Method for manufacturing solid electrolyte membranes

Abstract

The present invention relates to a method for manufacturing a solid electrolyte membrane. More specifically, a solid electrolyte membrane can be manufactured by fibrosing a small amount of binder through the dry calendering process. The fibrous binder contained within the solid electrolyte membrane is intertwined with each other, and therefore exhibits excellent properties in both ionic conductivity and strength.

Description

[Technical Field]

[0001] This application claims priority under U.S. Patent Application No. 18 / 234,286 dated August 15, 2023, Korean Patent Application No. 10-2023-0124429 dated September 19, 2023, and Korean Patent Application No. 10-2024-0108292 dated August 13, 2024, and all content disclosed in the literature of said U.S. and Korean patent applications is incorporated herein by reference.

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

[0003] Lithium-ion batteries have limitations in terms of capacity, safety, output, size, and miniaturization. Therefore, various types of batteries are being researched to overcome these limitations of lithium-ion batteries.

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

[0005] A solid-state battery is a battery in which the liquid electrolyte used in conventional lithium-ion secondary batteries is replaced with a solid. Therefore, since no flammable solvent is used in the battery, ignition or explosion due to the decomposition reaction of conventional electrolytes does not occur at all, thus greatly improving safety. In addition, since 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.

[0006] However, while all-solid-state batteries can ensure safety by using the solid electrolyte, their ionic conductivity may decrease. Furthermore, using a liquid electrolyte in combination with the solid electrolyte to ensure its ionic conductivity presents a problem of reduced strength.

[0007] Generally, in order to ensure the safety of all-solid-state batteries while preventing a decrease in their performance and uniformity, both the ionic conductivity and strength of the solid electrolyte must be maintained at a certain level or higher.

[0008] As the demand for all-solid-state batteries increases, the demand for solid electrolytes contained in them is also increasing proportionally. Therefore, there is a need to develop processes that can produce solid electrolytes with excellent ionic conductivity and strength. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent Publication No. 2022-0095689 [Overview of the project] [Problems that the invention aims to solve]

[0010] The inventors conducted multifaceted research to solve the aforementioned problems and confirmed that when a solid electrolyte membrane is manufactured through a calendering process, it is possible to produce a solid electrolyte membrane with excellent ionic conductivity and strength by controlling the optimal temperature, orientation, and loop. The calendering process includes physically mixing a sulfide-based solid electrolyte and / or a halide-based solid electrolyte with a binder, followed by the step of fiberizing the binder. The structure formed by the fiberized binder may vary depending on the temperature, orientation, and loop of the calendering process.

[0011] Therefore, an object of the present invention is to provide a method for manufacturing a solid electrolyte membrane with improved ionic conductivity and strength.

Means for Solving the Problems

[0012] To achieve the above object, the present invention includes: (S1) a step of mixing solid electrolyte particles and a binder; (S2) a step of applying the mixture obtained in the step (S1) to a calendaring process to form it into a film shape, and the binder is fibrillated by the mixing. The present invention provides a method for manufacturing a solid electrolyte membrane.

[0013] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the temperature of the calendaring process is 50°C to 200°C.

[0014] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the calendaring process is performed between 5 loops and 50 loops.

[0015] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the calendaring process is performed uniaxially or biaxially.

[0016] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the steps (S1) and (S2) are performed in a solvent-free manner.

[0017] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the solid electrolyte particles include one or more selected from the group consisting of sulfide-based solid electrolyte particles and halide-based solid electrolyte particles.

[0018] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the solid electrolyte membrane is composed of solid electrolyte particles and a fibrous binder.

[0019] The present invention also provides a method for producing a solid electrolyte membrane, wherein the fibrous binder comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same.

[0020] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is contained in an amount of 2% by weight or less based on the total weight of the solid electrolyte membrane.

[0021] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is contained in the solid electrolyte membrane in a dispersed state.

[0022] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the interface between the solid electrolyte particles and the fibrous binder is bonded together.

[0023] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the ionic conductivity of the solid electrolyte membrane is 0.5 mS / cm to 10 mS / cm.

[0024] The present invention also provides a method for manufacturing a solid electrolyte membrane having a tensile strength of 45 kPa to 1000 kPa. [Effects of the Invention]

[0025] The method for producing a solid electrolyte membrane according to the present invention includes a fibrous binder formed by the fibrousization of the binder during a dry process carried out without the use of a solvent, in a structure in which the binder is intertwined with each other. Therefore, even when only a small amount of the fibrous binder is used, it is possible to exhibit excellent tensile strength.

[0026] Furthermore, the strength of the solid electrolyte membrane can be improved by controlling the temperature, orientation, and loops in the calendering process after the physical mixing of the solid electrolyte particles and the binder to adjust the degree of fibrous formation of the binder and the internal structure formed by the fibrous binder. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic diagram showing the internal structure of a solid electrolyte membrane according to one embodiment of the present invention. [Figure 2a] These are scanning electron microscope images of a solid electrolyte membrane at different temperatures during the calendering process. [Figure 2b] This is a scanning electron microscope image of a solid electrolyte membrane oriented during the calendering process. [Figure 2c] This is a scanning electron microscope image of a solid electrolyte membrane obtained through a calendering loop. [Figure 3a] This graph shows the correlation between temperature and tensile strength in the calendering process. [Figure 3b] This graph shows the correlation between orientation and tensile strength in the calendering process. [Figure 3c] This graph shows the correlation between the loops in the calendering process and the ionic conductivity and tensile strength of the solid electrolyte membrane. [Modes for carrying out the invention]

[0028] The present invention will be described in more detail below to aid in understanding the invention.

[0029] As used herein, the term "three-dimensional network structure" refers to a structure formed by the intertwining of fibrous binders dispersed in a solid electrolyte membrane, and may include a frame made of fibrous binders and an internal space formed by the frame.

[0030] Method for manufacturing solid electrolyte membranes This invention relates to a method for producing a solid electrolyte membrane.

[0031] The present invention relates to a method for producing a solid electrolyte membrane, comprising the steps of (S1) mixing solid electrolyte particles and a binder; and (S2) applying the mixture obtained in step (S1) to a calendaring step to form a membrane, wherein the binder is fibrousized in the calendaring step.

[0032] In this context, the "calendering process" refers to the process of forming a film using two rollers.

[0033] In one embodiment of the present invention, step (S1) may involve physically mixing the solid electrolyte particles and the binder in a dry process that does not use a solvent.

[0034] Furthermore, since the solid electrolyte particles and the binder are physically mixed without any separate chemical reaction, the mixing can be described as physical mixing. The mixing may be carried out using a mortar and pestle, a ball mill, or a roll press.

[0035] Furthermore, during the physical mixing process, the binder may be fibrousized. The fibrous binder can be called a fibrous binder, and the fibrous binder may form a dispersed, intertwined three-dimensional network structure.

[0036] Figure 1 is a schematic diagram showing the internal structure of a solid electrolyte membrane according to one embodiment of the present invention.

[0037] Referring to Figure 1, within the solid electrolyte membrane (1), the solid electrolyte (10) may exist in a particulate state, and the fibrous binder (2) may be contained in an intertwined state. Specifically, the fibrous binder (2) may form a dispersed and intertwined three-dimensional network structure. The three-dimensional network structure includes frames made of the fibrous binder (2) and voids which are spaces between the frames, and solid electrolyte (10) particles may be located in the voids. The solid electrolyte (10) may be a sulfide-based and / or halide-based solid electrolyte.

[0038] In one embodiment of the present invention, the temperature of the calendering step may be 50°C to 200°C. 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, 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 rises, or degradation of the electrolyte or binder material may occur.

[0039] In one embodiment of the present invention, the calendering process may be performed for between 5 and 50 loops. Specifically, the number of loops may be 5 or more, 8 or more, 10 or more, or 12 or more, and may be 20 or less, 30 or less, 40 or less, or 50 or less. If the number of loops is less than 5, less binder fiberization may occur, reducing the strength of the solid electrolyte membrane. If the number of loops exceeds 50, the strength of the solid electrolyte membrane may not increase further even if the number of loops increases, or its uniformity may worsen.

[0040] In one embodiment of the present invention, the orientation of the calendering process may be uniaxial or biaxial. Uniaxial means that calendering is performed in one direction, and biaxial means that after calendering is performed in one direction, it is then performed alternately in the vertical direction on the horizontal plane of the electrolyte membrane.

[0041] When the calendering process is performed uniaxially, the fibrous formation of the binder will have directionality. On the other hand, when the calendering process is performed biaxially, the fibrous formation of the binder will have multiple directions equally distributed, resulting in less difference in strength depending on the direction.

[0042] In one embodiment of the present invention, the pressure applied to the mixture to form a film in the calendering step may be 1 kgf / cm to 50 kgf / cm. Specifically, the pressure may be 1 kgf / cm or more, 2 kgf / cm or more, 3 kgf / cm or more, 4 kgf / cm or more, 5 kgf / cm or more, 6 kgf / cm or more, 7 kgf / cm or more, 8 kgf / cm or more, 9 kgf / cm or more, or 10 kgf / cm or more, and may be 50 kgf / cm or less, 45 kgf / cm or less, 40 kgf / cm or less, 35 kgf / cm or less, 30 kgf / cm or less, 25 kgf / cm or less, or 20 kgf / cm or less. If the pressure is less than 1 kgf / cm, the degree of fiberization of the binder will be low, requiring an increase in the number of loops in the calendering step, and if it exceeds 50 kgf / cm, the uniformity of the formed film may decrease. In this case, the pressure may be linear pressure.

[0043] In one embodiment of the present invention, the solid electrolyte membrane is composed of a solid electrolyte and a fibrous binder, and the solid electrolyte includes one or more selected from the group consisting of sulfide-based solid electrolytes and halide-based solid electrolytes.

[0044] In one embodiment of the present invention, the interface between the solid electrolyte particles and the fibrous binder may be bonded.

[0045] Since the interface between the solid electrolyte particles and the fibrous binder is firmly bonded by pressure during the manufacturing process, even if a small amount of the fibrous binder is used, it is possible to prevent a decrease in the strength of the solid electrolyte membrane. Furthermore, since adhesion also occurs between the solid electrolytes, this may be even more advantageous in improving the strength of the solid electrolyte membrane.

[0046] 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, 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).

[0047] In one embodiment of the present invention, the tensile strength of the solid electrolyte membrane may be 45 kPa to 1000 kPa. It 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.

[0048] In one embodiment of the present invention, the solid electrolyte membrane may be solvent-free.

[0049] The solid electrolyte membrane is manufactured by a dry process in which the sulfide-based and / or halide-based solid electrolyte and binder are physically mixed, and therefore contains no solvent whatsoever. Furthermore, during the dry process, the binder is fibrousized by pressurization, and the fibrous binder disperses and intertwines with each other, forming a three-dimensional network structure. As a result, even when using only a small amount of the binder, a solid electrolyte membrane with improved strength due to the structure formed by the fibrous binder can be manufactured.

[0050] 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, resulting in a decrease in ionic conductivity.

[0051] Generally, the wet process carried out for the manufacture of solid electrolyte membranes involves using a solvent capable of dissolving the binder so that it is positioned between the solid electrolyte particles and provides adhesion.

[0052] On the other hand, the dry process according to the present invention does not use a solvent and physically stretches the initial particulate binder 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 be improved compared to a solid electrolyte membrane manufactured by the wet process. As mentioned above, the initial particulate binder undergoes physical deformation due to shear force at the stage of mixing with electrolyte particles. To induce such physical deformation, a mortar and pestle, ball mill, or roll press may be introduced during mixing. Furthermore, as a binder that readily undergoes physical deformation, a binder that is physically very weak and relatively easily forms fibers, such as PTFE, can be used.

[0053] In one embodiment of the present invention, the solid electrolyte may include a sulfide-based solid electrolyte and / or a halide-based solid electrolyte.

[0054] Furthermore, the solid electrolyte may be present in an amount of 98% by weight or more based on the total weight of the solid electrolyte membrane. Specifically, the content of the solid electrolyte may be 98% by weight or more, 98.5% by weight or more, or 99% by weight or more. If the content of the solid electrolyte is less than 98% by weight, the ionic conductivity of the solid electrolyte membrane may decrease. Also, there is no particular upper limit to the content of the solid electrolyte, but for example, it may be 99.8% by weight or less, and if it exceeds 99.8% by weight, the binder content will decrease relatively, and the tensile strength may decrease somewhat.

[0055] Furthermore, the solid electrolyte may be particulate, and its particle size (D50) may be between 10 nm and 10 μm. Specifically, it may be 10 nm or more, 100 nm or more, 1 μm or more, 2 μm or more, or 3 μm or more, and may be 5 μm or less, 7 μm or less, 9 μm or less, or 10 μm or less. If the particle size (D50) of the solid electrolyte is less than 10 nm, the tensile strength may decrease, and if it exceeds 10 μm, the surface of the solid electrolyte film may not be uniform, which may increase the resistance with the electrode.

[0056] In one embodiment of the present invention, 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.

[0057] In one embodiment of the present invention, the sulfide-based solid electrolyte may include a compound represented by the following chemical formula 1 or a mixture thereof: [Chemical formula 1] Li a M b S c X d In the above formula 1, M is selected from P, Sn, Sb, As, and Ge; The aforementioned X is selected from Cl, Br, and I. 5 ≤ a ≤ 7.5, and 0.5 <b≦1.5であり、4<c≦6であり、0.5<d≦2である。

[0058] In one embodiment of the present invention, the sulfide-based solid electrolyte may contain Li6PS5Cl.

[0059] In one embodiment of the present invention, the halide-based solid electrolyte may be represented by the following chemical formula 2: [Chemical formula 2] Li 6-3a M a Br bCl c In Formula 2, M is a metal other than Li, 0 < a < 2, 0 ≤ b ≤ 6, 0 ≤ c ≤ 6, and b + c = 6. In some embodiments, M may be a metal other than Li. Preferably, M can be selected from Sc, Y, B, Al, Ga, and In, 0 < a < 2, 0 ≤ b ≤ 6, 0 ≤ c ≤ 6, and b + c = 6 may also be satisfied.

[0060] For example, the halide solid electrolyte may contain one or more selected from the group consisting of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0061] In one embodiment of the present invention, the binder fibrillates during a dry process in which it is physically mixed and pressed with the sulfide-based and / or halide-based solid electrolyte, and the fibrous binder may form a three-dimensional network structure in a dispersed and intertwined state with each other.

[0062] The binder may be one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same, but is not limited thereto. A binder having low ductility strength and easily stretching during the dry process and capable of fibrillating into a fibrous binder can be widely used.

[0063] Also, the binder may be contained at 2% by weight or less based on the total weight of the solid electrolyte membrane. Specifically, the content of the binder may be 2% by weight or less, 1.5 % by weight or less, or 1% by weight or less. If the content of the binder exceeds 2% by weight, the ionic conductivity of the solid electrolyte membrane may decrease. Also, the lower limit of the binder is not particularly limited, but for example, it may be 0.2% by weight or more. If it is less than 0.2% by weight, the tensile strength may decrease somewhat.

[0064] Furthermore, the aspect ratio of the fibrous binder may be between 15 and 500. Specifically, the aspect ratio may be 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 60 or more, 65 or more, 70 or more, 75 or more, 80 or more, 85 or more, 90 or more, 95 or more, or 100 or more, and may be 500 or less, 450 or less, 400 or less, 350 or less, 300 or less, 250 or less, or 200 or less. If the aspect ratio of the fibrous binder is less than 15, it is difficult to form a three-dimensional network structure with the fibrous binder, and the strength of the solid electrolyte membrane decreases, which may reduce uniformity when assembling the battery. If the aspect ratio of the fibrous binder exceeds 500, the process for manufacturing the fibrous binder having that aspect ratio becomes complicated, which may reduce uniformity.

[0065] All solid state battery The present invention also relates to an all-solid-state battery comprising the solid electrolyte membrane.

[0066] 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.

[0067] In one embodiment of the present invention, the positive electrode may include a positive electrode active material, a conductive material, and a binder.

[0068] 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 surface of the positive electrode current collector.

[0069] The positive electrode active material layer comprises a positive electrode active material, a conductive material, and a binder.

[0070] 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[Nix Co y Mn z M v O2(In the above formula, M is any one element selected from the group consisting of Al, Ga, and In or two or more of these elements; 0.3 ≦ x < 1.0, 0 ≦ y, z ≦ 0.5, 0 ≦ v ≦ 0.1, and x + y + z + v = 1), Li(Li a M b-a-b’ M’ b’ )O 2-c A c (In the above formula, 0 ≦ a ≦ 0.2, 0.6 ≦ b ≦ 1, 0 ≦ b’ ≦ 0.2, 0 ≦ c ≦ 0.2; M contains one or more selected from the group consisting of Mn and 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), etc., layered compounds or compounds replaced by one or more transition metals; chemical formula Li 1+y Mn 2-y O4(where y is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; Ni-site type lithium nickel oxides represented by the chemical formula LiNi 1-y MyO2(where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); lithium manganese composite oxides represented by the chemical formula LiMn 2-y M y 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 replaced by alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., but not limited to these. [[ID={29}]]

[0071] 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 performance of the battery may deteriorate, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0072] 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 cause chemical changes in the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon can 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, lamp black, and summer 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 whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which can be used alone or in mixtures of two or more, but are not necessarily limited to these. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0073] The conductive material is usually included in an amount of 1% to 5% by weight based on 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, the effect of improving electrical conductivity may not be expected, or the electrochemical properties of the battery may deteriorate. If it is too high, exceeding 5% by weight, the amount of positive electrode active material may be relatively small, and the capacity and energy density may decrease. The method of incorporating the conductive material into the positive electrode is not greatly limited, and conventional methods known in the art, such as mixing with the positive electrode active material or coating, can be used.

[0074] 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, polypichlorohydrin, polyphosphazene, and polyacrylo It may contain one or more selected from the group consisting of nitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethyl scrophulari, 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).

[0075] 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 amount of positive electrode active material will decrease accordingly, which may reduce the battery capacity.

[0076] 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.

[0077] The positive electrode current collector is not particularly limited as long as it does not cause 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 alloys can be used as the positive electrode current collector.

[0078] The positive electrode current collector may have a fine uneven surface or employ 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 may take various forms, such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0079] 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 selectively compress-molded onto the current collector to 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 that evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

[0080] 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 surface of the negative electrode current collector.

[0081] 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.

[0082] The aforementioned lithium ion (Li + The material that can reversibly insert or remove the lithium ion (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The substance that can reversibly form a lithium-containing compound by reacting with ) may be, for example, tin oxide, titanium nitride, or silicon. 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).

[0083] Preferably, the negative electrode active material may be lithium metal or lithium-indium alloy (Li-In), and more specifically, it may be lithium metal, a lithium thin film, a lithium-indium alloy thin film, or a powder.

[0084] 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.

[0085] Furthermore, the binder is as described in the positive electrode active material layer.

[0086] Furthermore, the conductive material is as described in the positive electrode active material layer.

[0087] Furthermore, the negative electrode current collector is not particularly limited as long as it does not cause 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, or nonwoven fabrics with fine irregularities formed on their surface.

[0088] 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.

[0089] Manufacturing method for all-solid-state batteries The present invention also relates to a method for manufacturing an all-solid-state battery.

[0090] The method for manufacturing an all-solid-state battery according to the present invention includes the steps of: (P1) placing 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 the one surface of the solid electrolyte membrane; and (P2) placing a negative electrode on the other surface of the solid electrolyte membrane and applying pressure.

[0091] In step (P1), a mixture for forming a positive electrode active material layer is placed on one surface of the solid electrolyte membrane, and a positive electrode can be formed on that surface by applying high temperature and pressure.

[0092] 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, after forming the positive electrode active material layer, a current collector can be attached to produce the positive electrode.

[0093] Furthermore, the pressurization step is performed to bond the solid electrolyte membrane and the positive electrode while reducing interfacial resistance, and may be carried out 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, 460 MPa or lower, or 470 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 able to integrate, and if it exceeds the above range, the solid electrolyte membrane or the positive electrode may be deformed or damaged.

[0094] In the (P2) stage, an all-solid-state battery can be manufactured by placing a negative electrode on the other side of the solid electrolyte membrane and applying pressure. The description of the negative electrode is the same as described above.

[0095] 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.

[0096] Because all-solid-state batteries manufactured in this way contain a thin solid electrolyte, the manufacturing cost can be reduced, and ionic conductivity and energy density may be improved.

[0097] Furthermore, since the solid electrolyte membrane and the positive electrode are integrated through a high-temperature and high-pressure process, interfacial stability may be improved.

[0098] 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.

[0099] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by battery-powered 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.

[0100] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications naturally fall within the scope of the attached claims.

[0101] In the following examples and comparative examples, solid electrolytes and all-solid-state batteries were manufactured according to the compositions and processes described in Table 1 below.

[0102] [Table 1]

[0103] Example 1 A solid electrolyte film with a thickness of 300 μm was produced by mixing Li6PS5Cl powder, a sulfide-based solid electrolyte, with PTFE particles (polytetrafluoroethylene, Chemours) as a binder in a mortar and pestle, and then performing 15 calendaring loops in a roll press at a temperature of 90°C and under biaxial orientation conditions. The above manufacturing process was carried out dryly without the use of solvents.

[0104] Example 2 The procedure was carried out in the same manner as in Example 1, except that the temperature was set to 23°C.

[0105] Example 3 The procedure was carried out in the same manner as in Example 1, except that the temperature was set to 60°C.

[0106] Example 4 The procedure was carried out in the same manner as in Example 1, except that the temperature was set to 120°C.

[0107] Example 5 The procedure was carried out in the same manner as in Example 1, except that the orientation condition for the calendering process was set to uniaxial orientation.

[0108] Example 6 The procedure was carried out in the same manner as in Example 1, except that the aforementioned color rendering loop was performed twice.

[0109] Example 7 The procedure was carried out in the same manner as in Example 1, except that the aforementioned color rendering loop was performed five times.

[0110] Example 8 The procedure was carried out in the same manner as in Example 1, except that the aforementioned color rendering loop was performed 10 times.

[0111] Example 9 The procedure was carried out in the same manner as in Example 1, except that the aforementioned color rendering loop was performed 30 times.

[0112] Experimental Example 1: Internal Structure of a Solid Electrolyte Membrane An experiment was conducted to confirm the internal structure of the solid electrolyte membrane produced in the example.

[0113] Figure 2a shows scanning electron microscope (SEM, FEI Apreo SEM) images of the solid electrolyte membrane at different temperatures during the calendering process.

[0114] Referring to Figure 2a, it was confirmed that the solid electrolyte membrane of Example 2, which had the lowest temperature among Examples 1 to 4, did not have a dense structure in which the fibrous binders were intertwined. From this, it can be seen that if the temperature of the calendering process is too low, the strength of the solid electrolyte membrane will be low.

[0115] Figure 2b is a scanning electron microscope (SEM, FEI Apreo SEM) image of the solid electrolyte membrane oriented during the calendering process.

[0116] Referring to Figure 2b, it can be seen that in Example 1, where the orientation during the calendering process is biaxial, the three-dimensional network structure formed by the entanglement of fibrous binders is even denser compared to Example 5, where the orientation during the calendering process is uniaxial. From this, it can be seen that the strength of the solid electrolyte membrane is further improved when the calendering process is carried out with biaxial orientation.

[0117] Figure 2c is a scanning electron microscope (SEM, FEI Apreo SEM) image of the solid electrolyte membrane during the calendering process loop.

[0118] Referring to Figure 2c, it can be seen that as the number of loops in the calendering process increases, the three-dimensional network structure formed by the entanglement of fibrous binders becomes even denser. From this, it can be seen that the strength of the solid electrolyte membrane improves as the number of times the calendering process loops are repeated increases.

[0119] Experimental Example 2: Measurement of Ionic Conductivity and Tensile Strength of Solid Electrolyte Membranes To confirm the physical properties of the solid electrolyte membrane produced in the examples, experiments were conducted to measure ionic conductivity and tensile strength. The methods for measuring ionic conductivity and tensile strength are as follows.

[0120] (1) Measurement of ionic conductivity 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 the blocking electrode to measure the ionic conductivity.

[0121] Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C under conditions of 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.

[0122] [Formula 1]

number

[0123] (2) Measurement of tensile strength The solid electrolyte membrane was cut into 10mm x 50mm pieces. To minimize damage to the solid electrolyte membrane due to forceps contact during measurement, tape was attached to both ends of the sample, and then the tensile strength was measured using a UTM (Universal Testing Machine, MARK-10, M5-05) device.

[0124] Figure 3a is a graph showing the correlation between temperature and tensile strength in the calendering process.

[0125] Referring to Figure 3a, it can be seen that the tensile strength of the solid electrolyte membrane increases as the temperature of the calendering process increases.

[0126] Figure 3b is a graph showing the correlation between the orientation of the calendering process and the tensile strength. In Example 5, where the calendering process was performed uniaxially, the tensile strength was measured in the horizontal (Uniaxial |) and vertical (Uniaxial ┻) directions relative to the orientation of the calendering process.

[0127] Referring to Figure 3b, when the orientation of the calendering process was biaxial or uniaxial, the tensile strength was similar, or the tensile strength increased slightly in the biaxial case as the calendering loop increased. However, when the orientation of the calendering process was uniaxial, the tensile strength measured in the direction perpendicular to the orientation (uniaxial ┻) was significantly lower than that measured in the biaxial or uniaxial case horizontally to the orientation of the calendering process, and the tensile strength hardly increased even as the calendering loop increased. From this, it was found that when the orientation of the calendering process is uniaxial, the tensile strength has directionality.

[0128] Figure 3c is a graph showing the correlation between the loop in the calendering process and the ionic conductivity and tensile strength of the solid electrolyte membrane.

[0129] Referring to Figure 3c, it was confirmed that even when the number of loops in the calendering process increased, there was no significant change in the ionic conductivity of the solid electrolyte membrane, but the tensile strength increased.

[0130] This indicates that, when manufacturing solid electrolyte membranes, the temperature, orientation, and loops of the calendering process affect the fiberization of the binder and the structure formed by the fiberized binder, and that these are closely related to the tensile strength of the solid electrolyte membrane.

[0131] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations can be made by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described below. [Explanation of Symbols]

[0132] 1: Solid electrolyte membrane 10: (Sulfide-based and / or halide-based) solid electrolytes 20: Fibrous binder

Claims

1. (S1) A step of mixing solid electrolyte particles and a binder; (S2) The step of applying the mixture obtained in step (S1) to a calendering process to form a film; A method for producing a solid electrolyte membrane, wherein the binder is fibrously formed by the mixing described above.

2. The method for producing a solid electrolyte membrane according to claim 1, wherein the temperature of the calendering step is 50°C to 200°C.

3. The method for producing a solid electrolyte membrane according to claim 1, wherein the calendering step is performed for 5 to 50 loops.

4. The method for producing a solid electrolyte membrane according to claim 1, wherein the calendering step is performed uniaxially or biaxially.

5. The method for producing a solid electrolyte membrane according to claim 1, wherein steps (S1) and (S2) are performed in a solvent-free manner.

6. The method for producing a solid electrolyte membrane according to claim 1, wherein the solid electrolyte particles include one or more selected from the group consisting of sulfide-based solid electrolyte particles and halide-based solid electrolyte particles.

7. The method for producing a solid electrolyte membrane according to any one of claims 1 to 6, wherein the solid electrolyte membrane comprises solid electrolyte particles and a fibrous binder.

8. The method for producing a solid electrolyte membrane according to claim 7, wherein the fibrous binder comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same.

9. The method for producing a solid electrolyte membrane according to claim 7, wherein the fibrous binder is included in an amount of 2% by weight or less based on the total weight of the solid electrolyte membrane.

10. The method for producing a solid electrolyte membrane according to claim 7, wherein the fibrous binder is contained in the solid electrolyte membrane in a dispersed state.

11. The method for producing a solid electrolyte membrane according to claim 7, wherein the interface between the solid electrolyte particles and the fibrous binder is bonded.

12. The method for producing a solid electrolyte membrane according to claim 7, wherein the ionic conductivity of the solid electrolyte membrane is 0.5 mS / cm to 10 mS / cm.

13. The method for manufacturing a solid electrolyte membrane according to claim 7, wherein the tensile strength of the solid electrolyte membrane is 45 kPa to 1000 kPa.

14. A solid electrolyte membrane manufactured by the method of claim 1.

15. All-solid-state battery comprising a solid electrolyte membrane according to claim 14.

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