Solid electrolyte membrane and all-solid-state rechargeable batteries

Abstract

The present invention relates to: a solid electrolyte membrane comprising a sulfide-based solid electrolyte, a binder, a first solvent, and a second solvent, wherein the first solvent is at least one selected from among butyl butyrate, isobutyl isobutyrate, tetrahydrofuran, and ethyl acetate, and the second solvent is at least one selected from among hexyl butyrate, benzyl butyrate, benzyl isobutyrate, isopentyl butyrate, and octyl acetate; and all-solid-state rechargeable batteries.

Description

Solid electrolyte membranes and all-solid-state secondary batteries

[0001] It relates to a solid electrolyte membrane and an all-solid-state secondary battery.

[0002] Lithium secondary batteries, which offer high energy density and portability, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is underway to utilize high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosion or fire in the event of collisions, penetration, or other problems. Therefore, all-solid-state secondary batteries, which utilize solid electrolytes instead of the electrolyte, have been proposed. All-solid-state secondary batteries are composed entirely of solid materials, eliminating the risk of electrolyte leakage and explosion, making them safer. Furthermore, they facilitate the production of thin batteries, allowing for a reduced anode thickness, improving high-speed charge / discharge performance and enabling high-voltage operation and high-energy density.

[0004] Sulfide-based solid electrolytes with high ionic conductivity are mainly used as solid electrolytes. Among them, argyrodite-type sulfide-based solid electrolytes have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It can exhibit high ionic conductivity approaching the S / cm range, and has the advantage of having soft mechanical properties, which can form close bonds between solid electrolytes and between the solid electrolyte and the positive active material. Accordingly, all-solid-state secondary batteries using argyrodite-type sulfide-based solid electrolytes can exhibit improved rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0005] By resolving the non-uniformity of binder distribution within a solid electrolyte membrane, the durability and high-rate characteristics of the solid electrolyte membrane and the all-solid-state secondary battery containing the same are improved.

[0006] In one embodiment, a solid electrolyte membrane is provided, which comprises a sulfide-based solid electrolyte, a binder, a first solvent, and a second solvent, wherein the first solvent is at least one selected from butyl butyrate, isobutyl isobutyrate, tetrahydrofuran, 2-methylbutyl butyrate, and ethyl acetate, and the second solvent is at least one selected from hexyl butyrate, benzyl butyrate, benzyl isobutyrate, isopentyl butyrate, and octyl acetate.

[0007] In another embodiment, an all-solid-state secondary battery is provided, comprising a positive electrode, a negative electrode, and the aforementioned solid electrolyte membrane positioned between the positive electrode and the negative electrode.

[0008] According to one embodiment, a solid electrolyte membrane has a binder uniformly distributed inside or a larger amount of binder distributed on the surface in contact with the anode, thereby improving durability and improving electrochemical characteristics such as rate characteristics and life characteristics of an all-solid-state secondary battery.

[0009] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0010] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0011] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0012] Here, “combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0013] It should be understood that the terms "include," "comprising," or "having" herein are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0014] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0015] Also, here, “layer” includes not only the shape formed on the entire surface when observed in a plan view, but also the shape formed on a portion of the surface.

[0016] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope image or a scanning electron microscope image. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size can mean the diameter (D50) of particles in a particle size distribution that have a cumulative volume of 50% by volume. In addition, unless otherwise defined, the average particle size can be obtained by randomly measuring the sizes (diameters or major axis lengths) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D50) of particles in the particle size distribution that have a cumulative volume of 50% by volume as the average particle size.

[0017] Here, “or” is not interpreted in an exclusive sense, for example, “A or B” is interpreted to include A, B, A+B, etc.

[0018] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0019] solid electrolyte membrane

[0020] In one embodiment, a solid electrolyte membrane is provided, which comprises a sulfide-based solid electrolyte, a binder, a first solvent, and a second solvent, wherein the first solvent is at least one selected from butyl butyrate, isobutyl isobutyrate, tetrahydrofuran, 2-methylbutyl butyrate, and ethyl acetate, and the second solvent is at least one selected from hexyl butyrate, benzyl butyrate, benzyl isobutyrate, isopentyl butyrate, and octyl acetate.

[0021] A solid electrolyte membrane according to one embodiment is characterized by comprising two or more solvents. The solvents are used for purposes such as dispersing solid electrolyte particles during the process of manufacturing the solid electrolyte membrane, and although some of the solvents evaporate during the drying process during the manufacturing process, they can be said to remain in small amounts in the final solid electrolyte membrane.

[0022] The first solvent may be said to be a solvent having higher volatility, higher boiling point, higher vapor pressure, or higher binder solubility than the second solvent, and the second solvent may be said to be a solvent having lower volatility, lower boiling point, lower vapor pressure, or lower binder solubility than the first solvent.

[0023] A solid electrolyte membrane can be manufactured in the form of a self-supporting membrane by manufacturing a composition including a solid electrolyte, a solvent, a binder, etc., coating it on a release film, and then drying it, or it can be manufactured by directly coating the composition on an anode, and then drying it. Due to the fact that the solid electrolyte is in a solid particle state, unlike a liquid electrolyte, and is vulnerable to moisture, etc., the choice of solvent and binder is very limited, and the problem that the binder acts as a resistor for lithium ion movement is further highlighted, and furthermore, during the manufacturing process of the solid electrolyte membrane, the binder is not well dispersed but sinks to the bottom, so that in the final solid electrolyte membrane, the binder is distributed in a high concentration only on the lower surface, which reduces the adhesion to the positive electrode, lowers the durability, and lowers the high-rate characteristics of the battery.

[0024] In one embodiment, by using both the first solvent and the second solvent as solvents in the manufacture of the solid electrolyte membrane, when applied in the form of a membrane, the first solvent can volatilize first or move to the upper part of the membrane, thereby moving the binder from the bottom to the top, while the second solvent can help disperse the binder within the membrane without volatilizing in the meantime. As a result, in the manufactured solid electrolyte membrane, the binder can be evenly or uniformly distributed within the membrane without being concentrated at a high concentration at the bottom, or a higher concentration of binder can be distributed in the upper part or the surface in contact with the anode in the thickness direction of the solid electrolyte membrane, and for example, a concentration gradient can be exhibited in which the binder content gradually increases from the bottom to the top. Such a solid electrolyte membrane can have improved adhesion to not only the anode but also the cathode, increased durability, and improved high-rate characteristics and life characteristics of a battery.

[0025] For example, the boiling point of the first solvent may be less than 190°C, and the boiling point of the second solvent may be greater than or equal to 190°C. Specifically, the boiling point of the first solvent may be from 60°C to 180°C, or from 80°C to 170°C, and the boiling point of the second solvent may be from 200°C to 280°C, or from 200°C to 260°C. Here, the boiling point is a value under the condition of 760 mmHg, which is an atmospheric pressure.

[0026] For example, the vapor pressure of the first solvent may be 1.00 mmHg or more, and the vapor pressure of the second solvent may be less than 1.00 mmHg. Specifically, the vapor pressure of the first solvent may be 1.00 mmHg to 20 mmHg, or 1.20 mmHg to 10 mmHg, and the vapor pressure of the second solvent may be 0.001 mmHg to 0.90 mmHg, or 0.01 mmHg to 0.80 mmHg. Here, the vapor pressure is a value at a temperature condition of 25°C.

[0027] The first solvent may be included in an amount of 0.1 wt% or less based on 100 wt% of the solid electrolyte membrane, for example, 0.0001 wt% to 0.1 wt%, 0.0001 wt% to 0.05 wt%, 0.0001 wt% to 0.04 wt%, 0.0001 wt% to 0.03 wt%, 0.0001 wt% to 0.02 wt%, 0.0001 wt% to 0.01 wt%, 0.001 wt% to 0.01 wt%, 0.001 wt% to 0.005 wt%, or 0.005 wt% to 0.01 wt%.

[0028] The second solvent may be included in an amount of 0.1 wt% or less based on 100 wt% of the solid electrolyte membrane, for example, 0.0001 wt% to 0.1 wt%, 0.0001 wt% to 0.05 wt%, 0.0001 wt% to 0.04 wt%, 0.0001 wt% to 0.03 wt%, 0.0001 wt% to 0.02 wt%, 0.0001 wt% to 0.01 wt%, 0.001 wt% to 0.01 wt%, 0.001 wt% to 0.005 wt%, or 0.005 wt% to 0.01 wt%.

[0029] The weight ratio of the first solvent to the second solvent within the solid electrolyte membrane may be 10:90 to 95:5, for example, 40:60 to 95:5, 50:50 to 95:5, 60:40 to 95:5, or 70:30 to 90:10. When the weight ratio of the first solvent to the second solvent satisfies the above range, the processability may be improved and the dispersibility of the binder may be further enhanced.

[0030] The solid electrolyte membrane may contain other solvents in addition to the first solvent and the second solvent as needed, and may further contain solvents such as xylene, toluene, benzene, and hexane, for example.

[0031] bookbinder

[0032] Any binder can be applied without limitation as long as it can adhere solid electrolyte particles well without adversely affecting the solid electrolyte. For example, the binder is nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, and these. copolymers, or combinations thereof.

[0033] For example, the binder may be a rubber-based binder, and may be specifically nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, or a combination thereof.

[0034] The binder may be included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte membrane, for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. If the binder content is excessive, the ionic conductivity of the solid electrolyte membrane may be reduced, and if the binder content is too small, the adhesive strength may be reduced, which may lower durability and battery reliability.

[0035] As described above, the binder may be evenly or uniformly distributed within the solid electrolyte membrane. As another example, the binder may be distributed in a higher concentration on the surface in contact with the anode than on the surface in contact with the cathode within the solid electrolyte membrane. For example, the binder may exhibit a concentration gradient in which the binder concentration increases from the surface in contact with the cathode to the surface in contact with the anode within the solid electrolyte membrane. In this case, the adhesive strength with the cathode is improved, thereby enhancing durability and improving the high-rate characteristics of the battery.

[0036] solid electrolyte

[0037] The solid electrolyte may be an inorganic solid electrolyte such as a sulfide-based solid electrolyte or an oxide-based solid electrolyte.

[0038] In one embodiment, the solid electrolyte may be a sulfide-based solid electrolyte having excellent ion conductivity. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5--LiX (wherein X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0039] Such sulfide-based solid electrolytes can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0040] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0041] According to one embodiment, sulfide-based solid electrolyte particles can be manufactured through, for example, a first heat treatment in which sulfur-containing raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the first heat treatment result is mixed and calcined at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ionic conductivity and robustness can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0042] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfide-based solid electrolyte particles may have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and can further form a close interface between an electrode layer and a solid electrolyte layer. An all-solid-state secondary battery including the same can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0043] The argyrodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the chemical formula 11 below.

[0044] [Chemical Formula 11]

[0045] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0046] In the above chemical formula 11, 4≤a≤8, and M 1 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 2 is Na, K, or a combination thereof, 0≤c<0.5, and M 3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0047] For example, in chemical formula 1, a halide element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 1에 M 1 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 1에서 M 3 can be understood as an element substituted in place of P and 0 <e<1일 수 있다. 화학식 1에서 M 4 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 4 Go SO n If SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and can be, for example, SO4.

[0048] For example, in chemical formula 1, a+b+c+h=7, d+e=1, and f+g+h=6.

[0049] As a specific example, argyrodite-type sulfide-based solid electrolyte particles include Li3PS4 and Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or combinations thereof, but are not limited thereto.

[0050] An argyrodite-type sulfide-based solid electrolyte can be manufactured, for example, by mixing lithium sulfide and phosphorus sulfide, and optionally, lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the resultant of the first heat treatment again and calcining at 350°C to 800°C.

[0051] The average particle size (D50) of the sulfide-based solid electrolyte particles may be, for example, 0.1 ㎛ to 5.0 ㎛ or 0.1 ㎛ to 3.0 ㎛, and may be small particles of 0.1 ㎛ to 1.9 ㎛ or large particles of 2.0 ㎛ to 5.0 ㎛. The sulfide-based solid electrolyte particles may be a mixture of small particles having an average particle size of 0.1 ㎛ to 1.9 ㎛ and large particles having an average particle size of 2.0 ㎛ to 5.0 ㎛. The average particle size of the sulfide-based solid electrolyte particles may be measured from an electron microscope image, and for example, a particle size distribution may be obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, and D50 may be calculated from this.

[0052] The solid electrolyte may include an oxide-based inorganic solid electrolyte in addition to a sulfide-based material. The oxide-based inorganic solid electrolyte may include, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti yO3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0053] The solid electrolyte may include, for example, a halide-based solid electrolyte. The halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0054] The above halide-based solid electrolyte may contain a lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof, for example. The halide-based solid electrolyte may contain, for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte is, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0055] The solid electrolyte is in the form of particles and may have an average particle diameter (D50) of 5.0 μm or less, for example, 0.1 μm to 5.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.5 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.0 μm. This solid electrolyte can effectively penetrate between positive electrode active materials and has excellent contact with the positive electrode active material and connectivity between solid electrolyte particles.

[0056] Other ingredients

[0057] The solid electrolyte membrane may optionally further comprise an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0058] The above alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ion conductivity by enhancing the lithium ion mobility of the solid electrolyte layer.

[0059] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0060] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0061] Ionic liquids are salts or molten salts that are composed only of ions and are liquid at room temperature, with a melting point below room temperature.

[0062] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among:

[0063] The ionic liquid may be at least one selected from the group consisting of, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

[0064] In the above solid electrolyte layer, the weight ratio of the solid electrolyte and the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0065] All-solid-state secondary battery

[0066] In one embodiment, an all-solid-state secondary battery is provided, comprising a positive electrode, a negative electrode, and the aforementioned solid electrolyte membrane positioned between the positive electrode and the negative electrode.

[0067] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to FIG. 1, the all-solid-state secondary battery (100') may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a battery case. The all-solid-state secondary battery (100') may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although FIG. 1 illustrates one electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), an all-solid-state secondary battery may be manufactured by laminating two or more electrode assemblies.

[0068] cathode

[0069] An anode for an all-solid-state secondary battery comprises a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer comprises a negative electrode active material, may further comprise a binder and / or a conductive material, and may optionally comprise the solid electrolyte described above.

[0070] The above negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0071] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0072] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0073] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO. x (0 < x < 2), Si-Q alloy (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn-based negative electrode active materials include Sn, SnO2, Sn-R alloy (wherein R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may be mixed with SiO2 for use. The above elements Q and R may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0074] For example, the negative active material may include silicon-carbon composite particles. The average particle diameter (D50) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. The average particle diameter (D50) is measured by a particle size analyzer and refers to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. With respect to 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of 10 wt% to 60 wt% and carbon may be included in an amount of 40 wt% to 90 wt%. The silicon-carbon composite particles may include, for example, a core including silicon particles and a carbon coating layer positioned on a surface of the core. The average particle diameter (D50) of the silicon particles in the core may be, for example, 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (0 <x<2)로 표시될 수 있다. 또한, 상기 탄소 코팅층의 두께는 약 5 nm 내지 100 nm일 수 있다.

[0075] For example, the silicon-carbon composite particle may include a core including silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core and including amorphous carbon. For example, in the silicon-carbon composite particle, the amorphous carbon may not be present in the core but may be present only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (phenol resin, furan resin, polyimide resin, etc.). At this time, the content of the crystalline carbon may be 10 wt% to 70 wt%, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to 100 wt% of the silicon-carbon composite particle.

[0076] In the above silicon-carbon composite particle, the core may include a void in the central portion. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0077] The silicon-carbon composite particles described above can effectively suppress problems such as volume expansion, structural collapse, or particle crushing due to charge and discharge, thereby preventing the phenomenon of conductive path disconnection, realizing high capacity and high efficiency, and are advantageous for use under high voltage or fast charging conditions.

[0078] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. When the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0079] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0080] In one embodiment, the negative electrode active material layer further includes a binder and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. In addition, when the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0081] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be an insoluble binder, a water-soluble binder, or a combination thereof.

[0082] The above-mentioned non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0083] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0084] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity as a type of thickener may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0085] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0086] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0087] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0088] Fig. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. Referring to Fig. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state secondary battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405) or on the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged more than once, the precipitation-type negative electrode (400') may include, for example, a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The lithium metal layer (404) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0089] In this case, the aforementioned area or first solid electrolyte layer can be said to be a surface in contact with the cathode coating layer (405).

[0090] The above cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0091] The metal may be a lithium-philic metal, and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of several types of alloys. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, and may be, for example, 10 nm to 4 μm.

[0092] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0093] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0094] The above-described cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal may be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0095] The above cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0096] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0097] The above-described precipitated negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further flatten the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0098] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy.

[0099] The thickness of the lithium metal layer (404) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0100] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0101] anode

[0102] In one embodiment, the device comprises a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and a solid electrolyte, and may optionally comprise a binder and / or a conductive material. In this case, the positive electrode active material layer may comprise the aforementioned solid electrolyte.

[0103] positive electrode active material

[0104] The above-mentioned positive electrode active material may be applied without limitation as long as it is generally used in all-solid-state secondary batteries. For example, the above-mentioned positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, may include a lithium transition metal composite oxide, and may include a compound represented by any one of the following chemical formulas.

[0105] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0106] Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0107] Li a E 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0108] Li a E 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0109] Li a Ni 1-b-c Co b X c D α(0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 <α ≤ 2);

[0110] Li a Ni 1-b-c Co b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0111] Li a Ni 1-b-c Co b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0112] Li a Ni 1-b-c Mr b X c D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2);

[0113] Li a Ni 1-b-c Mr b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0114] Li a Ni 1-b-c Mr b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0115] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0116] The a Nor b Co c Mn d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0117] The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0118] The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0119] The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0120] The a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0121] The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0122] QO2; QS2; LiQS2;

[0123] V2O5; LiV2O5;

[0124] LiZO2;

[0125] LiNiVO4;

[0126] The (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0127] The (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0128] The a FePO4(0.90 ≤ a ≤ 1.8).

[0129] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0130] The above-mentioned positive electrode active material may be, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), or lithium iron phosphate (LFP).

[0131] The positive electrode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 11, a lithium cobalt-based oxide represented by the following chemical formula 12, a lithium iron phosphate-based compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 14, or a combination thereof.

[0132] [Chemical Formula 11]

[0133] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 Xb1

[0134] In the above chemical formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0135] In the above chemical formula 1, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0136] [Chemical Formula 12]

[0137] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0138] In the above chemical formula 12, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0139] [Chemical Formula 13]

[0140] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0141] In the above chemical formula 13, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0142] [Chemical Formula 14]

[0143] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0144] In the above chemical formula 14, 0.9≤a4≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0145] The average particle diameter (D50) of the positive electrode active material may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may include small particles having an average particle diameter (D50) of 1 μm to 9 μm and large particles having an average particle diameter (D50) of 10 μm to 25 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within a positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle diameter may be obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle diameters (diameter, major axis, or major axis length), obtaining a particle size distribution, and then taking the diameter (D50) of particles having a cumulative volume of 50% by volume from the particle size distribution as the average particle diameter.

[0146] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0147] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0148] The positive electrode active material may be included in an amount of 55 wt% to 99 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0149] bookbinder

[0150] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0151] The content of the binder in the positive electrode active material layer may be approximately 0.1 wt% to 5 wt% with respect to 100 wt% of the positive electrode active material layer.

[0152] Challenge

[0153] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any material that does not cause a chemical change and is electronically conductive in the battery to be constructed may be used. Examples of conductive materials that may be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0154] The content of the conductive material in the positive electrode active material layer may be 0 wt% to 3 wt%, 0.01 wt% to 2 wt%, or 0.1 wt% to 1 wt% with respect to 100 wt% of the positive electrode active material layer.

[0155] With respect to 100 wt% of the above positive electrode active material layer, the solid electrolyte may be included in an amount of 0.1 wt% to 35 wt%, for example, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%.

[0156] In addition, in the positive electrode active material layer, 65 wt% to 99 wt% of the positive electrode active material and 1 wt% to 35 wt% of the solid electrolyte may be included based on the total weight of the positive electrode active material and the solid electrolyte, for example, 80 wt% to 90 wt% of the positive electrode active material and 10 wt% to 20 wt% of the solid electrolyte may be included. When the solid electrolyte is included in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0157] Aluminum foil may be used as the positive electrode collector, but is not limited thereto.

[0158] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0159] The shape of the above-mentioned all-solid-state secondary battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state secondary battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, and for example, it can be used in electric bicycles or power tools, etc. In addition, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0160] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0161] Example 1

[0162] 1. Manufacturing of solid electrolyte membrane

[0163] A composition for a solid electrolyte membrane was prepared by mixing isobutyryl isobutyrate (IBIB) as a first solvent and hexyl butyrate as a second solvent in a weight ratio of 80:20, adding 2 wt% of an acrylic rubber binder and 98 wt% of a solid electrolyte (Li6PS5Cl, D50=3.5㎛) and mixing. The composition was applied onto a release PET film using a blade coater, pre-dried at about 110°C, and then dried at about 80°C under vacuum conditions to prepare a solid electrolyte membrane having a thickness of about 100 to 150㎛.

[0164] 2. Manufacturing of all-solid-state secondary batteries

[0165] An Ag / C composite was prepared by mixing carbon black having a primary particle size (D50) of approximately 30 nm and silver (Ag) having an average particle size (D50) of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the composite was added to 2 g of an NMP solution containing 7 wt% of polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer composition. This was applied to a nickel foil current collector using a bar coater and vacuum-dried, thereby preparing a deposition-type negative electrode in which a negative electrode coating layer was formed on the current collector.

[0166] LiNi coated with Li2O-ZrO2 0.8 Co 0.15 Mn 0.05 A positive electrode composition was prepared by mixing 85 wt% of O2 positive electrode active material, 13.5 wt% of solid electrolyte Li6PS5Cl, 1.0 wt% of polyvinylidene fluoride binder, and 0.5 wt% of carbon nanotube conductive material. The prepared positive electrode composition was coated on a positive electrode current collector using a bar coater, and dried and rolled to prepare a positive electrode.

[0167] A solid electrolyte film was laminated on a cathode, and an anode was laminated thereon to manufacture a unit cell. This was then placed in a laminate film and subjected to warm isostatic pressing (WIP) at 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0168] Comparative Example 1

[0169] An all-solid-state secondary battery was manufactured in substantially the same manner as in Example 1, except that only a second solvent was used in the manufacture of the solid electrolyte membrane.

[0170] Evaluation Example 1: Battery Rate Evaluation

[0171] For the all-solid-state secondary batteries of Example 1 and Comparative Example 1, a first cycle was performed by charging at 0.1 C and discharging at 0.1 C in a voltage range of 2.5 V to 4.25 V in a constant temperature chamber at 45°C, a second cycle was performed by charging at 0.1 C and discharging at 0.33 C, and a third cycle was performed by charging at 0.1 C and discharging at 1.0 C. The charge capacity and discharge capacity in each cycle were measured, and the ratio of the latter to the former was calculated as efficiency, which is shown in Table 1 below.

[0172] Charge capacity (mAh / g)Discharge capacity (mAh / g)Efficiency (%)Example 10.1C Charge / 0.1C discharge242.38207.4985.60.1C Charge / 0.33C discharge207.05191.6592.560.1C Charge / 1.0C discharge191.38174.391.07Comparative example 20.1C Charge / 0.1C discharge242.29205.6184.860.1C Charge / 0.33C discharge206.1190.8392.590.1C Charge / 1.0C discharge190.66167.1887.68

[0173] Referring to Table 1, it can be seen that in Example 1, where the first solvent and the second solvent were appropriately mixed and applied, the discharge capacity in the first to third cycles was higher and the charge / discharge efficiency in the third cycle was higher, thereby improving the high-rate characteristics, compared to Comparative Example 2, where only the second solvent was used.

[0174] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0175] [Explanation of symbols]

[0176] 100: All-solid-state battery 200: Cathode

[0177] 201: Cathode current collector 203: Cathode active material layer

[0178] 300: Solid electrolyte layer 400: Cathode

[0179] 401: Negative current collector 403: Negative active material layer

[0180] 400': Precipitation type cathode 404: Lithium metal layer

[0181] 405: Cathode coating layer 500: Elastic layer

Claims

1. A solid electrolyte membrane comprising a sulfide-based solid electrolyte, a binder, a first solvent, and a second solvent, The first solvent is at least one selected from butyl butyrate, isobutyl isobutyrate, tetrahydrofuran, 2-methylbutyl butyrate, and ethyl acetate, A solid electrolyte membrane wherein the second solvent is at least one selected from hexyl butyrate, benzyl butyrate, benzyl isobutyrate, isopentyl butyrate, and octyl acetate.

2. In paragraph 1, The boiling point of the first solvent is less than 190°C, A solid electrolyte membrane having a boiling point of the second solvent of 190°C or higher.

3. In paragraph 1, The boiling point of the first solvent is 60°C to 180°C, A solid electrolyte membrane having a boiling point of the second solvent of 200°C to 280°C.

4. In paragraph 1, The vapor pressure of the first solvent at 25°C is 1.00 mmHg or more, A solid electrolyte membrane having a vapor pressure of the second solvent at 25°C of less than 1.00 mmHg.

5. In paragraph 1, The vapor pressure of the first solvent at 25°C is 1.00 mmHg to 20 mmHg, A solid electrolyte membrane having a vapor pressure of the second solvent at 25°C of 0.001 mmHg to 0.90 mmHg.

6. In paragraph 1, A solid electrolyte membrane in which the first solvent is included in an amount of 0.1 wt% or less with respect to 100 wt% of the solid electrolyte membrane.

7. In paragraph 1, A solid electrolyte membrane in which the second solvent is included in an amount of 0.1 wt% or less with respect to 100 wt% of the solid electrolyte membrane.

8. In paragraph 1, A solid electrolyte membrane in which the weight ratio of the first solvent and the second solvent is 10:90 to 95:

5.

9. In paragraph 1, A solid electrolyte membrane in which the weight ratio of the first solvent and the second solvent is 70:30 to 90:

10.

10. In paragraph 1, The above binder is nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, copolymers thereof, or their A solid electrolyte membrane comprising a combination.

11. In paragraph 1, A solid electrolyte membrane in which the binder is included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte membrane.

12. In paragraph 1, The above binder is a solid electrolyte membrane that is uniformly distributed within the solid electrolyte membrane.

13. In paragraph 1, The above binder is a solid electrolyte membrane having a concentration gradient in the thickness direction of the solid electrolyte membrane.

14. In paragraph 1, A solid electrolyte membrane in which the above sulfide-based solid electrolyte is in the form of particles and the average particle diameter of the particles is 0.1 ㎛ to 5.0 ㎛.

15. In paragraph 1, The above sulfide-based solid electrolyte is a solid electrolyte membrane containing an argyrodite-type sulfide.

16. In paragraph 15, The above sulfide-based solid electrolyte particles are a solid electrolyte membrane comprising a compound represented by the following chemical formula 1: [Chemical Formula 1] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h In the above chemical formula 1, 4≤a≤8, M 1 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, M 2 is Na, K, or a combination thereof, and 0≤c<0.5, M 3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

17. Bipolar, cathode, and An all-solid-state secondary battery comprising a solid electrolyte membrane according to any one of claims 1 to 16 positioned between an anode and a cathode.

18. In paragraph 17, An all-solid-state secondary battery, wherein the binder content on the surface of the solid electrolyte membrane in contact with the positive electrode is greater than the binder content on the surface of the solid electrolyte membrane in contact with the negative electrode.

19. In paragraph 18, An all-solid-state secondary battery in which the binder content increases from the surface in contact with the cathode to the surface in contact with the anode within the above-mentioned solid electrolyte membrane.

20. In paragraph 17, The negative electrode comprises a current collector and a negative electrode coating layer positioned on the current collector and containing a lithium-philic metal, a carbon material, or a combination thereof, An all-solid-state secondary battery comprising a lithium metal layer formed by charging between the above-described current collector and the negative electrode coating layer.

Images