Positive electrode for all-solid-state rechargeable batteries, and all-solid-state rechargeable batteries

Abstract

The present invention relates to a positive electrode for all-solid-state rechargeable batteries, and all-solid-state rechargeable batteries, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer positioned on the positive electrode current collector, wherein: the positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a fluorine-based binder, a lithium salt, and a dispersion medium; the fluorine-based binder is a polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene (PVdF-HFP-TFE) copolymer; and the dispersion medium includes a compound represented by chemical formula 1 ([chemical formula 1] CH3C(=O)O-R1, R1 is a C7-C9 alkyl group).

Description

Cathode for all-solid-state secondary batteries and all-solid-state secondary batteries

[0001] The present invention relates to a positive electrode for an all-solid-state secondary battery and an all-solid-state secondary battery including the same.

[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 explosions or fires in the event of collisions, penetrations, or other problems. Therefore, all-solid-state secondary batteries, which utilize solid electrolytes instead of the electrolyte, are being proposed. All-solid-state secondary batteries are comprised entirely of solid materials, offering the advantage of safety by eliminating the risk of electrolyte leakage and explosion.

[0004] By lowering the resistance and increasing the lithium ion conductivity of the positive electrode for all-solid-state secondary batteries, the initial charge-discharge characteristics and cycle life of the battery are improved. Alternatively, by suppressing the agglomeration of the binder within the slurry during the manufacture of the positive electrode for all-solid-state secondary batteries and ensuring the phase stability of the slurry, the quality and productivity of the battery are improved.

[0005] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, comprising: a positive electrode current collector; and a positive electrode active material layer positioned on the positive electrode current collector; wherein the positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a fluorine-based binder, a lithium salt, and a dispersion medium, wherein the fluorine-based binder is a copolymer of polyvinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene (PVdF-HFP-TFE), and the dispersion medium includes a compound represented by the following chemical formula 1.

[0006] [Chemical Formula 1]

[0007] CH3C(=O)OR 1

[0008] In the above chemical formula 1, R 1 is an alkyl group of C7 to C9.

[0009] In another embodiment, an all-solid-state secondary battery is provided, comprising the above-described positive electrode; a negative electrode; and a solid electrolyte layer positioned between the positive electrode and the negative electrode.

[0010] According to one embodiment, a positive electrode for an all-solid-state secondary battery has high lithium ion conductivity and low resistance, and an all-solid-state secondary battery using the positive electrode has improved overall performance, including initial charge / discharge characteristics and lifespan characteristics. Alternatively, when manufacturing an all-solid-state secondary battery positive electrode according to one embodiment, the agglomeration phenomenon of a binder in a slurry is suppressed and the phase stability of the slurry is secured, thereby improving the quality and productivity of the all-solid-state secondary battery.

[0011] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0012] Figure 3 is a graph showing the initial charge / discharge characteristics of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Example 1, and is a graph showing the voltage according to the specific capacity.

[0013] Figure 4 is a graph showing the life characteristics of the all-solid-state secondary batteries of Examples 1 and 2 and Comparative Example 1.

[0014] Figure 5 is a graph showing the viscosity change in each case for the binder solution manufactured in Comparative Example 1: initially, after one day of high-temperature stirring, and after one month of standing.

[0015] Figure 6 is a graph showing the viscosity change in each case for the binder solution manufactured in Example 1, initially and after one month of storage.

[0016] Figure 7 is a graph showing the change in viscosity of the positive electrode slurry manufactured in Comparative Example 1 at the initial stage and after 1 day.

[0017] Figure 8 is a graph showing the change in viscosity of the positive electrode slurry manufactured in Example 1 at the initial stage and after 1 day.

[0018] Figure 9 is a graph showing the change in ionic conductivity according to the lithium salt content of a composite binder solvent and a reference binder solution.

[0019] Figure 10 is a graph showing the ionic conductivity and electronic conductivity of the anodes of Examples 1 and 2 and Comparative Example 1.

[0020] Figure 11 is a schematic diagram schematically showing the action of lithium salt to suppress binder agglomeration between a hydrofluoric acid binder and a dispersion medium.

[0021] Below, specific implementation examples are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the implementation examples described herein.

[0022] 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.

[0023] Here, “combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 transmission electron microscope images or scanning electron microscope images. 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.

[0028] Here, “or” is not interpreted in an exclusive sense, for example, “A or B” is interpreted to include A, B, A+B, etc.

[0029] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0030] anode

[0031] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, comprising: a positive electrode current collector; and a positive electrode active material layer positioned on the positive electrode current collector; wherein the positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a fluorine-based binder, a lithium salt, and a dispersion medium, wherein the fluorine-based binder is a copolymer of polyvinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene (PVdF-HFP-TFE), and the dispersion medium includes a compound represented by the following chemical formula 1.

[0032] [Chemical Formula 1]

[0033] CH3C(=O)OR 1

[0034] In the above chemical formula 1, R 1 is an alkyl group of C7 to C9.

[0035] The positive electrode active material layer includes a positive electrode active material, a sulfide-based solid electrolyte, a fluorine-based binder, a lithium salt, and a dispersion medium. Among the solid electrolytes included in the positive electrode active material layer, the sulfide-based solid electrolyte, which is mainly selected due to its excellent ionic conductivity, is easily deteriorated by air, moisture, polar solvents, or high temperatures. Therefore, when using a sulfide-based solid electrolyte, care must be taken in selecting the material.

[0036] In addition to the aforementioned sulfide-based solid electrolyte, the cathode active material slurry for manufacturing the cathode active material layer contains various organic and inorganic substances, such as cathode active materials and binders, dispersed via a dispersion medium. Among these, fluorinated binders, which have electrochemical stability, are mainly used as binders. However, these fluorinated binders may cause agglomeration within the solution due to the strong interaction between the polymers themselves. As a result, agglomeration of the fluorinated binder (1) can be easily observed, as shown in the circled portion of A in Fig. 11. In addition, these fluorinated binders may increase the viscosity of the cathode active material slurry, thereby deteriorating the storage stability of the slurry and the quality of the electrode plate.

[0037] Accordingly, in one embodiment, an object is to provide a positive electrode capable of improving quality and productivity by suppressing agglomeration between fluorinated binders. To this end, the positive electrode active material layer includes a lithium salt together with a fluorinated binder. As shown in FIG. 11B, a lithium salt (3) can act as a compatibilizer between a fluorinated binder (1) and a dispersion medium (2), thereby suppressing agglomeration of the binder. In addition, the interaction between the fluorinated binder (1) and the lithium salt (3) due to the steric hindrance effect caused by the lithium salt (3) around the chain of the fluorinated binder (1) is also expected to contribute to suppressing agglomeration of the binder.

[0038] For example, the fluorine-based binder and the lithium salt may be complexed, and this complexation may form a complex of the fluorine-based binder and the lithium salt. The complex of the fluorine-based binder and the lithium salt may be referred to as a lithium ion conductive composite binder. In the positive electrode for an all-solid-state secondary battery, the sulfide-based solid electrolyte is vulnerable to moisture and has limited dispersibility, requiring the addition of an organic binder. In particular, the development of an organic binder that is applicable to a wet process and has high lithium ion conductivity is becoming an important factor in the commercialization of all-solid-state secondary batteries. Accordingly, the complex of the fluorine-based binder and the lithium salt described above can improve the dispersibility of the positive electrode active material and the sulfide-based solid electrolyte, suppress deterioration of the sulfide-based solid electrolyte, and effectively lower the resistance of the positive electrode. In addition, the dispersion medium described below can promote the interaction between the fluorine-based binder and the lithium salt, and has low reactivity with the sulfide-based solid electrolyte, thereby suppressing deterioration of the solid electrolyte. Within this dispersion medium, the fluorine-based binder and lithium salt interact to promote lithium ionization, and the positive electrode containing this has reduced resistance and improved high-rate and life characteristics.

[0039] Dispersant

[0040] The above dispersion medium includes a compound represented by the chemical formula 1 below.

[0041] [Chemical Formula 1]

[0042] CH3C(=O)OR 1

[0043] R 1 is an alkyl group of C7 to C9. That is, R 1 is an alkyl group having 7 to 9 carbon atoms. R 1 The alkyl group may be a chain-like alkyl group or a cyclic alkyl group, and may be a straight-chain or branched alkyl group.

[0044] The compound represented by the above chemical formula 1 can be expressed as a C7 to C9 alkyl acetate, and may be, for example, heptyl acetate, octyl acetate, or nonyl acetate. In the above chemical formula 1, R 1 For example, it can be an alkyl group of C7 to C8 or an alkyl group of C8 to C9.

[0045] The above dispersion medium is a nonpolar or low-polar solvent that has very low reactivity with a sulfide-based solid electrolyte and may not increase cell resistance. Furthermore, the dispersion medium can effectively dissolve a fluorinated binder to achieve an appropriate viscosity, thereby enabling uniform coating on the electrode plate. Furthermore, the dispersion medium can facilitate complexation of the fluorinated binder and lithium salt and promote interaction between the two. Accordingly, lithium ionization within the positive electrode can be promoted, thereby enhancing the lithium ion conductivity of the positive electrode for an all-solid-state secondary battery.

[0046] With respect to 100 wt% of the positive electrode active material layer, the dispersion medium may be included in an amount of 0.1 wt% or less, and the lower limit of the dispersion medium content may not be particularly limited. Alternatively, the dispersion medium may be included in an amount of 0.0001 wt% to 0.1 wt%, for example, 0.0001 wt% to 0.05 wt%, with respect to 100 wt% of the positive electrode active material layer. Alternatively, with respect to 100 wt% of the positive electrode active material layer, the compound represented by the chemical formula 1 may be included in an amount of 0.1 wt% or less, 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%. It can be said that the compound represented by the chemical formula 1 used as a kind of dispersion medium in the positive electrode composition during the manufacture of the positive electrode remains in the final positive electrode active material layer in such a small amount.

[0047] Fluorine-based binder

[0048] The above fluorinated binder is a polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene (PVdF-HFP-TFE) copolymer. The above-mentioned fluorinated binder is suitable for complexing with lithium salts, improves the lithium ion conductivity of a positive electrode for an all-solid-state secondary battery, enhances the dispersibility of a sulfide-based solid electrolyte, and effectively suppresses deterioration due to moisture.

[0049] According to one embodiment, a fluorinated binder may include 30 mol% to 45 mol% of vinylidene fluoride units, 30 mol% to 45 mol% of hexafluoropropylene units, and 10 mol% to 45 mol% of tetrafluoroethylene units, for example, 35 mol% to 40 mol% of vinylidene fluoride units, 35 mol% to 40 mol% of hexafluoropropylene units, and 20 mol% to 30 mol% of tetrafluoroethylene units. In this range, the effect of securing excellent adhesive strength and the effect of suppressing viscosity changes of the binder in the short or long term can be harmonized with each other.

[0050] The above fluorine-based binder may be included in an amount of 0.1 wt% to 5 wt% based on 100 wt% of the positive electrode active material layer, for example, 0.1 wt% to 3 wt%, or 0.5 wt% to 2 wt%. Within this range, excellent adhesive strength can be effectively secured.

[0051] lithium salt

[0052] The lithium salt may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiCsF6, LiCl, LiF, LiBr, LiI, LiCF3SO3, LiClO4, LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiB(C2O4)2, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.

[0053] For example, the lithium salt may be an imide-based lithium salt. Specifically, the imide-based lithium salt may be lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof. Such imide-based lithium salts are suitable for complexing with fluorine-based binders and advantageously act to increase lithium ion conductivity and reduce resistance of a positive electrode for an all-solid-state secondary battery. In addition, the lithium salt acts as a compatibilizer between the polymer and the dispersion medium, thereby preventing binder agglomeration not only during short-term but also long-term storage of the binder solution.

[0054] The lithium salt may be included in an amount of 10 to 60 parts by weight, for example, 30 to 50 parts by weight, based on 100 parts by weight of the fluorine-based binder. When the lithium salt is included in the above range, effective complexation with the fluorine-based binder may occur, thereby increasing the lithium ion conductivity of the positive electrode for an all-solid-state secondary battery while lowering the resistance, and improving the high-rate characteristics and life characteristics of the all-solid-state battery.

[0055] The lithium salt may be included in an amount of 0.01 wt% to 3 wt% based on 100 wt% of the positive electrode active material layer, for example, 0.05 wt% to 2 wt%, or 0.1 wt% to 1 wt%. Within the above range, excellent ionic conductivity and battery performance can be effectively secured.

[0056] positive electrode active material

[0057] The cathode active material can be applied without limitation as long as it is one commonly used in all-solid-state secondary batteries. For example, the cathode active material may be a compound capable of reversible lithium intercalation and deintercalation. Specifically, the cathode active material may be at least one compound oxide of lithium and a metal selected from the group consisting of cobalt, manganese, nickel, and combinations thereof.

[0058] As a positive electrode active material, a compound represented by one of the following chemical formulas can be used, for example, 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); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f)Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0059] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0060] 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).

[0061] 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.

[0062] [Chemical Formula 11]

[0063] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0064] 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 2are 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.

[0065] In the above chemical formula 11, 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.

[0066] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0067] [Chemical Formula 12]

[0068] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0069] 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.

[0070] [Chemical Formula 13]

[0071] Li a3 Fex3 M 4 y3 PO 4-b3 X b3

[0072] 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.

[0073] [Chemical Formula 14]

[0074] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0075] In the above chemical formula 14, 0.9≤a2≤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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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%. Within this range, it may be advantageous to ensure smooth ionic conductivity and secure battery performance.

[0080] Sulfide-based solid electrolyte

[0081] In order to secure excellent ionic conductivity, the positive electrode active material layer includes a sulfide-based solid electrolyte as a solid electrolyte. The sulfide-based solid electrolyte includes, for example, Li2S-P2S5, Li2S-P2S5-LiX (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.

[0082] 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.

[0083] Methods for mixing sulfur-containing raw materials for manufacturing sulfide-based solid electrolytes include mechanical milling or solution milling. Mechanical milling involves placing starting materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution milling method, the starting 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. The heat treatment can be performed at a temperature ranging from 400°C to 600°C, for example, from 450°C to 500°C, or from 460°C to 490°C, for 5 to 30 hours, 10 to 24 hours, or 15 to 20 hours. Heat treatment under the above conditions can maximize ionic conductivity. For example, a sulfide-based solid electrolyte can be manufactured by mixing sulfur-containing raw materials and heat-treating them twice or more, in which case a sulfide-based solid electrolyte with high ionic conductivity and strength can be manufactured.

[0084] 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.

[0085] For example, the sulfide-based solid electrolyte may be in the form of particles and may include argyrodite-type sulfides. These argyrodite-type sulfide-based solid electrolyte particles have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It possesses high ionic conductivity approaching the S / cm range. Furthermore, it can form a close bond between the positive electrode active material and the solid electrolyte without causing a decrease in ionic conductivity, and can form a close interface between the electrode and the solid electrolyte layer. An all-solid-state secondary battery including this can exhibit improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0086] The above argyrodite-type sulfide-based solid electrolyte may include, for example, a compound represented by the chemical formula 21 below.

[0087] [Chemical Formula 21]

[0088] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0089] In the above chemical formula 21, 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.

[0090] For example, in chemical formula 21, a halogen element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 21에 M 1 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 21에서 M 3 can be understood as an element substituted in the P position, and 0 <e<1일 수 있다. 화학식 21에서 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.

[0091] For example, in chemical formula 21, a+b+c+h=7, d+e=1, and f+g+h=6.

[0092] 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.

[0093] 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.

[0094] 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 ㎛. When such a sulfide-based solid electrolyte is used, it can effectively penetrate between positive electrode active materials, and the contactability with the positive electrode active material and the connectivity between the solid electrolyte particles can be excellent. At this time, the average particle diameter of the sulfide-based solid electrolyte particles may be measured from an electron microscope image, and for example, the particle size distribution may be obtained by measuring the size (diameter or length of the major axis) of about 20 particles in a scanning electron microscope image, and D50 may be calculated from this.

[0095] With respect to the total weight of the positive electrode active material layer, the sulfide-based solid electrolyte may be included in an amount of 0.1 wt% to 35 wt%, for example, 0.5 wt% to 35 wt%, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%.

[0096] In addition, in the positive electrode active material layer, the positive electrode active material may be included in an amount of 65 wt% to 99 wt% and the sulfide-based solid electrolyte in an amount of 1 wt% to 35 wt%, based on the total weight of the positive electrode active material and the sulfide-based solid electrolyte, for example, the positive electrode active material may be included in an amount of 80 wt% to 90 wt% and the sulfide-based solid electrolyte in an amount of 10 wt% to 20 wt%. 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.

[0097] Other solid electrolytes

[0098] The above-mentioned positive electrode active material layer may further include, as a solid electrolyte, other solid electrolytes in addition to the aforementioned sulfide-based solid electrolyte. For example, the other solid electrolyte may further include an oxide-based solid electrolyte, a halide-based solid electrolyte, a polymer-based solid electrolyte, or a combination thereof. The types of the other solid electrolytes described above are described in detail below.

[0099] The above oxide-based solid electrolyte is, 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 y O3(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 Tiy (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.

[0100] The above 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.

[0101] The halide-based solid electrolyte may contain 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. The halide-based solid electrolyte may contain, for example, Li aM1X6 (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.

[0102] The above polymer-based solid electrolyte may be a composite of a lithium salt and a polymer resin. For example, the above polymer-based solid electrolyte may be formed by adding a polymer resin to a lithium salt.

[0103] The above other solid electrolyte is in the form of particles and may have an average particle diameter (D50) of 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛.

[0104] Challenge

[0105] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. For example, the conductive material may include a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; a metal-based material containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; a conductive polymer such as a polyphenylene derivative; or a conductive material including a mixture thereof.

[0106] 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.

[0107] Aluminum foil may be used as the positive electrode collector, but is not limited thereto.

[0108] All-solid-state secondary battery

[0109] In one embodiment, an all-solid-state secondary battery is provided, comprising the above-described positive electrode; a negative electrode; and a solid electrolyte layer positioned between the positive electrode and the negative electrode.

[0110] 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.

[0111] cathode

[0112] An anode for an all-solid-state secondary battery includes a cathode current collector; and a cathode active material layer positioned on the cathode current collector. The cathode active material layer includes a cathode active material and may further include a binder and / or a conductive material.

[0113] 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.

[0114] 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.

[0115] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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 a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0125] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0126] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0127] When using an aqueous binder as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity 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.

[0128] The above dry binder is a polymeric material capable of being fiberized, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof. The amount of such thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0129] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0130] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0131] 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.

[0132] 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 negative electrode current collector (401) and a negative electrode coating layer (405) positioned on the negative electrode 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 negative electrode 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 negative electrode current collector (401), a lithium metal layer (404) positioned on the negative electrode 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.

[0133] 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, a carbon material, or a combination thereof.

[0134] 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.

[0135] 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. For example, the carbon material may refer to amorphous carbon.

[0136] When the cathode 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 cathode 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.

[0137] The 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 can 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.

[0138] The cathode coating layer (405) may further include a binder, which may be, for example, a conductive binder. In addition, the cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0139] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 μm, or 500 nm to 10 μm, or 1 μm to 5 μm.

[0140] The precipitation-type negative electrode (400') may further include, for example, a thin film on the surface of the negative electrode current collector, that is, between the negative electrode 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 planarize the precipitation 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] solid electrolyte layer

[0145] The solid electrolyte layer (300) may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, etc. The details of the sulfide-based solid electrolyte, the oxide-based solid electrolyte, and the halide-based solid electrolyte are as described above, so they are omitted.

[0146] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300) may be larger than the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200). In this case, the energy density of the all-solid-state secondary battery can be maximized while increasing the mobility of lithium ions, thereby improving the overall performance. For example, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be 0.1 ㎛ to 1.9 ㎛, or 0.1 ㎛ to 1.0 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300) may be 2.0 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When this particle size range is satisfied, the energy density of the all-solid-state secondary battery can be maximized while lithium ion transport is facilitated, resistance is suppressed, and the overall performance of the all-solid-state secondary battery can be improved. Here, the average particle size (D50) of the solid electrolyte can be measured using a particle size analyzer using laser diffraction.

[0147] The above solid electrolyte layer may further include a binder in addition to the solid electrolyte. At this time, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, but is not limited thereto, and any binder used in the relevant technical field may be used. The acrylate polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0148] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted.

[0149] The thickness of the solid electrolyte layer may be, for example, 100 μm to 3000 μm, for example, 100 μm to 2000 μm, 100 μm to 1000 μm, 100 μm to 800 μm, 100 μm to 400 μm, or 100 μm to 300 μm.

[0150] The solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, trizolium, 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.

[0156] 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.

[0157] In the solid electrolyte layer, the weight ratio of the solid electrolyte to 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.

[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 negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative 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. Preparation of binder solution

[0163] A binder solution is prepared by mixing 0.8 g of PVdF (40 mol%)-HFP (40 mol%)-TFE (20 mol%) and 0.24 g of LiTFSI in octyl acetate. Here, the weight ratio of PVdF-HFP-TFE and LiTFSI is 100:30.

[0164] 2. Manufacturing of the anode

[0165] LiNi coated with Li2O-ZrO2 0.9 Co 0.05 Mn 0.05 A cathode slurry is prepared by mixing an O2 cathode active material, an argyrodite-type solid electrolyte Li6PS5Cl (D50=1.0㎛), a prepared binder solution, and a carbon nanotube conductive material. At this time, the cathode slurry is mixed so that the cathode active material is 85 wt%, the solid electrolyte is 13.5 wt%, the PVdF-HFP-TFE is 1.0 wt%, the LiTFSI is 0.3 wt%, and the conductive material is 0.2 wt%, excluding the content of the dispersion medium. The prepared cathode slurry is coated on a cathode current collector using a bar coater, and dried in a convection oven at 80°C for 10 minutes, thereby preparing a cathode in which a cathode active material layer is formed on the cathode current collector.

[0166] 3. Manufacturing of solid electrolyte layer

[0167] A solid electrolyte layer slurry is prepared by adding an argyrodite-type solid electrolyte Li6PS5Cl (D50=3㎛) to a binder solution in which an acrylic binder (SX-A334, Zeon) is dissolved in an isobutylyl isobutylate (IBIB) solvent and stirring the solution. The solid electrolyte layer slurry contains 98.5 wt% of the solid electrolyte and 1.5 wt% of the binder. The solid electrolyte layer slurry is applied onto a release PET film using a bar coater and dried at room temperature to prepare a solid electrolyte layer.

[0168] 4. Manufacturing of the cathode

[0169] An Ag / C composite is 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 is added to 2 g of an NMP solution containing 7 wt% polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer slurry. This is applied to a nickel foil current collector using a bar coater and vacuum-dried to prepare a deposition-type negative electrode in which a negative electrode coating layer is formed on the negative electrode current collector.

[0170] 5. Manufacturing of all-solid-state secondary batteries

[0171] The prepared positive electrode, negative electrode, and solid electrolyte layer are cut, a solid electrolyte layer is laminated on the positive electrode, and then the negative electrode is laminated on top of that. This is sealed in a pouch shape and subjected to a warm isostatic press (WIP) at 85°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0172] Example 2

[0173] A positive electrode and an all-solid-state secondary battery are manufactured in substantially the same manner as in Example 1, except that a binder solution having a weight ratio of PVdF-HFP-TFE and LiTFSI of 100:50 is manufactured by mixing 1.0 g of PVdF-HFP-TFE and 0.5 g of LiTFSI with 9.2 g of octyl acetate.

[0174] Comparative Example 1

[0175] A positive electrode and an all-solid-state secondary battery are manufactured in substantially the same manner as in Example 1, except that the binder solution is manufactured without adding LiTFSI.

[0176] Evaluation Example 1: Initial Charge-Discharge Performance Evaluation

[0177] In order to evaluate the initial charge-discharge performance, a voltage graph according to specific capacity is shown in Fig. 3 for the all-solid-state secondary batteries manufactured in Examples 1 and 2 and Comparative Example 1.

[0178] For each battery, an initial charge / discharge was performed by charging to an upper limit voltage of 4.25 V at a constant current of 0.1 C at 45°C and then discharging to a final voltage of 2.5 V at 0.1 C (first cycle; indicated by 0.1 C in Fig. 3). A second cycle was then performed under the same voltage range with 0.1 C charge and 0.3 C discharge conditions (second cycle; indicated by 0.3 C in Fig. 3). A third cycle was then performed under the same voltage range with 0.1 C charge and 1 C discharge conditions (third cycle; indicated by 1 C in Fig. 3).

[0179] Referring to Figure 3, the battery resistance of Comparative Example 1 was found to be higher in all of the first to third cycles. It is understood that the cell performance is maximized when the lithium salt content is 30 to 50 parts by weight relative to 100 parts by weight of the fluorine-based binder.

[0180] Evaluation Example 2: Life Characteristics Evaluation

[0181] For the all-solid-state secondary batteries manufactured in Examples 1 and 2 and Comparative Example 1, initial charge and discharge were performed as in Evaluation Example 1, and then charging at 0.33 C and discharging at 0.33 C in a voltage range of 2.5 V to 4.25 V at 45°C were repeated 100 times or more to evaluate the life characteristics, and the specific capacity (mAh / g) according to the number of cycles was measured and shown in Table 1 and Fig. 4 below.

[0182] 20-time capacity (mAh / g)50-time capacity (mAh / g)100-time capacity (mAh / g)Example 1181178170Example 2184179172Comparative example 1175173167

[0183] Referring to Table 1 and Figure 4, the life characteristics of Examples 1 and 2 were relatively better than those of Comparative Example 1.

[0184] Evaluation Example 3: Evaluation of the storage characteristics of the binder solution

[0185] In order to evaluate the temporal storage characteristics of the binder solution, the viscosity change graphs for the binder solution prepared in Comparative Example 1 at the initial stage, after 1 day of high-temperature stirring, and after 1 month of storage are shown in Fig. 5. In addition, the viscosity change graphs for the binder solution prepared in Example 1 at the initial stage and after 1 month of storage are shown in Fig. 6. At this time, the viscosity was measured using a rheometer viscometer at a temperature of 25°C, specifying a shear rate range of 0.01 to 1000, increasing the shear rate from 0.01 to 1000, and then decreasing it from 1000 to 0.01 (forward and backward direction).

[0186] Referring to FIGS. 5 and 6, it can be seen that although the short-term differences in the storage characteristics of the binder solution of Example 1 compared to Comparative Example 1 are not significant, there is a significant difference in the viscosity change in the long term. That is, in Example 1, the viscosity change of the binder solution is minimal even after a long-term storage of one month, whereas in Comparative Example 1, the viscosity change of the binder solution after a long-term storage of one month is large compared to the initial state. Therefore, it can be expected that when the binder solution prepared in Comparative Example 1 is used, there may be a problem with the stability of the slurry.

[0187] Evaluation Example 4: Evaluation of the standing characteristics of anode slurry

[0188] In order to evaluate the standing characteristics of the positive electrode slurry, graphs showing the change in viscosity over 1 day (1 day) compared to the initial value (0 day) for each positive electrode slurry manufactured in Comparative Example 1 and Example 1 are shown in FIGS. 7 and 8, respectively. At this time, the viscosity was measured using the same method as in Evaluation Example 3.

[0189] Referring to FIGS. 7 and 8, it can be confirmed that the viscosity change after 1 day compared to the initial state in Example 1 is smaller than in Comparative Example 1. Accordingly, it can be seen that in the case of Example 1 using a lithium salt, the viscosity increase tendency of the positive electrode slurry is suppressed compared to Comparative Example 1. Therefore, it can be seen that in Comparative Example 1, the viscosity tendency of the positive electrode slurry was large, so there was a problem with the stability of the slurry, and the quality and performance of the electrode plate could easily deteriorate during the manufacture of the positive electrode.

[0190] Evaluation Example 5: Ionic Conductivity of Binder Solution

[0191] The change in cell performance depending on the salt concentration suggests that the binder plays a key role in the activation of the lithium salt. This suggests that the PVdF-HFP-TFE binder interacts with the LiTFSI salt, aiding its ionization. To support this, the change in ionic conductivity of the LiTFSI solution with and without the binder was analyzed as follows.

[0192] A composite binder solution is prepared by mixing PVdF-HFP-TFE, LiTFSI, and octyl acetate, and the content of octyl acetate is changed to 1150 parts by weight and the content of LiTFSI is changed to 10 parts by weight, 30 parts by weight, and 50 parts by weight, based on 100 parts by weight of PVdF-HFP-TFE (corresponding to 'binder + LiTFSI' in Fig. 9).

[0193] In addition, a reference binder solution was prepared by adding LiTFSI to octyl acetate in the same amount but not adding PVdF-HFP-TFE (corresponding to 'LiTFSI only' in Fig. 9). The ionic conductivity (μS / cm) of the prepared solutions was measured, and the change in ionic conductivity according to the LiTFSI content is shown in Fig. 9. Here, the ionic conductivity was measured using a portable ion meter from Mettler Toledo.

[0194] Referring to the above experimental results, it was confirmed that the ionic conductivity of the composite binder solution mixed with PVdF-HFP-TFE and LiTFSI increased more than that of the reference binder solution without PVdF-HFP-TFE binder at various LiTFSI contents, and it was confirmed that the higher the LiTFSI content, the higher the ionic conductivity.

[0195] Evaluation Example 6: Evaluation of ionic and electronic conductivity of the electrode plate

[0196] A symmetric ion blocking cell was manufactured using the positive electrodes manufactured in Examples 1 and 2 and Comparative Example 1, and electrochemical impedance spectroscopy (EIS) was performed on the positive electrode plates. At this time, EIS had an amplitude of about 10 mV and a frequency of 0.1 Hz to 10 6 Hz, air atmosphere, 25℃. The positive electrode plate is a mixed conductor capable of simultaneous transport of electrons and ions, and an equivalent circuit corresponding to it can be designed. The Nyquist plot was obtained by impedance analysis, and the ionic conductivity and electronic conductivity of the positive electrode plate were separated and extracted therefrom, and the results are shown in Fig. 10. In Fig. 10, the left vertical axis represents the electronic conductivity, and the right vertical axis represents the ionic conductivity. Referring to Fig. 10, it can be confirmed that the positive electrode plates of Examples 1 and 2 manufactured using the positive electrode slurry mixed with PVdF-HFP-TFE and LiTFSI exhibit excellent ionic conductivity and electronic conductivity.

[0197] 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.

[0198] [Explanation of symbols]

[0199] 1: Fluorine-based binder 2: Dispersion medium

[0200] 3: Lithium salt

[0201] 100: All-solid-state battery 200: Cathode

[0202] 201: Cathode current collector 203: Cathode active material layer

[0203] 300: solid electrolyte layer 400: cathode

[0204] 401: Negative current collector 403: Negative active material layer

[0205] 400': Precipitation type cathode 404: Lithium metal layer

[0206] 405: Cathode coating layer 500: Elastic layer

Claims

1. A positive electrode current collector; and a positive electrode active material layer positioned on the positive electrode current collector; The above cathode active material layer includes a cathode active material, a sulfide-based solid electrolyte, a fluorine-based binder, a lithium salt, and a dispersion medium. The above fluorine-based binder is a copolymer of polyvinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, The above dispersion medium is a positive electrode for an all-solid-state secondary battery comprising a compound represented by the following chemical formula 1: [Chemical Formula 1] CH 3 C(=O)O-R 1 In the above chemical formula 1, R 1 is an alkyl group of C7 to C9.

2. In paragraph 1, A positive electrode for an all-solid-state secondary battery, wherein the compound represented by the chemical formula 1 is contained in an amount of 0.1 wt% or less with respect to 100 wt% of the positive electrode active material layer.

3. In paragraph 1, An all-solid-state secondary battery positive electrode, wherein the lithium salt is contained in an amount of 10 to 60 parts by weight based on 100 parts by weight of the fluorine-based binder in the positive electrode active material layer.

4. In paragraph 1, An all-solid-state secondary battery positive electrode, wherein the lithium salt is contained in an amount of 30 to 50 parts by weight per 100 parts by weight of the fluorine-based binder in the positive electrode active material layer.

5. In paragraph 1, The above fluorine-based binder A positive electrode for an all-solid-state secondary battery comprising 30 to 45 mol% of a vinylidene fluoride unit, 30 to 45 mol% of a hexafluoropropylene unit, and 10 to 45 mol% of a tetrafluoroethylene unit.

6. In paragraph 1, The above lithium salt is LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiCsF 6 , LiCl, LiF, LiBr, LiI, LiCF 3 SO 3 , LiClO 4 , LiSCN, LiN(CN) 2 , Li(CF 3 SO 2 ) 3 C, LiC 4 F 9 SO 3 , LiN(SO 2 CF 2 CF 3 ) 2 , LiB(C 2 O 4 ) 2 , LiBF 3 (C 2 F 5 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.

7. In paragraph 1, The above lithium salt is an imide-based lithium salt, and is a positive electrode for an all-solid-state secondary battery.

8. In paragraph 7, The above lithium salt is a cathode for an all-solid-state secondary battery comprising lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a combination thereof.

9. In paragraph 1, An all-solid-state secondary battery cathode comprising the above-mentioned fluorine-based binder and the above-mentioned lithium salt in a composite form.

10. In paragraph 1, An all-solid-state secondary battery positive electrode, comprising 65 to 99 wt% of the positive electrode active material and 1 to 35 wt% of the sulfide-based solid electrolyte, based on the total weight of the positive electrode active material and the sulfide-based solid electrolyte.

11. In paragraph 1, The above cathode active material is a cathode for an all-solid-state secondary battery including lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium iron phosphate oxide, or a combination thereof.

12. In paragraph 1, The above sulfide-based solid electrolyte is a positive electrode for an all-solid-state secondary battery containing an argyrodite-type sulfide.

13. In paragraph 1, The average particle diameter (D50) of the above positive electrode active material is 3 ㎛ to 25 ㎛, An all-solid-state secondary battery cathode having an average particle size (D50) of the above sulfide-based solid electrolyte of 0.1 ㎛ to 1.9 ㎛.

14. In paragraph 1, The above positive electrode active material layer is, with respect to 100 wt% of the positive electrode active material layer, 55 wt% to 99 wt% of cathode active material, 0.1 wt% to 35 wt% sulfide-based solid electrolyte, 0.1 wt% to 5 wt% fluorinated binder, 0.01 wt% to 3 wt% lithium salt, 0.0001 wt% to 0.1 wt% of a dispersant and A cathode for an all-solid-state secondary battery comprising 0 to 3 wt% of a conductive material.

15. An anode according to any one of paragraphs 1 to 14; cathode; and An all-solid-state secondary battery comprising a solid electrolyte layer positioned between the positive electrode and the negative electrode.

16. In paragraph 15, The above negative electrode comprises a negative electrode current collector; and a negative electrode coating layer positioned on the negative electrode 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 negative electrode current collector and the negative electrode coating layer.

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