Method for manufacturing solid electrolyte membrane

Abstract

The present invention relates to a method for manufacturing a solid electrolyte membrane. More specifically, a solid electrolyte membrane can be manufactured by fiberizing a small amount of binders through dry calendering. Since the fiberized binders are included in the solid electrolyte membrane while entangled with each other, both excellent ion conductivity and strength characteristics are exhibited.

Description

Method for manufacturing a solid electrolyte membrane

[0001] This application claims the benefit of priority to U.S. Patent Application No. 18 / 234,286, filed Aug. 15, 2023, Korean Patent Application No. 10-2023-0124429, filed Sep. 19, 2023, and Korean Patent Application No. 10-2024-0108292, filed Aug. 13, 2024, the entire contents of which are 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.

[0003] Lithium secondary batteries have limitations in terms of capacity, safety, output, size, and miniaturization. Therefore, research is underway into various batteries that can overcome these limitations.

[0004] Representative examples include metal-air batteries with much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries with no risk of explosion in terms of safety, supercapacitors for output, NaS batteries or RFBs (redox flow batteries) for large-scale applications, and thin film batteries for miniaturization, all of which are being continuously researched in academia and industry.

[0005] All-solid-state batteries replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Consequently, they eliminate the use of flammable solvents, significantly improving safety by eliminating the risk of fire or explosion caused by decomposition reactions of conventional electrolytes. Furthermore, the ability to use lithium metal or lithium alloys as the anode material offers the advantage of dramatically improving the battery's energy density relative to its mass and volume.

[0006] However, while solid-state batteries can ensure safety by using the solid electrolyte, their ionic conductivity may be reduced. Furthermore, if a liquid electrolyte is used as a means to secure the ionic conductivity of the solid electrolyte, there is a problem of reduced strength.

[0007] In general, in order to ensure the safety of all-solid-state batteries while preventing degradation of battery performance and processability, both the ionic conductivity and strength of the solid electrolyte must be maintained above a certain level.

[0008] As the demand for all-solid-state batteries increases, the demand for solid electrolytes included in all-solid-state batteries also increases proportionally, and therefore, the development of a process capable of manufacturing solid electrolytes with both excellent ionic conductivity and strength is required.

[0009] [Prior Art Literature]

[0010] [Patent Document]

[0011] (Patent Document 1) Korean Patent Publication No. 2022-0095689

[0012] To address the above-described problems, the inventors of the present invention have conducted extensive research and have found that, when a solid electrolyte membrane is manufactured through a calendering process and the optimal temperature, orientation, and loop are controlled to produce a solid electrolyte membrane having excellent ionic conductivity and strength, the solid electrolyte membrane can be manufactured. The calendering process comprises physically mixing a sulfide-based solid electrolyte and / or a halide-based solid electrolyte with a binder, and then fiberizing the binder. The structure formed by the fiberized binder may vary depending on the temperature, orientation, and loop of the calendering process.

[0013] Accordingly, the purpose of the present invention is to provide a method for manufacturing a solid electrolyte membrane with improved ionic conductivity and strength.

[0014] To achieve the above object, the present invention provides a method for manufacturing 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 process to form the mixture into a membrane shape, wherein the binder is fiberized by the mixing.

[0015] 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.

[0016] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the calendaring process is performed for 5 to 50 loops.

[0017] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the calendaring process is performed uniaxially or biaxially.

[0018] 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.

[0019] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the solid electrolyte particles include at least one selected from the group consisting of sulfide-based solid electrolyte particles and halide-based solid electrolyte particles.

[0020] 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.

[0021] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the fibrous binder comprises at least one selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same.

[0022] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is included in an amount of 2 wt% or less based on the total weight of the solid electrolyte membrane.

[0023] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is included in a dispersed state in the solid electrolyte membrane.

[0024] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the interface between the solid electrolyte and the fibrous binder is bonded.

[0025] 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 to 10 S / cm.

[0026] The present invention also provides a method for manufacturing a solid electrolyte membrane, wherein the tensile strength of the solid electrolyte membrane is 45 to 1000 kPa.

[0027] The method for manufacturing a solid electrolyte membrane according to the present invention includes a structure in which fibrous binders formed by fiberization of a binder during a dry process performed without using a solvent are entangled with each other, so that even if only a small amount of the fibrous binder is used, excellent tensile strength can be exhibited.

[0028] In addition, by controlling the temperature, orientation, and loop in the calendaring process after the physical mixing of the solid electrolyte particles and the binder, the degree of fiberization of the binder and the internal structure formed by the fiberized binder can be controlled, thereby improving the strength of the solid electrolyte membrane.

[0029] Figure 1 is a schematic diagram showing the internal structure of a solid electrolyte membrane according to one embodiment of the present invention.

[0030] Figure 2a is a scanning electron microscope photograph of a solid electrolyte membrane according to the temperature of the calendaring process.

[0031] Figure 2b is a scanning electron microscope photograph of a solid electrolyte membrane according to the orientation of the calendaring process.

[0032] Figure 2c is a scanning electron microscope photograph of a solid electrolyte membrane along a loop of a calendaring process.

[0033] Figure 3a is a graph showing the correlation between temperature and tensile strength in the calendaring process.

[0034] Figure 3b is a graph showing the correlation between the orientation of the calendaring process and the tensile strength.

[0035] Figure 3c is a graph showing the correlation between the loop of the calendaring process and the ionic conductivity and tensile strength of the solid electrolyte membrane.

[0036] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0037] The term “three-dimensional network structure” used herein refers to a structure formed by entanglement of fibrous binders dispersed and included in a solid electrolyte membrane, and may be a structure including a frame made of the fibrous binder and an internal space formed by the frame.

[0038]

[0039] Method for manufacturing a solid electrolyte membrane

[0040] The present invention relates to a method for manufacturing a solid electrolyte membrane.

[0041] A method for manufacturing a solid electrolyte membrane according to the present invention comprises: (S1) a step of mixing solid electrolyte particles and a binder; and (S2) a step of applying the mixture obtained in step (S1) to a calendaring process to form the mixture into a membrane shape; wherein the binder is characterized in that it is fiberized in the calendaring process.

[0042] At this time, the calendaring process refers to a process of forming into a film shape using two rollers.

[0043]

[0044] In one embodiment of the present invention, the step (S1) may be a physical mixing process in which solid electrolyte particles and a binder are mixed using a dry process without using a solvent.

[0045] In addition, since the solid electrolyte particles and the binder are physically mixed without a separate chemical reaction, the mixing can be referred to as physical mixing. The mixing can be performed by a mortar (pestle bowl), ball mixing, or roll pressing.

[0046] Additionally, the binder may be fiberized during the physical mixing. The fiberized binder may be referred to as a fibrous binder, and the fibrous binder may be dispersed and form a three-dimensional network structure in which the fibrous binder is entangled with one another.

[0047]

[0048] Figure 1 is a schematic diagram showing the internal structure of a solid electrolyte membrane according to one embodiment of the present invention.

[0049] Referring to Fig. 1, the solid electrolyte (10) exists in a particle state inside the solid electrolyte membrane (1), and the fibrous binder (2) may be included in an entangled state. Specifically, the fibrous binder (2) may be dispersed and form a three-dimensional network structure in which the fibrous binder (2) is entangled with each other. The three-dimensional network structure includes a frame made of the fibrous binder (2) and a void, which is a space between the frames, and solid electrolyte (10) particles may be positioned in the void. The solid electrolyte (10) may be a sulfide-based and / or halide-based solid electrolyte.

[0050]

[0051] In one embodiment of the present invention, the temperature of the calendering process 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 lower than 50°C, less fiberization of the binder may occur, which may lower the strength of the solid electrolyte membrane, and if it exceeds 200°C, the strength of the solid electrolyte membrane may not increase any further even if the temperature increases, or the electrolyte or binder material may deteriorate.

[0052]

[0053] In one embodiment of the present invention, the calendaring process may be performed for 5 to 50 loops. Specifically, the number of loops may be 5 or more, 8 or more, 10 or more, or 12 or more, and 20 or less, 30 or less, 40 or less, or 50 or less. If the number of loops is less than 5, less fiberization of the binder may occur, which may lower the strength of the solid electrolyte membrane. If the number of loops is more than 50, even if the number of loops increases, the strength of the solid electrolyte membrane may not increase any further, or the processability may deteriorate.

[0054]

[0055] In one embodiment of the present invention, the orientation of the calendering process may be performed uniaxially or biaxially. Here, uniaxially means that calendering is performed in one direction, and biaxially means that calendering is performed in one direction and then alternately in a vertical direction toward the horizontal surface of the electrolyte membrane.

[0056] When the above-mentioned calendaring process is performed uniaxially, the fiberization of the binder becomes directional. On the other hand, when the above-mentioned calendaring process is performed biaxially, the fiberization of the binder becomes evenly directional, thereby reducing the difference in strength depending on the direction.

[0057]

[0058] In one embodiment of the present invention, the pressure applied to the mixture to form a film in the calendering process may be 1 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 may be lowered, so that the number of loops in the calendering process may need to be increased, and if it exceeds 50 kgf / cm, the uniformity of the film formed may be reduced. At this time, the above pressure may be linear pressure.

[0059]

[0060] 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 at least one selected from the group consisting of a sulfide-based solid electrolyte and a halide-based solid electrolyte.

[0061]

[0062] In one embodiment of the present invention, the interface between the solid electrolyte and the fibrous binder may be bonded.

[0063] Since the interface between the solid electrolyte and the fibrous binder is firmly bonded by pressure during the manufacturing process, even if a small amount of the fibrous binder is used, the strength of the solid electrolyte membrane can be prevented from deteriorating. Furthermore, since the solid electrolytes are bonded together, this can further enhance the strength of the solid electrolyte membrane.

[0064]

[0065] In one embodiment of the present invention, the ionic conductivity of the solid electrolyte membrane may be 0.5 to 10 S / cm. Specifically, the ionic conductivity may be 0.5 S / cm or more, 0.6 S / cm or more, 0.8 S / cm or more, 1 S / cm or more, 1.5 S / cm or more, or 2 S / cm or more, and may be 3 S / cm or less, 5 S / cm or less, 8 S / cm or less, or 10 S / cm or less. The ionic conductivity may be measured at room temperature (25°C).

[0066]

[0067] In one embodiment of the present invention, the tensile strength of the solid electrolyte membrane may be 45 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.

[0068]

[0069] In one embodiment of the present invention, the solid electrolyte membrane may be solvent-free.

[0070] The above solid electrolyte membrane is manufactured through a dry process that physically mixes the sulfide-based and / or halide-based solid electrolyte with a binder, and therefore does not contain any solvent. Furthermore, during the dry process, the binder is fiberized by pressure, and the fibrous binder is dispersed and entangled with one another, forming a three-dimensional network structure. Accordingly, even with a small amount of the binder, a solid electrolyte membrane with improved strength can be manufactured due to the structure formed by the fibrous binder.

[0071] In addition, since a separate solvent is not used, the phenomenon of the crystal structure of the sulfide-based and / or halide-based solid electrolyte being destroyed by the solvent and resulting in a decrease in ionic conductivity can be prevented.

[0072]

[0073] Typically, the wet process used to manufacture a solid electrolyte membrane uses a solvent capable of dissolving a binder, which is positioned between solid electrolyte particles to provide adhesive strength.

[0074] On the other hand, the dry process according to the present invention physically stretches the initial particle-shaped binder to fiberize it without using a solvent. Therefore, the structure of the binder in the manufactured solid electrolyte membrane is different from the structure formed by the wet process, and the physical properties of the solid electrolyte membrane or the solid electrolyte membrane manufactured by the wet process can be improved. In the above, the initial particle-shaped binder is physically deformed by shear force during the mixing step with the electrolyte particles. To induce this physical deformation, a tumbler, ball milling, or roll press can be introduced during the mixing process. In addition, a binder that can easily induce physical deformation, such as PTFE, which is physically very weak and thus relatively prone to fiberization, can be used.

[0075]

[0076] In one embodiment of the present invention, the solid electrolyte may include a sulfide-based solid electrolyte and / or a halide-based solid electrolyte.

[0077] In addition, the solid electrolyte may be included in an amount of 98 wt% or more based on the total weight of the solid electrolyte membrane. Specifically, the content of the solid electrolyte may be 98 wt% or more, 98.5 wt% or more, or 99 wt% or more. If the content of the solid electrolyte is less than 98 wt%, the ionic conductivity of the solid electrolyte membrane may be reduced. In addition, the upper limit of the solid electrolyte content is not particularly limited, but may be, for example, 99.8 wt% or less, and if it exceeds 99.8 wt%, the content of the binder is relatively reduced, so that the tensile strength may be somewhat reduced.

[0078] In addition, the solid electrolyte may be in the form of particles, and the particle size (D50) may be from 10 nm to 10 ㎛, specifically, may be 10 nm or more, 100 nm or more, 1 ㎛ or more, 2 ㎛ or more, or 3 ㎛ or more, and may be 5 ㎛ or less, 7 ㎛ or less, 9 ㎛ or less, or 10 ㎛ or less. If the particle size (D50) of the solid electrolyte is less than 10 nm, the tensile strength may be reduced, and if it exceeds 10 ㎛, the surface of the solid electrolyte membrane may not be uniform, which may increase the resistance with respect to the electrode.

[0079]

[0080] In one embodiment of the present invention, the sulfide-based solid electrolyte may include at least one 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 art can be used.

[0081] 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:

[0082] <Chemical Formula 1>

[0083] Li a M b S c X d

[0084] In the above chemical formula 1, M is selected from P, Sn, Sb, As, and Ge;

[0085] The above X is selected from Cl, Br and I,

[0086] 5 ≤ a ≤ 7.5, 0.5 < b ≤ 1.5, 4 < c ≤ 6, and 0.5 < d ≤ 2.

[0087] In one embodiment of the present invention, the sulfide-based solid electrolyte may include Li6PS5Cl.

[0088]

[0089] In one embodiment of the present invention, the halide-based solid electrolyte may be represented by the following chemical formula 2:

[0090] <Chemical Formula 2>

[0091] Li 6-3a M a Br b Cl c

[0092] In the above chemical formula 2, M is a metal other than Li, and a is 0 <a<2 이고, b는 0≤b≤6 이고, c는 0≤c≤6 이며, b+c=6 이다. 일부 실시예에서, M은 Li 이 외의 금속일 수 있다. 바람직하게는, M은 Sc, Y, B, Al, Ga 및 In 중 선택될 수 있고, 0<a<2 이고, 0≤b≤6 이고, 0≤c≤6 이며, b+c=6 일 수 있다.

[0093] For example, the halide solid electrolyte may include at least one selected from the group consisting of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0094]

[0095] In one embodiment of the present invention, the binder is fiberized during a dry process in which it is physically mixed and pressurized with the sulfide-based and / or halide-based solid electrolyte, and the fibrous binder is dispersed and entangled with each other to form a three-dimensional network structure.

[0096] The above binder may be at least one selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same, but is not limited thereto. A binder that has low ductility and thus easily stretches during the dry process and can be fiberized to become a fibrous binder may be widely used.

[0097] In addition, the binder may be included in an amount of 2 wt% or less based on the total weight of the solid electrolyte membrane. Specifically, the content of the binder may be 2 wt% or less, 1.5 wt% or less, or 1 wt% or less. If the content of the binder exceeds 2 wt%, the ionic conductivity of the solid electrolyte membrane may decrease. In addition, the lower limit of the binder is not particularly limited, but may be, for example, 0.2 wt% or more, and if it is less than 0.2 wt%, the tensile strength may be somewhat reduced.

[0098] In addition, the aspect ratio of the fibrous binder may be 15 to 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 by the fibrous binder, so that the strength of the solid electrolyte membrane is lowered, and thus the processability may be deteriorated during battery assembly. If the aspect ratio of the above fibrous binder exceeds 200, the process for manufacturing the fibrous binder having the aspect ratio may be complicated, resulting in poor processability.

[0099]

[0100] All-solid-state batteries

[0101] The present invention also relates to an all-solid-state battery including the solid electrolyte membrane.

[0102] An all-solid-state battery according to the present invention includes the solid electrolyte membrane; an anode formed on one surface of the solid electrolyte membrane; and an anode formed on the other surface of the solid electrolyte membrane.

[0103]

[0104] In one embodiment of the present invention, the positive electrode may include a positive electrode active material, a conductive material, and a binder.

[0105]

[0106] 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.

[0107] The above positive electrode active material layer includes a positive electrode active material, a conductive material, and a binder.

[0108]

[0109] In addition, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and examples thereof include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and Li[Ni x Co y Mn z M v ]O2 (wherein M is one or two 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 (In the above formula, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2; M includes at least one selected from the group consisting of Mn and Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M' is at least one selected from the group consisting of Al, Mg and B, and A is at least one selected from the group consisting of P, F, S and N.) layered compounds 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-y Ni-site type lithium nickel oxide represented by MyO2 (wherein, M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y is 0.01 to 0.3); chemical formula LiMn 2-y M yLithium manganese composite oxides represented by O2 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc., but are not limited thereto.

[0110] In addition, the positive electrode active material may be included in an amount of 60 to 80 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 60 wt% or more, 65 wt% or more, or 68 wt% or more, and may be 72 wt% or less, 75 wt% or less, or 80 wt% or less. If the content of the positive electrode active material is less than 60 wt%, battery performance may deteriorate, and if it is more than 80 wt%, mass transfer resistance may increase.

[0111]

[0112] In addition, 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. Representative examples thereof include graphite or conductive carbon, and examples thereof include graphite such as natural graphite and 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 having a crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powder 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 may be used alone or in combination of two or more thereof, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0113] The conductive material may typically be included in an amount of 1 wt% to 5 wt% based on the total weight of the positive electrode active material layer, and specifically, the content of the conductive material may be 1 wt% or more, 1.5 wt% or more, or 2 wt% or more, and 4 wt% or less, 4.5 wt% or less, or 5 wt% or less. If the content of the conductive material is too low, such as less than 1 wt%, it may be difficult to expect an effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 5 wt%, the amount of positive electrode active material may be relatively small, which may lower the capacity and energy density. The method of including the conductive material in the positive electrode is not particularly limited, and conventional methods known in the art, such as mixing or coating with the positive electrode active material, may be used.

[0114]

[0115] In addition, the binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, and includes styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate It may include at least one selected from the group consisting of 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 include polytetrafluoroethylene (PTFE).

[0116] In addition, the binder may be included in an amount of 0.5 wt% to 4 wt% based on the total weight of the positive electrode active material layer, and specifically, the content of the binder may be 0.5 wt% or more, 1 wt% or more, or 1.5 wt% or more, and 3 wt% or less, 3.5 wt% or less, or 4 wt% or less. If the content of the binder is less than 0.5 wt%, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced, and if it exceeds 4 wt%, the adhesive strength may be improved, but the content of the positive electrode active material may be reduced, which may lower the battery capacity.

[0117]

[0118] In addition, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

[0119] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, the positive electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., or an aluminum-cadmium alloy.

[0120] The above-mentioned positive electrode current collector may have a finely irregular structure on its surface or may employ a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or non-woven fabric.

[0121] The positive electrode as described above can be manufactured according to a conventional method, and specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive agent, and a binder in an organic solvent phase is applied and dried on a positive electrode current collector, and optionally, to improve electrode density, it can be manufactured by compression molding the positive electrode current collector. At this time, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive agent and is easily evaporated. Specifically, examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, and the like.

[0122]

[0123] 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 a negative electrode current collector.

[0124] The above negative active material is lithium (Li + ) can be reversibly intercalated or deintercalated, a material that can react with lithium ions to form a reversibly lithium-containing compound, or a lithium metal or a lithium alloy.

[0125] The above lithium ion (Li + ) can be reversibly inserted or de-inserted, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ion (Li +) can be, for example, tin oxide, titanium nitrate or silicon. The lithium alloy can 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).

[0126] Preferably, the negative active material may be lithium metal or a lithium-indium alloy (Li-In), and specifically, may be in the form of a lithium metal or a lithium thin film or a lithium-indium alloy thin film or powder.

[0127] The negative electrode active material may be included in an amount of 40 to 80 wt% based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt% or more or 50 wt% or more, and 70 wt% or less or 80 wt% or less. If the content of the negative electrode active material is less than 40 wt%, 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 wt%, the material transfer resistance may increase.

[0128] In addition, the binder is as described above in the positive electrode active material layer.

[0129] In addition, the above-described conductive material is as described above in the positive electrode active material layer.

[0130] In addition, the negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the negative electrode current collector, like the positive electrode current collector, may be made of various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. having fine irregularities formed on the surface.

[0131] The method for manufacturing the above negative electrode is not particularly limited, and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a method for forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, a case in which a battery is assembled on the negative electrode current collector without a lithium thin film and then a metallic lithium thin film is formed on the metal plate through initial charging is also included in the negative electrode of the present invention.

[0132]

[0133] Manufacturing method of all-solid-state battery

[0134] The present invention also relates to a method for manufacturing an all-solid-state battery.

[0135] A method for manufacturing an all-solid-state battery according to the present invention comprises 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 one surface of the solid electrolyte membrane; and (P2) positioning a negative electrode on the other surface of the solid electrolyte membrane and applying pressure.

[0136]

[0137] In the above step (P1), a mixture for forming a positive electrode active material layer is positioned on one side of a solid electrolyte membrane, and a positive electrode can be formed on one side of the solid electrolyte membrane by applying high temperature and pressure.

[0138] The mixture for forming the above-described positive electrode active material layer may include a positive electrode active material, a conductive agent, and a binder. The specific types and weights of these are as described above. In addition, after forming the positive electrode active material layer, a current collector may be attached to manufacture the positive electrode.

[0139] In addition, the pressurization process may be performed at a pressure of 300 MPa to 500 MPa to bond the solid electrolyte membrane and the anode while reducing the interface resistance. The pressure of the high-temperature pressurization process may be 300 MPa or more, 350 MPa or more, or 400 MPa or more, and may be 450 MPa or less, 460 MPa or less, or 470 MPa or less. If the temperature and / or pressure of the high-temperature pressurization process is below the above range, the solid electrolyte membrane and the anode may not be integrated, and if it exceeds the above range, the solid electrolyte membrane or the anode may be deformed or damaged.

[0140]

[0141] In the above step (P2), a cathode is positioned on the other side of the solid electrolyte membrane and pressurized to manufacture an all-solid-state battery. The description of the cathode is as described above.

[0142] The pressure during the pressurization may be 40 MPa to 80 MPa, and specifically, the pressure during the pressurization may be 40 MPa or more, 45 MPa or more, or 50 MPa or more, and 70 MPa or less, 75 MPa or less, or 80 MPa or less. If the pressure during the 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 the negative electrode may be deformed or damaged.

[0143]

[0144] The all-solid-state battery manufactured in this way includes a thin solid electrolyte, so that the manufacturing cost can be reduced and the ionic conductance and energy density can be improved.

[0145] In addition, since the solid electrolyte and the anode are integrated through a high-temperature pressurization process, interface stability can be improved.

[0146]

[0147] battery module

[0148] 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.

[0149] At this time, specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0150] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0151] 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.

[0152]

[0153] Solid electrolyte membrane calendering process Sulfide-based solid electrolyte Binder Temperature (℃) Orientation Loop Dry process Whether or not Material form Content (wt%) Example 1 Li6PS5ClPTFE Fiber 0.590 Biaxial 15 times Dry Example 2 Li6PS5ClPTFE Fiber 0.523 Biaxial 15 times Dry Example 3 Li6PS5ClPTFE Fiber 0.560 Biaxial 15 times Dry Example 4 Li6PS5ClPTFE Fiber 0.5120 Biaxial 15 times Dry Example 5 Li6PS5ClPTFE Fiber 0.590 Monoaxial 15 times Dry Example 6 Li6PS5ClPTFE Fiber 0.590 Biaxial 2 times Dry Example 7 Li6PS5ClPTFE Fiber 0.590 Biaxial 5 times Dry Example 8Li6PS5ClPTFE fiber 0.590 biaxial 10 times dry test example 9Li6PS5ClPTFE fiber 0.590 biaxial 30 times dry test

[0154]

[0155] Example 1

[0156] A mixture was obtained by mixing Li6PS5Cl powder, a sulfide-based solid electrolyte, with PTFE particles (polytetrafluoroethylene, Chemours), a binder, in a cauldron. The mixture was subjected to 15 calendaring loops using a roll press at 90°C and in a biaxial orientation, thereby producing a solid electrolyte membrane having a thickness of 300 μm. The manufacturing process was carried out dry without using a solvent.

[0157]

[0158] Example 2

[0159] The same procedure as Example 1 was followed, except that the temperature was set to 23°C.

[0160]

[0161] Example 3

[0162] The same procedure as Example 1 was followed, except that the temperature was set to 60°C.

[0163]

[0164] Example 4

[0165] The same procedure as Example 1 was followed, except that the temperature was set to 120°C.

[0166]

[0167] Example 5

[0168] The above calendaring process was performed in the same manner as Example 1, except that the orientation conditions were set to uniaxial orientation.

[0169]

[0170] Example 6

[0171] The same procedure as Example 1 was followed, except that the above calendaring loop was performed twice.

[0172]

[0173] Example 7

[0174] The same procedure as Example 1 was followed, except that the above calendaring loop was performed five times.

[0175]

[0176] Example 8

[0177] The same procedure as Example 1 was followed, except that the above calendaring loop was performed 10 times.

[0178]

[0179] Example 9

[0180] The same procedure as Example 1 was followed, except that the above calendaring loop was performed 30 times.

[0181]

[0182] Experimental Example 1: Internal Structure of a Solid Electrolyte Membrane

[0183] An experiment was conducted to confirm the internal structure of the solid electrolyte membrane manufactured in the example.

[0184]

[0185] Figure 2a is a scanning electron microscope (SEM, FEI Apreo SEM) photograph of a solid electrolyte membrane according to the temperature of the calendaring process.

[0186] Referring to Fig. 2a, it was confirmed that the solid electrolyte membrane of Example 2, which had the lowest temperature among Examples 1 to 4, had a structure in which the fibrous binders were intertwined with each other without a dense structure. From this, it can be seen that if the temperature of the calendaring process is excessively low, the strength of the solid electrolyte membrane will be low.

[0187]

[0188] Figure 2b is a scanning electron microscope (SEM, FEI Apreo SEM) image of a solid electrolyte membrane according to the orientation of the calendaring process.

[0189] Referring to Fig. 2b, it can be seen that the three-dimensional network structure formed by intertwining of fibrous binders in Example 1, which is biaxial, is more dense than that in Example 5, which is uniaxial during the calendaring process. From this, it can be seen that the strength of the solid electrolyte membrane will be further improved when the calendaring process is performed with a biaxial orientation.

[0190]

[0191] Figure 2c is a scanning electron microscope (SEM, FEI Apreo SEM) photograph of a solid electrolyte membrane along a loop of a calendaring process.

[0192] Referring to Figure 2c, it can be seen that as the loops of the calendering process increase in number, the three-dimensional network structure formed by the entanglement of the fibrous binders becomes denser. This suggests that the strength of the solid electrolyte membrane will further improve as the number of loop repetitions during the calendering process increases.

[0193]

[0194] Experimental Example 2: Measurement of ionic conductivity and tensile strength of a solid electrolyte membrane

[0195] To verify the properties of the solid electrolyte membrane manufactured in the examples, experiments were conducted to measure ionic conductivity and tensile strength. The measurement methods for ionic conductivity and tensile strength are as follows.

[0196]

[0197] (1) Ionic conductivity measurement

[0198] To measure the ionic conductivity of the solid electrolyte membrane, the solid electrolyte membrane was placed in a polyether ether ketone (PEEK) holder with a diameter of 10 mm, and the ionic conductivity was measured using a titanium rod as a blocking electrode.

[0199] The resistance was measured at 25°C using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) with an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, and the ionic conductivity of the solid electrolyte membrane was calculated using Equation 1 below.

[0200]

[0201] [Formula 1]

[0202]

[0203]

[0204] In the above equation 1, σi is the ionic conductivity (mS / cm) of the solid electrolyte membrane, R is the resistance (Ω) of the solid electrolyte membrane measured by the electrochemical impedance spectrometer, L is the thickness (㎛) of the solid electrolyte membrane, and A is the area (cm) of the solid electrolyte membrane. 2 ) means.

[0205]

[0206] (2) Tensile strength measurement

[0207] The solid electrolyte membrane was cut into 10 mm x 50 mm sizes. To minimize damage to the solid electrolyte membrane due to forceps bite during measurement, tape was attached to both ends of the sample, and the tensile strength was measured using a UTM (Universal Testing Machine, MARK-10, M5-05) device.

[0208]

[0209] Figure 3a is a graph showing the correlation between temperature and tensile strength in the calendaring process.

[0210] Referring to Fig. 3a, it can be confirmed that as the temperature of the calendaring process increases, the tensile strength of the solid electrolyte membrane also increases.

[0211]

[0212] Figure 3b is a graph showing the correlation between the orientation of the calendaring process and the tensile strength. In this case, for Example 5, in which the orientation of the calendaring process was uniaxial, the tensile strength was measured in the directions horizontal (Uniaxial |) and vertical (Uniaxial ┻) to the orientation of the calendaring process.

[0213] Referring to Fig. 3b, when the orientation of the calendering process is biaxial or uniaxial (|), the tensile strength is similar, or the tensile strength is slightly higher in the biaxial case as the number of calendering loops increases. However, when the orientation of the calendering process is uniaxial, the tensile strength measured in the direction perpendicular to the orientation (Uniaxial ┻) is significantly lower than the tensile strength measured in the direction perpendicular to the orientation of the biaxial or uniaxial (|) calendering process, and also, the tensile strength hardly increases even when the number of calendering loops increases. From this, it can be seen that the tensile strength has directionality when the orientation of the calendering process is uniaxial.

[0214]

[0215] Figure 3c is a graph showing the correlation between the loop of the calendaring process and the ionic conductivity and tensile strength of the solid electrolyte membrane.

[0216] Referring to Fig. 3c, it can be confirmed that the ionic conductivity of the solid electrolyte membrane does not change significantly even when the loop of the calendaring process increases, but the tensile strength increases.

[0217]

[0218] From this, it can be seen that the temperature, orientation, and loop of the calendaring process in the manufacture of a solid electrolyte membrane affect the fiberization of the binder and the structure formed by the fiberized binder, and thus are closely related to the tensile strength of the solid electrolyte membrane.

[0219]

[0220] 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 are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0221]

[0222] [Explanation of symbols]

[0223] 1: Solid electrolyte membrane

[0224] 10: (Sulphide and / or halide) solid electrolyte

[0225] 20: Fibrous binder

Claims

1. (S1) A step of mixing solid electrolyte particles and a binder; and (S2) a step of applying the mixture obtained in the step (S1) to a calendaring process to form it into a film shape; including, A method for producing a solid electrolyte membrane, wherein the binder is fiberized by the mixing.

2. In paragraph 1, A method for manufacturing a solid electrolyte membrane, wherein the temperature of the above calendaring process is 50°C to 200°C.

3. In paragraph 1, A method for manufacturing a solid electrolyte membrane, wherein the above calendaring process is performed for 5 to 50 loops.

4. In paragraph 1, A method for manufacturing a solid electrolyte membrane, wherein the above-mentioned calendaring process is performed uniaxially or biaxially.

5. In paragraph 1, A method for producing a solid electrolyte membrane, wherein the above steps (S1) and (S2) are performed in a solvent-free manner.

6. In paragraph 1, A method for producing a solid electrolyte membrane, wherein the solid electrolyte particles include at least one selected from the group consisting of sulfide-based solid electrolyte particles and halide-based solid electrolyte particles.

7. In paragraph 1, A method for manufacturing a solid electrolyte membrane, wherein the solid electrolyte membrane is composed of solid electrolyte particles and a fibrous binder.

8. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the fibrous binder comprises at least one selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same.

9. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is contained in an amount of 2 wt% or less based on the total weight of the solid electrolyte membrane.

10. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the fibrous binder is dispersed in the solid electrolyte membrane.

11. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the interface between the solid electrolyte and the fibrous binder is bonded.

12. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the ionic conductivity of the solid electrolyte membrane is 0.5 to 10 S / cm.

13. In paragraph 7, A method for manufacturing a solid electrolyte membrane, wherein the tensile strength of the solid electrolyte membrane is 45 to 1000 kPa.

14. A solid electrolyte membrane manufactured according to the method of paragraph 1.

15. An all-solid-state battery comprising the solid electrolyte membrane of clause 14.

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