Solid electrolyte membrane, method for manufacturing the same, and all-solid-state battery containing the same

Abstract

The present invention relates to a solid electrolyte membrane, a method for producing the same, and an all-solid-state battery including the same. More specifically, the solid electrolyte membrane includes a first solid electrolyte layer and a second solid electrolyte layer stacked adjacent to each other, wherein the first solid electrolyte layer has a structure in which particulate binders are simply dispersed, and the second solid electrolyte layer has a structure in which fibrous binders are intertwined or linked to each other, thereby improving the strength of the solid electrolyte membrane without reducing its ionic conductivity.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority under U.S. Patent Application No. 18 / 390,298 dated December 20, 2023, U.S. Patent Application No. 18 / 946,323 dated November 13, 2024, and Korean Patent Application No. 10-2024-0174801 dated November 29, 2024, and all content disclosed in the documents of said patent applications is incorporated herein by reference.

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

[0003] Electrified transportation methods, exemplified by the widespread application of electric vehicles (EVs) and the emergence of urban air transport (UAM) vehicles, continue to increase. Simultaneously, demand for fixed-line energy storage systems is growing, particularly in the residential and industrial sectors powered by solar and wind turbines. These changes stem from the negative environmental and climatic impacts caused by traditional internal combustion engines and other non-renewable power production methods. Therefore, technological development of batteries with high energy density, while ensuring improved safety, is becoming essential.

[0004] 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.

[0005] 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.

[0006] 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 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.

[0007] However, while all-solid-state batteries can ensure safety by using the solid electrolyte, there is a possibility of reduced ionic conductivity. Furthermore, if a liquid electrolyte is used in conjunction with the solid electrolyte to ensure its ionic conductivity, there is a problem of reduced strength.

[0008] Generally, in order to ensure the safety of all-solid-state batteries while simultaneously preventing a decline in battery performance and processability, the ionic conductivity and strength of the solid electrolyte membrane must all be maintained at a certain level or higher.

[0009] However, among the solid electrolyte membranes developed to date, there is still room for improvement in the technological development of solid electrolytes that possess both high ionic conductivity and high strength. Furthermore, as the demand for all-solid-state batteries increases, the demand for solid electrolyte membranes included in all-solid-state batteries is also increasing proportionally, thus necessitating the development of solid electrolyte membranes that excel in both ionic conductivity and strength.

[0010] In addition, in all-solid-state batteries, side reactions tend to occur at the interface between the solid electrolyte membrane containing the binder and the negative electrode, leading to a deterioration in battery performance. Therefore, there is an increasing demand for solid electrolyte membranes that prevent side reactions from occurring at the interface with the negative electrode.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] In order to solve the above problems, the inventors conducted extensive research and found that in a solid electrolyte membrane with two solid electrolyte layers laminated, by making the forms of the binders contained in the two solid electrolyte layers different and applying them as particulate binders and fibrous binders respectively, the strength was improved without a decrease in the ionic conductivity of the solid electrolyte membrane, and it was confirmed that side reactions were suppressed at the interface between the negative electrode and the solid electrolyte layer containing the particulate binder.

[0013] Therefore, an object of the present invention is to provide a solid electrolyte membrane with improved strength without a decrease in ionic conductivity and a method for manufacturing the same.

[0014] Another object of the present invention is to provide an all-solid-state battery including the solid electrolyte membrane.

Means for Solving the Problems

[0015] To achieve the above object, the present invention provides a solid electrolyte membrane including a first solid electrolyte layer and a second solid electrolyte layer formed on one surface of the first solid electrolyte layer, the first solid electrolyte layer includes a first solid electrolyte and a particulate binder, the second solid electrolyte layer includes a second solid electrolyte and a fibrous binder, The aforementioned solid electrolyte membrane provides a solvent-free solid electrolyte membrane.

[0016] In one embodiment of the present invention, the weight of the particulate binder may be less than 2% by weight, based on the total weight of the first solid electrolyte layer.

[0017] In one embodiment of the present invention, the weight of the fibrous binder may be 0.01% to 5% by weight, based on the total weight of the second solid electrolyte layer.

[0018] In one embodiment of the present invention, the particulate binder and the fibrous binder may each contain one or more selected from the group consisting of polytetrafluoroethylene (PTFE), ethylene-vinyl acetate (EVA), styrene-ethylene-butylene-styrene (SEBS), and copolymers containing these materials.

[0019] In one embodiment of the present invention, the first solid electrolyte or the second solid electrolyte may be a sulfide-based solid electrolyte, a halide-based solid electrolyte, or an oxide-based solid electrolyte.

[0020] In one embodiment of the present invention, the thickness of the solid electrolyte membrane may be 20 μm to 700 μm.

[0021] In one embodiment of the present invention, the ionic conductivity of the solid electrolyte membrane may be 0.5 mS / cm to 10 mS / cm.

[0022] In one embodiment of the present invention, the solid electrolyte membrane may be solvent-free.

[0023] The present invention also relates to a method for manufacturing a solid electrolyte membrane, which involves manufacturing a first solid electrolyte layer and a second solid electrolyte layer, and then joining them together. The first solid electrolyte layer is manufactured by the following steps (A1) to (A2): (A1) The step of mixing the first solid electrolyte particles and the first binder; and (A2) A step in which the mixture obtained in step (A1) is applied to a first calendering step to form a film and obtain a first solid electrolyte layer. The second solid electrolyte layer is manufactured by the following steps (B1) to (B2): (B1) The step of mixing the second solid electrolyte particles and the second binder; and (B2) A step in which the mixture obtained in step (B1) is applied to a second calendering step to form a film and obtain a second solid electrolyte layer. The present invention provides a method for manufacturing a solid electrolyte membrane, wherein the first binder is a particulate binder, and the second binder is fibrously formed during mixing to become a fibrous binder.

[0024] In one embodiment of the present invention, the temperatures of the first and second calendering steps may be 50°C to 200°C, respectively.

[0025] In one embodiment of the present invention, the first color rendering step may be performed for 1 to 10 loops, and the second color rendering step may be performed for 5 to 50 loops.

[0026] In one embodiment of the present invention, the calendering step may be performed uniaxially or biaxially.

[0027] The present invention also provides an all-solid-state battery comprising a positive electrode, a negative electrode, and the solid electrolyte membrane interposed between them.

[0028] In one embodiment of the present invention, the first solid electrolyte layer of the solid electrolyte membrane may be adjacent to the negative electrode.

[0029] In one embodiment of the present invention, the first solid electrolyte layer may be composed of a first solid electrolyte and a particulate binder, and the second solid electrolyte layer may be composed of a second solid electrolyte and a fibrous binder.

[0030] In one embodiment of the present invention, no solvent may be used during the production of the first solid electrolyte layer and the second solid electrolyte layer. [Effects of the Invention]

[0031] According to the solid electrolyte membrane of the present invention, two solid electrolyte layers, each containing particulate binders and fibrous binders of different forms, are manufactured separately by a dry process and then joined together to form a double layer structure. This has the effect of improving strength without reducing ionic conductivity.

[0032] Furthermore, in the all-solid-state battery containing the solid electrolyte membrane of the present invention, the solid electrolyte layer containing particulate binder among the bilayers contained in the solid electrolyte membrane is arranged to be in contact with the negative electrode, which has the effect of minimizing side reactions at the interface between the solid electrolyte membrane and the negative electrode. [Brief explanation of the drawing]

[0033] [Figure 1a] This is a schematic diagram showing a longitudinal cross-section of a solid electrolyte membrane according to one embodiment of the present invention. [Figure 1b] This is a schematic diagram showing a longitudinal cross-section of an all-solid-state battery including a solid electrolyte membrane according to one embodiment of the present invention. [Figure 2a] This is a schematic diagram of an all-solid-state battery manufactured for performance experiments based on the shape of the binder contained in a sulfide-based solid electrolyte membrane. [Figure 2b] This is a charge-discharge curve for an all-solid-state battery having the structure shown in Figure 2a. [Figure 3a] This is a schematic diagram of an all-solid-state battery manufactured for performance experiments based on the shape of the binder contained in a sulfide-based solid electrolyte membrane. [Figure 3b] This is the charge-discharge curve for an all-solid-state battery having the structure shown in Figure 3a. [Figure 4] This is the charge-discharge curve for the all-solid-state battery manufactured in Example 1. [Modes for carrying out the invention]

[0034] The present invention will be described in more detail below to aid in understanding the invention.

[0035] 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.

[0036] solid electrolyte membrane The present invention relates to a solid electrolyte membrane, the solid electrolyte membrane comprising a first solid electrolyte layer and a second solid electrolyte layer, wherein the shape of the binder contained in the first solid electrolyte layer and the second solid electrolyte layer is different.

[0037] Figure 1a is a schematic diagram showing a longitudinal cross-section of a solid electrolyte membrane according to one embodiment of the present invention.

[0038] Referring to Figure 1a, a solid electrolyte membrane (1) according to one embodiment of the present invention is a solid electrolyte membrane (1) comprising a first solid electrolyte layer (10) and a second solid electrolyte layer (20) formed on one surface of the first solid electrolyte layer (10), wherein the first solid electrolyte layer (10) comprises a first solid electrolyte (10a) and a particulate binder (10b), and the second solid electrolyte layer (20) comprises a second solid electrolyte (20a) and a fibrous binder (20b).

[0039] Since the first solid electrolyte layer is adjacent to the negative electrode and the binder contained within the first solid electrolyte layer is particulate, contact with the negative electrode can be minimized, and side reactions between the interface of the first solid electrolyte layer and the negative electrode can be reduced.

[0040] The form of the binder can be controlled by the number of loops of the first and second calendering processes performed during the manufacturing of the first and second solid electrolyte layers. The more loops of the calendering process there are, the more the binder can take on a fibrous form.

[0041] In one embodiment of the present invention, the particulate binder may be present in an amount of 2% by weight or less based on the total weight of the first solid electrolyte layer. The first solid electrolyte layer has a lower binder content than the adjacent second solid electrolyte layer, and this prevents the occurrence of side reactions at the interface with the negative electrode when the first solid electrolyte layer is positioned in contact with the negative electrode during the manufacture of an all-solid-state battery.

[0042] Specifically, the content of the particulate binder may be 2% by weight or less, 1.9% by weight or less, 1.8% by weight or less, 1.7% by weight or less, 1.6% by weight or less, 1.5% by weight or less, 1.4% by weight or less, 1.3% by weight or less, 1.2% by weight or less, 1.1% by weight or less, 1% by weight or less, 0.9% by weight or less, 0.8% by weight or less, 0.7% by weight or less, 0.6% by weight or less, or 0.5% by weight or less. If the content of the particulate binder exceeds 2% by weight, the ionic conductivity of the solid electrolyte membrane may decrease, and if the first solid electrolyte layer is arranged inside the all-solid-state battery so as to be in contact with the negative electrode, side reactions may occur at the interface with the negative electrode. The lower limit of the particulate binder content is not particularly limited and may be, for example, 0.4% by weight, 0.3% by weight, 0.2% by weight, or 0.1% by weight, within the range exceeding 0% by weight.

[0043] Furthermore, the particulate binder has an average particle size (D 50 ) may be 10 nm to 1 μm, and the average particle size (D 50 If the average particle size (D) is less than 10 nm, the slurry manufacturing process for solid electrolyte membrane fabrication may not proceed smoothly, and the average particle size (D) may be less than 10 nm. 50 If the thickness exceeds 1 μm, it can be difficult to uniformly distribute the binder within the solid electrolyte membrane.

[0044] D as used in this specification 50 This can be defined as the particle diameter at which the cumulative volume accounts for 50% of the particle size distribution curve (the curve in the particle size distribution graph) for each particle. 50 For example, this can be measured using laser diffraction. Laser diffraction can generally measure particle sizes ranging from submicron levels to several millimeters, and can produce highly repeatable and high-resolution results.

[0045] In one embodiment of the present invention, the fibrous binder may be present in an amount of 0.01% to 5% by weight based on the total weight of the second solid electrolyte layer. The fibrous binder may also be present in amounts of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, and 2% by weight based on the total weight of the second solid electrolyte layer. It may be included in amounts of 0.4% by weight, 2.5% by weight, 2.6% by weight, 2.7% by weight, 2.8% by weight, 2.9% by weight, 3.0% by weight, 3.1% by weight, 3.2% by weight, 3.3% by weight, 3.4% by weight, 3.5% by weight, 3.6% by weight, 3.7% by weight, 3.8% by weight, 3.9% by weight, 4.0% by weight, 4.1% by weight, 4.2% by weight, 4.3% by weight, 4.4% by weight, 4.5% by weight, 4.6% by weight, 4.7% by weight, 4.8% by weight, or 4.9% by weight.

[0046] If the content of the fibrous binder is less than 0.01% by weight, the strength of the solid electrolyte membrane may decrease, and if it exceeds 5% by weight, the ionic conductivity of the solid electrolyte membrane may decrease.

[0047] Furthermore, the fibrous binder may have an aspect ratio of 10 to 10,000. If the aspect ratio is less than 10, the number of cross-linked structures formed by the binder within the solid electrolyte membrane will be small, potentially resulting in weaker strength. If it exceeds 10,000, the time required for the manufacturing process may increase. The cross-linked structures formed by the binder can be described as a network structure that is intertwined like a net.

[0048] In one embodiment of the present invention, the particulate binder and the fibrous binder may each contain one or more selected from the group consisting of polytetrafluoroethylene (PTFE), ethylene-vinyl acetate (EVA), styrene-ethylene-butylene-styrene (SEBS), and copolymers containing one or more of PTFE, EVA, and SEBS. Furthermore, the particulate binder and the fibrous binder may be the same or different from each other.

[0049] In one embodiment of the present invention, the first solid electrolyte and the second solid electrolyte may each include one or more selected from the group consisting of sulfide-based solid electrolytes and halide-based solid electrolytes, and these may be the same or different from each other.

[0050] The sulfide-based solid electrolyte may include one or more selected from the group consisting of LiPSX (X = Cl, Br, or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these, and a wide range of sulfide-based solid electrolytes commonly used in the industry can be used.

[0051] Non-limiting examples of sulfide-containing solid electrolytes include Li-PS-based glass, Li-PS-based glass ceramics, and argyrodite-based sulfide-containing solid electrolytes.

[0052] Non-limiting examples of the sulfide-containing solid electrolyte include x Li2S- y P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2 or Li2S-GeS2-ZnS, Li6PS5X (X = one or more of Cl, Br or I), among others.

[0053] In one aspect, the sulfide-containing solid electrolyte may include one or more selected from LPS-based glass or glass-ceramics, such as x Li2S- y P2S5 or argyrodite-based sulfide-containing solid electrolytes (Li6PS5X; X = Cl, Br, I). In one aspect, the sulfide-containing solid electrolyte may be Li6PS5X.

[0054] Also, the halide-based solid electrolyte may be represented by the following Chemical Formula 1: <Chemical Formula 1> Li 6-3a M a Br b Cl c In Chemical Formula 1, M is a metal other than Li, a satisfies 0 < a < 2, b satisfies 0 ≤ b ≤ 6, c satisfies 0 ≤ c ≤ 6, and b + c = 6.

[0055] For example, the halide solid electrolyte may include one or more selected from the group consisting of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0056] [[ID=??]] Furthermore, since both the first solid electrolyte layer and the second solid electrolyte layer are manufactured by a dry process, the first solid electrolyte layer may contain a first solid electrolyte and a particulate binder, and the second solid electrolyte layer may contain a second solid electrolyte and a fibrous binder. Alternatively, the first solid electrolyte layer may consist of a first solid electrolyte and a particulate binder, and the second solid electrolyte layer may consist of a second solid electrolyte and a fibrous binder.

[0057] Furthermore, no solvent may be used during the manufacturing of the first solid electrolyte layer and the second solid electrolyte layer.

[0058] Furthermore, the solid electrolyte membrane may be substantially solvent-free. In one embodiment of the present invention, the phrase "substantially free" may allow for the inclusion of a small amount of solvent so as to satisfy the stated objectives of the present invention. For example, a small amount of solvent, such as less than 1% by weight, based on the total weight of the solid electrolyte membrane, may be permitted. Specifically, a small amount may be less than 0.95% by weight, less than 0.90% by weight, less than 0.85% by weight, less than 0.80% by weight, less than 0.75% by weight, less than 0.70% by weight, less than 0.65% by weight, less than 0.60% by weight, less than 0.55% by weight, less than 0.50% by weight, less than 0.45% by weight, less than 0.40% by weight, less than 0.35% by weight, less than 0.30% by weight, less than 0.25% by weight, less than 0.20% by weight, less than 0.15% by weight, less than 0.10% by weight, less than 0.05% by weight, less than 0.02% by weight, or less than 0.01% by weight, based on the total weight of the solid electrolyte membrane.

[0059] The content of the first solid electrolyte in the first solid electrolyte layer may be 98% by weight or more, specifically 98% by weight or more, 98.1% by weight or more, 98.2% by weight or more, 98.3% by weight or more, 98.4% by weight or more, 98.5% by weight or more, 98.6% by weight or more, 98.7% by weight or more, 98.8% by weight or more, 98.9% by weight or more, 99% by weight or more, 99.1% by weight or more, 99.2% by weight or more, 99.3% by weight or more, 99.4% by weight or more, or 99.5% by weight or more. If the content of the first solid electrolyte is less than 98% by weight, the ionic conductivity of the solid electrolyte membrane may decrease, and if it exceeds 99.5% by weight, the strength of the solid electrolyte membrane may decrease because the content of particulate binder decreases relatively.

[0060] Furthermore, the content of the second solid electrolyte in the aforementioned second solid electrolyte layer may be 95% to 99.99% by weight. The content of the solid electrolyte is determined based on the total weight of the aforementioned second solid electrolyte layer, and may be 95.1%, 95.2%, 95.3%, 95.4%, 95.5%, 95.6%, 95.7%, 95.8%, 95.9%, 96.0%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, 96.6%, 96.7%, 96.8%, and 96.9%. It may be included in amounts of wt%, 97.0 wt%, 97.1 wt%, 97.2 wt%, 97.3 wt%, 97.4 wt%, 97.5 wt%, 97.6 wt%, 97.7 wt%, 97.8 wt%, 97.9 wt%, 98.0 wt%, 98.1 wt%, 98.2 wt%, 98.3 wt%, 98.4 wt%, 98.5 wt%, 98.6 wt%, 98.7 wt%, 98.8 wt%, 98.9 wt%, or 99.9 wt%. If the content of the aforementioned second solid electrolyte is less than 95 wt%, the strength of the solid electrolyte membrane may decrease, and if it exceeds 99.99 wt%, the strength of the solid electrolyte membrane may decrease.

[0061] In one embodiment of the present invention, the thickness of the solid electrolyte membrane may be 20 μm to 700 μm. If the thickness of the solid electrolyte membrane is less than 20 μm, the strength will be weak, reducing processability and potentially causing short circuits during battery assembly and / or operation. If it exceeds 700 μm, the energy density of the battery may decrease.

[0062] Furthermore, the thickness of the first solid electrolyte layer adjacent to the negative electrode in the solid electrolyte membrane is 10 μm to 400 μm, and when it falls within this range, side reactions at the interface with the negative electrode can be minimized. The thickness of the second solid electrolyte layer formed adjacent to the first solid electrolyte layer may be 10 μm to 500 μm.

[0063] In one embodiment of the present invention, the ionic conductivity of the solid electrolyte membrane may be 0.5 mS / cm to 10 mS / cm. Specifically, the ionic conductivity may be 0.5 mS / cm or more, 0.6 mS / cm or more, 0.8 mS / cm or more, 1 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, or 2 mS / cm or more, and may be 3 mS / cm or less, 5 mS / cm or less, 8 mS / cm or less, or 10 mS / cm or less. The ionic conductivity may be measured at room temperature (25°C).

[0064] In one embodiment of the present invention, the tensile strength of the solid electrolyte membrane may be 45 kPa to 1000 kPa. Specifically, the tensile strength of the solid electrolyte membrane may be 45 kPa or more, 50 kPa or more, 80 kPa or more, 100 kPa or more, 120 kPa or more, or 150 kPa or more, and may be 200 kPa or less, 300 kPa or less, 500 kPa or less, 700 kPa or less, 900 kPa or less, or 1000 kPa or less.

[0065] In one embodiment of the present invention, the solid electrolyte membrane may be solvent-free.

[0066] The first solid electrolyte layer and the second solid electrolyte layer contained in the solid electrolyte membrane are both manufactured by a dry process that does not use a solvent, or preferably, is solvent-free. For example, the first solid electrolyte layer is manufactured by a dry process in which the first solid electrolyte and the first binder are physically mixed, and the second solid electrolyte layer is manufactured by a dry process in which the second solid electrolyte and the second binder are physically mixed, so they may be substantially solvent-free, or preferably solvent-free. Furthermore, when manufacturing the first solid electrolyte layer, particulate binder can be dispersed during the dry process. This makes it possible to manufacture a first solid electrolyte layer with improved strength due to the dispersion structure formed by the particulate binder formed during the dry process. The second solid electrolyte layer can also be manufactured in the same way, and when forming the second solid electrolyte layer, the calendering process loop is repeated more times, and fibrous binder can be formed, improving its strength. The solid electrolyte membrane formed by joining the first solid electrolyte layer and the second solid electrolyte layer manufactured in this way can have improved strength.

[0067] Furthermore, since no separate solvent is used, it is possible to prevent the phenomenon in which the crystalline structure of sulfide-based and / or halide-based solid electrolytes is destroyed by the solvent, leading to a decrease in ionic conductivity.

[0068] Generally, wet processes performed for the manufacture of solid electrolyte membranes use a solvent capable of dissolving the binder, allowing it to be positioned between solid electrolyte particles and provide adhesion. Conventional solvents used in wet processes, such as N-methyl-2-pyrrolidone (NMP), water, or ethanol, are polar solvents that can dissolve the binder and are suitable for wet processes. However, they react with sulfide-based solid electrolytes, making it difficult to use these polar solvents together with sulfide-based solid electrolytes. Therefore, solvents that do not react with sulfide-based solid electrolytes, such as xylene or anisole, are used as wet process solvents that can be used together with sulfide-based solid electrolytes. Furthermore, in wet processes using solvents such as xylene or anisole, nitrile-butadiene rubber (NBR), styrene-ethylene / butylene styrene (SEBS), etc., are used as binders that dissolve in these solvents.

[0069] On the other hand, the dry process according to the present invention does not use a solvent and physically stretches the binder in its initial particle form to form fibers. Therefore, the structure of the binder in the manufactured solid electrolyte membrane differs from the structure formed by the wet process, and the physical properties of the solid electrolyte membrane can also be improved compared to solid electrolyte membranes manufactured by the wet process. As mentioned above, the binder in its initial particle form undergoes physical deformation due to shear force when mixed with electrolyte particles. To induce such physical deformation, a mortar and pestle, ball mill, or roll press can be introduced during mixing. Furthermore, as a binder that can effectively induce physical deformation, a binder that is physically very weak and relatively prone to fiber formation, such as PTFE, can be used.

[0070] Method for manufacturing solid electrolyte membranes The present invention also relates to a method for producing a solid electrolyte membrane.

[0071] The method for manufacturing a solid electrolyte membrane according to the present invention involves manufacturing a first solid electrolyte layer and a second solid electrolyte layer separately, and then joining them together to produce a solid electrolyte membrane.

[0072] The first solid electrolyte layer is manufactured by the following steps (A1) to (A2): (A1) The step of mixing the first solid electrolyte particles and the first binder; and (A2) A step in which the mixture obtained in step (A1) is applied to the first calendering step to form a film.

[0073] The second solid electrolyte layer is manufactured by the following steps (B1) to (B2): (B1) The step of mixing the second solid electrolyte particles and the second binder; and (B2) A step in which the mixture obtained in step (B1) is applied to the second calendering step to form a film.

[0074] The first and second binders are fibrousized during mixing, becoming a particulate binder and a fibrous binder, respectively.

[0075] The substances and contents of the first solid electrolyte, the second solid electrolyte, the particulate binder, and the fibrous binder are as described above.

[0076] The form of the binder can be controlled by the number of loops of the first and second calendering processes performed during the manufacturing of the first and second solid electrolyte layers. The more loops of the calendering process there are, the more the binder can take on a fibrous form.

[0077] Furthermore, the particulate binder and the fibrous binder may be substantially the same in composition, differing only in the shape of the binder before and after the drying process.

[0078] Furthermore, the calendering process refers to the process of forming the target material in the calendering process into a film using two rollers. The pressure applied to the target material during the calendering process may be between 5 MPa and 200 MPa.

[0079] In one embodiment of the present invention, the method for joining the first solid electrolyte layer and the second solid electrolyte layer is not particularly limited as long as it is a joining method that can form a double layer in which the first solid electrolyte layer and the second solid electrolyte layer are stacked adjacent to each other.

[0080] For example, the first solid electrolyte layer and the second solid electrolyte layer can be bonded by simply stacking them, or they can be bonded by applying pressure after stacking.

[0081] In one embodiment of the present invention, the temperatures of the first and second calendering steps may be 50°C to 200°C, respectively. Specifically, the temperature may be 50°C or higher, 70°C or higher, or 80°C or higher, and may be 100°C or lower, 120°C or lower, 140°C or lower, 160°C or lower, 180°C or lower, or 200°C or lower. If the temperature is below 50°C, less fiber formation of the binder may occur, potentially reducing the strength of the solid electrolyte membrane. If the temperature exceeds 200°C, the strength of the solid electrolyte membrane may not increase further even if the temperature increases, or the electrolyte or binder material may deteriorate.

[0082] In one embodiment of the present invention, the first calendering step may be performed for 1 to 10 loops, and the second calendering step may be performed for 5 to 50 loops. Specifically, if the number of loops in the first calendering step is less than 1, the binder may not be able to improve the adhesion between the solid electrolyte particles, and if it exceeds 10 loops, the degree of fibrous formation of the binder increases, and as the binder becomes fibrous, the side reactions at the interface between the fibrous binder inside the first solid electrolyte layer adjacent to the negative electrode and the negative electrode may increase. Also, if the number of loops in the second calendering step is 5 to 10, the fibrous formation of the binder may not be smooth, but in this case, if the binder content is increased, the binder can be sufficiently fibroused by friction between the binders even if the number of loops is reduced. Therefore, when the number of loops in the second calendering step is 5 to 10, the content of the second binder can be set to 2% to 5% by weight so that the second binder is sufficiently fibroused. However, even if the content of the second binder is increased, if the number of loops in the second calendering step is less than 5, less fiber formation of the binder may occur, potentially reducing the strength of the solid electrolyte membrane. Also, if the number of loops in the second calendering step exceeds 50, even if the number of loops increases, the strength of the solid electrolyte membrane may not increase further, or the processability may worsen. The number of loops in the first calendering step may be 1 or more, 2 or more, or 3 or more, and may be 8 or less, 9 or less, or 10 or less. The number of loops in the second calendering step may be 5 or more, 10 or more, 15 or more, 20 or more, 23 or more, or 25 or more, and may be 35 or less, 40 or less, 45 or less, or 50 or less.

[0083] In one embodiment of the present invention, the orientation of the first and second calendering steps may be uniaxial or biaxial. In this case, uniaxial means that the calendering direction proceeds in one direction, and biaxial means that after the calendering proceeds in one direction, it proceeds alternately in the horizontal and vertical directions of the solid electrolyte membrane.

[0084] When the calendering process is carried out in a biaxial manner, fiber formation proceeds uniformly in multiple directions, further improving the strength of the solid electrolyte membrane.

[0085] In the method for manufacturing a solid electrolyte membrane as described above, the first solid electrolyte layer and the second solid electrolyte layer were manufactured in a dry process that did not use a solvent, but the method is not limited to this. For example, the first solid electrolyte layer can be manufactured in a wet process using a slurry coating step with a particulate binder. Alternatively, the second solid electrolyte layer can be manufactured in a wet process using a slurry coating step with a fibrous binder, in which the binder raw material itself is fibrous. Alternatively, the second solid electrolyte layer can be manufactured in a dry process using a fibrous binder, in which the binder raw material itself is fibrous. In this case, when manufacturing the first solid electrolyte layer or the second solid electrolyte layer in a wet process, the binder must be present in a certain amount or more based on the total weight of the first solid electrolyte layer or the second solid electrolyte layer, otherwise it will be impossible to form it into a membrane. For example, the binder may be present in an amount of 2% by weight or more based on the total weight of the first solid electrolyte layer or the second solid electrolyte layer.

[0086] all solid state battery The present invention also relates to an all-solid-state battery comprising the solid electrolyte membrane.

[0087] The all-solid-state battery according to the present invention includes a solid electrolyte membrane; a positive electrode formed on one surface of the solid electrolyte membrane; and a negative electrode formed on the other surface of the solid electrolyte membrane.

[0088] As described above, the solid electrolyte membrane includes a first solid electrolyte layer and a second solid electrolyte layer formed on one surface of the first solid electrolyte layer, wherein the first solid electrolyte layer contains a particulate binder and the second solid electrolyte layer contains a fibrous binder.

[0089] By ensuring that the first solid electrolyte layer, which contains a particulate binder, is in contact with the negative electrode, an all-solid-state battery can be formed.

[0090] The second solid electrolyte layer contains a fibrous binder. The fibrous binder tends to intertwine or link together, forming a network-like three-dimensional structure. The second solid electrolyte layer can form many network-like three-dimensional structures due to the fibrous binder. When the second solid electrolyte layer comes into contact with the negative electrode, side reactions may occur at the interface between the second solid electrolyte layer and the negative electrode, centered around the network-like three-dimensional structure formed by the fibrous binder.

[0091] Figure 1b is a schematic diagram showing a longitudinal cross-section of an all-solid-state battery including a solid electrolyte membrane according to one embodiment of the present invention.

[0092] Similar to Figure 1a, the solid electrolyte membrane in Figure 1b is a solid electrolyte membrane (1) comprising a first solid electrolyte layer (10) and a second solid electrolyte layer (20) formed on one surface of the first solid electrolyte layer (10), wherein the first solid electrolyte layer (10) comprises a first solid electrolyte (10a) and a first particulate binder (10b), and the second solid electrolyte layer (20) comprises a second solid electrolyte (20a) and a second fibrous binder (20b), characterized in that the weight of the first particulate binder (10b) relative to the total weight of the first solid electrolyte layer (10) is less than the weight of the second fibrous binder (20b) relative to the total weight of the second solid electrolyte layer (20). In an all-solid-state battery, the solid electrolyte membrane is interposed between the positive electrode (30) and the negative electrode (40), and the first solid electrolyte layer (10) is in contact with the negative electrode (40), for example, by direct contact.

[0093] Therefore, in order to prevent side reactions at the interface between the solid electrolyte membrane and the negative electrode, the first solid electrolyte layer containing particulate binder and the negative electrode are adjacent to each other, thereby enabling the manufacture of an all-solid-state battery.

[0094] In one embodiment of the present invention, the positive electrode may include a positive electrode active material, a conductive material, and a binder.

[0095] In the present invention, the positive electrode included in the all-solid-state battery includes a positive electrode active material layer, and the positive electrode active material layer may be formed on one or both sides of the positive electrode current collector.

[0096] The positive electrode active material layer comprises a positive electrode active material, a conductive material, and a binder.

[0097] Furthermore, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly intercalating and releasing lithium ions, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li[Ni x Co y Mn z M v ]O2(In the above formula, M is one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(Li a M b-a-b’ M' b’ )O 2-c A c Layered compounds such as (wherein the above formula, 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M comprises Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N) or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-yNi-site type lithium nickel oxide represented by MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides represented by O2 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc. are examples, but are not limited to these.

[0098] Furthermore, the positive electrode active material may be present in an amount of 60% to 80% by weight, based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 60% or more by weight, 65% or more by weight, or 68% or more by weight, and may be 72% or less by weight, 75% or less by weight, or 80% or less by weight. If the content of the positive electrode active material is less than 60% by weight, the battery performance may decrease, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0099] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not induce chemical changes in the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, and lamp black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in mixtures of two or more, but are not necessarily limited to these. Preferably, the conductive material may also contain vapor-grown carbon fiber (VGCF).

[0100] The conductive material may typically be present in an amount of 1% to 5% by weight relative to the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 1% or more by weight, 1.5% or more by weight, or 2% or more by weight, or 4% or less by weight, 4.5% or less by weight, or 5% or less by weight. If the content of the conductive material is too low (less than 1% by weight), it may be difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it is too high (more than 5% by weight), the amount of positive electrode active material will be relatively small, and the capacity and energy density may decrease. The method of incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as mixing with the positive electrode active material or coating, can be used.

[0101] Furthermore, the binder contains components that assist in the bonding of the positive electrode active material to conductive materials and to the current collector, such as styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, and polyacrylic. The binder may contain one or more selected from the group consisting of polynitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may contain polytetrafluoroethylene (PTFE).

[0102] Furthermore, the binder may be included in an amount of 0.5% to 4% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 0.5% or more by weight, 1% or more by weight, or 1.5% or more by weight, or 3% or less by weight, 3.5% or less by weight, or 4% or less by weight. If the binder content is less than 0.5% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 4% by weight, the adhesive strength will improve, but the content of the positive electrode active material will decrease accordingly, which may reduce the battery capacity.

[0103] Furthermore, the positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between the external conductor and the positive electrode active material layer.

[0104] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the all-solid-state battery and has high electronic conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloy can be used as the positive electrode current collector.

[0105] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. As a result, the positive electrode current collector can take various forms, such as film, sheet, foil, mesh, net, porous material, foam, nonwoven fabric, etc.

[0106] The positive electrode described above can be manufactured by conventional methods. Specifically, it can be manufactured by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent to produce a composition for forming a positive electrode active material layer, which is then coated onto a positive electrode current collector and dried, and then compression-molded onto the current collector to selectively improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, etc.

[0107] In the present invention, the negative electrode included in the all-solid-state battery includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one or both sides of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a binder, and a conductive material.

[0108] The negative electrode active material is lithium (Li +This may include materials that can be reversibly intercalated or deintercalated, materials that can react with lithium ions to reversibly form lithium-containing compounds, lithium metals, or lithium alloys.

[0109] The aforementioned lithium ion (Li + The material that can reversibly insert or remove lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + A substance that can reversibly form a lithium-containing compound by reacting with ) may be, for example, tin oxide, titanium nitrate, or silicone. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0110] Preferably, the negative electrode active material may be lithium metal or lithium-indium alloy (Li-In), and more specifically, it may be in the form of lithium metal or lithium in thin film or lithium-indium alloy thin film or powder.

[0111] The negative electrode active material may be present in an amount of 40% to 80% by weight, based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0112] Furthermore, the binder is as described above for the positive electrode active material layer.

[0113] Furthermore, the conductive material is as described above for the positive electrode active material layer.

[0114] Furthermore, the negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. Also, similar to the positive electrode current collector, the negative electrode current collector can be made of various forms such as films, sheets, foils, nets, porous materials, foams, nonwoven fabrics, etc., with fine irregularities formed on the surface.

[0115] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the industry. For example, methods such as crimping, coating, and vapor deposition can be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial charging after the battery has been assembled without a lithium thin film on the negative electrode current collector.

[0116] Manufacturing method for all-solid-state batteries The present invention also relates to a method for manufacturing an all-solid-state battery.

[0117] The method for manufacturing an all-solid-state battery according to the present invention includes the steps of (P1) positioning a mixture for forming a positive electrode active material layer on one surface of a solid electrolyte membrane and applying pressure to form a positive electrode on that surface of the solid electrolyte membrane; and (P2) positioning a negative electrode on the other surface of the solid electrolyte membrane and applying pressure. At this time, the solid electrolyte membrane includes a first solid electrolyte layer and a second solid electrolyte layer formed on one surface of the first solid electrolyte layer, wherein the first solid electrolyte layer contains a particulate binder and the second solid electrolyte layer contains a fibrous binder.

[0118] A solid-state battery can be manufactured by arranging the first solid electrolyte layer contained in the solid electrolyte membrane and the negative electrode adjacent to each other. In this case, the particulate binder contained in the first solid electrolyte layer exists in a simply dispersed form within the first solid electrolyte and does not intertwine with each other or form a connected network-like three-dimensional structure like a fibrous binder. Therefore, side reactions can be prevented at the interface between the first solid electrolyte layer and the negative electrode.

[0119] In step (P1), a mixture for forming a positive electrode active material layer is positioned on one surface of the solid electrolyte membrane and subjected to high temperature and pressure to form a positive electrode on that surface of the solid electrolyte membrane.

[0120] The mixture for forming the positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder. The specific types and weights of these are as described above. Furthermore, a positive electrode can be manufactured by attaching a current collector after the positive electrode active material layer has been formed.

[0121] Furthermore, the pressurization step is used to bond the solid electrolyte membrane and the positive electrode, reducing interfacial resistance to achieve bonding, and may be performed at a pressure of 300 MPa to 500 MPa. The pressure of the high-temperature pressurization step may be 300 MPa or higher, 350 MPa or higher, or 400 MPa or higher, and may be 450 MPa or lower, 470 MPa or lower, or 500 MPa or lower. If the temperature and / or pressure of the high-temperature pressurization step is below the above range, the solid electrolyte membrane and the positive electrode may not be integrated, and if it exceeds the above range, the solid electrolyte membrane or the positive electrode may be deformed or damaged.

[0122] In step (P2), a negative electrode can be positioned on the other side of the solid electrolyte membrane and pressurized to manufacture an all-solid-state battery. The negative electrode is described above.

[0123] The pressure during pressurization may be between 40 MPa and 80 MPa. Specifically, the pressure during pressurization may be 40 MPa or more, 45 MPa or more, or 50 MPa or more, and may be 70 MPa or less, 75 MPa or less, or 80 MPa or less. If the pressure during pressurization is less than 40 MPa, the interfacial resistance between the negative electrode and the solid electrolyte membrane may increase, and if it exceeds 80 MPa, the solid electrolyte or negative electrode may deform or break.

[0124] Because all-solid-state batteries manufactured in this way contain a thin solid electrolyte, the manufacturing cost can be reduced, and the ion conductance and energy density can be improved.

[0125] Furthermore, since the solid electrolyte and the positive electrode are integrated by a high-temperature and high-pressure process, interfacial stability can be improved.

[0126] Battery module The present invention also relates to a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source.

[0127] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by electric motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0128] 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 such changes and modifications will naturally fall within the scope of the attached claims.

[0129] In the following examples and comparative examples, solid electrolyte membranes and all-solid-state batteries were manufactured according to the compositions and processes described in Table 1 below.

[0130] [Table 1]

[0131] Example 1 1-1. Manufacturing of the first and second solid electrolyte layers The first and second solid electrolyte layers were manufactured using a solvent-free dry process as described below.

[0132] A first solid electrolyte layer with a thickness of 200 μm was produced by mixing Li6PS5Cl powder, a sulfide-based solid electrolyte, with PTFE particles (polytetrafluoroethylene, Chemours), a first binder, in a mortar and pestle. The mixture obtained was subjected to five calendaring loops in a roll press at a temperature of 90°C and under biaxial orientation conditions. The first solid electrolyte and the first binder were mixed at concentrations of 99.8% by weight and 0.2% by weight, respectively.

[0133] A second solid electrolyte layer with a thickness of 400 μm was produced by mixing Li6PS5Cl powder, a sulfide-based solid electrolyte, with PTFE particles (polytetrafluoroethylene, Chemours), a second binder, in a mortar. The mixture obtained was subjected to 30 calendaring loops in a roll press at a temperature of 90°C and under biaxial orientation conditions. The second solid electrolyte and the second binder were mixed at concentrations of 99.5% by weight and 0.5% by weight, respectively.

[0134] 1-2. Manufacturing of Solid Electrolyte Membranes A solid electrolyte membrane was manufactured by laminating the second solid electrolyte layer onto one surface of the first solid electrolyte layer and then bonding them together under pressure at 5 MPa. The thickness of the solid electrolyte membrane is 600 μm.

[0135] 1-3. Manufacturing of All-Solid-State Batteries A positive electrode (NCM811, LGChem), a solid electrolyte membrane manufactured in steps 1-2 above, and a negative electrode (Si powder, Alfa Aesar) were sequentially stacked to manufacture an all-solid-state battery. At this time, the first solid electrolyte layer of the solid electrolyte membrane was in contact with the negative electrode.

[0136] Example 2 A solid electrolyte membrane and an all-solid-state battery were manufactured in the same manner as in Example 1, except that 98% by weight of the second solid electrolyte and 2% by weight of the second binder were mixed and a caravendering loop was performed 30 times.

[0137] Example 3 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the thickness of the second solid electrolyte layer was 200 μm.

[0138] Comparative Example 1 We attempted to manufacture a solid electrolyte membrane and an all-solid-state battery in the same manner as in Example 1, except that the first and second solid electrolyte layers were manufactured in a wet process using a solvent as described below.

[0139] For the aforementioned wet process, a xylene solvent, which is stable in sulfide-based solid electrolytes, was used as the solvent.

[0140] A solution was prepared by dissolving PTFE particles, which are the first binder, in xylene solvent at a concentration of 0.2% by weight. This solution was mixed with Li6PS5Cl powder, a sulfide-based solid electrolyte, as the first solid electrolyte. The mixture was then coated onto a PET (polyethylene terephthalate) release film using a doctor blade, and the film was vacuum-dried at 100°C for 12 hours to form the first solid electrolyte layer. However, the adhesive strength was weak, and the first solid electrolyte layer was not formed in the form of a film. Therefore, it was not possible to manufacture a solid electrolyte film in which the first and second solid electrolyte layers were laminated.

[0141] Comparative Example 2 A slurry was prepared by mixing 98% by weight of the sulfide-based solid electrolyte Li6PS5Cl and 2% by weight of the binder SEBS (Styrene-ethylene-butylene-styrene) with xylene as a solvent. At this time, the slurry concentration was set to 60% by weight of the sulfide-based solid electrolyte and 40% by weight of the solvent.

[0142] The slurry was coated onto a PET (polyethylene terephthalate) release film using a doctor blade, and then dried at a temperature of 80°C to produce a solid electrolyte membrane with a thickness of 50 μm.

[0143] Because the appropriate number of calendering processes are not followed, the binder is in a granular form.

[0144] Comparative Example 3 As the solid electrolyte membrane, only the first solid electrolyte layer of Example 1, which contains particulate binder, was used.

[0145] Comparative Example 4 As the solid electrolyte membrane, only the second solid electrolyte layer of Example 1, which contains a fibrous binder, was used.

[0146] Comparative Example 5 As the solid electrolyte membrane, only the second solid electrolyte layer produced in Example 2 was used.

[0147] Experimental Example 1: Measurement of Ionic Conductivity of Solid Electrolyte Membranes To determine the ionic conductivity based on the shape of the binder contained in the solid electrolyte membrane and the morphology of the solid electrolyte membrane, the ionic conductivity was measured using the following method.

[0148] To measure the ionic conductivity of a solid electrolyte membrane, the membrane was placed in a 10 mm diameter polyether ether ketone (PEEK) holder, and a titanium rod was used as a blocking electrode to measure the ionic conductivity.

[0149] Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C with an amplitude of 10mV and a scan range from 1Hz to 0.1MHz. The ionic conductivity of the solid electrolyte membrane was then calculated using Equation 1 below. [Formula 1]

number

[0150] In Equation 1 above, σi is the ionic conductivity of the solid electrolyte membrane (mS / cm), R is the resistance of the solid electrolyte membrane measured by the electrochemical impedance spectrometer (Ω), L is the thickness of the solid electrolyte membrane (μm), and A is the area of ​​the solid electrolyte membrane (cm²). 2 ) means.

[0151] The measured ionic conductivity values ​​are listed in Table 2 below.

[0152] [Table 2]

[0153] Referring to Table 2 above, the solid electrolyte membranes of Examples 1 to 3 exhibited ionic conductivity sufficient for application in all-solid-state batteries.

[0154] Furthermore, in Comparative Example 1, an attempt was made to manufacture a solid electrolyte membrane containing a first solid electrolyte layer and a second solid electrolyte layer using a wet process. However, because the first and second binders, PTFE, are soluble in xylene solvent, the membrane was not manufactured, and as a result, the ionic conductivity could not be measured.

[0155] Furthermore, in Comparative Example 2, SEBS, a binder insoluble in xylene solvent, was used, but a relatively large amount of binder (2% by weight) was used, and it was confirmed that a solid electrolyte membrane was manufactured in a wet process, and the ionic conductivity was relatively lower compared to Examples 1-3.

[0156] Furthermore, Comparative Example 3 is a solid electrolyte membrane, which is the first solid electrolyte layer produced by the dry process in Example 1 (5 kallering loops). Because it has a low content of 0.2% by weight of the first binder, is in a single-layer form, has fewer kallering loops, and the first binder is in a particulate form, it showed higher ionic conductivity compared to Example 1. However, because it is in a single-layer form, it can be predicted that its strength will be weaker compared to Example 1, which is in a double-layer form.

[0157] Furthermore, Comparative Example 4 is a solid electrolyte membrane, which is the second solid electrolyte layer produced by the dry process in Example 1 (30 calendering loops). It has a low content of 0.5% by weight of the second binder and is in a single-layer form. Although it showed high ionic conductivity at a similar level to Example 1, it can be predicted that its strength will be weaker compared to Example 1, which is in a double-layer form, because it is in a single-layer form.

[0158] Comparative Example 5 is a solid electrolyte membrane, which is the second solid electrolyte layer produced by the dry process in Example 2 (30 kallering loops). Because it contains a high amount of the second binder (2% by weight) and has a large number of kallering loops, and the second binder exhibits a fibrous morphology, it may have higher strength, but its ionic conductivity was slightly lower. Furthermore, since the solid electrolyte membrane was a single-layer structure, its strength is expected to be weaker compared to Example 2, which had a double-layer structure.

[0159] Experimental Example 2: Correlation between binder shape and all-solid-state battery performance We conducted experiments to confirm the effect of the binder shape contained in the solid electrolyte membrane on the performance of all-solid-state batteries.

[0160] The all-solid-state battery was designed with a structure including a positive electrode (NCM811:LPSCl:VGCF (Vapor Grown Carbon Fiber) = 66:31:3 (wt%)), a negative electrode (Li, Li-In, or Si), and a sulfide-based solid electrolyte membrane (SSE, Solid-state electrolyte) interposed between them.

[0161] The sulfide-based solid electrolyte membrane included in the all-solid-state battery shown in Figure 2a(a) was prepared according to the method for producing the second sulfide-based solid electrolyte layer in Example 1, so that the fibrous PTFE binder content was 5 wt% (5 wt% PTFE SSE).

[0162] The sulfide-based solid electrolyte membrane included in the all-solid-state battery shown in Figure 2a(b) is formed as a bilayer, and the bilayer contains a sulfide-based solid electrolyte membrane without a fibrous PTFE binder (0wt% PTFE SSE) and a sulfide-based solid electrolyte membrane with a PTFE content of 5wt% (5wt% PTFE SSE), which is a fibrous PTFE binder. The all-solid-state battery was manufactured so that the sulfide-based solid electrolyte membrane without the binder (0wt% PTFE SSE) is in contact with the negative electrode (Li-In).

[0163] Figure 2b shows the charge-discharge curve for an all-solid-state battery having the structure shown in Figure 2a (positive electrode loading 2.5 mAh·cm). -2 (C rate: 0.1C). Figures 2b(a) and (b) are charge-discharge curves for all-solid-state batteries corresponding to Figures 2a(a) and (b), respectively.

[0164] Referring to Figure 2b(a), it can be seen that in an all-solid-state battery, when a sulfide-based solid electrolyte membrane containing a fibrous PTFE binder comes into contact with the negative electrode, side reactions between the fibrous PTFE binder and the negative electrode make it difficult for the battery to operate normally.

[0165] Referring to Figure 2b(b), it can be seen that when a sulfide-based solid electrolyte film without fibrous PTFE binder is formed on the surface in contact with the negative electrode, the side reaction between the fibrous PTFE binder and the negative electrode is prevented, thus improving the lifespan of the all-solid-state battery.

[0166] Figure 3a(a) shows the bilayer structure of the sulfide-based solid electrolyte membrane contained in the all-solid-state battery. According to the manufacturing method of the sulfide-based solid electrolyte membrane of Example 1, the first solid electrolyte layer contained 0.5% by weight of particulate PTFE binder, and the second solid electrolyte layer contained fibrous PTFE binder. In the first solid electrolyte layer, five calendering loops were performed to make the PTFE binder particulate.

[0167] Figure 3a(b) shows the bilayer structure of the sulfide-based solid electrolyte membrane contained in the all-solid-state battery. In Example 1, both the first and second solid electrolyte layers of the sulfide-based solid electrolyte membrane underwent a calendering process 30 times each, resulting in each layer containing 0.5% by weight of fibrous PTFE binder.

[0168] Figure 3b shows the charge-discharge curve for an all-solid-state battery having the structure shown in Figure 3a (positive electrode loading 2.5 mAh·cm). -2 (C rate: 0.1C). Figures 3b(a) and (b) are charge-discharge curves for all-solid-state batteries corresponding to Figures 3a(a) and (b), respectively.

[0169] Referring to Figure 3b(a), it can be seen that in an all-solid-state battery, when a sulfide-based solid electrolyte membrane containing particulate PTFE binder, rather than fibrous PTFE binder, comes into contact with the negative electrode, the side reactions between the particulate PTFE binder and the negative electrode are completed early, and the charging capacity of the all-solid-state battery increases.

[0170] Referring to Figure 3b(b), it can be seen that in an all-solid-state battery, when a sulfide-based solid electrolyte membrane containing a fibrous PTFE binder comes into contact with the negative electrode, side reactions between the fibrous PTFE binder and the negative electrode make it difficult for the battery to operate normally. Furthermore, the side reactions may persist along the fibrous PTFE binder, eventually reaching the positive electrode and potentially causing a soft short circuit.

[0171] Therefore, we were able to confirm that, for the normal operation and performance improvement of all-solid-state batteries, a particulate form of the binder contained in the sulfide-based solid electrolyte membrane adjacent to the negative electrode is more advantageous than a fibrous form.

[0172] Experimental Example 3: Evaluation of Cycle Characteristics of All-Solid-State Batteries The cycle characteristics of the all-solid-state battery manufactured in Example 1 were evaluated. The all-solid-state battery manufactured in Example 1 is a full cell containing a negative electrode (Si), a bilayer solid electrolyte membrane (Bilayer SSE-1), and a positive electrode (NCM).

[0173] The cycle characteristics of all-solid-state batteries were evaluated by performing charge and discharge at room temperature with a constant positive electrode loading amount, a constant current rate (C rate), and a constant negative electrode / positive electrode capacity ratio (N / P ratio), and then evaluating the discharge capacity retention rate.

[0174] Figure 4 shows the charge-discharge curve for the all-solid-state battery manufactured in Example 1 (positive electrode loading 2.5 mAh·cm). -2 ;C rate:0.1C;N / P Ratio:1.2).

[0175] Referring to Figure 4, it can be seen that the all-solid-state battery manufactured in Example 1 has a high discharge capacity retention rate.

[0176] Furthermore, the discharge capacity of the all-solid-state battery in Example 1 was measured up to 200 cycles, and cycle performance experiments were conducted (positive electrode loading: 2.5 mAh·cm). -2 (C rate: 0.33C; N / P Ratio: 1.2). As a result, it was confirmed that the all-solid-state battery of Example 1 maintained a similar level of discharge capacity up to 200 cycles.

[0177] Although the present invention has been described in part by limited embodiments and drawings, it is understood that the present invention is not limited thereto, and that various modifications and variations are possible within the equivalent scope of the technical concept of the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0178] 1: Solid electrolyte membrane 10: First solid electrolyte layer 10a: First solid electrolyte, 10b: Particulate binder 20:Second solid electrolyte layer 20a: Second solid electrolyte, 20b: Fibrous binder 30: Positive electrode 40: Negative electrode

Claims

1. A solid electrolyte membrane comprising a first solid electrolyte layer and a second solid electrolyte layer formed on one surface of the first solid electrolyte layer, The first solid electrolyte layer comprises a first solid electrolyte and a particulate binder, wherein the weight of the particulate binder is 2% by weight or less based on the total weight of the first solid electrolyte layer. The second solid electrolyte layer comprises a second solid electrolyte and a fibrous binder, wherein the weight of the fibrous binder is 0.01% to 5% by weight, based on the total weight of the second solid electrolyte layer. The solid electrolyte membrane is a solvent-free solid electrolyte membrane.

2. The solid electrolyte membrane according to claim 1, wherein the content of the first solid electrolyte is 98% by weight or more, based on the total weight of the first solid electrolyte layer.

3. The solid electrolyte membrane according to claim 1, wherein the content of the second solid electrolyte is 95% to 99.99% by weight, based on the total weight of the second solid electrolyte layer.

4. The solid electrolyte membrane according to claim 1, wherein the particulate binder and the fibrous binder each contain one or more selected from the group consisting of polytetrafluoroethylene (PTFE), ethylene-vinyl acetate (EVA), styrene-ethylene-butylene-styrene (SEBS), and copolymers containing the same.

5. The solid electrolyte membrane according to claim 1, wherein the first solid electrolyte or the second solid electrolyte is a sulfide-based solid electrolyte, a halogen-based solid electrolyte, or an oxide-based solid electrolyte.

6. The solid electrolyte membrane according to claim 1, wherein the thickness of the solid electrolyte membrane is 20 μm to 700 μm.

7. The solid electrolyte membrane according to claim 1, wherein the ionic conductivity of the solid electrolyte membrane is 0.5 mS / cm to 10 mS / cm.

8. The solid electrolyte membrane according to claim 1, wherein the solid electrolyte membrane is solvent-free.

9. The solid electrolyte membrane according to claim 1, wherein the first solid electrolyte layer is composed of a first solid electrolyte and a particulate binder, and the second solid electrolyte layer is composed of a second solid electrolyte and a fibrous binder.

10. The solid electrolyte membrane according to claim 1, wherein no solvent is used during the manufacture of the first solid electrolyte layer and the second solid electrolyte layer.

11. The particulate binder and the fibrous binder contain polytetrafluoroethylene (PTFE), and the first solid electrolyte and the second solid electrolyte contain Li ６ PS ５ A solid electrolyte membrane according to claim 1, comprising Cl.

12. A method for manufacturing a solid electrolyte membrane, which includes the step of manufacturing a first solid electrolyte layer and a second solid electrolyte layer, and then joining them together. The first solid electrolyte layer is manufactured by the following steps (A1) to (A2): (A1) The step of mixing the first solid electrolyte particles and the first binder; and (A2) A step in which the mixture obtained in step (A1) is applied to a first calendering step to form a film and obtain a first solid electrolyte layer. The second solid electrolyte layer is manufactured by the following steps (B1) to (B2): (B1) The step of mixing the second solid electrolyte particles and the second binder; and (B2) A step in which the mixture obtained in step (B1) is applied to a second calendering step to form a film and obtain a second solid electrolyte layer. A method for producing a solid electrolyte membrane, wherein the first binder becomes a particulate binder, and the second binder is fibrously converted into a fibrous binder during mixing.

13. The method for producing a solid electrolyte membrane according to claim 12, wherein the temperatures of the first and second calendering steps are 50°C to 200°C, respectively.

14. The method for producing a solid electrolyte membrane according to claim 13, wherein the first calendering step is performed for 1 to 10 loops, and the second calendering step is performed for 5 to 50 loops.

15. The method for producing a solid electrolyte membrane according to claim 12, wherein the calendering step is performed uniaxially or biaxially.

16. A method for producing a solid electrolyte membrane according to claim 12, wherein the first solid electrolyte layer is composed of a first solid electrolyte and a particulate binder, and the second solid electrolyte layer is composed of a second solid electrolyte and a fibrous binder.

17. A method for manufacturing a solid electrolyte membrane according to claim 12, wherein no solvent is used during the production of the first solid electrolyte layer and the second solid electrolyte layer.

18. The particulate binder and the fibrous binder contain polytetrafluoroethylene (PTFE), and the first solid electrolyte and the second solid electrolyte contain Li ６ PS ５ A method for producing a solid electrolyte membrane according to claim 12, comprising Cl.

19. An all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between them, according to any one of claims 1 to 11.

20. The all-solid-state battery according to claim 19, wherein the first solid electrolyte layer of the solid electrolyte membrane is adjacent to the negative electrode.

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