Solid electrolyte membrane and all-solid-state battery comprising same

Abstract

The present invention relates to a solid electrolyte membrane for an all-solid-state battery, comprising a solid electrolyte and a binder, in which the binder comprises an acrylate-based binder and an NBR-based binder. The purpose of the present invention is to provide a solid electrolyte membrane having improved ionic conductivity and flexibility.

Description

Technical Field

[0001] This application claims priority to 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, the disclosures of which are incorporated herein by reference in their entirety.

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

[0003] A secondary battery is a device that converts external electrical energy into chemical energy, stores it, and generates electricity when needed. Since it can be recharged many times, it is also called a rechargeable battery. Common secondary batteries include lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (NiMH), and lithium secondary batteries. Compared with primary batteries that are used once and then discarded, secondary batteries have economic advantages as well as environmental advantages.

[0004] On the other hand, as wireless communication technology continues to develop, the demand for lightweight, thin and miniaturized portable devices and vehicle accessories is increasing, and the demand for secondary batteries as energy sources for these devices is also growing. In particular, as hybrid electric vehicles and electric vehicles become more practical in preventing environmental pollution, people have begun to study the use of secondary batteries in these next-generation vehicle batteries to reduce manufacturing costs and weight while extending their service life. Among various secondary batteries, lithium secondary batteries have attracted much attention due to their light weight, high energy density, high operating potential, and long cycle life.

[0005] Generally, a lithium secondary battery is manufactured by mounting an electrode assembly consisting of a negative electrode, a positive electrode, and a separator in a cylindrical or angular shaped metal can or an aluminum laminate pouch case, and then injecting an electrolyte into the electrode assembly.

[0006] However, lithium secondary batteries require cylindrical, angular or pouch-shaped housings with a certain space, which limits the development of various portable devices. Therefore, a new type of lithium secondary battery that is easy to shape is needed. In particular, as an electrolyte for lithium secondary batteries, an electrolyte with excellent ion conductivity and no leakage is needed.

[0007] Conventionally, liquid electrolytes in which lithium salts are dissolved in non-aqueous organic solvents have been used in lithium secondary batteries. However, such liquid electrolytes are not only prone to electrode material degradation and organic solvent volatilization, but are also prone to combustion or explosion due to increased ambient temperature and the temperature of the battery itself, and are also prone to leakage, making it difficult to achieve various types of high-safety lithium secondary batteries.

[0008] On the other hand, all-solid-state batteries utilizing solid electrolytes have the advantage of being free of organic solvents, allowing for safe and simple electrode assemblies.

[0009] However, all-solid-state batteries have limitations because their actual energy density and power output are not as good as lithium secondary batteries using conventional liquid electrolytes. Since there is an electrolyte membrane containing a solid electrolyte 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 unit volume and energy density per unit weight. To avoid this, thinning the electrolyte membrane will cause a short circuit between the positive and negative electrodes.

[0010] However, there are limitations in the current limited slurry solvent and binder technology. In other words, conventionally, solid electrolyte membranes are manufactured by using NBR-based polymers as binders to ensure flexibility and obtain a self-supporting membrane, but lower ion conductivity reduces battery characteristics.

[0011] Solid electrolyte membranes for all-solid-state batteries are highly dependent on the properties of binder materials, from the dispersibility of electrolyte particles to the manufacturability of solid electrolyte membranes or the charging and discharging characteristics of batteries. Therefore, it is necessary to develop a solid electrolyte membrane for all-solid-state batteries that has both excellent ion conductivity and flexibility.

[0012] [Prior art literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Korean Patent Publication No. 10-2021-0082575 Summary of the invention

[0015] [Technical issues]

[0016] In order to solve the above problems, the inventors of the present invention conducted various studies and confirmed that adjusting the content of acrylic adhesive and nitrile rubber (NBR) adhesive as adhesives can prepare a solid electrolyte membrane with improved ion conductivity and flexibility, and completed the present invention.

[0017] Therefore, the present invention aims to provide a solid electrolyte membrane for an all-solid-state battery having excellent ionic conductivity and flexibility.

[0018] Another object of the present invention is to provide an all-solid-state battery comprising the solid electrolyte membrane.

[0019] [Technical solution]

[0020] In one aspect of the present invention, a solid electrolyte membrane for an all-solid-state battery includes a solid electrolyte and a binder, wherein the binder includes an acrylate-based binder and an NBR-based binder.

[0021] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may contain the acrylic ester binder in an amount of at least 25 wt % and less than 75 wt % based on the total weight of the binder.

[0022] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may contain the NBR-based binder in an amount of 75 wt % or less and greater than 25 wt % based on the total weight of the binder.

[0023] 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.

[0024] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may include an acrylate monomer, wherein the alkyl acrylate-based binder is selected from the group consisting of alkyl (meth)acrylates, alkyl acrylates, hydroxyalkyl acrylates, epoxy (meth)acrylates, and combinations thereof.

[0025] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may include at least one of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte.

[0026] In one aspect of the present invention, the thickness of the solid electrolyte membrane for an all-solid-state battery may be 10 μm to 200 μm.

[0027] In one aspect of the present invention, the solid electrolyte membrane for an all-solid-state battery may be a free-standing membrane.

[0028] In one aspect of the present invention, the ion conductivity of the solid electrolyte membrane for an all-solid-state battery may be 1.0 mS / cm to 10 mS / cm.

[0029] In one aspect of the present invention, an all-solid-state battery comprises a positive electrode, a negative electrode, and a solid electrolyte membrane disposed therebetween, wherein the solid electrolyte membrane is the solid electrolyte membrane of the present invention.

[0030] [Beneficial Effects]

[0031] The solid electrolyte membrane for an all-solid-state battery of the present invention contains an acrylic ester binder and a nitrile rubber binder as a binder, and can exhibit excellent ion conductivity and flexibility by adjusting the content of the binder. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1a and 1b It is a diagram showing the flexibility of the solid electrolyte membrane according to the example of the present invention.

[0033] Figures 2a to 2fIt is a graph showing the flexibility of a solid electrolyte membrane of a comparative example of the present invention. DETAILED DESCRIPTION

[0034] Hereinafter, the present invention will be described in more detail.

[0035] The terms and words used in this specification and claims should not be interpreted by their ordinary meanings or dictionary meanings, but should be interpreted based on the principle that the inventor can appropriately define the concepts of the terms to best describe his / her invention, with the meanings and concepts consistent with the technical ideas of the present invention.

[0036] The terms used in the present invention are only used to describe certain examples and are not intended to limit the present invention. Unless the context clearly indicates otherwise, expressions in the singular include the plural. In the present invention, the term "comprising" or "having" is intended to indicate the presence of the features, numbers, steps, actions, components, parts or combinations thereof described in the specification, and should not be understood as excluding the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, parts or combinations thereof.

[0037] Although lithium secondary batteries have been used in small applications such as mobile phones and laptops, they have recently expanded to large and medium-sized applications such as electric vehicles and energy storage devices. In this case, unlike small applications, the working environment is more severe and more batteries need to be used, so they need to have good performance and stability.

[0038] Currently, most commercially available lithium secondary batteries use liquid electrolytes that are lithium salts dissolved in organic solvents. The organic solvents contained in the liquid electrolytes are volatile and flammable, posing a potential risk of fire and explosion. They may also leak, resulting in a lack of long-term reliability.

[0039] For this reason, all-solid-state batteries are being developed that replace the liquid electrolyte in lithium secondary batteries with solid electrolytes. Since all-solid-state batteries do not contain volatile organic solvents, there is no risk of explosion or fire, and all-solid-state batteries are receiving increasing attention as a way to manufacture high-power batteries with excellent economy and productivity.

[0040] In order to realize high energy density all-solid-state batteries, it is crucial to manufacture thin solid electrolyte membranes. The solid electrolyte membrane is prepared by applying a slurry containing a solid electrolyte in particle form and a binder to a release film, drying and removing the release film, and depending on the properties of the binder, the dispersibility of the solid electrolyte, the manufacturability of the solid electrolyte membrane, and even the charge and discharge characteristics of the all-solid-state battery may vary.

[0041] Therefore, the present invention aims to provide a solid electrolyte membrane for an all-solid-state battery, which has excellent ion conductivity by minimizing ion conductivity degradation, and has excellent flexibility to facilitate the manufacture of the all-solid-state battery.

[0042] Hereinafter, the composition and effects of the present invention will be described in detail.

[0043] In one example of the present invention, a solid electrolyte membrane for an all-solid-state battery includes a solid electrolyte and a binder, wherein the binder may include an acrylate-based binder and an NBR-based binder.

[0044] The solid electrolyte may include at least one selected from the group consisting of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, preferably a sulfide-based solid electrolyte. The solid electrolyte may be in a particle form.

[0045] The sulfide-based solid electrolyte contains sulfur (S) and exhibits ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass-ceramics.

[0046] Specifically, the sulfide-based solid electrolyte may include at least one 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, preferably may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br and Li6PS5I. Li6PS5Cl, Li6PS5Br and Li6PS5I may be argyrodite-type solid electrolytes. In addition, the sulfide-based solid electrolyte can be doped with trace elements, for example, Li6PS5Cl additionally doped with bromine (Br).

[0047] The polymer solid electrolyte is a composite of lithium salt and polymer resin, that is, a polymer electrolyte material formed by adding a polymer resin to a solvated lithium salt, which can exhibit a thermal conductivity of about 1x10 -7 S / cm or more, preferably about 1x10 -5 S / cm or above ionic conductivity.

[0048] The non-limiting examples of polymer resins include polyether polymers, polycarbonate polymers, acrylic polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives (e.g., polyethylene oxide), phosphate polymers, poly-stirring lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers comprising ion dissociation groups, and one or more thereof may be included. In addition, polymer electrolytes may be polymer resins, for example, branched copolymers, comb-like polymers, and cross-linked polymer resins copolymerized with amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS) and / or phosphazenes as monomers in polyethylene oxide (PEO) backbones, and one or more thereof may be included.

[0049] In the electrolyte of the present invention, the lithium salt is an ionizable lithium salt, which can be expressed as Li + X - The anions of these lithium salts are not particularly limited and may include, for example, 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 - wait.

[0050] The oxide-based solid electrolyte may include oxygen (O) and have an ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. For example, it may include at least one selected from the following: LLTO-based compounds, Li6La2CaTa2O 12 、Li6La2ANb2O 12 (where 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 (wherein, 0≤x≤1, 0≤y≤1), LISICON compounds, LIPON compounds, perovskite compounds, nasicon compounds and LLZO compounds.

[0051] The adhesive may include an acrylic adhesive and a nitrile rubber (NBR) adhesive.

[0052] As used herein, acrylate is a substance produced by the esterification reaction of acrylic acid with alcohol, and may include, for example, methyl acrylate, ethyl acrylate, and the like.

[0053] In one example, the acrylic adhesive of the present invention can include an alkyl acrylate monomer, such as (meth) alkyl acrylate, alkyl acrylate or hydroxyalkyl acrylate. In addition, the acrylic adhesive can be prepared by mixing monomers. In one example, the acrylic adhesive can be prepared by mixing butyl acrylate and ethyl acrylate, but is not limited to these examples.

[0054] In addition, according to one example, the acrylate adhesive of the present invention may include two or more acrylate monomers, such as polyester acrylate.

[0055] Furthermore, according to one example, the acrylic adhesive of the present invention may include an alkyl (meth)acrylate monomer and an epoxy (meth)acrylate monomer, such as glycidyl (meth)acrylate.

[0056] As used herein, nitrile rubber (NBR) refers to an adhesive comprising a copolymer of acrylonitrile and butadiene.

[0057] The NBR-based adhesive used in the present invention may be those known in the art.

[0058] In one example of the present invention, the content of the acrylate adhesive may be at least 25 wt % and less than 75 wt % based on the total weight of the adhesive. More specifically, the content of the acrylate adhesive 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, or less than 75 wt %, less than 70 wt %, less than 65 wt %, less than 60 wt %, less than 55 wt %, or less than 50 wt %, based on the total weight of the adhesive.

[0059] When the content of the acrylic adhesive is less than 25 weight %, there is a problem of rapid decrease in the ionic conductivity of the solid electrolyte membrane; when the content of the acrylic adhesive is more than 75 weight %, due to the relatively small content of the NBR adhesive, the flexibility of the solid electrolyte membrane is significantly reduced.

[0060] In one example of the present invention, based on the total weight of the adhesive, the content of the NBR-based adhesive may be less than or equal to 75 wt % and greater than 25 wt %. More specifically, based on the total weight of the adhesive, the content of the NBR-based adhesive may be less than 75 wt %, less than 70 wt %, less than 65 wt %, less than 60 wt %, less than 55 wt %, or less than 50 wt %, or greater than 25 wt %, more than 30 wt %, more than 35 wt %, more than 40 wt %, more than 45 wt %, or more than 50 wt %.

[0061] When the content of NBR-based adhesive is less than 25 wt %, there is a problem of significantly reduced flexibility of the solid electrolyte membrane. When the content of NBR-based adhesive is greater than 75 wt %, due to the relatively small content of acrylate-based adhesive, there is a problem of rapidly reduced ionic conductivity of the solid electrolyte membrane.

[0062] Based on the total weight of the solid electrolyte membrane for an all-solid-state battery, the content of the solid electrolyte may be 95 wt % to 99.5 wt %, and the content of the binder may be 0.5 wt % to 5 wt %. By containing the above-mentioned solid electrolyte and binder, a solid electrolyte membrane for an all-solid-state battery can be prepared, which can be maintained in a film form while minimizing the content of the binder serving as an ionic conductivity resistor.

[0063] The solid electrolyte membrane for all-solid-state batteries can be a self-standing (also called "self-supporting") membrane. A self-supporting membrane refers to a membrane that can maintain its shape without a support. The solid electrolyte membrane for all-solid-state batteries in the form of a self-supporting membrane can be used in the manufacturing process of all-solid-state batteries without any external supporting components.

[0064] The thickness of the solid electrolyte membrane for an all-solid-state battery may be 10 μm to 200 μm, preferably 50 μm to 100 μm. The membrane having the above thickness can be applied to an all-solid-state battery and has excellent ion conductivity and flexibility.

[0065] The ion conductivity of the solid electrolyte membrane for an all-solid-state battery may be 1.0 mS / cm to 10.0 mS / cm. Specifically, the ionic conductivity of the solid electrolyte membrane for an all-solid-state battery can be above 1.0 mS / cm, above 1.1 mS / cm, above 1.2 mS / cm, above 1.3 mS / cm, above 1.4 mS / cm, above 1.5 mS / cm, above 1.6 mS / cm, above 1.7 mS / cm, above 1.8 mS / cm, above 1.9 mS / cm, above 2.0 mS / cm, or below 10.0 mS / cm, below 9.5 mS / cm, below 9.0 mS / cm, below 8.5 mS / cm, below 8.0 mS / cm, below 7.5 mS / cm, below 7.0 mS / cm, below 6.5 mS / cm, below 6.0 mS / cm, below 5.5 mS / cm, below 5.0 mS / cm, but are not limited to these examples. If the ionic conductivity of the solid electrolyte membrane is less than 1.0 mS / cm, the transfer of lithium ions between the positive electrode and the negative electrode may be impaired, resulting in reduced battery performance.

[0066] In one example of the present invention, an all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane disposed therebetween, wherein the solid electrolyte membrane may be the solid electrolyte membrane of the present invention described above.

[0067] The all-solid-state battery is a lithium secondary battery in which the positive electrode or the negative electrode is not limited and may be a lithium air battery, a lithium oxide battery, a lithium sulfur battery, or a lithium metal battery.

[0068] The positive electrode may include a positive electrode collector and a positive electrode active material coated on one side or both sides of the positive electrode collector.

[0069] The positive electrode current collector is intended to support the positive electrode active material, and is not particularly limited as long as it has good conductivity and is electrochemically stable within the voltage range of the lithium secondary battery. For example, the positive electrode current collector can be any metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof, wherein the stainless steel can be surface treated with carbon, nickel, titanium or silver, and the alloy can preferably be an aluminum-cadmium alloy, but can also be a non-conductive polymer whose surface is treated with calcined carbon or a conductive material or a conductive polymer.

[0070] The positive electrode current collector may have microscopic irregularities formed on its surface to strengthen the binding force with the positive electrode active material, and may use various forms such as films, sheets, foils, screens, nets, porous bodies, foams, non-woven fabrics, etc.

[0071] The positive electrode active material may include a positive electrode active material and optionally a conductive material and a binder.

[0072] The positive electrode active material may vary depending on the type of all-solid-state battery. For example, the positive electrode active material may include, but is not limited to: layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium manganese oxides such as Li 1+x Mn 2-x O4 (where 0≤x≤0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide, such as LiV3O8, V2O5 or Cu2V2O7; Ni-type lithium nickel compound, which is composed of LiNi 1-x M x O2 (wherein M is Co, Mn, Al, Cu, Fe, Mg, B or Ga; and 0.01≤x≤0.3); lithium manganese composite oxide, which is composed of LiMn 2-x M x O2 (wherein M is Co, Ni, Fe, Cr, Zn or Ta; and 0.01≤x≤0.1) or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); a lithium manganese composite oxide having a spinel structure, composed of LiNi x Mn 2-x O4 represents; LiCoPO4; LiFePO4; elemental sulfur (S8); sulfur compounds, such as Li2S n (where n is 1), organic sulfur compounds or carbon sulfur polymers ((C2S x )n, wherein x is 2.5 to 50 and n is 2).

[0073] The conductive material is a material that electrically connects the electrolyte and the cathode active material and serves as a path for electrons to move from the current collector to the cathode active material, and can be used without limitation as long as it does not cause chemical changes in the lithium secondary battery and has porosity and conductivity.

[0074] For example, porous carbon materials, wherein the carbon materials include carbon black, graphite, graphene, activated carbon and carbon fiber; and metal fibers, such as metal mesh; metal powders, such as copper, silver, nickel or aluminum; or organic conductive materials, such as polyphenylene derivatives, can be used as conductive materials. The above conductive materials can be used alone or in combination.

[0075] Available products currently commercially available as conductive materials include acetylene black (from Chevron Chemical or Gulf Oil), Ketjen Black EC (from Armak), Vulcan XC-72 (from Cabot), and Super P (from MMM). Examples may include acetylene black, carbon black, and graphite.

[0076] In addition, the positive electrode may further include a binder, wherein the binder further increases the cohesive force between components constituting the positive electrode or between these components and the current collector, and any binder known in the art may be used.

[0077] For example, the adhesive can be a mixture or copolymer of one or two or more selected from the group consisting of: fluororesin adhesives, including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), nitrile rubber or styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose and regenerated cellulose; polyol adhesives; polyolefin adhesives, including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; silane adhesives.

[0078] The negative electrode may include a negative electrode current collector and a negative electrode active material located on the negative electrode current collector. In addition, similar to the positive electrode, the negative electrode may include a conductive material and a binder as needed. The negative electrode current collector, the conductive material and the binder are as described above.

[0079] The negative electrode active material is any material that can reversibly intercalate or deintercalate lithium ions (Li+), and can also be any material that can react with lithium ions to reversibly form a lithium-containing compound.

[0080] For example, the negative electrode active material may include, but is not limited to: one or more carbonaceous materials 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 fiber carbon, Si-based materials, Li x Fe2O3 (where 0≤x≤1), Li x WO2 (where 0≤x≤1), Sn x Me 1-x Me′ y O z(wherein Me is Mn, Fe, Pb or Ge; Me′ is Al, B, P, Si; an element of Group 1, 2 or 3 of the periodic table; a halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) and other 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, etc.; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; and lithium titanium oxides.

[0081] The present invention does not particularly limit the preparation of the all-solid-state battery, and known methods can be used.

[0082] For example, a solid electrolyte membrane is placed between the positive electrode and the negative electrode, and then it is compression-molded to assemble the battery cell. The assembled battery is installed in an external material and sealed by heating and compression, etc. The external material includes a laminated package of aluminum or stainless steel, and a cylindrical or square metal container.

[0083] In one example, the electrodes of the positive electrode and the negative electrode are prepared by a slurry coating process, in which the electrodes are prepared, coated, and then dried in the form of a slurry composition containing the corresponding electrode active material, solvent, and binder.

[0084] The method of coating the electrode slurry on the current collector may include a method of distributing the electrode slurry on the current collector and uniformly dispersing the electrode slurry using a doctor blade, die casting, comma coating, or screen printing. Alternatively, the electrode slurry can be formed on a separate substrate and then bonded to the current collector by a pressing or laminating method. The final coating thickness can be controlled by adjusting the concentration of the slurry or the number of coatings.

[0085] The drying process is to remove the solvent and moisture in the slurry to dry the slurry coated on the metal current collector, which can vary depending on the solvent used. For example, it is carried out in a vacuum oven at 50°C to 200°C. The drying methods include, for example, drying by warm air, hot air, low-humidity air, vacuum drying, irradiation with (far) infrared or electromagnetic radiation. The drying time is not specifically specified, but it is usually 30 seconds to 24 hours.

[0086] After the drying process, a cooling process can further be included, and the cooling process may include slow cooling to room temperature to ensure good formation of the recrystallized structure of the binder.

[0087] In addition, if necessary, in order to increase the capacity density of the electrode after the drying process and increase the adhesion between the current collector and the active material, a rolling process can be performed, wherein the electrode is passed between two heated rollers and compressed to a desired thickness. The present invention has no particular restrictions on the rolling process, and a known rolling process can be used. For example, by passing the electrode between rotating rollers or using a flat press.

[0088] The shape of the all-solid-state battery is not particularly limited, and may be cylindrical, stacked, coin-shaped, or the like.

[0089] Example

[0090] Hereinafter, preferred embodiments are described for the purpose of illustrating the present invention, but it will be apparent to those skilled in the art that various changes and modifications may be made within the scope and technical concept of the present invention, and such changes and modifications fall within the scope of the appended patent claims.

[0091] Manufacturing of solid electrolyte membranes for all-solid-state batteries

[0092] Example 1

[0093] A binder solution was prepared by dissolving a binder polymer in an isobutyl isobutyrate solvent, and then argyrodite (Li6PS5Cl) as a solid electrolyte, the binder solution and isobutyl isobutyrate as an additional solvent were added to a container and mixed to prepare a slurry.

[0094] Polyethylene terephthalate (PET) was used as a release film, and the above slurry was coated on the release film. Thereafter, it was dried at room temperature for 2 hours, and then dried in a vacuum oven at a temperature of 45°C for 5 hours, and the release film was removed to prepare a self-supporting film-formed solid electrolyte membrane for all-solid-state batteries.

[0095] The solid electrolyte membrane for all-solid-state batteries comprises 98 wt % of argyrodite and 2 wt % of a binder polymer based on the total weight of the solid electrolyte membrane. The binder polymer comprises 50 wt % of acrylate and 50 wt % of nitrile rubber (NBR). The acrylate binder uses a mixture of 50 wt % of butyl acrylate and 50 wt % of ethyl acrylate.

[0096] In addition, the thickness of the solid electrolyte membrane for the all-solid-state battery is 100 μm.

[0097] Example 2

[0098] A solid electrolyte membrane was prepared in the same manner as that prepared in Example 1, except that the binder polymer used 25 wt % of acrylate and 75 wt % of NBR.

[0099] Comparative Example 1

[0100] A solid electrolyte membrane was prepared in the same manner as in Example 1, except that 100 wt % of acrylate was used as the binder polymer.

[0101] Comparative Example 2

[0102] A solid electrolyte membrane was prepared in the same manner as that prepared in Example 1, except that the binder polymer used 75 wt % of acrylate and 25 wt % of NBR.

[0103] Comparative Example 3

[0104] A solid electrolyte membrane was prepared in the same manner as in Example 1, except that 100 wt % of NBR was used as the binder polymer.

[0105] Comparative Example 4

[0106] A solid electrolyte membrane was prepared in the same manner as that prepared in Example 1, except that the binder polymer used 50 wt % of NBR and 50 wt % of polyimide (PI).

[0107] Comparative Example 5

[0108] A solid electrolyte membrane was prepared in the same manner as that prepared in Example 1, except that 50 wt % of NBR and 50 wt % of styrene ethylene butylene styrene (SEBS) were used as the binder polymer.

[0109] Comparative Example 6

[0110] A solid electrolyte membrane was prepared in the same manner as that prepared in Example 1, except that 50 wt % of NBR and 50 wt % of cyanoacrylate (CA) were used as the binder polymer.

[0111] Experimental Example 1: Measurement of ionic conductivity and flexibility

[0112] The ion conductivities of the solid electrolyte membranes for all-solid-state batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 5 were measured, and their flexibility was confirmed.

[0113] Figure 1a is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Example 1, Figure 1b Graphs showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Example 2.

[0114] Figure 2a is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 1, Figure 2b : is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 2, Figure 2c : is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 3, Figure 2d : is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 4, Figure 2e : is a diagram showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 5, Figure 2f Graphs showing the flexibility of the solid electrolyte membrane for an all-solid-state battery of Comparative Example 6.

[0115] The ionic conductivity was measured by placing aluminum foil on the upper and lower surfaces of a solid electrolyte membrane for an all-solid-state battery, assembling a fixture cell, and pressurizing it to 360 MPa.

[0116] The flexibility was measured 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.

[0117] The ionic conductivity and flexibility results of the solid electrolyte membrane are shown in Table 1 below.

[0118] [Table 1]

[0119]

[0120] According to the results in Table 1 above, Examples 1 and 2, which contain at least 25 wt% but less than 75 wt% of acrylate and 75 wt% or less and more than 25 wt% of NBR as binder polymers, exhibit excellent ionic conductivity and at the same time, exhibit excellent flexibility and no cracking. Comparative Example 1, which contains 100 wt% of acrylate based on the total weight of the binder polymer, has better ionic conductivity than Examples 1 and 2, but is found to be easily cracked and has no flexibility.

[0121] Comparative Example 2 contained 75 wt % of acrylate and 25 wt % of NBR relative to the total weight of the binder polymer and was found to have better ion conductivity than Examples 1 and 2, but was found to have no flexibility due to cracking.

[0122] Comparative Example 3 contained 100 wt % of NBR based on the total weight of the binder polymer and was found to have good flexibility, but the ionic conductivity was lower than that of Examples 1 and 2.

[0123] Comparative Example 4 contained 50 wt % of NBR and 50 wt % of polyimide (PI) based on the total weight of the binder polymer and was found to have good ion conductivity, but was found to have cracks and lack flexibility.

[0124] Comparative Example 5 contained 50% NBR and 50% styrene ethylene butylene styrene (SEBS) based on the total weight of the binder polymer and was found to have good flexibility but lower ionic conductivity than Examples 1 and 2.

[0125] Comparative Example 6 contained 50 wt % of NBR and 50 wt % of cyanoacrylate (CA) based on the total weight of the binder polymer and was found to have good ion conductivity, but was found to have cracks and lack flexibility.

[0126] Therefore, it can be seen that the solid electrolyte membrane for an all-solid-state battery containing at least 25 wt % but less than 75 wt % of acrylate and 75 wt % or less and more than 25 wt % of NBR relative to the total weight of the binder polymer has excellent ionic conductivity and flexibility.

[0127] Furthermore, it can be seen that combining NBR and a binder other than an acrylic binder as a binder polymer leads to a decrease in the ion conductivity of the electrolyte.

[0128] It can also be seen 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 membrane for an all-solid-state battery, comprising a solid electrolyte and a binder, wherein: The adhesive includes an acrylate-based adhesive and an NBR-based adhesive.

2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, in, The content of the acrylic adhesive is at least 25 wt % and less than 75 wt % based on the total weight of the adhesive.

3. The solid electrolyte membrane for an all-solid-state battery according to claim 1, in, The content of the NBR-based adhesive is 75 wt % or less and greater than 25 wt % based on the total weight of the adhesive.

4. The solid electrolyte membrane for an all-solid-state battery according to claim 1, in, The acrylic ester adhesive is an alkyl acrylate adhesive.

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

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

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

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

10. An all-solid-state battery, comprising: positive electrode, a negative electrode; and A solid electrolyte membrane disposed between the positive electrode and the negative electrode, in, The solid electrolyte membrane is the solid electrolyte membrane according to any one of claims 1 to 9.

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