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

Abstract

The present invention relates to a solid electrolyte membrane 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. 10-2023-0102139 filed on August 4, 2023, and Korean Patent Application No. 10-2024-0098513 filed on July 25, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a solid electrolyte membrane and an all-solid-state battery including the same. [Background technology]

[0003] A secondary battery is a device that converts external electrical energy into chemical energy, stores it, and generates electricity when needed. It is also called a rechargeable battery because it can be recharged multiple times. Commonly used secondary batteries include lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (NiMH), and lithium secondary batteries. Secondary batteries offer both economical and environmental advantages over primary batteries, which are used once and then discarded.

[0004] Meanwhile, advances in wireless communication technology have led to demand for lighter, thinner, and smaller portable devices and automotive accessories, resulting in a growing demand for secondary batteries as a power source for these devices. In particular, hybrid and electric vehicles have become commercially viable in order to prevent environmental pollution. Research is emerging into using secondary batteries in these next-generation vehicle batteries to reduce manufacturing costs and weight and extend battery life. Among the various secondary batteries available, lithium secondary batteries have recently been gaining attention due to their light weight, high energy density, high operating potential, and long cycle life.

[0005] In general, a lithium secondary battery is manufactured by mounting an electrode assembly including a negative electrode, a positive electrode, and a separator inside a cylindrical or rectangular metal can or a pouch-type case made of an aluminum laminate sheet, and injecting an electrolyte into the electrode assembly.

[0006] However, lithium secondary batteries require a case with a certain amount of space, such as a cylindrical, rectangular, or pouch-shaped case, which limits the development of various portable devices. Therefore, new lithium secondary batteries with a shape that can be easily modified are needed. In particular, electrolytes contained in lithium secondary batteries that are leak-proof and have excellent ionic conductivity are needed.

[0007] Conventional electrolytes for lithium secondary batteries have mainly been liquid electrolytes in which lithium salts are dissolved in non-aqueous organic solvents. However, such liquid electrolytes have the potential for electrode material degradation and organic solvent volatilization, as well as the risk of combustion or explosion due to temperature increases in the surrounding area and the battery itself, and the risk of liquid leakage, making it difficult to realize various types of highly safe lithium secondary batteries.

[0008] On the other hand, all-solid-state batteries using solid electrolytes have the advantage that they do not use organic solvents, allowing electrode assemblies to be produced safely and simply.

[0009] However, all-solid-state batteries have limitations in that their actual energy density and output are lower than those of conventional lithium secondary batteries that use liquid electrolytes. Because an electrolyte membrane containing a solid electrolyte is located between the positive and negative electrodes, all-solid-state batteries are larger and heavier than conventional lithium secondary batteries, resulting in lower energy density per volume and energy density per weight. If the electrolyte membrane is made thinner to prevent this, a short circuit between the positive and negative electrodes may occur.

[0010] However, there are limitations with the current limited slurry solvent and binder technology. Conventionally, when a solid electrolyte membrane is manufactured using an NBR-based polymer as a binder, flexibility is ensured and a free-standing membrane can be obtained, but the problem is that battery performance deteriorates due to low ionic conductivity.

[0011] The solid electrolyte membrane for all-solid-state batteries varies greatly depending on the physical properties of the binder material, from the dispersibility of electrolyte particles to the feasibility of manufacturing the solid electrolyte membrane and the charge / discharge characteristics of the battery. Therefore, there is a need to develop a solid electrolyte membrane for all-solid-state batteries that not only has excellent ion conductivity but also flexibility. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent Publication No. 10-2021-0082575 Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, the present inventors have conducted extensive research to solve the above problems and have found that a solid electrolyte membrane with improved ionic conductivity and flexibility can be manufactured by adjusting the contents of an acrylic binder and a nitrile butadiene rubber (NBR) binder, thereby completing the present invention.

[0014] Therefore, an object of the present invention is to provide a solid electrolyte membrane for an all-solid-state battery that has excellent ion conductivity and flexibility.

[0015] Another object of the present invention is to provide an all-solid-state battery including the solid electrolyte membrane. [Means for solving the problem]

[0016] In one aspect of the present invention, a solid electrolyte membrane for an all-solid-state battery includes a solid electrolyte and a binder, and the binder includes an acrylate-based binder and an NBR-based binder.

[0017] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may have a content of the acrylate binder of 25% by weight or more and less than 75% by weight based on the total weight of the binder.

[0018] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may have a content of the NBR-based binder of 75 wt % or less and more than 25 wt % based on the total weight of the binder.

[0019] In one aspect of the present invention, in the solid electrolyte membrane for an all-solid-state battery, the acrylate-based binder may be an alkyl acrylate-based binder.

[0020] In one aspect of the present invention, in the solid electrolyte membrane for an all-solid-state battery, the alkyl acrylate binder may include an acrylate monomer selected from the group consisting of alkyl (meth)acrylate, alkyl acrylate, hydroxyalkyl acrylate, epoxy (meth)acrylate, and combinations thereof.

[0021] In one aspect of the present invention, in the solid electrolyte membrane for an all-solid-state battery, the solid electrolyte may include any one or more of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte.

[0022] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may have a thickness of 10 μm to 200 μm.

[0023] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may be a free-standing film.

[0024] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may have an ionic conductivity of 1.0 mS / cm to 10 mS / cm.

[0025] In one aspect of the present invention, the all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, and the solid electrolyte membrane is the solid electrolyte membrane according to the present invention. [Effects of the Invention]

[0026] The solid electrolyte membrane for an all-solid-state battery of the present invention contains an acrylate-based binder and a nitrile-butadiene rubber-based binder as binders, and by adjusting the content of the binders, it is possible to exhibit excellent effects in ion conductivity and flexibility. [Brief explanation of the drawings]

[0027] [Figure 1a] 1 is a view confirming flexibility of a solid electrolyte membrane according to an embodiment of the present invention; [Figure 1b] 1 is a view confirming flexibility of a solid electrolyte membrane according to an embodiment of the present invention; [Figure 2a] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. [Figure 2b] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. [Figure 2c] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. [Figure 2d] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. [Figure 2e] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. [Figure 2f] 1 is a diagram confirming flexibility of a solid electrolyte membrane according to a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will now be described in more detail.

[0029] The terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed in a meaning and concept that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his / her invention.

[0030] The terms used in the present invention are used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, terms such as "comprise" or "have" specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0031] Lithium secondary batteries have been used in small devices such as mobile phones and laptops, but recently their application has expanded to medium and large devices such as electric vehicles and energy storage devices. In this case, unlike small devices, the operating environment is harsher and more batteries must be used, so it is necessary to ensure stability as well as excellent performance.

[0032] Most lithium secondary batteries currently in practical use use a liquid electrolyte in which lithium salts are dissolved in an organic solvent. The organic solvents contained in the liquid electrolyte are volatile and flammable, posing a potential risk of fire or explosion and the risk of leakage, resulting in a lack of long-term reliability.

[0033] Therefore, development of all-solid-state batteries, which replace the liquid electrolyte of lithium secondary batteries with a solid electrolyte, is underway. Because all-solid-state batteries do not contain volatile organic solvents, they are free from the risk of explosion or fire, and are attracting attention as batteries that are economical, highly productive, and capable of producing high-power batteries.

[0034] To achieve high energy density in all-solid-state batteries, it is essential to fabricate a thin solid electrolyte membrane. The solid electrolyte membrane is fabricated by coating a slurry containing particulate solid electrolyte and a binder on a release film, drying the slurry, and then removing the release film. The physical properties of the binder can affect the dispersibility of the solid electrolyte, the feasibility of fabricating a solid electrolyte membrane, and even the charge / discharge characteristics of the all-solid-state battery.

[0035] Therefore, an object of the present invention is to provide a solid electrolyte membrane for an all-solid-state battery that has excellent ion conductivity by minimizing the decrease in ion conductivity and is highly flexible so as to facilitate the production of an all-solid-state battery.

[0036] The configuration and effects of the present invention will be described in detail below.

[0037] In one embodiment of the present invention, the solid electrolyte membrane for an all-solid-state battery includes a solid electrolyte and a binder, and the binder may include an acrylate-based binder and an NBR-based binder.

[0038] The solid electrolyte may include one or more selected from the group consisting of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, and preferably includes a sulfide-based solid electrolyte. The solid electrolyte may be in the form of particles.

[0039] The sulfide-based solid electrolyte may include Li-PS-based glass or Li-PS-based glass ceramic, which contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table.

[0040] Specifically, the sulfide-based solid electrolyte may include 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 includes one or more selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The Li6PS5Cl, Li6PS5Br, and Li6PS5I may be argyrodite-type solid electrolytes. The sulfide-based solid electrolyte may be doped with a trace element, for example, Li6PS5Cl doped with bromine (Br).

[0041] The polymer solid electrolyte is a composite of lithium salt and polymer resin, i.e., a polymer electrolyte material formed by adding polymer resin to solvated lithium salt, and has a concentration of about 1x10 -7 S / cm or more, preferably about 1x10 -5 It may exhibit ionic conductivity of S / cm or more.

[0042] Non-limiting examples of the polymer resin include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups, and the polymer electrolyte may include one or more of these. Examples of the polymer resin include branched copolymers in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms), and / or phosphazene are copolymerized with a PEO (polyethylene oxide) main chain using a comonomer, comb-like polymers, and crosslinked polymers, and the polymer electrolyte may include one or more of these.

[0043] In the electrolyte of the present invention, the lithium salt is Li as an ionizable lithium salt. + X - The anion of such a lithium salt is not particularly limited, but may be F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C- , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Examples include:

[0044] 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, an LLTO-based compound, 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 (where 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-based compounds, LIPON-based compounds, perovskite-based compounds, Nasicon-based compounds, and LLZO-based compounds.

[0045] The binder may include an acrylate-based binder and a Nitril Butadiene Rubber (NBR)-based binder.

[0046] In this specification, acrylate may include, for example, methyl acrylate, ethyl acrylate, etc., as a substance produced by an esterification reaction between acrylic acid and alcohol.

[0047] According to an example, the acrylate-based binder of the present invention may include an alkyl acrylate monomer such as alkyl (meth)acrylate, alkyl acrylate, or hydroxyalkyl acrylate. The acrylate-based binder may also be prepared by mixing the above monomers. For example, the acrylate-based binder may be prepared by mixing butyl acrylate and ethyl acrylate, but is not limited thereto.

[0048] Also, according to one example, the acrylate binder herein may contain two or more types of acrylic monomers, such as polyester acrylate.

[0049] Also, by way of example, the acrylate-based binder herein may include an alkyl (meth)acrylate monomer and an epoxy (meth)acrylate monomer, such as glycidyl (meth)acrylate.

[0050] In this specification, nitrile butadiene rubber (NBR) refers to a binder containing a copolymer of acrylonitrile and butadiene.

[0051] The NBR binder used in the present invention may be any of those known in the art.

[0052] In one embodiment of the present invention, the content of the acrylate binder may be 25 wt% or more and less than 75 wt% based on the total weight of the binder. More specifically, the content of the acrylate binder may be 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, or 50 wt% or more based on the total weight of the binder, or less than 75 wt%, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, or 50 wt% or less.

[0053] If the content of the acrylate-based binder is less than 25 wt %, there is a problem that the ionic conductivity of the solid electrolyte membrane is rapidly reduced, and if the content of the acrylate-based binder is 75 wt % or more, there is a problem that the content of the NBR-based binder is relatively small, and there is a problem that the flexibility of the solid electrolyte membrane is significantly reduced.

[0054] In one embodiment of the present invention, the content of the NBR binder may be 75% by weight or less to more than 25% by weight based on the total weight of the binder. More specifically, the content of the NBR binder may be 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, or 50% by weight or less, or may be more than 25% by weight, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, or 50% by weight or more, based on the total weight of the binder.

[0055] If the content of the NBR-based binder is 25 wt % or less, there is a problem that the flexibility of the solid electrolyte membrane is significantly reduced, and if the content of the NBR-based binder is more than 75 wt %, there is a problem that the content of the acrylate-based binder is relatively small, and the ionic conductivity of the solid electrolyte membrane is rapidly reduced.

[0056] The solid electrolyte may be contained in an amount of 95 wt % to 99.5 wt % and the binder may be contained in an amount of 0.5 wt % to 5 wt % based on the total weight of the solid electrolyte membrane for the all-solid-state battery. By containing the solid electrolyte and the binder as described above, it is possible to produce a solid electrolyte membrane for the all-solid-state battery that can be maintained in a film form while minimizing the content of the binder, which acts as a resistance to ion conductivity.

[0057] The solid electrolyte membrane for an all-solid-state battery may be a free-standing (also called "self-supporting") film. The free-standing film means that it maintains its shape without a support. The free-standing film-like solid electrolyte membrane for an all-solid-state battery may be used in the manufacturing process of an all-solid-state battery without any external supporting components.

[0058] The thickness of the solid electrolyte membrane for an all-solid-state battery may be 10 μm to 200 μm, and preferably 50 μm to 100 μm. By having this thickness, the membrane can be applied to an all-solid-state battery, and can have excellent effects in ion conductivity and flexibility.

[0059] The solid electrolyte membrane for an all-solid-state battery may have an ionic conductivity of 1.0 mS / cm to 10.0 mS / cm. Specifically, the ionic conductivity of the solid electrolyte membrane for an all-solid-state battery may be 1.0 mS / cm or more, 1.1 mS / cm or more, 1.2 mS / cm or more, 1.3 mS / cm or more, 1.4 mS / cm or more, 1.5 mS / cm or more, 1.6 mS / cm or more, 1.7 mS / cm or more, 1.8 mS / cm or more, 1.9 mS / cm or more, 2.0 mS / cm or more, or 10.0 mS / cm or less, 9.5 mS / cm or less, 9.0 mS / cm or less, 8.5 mS / cm or less, 8.0 mS / cm or less, 7.5 mS / cm or less, 7.0 mS / cm or less, 6.5 mS / cm or less, 6.0 mS / cm or less, 5.5 mS / cm or less, or 5.0 mS / cm or less, but is not limited to these examples. If the ionic conductivity of the solid electrolyte membrane is less than 1.0 mS / cm, the movement of lithium ions between the positive electrode and the negative electrode may decrease, resulting in a decrease in battery performance.

[0060] In one embodiment of the present invention, the all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, and the solid electrolyte membrane may be the solid electrolyte membrane of the present invention described above.

[0061] The all-solid-state battery is a lithium secondary battery, and is not limited to a positive electrode or a negative electrode, and may be a lithium-air battery, a lithium-oxide battery, a lithium-sulfur battery, or a lithium-metal battery.

[0062] The positive electrode may include a positive electrode current collector and a positive electrode active material coated on one or both sides of the positive electrode current collector.

[0063] The positive electrode current collector is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of a lithium secondary battery, and serves to support the positive electrode active material. For example, the positive electrode current collector may be made of a 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. The alloy may preferably be an aluminum-cadmium alloy. Alternatively, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may be used.

[0064] The positive electrode current collector may have fine irregularities on its surface to strengthen the bonding force with the positive electrode active material, and may be in various forms such as a film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0065] The positive electrode active material may include a positive electrode active material, and optionally a conductive material and a binder.

[0066] The positive electrode active material varies depending on the type of all-solid-state battery. For example, the positive electrode active material can be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with a higher transition metal; 1+x Mn 2-xO4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and 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 oxides represented by 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 oxides with spinel structure represented by O4; LiCoPO4; LiFePO4; elemental sulfur (S8); Li2Sn (n=1), organic sulfur compounds, or carbon-sulfur polymers (C2S x )n:x=2.5-50, n=2) and other sulfur-based compounds may be included, but are not limited to these.

[0067] The conductive material electrically connects the electrolyte and the positive electrode active material and serves as a path through which electrons move from a current collector to the positive electrode active material. Any conductive material may be used without limitation as long as it does not undergo chemical change in a lithium secondary battery and has porosity and conductivity.

[0068] For example, the conductive material may be a porous carbon-based material, such as carbon black, graphite, graphene, activated carbon, or carbon fiber; metallic fibers such as metal mesh; metallic powders such as copper, silver, nickel, or aluminum; or organic conductive materials such as polyphenylene derivatives. The conductive materials may be used alone or in combination.

[0069] Currently available conductive materials include acetylene black (Chevron Chemical Company or Gulf Oil Company products, etc.), Ketjen Black EC (Armak Company products), Vulcan XC-72 (Cabot Company products), and Super P (MMM products). Examples include acetylene black, carbon black, and graphite.

[0070] The positive electrode may further include a binder, and the binder may be any binder known in the art that further enhances the binding strength between the components constituting the positive electrode and between the components and the current collector.

[0071] For example, the binder may be one or a mixture or copolymer of two or more selected from the group consisting of: fluororesin-based binders including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber-based binders including styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, and styrene isoprene rubber; cellulose-based binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol-based binders; polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binders; and silane-based binders.

[0072] The negative electrode may include a negative electrode current collector and a negative electrode active material located on the negative electrode current collector. Further, similar to the positive electrode, the negative electrode may include a conductive material and a binder as necessary. At this time, the negative electrode current collector, the conductive material, and the binder are as described above.

[0073] The negative electrode active material can reversibly intercalate or deintercalate lithium ions (Li + ), and any substance that can react with lithium ions to reversibly form a lithium-containing compound is possible.

[0074] For example, the negative electrode active material is one or more carbon-based substances 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, fibrous carbon, Si-based substances, Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 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., but not limited thereto.

[0075] The production of the all-solid-state battery is not particularly limited in the present invention, and known methods may be used.

[0076] For example, a solid electrolyte membrane is placed between a positive electrode and a negative electrode, and then the membrane is compression-molded to assemble a cell. The assembled cell is placed in an exterior packaging and then sealed by heat compression or the like. Examples of exterior packaging that can be used include laminate packs made of aluminum, stainless steel, or other materials, and cylindrical or rectangular metal containers.

[0077] For example, the positive and negative electrodes are manufactured by a slurry coating process in which a slurry composition containing the respective electrode active materials, a solvent, and a binder is prepared, coated, and then dried.

[0078] Methods for coating the electrode slurry on the current collector include distributing the electrode slurry on the current collector and then uniformly dispersing it using a doctor blade, die casting, comma coating, screen printing, etc. 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 final coating thickness can be adjusted by adjusting the concentration of the slurry solution or the number of coatings.

[0079] The drying step is a process of removing the solvent and water from the slurry in order to dry the slurry coated on the metal current collector, and may vary depending on the solvent used. For example, it is performed in a vacuum oven at 50°C to 200°C. Drying methods include drying with warm air, hot air, or low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying time is not particularly limited, but is usually within a range of 30 seconds to 24 hours.

[0080] After the drying step, a cooling step may be further included, and the cooling step may be slow cooling to room temperature so that the recrystallized structure of the binder is firmly formed.

[0081] In addition, if necessary, after the drying process, a rolling process may be performed in which the electrode is passed between two rolls heated to a high temperature to compress it to a desired thickness in order to increase the capacity density of the electrode and the adhesion between the current collector and the active material. The rolling process is not particularly limited in the present invention, and any known rolling process (pressing) can be used. For example, the rolling process may be performed by passing the electrode between rotating rolls or using a flat press.

[0082] The shape of the all-solid-state battery is not particularly limited, and may be various shapes such as a cylindrical shape, a laminated shape, or a coin shape.

[0083] Preferred examples will be described below to aid in understanding the present invention. However, the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the category and technical idea of ​​the present invention. It is to be understood that such changes and modifications also fall within the scope of the appended claims.

[0084] Manufacturing solid electrolyte membranes for all-solid-state batteries Example 1 A binder polymer was dissolved in an isobutyl isobutyrate solvent to prepare a binder solution, and then argyrodite (Li6PS5Cl) as a solid electrolyte, the binder solution, and isobutyl isobutyrate as an additional solvent were placed in a container and mixed to prepare a slurry.

[0085] The slurry was coated onto a polyethylene terephthalate (PET) release film, dried at room temperature for 2 hours, and then dried in a vacuum oven at 45°C for 5 hours. The release film was then removed to prepare a free-standing solid electrolyte membrane for an all-solid-state battery.

[0086] The solid electrolyte membrane for the all-solid-state battery contained 98 wt% argyrodite and 2 wt% binder polymer based on the total weight of the solid electrolyte membrane. The binder polymer was made of 50 wt% acrylate and 50 wt% nitrile butadiene rubber (NBR). The acrylate binder was a mixture of 50 wt% butyl acrylate and 50 wt% ethyl acrylate.

[0087] The thickness of the solid electrolyte membrane for the all-solid-state battery was 100 μm.

[0088] Example 2 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 25 wt % acrylate and 75 wt % NBR.

[0089] Comparative Example 1 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 100 wt % acrylate.

[0090] Comparative Example 2 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 75 wt % acrylate and 25 wt % NBR.

[0091] Comparative Example 3 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 100 wt % NBR.

[0092] Comparative Example 4 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 50 wt % NBR and 50 wt % polyimide (PI).

[0093] Comparative Example 5 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 50 wt % NBR and 50 wt % styrene ethylene butylene styrene (SEBS).

[0094] Comparative Example 6 A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the binder polymer was 50 wt % NBR and 50 wt % cyanoacrylate (CA).

[0095] Experimental Example 1: Measurement of ionic conductivity and flexibility The ionic conductivity of the solid electrolyte membranes for all-solid-state batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 6 was measured, and flexibility was confirmed.

[0096] FIG. 1a is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Example 1, and FIG. 1b is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Example 2.

[0097] FIG. 2a is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 1, FIG. 2b is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 2, FIG. 2c is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 3, FIG. 2d is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 4, FIG. 2e is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 5, and FIG. 2f is a diagram confirming the flexibility of the solid electrolyte membrane for an all-solid-state battery according to Comparative Example 6.

[0098] The ionic conductivity was measured by assembling a jig cell by placing aluminum foil on the top and bottom of the solid electrolyte membrane for an all-solid-state battery, and then applying a pressure of 360 MPa.

[0099] Flexibility was evaluated by observing whether cracks occurred when the solid electrolyte membrane for all-solid-state batteries was wound around a mandrel with a diameter of 2 mm.

[0100] The results of the ionic conductivity and flexibility of the solid electrolyte membrane are shown in Table 1 below.

[0101] [Table 1]

[0102] From the results in Table 1, Examples 1 and 2 contain 25 wt% or more to less than 75 wt% of acrylate and 75 wt% or less to more than 25 wt% of NBR as the binder polymer, and therefore exhibit excellent ionic conductivity, no cracking, and excellent flexibility. Comparative Example 1 contains 100 wt% of acrylate relative to the total weight of the binder polymer, and although it has better ionic conductivity than Examples 1 and 2, it was confirmed that it exhibited cracking and lacked flexibility.

[0103] Comparative Example 2 contained 75 wt% of acrylate and 25 wt% of NBR relative to the total weight of the binder polymer, and although the ionic conductivity was superior to that of Examples 1 and 2, cracks occurred and it was confirmed that the material lacked flexibility.

[0104] Comparative Example 3 contained 100% by weight of NBR relative to the total weight of the binder polymer, and it was confirmed that the flexibility was excellent but the ionic conductivity was lower than those of Examples 1 and 2.

[0105] Comparative Example 4 contained 50 wt % NBR and 50 wt % polyimide (PI) based on the total weight of the binder polymer, and although it had excellent ionic conductivity, it was confirmed that cracks occurred and it lacked flexibility.

[0106] Comparative Example 5 contained 50 wt% NBR and 50 wt% styrene ethylene butylene styrene (SEBS) based on the total weight of the binder polymer, and was found to have excellent flexibility but lower ionic conductivity than Examples 1 and 2.

[0107] Comparative Example 6 contained 50 wt% NBR and 50 wt% cyanoacrylate (CA) based on the total weight of the binder polymer, and although it had excellent ionic conductivity, it was confirmed that cracks occurred and it lacked flexibility.

[0108] Therefore, it is found that a solid electrolyte membrane for an all-solid-state battery containing an acrylate-based binder polymer in an amount of 25 wt % or more and less than 75 wt % and an NBR-based binder polymer in an amount of 75 wt % or less and more than 25 wt % relative to the total weight of the binder polymer has excellent ionic conductivity and flexibility.

[0109] It is also clear that the combination of NBR and other binders in addition to the acrylate-based binder as the binder polymer reduces the ionic conductivity of the electrolyte.

[0110] In addition, it is found that the solid electrolyte membrane for all-solid-state batteries using NBR and alkyl acrylate binders as binder polymers has better ionic conductivity and flexibility.

Claims

1. a solid electrolyte and a binder; The solid electrolyte membrane for an all-solid-state battery, wherein the binder includes an acrylate-based binder and an NBR-based binder.

2. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the content of the acrylate binder is 25% by weight or more and less than 75% by weight based on the total weight of the binder.

3. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the content of the NBR-based binder is 75% by weight or less to more than 25% by weight based on the total weight of the binder.

4. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the acrylate-based binder is an alkyl acrylate-based binder.

5. 5. The solid electrolyte membrane for an all-solid-state battery according to claim 4, wherein the alkyl acrylate binder comprises an acrylate monomer selected from the group consisting of alkyl (meth)acrylate, alkyl acrylate, hydroxyalkyl acrylate, epoxy (meth)acrylate, and combinations thereof.

6. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the solid electrolyte includes at least one of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte.

7. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the thickness of the solid electrolyte membrane for an all-solid-state battery is 10 μm to 200 μm.

8. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the solid electrolyte membrane for an all-solid-state battery is a free-standing film.

9. 2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein the ionic conductivity of the solid electrolyte membrane for an all-solid-state battery is 1.0 mS / cm to 10 mS / cm.

10. a positive electrode; a negative electrode; a solid electrolyte membrane interposed between the positive electrode and the negative electrode; The solid electrolyte membrane according to any one of claims 1 to 9, wherein the solid electrolyte membrane is an all-solid-state battery.

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