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

Abstract

The present invention aims to improve the atmospheric stability of a conventional sulfide-based solid electrolyte, 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, the polymer coating layer comprising a polymer having a weight average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25° C., the polymer of the polymer coating layer being a copolymer of a hydrophobic acrylate monomer and an acrylate monomer forming a polymer skeleton, the hydrophobic acrylate monomer containing an F element or an Si element or containing a hydrocarbon having 10 or more carbon atoms, and the acrylate monomer forming the polymer skeleton containing a hydrocarbon having 9 or less carbon atoms, and an all-solid-state battery including the same.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0026992 filed on March 2, 2022, and all the contents disclosed in the Korean patent application are incorporated herein by reference.

[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] As technology development and demand related to electric vehicles, as well as mobile devices, increase, the demand for secondary batteries as an energy source is rapidly increasing. Generally, a secondary battery includes a positive electrode, a negative electrode, an electrolyte positioned therebetween, and a separator. Currently, the most widely used secondary battery is a lithium secondary battery, which generally uses a liquid electrolyte as the electrolyte. However, the liquid electrolyte is vulnerable to heat and shock and has high flammability. Therefore, lithium secondary batteries have problems such as being damaged by external shocks or exploding due to temperature increases.

[0004] An all-solid-state battery is a battery that replaces the liquid electrolyte filling the space between the positive and negative electrodes of a conventional lithium secondary battery with a solid, has no risk of explosion, is safe, and has a higher energy density than conventional batteries, and is 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 be conducted and has a high ionic conductivity at the electrolyte level applicable to current lithium secondary batteries. Core materials constituting the solid electrolyte include polymers, sulfides, oxides, etc. Among them, sulfide-based solid electrolytes with high ductility and high ionic conductivity are evaluated as suitable for manufacturing high-capacity large batteries.

[0005] However, sulfide-based solid electrolytes have a high reactivity to moisture, reacting not only with moisture in the atmosphere but also with moisture under low humidity conditions, which generates the harmful gas hydrogen sulfide (H2S). This not only negatively impacts worker safety due to the toxic hydrogen sulfide, but also degrades the performance of the sulfide-based solid electrolyte itself. Therefore, there is a need to develop sulfide-based solid electrolytes with excellent atmospheric stability and chemical resistance. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-135947 [Patent Document 2] China Patent Publication Publication CN112701345A [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a composite solid electrolyte with improved atmospheric stability and chemical resistance. However, the problems that this invention aims to solve are not limited to those 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] To solve the above problems, the present invention provides a composite solid electrolyte and an all-solid-state battery. (1) The present invention comprises 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 weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25°C. The polymer in the polymer coating layer is a copolymer of a hydrophobic acrylate monomer and an acrylate monomer that forms the polymer backbone. The hydrophobic acrylate monomer contains element F or element Si, or contains a hydrocarbon with 10 or more carbon atoms. The acrylate monomer forming the polymer skeleton contains hydrocarbons with 9 or fewer carbon atoms, providing a composite solid electrolyte.

[0009] (2) In the present invention, the sulfide-based solid electrolyte provides the composite solid electrolyte described in (1) above, having a silver-germanium ore-type crystal structure.

[0010] (3) The present invention provides a composite solid electrolyte according to (1) or (2) above, wherein the hydrophobic acrylate monomer is one or more selected from polydimethylsiloxane (meth)acrylate, N-octadecyl (meth)acrylate, stearyl (meth)acrylate, and perfluorohexylethyl (meth)acrylate.

[0011] (4) The present invention provides a composite solid electrolyte according to any one of (1) to (3) above, wherein the acrylate monomer forming the backbone of the polymer is one or more selected from cyclohexyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, and iso-pentyl (meth)acrylate.

[0012] (5) In the present invention, the polymer of the polymer coating layer includes repeating units represented by the following chemical formula 1 and repeating units represented by the following chemical formula 2, providing a composite solid electrolyte according to any one of (1) to (4) above.

[0013] [ka]

[0014] In the above Chemical Formula 1, R1 is hydrogen; or an alkyl group having C1-C 10 and is an alkyl group of R2 is an alkyl group having C4-C containing a cyclic hydrocarbon 10 and is an alkyl group of

[0015] [Chemical Formula]

[0016] In the above Chemical Formula 2, R3 to R8 are each independently hydrogen; or an alkyl group having C1-C 10 and is an alkyl group of R9 is a direct bond; an alkylene group having C1-C 10 an alkenylene group having C2-C 10 an oxyalkylene group having C1-C 10 an arylene group having C6-C 30 or an oxyarylene group having C6-C 30 and is n is an integer of 1 or more.

[0017] (6) In the present invention, the polymer coating layer is contained in an amount of 0.1 part by weight to 10 parts by weight with respect to 100 parts by weight of the sulfide-based solid electrolyte particles, and provides the composite solid electrolyte according to any one of the above (1) to (5).

[0018] (7) The present invention provides the composite solid electrolyte according to any one of the above (1) to (6), having an ionic conductivity of 0.001 mS / cm or more.

[0019] (8) When the present invention exposes the composite solid electrolyte to an inert atmosphere, a temperature of 25°C, and a relative humidity of 0.5% to 0.6%, the generation rate of hydrogen sulfide (H2S) at the time point of 1 hour after the exposure is 10 cm per 1 g of the composite solid electrolyte 3The present invention provides a composite solid electrolyte according to any one of the above items (1) to (7), wherein the value is less than or equal to / h.

[0020] (9) The present invention provides an all-solid-state battery comprising a composite solid electrolyte as described in any one of the above (1) to (8). [Effects of the Invention]

[0021] 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 stable in the atmosphere, but its chemical resistance can also be improved during the wet process in battery manufacturing. [Modes for carrying out the invention]

[0022] The present invention will be described in more detail below to aid in understanding it. 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 appropriately define the concepts of terms in order to best explain 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” are intended to indicate the existence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0025] 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 weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25°C. The polymer in the polymer coating layer is a copolymer of a hydrophobic acrylate monomer and an acrylate monomer that forms the polymer backbone. The hydrophobic acrylate monomer contains element F or element Si, or contains a hydrocarbon with 10 or more carbon atoms, and the acrylate monomer that forms the polymer backbone contains a hydrocarbon with 9 or fewer carbon atoms.

[0026] 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 during battery manufacturing, thus completing the present invention.

[0027] The composite solid electrolyte according to the present invention contains a polymer coating layer having a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25°C, thereby suppressing the decomposition and degradation of sulfide-based solid electrolyte particles when exposed to moisture or oxygen. As a result, the generation of hydrogen sulfide, a toxic gas, can be suppressed, and the decrease in the ionic conductivity of the composite solid electrolyte can be prevented.

[0028] The polymer in the polymer coating layer is typically a polymer with high compatibility with the binder polymer of the battery, and is an acrylate monomer polymer. The polymer in the polymer coating layer is a copolymer of two or more acrylate monomers, and specifically, the polymer in the polymer coating layer is a copolymer of a hydrophobic acrylate monomer and an acrylate monomer that forms the polymer backbone.

[0029] More specifically, the polymer in the polymer coating layer may be a copolymer obtained by polymerizing a hydrophobic acrylate monomer and an acrylate monomer that forms the polymer backbone in a weight ratio of 1:99 to 10:90.

[0030] According to the present invention, the sulfide-based solid electrolyte may have a silver-germanium ore-type crystal structure in terms of high ionic conductivity and low reactivity with the lithium anode. The sulfide-based solid electrolyte may also 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 (In this case, A may be Cl, Br, I, Sn, or a combination thereof, and x may be 0 ≤ x ≤ 2.)

[0031] The polymer coating layer contains a polymer with a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol. Specifically, the weight-average molecular weight (Mw) of the polymer may be 5,000 g / mol to 200,000 g / mol, or more specifically, 10,000 g / mol to 100,000 g / mol. On the other hand, if the weight-average molecular weight (Mw) of the polymer is less than 5,000 g / mol, the amount of residual monomers that did not participate in the polymer polymerization reaction is high, and the moisture barrier effect is insufficient. If it exceeds 300,000 g / mol, the contact between sulfide-based solid electrolyte particles decreases, and the ionic conductivity may decrease.

[0032] The polymer in the polymer coating layer may have a contact angle with water of 100° or more at 25°C, specifically 100° to 170°, or more specifically 110° to 170°. In this case, the water-repellent performance of the composite solid electrolyte can be excellent.

[0033] The hydrophobic acrylate monomer may contain an element F or an element Si that can impart water-repellent properties, or it may contain a hydrocarbon with 10 or more carbon atoms. The hydrophobic acrylate monomer may be a fluorine-containing (meth)acrylate monomer, a silicon-containing (meth)acrylate monomer, and C 10 -C 20 It may be one or more hydrocarbon-containing (meth)acrylate monomers selected from the following. In this case, (meth)acrylate means methacrylate or acrylate. And C 10 -C 20 The hydrocarbons may be linear or branched chain hydrocarbons; cyclic hydrocarbons; or hydrocarbons in which both linear or branched chains and rings exist simultaneously.

[0034] Specifically, the hydrophobic acrylate monomer may be one or more selected from polydimethylsiloxane (meth)acrylate, N-octadecyl (meth)acrylate, stearyl (meth)acrylate, and perfluorohexylethyl (meth)acrylate. More specifically, the acrylate monomer may be polydimethylsiloxane (meth)acrylate, for example, α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane.

[0035] The acrylate monomers forming the backbone of the polymer are monomers forming the main chain of the polymer and may contain hydrocarbons with 9 or fewer carbon atoms. The acrylate monomers forming the backbone of the polymer may also be C1-C9 hydrocarbon-containing (meth)acrylate monomers. In this case, (meth)acrylate means methacrylate or acrylate. The C1-C9 hydrocarbons may be linear or branched chain hydrocarbons; cyclic hydrocarbons; or hydrocarbons in which both linear or branched chains and rings exist simultaneously.

[0036] Specifically, the acrylate monomers forming the backbone of the polymer may be one or more selected from cyclohexyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, and iso-pentyl (meth)acrylate.

[0037] The polymer in the polymer coating layer may be, for example, a copolymer of polydimethylsiloxane-based (meth)acrylate and cyclohexyl (meth)acrylate, and more specifically, a copolymer obtained by polymerizing polydimethylsiloxane-based (meth)acrylate and cyclohexyl (meth)acrylate in a weight ratio of 1:99 to 10:90.

[0038] 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.

[0039] [ka]

[0040] In the aforementioned chemical formula 1, R1 is hydrogen; or C1-C 10 It is an alkyl group, R2 is a C4-C containing cyclic hydrocarbons. 10 It is an alkyl group,

[0041] [ka]

[0042] In the aforementioned chemical formula 2, R3~R8 are each independently hydrogen; or C1-C 10 It is an alkyl group, R9 is a direct bond; C1-C10 alkylene group; C2-C 10 alkenylene group; C1-C 10 oxyalkylene group; C6-C 30 Arylene group of; or C6-C 30 It is an oxyarylene group, n is an integer greater than or equal to 1. In the repeating units represented by chemical formulas 1 and 2, * represents a portion that binds to other repeating units.

[0043] The polymer may contain repeating units represented by chemical formula 1 and repeating units represented by chemical formula 2 in a ratio of 1:99 to 10:90 in order to improve the moisture barrier effect and minimize the decrease in ionic conductivity.

[0044] 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 is improved, and the decrease in ionic conductivity can be minimized.

[0045] According to the present invention, the composite solid electrolyte may have an ionic conductivity of 0.001 mS / cm or higher, specifically 0.001 mS / cm to 20 mS / cm, more specifically 0.01 mS / cm to 10 mS / cm, or 0.01 mS / cm to 5 mS / cm. A higher ionic conductivity of the electrolyte is preferable, but 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. The ionic conductivity can be measured in a dry room at a temperature of 22°C and a relative humidity of 0.7%.

[0046] According to the present invention, when the composite solid electrolyte is exposed to an inert atmosphere, a temperature of 25°C, and a relative humidity of 0.5% to 0.6%, the hydrogen sulfide (H2S) generation rate at 1 hour after exposure is 10 cm³ per gram of the composite solid electrolyte. 3The rate may be less than or equal to / h. In other words, the composite solid electrolyte according to the present invention has excellent moisture stability, a low rate of decrease in ionic conductivity after exposure to moisture, generates little hydrogen sulfide (a toxic gas), generates it slowly, and ensures process safety.

[0047] When the composite solid electrolyte is exposed to an inert atmosphere, 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 10 cm³ per gram of the composite solid electrolyte. 3 The following is also acceptable.

[0048] The composite solid electrolyte according to the present invention can be manufactured by coating sulfide-based solid electrolyte particles with a polymer composition containing polymers having a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol.

[0049] 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 stoichiometry 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.

[0050] The aforementioned polymers with a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol can be produced by polymerizing the aforementioned acrylate monomers using methods such as suspension polymerization, solution polymerization, and bulk polymerization. For example, the aforementioned acrylate monomers, along with selectively chain transfer agents, dispersants, and thermal initiators, can be dispersed in a solvent, and then the polymer can be produced by suspension polymerization while mixing with a stirrer.

[0051] The polymer composition can be produced by dissolving or dispersing a polymer having a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol in a solvent such as toluene or xylene. In this case, the weight ratio of the polymer having a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol to the solvent such as toluene or xylene may be 1:2 to 2:1.

[0052] Finally, the coating may be carried out by a step of mixing and stirring the polymer composition and the sulfide-based solid electrolyte and then drying, or by spraying the polymer composition onto the sulfide-based solid electrolyte and then drying. However, it may also be carried out by methods known in the industry.

[0053] All solid state battery The present invention provides an all-solid-state battery containing the composite solid electrolyte. 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 a composite solid electrolyte according to the present invention, disposed between the positive electrode and the negative electrode.

[0054] The all-solid-state battery according to the present invention exhibits less reduction in ionic conductivity due to moisture, and can provide excellent initial efficiency, lifespan characteristics, and output characteristics. In this case, 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 and pressurizing such that a solid electrolyte layer exists between the positive electrode and the negative electrode.

[0055] (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.

[0056] 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. may be used. Further, fine irregularities may be formed on the surface to strengthen the binding force of the positive electrode active material, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc.

[0057] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (for example, LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (for example, LiCoO2, etc.), a lithium-nickel-based oxide (for example, LiNiO2, etc.), a lithium-nickel-manganese-based oxide (for example, 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 (for example, LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (for example, 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 (for example, 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, and p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (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 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 more of these compounds may be included.

[0058] Among them, in terms of improving the capacity characteristics and safety 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[[ID=二十三]] 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn[[ID=三十三]] 0.15 Co[[ID=三十五]] 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co[[ID=四十一]] 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 according to the control of 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 0.2 Co 0.2 )O2, Li(Ni 0.5 [[ID=5十六]]Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )This could also be O2, or one or more of these, or a mixture of two or more.

[0059] The positive electrode active material may be present in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0060] The 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.

[0061] Typically, the binder may 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, based on the total weight of the solids in the cathode slurry excluding the solvent.

[0062] The aforementioned conductive material is a component that further improves the conductivity of the positive electrode active material. 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 may be used.

[0063] Typically, the conductive material may 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, based on the total weight of the solid matter in the positive electrode slurry excluding the solvent.

[0064] The solvent may include organic solvents such as NMP (N-methyl-2-pyrrolidone) and may be used in an amount that results in a desirable viscosity when the positive electrode active material and selectively include binders and conductive materials. For example, the concentration of solids containing the positive electrode active material and selectively including binders and conductive materials may be 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0065] (2) Negative electrode The negative electrode may be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent onto a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself may be used as the negative electrode.

[0066] 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 surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. Also, similar to the positive electrode current collector, fine irregularities may be formed on the surface to strengthen the bonding force of the negative electrode active material, and it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0067] The aforementioned 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 x ), or silicon-based negative electrode active materials including silicon alloy may be used. In this case, a thin and stable SEI layer containing siloxane bonds is formed, which can further improve the high-temperature stability and lifespan characteristics of the battery.

[0068] The negative electrode active material may be present in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight, based on the total weight of the solid content excluding the solvent in the negative electrode slurry.

[0069] The 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.

[0070] Typically, the binder may 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, based on the total weight of the solids in the negative electrode slurry excluding the solvent.

[0071] 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, and may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0072] The conductive material may 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, based on the total weight of the solids in the negative electrode slurry excluding the solvent.

[0073] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that results in a desirable viscosity when the negative electrode active material and selectively include binders and conductive materials. For example, the concentration of the solids containing the negative electrode active material and selectively including binders and conductive materials may be 50% to 95% by weight, preferably 70% to 90% by weight.

[0074] When using a metal itself as the negative electrode, the metal can be manufactured by physically joining, rolling, or vapor deposition of the metal thin film itself or onto the negative electrode current collector. The vapor deposition method may involve electro-vapor deposition or chemical vapor deposition.

[0075] For example, the metal bonded / rolled / deposited onto the metal thin film itself or 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).

[0076] (3) Solid electrolyte layer The solid electrolyte layer may further contain a binder in addition to the solid electrolyte according to the present invention.

[0077] The 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.

[0078] Typically, the binder may 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, based on the total weight of the solid electrolyte layer.

[0079] The present invention provides a battery module and a battery pack containing the all-solid-state battery as a unit cell. Because the battery module and 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 devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Examples]

[0080] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative examples 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 present description and the technical concept, and it goes without saying that such variations and modifications fall within the scope of the appended claims.

[0081] Manufacturing example Three precursors, Li2S, P2S5, and LiCl, were dry-mixed (ball-milled) in a molar ratio of 5:1:2. During dry mixing, a planetary ball mill equipped with zirconia balls was used, and the mixture was rotated at a speed of over 300 rpm to ensure uniform mixing. The resulting mixed precursor was then heat-treated at 600°C for 12 hours to crystallize, and subsequently pulverized again by ball-milling to produce Li6PS5Cl having a silver-germanium ore-type crystal structure. All of the above processes were carried out under an inert Ar atmosphere.

[0082] Examples and Comparative Examples Example 1 95 parts by weight of cyclohexyl methacrylate (TCI), 5 parts by weight of α-butyl-ω-(3-methacryloxypropyl) polydimethylsiloxane (JNC, Silaplane FM-0721) (Mw: 5,000 g / mol), and 0.6 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer A (Mw: 45,000 g / mol, contact angle with water at 25°C: 107°). A polymer composition was prepared by dissolving 5 parts by weight of copolymer A in 100 parts by weight of xylene.

[0083] The polymer composition and Li6PS5Cl having a silver-germanium ore-type 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 a silver-germanium ore-type crystal structure.

[0084] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 45,000 g / mol and a contact angle with water of 107° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0085] Example 2 95 parts by weight of cyclohexyl methacrylate (TCI), 5 parts by weight of α-butyl-ω-(3-methacryloxypropyl) polydimethylsiloxane (JNC, Silaplane FM-0721) (Mw: 5,000 g / mol), and 3.7 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer B (Mw: 13,000 g / mol, contact angle with water at 25°C: 108°).

[0086] A polymer composition was prepared in the same manner as in Example 1, except that copolymer B was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0087] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 13,000 g / mol and a contact angle with water of 108° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0088] Example 3 95 parts by weight of cyclohexyl methacrylate (TCI), 5 parts by weight of α-butyl-ω-(3-methacryloxypropyl) polydimethylsiloxane (JNC, Silaplane FM-0721) (Mw: 5,000 g / mol), and 0.3 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer C (Mw: 86,000 g / mol, contact angle with water at 25°C: 107°).

[0089] A polymer composition was prepared in the same manner as in Example 1, except that copolymer C was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0090] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 86,000 g / mol and a contact angle with water of 107° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0091] Comparative Example 1 In Comparative Example 1, Li6PS5Cl, which has a silver-germanium ore-type crystal structure and was produced in the manufacturing example, was used as the solid electrolyte.

[0092] Comparative Example 2 100 parts by weight of cyclohexyl methacrylate (TCI) and 0.6 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce polymer D (Mw: 45,000 g / mol, contact angle with water at 25°C: 89°).

[0093] A polymer composition was prepared in the same manner as in Example 1, except that polymer D was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0094] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 45,000 g / mol and a contact angle with water of 89° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0095] Comparative Example 3 95 parts by weight of cyclohexyl methacrylate (TCI), 5 parts by weight of α-butyl-ω-(3-methacryloxypropyl) polydimethylsiloxane (JNC, Silaplane FM-0721) (Mw: 5,000 g / mol), and 0.05 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer E (Mw: 310,000 g / mol, contact angle with water at 25°C: 107°).

[0096] A polymer composition was prepared in the same manner as in Example 1, except that copolymer E was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0097] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 310,000 g / mol and a contact angle with water of 107° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0098] Comparative Example 4 95 parts by weight of cyclohexyl methacrylate (TCI), 5 parts by weight of α-butyl-ω-(3-methacryloxypropyl) polydimethylsiloxane (JNC, Silaplane FM-0721) (Mw: 5,000 g / mol), and 10 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer F (Mw: 4,500 g / mol, contact angle with water at 25°C: 97°). For reference, during the polymerization of copolymer F, the polymerization stability of α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane decreased, and NMR analysis confirmed the presence of 4.4 parts by weight of unreacted α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane (88% by weight based on the initial content of α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane).

[0099] A polymer composition was prepared in the same manner as in Example 1, except that copolymer F was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0100] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 4,500 g / mol and a contact angle with water of 97° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0101] Comparative Example 5 100 parts by weight of methyl methacrylate (Junsei Chemical Co., Ltd.) and 0.6 parts by weight of n-dodecyl mercaptan as a chain transfer agent were dispersed in 187 parts by weight of water. Suspension polymerization was carried out at 75°C for 3 hours while mixing with a stirrer to produce copolymer G (Mw: 44,000 g / mol, contact angle with water at 25°C: 69°).

[0102] A polymer composition was prepared in the same manner as in Example 1, except that copolymer G was used instead of copolymer A, and a polymer coating layer was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0103] As a result, a composite solid electrolyte was obtained in which a polymer coating layer containing a polymer having a weight-average molecular weight (Mw) of 44,000 g / mol and a contact angle with water of 69° at 25°C was formed on Li6PS5Cl particles having a silver-germanium ore-type crystal structure.

[0104] [Table 1]

[0105] 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 2-5 were placed in a 13 mm diameter SUS mold. With the mold attached to a press machine along with insulating PEEK, Potentiostat was connected to the SUS mold. After pressurizing at 370 MPa to sufficiently densify the electrolyte structure, the pressure was gradually 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 22°C and a relative humidity of 0.7%.

[0106] 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 2-5 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 at 25°C and 0.59% relative humidity). The hydrogen sulfide generation rate per gram of composite solid electrolyte was calculated from the amount of hydrogen sulfide generated after one hour. The hydrogen sulfide generation rates are shown in Table 2 below.

[0107] [Table 2]

[0108] The composite solid electrolytes of Examples 1 to 3 possess ionic conductivity suitable for use as an electrolyte, and it can be confirmed that the rate of generation of hydrogen sulfide, a toxic gas, is remarkably slow.

[0109] In contrast, the composite solid electrolytes of Comparative Examples 2 and 5 have low hydrophobicity, with contact angles to water of 89° and 69°, respectively, and it can be confirmed that their moisture-blocking effect is reduced. Furthermore, it can be confirmed that the composite solid electrolyte of Comparative Example 3 has a high molecular weight of the polymer, resulting in a thick and non-uniformly formed coating layer, which not only has low ionic conductivity but also a reduced moisture-blocking effect. Finally, it can be confirmed that the composite solid electrolyte of Comparative Example 4 has a polymer molecular weight that is too low, leading to reduced polymerization stability during the manufacturing process, a high amount of residual monomers that did not participate in the polymer polymerization reaction, and insufficient moisture-blocking effect.

[0110] As a result, it is found that the composite solid electrolyte according to the present invention has a polymer coating layer on the sulfide-based solid electrolyte particles that has a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25°C (a copolymer of a hydrophobic acrylate monomer (containing element F or element Si, or a hydrocarbon with 10 or more carbon atoms) and an acrylate monomer (containing a hydrocarbon with 9 or fewer carbon atoms) that forms the polymer backbone), has ionic conductivity suitable for use as an electrolyte, and can prevent the sulfide-based solid electrolyte particles from decomposing and degrading.

Claims

1. Sulfide-based solid electrolyte particles, A polymer coating layer formed on the sulfide-based solid electrolyte particles, Includes, The polymer coating layer contains a polymer having a weight-average molecular weight (Mw) of 5,000 g / mol to 300,000 g / mol and a contact angle with water of 100° or more at 25°C. The polymer in the polymer coating layer is a copolymer of a hydrophobic acrylate monomer and an acrylate monomer that forms the polymer backbone. The hydrophobic acrylate monomer contains the element Si, The acrylate monomer that forms the backbone of the polymer contains hydrocarbons with 9 or fewer carbon atoms. The polymer in the polymer coating layer is a composite solid electrolyte comprising repeating units represented by the following chemical formula 1 and repeating units represented by the following chemical formula 2. 【Chemistry 1】 In the aforementioned chemical formula 1, R １ is hydrogen; or C １ -C １０ It is an alkyl group, R ２ C, which contains cyclic hydrocarbons ４ -C １０ It is an alkyl group, 【Chemistry 2】 In the aforementioned chemical formula 2, R ３ ~R ８ are each independently hydrogen; or a C １ -C １０ alkyl group, R ９ Direct bond; C １ -C １０ The alkylene group; C ２ -C １０ The alkenylene group of C １ -C １０ oxyalkylene group; C ６ -C ３０ The arylene group of; or C ６ -C ３０ It is an oxyarylene group, n is an integer greater than or equal to 1.

2. The composite solid electrolyte according to claim 1, wherein the sulfide-based solid electrolyte has a silver-germanium ore-type crystal structure.

3. The hydrophobic acrylate monomer is a polydimethylsiloxane-based (meth)acrylate, as described in claim 1.

4. The composite solid electrolyte according to claim 1, wherein the acrylate monomer forming the backbone of the polymer is one or more selected from cyclohexyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, and iso-pentyl (meth)acrylate.

5. 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.

6. The composite solid electrolyte according to claim 1, wherein the ionic conductivity is 0.001 mS / cm or higher.

7. When the composite solid electrolyte was exposed to an inert atmosphere, a temperature of 25°C, and a relative humidity of 0.5% to 0.6%, the amount of hydrogen sulfide (H) at 1 hour after exposure was ２ The generation rate of S) is 10 cm per gram of the composite solid electrolyte. ３ The composite solid electrolyte according to claim 1, wherein the value is less than or equal to / h.

8. A solid-state battery comprising a composite solid electrolyte according to any one of claims 1 to 7.

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