Solid electrolyte composition, solid electrolyte membrane containing the same, and all-solid-state battery

Abstract

The present invention includes a solid electrolyte, a binder, a solvent, and a dispersant, The present invention relates to a solid electrolyte composition for an all-solid-state battery, wherein the dispersant is a carboxylic acid compound having a weight-average molecular weight of 1,000 to 5,000, a solid electrolyte membrane produced from the composition, and an all-solid-state battery including the composition.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0078642 dated June 20, 2023, and incorporates all the contents disclosed in the said Korean Patent Application as part of this Specification.

[0002] This invention relates to a solid electrolyte composition, a solid electrolyte membrane containing the same, and an all-solid-state battery. [Background technology]

[0003] From the perspectives of battery capacity, safety, output, scaling up, and miniaturization, various types of batteries are currently being researched that can overcome the limitations of lithium-ion secondary batteries.

[0004] Typically, metal-air batteries, which have a much larger theoretical capacity than lithium-ion batteries; all-solid-state batteries, which pose no risk of explosion in terms of safety; supercapacitors, which offer high output; NaS batteries or RFB (redox flow batteries), which are designed for larger sizes; and thin-film batteries, which are designed for ultra-miniaturization, are among the technologies that are being continuously researched in academia and industry.

[0005] All-solid-state batteries are batteries that replace the liquid electrolyte used in conventional lithium-ion secondary batteries with a solid electrolyte. Because they do not use flammable solvents within the battery, there is no risk of ignition or explosion due to the decomposition reaction of conventional electrolytes, thus significantly improving safety. Furthermore, because lithium (Li) metal or lithium alloy can be used as the negative electrode material, there is an advantage in that the energy density relative to the mass and volume of the battery can be dramatically improved.

[0006] To improve the energy density of all-solid-state batteries, it is essential to fabricate a solid electrolyte membrane. The solid electrolyte membrane can be manufactured by dispersing a solid electrolyte in a solvent to produce a slurry-like solid electrolyte composition, then applying the solid electrolyte composition to one side of a release film, drying it, and finally removing the release film. To obtain a solid electrolyte membrane with a uniform thickness, it is extremely important to improve the dispersibility of the solid electrolyte within the solid electrolyte composition, which is also closely related to the performance of all-solid-state batteries. If the dispersion of the solid electrolyte within the solid electrolyte composition is not sufficiently carried out, there is a possibility that the uniformity of the thickness of the solid electrolyte membrane will decrease, thereby deteriorating the performance of all-solid-state batteries.

[0007] Therefore, there is a need for research on solid electrolyte compositions for all-solid-state batteries that can improve the dispersibility of solid electrolytes.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] To solve the above problems, the inventors conducted extensive research. As a result, it was confirmed that when a carboxylic acid compound with a weight average molecular weight of 1000 to 5000 is used as a dispersant in a solid electrolyte composition for all-solid-state batteries, the phenomenon of solid electrolyte aggregation within the composition can be suppressed, and the dispersibility can be improved, thus completing the present invention.

[0010] Therefore, an object of the present invention is to provide a solid electrolyte composition for all-solid-state batteries that can improve the dispersibility of solid electrolytes.

[0011] Furthermore, an object of the present invention is to provide a solid electrolyte membrane with uniform thickness and high ionic conductivity by manufacturing a solid electrolyte membrane using the solid electrolyte composition described above.

[0012] Furthermore, an object of the present invention is to provide an all-solid-state battery with excellent lifespan characteristics by including the solid electrolyte membrane. [Means for solving the problem]

[0013] In order to achieve the aforementioned objective, The present invention comprises a solid electrolyte, a binder, and a dispersant. The present invention provides a solid electrolyte composition for all-solid-state batteries, wherein the dispersant is a carboxylic acid compound having a weight-average molecular weight of 1000 to 5000.

[0014] Furthermore, the present invention provides a solid electrolyte membrane for an all-solid-state battery manufactured using the solid electrolyte composition for all-solid-state batteries of the present invention.

[0015] Furthermore, the present invention is an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between them. The present invention provides an all-solid-state battery in which the solid electrolyte membrane is the solid electrolyte membrane of the present invention. [Effects of the Invention]

[0016] The solid electrolyte composition for all-solid-state batteries of the present invention can suppress the phenomenon of solid electrolyte aggregation within the composition and improve dispersibility.

[0017] Furthermore, a solid electrolyte membrane produced using the solid electrolyte composition for all-solid-state batteries of the present invention can have the effect of having a uniform thickness and high ionic conductivity.

[0018] Furthermore, the all-solid-state battery containing the solid electrolyte membrane of the present invention can have excellent performance. [Brief explanation of the drawing]

[0019] [Figure 1]This is a graph showing the dispersion particle size distribution of the solid electrolyte in the solid electrolyte composition for all-solid-state batteries in Experimental Example 1. [Figure 2] This is a graph showing the life characteristics of the all-solid-state battery in Experimental Example 3. [Modes for carrying out the invention]

[0020] The present invention will be described in more detail below.

[0021] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their inventions.

[0022] The terms used in this invention are used solely to describe specific embodiments and are not intended to limit the invention. A singular expression includes plural expressions unless the context clearly indicates otherwise. In this invention, terms such as “includes” or “having” are intended to specify the existence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification, and should not be understood to preemptively exclude the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0023] Solid electrolyte composition for all solid-state batteries The present invention relates to a solid electrolyte composition for all-solid-state batteries. The solid electrolyte composition for all-solid-state batteries comprises a solid electrolyte, a binder, and a dispersant. The dispersant may be a carboxylic acid compound having a weight-average molecular weight (Mw) of 1000 to 5000.

[0024] Conventional solid electrolyte compositions for all-solid-state batteries do not contain a dispersant, which leads to the aggregation of the solid electrolyte within the composition. When the solid electrolyte aggregates in this way, the particle size of the dispersed solid electrolyte increases within the solid electrolyte composition for all-solid-state batteries. When the particle size of the dispersed solid electrolyte increases, the thickness of the solid electrolyte film for all-solid-state batteries manufactured using the solid electrolyte composition becomes uneven, which leads to a problem of reduced performance in all-solid-state batteries containing it.

[0025] The solid electrolyte composition for all-solid-state batteries of the present invention uses a carboxylic acid compound with a weight-average molecular weight of 1000 to 5000 as a dispersant, thereby suppressing the aggregation of the solid electrolyte within the composition, improving the dispersibility of the solid electrolyte, and achieving excellent solubility in the solvent. This makes it possible to provide a solid electrolyte membrane for all-solid-state batteries with uniform thickness and excellent ionic conductivity.

[0026] If the carboxylic acid compound is not used, the dispersibility of the solid electrolyte may decrease. Therefore, it is preferable to use the carboxylic acid compound as a dispersant to improve the dispersibility of the solid electrolyte. Furthermore, if the weight-average molecular weight of the carboxylic acid compound is less than 1000, while its solubility in the solvent is excellent, its ability to control aggregation in the solid electrolyte is poor, which may cause the solid electrolyte to aggregate. Conversely, if the weight-average molecular weight of the carboxylic acid compound exceeds 5000, while its ability to control aggregation in the solid electrolyte is excellent, its solubility in the solvent may be poor. This may result in the production of a solid electrolyte membrane for all-solid-state batteries with uneven thickness, potentially degrading the performance of all-solid-state batteries containing such membranes.

[0027] The dispersant may contain one or more selected from the group consisting of glycolic acid ethoxylate lauryl ether, glycolic acid ethoxylate oleyl ether, and glycolic acid ethoxylate 4-tert-butylphenyl ether.

[0028] The dispersant may be present in an amount of 0.1 to 2% by weight, preferably 0.1 to 0.7% by weight, relative to the total weight of the solid electrolyte composition for the all-solid-state battery. Within this range, the dispersibility of the solid electrolyte can be improved. If the dispersant is present in an amount of less than 0.1% by weight, the effect of improving the dispersibility of the solid electrolyte cannot be expected, and if it is present in an amount exceeding 2% by weight, the content of the solid electrolyte will decrease, which may lead to a problem of reduced performance of the all-solid-state battery.

[0029] The solid electrolyte composition for all-solid-state batteries of the present invention, by containing the aforementioned dispersant, can improve the dispersibility of the solid electrolyte within the solid electrolyte composition and suppress the phenomenon of aggregation. Therefore, the solid electrolyte within the solid electrolyte composition for all-solid-state batteries can exist without aggregation.

[0030] The particle size D50 of the solid electrolyte may be 0.5 to 1.5 μm, and the particle size D99 may be 3 to 5 μm. Preferably, the particle size D50 is 0.6 to 1.1 μm and the particle size D99 is 3 to 4 μm.

[0031] The dispersion particle size D50 of the solid electrolyte in the solid electrolyte composition for all-solid-state batteries may be 0.5 to 1.5 μm, and the dispersion particle size D99 may be 3 to 5 μm. More specifically, when a solid electrolyte having a particle size D50 of 0.5 to 1.5 μm and a particle size D99 of 3 to 5 μm is used as a solid electrolyte composition for all-solid-state batteries, the dispersion particle size D50 of the solid electrolyte in the solid electrolyte composition for all-solid-state batteries may be 0.5 to 1.5 μm, and the dispersion particle size D99 may be 3 to 5 μm. In other words, the particle size of the solid electrolyte before dispersion and the dispersion particle size of the solid electrolyte after dispersion may be the same. Therefore, the solid electrolyte can exist in a dispersed form without the phenomenon of aggregation occurring within the solid electrolyte composition for all-solid-state batteries.

[0032] In this specification, dispersion particle size may mean the particle size of the solid electrolyte dispersed in a solid electrolyte composition for all-solid-state batteries.

[0033] If the solid electrolyte composition for all-solid-state batteries does not contain a dispersant, or if the weight-average molecular weight of the carboxylic acid compound used as a dispersant is less than 1000 or exceeds 5000, then a solid electrolyte with a particle size D99 of 3 to 5 μm may have a dispersed particle size D99 of more than 5 μm within the solid electrolyte composition for all-solid-state batteries. In other words, the effect of improving the dispersibility of the solid electrolyte cannot be obtained, and the phenomenon of solid electrolyte aggregation may occur. However, if the dispersant contains a carboxylic acid compound with a weight-average molecular weight of 1000 to 5000, the particle size of the solid electrolyte and the dispersed particle size of the solid electrolyte within the solid electrolyte composition for all-solid-state batteries may be the same. That is, by including the aforementioned dispersant, the solid electrolyte composition for all-solid-state batteries of the present invention can suppress the phenomenon of solid electrolyte aggregation within the solid electrolyte composition for all-solid-state batteries and improve dispersibility. In other words, the solid electrolyte can be dispersed well without aggregation within the solid electrolyte composition for all-solid-state batteries and maintain its particle size. Therefore, the particle size of the solid electrolyte and the dispersed particle size may be within the same or similar range.

[0034] Therefore, the dispersion particle size (D99) / dispersion particle size (D50) of the solid electrolyte in the solid electrolyte composition for the all-solid-state battery may be 2 to 7, preferably 3 to 6.

[0035] The solid electrolyte may include one or more selected from the group consisting of sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes, and preferably includes a sulfide-based solid electrolyte.

[0036] The sulfide-based solid electrolyte contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS glass or Li-PS glass ceramic.

[0037] Specifically, the sulfide-based solid electrolyte may contain one or more selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS, and preferably contains one or more selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The Li6PS5Cl, Li6PS5Br, and Li6PS5I mentioned above may be argyrodite-type solid electrolytes. Furthermore, the sulfide-based solid electrolyte may be in a form doped with trace amounts of elements; for example, Li6PS5Cl may be further doped with bromine (Br).

[0038] The aforementioned polymer solid electrolyte is a composite of a lithium salt and a polymer resin, that is, a polymer electrolyte material formed by adding a polymer resin to a solvated lithium salt, and is approximately 1 x 10⁻⁶ -7 S / cm or more, preferably about 1 x 10 -5It can exhibit an ionic conductivity of 1 S / cm or more.

[0039] Non-limiting examples of the polymer resin include polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, etc., and one or more of these may be included. Further, as the polymer resin of the polymer electrolyte, branched copolymers obtained by copolymerizing amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene as comonomers on a PEO (polyethylene oxide) main chain, comb-like polymer resins, crosslinked polymer resins, etc. can be cited as examples, and one or more of these may be included.

[0040] In the polymer solid electrolyte, the aforementioned lithium salt is an ionizable lithium salt and can be represented by Li + X - Although not particularly limited, examples of anions of such lithium salts include F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - [[ID=3​​​​​​​​​​​​​​(CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , (CF3CF2SO2)2N - Examples include the following.

[0041] The oxide-based solid electrolyte may contain oxygen (O) and have the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. For example, LLTO compounds, Li6La2CaTa2O 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (Here, 0≦x≦1, 0≦y≦1), LiAl x Zr 2-x (PO4)3 (where 0≦x≦1, 0≦y≦1), LiTi x Zr 2-x (PO4)3 (where 0≦x≦1, 0≦y≦1), may contain one or more compounds selected from LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0042] The solid electrolyte may be present in an amount of 95 to 99% by weight relative to the total weight of the solid electrolyte composition for all-solid-state batteries.

[0043] The type of binder mentioned above is not particularly limited, as long as it is used in this industry.

[0044] For example, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), styrene-butadiene-styrene copolymer (SBS), polybutadiene (PAN), styrene-ethylene / butylene-styrene block copolymer (SEBS), silicone rubber (SR), hydrogenated nitrile butadiene rubber (HNBR), poly(ethylene vinyl acetate) (PEVA), poly(methyl methacrylate) (PMMA), polyisobutene (PIB), polyacrylate, etc. may be used, but are not limited to these. In the present invention, the use of styrene-butadiene-styrene copolymer may be preferred.

[0045] The binder may be present in an amount of 0.5 to 5% by weight relative to the total weight of the solid electrolyte composition for the all-solid-state battery.

[0046] The solid electrolyte composition for all-solid-state batteries of the present invention may be in the form of a slurry in which a solid electrolyte, a binder, and a dispersant are dispersed in a solvent.

[0047] The solvent is not particularly limited in type, as long as it can disperse the solid electrolyte, binder, and dispersant. For example, xylene, hexane, benzene, anisole, isobutyl isobutyrate, toluene, and butyl butyrate can be used.

[0048] Solid electrolyte membrane for all-solid-state batteries Furthermore, the present invention relates to a solid electrolyte membrane for an all-solid-state battery manufactured using the solid electrolyte composition for all-solid-state batteries of the present invention described above.

[0049] The solid electrolyte membrane for the all-solid-state battery can be manufactured by applying the solid electrolyte composition for the all-solid-state battery to one surface of a release film, drying it, and then removing the release film.

[0050] The solid electrolyte composition for all-solid-state batteries exhibits excellent dispersibility, with the solid electrolyte not agglomerating within the composition. Therefore, when a solid electrolyte membrane for all-solid-state batteries is manufactured using the solid electrolyte composition, a membrane with uniform thickness and excellent ionic conductivity can be produced. In the present invention, the thickness of the solid electrolyte membrane for all-solid-state batteries may be 20 to 50 μm. Furthermore, the ionic conductivity of the solid electrolyte membrane for all-solid-state batteries is 1.3 x 10⁻¹⁰. -3 The ionic conductivity may be greater than or equal to S / cm. The ionic conductivity may be measured at room temperature (25°C).

[0051] All solid state battery Furthermore, the present invention relates to an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between them, wherein the solid electrolyte membrane may be the solid electrolyte membrane for the all-solid-state battery of the present invention described above.

[0052] The all-solid-state battery is a lithium secondary battery, and there are no restrictions on whether it is a positive or negative electrode. It may be a lithium-air battery, a lithium oxide battery, a lithium-sulfur battery, or a lithium metal battery.

[0053] The positive electrode may include a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector.

[0054] The positive electrode current collector is for supporting the positive electrode active material layer and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery. For example, the positive electrode current collector may be any one metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver. As the alloy, an aluminum-cadmium alloy may be preferably used. Other materials such as calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may also be used.

[0055] The positive electrode current collector can have fine irregularities formed on its surface to strengthen its bonding force with the positive electrode active material, and may be used in various forms such as film, sheet, foil, mesh, net, porous material, foam, nonwoven fabric, etc.

[0056] The positive electrode active material layer may selectively contain a positive electrode active material, a conductive material, and a binder.

[0057] The positive electrode active material may vary depending on the type of all-solid-state battery. For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (0 ≤ x ≤ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (M=Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≦x≦0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxide represented as O2 (M=Co, Ni, Fe, Cr, Zn, or Ta; 0.01≦x≦0.1) or Li2Mn3MO8 (M=Fe, Co, Ni, Cu, or Zn); LiNi x Mn 2-x Lithium manganese composite oxide with a spinel structure represented by O4; LiCoPO4; LiFePO4; elemental sulfur (S8); Li2S n (n=1), organosulfur compounds or carbon-sulfur polymers ((C2S x ) n This may include, but is not limited to, sulfur series compounds such as (x=2.5~50, n=2).

[0058] The conductive material electrically connects the electrolyte and the positive electrode active material, and acts as a pathway for electrons to move from the current collector to the positive electrode active material. It can be used without limitation as long as it does not cause chemical changes in lithium secondary batteries and is porous and conductive.

[0059] For example, the conductive material can be a porous carbon-based material, such as carbon black, graphite, graphene, activated carbon, carbon fiber, metallic fibers such as metal mesh; metallic powders such as copper, silver, nickel, and aluminum; or organic conductive materials such as polyphenylene derivatives. The conductive materials can be used individually or in combination.

[0060] Currently, commercially available conductive materials include the acetylene black series (products from Chevron Chemical Company or Gulf Oil Company, etc.), the Ketjen Black EC series (products from Armak Company), Vulcan XC-72 (products from Cabot Company), and Super P (products from MMM). Examples include acetylene black, carbon black, and graphite.

[0061] Furthermore, the binder enhances the bonding force between the components constituting the positive electrode and between them and the current collector, and any binder known in the industry can be used.

[0062] For example, the binder may be one, a mixture of two or more, or a copolymer selected from the group consisting of: fluororesin binders containing polyvinylidenefluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol binders; polyolefin binders containing polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders.

[0063] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector. Furthermore, the negative electrode, like the positive electrode, may optionally include a conductive material and a binder. In this case, the negative electrode current collector, conductive material, and binder are as described above.

[0064] The aforementioned negative electrode active material is lithium ion (Li + Any substance that can reversibly intercalate or deintercalate lithium, or react with lithium ions to reversibly form lithium-containing compounds, is acceptable.

[0065] For example, the negative electrode active material is one or more carbon-based materials, Si-based materials, Li selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super-P, graphene, and fibrous carbon. x Fe2O3 (0 ≤ x ≤ 1), Li x WO2(0≦x≦1), Sn x Me 1-xMe´ y O z (Me: Mn, Fe, Pb, Ge; Me´: Al, B, P, Si, Group 1, 2, 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc. metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides, etc. may be included, but are not limited thereto.

[0066] Also, the negative electrode may include a negative electrode current collector and a coating layer including metal-carbon composite particles located on the negative electrode current collector. This may mean an anodeless negative electrode that does not contain a negative electrode active material.

[0067] When the all-solid-state battery is charged, lithium ions may pass through the coating layer and reach the surface of the negative electrode current collector, and these may be electrodeposited to form a lithium metal layer.

[0068] The metal-carbon composite particles may have a form in which carbon particles and metal particles are attached to each other or one of them is coated on the surface of the other, and may be physically or chemically bonded.

[0069] The carbon particles may include natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotubes, fullerenes, carbon fibers, fluorinated carbon.

[0070] The aforementioned metal particles are lithiophilic metals, such as Ni, Cu, Ag, Au, Pt, Al, Zn, and Bi, and may be one or more of these in combination. Introducing these lithium-philic metals is advantageous for forming a stable and uniform lithium layer on the surface of the current collector.

[0071] The negative electrode may be manufactured by mixing a binder solution and the composite particles to produce a slurry for forming a coating layer, and then applying and drying the slurry onto a negative electrode current collector. In this case, the binder may be a conventional binder used in the industry.

[0072] The manufacturing of the all-solid-state battery is not particularly limited in the present invention, and known methods can be used.

[0073] As an example, a solid electrolyte membrane is placed between the positive and negative electrodes, and then the cell is assembled by compression molding. After the assembled cell is placed inside an outer packaging material, it is sealed by heat compression or the like. As the outer packaging material, laminate packs made of aluminum, stainless steel, etc., or metal containers such as cylindrical or rectangular containers can be used.

[0074] As an example, the positive and negative electrodes are manufactured in the form of a slurry composition containing the respective electrode active material, solvent, and binder, and then coated and dried in a slurry coating process.

[0075] Methods for coating the electrode slurry onto a current collector include distributing the electrode slurry onto the current collector and then uniformly dispersing it using a doctor blade, die casting, comma coating, and screen printing. Alternatively, the electrode slurry can be formed on a separate substrate and then bonded to the current collector by pressing or lamination. In this case, the thickness of the final coating can be adjusted by adjusting the concentration of the slurry solution or the number of coatings.

[0076] The drying process involves removing solvent and moisture from the slurry coated on the metal current collector in order to dry it, and may vary depending on the solvent used. For example, it is performed in a vacuum oven at 50-200°C. Drying methods include, for example, drying with hot air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. While there are no particular limitations on drying time, it is usually carried out in the range of 30 seconds to 24 hours.

[0077] The drying process may be followed by a cooling process, which may involve slow cooling to room temperature to allow for proper recrystallization of the binder.

[0078] Furthermore, if necessary, after the drying process, a rolling process can be performed in which the electrodes are passed between two high-temperature heated rolls and compressed to a desired thickness in order to increase the capacitance density of the electrodes and increase the adhesion between the current collector and the active material. The rolling process is not particularly limited in this invention, and any known rolling process (pressing) is possible. For example, it may be performed by passing the electrodes between rotating rolls or by using a flat plate press.

[0079] The shape of the all-solid-state battery is not particularly limited and can be in various shapes such as cylindrical, stacked, or coin-shaped.

[0080] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications naturally fall within the scope of the attached claims.

[0081] Example 1. Example 1-1. Preparation of a solid electrolyte composition for all-solid-state batteries As a solid electrolyte, an argyrodite (Li6PS5Cl) with a particle size (D50) of 0.6-0.8 μm and a particle size (D99) of 3-4 μm was mixed with a styrene-butadiene-styrene copolymer as a binder and glycolic acid ethoxylate lauryl ether with a weight-average molecular weight of 4080 as a dispersant in a weight ratio of 98:1.7:0.3. This mixture was then added to isobutyl isobutylate to produce the slurry-like solid electrolyte composition for all-solid-state batteries of Example 1-1.

[0082] Examples 1-2. Manufacturing of solid electrolyte membranes for all-solid-state batteries Polyethylene terephthalate was used as a release film, and the solid electrolyte composition for all-solid-state batteries produced in Example 1-1 was applied to the release film using a bar coater. After that, it was dried under vacuum for 5 hours, and the release film was removed to produce the solid electrolyte membrane for all-solid-state batteries of Example 1-2.

[0083] Examples 1-3. A positive electrode was manufactured by mixing a positive electrode active material (NCM 811), a conductive material (carbon fiber), a solid electrolyte (Li6PS5Cl), and a binder (polytetrafluoroethylene) in a weight ratio of 84:0.2:14.8:1, applying the mixture to a positive electrode current collector, and then rolling it.

[0084] The negative electrode was manufactured by coating a 20 μm thick mixture of negative electrode active material (carbon black) and binder (polyvinylidene fluoride) onto a 10 μm thick SUS (stainless steel) material, which served as the negative electrode current collector.

[0085] The solid electrolyte membrane produced in Example 1-2 was interposed between the positive electrode and the negative electrode to produce the all-solid-state battery of Example 1-3.

[0086] Example 2. Except for using glycolic acid ethoxylate oleyl ether with a weight-average molecular weight of 2220 as a dispersant, the procedure was carried out in the same manner as in Examples 1-1, 1-2, and 1-3, to produce the solid electrolyte composition for an all-solid-state battery in Example 2-1, the solid electrolyte membrane for an all-solid-state battery in Example 2-2, and the all-solid-state battery in Example 2-3.

[0087] Example 3. Except for using glycolic acid ethoxylate 4-tert-butylphenyl ether with a weight-average molecular weight of 1080 as a dispersant, the procedure was carried out in the same manner as in Examples 1-1, 1-2, and 1-3, to produce the solid electrolyte composition for all-solid-state batteries in Example 3-1, the solid electrolyte membrane for all-solid-state batteries in Example 3-2, and the all-solid-state battery in Example 3-3.

[0088] Comparative Example 1. Except for not using a dispersant, the procedure was carried out in the same manner as in Examples 1-1, 1-2, and 1-3 to produce the solid electrolyte composition for all-solid-state batteries in Comparative Example 1-1, the solid electrolyte membrane for all-solid-state batteries in Comparative Example 1-2, and the all-solid-state battery in Comparative Example 1-3.

[0089] Comparative Example 2. Except for using glycolic acid ethoxylate lauryl ether with a weight-average molecular weight of 740 as a dispersant, the same procedure as in Examples 1-1, 1-2, and 1-3 was followed to produce the solid electrolyte composition for all-solid-state batteries of Comparative Example 2-1, the solid electrolyte membrane for all-solid-state batteries of Comparative Example 2-2, and the all-solid-state battery of Comparative Example 2-3.

[0090] Comparative Example 3. Except for using glycolic acid ethoxylate oleyl ether with a weight-average molecular weight of 5680 as a dispersant, the same procedure as in Examples 1-1, 1-2, and 1-3 was followed to produce the solid electrolyte composition for all-solid-state batteries of Comparative Example 3-1, the solid electrolyte membrane for all-solid-state batteries of Comparative Example 3-2, and the all-solid-state battery of Comparative Example 3-3.

[0091] Experimental Example 1. Measurement of the dispersion particle size of solid electrolyte in a solid electrolyte composition for all-solid-state batteries. The dispersion particle size of the solid electrolyte in the solid electrolyte compositions for all-solid-state batteries described above in Examples 1-1 to 3-1 and Comparative Examples 1-1 to 3-1 was measured using a particle size analyzer.

[0092] The solid electrolyte used in Examples 1-1 to 3-1 and Comparative Examples 1-1 to 3-1 was argyrodite (Li6PS5Cl) with a particle size (D50) of 0.6 to 0.8 μm and a particle size (D99) of 3 to 4 μm. The dispersed particle size was measured to confirm that the solid electrolyte was dispersed without aggregation within the solid electrolyte composition for all-solid-state batteries.

[0093] The results are shown in Table 1 and Figure 1 below.

[0094] [Table 1]

[0095] In Table 1 above, the solid electrolyte compositions for all-solid-state batteries in Examples 1-1 to 3-1 of the present invention showed that the particle sizes of the dispersed solid electrolyte within the composition (D50) and (D99) were very similar to the particle sizes D50 and D99 of the solid electrolyte before dispersion. This indicates that the solid electrolyte was dispersed without aggregation.

[0096] Comparative Example 1-1 did not contain a dispersant, Comparative Example 2-1 used a carboxylic acid compound with a weight-average molecular weight of less than 1000 as a dispersant, and Comparative Example 3-1 used a carboxylic acid compound with a weight-average molecular weight exceeding 5000 as a dispersant. In Comparative Examples 1-1 to 3-1, the solid electrolyte was unable to maintain its particle size within the solid electrolyte composition for all-solid-state batteries and aggregated with each other, resulting in a significant increase in the dispersion particle size (D99). In particular, the aggregation of the solid electrolyte occurred most frequently in Comparative Example 1-1, which did not contain a dispersant, resulting in a significant increase in the dispersion particle size (D99). Furthermore, even with the inclusion of a dispersant, using a carboxylic acid compound with a weight-average molecular weight outside the range of 1000 to 5000 resulted in poor dispersion of the solid electrolyte and an increase in the dispersion particle size (D99). Therefore, it was found that Comparative Examples 1-1 to 3-1 increased the dispersion particle size (D99) of the solid electrolyte within the solid electrolyte for all-solid-state batteries, leading to the aggregation of the solid electrolyte.

[0097] Experimental Example 2. Measurement of Ionic Conductivity of Solid Electrolyte Membrane for All-Solid-State Batteries The thickness of the solid electrolyte membrane for the all-solid-state battery in Examples 1-2 to 3-2 and Comparative Examples 1-2 to 3-2 was 30 μm, and the ionic conductivity of the solid electrolyte membrane for the all-solid-state battery was measured.

[0098] The ionic conductivity was measured by assembling a jig cell after positioning aluminum foil on the upper and lower parts of the solid electrolyte membrane for the all-solid-state battery, and then pressurizing it at 360 MPa. The results are shown in Table 2 below.

[0099] [Table 2]

[0100] Examples 1-2 to 3-2 used carboxylic acid compounds with a weight-average molecular weight of 1000 to 5000 as dispersants, and showed high ionic conductivity of the solid electrolyte membrane.

[0101] Comparative Examples 1-2 did not contain a dispersant, Comparative Example 2-2 used a carboxylic acid compound with a weight-average molecular weight of less than 1000 as a dispersant, and Comparative Example 3-2 used a carboxylic acid compound with a weight-average molecular weight exceeding 5000 as a dispersant. As can be seen from the results of Experimental Example 1, the solid electrolyte was not well dispersed and aggregated in the solid electrolyte compositions for all-solid-state batteries of Comparative Examples 1-1 to 3-1. Therefore, it was found that using these to manufacture solid electrolyte membranes for all-solid-state batteries would result in solid electrolyte membranes with uneven thickness and low ionic conductivity. In the case of Comparative Example 1-2, the dispersion of the solid electrolyte was very poor, resulting in aggregation of the solid electrolyte. However, because the solid electrolyte content increased due to the absence of a dispersant, the ionic conductivity was at a similar level to that of Comparative Examples 2-2 and 3-2.

[0102] Experimental Example 3. Evaluation of Life Characteristics of All-Solid-State Batteries The life characteristics of the all-solid-state batteries in Examples 1-3 to 3-3 and Comparative Examples 1-3 to 3-3 were measured.

[0103] Life characteristics were measured by charging the all-solid-state battery at 60°C in CCCV mode at 0.33C until it reached 4.25V, then discharging it to 3.0V with a constant current, and measuring the capacity retention rate after 150 charge-discharge cycles.

[0104] The results are shown in Figure 2.

[0105] Examples 1-3 to 3-3 used carboxylic acid compounds with a weight-average molecular weight of 1000 to 5000 as dispersants, and showed excellent lifespan characteristics for all-solid-state batteries.

[0106] Comparative Example 1-1 did not contain a dispersant, Comparative Example 2-1 used a carboxylic acid compound with a weight-average molecular weight of less than 1000 as a dispersant, and Comparative Example 3-1 used a carboxylic acid compound with a weight-average molecular weight exceeding 5000 as a dispersant. As can be seen from the results of Experimental Example 1, the solid electrolyte was not properly dispersed in the solid electrolyte compositions for all-solid-state batteries of Comparative Examples 1-1 to 3-1, and aggregation was observed. As a result, as can be seen from the results of Experimental Example 2, the thickness of the solid electrolyte membrane for all-solid-state batteries of Comparative Examples 1-2 to 3-2 was non-uniform, and the ionic conductivity was low. Therefore, it was found that when all-solid-state batteries were manufactured using these compositions, the lifespan characteristics of the all-solid-state batteries were very poor.

[0107] The present invention relates to a solid electrolyte composition for all-solid-state batteries that uses a carboxylic acid compound having a weight-average molecular weight of 1000 to 5000 as a dispersant. The dispersant prevents the solid electrolyte from aggregating within the composition and ensures proper dispersion. Furthermore, a solid electrolyte membrane produced using the solid electrolyte composition for all-solid-state batteries has uniform thickness and high ionic conductivity, and an all-solid-state battery containing this membrane can exhibit improved lifespan characteristics.

Claims

1. It comprises a solid electrolyte, a binder, and a dispersant. The dispersant is a carboxylic acid compound having a weight-average molecular weight of 1000 or more and 5000 or less. The solid electrolyte composition for all-solid-state batteries, wherein the dispersant is one or more selected from the group consisting of glycolate ethoxylate lauryl ether, glycolate ethoxylate oleyl ether, and glycolate ethoxylate 4-tert-butylphenyl ether.

2. The particle size D50 of the solid electrolyte is 0.5 μm or more and 1.5 μm or less, and the particle size D99 is 3 μm or more and 5 μm or less. The solid electrolyte composition for an all-solid-state battery according to claim 1, wherein the dispersion particle size D50 of the solid electrolyte in the solid electrolyte composition for an all-solid-state battery is 0.5 μm or more and 1.5 μm or less, and the dispersion particle size D99 is 3 μm or more and 5 μm or less.

3. The solid electrolyte composition for an all-solid-state battery according to claim 2, wherein the dispersion particle size (D99) / dispersion particle size (D50) of the solid electrolyte in the solid electrolyte composition for an all-solid-state battery is 2 or more and 7 or less.

4. The solid electrolyte composition for all-solid-state batteries according to claim 1, wherein the solid electrolyte composition for all-solid-state batteries comprises 95% by weight or more and 99% by weight or less of a solid electrolyte, 0.5% by weight or more and 5% by weight or less of a binder, and 0.1% by weight or more and 2% by weight or less of a dispersant, based on the total weight of the solid electrolyte composition for all-solid-state batteries.

5. The solid electrolyte composition for an all-solid-state battery according to claim 1, wherein the solid electrolyte comprises one or more selected from the group consisting of sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes.

6. The solid electrolyte composition for an all-solid-state battery according to claim 5, wherein the solid electrolyte includes a sulfide-based solid electrolyte.

7. A solid electrolyte membrane for an all-solid-state battery, manufactured using the solid electrolyte composition for an all-solid-state battery described in any one of claims 1 to 6.

8. The solid electrolyte membrane for an all-solid-state battery according to claim 7, wherein the thickness of the solid electrolyte membrane is 20 μm or more and 50 μm or less.

9. The ionic conductivity of the solid electrolyte membrane is 1.3 × 10⁻⁶. －３ A solid electrolyte membrane for an all-solid-state battery according to claim 7, wherein the S / cm is 1 or more.

10. This is an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between them. The solid electrolyte membrane is the solid electrolyte membrane described in claim 7, in an all-solid-state battery.

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