented by the chemical formula I (specifically, a polymer including a repeating unit represented by the chemical formula 1) with a sulfide-based solid electrolyte.

[0057] The polymer including a repeating unit represented by Chemical Formula I, the polymer including a repeating unit represented by Chemical Formula 1, and the sulfide-based solid electrolyte are the same as those described above for the composite solid electrolyte according to the present invention.

[0058] The sulfide-based solid electrolyte can be synthesized by, for example, mechanical milling or solid-phase synthesis. Specifically, the sulfide-based solid electrolyte can be produced by stoichiometrically weighing three precursors, Li2S, P2S5, and LiCl, mixing them by ball milling, heat-treating the resulting mixed precursor to crystallize it, and then pulverizing it by ball milling again. Here, the mixing, heat-treating, and pulverizing steps can be performed in an inert gas atmosphere.

[0059] According to the present invention, in step (A), the polymer may be mixed in an amount of 0.1 to 10 parts by weight relative to 100 parts by weight of the sulfide-based solid electrolyte. Specifically, the polymer may be mixed in an amount of 0.1 part by weight or more, 1 part by weight or more, 2 parts by weight or more, 6 parts by weight or less, 7 parts by weight or less, or 10 parts by weight or less relative to 100 parts by weight of the sulfide-based solid electrolyte. In this case, a uniform polymer coating layer is formed, and a composite solid electrolyte having appropriate ion conductivity and excellent moisture blocking effect can be produced.

[0060] According to the present invention, the mixing may be dry mixing. Specifically, the mixing may be ball milling of the polymer and the sulfide-based solid electrolyte particles. The dry mixing may be performed using a planetary ball mill equipped with zirconia balls, and may be performed while rotating at a speed of 100 rpm to 200 rpm to achieve uniform mixing.

[0061] (B) Step Step (B) is a step of forming a polymer coating layer on the sulfide-based solid electrolyte particles by heat-treating the mixture at a temperature equal to or higher than the melting point of the polymer, i.e., a step of melting the polymer to form a polymer coating layer on the sulfide-based solid electrolyte particles.

[0062] According to the present invention, the heat treatment temperature may be 180° C. to 250° C., specifically 180° C. to 230° C., and more specifically 180° C. to 220° C. In this case, the polymer is sufficiently melted and aggregation of electrolyte particles can be minimized, which is advantageous in that a uniform composite solid electrolyte is produced.

[0063] The heat treatment may be carried out in an inert atmosphere to prevent side reactions from occurring.

[0064] The heat treatment may be performed for 1 to 8 hours, specifically, 1 hour or more, 2 hours or more, 4 hours or less, 5 hours or less, or 8 hours or less, so that the polymer is sufficiently melted and aggregation of the electrolyte particles is minimized.

[0065] All solid state battery The present invention provides an all-solid-state battery comprising the composite solid electrolyte.

[0066] Specifically, the all-solid-state battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a solid electrolyte layer including the composite solid electrolyte according to the present invention disposed between the positive electrode and the negative electrode.

[0067] The all-solid-state battery according to the present invention has excellent water stability, and can provide excellent initial efficiency, life characteristics, and output characteristics of the battery.

[0068] The all-solid-state battery of the present invention can be manufactured by a conventional method known in the art, for example, by stacking a positive electrode and a negative electrode so that a solid electrolyte layer is present between them and applying pressure.

[0069] (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.

[0070] 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. In addition, 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, nets, porous bodies, foams, non-woven bodies, etc.

[0071] 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 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 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co qMn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, and p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, and 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 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are the atomic fractions of the respective 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.

[0072] 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 (e.g., 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 (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the significance of the improvement effect by controlling the types and content ratios of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2Co 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 a mixture of two or more of these can be used.

[0073] The positive electrode active material may be contained in an amount of 60% by weight to 99% by weight, specifically 70% by weight to 99% by weight, more specifically 80% by weight to 98% by weight, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0074] The binder is a component that helps bind the conductive material, active material, and current collector together. 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.

[0075] Typically, the binder may be contained in an amount of 1 wt % to 20 wt %, specifically 1 wt % to 15 wt %, more specifically 1 wt % to 10 wt %, based on the total weight of the solid content of the positive electrode slurry other than the solvent.

[0076] The conductive material is a component for further improving the conductivity of the positive electrode active material.

[0077] 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, 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 fiber and metal fiber; 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 may be used.

[0078] Typically, the conductive material may be contained in an amount of 1 wt % to 20 wt %, specifically 1 wt % to 15 wt %, more specifically 1 wt % to 10 wt %, based on the total weight of solids other than the solvent in the positive electrode slurry.

[0079] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that provides a desired viscosity when the positive electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the concentration of the solids including the positive electrode active material and, optionally, a binder and a conductive material is 50 wt % to 95 wt %, specifically 70 wt % to 95 wt %, more specifically 70 wt % to 90 wt %.

[0080] (2) Negative electrode The negative electrode can be prepared by, for example, coating a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent, or a graphite electrode made of carbon (C) or a metal itself can be used as the negative electrode.

[0081] For example, when the negative electrode is manufactured by coating the negative electrode slurry onto the negative electrode current collector, the negative electrode current collector typically 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. Examples of such a negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Furthermore, similar to the positive electrode current collector, the surface can be formed with fine irregularities to enhance the binding strength of the negative electrode active material, and the negative electrode current collector can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0082] The negative electrode active material may be natural graphite, artificial graphite, carbonaceous material, lithium-containing titanium composite oxide (LTO), Si, SiO x , Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe (Me); alloys composed of the above metals (Me); oxides of the above metals (Me) (MeO x and composites of the metals (Me) with carbon. Specific examples of the negative electrode active material include silicon (Si), silicon oxide (SiO x Silicon-based negative electrode active materials, such as silicon dioxide, silicon nitride, silicon carbide ...

[0083] The negative electrode active material may be contained in an amount of 60% by weight to 99% by weight, specifically 70% by weight to 99% by weight, more specifically 80% by weight to 98% by weight, based on the total weight of solids other than the solvent in the negative electrode slurry.

[0084] The binder is a component that helps bind the conductive material, active material, and current collector together. 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.

[0085] Typically, the binder may be contained in an amount of 1 wt % to 20 wt %, specifically 1 wt % to 15 wt %, more specifically 1 wt % to 10 wt %, based on the total weight of the solid content excluding the solvent in the negative electrode slurry.

[0086] The conductive material is a component for further improving the conductivity of the negative electrode active material. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include 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 fiber and metal fiber; 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.

[0087] The conductive material may be contained in an amount of 1 wt % to 20 wt %, specifically 1 wt % to 15 wt %, and more specifically 1 wt % to 10 wt %, based on the total weight of the solid content excluding the solvent in the negative electrode slurry.

[0088] 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 desired viscosity when containing the negative electrode active material, and optionally, a binder and a conductive material, etc. For example, the solvent may be included so that the concentration of solids including the negative electrode active material, and optionally, a binder and a conductive material, is 50 wt % to 95 wt %, specifically 70 wt % to 90 wt %.

[0089] When a metal is used as the anode, the anode can be fabricated by physically bonding, rolling, or depositing a metal thin film on the anode current collector or the metal thin film itself. The deposition method can be electrolytic deposition or chemical vapor deposition.

[0090] For example, the metal thin film itself or the metal bonded / rolled / deposited on 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).

[0091] (3) Solid electrolyte layer The solid electrolyte layer may further contain a binder in addition to the solid electrolyte according to the present invention.

[0092] The binder is a component that helps bind the conductive material, active material, and current collector together. 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.

[0093] Typically, the binder may be included in an amount of 1 wt % to 20 wt %, specifically 1 wt % to 15 wt %, and more specifically 1 wt % to 10 wt %, based on the total weight of the solid electrolyte layer.

[0094] The present invention provides a battery module including the all-solid-state battery as a unit cell, and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, excellent rate-limiting characteristics, and excellent cycle characteristics, and 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.

[0095] Specific examples will be presented below to facilitate understanding of the present invention. However, the examples are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description. It goes without saying that such changes and modifications fall within the scope of the appended claims.

[0096] 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 the dry mixing, rotating at a speed of 300 rpm to 70 rpm to ensure uniform mixing. The resulting mixed precursor was then heat-treated at 600°C for 12 hours to crystallize it, and then pulverized by ball milling to produce Li6PS5Cl with an argyrodite-type crystal structure. All of the above processes were carried out in an inert Ar atmosphere.

[0097] Examples and Comparative Examples Example 1 A mixture was prepared by dry mixing (ball milling) a polymer, PCTFE (Mw: 20,000 g / mol), with the Li6PS5Cl powder having an argyrodite-type crystal structure prepared in Preparation Example in a weight ratio of 5:95. A planetary ball mill equipped with zirconia balls was used for the dry mixing, and the mill was rotated at a speed of 100 to 200 rpm to ensure uniform mixing. The mixture was heat-treated at a temperature ranging from 180 to 250°C for 2 hours to form a polymer coating layer on the Li6PS5Cl particles having an argyrodite-type crystal structure. All of the above processes were carried out in an inert Ar atmosphere.

[0098] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing PCTFE was formed on Li6PS5Cl particles with an argyrodite-type crystal structure.

[0099] Example 2 A composite solid electrolyte in which a polymer coating layer containing PCTFE was formed on Li6PS5Cl particles having an argyrodite-type crystal structure was prepared in the same manner as in Example 1, except that PCTFE (Mw: 150,000 g / mol) was used instead of PCTFE (Mw: 20,000 g / mol) as the polymer.

[0100] Comparative Example 1 The Li6PS5Cl powder having an argyrodite-type crystal structure produced in Production Example was used as the solid electrolyte of Comparative Example 1.

[0101] Comparative Example 2 A composite solid electrolyte in which a polymer coating layer containing PTFE was formed on Li6PS5Cl particles having an argyrodite-type crystal structure was produced in the same manner as in Example 1, except that PTFE (Polytetrafluoroethylene) (manufactured by Sigma-Aldrich) was used as the polymer and heat treatment was carried out at 330°C for 2 hours.

[0102] Comparative Example 3 A composite solid electrolyte in which a polymer coating layer containing PDMS was formed on Li6PS5Cl particles having an argyrodite-type crystal structure was prepared in the same manner as in Example 1, except that PDMS (Silaplane FM-0725, manufactured by JNC Corp.) was used as the polymer.

[0103] Comparative Example 4 A composite solid electrolyte in which a polymer coating layer containing EVA was formed on Li6PS5Cl particles having an argyrodite-type crystal structure was prepared in the same manner as in Example 1, except that EVA (Ethylene-vinyl acetate copolymer) (manufactured by Sigma-Aldrich) was used as the polymer.

[0104] [Table 1]

[0105] Experimental Example 1: Initial ionic conductivity evaluation Immediately after the composite solid electrolyte powders of Examples 1 and 2 were prepared, 150 mg of each was placed in a 13 mm diameter SUS mold. The mold, along with the insulating PEEK, was attached to a press, and a potentiostat was connected to the SUS mold. After applying a pressure of 370 MPa to sufficiently densify the electrolyte structure, the pressure was slowly reduced to maintain 100 MPa, and AC impedance measurements were performed at frequencies from 1 Hz to 7 MHz. The ionic conductivity was calculated from the measured resistance using a Nyquist plot, and is shown in Table 2 below. All measurements were performed in a dry room at a temperature of 22°C and a relative humidity of 0.7%.

[0106] [Table 2]

[0107] Referring to Table 2, it can be seen that the composite solid electrolytes of Examples 1 and 2 according to the present invention have initial ionic conductivity at a level that allows a battery to be driven.

[0108] Experimental Example 2: Evaluation of hydrogen sulfide gas generation rate Five mg of each of the composite solid electrolytes of Examples 1 and 2, the solid electrolyte of Comparative Example 1, and the composite solid electrolyte powders of Comparative Examples 2 to 4 was taken and left for one hour or more in a glove box equipped with a hydrogen sulfide sensor (in a dry air atmosphere controlled at a relative humidity of 0.59%). Immediately after leaving the box, the amount of hydrogen sulfide generated per 1 g of composite solid electrolyte was calculated from the amount of hydrogen sulfide generated in one hour, and the results are shown in Table 3 below.

[0109] [Table 3]

[0110] Referring to Table 3, it can be seen that the composite solid electrolytes of Examples 1 and 2 according to the present invention generate less hydrogen sulfide, a toxic gas, than the solid electrolyte of Comparative Example. This confirms that the composite solid electrolytes of Examples 1 and 2 according to the present invention have better moisture stability.

[0111] Therefore, it can be seen that the composite solid electrolyte according to the present invention can inhibit the decomposition and degradation of sulfide-based solid electrolyte particles when exposed to moisture or oxygen because the polymer coating layer includes a polymer having a repeating unit represented by Formula I described herein. As a result, it can be seen that the composite solid electrolyte according to the present invention not only has excellent atmospheric stability itself, but also ensures process safety in both dry and wet processes when manufacturing a battery.

Claims

1. sulfide-based solid electrolyte particles; a polymer coating layer formed on the sulfide-based solid electrolyte particles, The polymer of the polymer coating layer comprises a repeating unit represented by the following chemical formula I: 【Chemical 1】 In the above formula I, X is F or Cl.

2. The composite solid electrolyte of claim 1 , wherein the polymer of the polymer coating layer comprises a repeating unit represented by the following Chemical Formula 1: 【Chemistry 2】

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

4. The composite solid electrolyte according to claim 1, wherein the polymer of the polymer coating layer has a weight average molecular weight (Mw) of 1,000 g / mol to 1,000,000 g / mol.

5. 2. 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 based on 100 parts by weight of the sulfide-based solid electrolyte particles.

6. 2. The composite solid electrolyte of claim 1, wherein the initial ionic conductivity is 0.001 mS / cm to 20 mS / cm.

7. When the composite solid electrolyte was exposed to an air atmosphere at a temperature of 25° C. and a relative humidity of 0.5% to 0.6%, hydrogen sulfide (H ) generated in the first hour was ２ S) is generated in an amount of 10 cm per 1 g of the composite solid electrolyte. ３ 2. The composite solid electrolyte of claim 1, wherein:

8. (A) preparing a mixture by mixing a polymer including a repeating unit represented by the following chemical formula I with a sulfide-based solid electrolyte; and (B) heat-treating the mixture at a temperature equal to or higher than the melting point of the polymer to form a polymer coating layer on the sulfide-based solid electrolyte particles. 【Chemistry 3】 In the above formula I, X is F or Cl.

9. The method for producing a composite solid electrolyte according to claim 8 , wherein the polymer comprises a repeating unit represented by the following Chemical Formula 1: 【Chemistry 4】

10. 9. The method for producing a composite solid electrolyte according to claim 8, wherein in step (A), the polymer is mixed in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the sulfide-based solid electrolyte.

11. The method for producing a composite solid electrolyte according to claim 8 , wherein the mixing is dry mixing.

12. The method for producing a composite solid electrolyte according to claim 8, wherein the heat treatment temperature is 180°C to 250°C.

13. An all-solid-state battery comprising the composite solid electrolyte according to any one of claims 1 to 7.

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